HUMAN VACCINES & IMMUNOTHERAPEUTICS 2016, VOL. 12, NO. 10, 2616–2627 http://dx.doi.org/10.1080/21645515.2016.1187343
PRODUCT REVIEW
FluzoneÒ intra-dermal (IntanzaÒ /IstivacÒ Intra-dermal): An updated overview Nicola Luigi Bragazzia, Andrea Orsia,b, Filippo Ansaldia,b, Roberto Gasparinia, and Giancarlo Icardia,b a
Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy; bHygiene Unit, IRCCS AOU San Martino - IST of Genoa, Genoa, Italy
ABSTRACT
ARTICLE HISTORY
Influenza is a highly contagious respiratory acute viral disease which imposes a very heavy burden both in terms of epidemiology and costs, in the developed countries as well as in the developing ones. It represents a serious public health concern and vaccination constitutes an important tool to reduce or at least mitigate its burden. Despite the existence of a broad armamentarium against influenza and despite all the efforts and recommendations of international organisms to broaden immunization, influenza vaccination coverage is still far from being optimal. This, taken together with logistic and technical difficulties that can result into vaccine shortage, makes intra-dermal (ID) vaccines, such as FluzoneÒ ID and IntanzaÒ , particularly attractive. ID vaccines are comparable and, in some cases, superior to intra-muscular/ sub-cutaneous vaccines in terms of immunogenicity, safety, reactogenicity, tolerability and crossprotection profiles, as well as in terms of patient preference, acceptance and vaccine selection. Further advances, such as FluzoneÒ ID with alternative B strains and Quadrivalent FluzoneÒ ID or the possibility of self-administering the vaccines, make influenza ID vaccines even more valuable.
Received 19 February 2016 Revised 20 April 2016 Accepted 4 May 2016
Introduction Influenza Influenza is a highly contagious respiratory acute viral disease characterized by a worldwide distribution, a short incubation period (1–3 days, generally 2 days), usually mild respiratory and systemic symptoms, such as high fever, cough, sore throat, headache, chills, anorexia and fatigue.1,2 It can be asymptomatic in 30–50% of subjects.2,3 On the other hand, it may result into severe complications, such as bacterial pneumonia and exacerbation of underlying chronic conditions (including heart or respiratory failure, chronic obstructive pulmonary diseases or COPDs, among others), hospitalization and deaths, especially in frail and high-risk subjects.2 The burden of seasonal influenza as well as of influenza pandemics is very heavy, both in terms of epidemiology and costs, in the developed countries4 as well as in the developing ones.5 Indeed, the World Health Organization (WHO) estimates that annual epidemics affect up to 15% of the total population worldwide, causing up to 4–5 million severe cases and up to 500,000 deaths.6 For these reasons, influenza represents a serious public health concern and vaccination constitutes an important tool to reduce and mitigate the tremendous socioeconomic burden generated by influenza. Influenza is caused by a single-stranded, negative-sense RNA virus, Myxovirus influenzae, which belongs to the Orthomyxoviridae family together with Thogotovirus and Isavirus, and includes 3 serotypes or genera, A, B, and C. The genus A, first isolated in 1933,7 is the most clinically relevant and has the capacity to induce minor or major changes in its structure
KEYWORDS
cutaneous vaccination; FluzoneÒ ; influenza; IntanzaÒ ; intradermal vaccine; microneedle device; skin immunization
(antigenic drifts and antigenic shifts, respectively). In case of antigenic drifts, the virus causes interpandemic influenza (known also as annual epidemics or seasonal influenza). In case of antigenic shifts, it causes pandemic influenza. Pandemic influenza is caused by influenza virus genus A, while seasonal influenza by influenza genus A and genus B.2 Influenza virus has a quite complex replication cycle, achieved through various stages (Fig. 1).1 First, the virus attaches to the (a-2,3)- or (a-2,6)-linked sialic acid receptors present on the free surface of the cells of the upper respiratory tract or erythrocytes. During this step (termed as virus adsorption), the role of hemagglutinin (HA), a cylinder-shaped, homotrimeric integral type 1 membrane glycoprotein found on the surface of influenza viruses, is crucial. The virus can then enter the cells (internalization) by exploiting different routes (clathrin-mediated endocytosis or CME, caveolae-dependent endocytosis or CDE, clathrin-caveolaeindependent endocytosis, or macropinocytosis). CME is the most usual pathway; the virus is internalized into an endosomal compartment, from which it must emerge in order to release its nucleic acid into the cytosol (endosomal trafficking via endosomes/caveosomes/macropinosomes/lysosomes to the perinuclear compartment). During the phase of fusion of the viral envelope with the endosome membrane, after the pH has been reduced (pH-dependent fusion of viral and endosomal/organellar membranes and uncoating), HA plays again a major role. The ribonucleoprotein must then reach the nucleus (nuclear importation) in order to begin the process of translation of its genes and to transcribe and replicate its nucleic acid (transcription and replication). Subsequently, the RNA segments, surrounded by the nucleoproteins, must migrate to the cell membrane (nuclear exportation) in order
CONTACT Giancarlo Icardi [email protected] Department of Health Sciences, University of Genoa, Via A. Pastore 1, 16132 Genoa, Italy. Color versions of one or more of the figures in this article can be found online at www.tandfonline.com/khvi. © 2016 Taylor & Francis
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Figure 1. The steps of the replication cycle of the influenza virus are the following: 1) virus adsorption; 2) internalization into cellular regions by means of clathrin-mediated endocytosis (CME), caveolae-dependent endocytosis (CDE), clathrin-caveolae-independent endocytosis, and macropinocytosis; 3) endosomal trafficking; 4) pHdependent fusion of viral and endosomal / organellar membranes; 5) uncoating; 6) nuclear importation; 7) transcription and replication; 8) nuclear exportation; 9) protein synthesis; 10) post-translational processing and trafficking; 11) viral progeny assembly and packaging; 12) budding; and 13) release (modified from references1 and 4 ).
to enable further molecular processing (namely, protein synthesis, post-translational processing and trafficking, and viral progeny assembly and packaging). Finally, the virus must be freed to invade other cells of the respiratory tract (budding and release). All this is achieved through a complex, finely tuned, highly dynamic, and synchronized action of a vast array of molecular complexes that perform multiple enzymatic and catalytic reactions, whose details are currently known only in part.1
Overview of the market The pharmacological armamentarium against influenza includes different drugs and vaccines, which has been recently reviewed by Gasparini and collaborators.8 Current available drugs include NA inhibitors (NAIs), such as oseltamivir, zanamivir, and peramivir, and adamantane-based M2 protein blockers (amantadine and rimantadine). However, because of the biology of influenza virus and its frequent mutations, these drugs are plagued by the issue of resistance.9,10 A variety of vaccines exists against influenza.8 They can be basically divided into 2 categories: pandemics and seasonal vaccines. Further, they can divided into inactivated influenza vaccines and live, attenuated influenza vaccines (called LAIVs). The first category includes: whole virus vaccine, subunit vaccine made up of purified HA and NA proteins, and split-virion vaccine. Licensed prepandemic/pandemic vaccines (reviewed in 11,12) are shown in Table 1. Other investigational vaccines against
H7N9 or universal pandemic vaccines are still under clinical experimentation.13 Seasonal vaccines can be divided into inactivated splitvirion, inactivated subunit and LAIV vaccines (revised in 14-23). Recently, also seasonal adjuvanted vaccines such as those adjuvanted by MF59 or virosomes have become available (reviewed in24). Inactivated vaccines can be administered via the IM route in subjects aged 6 mo and older,25 while LAIVs may be given intra-nasally to healthy, non-pregnant people aged 2–49 y. They may safely be administered at the same time as other vaccines.26 For further details, the reader is referred to Table 1. Generally speaking, the overall efficacy of influenza vaccines is 59% against laboratory-confirmed cases of influenza according to the recent meta-analysis by Osterholm and collaborators.27 According to another meta-analysis it varies from 17% against influenza like illness (ILI) to 73% against confirmed influenza.28 There is therefore the need to develop more effective vaccines.
Influenza vaccination coverage Despite the fact that annual vaccination represents an important strategy for curbing influenza-related complications, the vaccination coverage is still far from being optimal. For example, in the USA, according to the National Immunization Survey-Flu and the National Internet Flu Survey, only 39.0% of all individuals aged 6 mo, that is to say 2 subjects out of 5, were vaccinated against influenza, leaving therefore most population unprotected (CDC, 2015). Also among health-care personnel,
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Table 1. Overview of the market with the main available influenza vaccines. Commercial name AdimFlu-SÒ AflunovÒ ArepanrixÒ^ CantgripÒ CelturaÒ CelvapanÒ DaronrixÒ^ FocetriaÒ^ FocliviaÒ Green Flu-SÒ HumenzaÒ^ PandemrixÒ / D-Pan H1N1Ò^ PanenzaÒ PanvaxÒ / PanvaxÒ Junior PrepandrixÒ / D-Pan H5N1Ò PumarixÒ^ Q-Pan H5N1Ò VepacelÒ AddigripÒ / AdiugripÒ Adjuvanted InflupozziÒ AlorbatÒ AnFluÒ AgrifluÒ AgrippalÒ BatrevacÒ BegrivacÒ Biaflu Ò / Biaflu zonaleÒ CAIV-TÒ ChirofluÒ DotaricinÒ ElvarixÒ EvagripÒ FluadÒ / Fluad pediatric / Chiromas / Gripguard FluarixÒ Fluarix TetraÒ / Influsplit Tetra / a-RIX-Tetra FlublokÒ x FlucelvaxÒ / OptafluÒ FluINsure FluLavalÒ FlumistÒ / FluenzÒ Flumist quadrivalentÒ / Fluenz TetraÒ FluShieldÒ FluVaccinolÒ Fluval ABÒ FluvaxÒ / AfluriaÒ / EnziraÒ / NilgripÒ / X-FluTM , Influenza Vaccine Ph. Eur. FluviralÒ FluvirinÒ FocusvaxÒ GripaxÒ
Marketing Authorisation Holder
Characteristics
Pandemic/prepandemic vaccines Adimmune Corporation, Taichung, Taiwan Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics S.r.l. Siena, Italy) GlaxoSmithKline, Rixensart, Belgium
trivalent inactivated split-virion H1N1 pandemic vaccine monovalent inactivated surfacen antigen MF59-adjuvanted H5N1 prepandemic vaccine monovalent inactivated split-virion AS03-adjuvanted H1N1 vaccine INCDMI CANTACUZINO – Romania monovalent inactivated H1N1 vaccine Seqirus (bioCSL, formerly Novartis) monovalent inactivated MF59-adjuvanted H1N1 vaccine Baxter International, Vienna, Austria monovalent inactivated whole virus H1N1 vaccine GlaxSmithKline Biologicals, Rixensart, Belgium monovalent whole virus inactivated H5N1 mock-up vaccine Seqirus (bioCSL, formerly Novartis) monovalent inactivated MF59-adjuvanted H1N1 vaccine Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics S.r.l., monovalent inactivated surface antigen MF59-adjuvanted H5N1 Siena, Italy) mock-up vaccine Green Cross Corporation, Korea monovalent inactivated split-virion H1N1 pandemic vaccine Sanofi Pasteur, Lyon, France monovalent inactivated split-virion AF03-adjuvanted H1N1 pandemic vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H1N1 pandemic vaccine Sanofi Pasteur, Lyon, France monovalent inactivated split-virion H1N1 pandemic vaccine CSL Biotherapies, Parkville, Australia monovalent inactivated split-virion H1N1 vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H5N1 prepandemic vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H5N1 pandemic vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H5N1 vaccine Baxter International, Vienna, Austria monovalent inactivated whole virus H5N1 vaccine Seasonal vaccines Sanofi Pasteur (bioCSL, formerly Novartis Vaccines and Diagnostics S.r.l., Siena, Italy) Seqirus (bioCSL, formerly Novartis) Asta Pharma, Ho Chi Minh City, Vietnam Sinovac Kexing Biological Product Co., Ltd Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics Limited) Seqirus (bioCSL, formerly Novartis) Abbott srl Chiron, France KEDRION SpA, Italy (formerly Farmabiagini, Italy) Medimmune LLC, Maryland, USA / AstraZeneca (formerly Aviron, Mountain View, CA, USA) Seqirus (bioCSL, formerly Novartis) Alentia Biotech S.L., Granada, Spain VEB Sachsesches Serumwerk Dresden Seqirus (bioCSL, formerly Novartis) Seqirus (bioCSL, formerly Novartis, formerly Chiron Vaccines, Siena, Italy) GlaxoSmithKline Biologicals, Rixensart, Belgium GlaxoSmithKline Biologicals, Rixensart, Belgium Protein Sciences Corporation, Meriden, CT and Pearl River, NY, USA Seqirus (bioCSL, formerly Novartis) ID Biomedical Canada (formerly Intellivax International) GlaxoSmithKline Biologicals, Rixensart, Belgium Medimmune LLC, Maryland, USA / AstraZeneca (formerly Aviron) Medimmune LLC, Maryland, USA / AstraZeneca (formerly Aviron, Mountain View, CA, USA) Wyeth Lederle Vaccines, USA BGP GmbH, Vienna, Austria / STADA Medical GmbH, Germany Omninvest Vaccine Manufacturing, Researching and Trading Ltd., Hungary CSL Biotherapies, Parkville, Australia / bioCSL GmbH, Marburg, Germany / Pfizer Vaccines, UK / Instituto Biologico Argentino SAIC, Argentina GlaxoSmithKline Biologicals, Rixensart, Belgium Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics Limited) Crucell, Leiden, the Netherlands (formerly Berna Biotech Italia S.r. l., formerly Istituto sieroterapico Berna S.r.l.) Hebrew University
inactivated MF59-adjuvanted vaccine inactivated MF59-adjuvanted split-virion vaccine inactivated whole virus vaccine inactivated vaccine inactivated subunit vaccine inactivated subunit vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated whole virus vaccine LAIV, needle-free inactivated subunit vaccine inactivated subunit MF59-adjuvanted vaccine inactivated split-virion vaccine inactivated vaccine inactivated subunit MF59-adjuvanted vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated split-virion vaccine, trivalent, recombinant inactivated split-virion vaccine LAIV (inactivated subunit ProteosomeTM-adjuvanted vaccine) inactivated split-virion vaccine LAIV LAIV inactivated vaccine inactivated vaccine inactivated aluminum phosphate gel-adjuvanted vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated subunit vaccine inactivated subunit virosome-adjuvanted vaccine inactivated whole virus vaccine (Continued on next page)
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Table 1. (Continued ) Commercial name GripguardÒ GripovaxÒ GrippolÒ / Grippol PlusÒ / Grippol NeoÒ ImmugripÒ ImmuvacÒ Imovax gripeÒ InflexalÒ V / Infectovac FluÒ / IsifluÒ / VirofluÒ Influ-kovaxÒ InflumixÒ InflupozziÒ Influsome-Vac InfluvacÒ / Influvac sub-unit / Influvac S Influvac PlusÒ InfluvacÒ TC^ InfluvirusÒ InvivacÒ IsigripÒ LevrisonÒ MastafluÒ MFVÒ MFV-jectÒ MonogrippolÒ / Monogrippol NeoÒ / Monogrippol PlusÒ MunevanÒ^ NasovacÒ NivgripÒ PreflucelÒ PrevigripÒ^ ProdigripÒ SandovacÒ SubinviraÒ TetagripÒ Vacuna antigripal PasteurÒ Vacuna antigripal polivalente LetiÒ VaxigripÒ / VaxigripÒ Junior / IstivacÒ / MutagripÒ / GripavacÒ / Inactivated Influenza Vaccine (Split Virion)Ò XanafluÒ
Marketing Authorisation Holder
Characteristics
Socopharm / Chiron, France GlaxoSmithKline, Belgium Petrovax, Russia
inactivated vaccine inactivated whole virus vaccine inactivated subunit Polyoxidonium-adjuvanted vaccine
Pierre Fabre Medicament Nezel / Solvay Pharma Aventis Pasteur Crucell, Leiden, The Netherlands / Infectopharm / Janssen-Cilag GmbH, Neuss, Germany Korea Vaccine, Korea Schiapparelli, Italy Seqirus (bioCSL, formerly Novartis) Hebrew University, Israel Abbott Biologicals
inactivated subunit vaccine inactivated vaccine inactivated virosome-adjuvanted inactivated vaccine inactivated whole virus vaccine inactivated subunit vaccine inactivated liposome-based IL-2/GM-CSF-adjuvanted vaccine inactivated subunit vaccine
Abbott Biologicals (formerly Solvay Pharmaceuticals) AbbVie (formerly Abbott Biologicals, formerly Solvay Pharmaceuticals) Nuovo Istituto Sieroterapico Milanese S.r.l., Milan, Italy Solvay Pharmaceuticals, Vienna, Austria KEDRION SpA, Italy Laboratorios Farmaceuticos ROVI, S.A., Spain MASTA Ltd., London, UK Servier, UK Sanofi Petrovax Pharm, Russia
inactivated virosome-adjuvanted vaccine inactivated subunit vaccine
CellTech (formerly Medeva) Serum Institute of India Nicolau Institute of Virology, Romania Baxter International, Vienna, Austria Socopharm / Chiron, France Aventis Pasteur MSD Sanofi Pasteur, Lyon, France Imuna, Czech Republic Sanofi Pasteur, Lyon, France Sanofi Pasteur MSD Leti, Spain
inactivated whole virus vaccine LAIV inactivated whole virus vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated MF59-adjuvanted vaccine inactivated subunit vaccine inactivated split-virion vaccine inactivated vaccine inactivated split-virion vaccine inactivated split-virion vaccine
Sanofi Pasteur, Lyon, France
inactivated split-virion vaccine
Abbott Biologicals B.V., the Netherlands
inactivated subunit vaccine
inactivated split-virion vaccine virosome-adjuvanted vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated subunit vaccine Inactivated whole virus vaccine inactivated whole virus vaccine Inactivated
Abbreviations: IM (intramuscular), IN (intranasal), LAIV (Live Actenuated Influenza Vaccine), SC (subcutaneous). Cell-culture derived x Insect-cell derived ^Currently discontinued
the coverage was unacceptably low: according to the most recently available data released by National Health Interview Survey, in the 2007–08 flu season, vaccination coverage among healthcare workers was 48%.29 Further, due to the broadening of vaccination recommendations that extended the suggestion of being vaccinated to all subjects aged 6 mo and older, vaccine shortage can be experienced, together with manufacturing difficulties. Intradermal (ID) vaccines, such as FluzoneÒ ID and IntanzaÒ , are therefore an attractive option to properly overcome these critical issues.
FluzoneÒ ID and intanzaÒ An ID trivalent split-virion influenza vaccine (FluzoneÒ ID, Sanofi Pasteur, Swiftwater, PA) has been approved by the Food and Drug Administration (FDA) on 10th May 2011 and been available in the
US since the 2011/2012 influenza season for adults aged 18–64 y. FluzoneÒ ID is available as single-dose, preservative-free pre-filled syringe that contains 9mg hemagglutinin (HA) per strain and exploits the innovative BD’s SoluviaTM microinjection device with a glass barrel, a stainless steel barrel with a 1.5-mm, 30-gauge needle and an elastomeric plunger stopper, produced by Becton-Dickinson (BD, Franklin Lakes, NJ).30-32 Intanza 9mg vaccine (also known in some countries as IDfluTM 9mg, Sanofi Pasteur, administered with a micro-injection system), identical to FluzoneÒ ID for antigen content, way of administration and injection system, received marketing authorization in the EU in February 2009, licensed by the European Medicines Agency (EMA) for adults 18–59 y of age since the 2010/11 season in Europe, and in Canada in September 2010. IstivacÒ ID is identifical to Fluzone ID and is commercialized in Argentina for adults 18–59 y of age, used successfully since 2010.
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For subjects older than 64 y in the USA and 60 y in Europe and Canada, FluzoneÒ ID high Dose and IntanzaÒ 15mg (also known in some countries as IDfluTM 15mg, Sanofi Pasteur; administered with a micro-injection system) are available. High-quality reviews on IntanzaÒ and FluzoneÒ are already available in the extant literature30,33-36 and the reader is recommended to refer to them for information concerning trials and studies published until 2012. The thrust of our current manuscript intends to update the current evidences on ID vaccines and to provide new insights and prospects on future developments in the field.
Mechanisms of action ID vaccination is not a novelty, being already known and performed since 1908.33 Although the intradermal route of vaccine delivery was extensively studied for several vaccination including typhoid fever, measles, cholera, rabies, hepatitis B and poliomyelitis,33 only influenza vaccines have been broadly administered by this route: possible issues that hampered the intradermal delivery for other vaccines include the high costs of technical development and the unacceptable local reactogenicity due to adjuvants contained in traditional formulations.37 Skin represents an optimal site for vaccination and elicits both innate and adaptive immune responses. Skin, covering an impressive surface area of 1.6–1.85 m2 and being situated at the interface between human body and environment,38 is an important barrier, both passive and active, against chemical, physical and microbial insults. From an anatomic point of view, skin is composed of an upper laying (the epidermis), a basement membrane and a lower laying (the dermis). The epidermis is 150–200 mm thick and comprises the stratum corneum, the stratum germinativum, the stratum lucidum (present only in some specific parts of the human body), the stratum granulosum, the stratum of Malpighi or stratum spinosum, and the stratum basale.37 The stratum corneum is particularly thick, consisting of dead cells (corneocytes) surrounded by lipid drafts and regions in the lamellar phases,39-40 and has a great importance, in that optimal strategies for drug/vaccine delivery have to overcome the presence of this ‘formidable’ physical barrier.38 As summarized in an excellent way by Gill and collaborators, there are different ways for an optimal drug/vaccine skin delivery: the first strategy is based on stratum corneum disruption (use of chemical enhancers, ultrasounds, and electroporation), the second is based on stratum corneum removal (tape stripping, abrasion, thermal ablation, and microdermabrasion), and the third is based on stratum corneum penetration (use of jet injectors, gene gun, and micro-needles).41 The dermis is 1.5–3 mm thick and, in its turn, can be divided into a papillary compartment (stratum papillare) and a reticular compartment (stratum reticulare), containing thin and thick collagen fibers, respectively.38 Hypodermis or subcutaneous tissue is 3–100 mm thick and is a layer of loose connective tissue and elastin.38 Further, skin harbours immune cellular components (epidermal dendritic cells or epidermal DCs, known also as Langerhans cells or LCs, dermal DCs or DDCs known also as interstitial or migratory DCs, ab T cells, gd T cells, natural
killer or NK cells, B cells, mast cells, and macrophages), thus constituting a immunocompetent, multi-tasking organ38-44 or a complex system (skin immune system or SIS).45 Skin includes, indeed, skin-associated lymphoid tissues (SALTs),46 which are responsible of a continuous cross-talk between skin (and its cellular components) and lymph nodes.38 SALTs are constituted by lymphoid follicles, vessels, antigen-presenting cells (APCs), and lymphocytes. Some scholars, referring to the unique, natural immune enhancer effect of the skin, have proposed the existence of a skin-mediated ‘adjuvant’ mechanism.38-44 However, the exact nature of this mechanism is complex and still poorly known. It can be hypothesized that the effect of ID vaccination may be the result of 3 concurring, complementary pathways (summarized in Table 2 and Fig. 2). Antigens are captured at skin level by resident, highly efficient APCs, like epidermal keratinocytes and specialized DCs, expressing high levels of class II major histocompatibility complex.38 Skin DCs belong to the non-lymphoid tissue (NLT) DC group, while the LT DC group comprises 3 subsets (namely, the conventional DCs or cDCs type 1, the cDCs type 2, and, finally, the plasmacytoid DCs or pDCs).47 Skin NLT DCs can be subdivided into 4 subsets: LCs within the suprabasal layers of the epidermis, expressing langerin; DDCs lacking langerin, which in their turn include DDCs expressing CD1a and DDCs expressing CD14; and finally, recruited macrophages or other innate immune cells, activated by the expression of Toll-like receptors (TLRs) and nucleotide-binding domain leucine-rich repeat receptors.38 CD141, known also as BDCA-3, THBD or thrombomodulin, is an important marker in differentiating the different DC subsets. LCs can mature interacting with e-cadherin expressed by keratinocytes and can crosstalk with Th1, Th2, Th17, Th22 (cells producing IL-22, but not IL-17), Treg, and can prime na€ıve CD8C T cells into effector cytotoxic T lymphocytes (CTLs), while CD1aC DDCs crosstalk with Th2 and CTLs, CD1aC CD141C DDCs with Th17, and CD14C CD141C DDCs with Th1, Tfh, Treg, and TC2, as well as induce the differentiation of na€ıve B cells into IgM-secreting plasma cells.48 This pathway plays undoubtedly a major role. The maturation, the differentiation, the acquisition of adequate immune abilities, and the migration to the paracortical area of the regional draining lymph nodes as afferent lymph veiled cells (ALVCs) through high endothelial venules (HEVs), are
Table 2. Overview of the 3 mechanisms at the basis of the action of intra-dermal vaccines. PATHWAY Dermal dendritic cellsdependent pathway Dermal dendritic cellsindependent pathway
Mechanical insults due to micro-needles
DESCRIPTION Involvement of skin-resident antigen-presenting cells Passive drainage of small antigenic components (
PRODUCT REVIEW
FluzoneÒ intra-dermal (IntanzaÒ /IstivacÒ Intra-dermal): An updated overview Nicola Luigi Bragazzia, Andrea Orsia,b, Filippo Ansaldia,b, Roberto Gasparinia, and Giancarlo Icardia,b a
Department of Health Sciences (DISSAL), University of Genoa, Genoa, Italy; bHygiene Unit, IRCCS AOU San Martino - IST of Genoa, Genoa, Italy
ABSTRACT
ARTICLE HISTORY
Influenza is a highly contagious respiratory acute viral disease which imposes a very heavy burden both in terms of epidemiology and costs, in the developed countries as well as in the developing ones. It represents a serious public health concern and vaccination constitutes an important tool to reduce or at least mitigate its burden. Despite the existence of a broad armamentarium against influenza and despite all the efforts and recommendations of international organisms to broaden immunization, influenza vaccination coverage is still far from being optimal. This, taken together with logistic and technical difficulties that can result into vaccine shortage, makes intra-dermal (ID) vaccines, such as FluzoneÒ ID and IntanzaÒ , particularly attractive. ID vaccines are comparable and, in some cases, superior to intra-muscular/ sub-cutaneous vaccines in terms of immunogenicity, safety, reactogenicity, tolerability and crossprotection profiles, as well as in terms of patient preference, acceptance and vaccine selection. Further advances, such as FluzoneÒ ID with alternative B strains and Quadrivalent FluzoneÒ ID or the possibility of self-administering the vaccines, make influenza ID vaccines even more valuable.
Received 19 February 2016 Revised 20 April 2016 Accepted 4 May 2016
Introduction Influenza Influenza is a highly contagious respiratory acute viral disease characterized by a worldwide distribution, a short incubation period (1–3 days, generally 2 days), usually mild respiratory and systemic symptoms, such as high fever, cough, sore throat, headache, chills, anorexia and fatigue.1,2 It can be asymptomatic in 30–50% of subjects.2,3 On the other hand, it may result into severe complications, such as bacterial pneumonia and exacerbation of underlying chronic conditions (including heart or respiratory failure, chronic obstructive pulmonary diseases or COPDs, among others), hospitalization and deaths, especially in frail and high-risk subjects.2 The burden of seasonal influenza as well as of influenza pandemics is very heavy, both in terms of epidemiology and costs, in the developed countries4 as well as in the developing ones.5 Indeed, the World Health Organization (WHO) estimates that annual epidemics affect up to 15% of the total population worldwide, causing up to 4–5 million severe cases and up to 500,000 deaths.6 For these reasons, influenza represents a serious public health concern and vaccination constitutes an important tool to reduce and mitigate the tremendous socioeconomic burden generated by influenza. Influenza is caused by a single-stranded, negative-sense RNA virus, Myxovirus influenzae, which belongs to the Orthomyxoviridae family together with Thogotovirus and Isavirus, and includes 3 serotypes or genera, A, B, and C. The genus A, first isolated in 1933,7 is the most clinically relevant and has the capacity to induce minor or major changes in its structure
KEYWORDS
cutaneous vaccination; FluzoneÒ ; influenza; IntanzaÒ ; intradermal vaccine; microneedle device; skin immunization
(antigenic drifts and antigenic shifts, respectively). In case of antigenic drifts, the virus causes interpandemic influenza (known also as annual epidemics or seasonal influenza). In case of antigenic shifts, it causes pandemic influenza. Pandemic influenza is caused by influenza virus genus A, while seasonal influenza by influenza genus A and genus B.2 Influenza virus has a quite complex replication cycle, achieved through various stages (Fig. 1).1 First, the virus attaches to the (a-2,3)- or (a-2,6)-linked sialic acid receptors present on the free surface of the cells of the upper respiratory tract or erythrocytes. During this step (termed as virus adsorption), the role of hemagglutinin (HA), a cylinder-shaped, homotrimeric integral type 1 membrane glycoprotein found on the surface of influenza viruses, is crucial. The virus can then enter the cells (internalization) by exploiting different routes (clathrin-mediated endocytosis or CME, caveolae-dependent endocytosis or CDE, clathrin-caveolaeindependent endocytosis, or macropinocytosis). CME is the most usual pathway; the virus is internalized into an endosomal compartment, from which it must emerge in order to release its nucleic acid into the cytosol (endosomal trafficking via endosomes/caveosomes/macropinosomes/lysosomes to the perinuclear compartment). During the phase of fusion of the viral envelope with the endosome membrane, after the pH has been reduced (pH-dependent fusion of viral and endosomal/organellar membranes and uncoating), HA plays again a major role. The ribonucleoprotein must then reach the nucleus (nuclear importation) in order to begin the process of translation of its genes and to transcribe and replicate its nucleic acid (transcription and replication). Subsequently, the RNA segments, surrounded by the nucleoproteins, must migrate to the cell membrane (nuclear exportation) in order
CONTACT Giancarlo Icardi [email protected] Department of Health Sciences, University of Genoa, Via A. Pastore 1, 16132 Genoa, Italy. Color versions of one or more of the figures in this article can be found online at www.tandfonline.com/khvi. © 2016 Taylor & Francis
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Figure 1. The steps of the replication cycle of the influenza virus are the following: 1) virus adsorption; 2) internalization into cellular regions by means of clathrin-mediated endocytosis (CME), caveolae-dependent endocytosis (CDE), clathrin-caveolae-independent endocytosis, and macropinocytosis; 3) endosomal trafficking; 4) pHdependent fusion of viral and endosomal / organellar membranes; 5) uncoating; 6) nuclear importation; 7) transcription and replication; 8) nuclear exportation; 9) protein synthesis; 10) post-translational processing and trafficking; 11) viral progeny assembly and packaging; 12) budding; and 13) release (modified from references1 and 4 ).
to enable further molecular processing (namely, protein synthesis, post-translational processing and trafficking, and viral progeny assembly and packaging). Finally, the virus must be freed to invade other cells of the respiratory tract (budding and release). All this is achieved through a complex, finely tuned, highly dynamic, and synchronized action of a vast array of molecular complexes that perform multiple enzymatic and catalytic reactions, whose details are currently known only in part.1
Overview of the market The pharmacological armamentarium against influenza includes different drugs and vaccines, which has been recently reviewed by Gasparini and collaborators.8 Current available drugs include NA inhibitors (NAIs), such as oseltamivir, zanamivir, and peramivir, and adamantane-based M2 protein blockers (amantadine and rimantadine). However, because of the biology of influenza virus and its frequent mutations, these drugs are plagued by the issue of resistance.9,10 A variety of vaccines exists against influenza.8 They can be basically divided into 2 categories: pandemics and seasonal vaccines. Further, they can divided into inactivated influenza vaccines and live, attenuated influenza vaccines (called LAIVs). The first category includes: whole virus vaccine, subunit vaccine made up of purified HA and NA proteins, and split-virion vaccine. Licensed prepandemic/pandemic vaccines (reviewed in 11,12) are shown in Table 1. Other investigational vaccines against
H7N9 or universal pandemic vaccines are still under clinical experimentation.13 Seasonal vaccines can be divided into inactivated splitvirion, inactivated subunit and LAIV vaccines (revised in 14-23). Recently, also seasonal adjuvanted vaccines such as those adjuvanted by MF59 or virosomes have become available (reviewed in24). Inactivated vaccines can be administered via the IM route in subjects aged 6 mo and older,25 while LAIVs may be given intra-nasally to healthy, non-pregnant people aged 2–49 y. They may safely be administered at the same time as other vaccines.26 For further details, the reader is referred to Table 1. Generally speaking, the overall efficacy of influenza vaccines is 59% against laboratory-confirmed cases of influenza according to the recent meta-analysis by Osterholm and collaborators.27 According to another meta-analysis it varies from 17% against influenza like illness (ILI) to 73% against confirmed influenza.28 There is therefore the need to develop more effective vaccines.
Influenza vaccination coverage Despite the fact that annual vaccination represents an important strategy for curbing influenza-related complications, the vaccination coverage is still far from being optimal. For example, in the USA, according to the National Immunization Survey-Flu and the National Internet Flu Survey, only 39.0% of all individuals aged 6 mo, that is to say 2 subjects out of 5, were vaccinated against influenza, leaving therefore most population unprotected (CDC, 2015). Also among health-care personnel,
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Table 1. Overview of the market with the main available influenza vaccines. Commercial name AdimFlu-SÒ AflunovÒ ArepanrixÒ^ CantgripÒ CelturaÒ CelvapanÒ DaronrixÒ^ FocetriaÒ^ FocliviaÒ Green Flu-SÒ HumenzaÒ^ PandemrixÒ / D-Pan H1N1Ò^ PanenzaÒ PanvaxÒ / PanvaxÒ Junior PrepandrixÒ / D-Pan H5N1Ò PumarixÒ^ Q-Pan H5N1Ò VepacelÒ AddigripÒ / AdiugripÒ Adjuvanted InflupozziÒ AlorbatÒ AnFluÒ AgrifluÒ AgrippalÒ BatrevacÒ BegrivacÒ Biaflu Ò / Biaflu zonaleÒ CAIV-TÒ ChirofluÒ DotaricinÒ ElvarixÒ EvagripÒ FluadÒ / Fluad pediatric / Chiromas / Gripguard FluarixÒ Fluarix TetraÒ / Influsplit Tetra / a-RIX-Tetra FlublokÒ x FlucelvaxÒ / OptafluÒ FluINsure FluLavalÒ FlumistÒ / FluenzÒ Flumist quadrivalentÒ / Fluenz TetraÒ FluShieldÒ FluVaccinolÒ Fluval ABÒ FluvaxÒ / AfluriaÒ / EnziraÒ / NilgripÒ / X-FluTM , Influenza Vaccine Ph. Eur. FluviralÒ FluvirinÒ FocusvaxÒ GripaxÒ
Marketing Authorisation Holder
Characteristics
Pandemic/prepandemic vaccines Adimmune Corporation, Taichung, Taiwan Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics S.r.l. Siena, Italy) GlaxoSmithKline, Rixensart, Belgium
trivalent inactivated split-virion H1N1 pandemic vaccine monovalent inactivated surfacen antigen MF59-adjuvanted H5N1 prepandemic vaccine monovalent inactivated split-virion AS03-adjuvanted H1N1 vaccine INCDMI CANTACUZINO – Romania monovalent inactivated H1N1 vaccine Seqirus (bioCSL, formerly Novartis) monovalent inactivated MF59-adjuvanted H1N1 vaccine Baxter International, Vienna, Austria monovalent inactivated whole virus H1N1 vaccine GlaxSmithKline Biologicals, Rixensart, Belgium monovalent whole virus inactivated H5N1 mock-up vaccine Seqirus (bioCSL, formerly Novartis) monovalent inactivated MF59-adjuvanted H1N1 vaccine Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics S.r.l., monovalent inactivated surface antigen MF59-adjuvanted H5N1 Siena, Italy) mock-up vaccine Green Cross Corporation, Korea monovalent inactivated split-virion H1N1 pandemic vaccine Sanofi Pasteur, Lyon, France monovalent inactivated split-virion AF03-adjuvanted H1N1 pandemic vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H1N1 pandemic vaccine Sanofi Pasteur, Lyon, France monovalent inactivated split-virion H1N1 pandemic vaccine CSL Biotherapies, Parkville, Australia monovalent inactivated split-virion H1N1 vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H5N1 prepandemic vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H5N1 pandemic vaccine GlaxoSmithKline Biologicals, Rixensart, Belgium monovalent inactivated split-virion AS03-adjuvanted H5N1 vaccine Baxter International, Vienna, Austria monovalent inactivated whole virus H5N1 vaccine Seasonal vaccines Sanofi Pasteur (bioCSL, formerly Novartis Vaccines and Diagnostics S.r.l., Siena, Italy) Seqirus (bioCSL, formerly Novartis) Asta Pharma, Ho Chi Minh City, Vietnam Sinovac Kexing Biological Product Co., Ltd Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics Limited) Seqirus (bioCSL, formerly Novartis) Abbott srl Chiron, France KEDRION SpA, Italy (formerly Farmabiagini, Italy) Medimmune LLC, Maryland, USA / AstraZeneca (formerly Aviron, Mountain View, CA, USA) Seqirus (bioCSL, formerly Novartis) Alentia Biotech S.L., Granada, Spain VEB Sachsesches Serumwerk Dresden Seqirus (bioCSL, formerly Novartis) Seqirus (bioCSL, formerly Novartis, formerly Chiron Vaccines, Siena, Italy) GlaxoSmithKline Biologicals, Rixensart, Belgium GlaxoSmithKline Biologicals, Rixensart, Belgium Protein Sciences Corporation, Meriden, CT and Pearl River, NY, USA Seqirus (bioCSL, formerly Novartis) ID Biomedical Canada (formerly Intellivax International) GlaxoSmithKline Biologicals, Rixensart, Belgium Medimmune LLC, Maryland, USA / AstraZeneca (formerly Aviron) Medimmune LLC, Maryland, USA / AstraZeneca (formerly Aviron, Mountain View, CA, USA) Wyeth Lederle Vaccines, USA BGP GmbH, Vienna, Austria / STADA Medical GmbH, Germany Omninvest Vaccine Manufacturing, Researching and Trading Ltd., Hungary CSL Biotherapies, Parkville, Australia / bioCSL GmbH, Marburg, Germany / Pfizer Vaccines, UK / Instituto Biologico Argentino SAIC, Argentina GlaxoSmithKline Biologicals, Rixensart, Belgium Seqirus (bioCSL, formerly Novartis Vaccines and Diagnostics Limited) Crucell, Leiden, the Netherlands (formerly Berna Biotech Italia S.r. l., formerly Istituto sieroterapico Berna S.r.l.) Hebrew University
inactivated MF59-adjuvanted vaccine inactivated MF59-adjuvanted split-virion vaccine inactivated whole virus vaccine inactivated vaccine inactivated subunit vaccine inactivated subunit vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated whole virus vaccine LAIV, needle-free inactivated subunit vaccine inactivated subunit MF59-adjuvanted vaccine inactivated split-virion vaccine inactivated vaccine inactivated subunit MF59-adjuvanted vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated split-virion vaccine, trivalent, recombinant inactivated split-virion vaccine LAIV (inactivated subunit ProteosomeTM-adjuvanted vaccine) inactivated split-virion vaccine LAIV LAIV inactivated vaccine inactivated vaccine inactivated aluminum phosphate gel-adjuvanted vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated subunit vaccine inactivated subunit virosome-adjuvanted vaccine inactivated whole virus vaccine (Continued on next page)
HUMAN VACCINES & IMMUNOTHERAPEUTICS
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Table 1. (Continued ) Commercial name GripguardÒ GripovaxÒ GrippolÒ / Grippol PlusÒ / Grippol NeoÒ ImmugripÒ ImmuvacÒ Imovax gripeÒ InflexalÒ V / Infectovac FluÒ / IsifluÒ / VirofluÒ Influ-kovaxÒ InflumixÒ InflupozziÒ Influsome-Vac InfluvacÒ / Influvac sub-unit / Influvac S Influvac PlusÒ InfluvacÒ TC^ InfluvirusÒ InvivacÒ IsigripÒ LevrisonÒ MastafluÒ MFVÒ MFV-jectÒ MonogrippolÒ / Monogrippol NeoÒ / Monogrippol PlusÒ MunevanÒ^ NasovacÒ NivgripÒ PreflucelÒ PrevigripÒ^ ProdigripÒ SandovacÒ SubinviraÒ TetagripÒ Vacuna antigripal PasteurÒ Vacuna antigripal polivalente LetiÒ VaxigripÒ / VaxigripÒ Junior / IstivacÒ / MutagripÒ / GripavacÒ / Inactivated Influenza Vaccine (Split Virion)Ò XanafluÒ
Marketing Authorisation Holder
Characteristics
Socopharm / Chiron, France GlaxoSmithKline, Belgium Petrovax, Russia
inactivated vaccine inactivated whole virus vaccine inactivated subunit Polyoxidonium-adjuvanted vaccine
Pierre Fabre Medicament Nezel / Solvay Pharma Aventis Pasteur Crucell, Leiden, The Netherlands / Infectopharm / Janssen-Cilag GmbH, Neuss, Germany Korea Vaccine, Korea Schiapparelli, Italy Seqirus (bioCSL, formerly Novartis) Hebrew University, Israel Abbott Biologicals
inactivated subunit vaccine inactivated vaccine inactivated virosome-adjuvanted inactivated vaccine inactivated whole virus vaccine inactivated subunit vaccine inactivated liposome-based IL-2/GM-CSF-adjuvanted vaccine inactivated subunit vaccine
Abbott Biologicals (formerly Solvay Pharmaceuticals) AbbVie (formerly Abbott Biologicals, formerly Solvay Pharmaceuticals) Nuovo Istituto Sieroterapico Milanese S.r.l., Milan, Italy Solvay Pharmaceuticals, Vienna, Austria KEDRION SpA, Italy Laboratorios Farmaceuticos ROVI, S.A., Spain MASTA Ltd., London, UK Servier, UK Sanofi Petrovax Pharm, Russia
inactivated virosome-adjuvanted vaccine inactivated subunit vaccine
CellTech (formerly Medeva) Serum Institute of India Nicolau Institute of Virology, Romania Baxter International, Vienna, Austria Socopharm / Chiron, France Aventis Pasteur MSD Sanofi Pasteur, Lyon, France Imuna, Czech Republic Sanofi Pasteur, Lyon, France Sanofi Pasteur MSD Leti, Spain
inactivated whole virus vaccine LAIV inactivated whole virus vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated MF59-adjuvanted vaccine inactivated subunit vaccine inactivated split-virion vaccine inactivated vaccine inactivated split-virion vaccine inactivated split-virion vaccine
Sanofi Pasteur, Lyon, France
inactivated split-virion vaccine
Abbott Biologicals B.V., the Netherlands
inactivated subunit vaccine
inactivated split-virion vaccine virosome-adjuvanted vaccine inactivated split-virion vaccine inactivated split-virion vaccine inactivated subunit vaccine Inactivated whole virus vaccine inactivated whole virus vaccine Inactivated
Abbreviations: IM (intramuscular), IN (intranasal), LAIV (Live Actenuated Influenza Vaccine), SC (subcutaneous). Cell-culture derived x Insect-cell derived ^Currently discontinued
the coverage was unacceptably low: according to the most recently available data released by National Health Interview Survey, in the 2007–08 flu season, vaccination coverage among healthcare workers was 48%.29 Further, due to the broadening of vaccination recommendations that extended the suggestion of being vaccinated to all subjects aged 6 mo and older, vaccine shortage can be experienced, together with manufacturing difficulties. Intradermal (ID) vaccines, such as FluzoneÒ ID and IntanzaÒ , are therefore an attractive option to properly overcome these critical issues.
FluzoneÒ ID and intanzaÒ An ID trivalent split-virion influenza vaccine (FluzoneÒ ID, Sanofi Pasteur, Swiftwater, PA) has been approved by the Food and Drug Administration (FDA) on 10th May 2011 and been available in the
US since the 2011/2012 influenza season for adults aged 18–64 y. FluzoneÒ ID is available as single-dose, preservative-free pre-filled syringe that contains 9mg hemagglutinin (HA) per strain and exploits the innovative BD’s SoluviaTM microinjection device with a glass barrel, a stainless steel barrel with a 1.5-mm, 30-gauge needle and an elastomeric plunger stopper, produced by Becton-Dickinson (BD, Franklin Lakes, NJ).30-32 Intanza 9mg vaccine (also known in some countries as IDfluTM 9mg, Sanofi Pasteur, administered with a micro-injection system), identical to FluzoneÒ ID for antigen content, way of administration and injection system, received marketing authorization in the EU in February 2009, licensed by the European Medicines Agency (EMA) for adults 18–59 y of age since the 2010/11 season in Europe, and in Canada in September 2010. IstivacÒ ID is identifical to Fluzone ID and is commercialized in Argentina for adults 18–59 y of age, used successfully since 2010.
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For subjects older than 64 y in the USA and 60 y in Europe and Canada, FluzoneÒ ID high Dose and IntanzaÒ 15mg (also known in some countries as IDfluTM 15mg, Sanofi Pasteur; administered with a micro-injection system) are available. High-quality reviews on IntanzaÒ and FluzoneÒ are already available in the extant literature30,33-36 and the reader is recommended to refer to them for information concerning trials and studies published until 2012. The thrust of our current manuscript intends to update the current evidences on ID vaccines and to provide new insights and prospects on future developments in the field.
Mechanisms of action ID vaccination is not a novelty, being already known and performed since 1908.33 Although the intradermal route of vaccine delivery was extensively studied for several vaccination including typhoid fever, measles, cholera, rabies, hepatitis B and poliomyelitis,33 only influenza vaccines have been broadly administered by this route: possible issues that hampered the intradermal delivery for other vaccines include the high costs of technical development and the unacceptable local reactogenicity due to adjuvants contained in traditional formulations.37 Skin represents an optimal site for vaccination and elicits both innate and adaptive immune responses. Skin, covering an impressive surface area of 1.6–1.85 m2 and being situated at the interface between human body and environment,38 is an important barrier, both passive and active, against chemical, physical and microbial insults. From an anatomic point of view, skin is composed of an upper laying (the epidermis), a basement membrane and a lower laying (the dermis). The epidermis is 150–200 mm thick and comprises the stratum corneum, the stratum germinativum, the stratum lucidum (present only in some specific parts of the human body), the stratum granulosum, the stratum of Malpighi or stratum spinosum, and the stratum basale.37 The stratum corneum is particularly thick, consisting of dead cells (corneocytes) surrounded by lipid drafts and regions in the lamellar phases,39-40 and has a great importance, in that optimal strategies for drug/vaccine delivery have to overcome the presence of this ‘formidable’ physical barrier.38 As summarized in an excellent way by Gill and collaborators, there are different ways for an optimal drug/vaccine skin delivery: the first strategy is based on stratum corneum disruption (use of chemical enhancers, ultrasounds, and electroporation), the second is based on stratum corneum removal (tape stripping, abrasion, thermal ablation, and microdermabrasion), and the third is based on stratum corneum penetration (use of jet injectors, gene gun, and micro-needles).41 The dermis is 1.5–3 mm thick and, in its turn, can be divided into a papillary compartment (stratum papillare) and a reticular compartment (stratum reticulare), containing thin and thick collagen fibers, respectively.38 Hypodermis or subcutaneous tissue is 3–100 mm thick and is a layer of loose connective tissue and elastin.38 Further, skin harbours immune cellular components (epidermal dendritic cells or epidermal DCs, known also as Langerhans cells or LCs, dermal DCs or DDCs known also as interstitial or migratory DCs, ab T cells, gd T cells, natural
killer or NK cells, B cells, mast cells, and macrophages), thus constituting a immunocompetent, multi-tasking organ38-44 or a complex system (skin immune system or SIS).45 Skin includes, indeed, skin-associated lymphoid tissues (SALTs),46 which are responsible of a continuous cross-talk between skin (and its cellular components) and lymph nodes.38 SALTs are constituted by lymphoid follicles, vessels, antigen-presenting cells (APCs), and lymphocytes. Some scholars, referring to the unique, natural immune enhancer effect of the skin, have proposed the existence of a skin-mediated ‘adjuvant’ mechanism.38-44 However, the exact nature of this mechanism is complex and still poorly known. It can be hypothesized that the effect of ID vaccination may be the result of 3 concurring, complementary pathways (summarized in Table 2 and Fig. 2). Antigens are captured at skin level by resident, highly efficient APCs, like epidermal keratinocytes and specialized DCs, expressing high levels of class II major histocompatibility complex.38 Skin DCs belong to the non-lymphoid tissue (NLT) DC group, while the LT DC group comprises 3 subsets (namely, the conventional DCs or cDCs type 1, the cDCs type 2, and, finally, the plasmacytoid DCs or pDCs).47 Skin NLT DCs can be subdivided into 4 subsets: LCs within the suprabasal layers of the epidermis, expressing langerin; DDCs lacking langerin, which in their turn include DDCs expressing CD1a and DDCs expressing CD14; and finally, recruited macrophages or other innate immune cells, activated by the expression of Toll-like receptors (TLRs) and nucleotide-binding domain leucine-rich repeat receptors.38 CD141, known also as BDCA-3, THBD or thrombomodulin, is an important marker in differentiating the different DC subsets. LCs can mature interacting with e-cadherin expressed by keratinocytes and can crosstalk with Th1, Th2, Th17, Th22 (cells producing IL-22, but not IL-17), Treg, and can prime na€ıve CD8C T cells into effector cytotoxic T lymphocytes (CTLs), while CD1aC DDCs crosstalk with Th2 and CTLs, CD1aC CD141C DDCs with Th17, and CD14C CD141C DDCs with Th1, Tfh, Treg, and TC2, as well as induce the differentiation of na€ıve B cells into IgM-secreting plasma cells.48 This pathway plays undoubtedly a major role. The maturation, the differentiation, the acquisition of adequate immune abilities, and the migration to the paracortical area of the regional draining lymph nodes as afferent lymph veiled cells (ALVCs) through high endothelial venules (HEVs), are
Table 2. Overview of the 3 mechanisms at the basis of the action of intra-dermal vaccines. PATHWAY Dermal dendritic cellsdependent pathway Dermal dendritic cellsindependent pathway
Mechanical insults due to micro-needles
DESCRIPTION Involvement of skin-resident antigen-presenting cells Passive drainage of small antigenic components (
