2516. Persistence of Anti-HIV Antibodies in HIV-1-infected Patients on Combination Antiretroviral Therapy (cART) with Prolonged Viral Suppression

Abstract Background Despite years of cART with sustained HIV-RNA plasma viral load (pVL) < 50 copies/mL, antibodies (Abs) to HIV-1 proteins persist. The reasons for this are unknown but may reflect long-lived B cell responses and/or persistence of antigen. To address which of these may be the case, we compared decay rates of anti-HIV Abs to those of anti-Measles Abs. Methods A cohort of 10 HIV-infected patients on cART with pVL < 50 (average 3 years, range 0–7.1 years) were studied. Baseline and 5-year follow-up serum were collected and assessed for anti-HIV-1 Abs via western blot (Cambridge Biotech WB kit), with additional densiometric analysis used for quantitative calculation of a western blot “score” that was normalized to control specimens. The kinetics of measles Abs titers over the same 5-year period were also analyzed by the quantitative Serion Measles IgG ELISA kit, given a history of prior vaccination in these participants. McNemar’s and paired t-tests were used for analysis. Results All 10 patients exhibited persistence of anti-HIV-1 Abs at ≥ 5 year follow-up as determined by persistence of ≥ 2 diagnostic bands on WB (P = 0.003). The patterns for all 10 participants varied individually by patient with each exhibiting a unique profile (representative figure); 7/10 patients had WBs that could be analyzed quantitatively and showed no significant change over the study period (average baseline score 5.9 vs 5.3 at follow-up, P = 0.26). 7/9 patients had valid measles IgG measurements showing a consistent but nonsignificant decline over the same 5-year study period (measles titer 55–2800 mIU/mL at baseline vs 50–1300 mIU/mL at follow-up, n = 9, P = 0.18). Conclusion The mechanism leading to the persistence of anti-HIV-1 Abs in HIV-infected individuals with prolonged viral suppression has been unclear. The general decline in anti-Measles IgG titer over the 5-year observational period in 7/9 patients is likely to be explained by waning B cell-mediated humoral immunity in these vaccinated individuals and consistent with their lack of ongoing exposure to this pathogen. The persistence of anti-HIV-1 Abs over the same 5-year period, on the other hand, may indicate persistent HIV-1 viral protein production either from active reservoirs or by transcription of “defective” HIV-1 proviruses as recently reported. Disclosures All authors: No reported disclosures.