295
biotopics Glossary
come more members- both associate and core facility). A general picture o ~ y can be given here. Caveat
The best peptides generally came from facilities employing the FMOC chemistry, particularly where morereactive coupling reagents had been used. The amino acid composition analyses were very similar on all samples but, and here is the note of caution, this was a very poor indicator of sample homogeneity. Also disturbing was the observation that a number of heterogeneous samples appeared homogeneous either on CE or HPLC or even by both methods. Despite the general media 'hype', CE was no more advantageous than HPLC in revealing problems. Mass spectrometry turned out to be the single most important technique for evaluating synthetic peptide quality. No small contributing factor was that not only could heterogeneities be detected, but the nature of the impurities could usually be inferred from the known masses of side chain protecting groups. The synthetic peptides received had amino acid deletions, oxidized residues and a range of incom-
tBOC - tertiary butyloxycarbonyl group [(CH3)3C-O-CO-] used as blocking agent for the
amino group of amino acids in solid phase protein synthesis. FIMOC - 9-fluorenyl methyl oxycarbonyl group used as a blocking agent for the amino
function. It is stable to acid but removeable in mild base. pletely removed protecting groups and synthesis reagent adducts. Electrospray gave a more representative picture than plasma desorption, which tended to over-emphasize some of the contaminating products, possibly because of the hydrophobic nature of blocking groups retained in these. HPLC linked to dectrospray was the most discriminating form of analysis. It was then revealed that only around 10% of core facilities have routine access to mass spectrometry - a surprising and, in view of the results, worrying statistic. Why worrying? Well, the final assessment- bioassay of the contributed peptides showed that the contributed peptides (which had passed the amino acid composition test) varied very widely in quality. It is upon the resuits of a bioassay, that conclusions will be drawn and the scientific paper based. In summary, although current methods for peptide synthesis are
very good and there were excellent products (>95% homogeneous) among the ABRF peptides, the survey points out weaknesses in custom synthesis. It also demonstrates that core facilities are, at present, not as well equipped as they could be to recognize problems when they do occur. The importance is that many conclusions will be drawn and published on the assumption that the custom peptide is precisely what it should be. References 1 Chakrabartty, A., Schellman, J. A. and Baldwin, R. L. (1991) Nature351,586-588 2 Elliot, T., Cerundolo, V., Elvin, J. and Townsend, A. (1991) Nature351,402-406 3 Frenz,J. and Hancock, W. S. (1991) Trends Biotechnol. 9, 243-250 4 Geisow, M.J. (1990) Trends Biotechnol. 8, 301-303
Michael J. Geisow Biodigm, 81 Kneeton Road, East Bridgford, NottinghamNG13 8PH, UK.
Targeting peptides and proteins: NATO ASI Proteins and polypeptides, because of their size, complex physical properties and diverse functions and sites of action, present unique challenges in their use as therapeutic agents. A recent NATO Advanced Studies Institute (ASI) meeting* was concerned not only with the problems of targeting in vivo natural, synthetic and engineered proteins and peptides, but also with the crafting ofpolypeptides as carriers of drugs or toxins. Molecules such as single chain ribosome inactivating protein, or peptides of the extracellular V1 domain of the CD4 *A NATO AS! on 'Targeting of Drugs: the Challenge of Peptides and Proteins', directed by G. Gregoriadis, A. T. Florence and G. Poste was held at Cape Sounion Beach, Greece fiom 24June to 5 July, 1991.
cell-surface receptor of HIV, represent some of the highly specific agents that were discussed. While these may act with high degrees of precision in vitro, the problem of administration and subsequent targeting of the proteins and peptide constructs to their sites of action in the whole organism provided the main thrust of the meeting. Language and other vehicles for deliver}" Participants were drawn from two main camps, the molecular manipuhtors and immunologists forming one rehtively homogeneous grouping, and drug targeters the other. Placed in close contact for 12 days, in lectures and the vital tutorial sessions, there was considerable intellectual cross-fertilization, but
© 1991, Elsevier Science PublishersLtd (UK) 0167 - 9430/91/$2.00
there were two almost distinct (sometimes coded) languages to be learned (as often happens in science), which hinders the facility of transitions between disciplines. It is essential that they do fuse and work together, as George Poste (SmithKline-Beecham, Philadelphia USA) pointed out forcibly, since progress in our ability to generate complex molecules has, he maintained, outstripped our capacity to develop suitable delivery systems to optimize their applicability. The greatest challenge is the development of systems for the delivery of autocrine/ paracrine molecules which act at extravascular sites, and to deliver a wider range of endo~nous mob ecules (such as gonadotropin) and their analogues in a manner which reflects the natural periodicity of delivery. Intravenous (IV) administration of autocrine/paracrine
meeting report
TIBTECHSEPTEMBER1991 (VOL9)
296
forum mediators results in the exposure of many tissues to these agents which they do not normally encounter. The resulting toxicities may be lifethreatening. Even if the IV route is the route of choice (as it can be for many agents that act in the blood compartment), the circulating half-life of many proteins with molecular masses greater than 40 kDa may be severely curtailed by their interaction with specific receptors, either for proteins (e.g. tPA, tissue type plasminogen activator), or for carbohydrate moieties, or complex formulations. Theo van Berkel (University of Leiden, The Netherlands) discussed strategies to prolong the presence of proteins in blood. This can be achieved by altering the physical properties of the protein, for example by covalent linkage of polyoxyethylene glycol molecules (-5 kDa) (Abraham Abuchowski [Enzon Inc., USA], Alec Sehon [University of Manitoba, Canada]), or, as in the case of tPA, pre-treatment with the protein (or low molecular-mass partial analogue) to block the receptors that are responsible for removal of that protein 1. Modification of proteins with hydrophilic polymers can render them tolerogenic 2. It can usually also lead to decreased biological activity, but this is thought to be compensated for by increased circulation lifetimes, thus maximizing the opportunity for uptake and interaction at the desired site. The exact correlation between biological activity and half-life does not appear to have been established.
Delivery by stealth Man-made carriers for proteins, such as liposomes and micropartides, invariably suffer fairly rapid loss in the reticuloendothelial system (ILl/S). The ILES may be a target in the treatment of leishmaniasis, other microbial diseases or certain carcinomas of the fiver, but if the target cells are elsewhere (e.g. in the blood or in extravascular tissues), then maintenance of the carrier systems in the circulation is of interest. Latest advances3 in the development of'long-fife' liposomes or extended half-life liposomes - the term 'stealth' has been trademarked - by incorporation into the lipid bilayers of liposomes of amphipathic polyoxyethylated derivatives or GM1 ganglioside were discussed by TIBTECHSEPTEMBER1991 (VOL9)
Alberto Gabizon (Hadassah Medical Organization, Jerusalem, Israel), and the marked reduction in liver sequestration of such liposomes and increased therapeutic efficiency was illustrated4. Manipulation of the fate of carriers, through control of lipo-: some diameter, bilayer fluidity and even flexibility, led to the re-statement of the fact that there is no such thing as 'the liposome'. Site-directed therapy is one goal of incorporating drugs in carriers such as immunoliposomes s (Leaf Huang, University of Tennessee, USA) possessing surface-oriented antibodies to adhere to tumour antigens. Frequendy the targets are extravascular. A still raging controversy is the question ofextravasation of both proteins and their carriers to target tissues. Phillip Thorpe (University of Texas, Southwestern Medical School, Dallas, USA) drew attention, not only to the possibility of the passage of delivery systems through the incomplete developing tumour vasculature, but also to the problems which might be encountered thereafter (e.g. the generally poor penetration .of immunotoxins; typically 0.001% per gram of tumour). Tumour-antigen heterogeneity and the fact that life-sustaining tissues also often express the target antigen will remain as formidable challenges to selective therapy. One alternative strategy is to target toxins to the tumour vasculature itselt~ it was applicable to many types of solid tumour and, as up to 1000 cells in the tumour are dependent on one endothelial cell, potentially efficient. Anti-fibrinectinreceptor antibody targets the basement membrane, and is therefore a candidate as a toxin delivery vehicle.
The importance of interactions In general, however, researchers involved in developing methods of toxin delivery were less buoyant than at previous meetings (e.g. the ASI in !989 on the same general theme). The maintenance of immunotoxin molecules in high concentrations in the circulation is essential to achieve appropriate levels of toxicity at the target. The concomitant toxicities, according to Ellen Vitetta (University of Texas, Southwestern Medical School, Dallas, USA), have to be coped with. In vitro, the molecular interactions exhibited by these molecules are exquisitely timed. Understanding
the nature of the interactions is of paramount importance (as an example, interactions between the CD4 molecules on the surface of cells and the envelope glycoprotein gp120 of HIV occur in vivo with drastic effects). The application 6 of this knowledge to active therapeutic ends, however, is often bedevilled by the complexity of the milieu in which the systems operate, and the vagaries of the pathway between administration site and target. Part of the ultimate solution is to design and produce smaller mob ecules which do not have the transport [imitations of the larger parent molecules but retain the specificity of action. Maurice Hofnung (Institut Pasteur, Paris, France) discussed hybrid bacterial envelope protein vectors designed 7 by altering 'permissive' sites and avoiding change to 'non-permissive' sites which can lead to the production of unstable, toxic or insoluble recombinant proteins. Therapeutic application of anti-lymphocyte monoclonal antibodies 8 produced in humanized form to reduce immunogenicity on repeated use, and antibodies as immunosuppressants and immunostimulators diverting T-cells to release cytokines and become cytotoxic were discussed by Herman Waldmann (New Addenbrookes Laboratories, Cambridge, UK).
Choosing a route Another approach to delivery of proteins and peptides is to explore routes of administration which can adventitiously avoid some of the problems of the IV route. The oral, rectal and nasal routes represent clinical alternatives for drug delivery. The oral route in particular has many attractions for chronic administration of proteins such as insulin, as Murray Saffran (Medical College of Ohio, USA) pointed out. Avoiding gastric destruction by coating capsules of insulin with an azo-polymer that is degraded by the bacterial flora of the colon, clinically useful responses were found even though the bioavailability per os was in the order of 1-2%. Alexander Florence (University of London, UK) presented further evidence of oral uptake of nanoparticles (potential carriers) by the M-ceil of Peyer's patches, site of uptake of antigens, macromolecules, bacteria and viral particles. Still a somewhat controversial subject, quantitative determination of a
297
forum polystyrene carrier showed that around 3% of the administered dose of 50 nm particles reached the liver, while 1% penetrated to the spleen 1°. Roger Ash (University of Bradford, UK), working with an unusual experimental model (fish) that is devoid of Peyer's patches, produced evidence 11 of uptake of somatotropim and other proteins by oral and rectal routes. Optimization of function of another group of peptides and proteins, the new-generation vaccines, is testing the wit of both camps referred to earlier. Most of the recombinant subunit and synthetic peptide vaccines are non- or poorly immunogenic but a number of emerging approaches (including the use of sophisticated immunological adjuvants) are now capable of proyoking potent immune responses to antigens. Anthony Allison (Syntex Research, Palo Alto, USA) described adjuvant folmulations such as a squahne Pluronic® co-polymer emulsion which is thought to act by targeting antigens to antigenpresenting cells n. Another system, liposomes, [discussed by Gregory Gregoriadis (University of London, UK)], has successfully been applied 13 with numerous bacterial,
viral, protozoan and tumour antigem. In addition, the great structural versatility of liposomes has been instrumental in their use in vaccines in conjunction with cytokines such as interleukin-2, with ligands which target antigen-presenting cells or even as a means to overcome genetic restriction of animals to mount an immune response to certain peptides. Nature has taken many millions of years to evolve the complex series of compartments that comprise the mammalian body. It is perhaps too much to expect, even inspired by the sight of the ancient Temple of Poseidon, that in the space of 12 days, we would have addressed all of the many problems of design, delivery and targeting of complex proteim. References 1 Rijken, D. C., Otter, M., Kuiper,J. and van Berkel,Th. J. C. (1990) Thromb. Res. Suppl. 49, 63-71 2 Takata, M., Maid, P. K., Kubo, R. T., Chen, Y., Holford-Stevens,V., Rector, E. and Sehon, A. H. (1990)J. Immunol. 145, 2846-2853 $ Gregoriadis,G. (1988)in 12posomesas Drug Canim : Reant
Trmds and
Progress,
(G~goriadis, G., ed.), pp. 3-18, John Wiley & Sons
4 Gabizon, A., Price, D., Huberty,J., Bresailer, IL and Papahadjopoulos,D. (1990) CancerRes. 50, 6371-6378 $ Mamyam, K., Kennel,S.J. and Huang,L. (1990) Pr0c. Natl Acad. SCi. USA 87, 5744-5748 6 Till, M. A., Ghede, V., May,R. D. Auerbach, P. C., Zolh-Pamer, S., Gomy, M. K., Gregory,T., Uhr,J. W. and Vitetta,E. S. (1990)2.aDS 3, 609-614 7 Lederc, C., Mag~ean, P., van der Weft, S., Deriand, E., Duphy, P. and Hofnang, M. (1990).].lmmunol. 144,3174-3182 8 Waldmann,H. (1989)Annu. Rev. lmmunol. 7, 407-444
9 Saffran,M., Kumar,G. S., Neckers,D. C., Peria, J., Jones, R. H, and Field, J. B. (1990) Biochem. Soc. Trans. 18, 752-754 10 Jani, p. U., Halbert, G. W., Langridge,J. and Florence,A. T. (1990)J. Pharm. Pharmacol. 42, 821-826 11 McLean, E., Ash, IL and Westcott, P. A. B. (1989)Aquaculture79, 411-415 12 Byars, N. E., Allison, A. C., Ham.an, M. W. and Kendall,A. P. (1990) Vaccine5, 223-228
13 Gregoriadis,G. (1990) lmmunol. TodaIt 11, 89-97
Alexander T. Florence Gregory Gregoriadis Centrefor Drag Delivery Research.~..e School of Pharmacy, University of London, London W C I N IAX, UK.
Biotechnologyand sustainable development in the Third World A recent international public debate on 'Biotechnology and Farmers' Rights; Opportunities and Threats for Small-Scale Farmers in Developing Countries'* has hig~ighted the importance oi'biotecimc!cgy in meeting the challenges of sustainable rural devdopment in the Third World. Current biotechnological developments are more likely to threaten than to support sustainable rural development in the Third World. *The debate was organized by the Department of Biology and Society (Vrije Universiteit Amsterdam) and the Netherlands Organization for International Development and Cooperation (NOVIB) and held 8-9 April 1991, at the University of Amsterdam, The Netherlands.
Market forces direct the agricultural research agendas o f private companies and o f public research institutes with emphasis on industrial appfications and capitalintense, well-controlled large-scale farming systems and the substitution o f agricultural raw products. Furthermore, the increasing influence of biotechnology in plant breeding is resulting in the introduction of procedures often requiring high levels o f investment and which are directed at developing new, patentable varieties of crops. These patents would enable plant breeders in developed countries to obtain property rights to genetic resources which have become available as a result o f the efforts of local communities in developing countries who have
(~) 1991, ElsevierScience PublishersLtd (UK) 0167-9430/91152.00
maintained and developed local varieties of crops for centuries. The one-sided direction of current biotechnological research is not inherent to the technology itself, The starting point for the recent public debate was the assumption that current biotechnological research does have the potential to yield interesting and beneficial results for small-scale farmers in developing countries. Moreover, the organizers o f the debate assumed that small-scale farmers in developing countries have as much right to technologies suitable for them as their large-scale colleagues. So far, virtually no effort has been made to address the threats to the poorest farmers of the Third World. Opportunities to do so have scarcely been examined, let alone realized. The discussion
meeting report
TIBTECHSEPTEMBER1991 (VOL9)
biotopics Glossary
come more members- both associate and core facility). A general picture o ~ y can be given here. Caveat
The best peptides generally came from facilities employing the FMOC chemistry, particularly where morereactive coupling reagents had been used. The amino acid composition analyses were very similar on all samples but, and here is the note of caution, this was a very poor indicator of sample homogeneity. Also disturbing was the observation that a number of heterogeneous samples appeared homogeneous either on CE or HPLC or even by both methods. Despite the general media 'hype', CE was no more advantageous than HPLC in revealing problems. Mass spectrometry turned out to be the single most important technique for evaluating synthetic peptide quality. No small contributing factor was that not only could heterogeneities be detected, but the nature of the impurities could usually be inferred from the known masses of side chain protecting groups. The synthetic peptides received had amino acid deletions, oxidized residues and a range of incom-
tBOC - tertiary butyloxycarbonyl group [(CH3)3C-O-CO-] used as blocking agent for the
amino group of amino acids in solid phase protein synthesis. FIMOC - 9-fluorenyl methyl oxycarbonyl group used as a blocking agent for the amino
function. It is stable to acid but removeable in mild base. pletely removed protecting groups and synthesis reagent adducts. Electrospray gave a more representative picture than plasma desorption, which tended to over-emphasize some of the contaminating products, possibly because of the hydrophobic nature of blocking groups retained in these. HPLC linked to dectrospray was the most discriminating form of analysis. It was then revealed that only around 10% of core facilities have routine access to mass spectrometry - a surprising and, in view of the results, worrying statistic. Why worrying? Well, the final assessment- bioassay of the contributed peptides showed that the contributed peptides (which had passed the amino acid composition test) varied very widely in quality. It is upon the resuits of a bioassay, that conclusions will be drawn and the scientific paper based. In summary, although current methods for peptide synthesis are
very good and there were excellent products (>95% homogeneous) among the ABRF peptides, the survey points out weaknesses in custom synthesis. It also demonstrates that core facilities are, at present, not as well equipped as they could be to recognize problems when they do occur. The importance is that many conclusions will be drawn and published on the assumption that the custom peptide is precisely what it should be. References 1 Chakrabartty, A., Schellman, J. A. and Baldwin, R. L. (1991) Nature351,586-588 2 Elliot, T., Cerundolo, V., Elvin, J. and Townsend, A. (1991) Nature351,402-406 3 Frenz,J. and Hancock, W. S. (1991) Trends Biotechnol. 9, 243-250 4 Geisow, M.J. (1990) Trends Biotechnol. 8, 301-303
Michael J. Geisow Biodigm, 81 Kneeton Road, East Bridgford, NottinghamNG13 8PH, UK.
Targeting peptides and proteins: NATO ASI Proteins and polypeptides, because of their size, complex physical properties and diverse functions and sites of action, present unique challenges in their use as therapeutic agents. A recent NATO Advanced Studies Institute (ASI) meeting* was concerned not only with the problems of targeting in vivo natural, synthetic and engineered proteins and peptides, but also with the crafting ofpolypeptides as carriers of drugs or toxins. Molecules such as single chain ribosome inactivating protein, or peptides of the extracellular V1 domain of the CD4 *A NATO AS! on 'Targeting of Drugs: the Challenge of Peptides and Proteins', directed by G. Gregoriadis, A. T. Florence and G. Poste was held at Cape Sounion Beach, Greece fiom 24June to 5 July, 1991.
cell-surface receptor of HIV, represent some of the highly specific agents that were discussed. While these may act with high degrees of precision in vitro, the problem of administration and subsequent targeting of the proteins and peptide constructs to their sites of action in the whole organism provided the main thrust of the meeting. Language and other vehicles for deliver}" Participants were drawn from two main camps, the molecular manipuhtors and immunologists forming one rehtively homogeneous grouping, and drug targeters the other. Placed in close contact for 12 days, in lectures and the vital tutorial sessions, there was considerable intellectual cross-fertilization, but
© 1991, Elsevier Science PublishersLtd (UK) 0167 - 9430/91/$2.00
there were two almost distinct (sometimes coded) languages to be learned (as often happens in science), which hinders the facility of transitions between disciplines. It is essential that they do fuse and work together, as George Poste (SmithKline-Beecham, Philadelphia USA) pointed out forcibly, since progress in our ability to generate complex molecules has, he maintained, outstripped our capacity to develop suitable delivery systems to optimize their applicability. The greatest challenge is the development of systems for the delivery of autocrine/ paracrine molecules which act at extravascular sites, and to deliver a wider range of endo~nous mob ecules (such as gonadotropin) and their analogues in a manner which reflects the natural periodicity of delivery. Intravenous (IV) administration of autocrine/paracrine
meeting report
TIBTECHSEPTEMBER1991 (VOL9)
296
forum mediators results in the exposure of many tissues to these agents which they do not normally encounter. The resulting toxicities may be lifethreatening. Even if the IV route is the route of choice (as it can be for many agents that act in the blood compartment), the circulating half-life of many proteins with molecular masses greater than 40 kDa may be severely curtailed by their interaction with specific receptors, either for proteins (e.g. tPA, tissue type plasminogen activator), or for carbohydrate moieties, or complex formulations. Theo van Berkel (University of Leiden, The Netherlands) discussed strategies to prolong the presence of proteins in blood. This can be achieved by altering the physical properties of the protein, for example by covalent linkage of polyoxyethylene glycol molecules (-5 kDa) (Abraham Abuchowski [Enzon Inc., USA], Alec Sehon [University of Manitoba, Canada]), or, as in the case of tPA, pre-treatment with the protein (or low molecular-mass partial analogue) to block the receptors that are responsible for removal of that protein 1. Modification of proteins with hydrophilic polymers can render them tolerogenic 2. It can usually also lead to decreased biological activity, but this is thought to be compensated for by increased circulation lifetimes, thus maximizing the opportunity for uptake and interaction at the desired site. The exact correlation between biological activity and half-life does not appear to have been established.
Delivery by stealth Man-made carriers for proteins, such as liposomes and micropartides, invariably suffer fairly rapid loss in the reticuloendothelial system (ILl/S). The ILES may be a target in the treatment of leishmaniasis, other microbial diseases or certain carcinomas of the fiver, but if the target cells are elsewhere (e.g. in the blood or in extravascular tissues), then maintenance of the carrier systems in the circulation is of interest. Latest advances3 in the development of'long-fife' liposomes or extended half-life liposomes - the term 'stealth' has been trademarked - by incorporation into the lipid bilayers of liposomes of amphipathic polyoxyethylated derivatives or GM1 ganglioside were discussed by TIBTECHSEPTEMBER1991 (VOL9)
Alberto Gabizon (Hadassah Medical Organization, Jerusalem, Israel), and the marked reduction in liver sequestration of such liposomes and increased therapeutic efficiency was illustrated4. Manipulation of the fate of carriers, through control of lipo-: some diameter, bilayer fluidity and even flexibility, led to the re-statement of the fact that there is no such thing as 'the liposome'. Site-directed therapy is one goal of incorporating drugs in carriers such as immunoliposomes s (Leaf Huang, University of Tennessee, USA) possessing surface-oriented antibodies to adhere to tumour antigens. Frequendy the targets are extravascular. A still raging controversy is the question ofextravasation of both proteins and their carriers to target tissues. Phillip Thorpe (University of Texas, Southwestern Medical School, Dallas, USA) drew attention, not only to the possibility of the passage of delivery systems through the incomplete developing tumour vasculature, but also to the problems which might be encountered thereafter (e.g. the generally poor penetration .of immunotoxins; typically 0.001% per gram of tumour). Tumour-antigen heterogeneity and the fact that life-sustaining tissues also often express the target antigen will remain as formidable challenges to selective therapy. One alternative strategy is to target toxins to the tumour vasculature itselt~ it was applicable to many types of solid tumour and, as up to 1000 cells in the tumour are dependent on one endothelial cell, potentially efficient. Anti-fibrinectinreceptor antibody targets the basement membrane, and is therefore a candidate as a toxin delivery vehicle.
The importance of interactions In general, however, researchers involved in developing methods of toxin delivery were less buoyant than at previous meetings (e.g. the ASI in !989 on the same general theme). The maintenance of immunotoxin molecules in high concentrations in the circulation is essential to achieve appropriate levels of toxicity at the target. The concomitant toxicities, according to Ellen Vitetta (University of Texas, Southwestern Medical School, Dallas, USA), have to be coped with. In vitro, the molecular interactions exhibited by these molecules are exquisitely timed. Understanding
the nature of the interactions is of paramount importance (as an example, interactions between the CD4 molecules on the surface of cells and the envelope glycoprotein gp120 of HIV occur in vivo with drastic effects). The application 6 of this knowledge to active therapeutic ends, however, is often bedevilled by the complexity of the milieu in which the systems operate, and the vagaries of the pathway between administration site and target. Part of the ultimate solution is to design and produce smaller mob ecules which do not have the transport [imitations of the larger parent molecules but retain the specificity of action. Maurice Hofnung (Institut Pasteur, Paris, France) discussed hybrid bacterial envelope protein vectors designed 7 by altering 'permissive' sites and avoiding change to 'non-permissive' sites which can lead to the production of unstable, toxic or insoluble recombinant proteins. Therapeutic application of anti-lymphocyte monoclonal antibodies 8 produced in humanized form to reduce immunogenicity on repeated use, and antibodies as immunosuppressants and immunostimulators diverting T-cells to release cytokines and become cytotoxic were discussed by Herman Waldmann (New Addenbrookes Laboratories, Cambridge, UK).
Choosing a route Another approach to delivery of proteins and peptides is to explore routes of administration which can adventitiously avoid some of the problems of the IV route. The oral, rectal and nasal routes represent clinical alternatives for drug delivery. The oral route in particular has many attractions for chronic administration of proteins such as insulin, as Murray Saffran (Medical College of Ohio, USA) pointed out. Avoiding gastric destruction by coating capsules of insulin with an azo-polymer that is degraded by the bacterial flora of the colon, clinically useful responses were found even though the bioavailability per os was in the order of 1-2%. Alexander Florence (University of London, UK) presented further evidence of oral uptake of nanoparticles (potential carriers) by the M-ceil of Peyer's patches, site of uptake of antigens, macromolecules, bacteria and viral particles. Still a somewhat controversial subject, quantitative determination of a
297
forum polystyrene carrier showed that around 3% of the administered dose of 50 nm particles reached the liver, while 1% penetrated to the spleen 1°. Roger Ash (University of Bradford, UK), working with an unusual experimental model (fish) that is devoid of Peyer's patches, produced evidence 11 of uptake of somatotropim and other proteins by oral and rectal routes. Optimization of function of another group of peptides and proteins, the new-generation vaccines, is testing the wit of both camps referred to earlier. Most of the recombinant subunit and synthetic peptide vaccines are non- or poorly immunogenic but a number of emerging approaches (including the use of sophisticated immunological adjuvants) are now capable of proyoking potent immune responses to antigens. Anthony Allison (Syntex Research, Palo Alto, USA) described adjuvant folmulations such as a squahne Pluronic® co-polymer emulsion which is thought to act by targeting antigens to antigenpresenting cells n. Another system, liposomes, [discussed by Gregory Gregoriadis (University of London, UK)], has successfully been applied 13 with numerous bacterial,
viral, protozoan and tumour antigem. In addition, the great structural versatility of liposomes has been instrumental in their use in vaccines in conjunction with cytokines such as interleukin-2, with ligands which target antigen-presenting cells or even as a means to overcome genetic restriction of animals to mount an immune response to certain peptides. Nature has taken many millions of years to evolve the complex series of compartments that comprise the mammalian body. It is perhaps too much to expect, even inspired by the sight of the ancient Temple of Poseidon, that in the space of 12 days, we would have addressed all of the many problems of design, delivery and targeting of complex proteim. References 1 Rijken, D. C., Otter, M., Kuiper,J. and van Berkel,Th. J. C. (1990) Thromb. Res. Suppl. 49, 63-71 2 Takata, M., Maid, P. K., Kubo, R. T., Chen, Y., Holford-Stevens,V., Rector, E. and Sehon, A. H. (1990)J. Immunol. 145, 2846-2853 $ Gregoriadis,G. (1988)in 12posomesas Drug Canim : Reant
Trmds and
Progress,
(G~goriadis, G., ed.), pp. 3-18, John Wiley & Sons
4 Gabizon, A., Price, D., Huberty,J., Bresailer, IL and Papahadjopoulos,D. (1990) CancerRes. 50, 6371-6378 $ Mamyam, K., Kennel,S.J. and Huang,L. (1990) Pr0c. Natl Acad. SCi. USA 87, 5744-5748 6 Till, M. A., Ghede, V., May,R. D. Auerbach, P. C., Zolh-Pamer, S., Gomy, M. K., Gregory,T., Uhr,J. W. and Vitetta,E. S. (1990)2.aDS 3, 609-614 7 Lederc, C., Mag~ean, P., van der Weft, S., Deriand, E., Duphy, P. and Hofnang, M. (1990).].lmmunol. 144,3174-3182 8 Waldmann,H. (1989)Annu. Rev. lmmunol. 7, 407-444
9 Saffran,M., Kumar,G. S., Neckers,D. C., Peria, J., Jones, R. H, and Field, J. B. (1990) Biochem. Soc. Trans. 18, 752-754 10 Jani, p. U., Halbert, G. W., Langridge,J. and Florence,A. T. (1990)J. Pharm. Pharmacol. 42, 821-826 11 McLean, E., Ash, IL and Westcott, P. A. B. (1989)Aquaculture79, 411-415 12 Byars, N. E., Allison, A. C., Ham.an, M. W. and Kendall,A. P. (1990) Vaccine5, 223-228
13 Gregoriadis,G. (1990) lmmunol. TodaIt 11, 89-97
Alexander T. Florence Gregory Gregoriadis Centrefor Drag Delivery Research.~..e School of Pharmacy, University of London, London W C I N IAX, UK.
Biotechnologyand sustainable development in the Third World A recent international public debate on 'Biotechnology and Farmers' Rights; Opportunities and Threats for Small-Scale Farmers in Developing Countries'* has hig~ighted the importance oi'biotecimc!cgy in meeting the challenges of sustainable rural devdopment in the Third World. Current biotechnological developments are more likely to threaten than to support sustainable rural development in the Third World. *The debate was organized by the Department of Biology and Society (Vrije Universiteit Amsterdam) and the Netherlands Organization for International Development and Cooperation (NOVIB) and held 8-9 April 1991, at the University of Amsterdam, The Netherlands.
Market forces direct the agricultural research agendas o f private companies and o f public research institutes with emphasis on industrial appfications and capitalintense, well-controlled large-scale farming systems and the substitution o f agricultural raw products. Furthermore, the increasing influence of biotechnology in plant breeding is resulting in the introduction of procedures often requiring high levels o f investment and which are directed at developing new, patentable varieties of crops. These patents would enable plant breeders in developed countries to obtain property rights to genetic resources which have become available as a result o f the efforts of local communities in developing countries who have
(~) 1991, ElsevierScience PublishersLtd (UK) 0167-9430/91152.00
maintained and developed local varieties of crops for centuries. The one-sided direction of current biotechnological research is not inherent to the technology itself, The starting point for the recent public debate was the assumption that current biotechnological research does have the potential to yield interesting and beneficial results for small-scale farmers in developing countries. Moreover, the organizers o f the debate assumed that small-scale farmers in developing countries have as much right to technologies suitable for them as their large-scale colleagues. So far, virtually no effort has been made to address the threats to the poorest farmers of the Third World. Opportunities to do so have scarcely been examined, let alone realized. The discussion
meeting report
TIBTECHSEPTEMBER1991 (VOL9)
