AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 1 of 11
1
Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy
Kelly A. Curtis*, Krystin Ambrose Price, Philip Niedzwiedz, Silvina Masciotra, and Michele Owen
Laboratory Branch, Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
Running Title: Effects of ART on HIV Incidence Assays
*Corresponding author: Centers for Disease Control and Prevention 1600 Clifton Rd. NE, MS-A25 Atlanta, GA 30333 Phone: 404-639-1002 Fax: 404-718-2159 Email: [email protected]
1
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 2 of 11
2
Abstract The effects of antiretroviral therapy (ART) on the performance of HIV incidence assays have been well-documented. In order to improve upon current assay approaches or focus the development of future assays, studies are needed to characterize the effects of ART on all candidate HIV incidence assays. In this study, we compared the performance of three antibody avidity-based HIV incidence assays, the LAg, Bio-Rad Avidity, and HIV-1 Multiplex assays, using a well-defined cohort of recent HIV-1 seroconverters composed of ART-naïve HIV-1-infected individuals and those who received ART early or delayed in the course of infection. Differences in the performance of all three avidity-based incidence assays were noted with study subjects who received ART. The LAg assay and Multiplex total antibody measurements (nMFI) exhibited similar kinetics in reactivity, as these assays tended to fluctuate with changes in viral load. In the early ART group, all 7 subjects remained recent by both assays at time points >1 year post-seroconversion, and assay values declined dramatically post-delayed ART initiation. In contrast, the two-well, antibody-dissociation avidity assays, Bio-Rad Avidity and Multiplex avidity index measurements, continued to mature in the early ART group, though blunted relative to the ART naïve group, and assay values remained stable after delayed ART initiation. In summary, although the HIV incidence assays evaluated in this study are all designed to measure antibody avidity, each assay is affected differently by ART-induced virus suppression, presumably due to the distinct assay formats and procedures for measuring avidity.
2
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 3 of 11
3 HIV incidence, the rate of new infections in a given population, provides crucial information regarding the status of HIV/AIDS epidemic, including the efficacy of HIV prevention measures and identification of high-risk cohorts. Estimation of HIV incidence from cross-sectional surveys, as opposed to repeat testing of longitudinal cohorts for seroconversion, has been made possible since the inception of HIV incidence assays.1 Due to the numerous immunological and virological changes that occur in an individual post-infection, HIV incidence assays are designed to measure a specific biomarker(s) that distinguishes recent from established or long-term infection. The most widely evaluated methods have involved the measurement of serologic responses to HIV, mainly HIV antibody titer or antibody avidity.2-8 All serology-based HIV incidence assays are subject to some degree of misclassification, typically due to innate immune variation, differences in HIV-1 subtypes, and prolonged use of antiretroviral therapy (ART).9 To date, we have limited knowledge of the dynamics of HIV incidence assay performance in the presence of ART and whether virus suppression alone is responsible for increased false-recent rates (FRRs). Studies are also needed to elucidate the specific effects of ART initiation and viral load (VL) suppression on the immunologic parameters measured by HIV incidence assays and to determine if different assay approaches are affected in distinct ways. In this study, we compared the performance of three HIV incidence assays, the HIV-1 Limiting Antigen (LAg)-Avidity EIA (Sedia Biosciences Corp.; Maxim Biomedical, Inc., Rockville, MD), Bio-Rad Avidity, 6 and HIV-1 Multiplex assays, 7 using a well-defined cohort of recent HIV-1 seroconverters. The cohort is composed of HIV-1-infected individuals who fall into one of three groups: ART naïve, early initiation of ART, and delayed initiation of ART. The effects of ART use on the performance of these assays were assessed in relation to viral load. Longitudinal HIV seroconversion panels were collected as part of the Seroconversion Incidence Panel Project (SIPP) in collaboration with SeraCare Life Sciences, Inc. (Milford, MA). The specimen 3
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 4 of 11
4 10
collection protocol and characteristics of the cohort have been described in detail elsewhere.
The
cohort consists of specimens from 19 HIV-1 recent seroconverters, with total follow-up time ranging from 189 to 989 days (median= 699 days). According to medical records, seven subjects (76 specimens) were ART naïve during the entire sample collection period, seven subjects (82 specimens) received ART within the first six months of seroconversion (“early ART”; median= 64.5 days), and five subjects (60 specimens) initiated ART > 6 months post-seroconversion (“delayed ART”; median= 488.5 days). An estimated date of seroconversion was defined as the midpoint between the last negative HIV antibody test and first positive antibody test. The Sedia HIV-1 LAg-Avidity EIA was performed according to the manufacturer’s instructions (Sedia Biosciences Corporation, Portland, Oregon). All specimens with a normalized optical density (ODn) ≤ 2.0 were subjected to confirmatory testing. Specimens that yielded an ODn ≤ 1.5 during the confirmatory testing were considered recent infections. The Bio-Rad Avidity assay is based on the Genetic Systems HIV-1/HIV-2 PLUS O EIA (Bio-Rad Laboratories, Hercules, CA), with a few modifications for the measurement of antibody avidity.6 All specimens with an AI of 20-50% were subjected to confirmatory testing in duplicate. For specimens that required confirmatory testing, the final interpretation was determined by the mean of the duplicate results. Specimens that yielded a final AI ≤30% were considered recent. The HIV-1 Bio-Plex assay is based on the Bio-Rad Bio-Plex Multiplex System and has been described previously.7 Cutoff values for each analyte were calculated as previously described, using an HIV-1 Incidence/Prevalence Performance Panel (SeraCareLife Sciences).10 All specimens with assay values below the cutoff were considered recent. The cutoff values are as follows: gp120n= 4.2, gp160n= 3.1, gp120a= 24.9%, gp160a= 31.8%, gp41a= 31.8%. The viral load for each specimen in the SIPP cohort was quantitated using the COBAS AmpliPrep/COBAS TaqMan® HIV-1 Test, v2.0 (Roche Molecular Diagnostics, Pleasanton, CA), according to the manufacturer’s instructions. 4
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 5 of 11
5 Longitudinal reactivity over days since seroconversion is shown in Figure 1 for the LAg, BioRad Avidity, and HIV Multiplex assays (gp120n, gp160n, gp120a, gp160a, and gp41a). All of the seven subjects who received early ART were virally suppressed or had undetectable viral loads within 1 year post-seroconversion (data not shown). The LAg assay exhibited a similar pattern of reactivity, or little to no antibody maturation, as the Multiplex analytes gp120n and gp160n, which are measures of total antigen-specific antibody as opposed to antibody avidity. Surprisingly, avidity index, as measured by the Bio-Rad Avidity and Multiplex assays, continued to develop in absence of detectable viral load, though the maturation curve was blunted relative to the ART naïve group. One subject exhibited a viral breakthrough of 100,000 copies/ mL at 390 days, which coincided with a sharp increase in the LAg ODn that returned to pre-breakthrough levels after the viral load declined. For this subject, an increase in assay values could also be observed for gp120n, gp160n, and gp41a, but to a much lesser extent. In the late ART group, the LAg assay and Multiplex nMFI (direct antibody binding) measurements began to decline shortly after ART initiation, whereas the assays that measure avidity index remained relatively stable after ART initiation (Supplemental Figure 1). One subject in the delayed ART group exhibited virus suppression approximately one year prior to documented ART use, which was reflected by the lack of or attenuated antibody maturation observed with all of the incidence assays. It is suspected that this particular individual was receiving ART earlier than reported. Initiation of ART early in the course of HIV infection is associated with a greater impact on the FRR of HIV incidence assays, presumably since virus suppression reduces or eliminates the antigenic stimulation necessary for antibody maturation during early infection. The data presented here support this conclusion for all assays evaluated. Since the LAg, Bio-Rad Avidity, and Multiplex assays are all designed to measure antibody avidity, the differences in assay performance may be explained by the distinct chemistries or test formats. For the LAg assay, the recombinant gp41 protein (rIDR-M) is “limited” on the surface of the test plate to promote binding of high avidity antibodies to the antigen.4 5
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 6 of 11
6 The assay protocol entails a single-well measurement; therefore, it is likely that the assay is measuring the amount of high avidity antibodies that bind to the antigen. Alternatively, the Bio-Rad Avidity and Multiplex assays involve a dual-well measurement, which includes a reference well and a “treatment” well for the dissociative agent. Avidity index is expressed as a ratio of these two measurements or the percentage of antibody dissociation. During early HIV infection, avidity maturation in the absence of detectable viral load may be the result of low levels of antigenic stimulation occurring at local sites, even though total antibody levels in the blood remain low or undetectable. One major limitation of the current study is the small number of subjects included in each study group. The cohort was also obtained from a US study, therefore all study participants were likely infected with subtype B HIV. Further studies are needed to address whether similar effects in assay performance will occur in cases where ART is not fully suppressive and to determine if specific viral load levels can be identified that correspond to changes in assay performance.
6
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 7 of 11
7 Author Disclosure Statement: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
Please address reprint requests to: Kelly Curtis Centers for Disease Control and Prevention 1600 Clifton Rd. NE, MS-A25 Atlanta, GA 30329 [email protected]
7
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 8 of 11
8
References
1.
2.
3. 4.
5.
6.
7.
8.
9. 10.
Janssen RS, Satten GA, Stramer SL, et al. New testing strategy to detect early HIV-1 infection for use in incidence estimates and for clinical and prevention purposes. JAMA. Jul 1 1998;280(1):42-48. Parekh BS, Kennedy MS, Dobbs T, et al. Quantitative detection of increasing HIV type 1 antibodies after seroconversion: a simple assay for detecting recent HIV infection and estimating incidence. AIDS Res Hum Retroviruses. Mar 1 2002;18(4):295-307. Suligoi B, Massi M, Galli C, et al. Identifying recent HIV infections using the avidity index and an automated enzyme immunoassay. J Acquir Immune Defic Syndr. Apr 1 2003;32(4):424-428. Wei X, Liu X, Dobbs T, et al. Development of two avidity-based assays to detect recent HIV type 1 seroconversion using a multisubtype gp41 recombinant protein. AIDS Res Hum Retroviruses. Jan 2010;26(1):61-71. Rawal BD, Degula A, Lebedeva L, et al. Development of a new less-sensitive enzyme immunoassay for detection of early HIV-1 infection. J Acquir Immune Defic Syndr. Jul 1 2003;33(3):349-355. Hauser A, Santos-Hoevener C, Meixenberger K, et al. Improved testing of recent HIV-1 infections with the BioRad avidity assay compared to the limiting antigen avidity assay and BED Capture enzyme immunoassay: evaluation using reference sample panels from the German Seroconverter Cohort. PLoS One. 2014;9(6):e98038. Curtis KA, Kennedy MS, Charurat M, et al. Development and characterization of a bead-based, multiplex assay for estimation of recent HIV type 1 infection. AIDS Res Hum Retroviruses. Feb 2012;28(2):188-197. Keating SM, Hanson D, Lebedeva M, et al. Lower-sensitivity and avidity modifications of the vitros anti-HIV 1+2 assay for detection of recent HIV infections and incidence estimation. J Clin Microbiol. Dec 2012;50(12):3968-3976. Incidence Assay Critical Path Working G. More and better information to tackle HIV epidemics: towards improved HIV incidence assays. PLoS Med. Jun 2011;8(6):e1001045. Curtis KA, Ambrose KM, Kennedy MS, Owen SM. Evaluation of dried blood spots with a multiplex assay for measuring recent HIV-1 infection. PLoS One. 2014;9(9):e107153.
Figures
8
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 9 of 11
9 Figure 1. The effect of early ART on LAg, Bio-Rad Avidity, and Multiplex assay performance. Assay values for each subject are plotted over days since seroconversion for 7 ART naïve (black lines) and 7 early ART (red lines) subjects. Each circle represents an individual time point. The horizontal black line denotes the cutoff value for each assay.
9
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 10 of 11
10
Supplemental Figure 1. The effects of delayed ART on assay performance and viral load. Subject IDs are noted on the top of each graph. Assay values are plotted on the left vertical axis (black lines) and viral load is plotted on the right vertical axis (red lines). For BioPlex AI, the following analytes are represented: gp120a (closed circles), gp160a (open circles), and gp41a (triangles). For BioPlex nMFI, the following analytes are displayed: gp120n (closed circles) and gp160n (open circles). Open red circles indicate the first longitudinal specimen where ART use was documented.
10
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof. Page 11 of 11
11
11
Page 1 of 11
1
Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy
Kelly A. Curtis*, Krystin Ambrose Price, Philip Niedzwiedz, Silvina Masciotra, and Michele Owen
Laboratory Branch, Division of HIV/AIDS Prevention, National Center for HIV/AIDS, Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA
Running Title: Effects of ART on HIV Incidence Assays
*Corresponding author: Centers for Disease Control and Prevention 1600 Clifton Rd. NE, MS-A25 Atlanta, GA 30333 Phone: 404-639-1002 Fax: 404-718-2159 Email: [email protected]
1
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 2 of 11
2
Abstract The effects of antiretroviral therapy (ART) on the performance of HIV incidence assays have been well-documented. In order to improve upon current assay approaches or focus the development of future assays, studies are needed to characterize the effects of ART on all candidate HIV incidence assays. In this study, we compared the performance of three antibody avidity-based HIV incidence assays, the LAg, Bio-Rad Avidity, and HIV-1 Multiplex assays, using a well-defined cohort of recent HIV-1 seroconverters composed of ART-naïve HIV-1-infected individuals and those who received ART early or delayed in the course of infection. Differences in the performance of all three avidity-based incidence assays were noted with study subjects who received ART. The LAg assay and Multiplex total antibody measurements (nMFI) exhibited similar kinetics in reactivity, as these assays tended to fluctuate with changes in viral load. In the early ART group, all 7 subjects remained recent by both assays at time points >1 year post-seroconversion, and assay values declined dramatically post-delayed ART initiation. In contrast, the two-well, antibody-dissociation avidity assays, Bio-Rad Avidity and Multiplex avidity index measurements, continued to mature in the early ART group, though blunted relative to the ART naïve group, and assay values remained stable after delayed ART initiation. In summary, although the HIV incidence assays evaluated in this study are all designed to measure antibody avidity, each assay is affected differently by ART-induced virus suppression, presumably due to the distinct assay formats and procedures for measuring avidity.
2
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 3 of 11
3 HIV incidence, the rate of new infections in a given population, provides crucial information regarding the status of HIV/AIDS epidemic, including the efficacy of HIV prevention measures and identification of high-risk cohorts. Estimation of HIV incidence from cross-sectional surveys, as opposed to repeat testing of longitudinal cohorts for seroconversion, has been made possible since the inception of HIV incidence assays.1 Due to the numerous immunological and virological changes that occur in an individual post-infection, HIV incidence assays are designed to measure a specific biomarker(s) that distinguishes recent from established or long-term infection. The most widely evaluated methods have involved the measurement of serologic responses to HIV, mainly HIV antibody titer or antibody avidity.2-8 All serology-based HIV incidence assays are subject to some degree of misclassification, typically due to innate immune variation, differences in HIV-1 subtypes, and prolonged use of antiretroviral therapy (ART).9 To date, we have limited knowledge of the dynamics of HIV incidence assay performance in the presence of ART and whether virus suppression alone is responsible for increased false-recent rates (FRRs). Studies are also needed to elucidate the specific effects of ART initiation and viral load (VL) suppression on the immunologic parameters measured by HIV incidence assays and to determine if different assay approaches are affected in distinct ways. In this study, we compared the performance of three HIV incidence assays, the HIV-1 Limiting Antigen (LAg)-Avidity EIA (Sedia Biosciences Corp.; Maxim Biomedical, Inc., Rockville, MD), Bio-Rad Avidity, 6 and HIV-1 Multiplex assays, 7 using a well-defined cohort of recent HIV-1 seroconverters. The cohort is composed of HIV-1-infected individuals who fall into one of three groups: ART naïve, early initiation of ART, and delayed initiation of ART. The effects of ART use on the performance of these assays were assessed in relation to viral load. Longitudinal HIV seroconversion panels were collected as part of the Seroconversion Incidence Panel Project (SIPP) in collaboration with SeraCare Life Sciences, Inc. (Milford, MA). The specimen 3
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 4 of 11
4 10
collection protocol and characteristics of the cohort have been described in detail elsewhere.
The
cohort consists of specimens from 19 HIV-1 recent seroconverters, with total follow-up time ranging from 189 to 989 days (median= 699 days). According to medical records, seven subjects (76 specimens) were ART naïve during the entire sample collection period, seven subjects (82 specimens) received ART within the first six months of seroconversion (“early ART”; median= 64.5 days), and five subjects (60 specimens) initiated ART > 6 months post-seroconversion (“delayed ART”; median= 488.5 days). An estimated date of seroconversion was defined as the midpoint between the last negative HIV antibody test and first positive antibody test. The Sedia HIV-1 LAg-Avidity EIA was performed according to the manufacturer’s instructions (Sedia Biosciences Corporation, Portland, Oregon). All specimens with a normalized optical density (ODn) ≤ 2.0 were subjected to confirmatory testing. Specimens that yielded an ODn ≤ 1.5 during the confirmatory testing were considered recent infections. The Bio-Rad Avidity assay is based on the Genetic Systems HIV-1/HIV-2 PLUS O EIA (Bio-Rad Laboratories, Hercules, CA), with a few modifications for the measurement of antibody avidity.6 All specimens with an AI of 20-50% were subjected to confirmatory testing in duplicate. For specimens that required confirmatory testing, the final interpretation was determined by the mean of the duplicate results. Specimens that yielded a final AI ≤30% were considered recent. The HIV-1 Bio-Plex assay is based on the Bio-Rad Bio-Plex Multiplex System and has been described previously.7 Cutoff values for each analyte were calculated as previously described, using an HIV-1 Incidence/Prevalence Performance Panel (SeraCareLife Sciences).10 All specimens with assay values below the cutoff were considered recent. The cutoff values are as follows: gp120n= 4.2, gp160n= 3.1, gp120a= 24.9%, gp160a= 31.8%, gp41a= 31.8%. The viral load for each specimen in the SIPP cohort was quantitated using the COBAS AmpliPrep/COBAS TaqMan® HIV-1 Test, v2.0 (Roche Molecular Diagnostics, Pleasanton, CA), according to the manufacturer’s instructions. 4
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 5 of 11
5 Longitudinal reactivity over days since seroconversion is shown in Figure 1 for the LAg, BioRad Avidity, and HIV Multiplex assays (gp120n, gp160n, gp120a, gp160a, and gp41a). All of the seven subjects who received early ART were virally suppressed or had undetectable viral loads within 1 year post-seroconversion (data not shown). The LAg assay exhibited a similar pattern of reactivity, or little to no antibody maturation, as the Multiplex analytes gp120n and gp160n, which are measures of total antigen-specific antibody as opposed to antibody avidity. Surprisingly, avidity index, as measured by the Bio-Rad Avidity and Multiplex assays, continued to develop in absence of detectable viral load, though the maturation curve was blunted relative to the ART naïve group. One subject exhibited a viral breakthrough of 100,000 copies/ mL at 390 days, which coincided with a sharp increase in the LAg ODn that returned to pre-breakthrough levels after the viral load declined. For this subject, an increase in assay values could also be observed for gp120n, gp160n, and gp41a, but to a much lesser extent. In the late ART group, the LAg assay and Multiplex nMFI (direct antibody binding) measurements began to decline shortly after ART initiation, whereas the assays that measure avidity index remained relatively stable after ART initiation (Supplemental Figure 1). One subject in the delayed ART group exhibited virus suppression approximately one year prior to documented ART use, which was reflected by the lack of or attenuated antibody maturation observed with all of the incidence assays. It is suspected that this particular individual was receiving ART earlier than reported. Initiation of ART early in the course of HIV infection is associated with a greater impact on the FRR of HIV incidence assays, presumably since virus suppression reduces or eliminates the antigenic stimulation necessary for antibody maturation during early infection. The data presented here support this conclusion for all assays evaluated. Since the LAg, Bio-Rad Avidity, and Multiplex assays are all designed to measure antibody avidity, the differences in assay performance may be explained by the distinct chemistries or test formats. For the LAg assay, the recombinant gp41 protein (rIDR-M) is “limited” on the surface of the test plate to promote binding of high avidity antibodies to the antigen.4 5
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 6 of 11
6 The assay protocol entails a single-well measurement; therefore, it is likely that the assay is measuring the amount of high avidity antibodies that bind to the antigen. Alternatively, the Bio-Rad Avidity and Multiplex assays involve a dual-well measurement, which includes a reference well and a “treatment” well for the dissociative agent. Avidity index is expressed as a ratio of these two measurements or the percentage of antibody dissociation. During early HIV infection, avidity maturation in the absence of detectable viral load may be the result of low levels of antigenic stimulation occurring at local sites, even though total antibody levels in the blood remain low or undetectable. One major limitation of the current study is the small number of subjects included in each study group. The cohort was also obtained from a US study, therefore all study participants were likely infected with subtype B HIV. Further studies are needed to address whether similar effects in assay performance will occur in cases where ART is not fully suppressive and to determine if specific viral load levels can be identified that correspond to changes in assay performance.
6
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 7 of 11
7 Author Disclosure Statement: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.
Please address reprint requests to: Kelly Curtis Centers for Disease Control and Prevention 1600 Clifton Rd. NE, MS-A25 Atlanta, GA 30329 [email protected]
7
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 8 of 11
8
References
1.
2.
3. 4.
5.
6.
7.
8.
9. 10.
Janssen RS, Satten GA, Stramer SL, et al. New testing strategy to detect early HIV-1 infection for use in incidence estimates and for clinical and prevention purposes. JAMA. Jul 1 1998;280(1):42-48. Parekh BS, Kennedy MS, Dobbs T, et al. Quantitative detection of increasing HIV type 1 antibodies after seroconversion: a simple assay for detecting recent HIV infection and estimating incidence. AIDS Res Hum Retroviruses. Mar 1 2002;18(4):295-307. Suligoi B, Massi M, Galli C, et al. Identifying recent HIV infections using the avidity index and an automated enzyme immunoassay. J Acquir Immune Defic Syndr. Apr 1 2003;32(4):424-428. Wei X, Liu X, Dobbs T, et al. Development of two avidity-based assays to detect recent HIV type 1 seroconversion using a multisubtype gp41 recombinant protein. AIDS Res Hum Retroviruses. Jan 2010;26(1):61-71. Rawal BD, Degula A, Lebedeva L, et al. Development of a new less-sensitive enzyme immunoassay for detection of early HIV-1 infection. J Acquir Immune Defic Syndr. Jul 1 2003;33(3):349-355. Hauser A, Santos-Hoevener C, Meixenberger K, et al. Improved testing of recent HIV-1 infections with the BioRad avidity assay compared to the limiting antigen avidity assay and BED Capture enzyme immunoassay: evaluation using reference sample panels from the German Seroconverter Cohort. PLoS One. 2014;9(6):e98038. Curtis KA, Kennedy MS, Charurat M, et al. Development and characterization of a bead-based, multiplex assay for estimation of recent HIV type 1 infection. AIDS Res Hum Retroviruses. Feb 2012;28(2):188-197. Keating SM, Hanson D, Lebedeva M, et al. Lower-sensitivity and avidity modifications of the vitros anti-HIV 1+2 assay for detection of recent HIV infections and incidence estimation. J Clin Microbiol. Dec 2012;50(12):3968-3976. Incidence Assay Critical Path Working G. More and better information to tackle HIV epidemics: towards improved HIV incidence assays. PLoS Med. Jun 2011;8(6):e1001045. Curtis KA, Ambrose KM, Kennedy MS, Owen SM. Evaluation of dried blood spots with a multiplex assay for measuring recent HIV-1 infection. PLoS One. 2014;9(9):e107153.
Figures
8
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 9 of 11
9 Figure 1. The effect of early ART on LAg, Bio-Rad Avidity, and Multiplex assay performance. Assay values for each subject are plotted over days since seroconversion for 7 ART naïve (black lines) and 7 early ART (red lines) subjects. Each circle represents an individual time point. The horizontal black line denotes the cutoff value for each assay.
9
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof.
Page 10 of 11
10
Supplemental Figure 1. The effects of delayed ART on assay performance and viral load. Subject IDs are noted on the top of each graph. Assay values are plotted on the left vertical axis (black lines) and viral load is plotted on the right vertical axis (red lines). For BioPlex AI, the following analytes are represented: gp120a (closed circles), gp160a (open circles), and gp41a (triangles). For BioPlex nMFI, the following analytes are displayed: gp120n (closed circles) and gp160n (open circles). Open red circles indicate the first longitudinal specimen where ART use was documented.
10
AIDS Research and Human Retroviruses Persistence of HIV Antibody Avidity in the Presence of Antiretroviral Therapy (doi: 10.1089/AID.2015.0247) This article has been peer-reviewed and accepted for publication, but has yet to undergo copyediting and proof correction. The final published version may differ from this proof. Page 11 of 11
11
11
