Understanding The Myeloid HIV Reservoir In HIV-Associated Neurological Disorder During Antiretroviral-Treated HIV Infection

Abstract

Background: Despite effective antiretroviral therapy (ART), the persistence of latent HIV that produce replication-competent virus remains a major barrier to a cure. Since the development of the quantitative viral outgrowth assay (QVOA) over 20 years ago, there has been significant advancements in the detection and quantification of the replication-competent reservoir. However, the original development and ongoing modifications of the QVOA remains mostly T cell-centric. Recent studies have shown compelling evidence that the myeloid compartment harbor HIV in the setting of ART in tissues, yet only a few studies were tailored to measure myeloid-derived replication-competent HIV in circulation in humans. In addition, the myeloid compartment is reported to play an important mechanistic role in the neuropathogenesis of HIV-associated neurological dysfunction, though it remains unclear whether HIV reservoirs that may be persistent in myeloid cells in the setting of suppressive ART are related to neurocognitive impairment. Methods: We obtained cryopreserved peripheral blood mononuclear cells from chronic HIV-infected individuals on long term ART (>5 years) (n=16) and those who initiated ART early during acute infection and remained aviremic for 2 years (n=8), all of whom had available age and education-adjusted neuropsychological testing scores. Cells were sorted to ultra-high purity by flow-cytometry for total monocytes and CD4 T cells and validated. Using a modified novel Monocyte TZM-bl Assay (TZA), (MoCo-TZA), the frequencies of cells producing replication-competent HIV (IUPM) were calculated in both total monocytes and CD4 T cells. Total p24 associated with replication-competent HIV produced by these cell types were quantified using a relative light unit to replication-competent HIV-associated p24 standard curve in the MoCo TZA. Ratios of total replication-competent HIV-associated p24 and IUPMs, termed infectious potential, were calculated for monocytes and CD4 T cells. Results: Among the 16 ART-suppressed chronic HIV-infected individuals evaluated, 11 had detectable peripheral blood monocytes with inducible replication-competent HIV. Although monocyte IUPMs were significantly lower as compared to CD4 T cells, the infectious potential in the monocyte compartment was slightly higher as compared to the CD4 T cell compartment. Higher surface expression of CD16 on intermediate monocytes correlated with elevated monocyte reservoir measurements. In individuals who were treated early during acute infection, all 8 had detectable circulating monocytes with inducible replication-competent HIV after 2 years of ART. Individuals with cognitive impairment had higher reservoir measurements in total monocytes as compared to those with normal cognition. In addition, higher expression of CD16 on intermediate monocytes correlated with lower executive function and global NP z-scores. No differences in CD4 T cell reservoir measurements were observed between cognitive status groups. Conclusion: Utilizing the MoCo-TZA, we show that inducible replication-competent HIV in circulating monocytes is detectable during long-term chronic infection, as well as in individuals who initiated ART early during acute infection and were on treatment for 2 years. Our results highlight the need to further understand the monocyte-derived replication-competent HIV reservoir during ART-suppression and to further investigate this reservoir compartment in HIV-associated neurocognitive disease treatments and in HIV cure efforts.