Short Communication: Ultrasensitive Immunoassay for Assessing Residual Simian-Tropic HIV (stHIV) in Non-Human Primate Models of AIDS

Persistence of replication competent viral reservoirs during infection remains a barrier to HIV cure, despite the ability of combination antiretroviral therapy (cART) to effectively suppress viral replication. Simian-tropic human immunodeficiency virus (stHIV) is a minimally chimeric HIV-1 that is comprised of 94% HIV-1 sequence, contains HIV-1 drug and immunologic targets, and is capable of replicating to high levels and causing authentic HIV-like pathogenesis leading to clinical AIDS in pigtail macaques. Suppression of stHIV replication by cART provides a model for study of viral reservoirs and HIV-specific intervention strategies targeting them. Accurate measurement of reservoir size is crucial for evaluating the effect of any such intervention strategies. While there are a variety of assays which allow for indirect monitoring of viral reservoir size ex vivo, they each quantify a different aspect of viral reservoirs, and are characterized by conceptual and/or technical limitations. Measurement of viral protein in ex vivo cell culture assays captures the immunologically relevant viral-antigen producing component of the reservoir. This work demonstrates the utility of an ultrasensitive digital HIV Gag p24 immunoassay, which enabled earlier, and more sensitive detection of viral protein in culture supernatants from stimulated CD4+ T cells from stHIV infected pigtail macaques receiving cART compared to conventional enzyme-linked immunosorbent assays (ELISA). Protein measurements were highly correlated with cell free stHIV RNA, as measured by quantitative reverse transcription PCR. This ultrasensitive p24 assay can be used to complement other reservoir measurement tools to assess ongoing replication and reactivation of infectious virus from reservoirs in stHIV-infected pigtail macaques.

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