Towards Novel HIV-1 Serodiagnostic Tests without Vaccine-Induced Seroreactivity

Abstract

Vaccine-induced seroreactivity/positivity (VISR/P) poses a significant and common challenge to HIV vaccine implementation, as up to 95% of vaccine recipients may be misclassified as having HIV infection by current HIV screening and confirmatory serological assays. We investigated whether internal HIV proteins could be used to overcome VISR and discovered a set of 4 antigens (gp41 endodomain, p31 integrase, p17 matrix protein, and Nef) that are recognized by antibodies produced in individuals with HIV infection but not in vaccinated individuals. When evaluated in a multiplex double-antigen bridging ELISA, this antigen combination had specificities of 98.1% prevaccination and 97.1% postvaccination, demonstrating the assay is minimally impacted by vaccine-induced antibodies. The sensitivity was 98.5%, further increasing to 99.7% when p24 antigen testing was included. Results were similar across HIV-1 clades. Although more technical advancements will be desired, this research provides the groundwork for the development of new fourth-generation HIV tests unaffected by VISR. IMPORTANCE While the detection of HIV infection is accomplished by several methods, the most common are serological tests that detect host antibodies produced in response to viral infection. However, the use of current serological tests may present a significant challenge to the adoption of an HIV vaccine in the future because the antibodies to HIV antigens detected in currently available tests also tend to be included as antigens in the HIV vaccines in development. The use of these serological tests may thus result in the misclassification of vaccinated HIV-negative individuals, which can have potential for significant harms for individuals and could prevent the widespread adoption and implementation of HIV vaccines. Our study aimed to identify and evaluate target antigens for inclusion in new serological tests that can be used to identify HIV infections without interference from vaccine-induced antibodies but also fit within existing platforms for HIV diagnostics.

Keywords: antigens; diagnostics; human immunodeficiency virus; seroreactivity; vaccine.

FIG 1

Evaluation and performance of individual HIV-1 candidate antigens. (a) Structure of HIV indicating polypeptide antigens that were tested. (b) Immune response to each polypeptide antigen in individuals living with known HIV-1 infection and those who participated in HIV vaccine studies. (c) Heat maps of serological assays for the identification of antigens. Samples shaded gray were below the cutoff 0.1 μg/mL for gp41e and PR, 0.7 μg/mL for p31, 0.25 μg/mL for p17, 0.9 μg/mL for Nef, 0.1 U/mL for RT, 0.3 μg/mL for p55, and 0 μg/mL for p15. (d) Performance evaluation of individual HIV-1 candidate antigens. Sensitivity of each polypeptide antigen to detect infection in treatment-naive individuals living with known HIV-1 infection (AMBER, n = 600). The specificity of each antigen was evaluated in individuals who participated in HIV vaccine studies (TRAVERSE and ASCENT, n = 109). Dotted horizontal lines represent the threshold for positivity (0.176). (e) Venn diagram sensitivities for different combinations of indirect ELISA. gp41e, glycoprotein 41 endodomain; PLWH, people living with HIV; PR, protease; RT, reverse transcriptase.

FIG 2

Performance evaluation of the DHIVAx assay. (a) Overall performance of the DHIVAx assay. Sensitivity of each polypeptide antigen to detect infection in treatment-naive individuals living with known HIV-1 infection (AMBER, n = 600). Samples were initially tested 4-fold diluted (green circles) and all samples with blank-corrected Abs_450nm were retested undiluted (blue circles). Samples with a positive p24 antigen detection test are indicated as closed blue circles. The specificity of each antigen was evaluated in individuals who participated in HIV vaccine studies (TRAVERSE and ASCENT, n = 109). Dotted horizontal line represents the threshold for positivity (0.176). (b) Sensitivity by HIV-1 clade. (c) Sensitivity by time since diagnosis. (d) Performance of the DHIVAx assay in the World Health Organization HIV specimen evaluation panel. Dotted horizontal line represents the threshold for positivity (0.176). PLWH, people living with HIV.

FIG 3

Performance of DHIVAx assay in seroconversion panels, including p24 antigen data and 2 reference tests. Dotted horizontal lines represent the thresholds for positivity for the DHIVAx assay (0.176; left y axis) and DHIVAx assay with p24 antigen detection (1.0; right y axis).

FIG 4

Assessment of DHIVAx assay in longitudinal follow-up samples collected from individuals with known HIV infection. Dotted horizontal line represents the threshold for positivity (0.176).