Role of Viral Reservoirs in the Pathogenesis of HIV Disease

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

The development of ART has led to remarkable improvements in the health and life expectancy of PWH. While current ART has proven to be effective in suppressing HIV, the eradication of the virus remains elusive in PWH. Given that HIV suppression in PWH requires lifelong adherence to ART, there is a need to investigate novel therapies aimed at achieving ART-free virologic remission. Over the past decade, significant therapeutic efforts have been made to eliminate the HIV reservoir in PWH. Such efforts require quantitative and reproducible laboratory assays to monitor the efficacy of therapeutics on the reservoir burden in CD4+ T cells of PWH receiving ART. As such, we examined correlations among multiple molecular- and cellular-based assays that measure the size of HIV reservoirs in a cohort of PWH who initiated ART during the chronic phase of infection. Enriched CD4+ T cells isolated from peripheral blood mononuclear cells (PBMCs) were subjected to the following assays: three molecular assays, including 1) total HIV DNA, 2) cell-associated (CA) HIV RNA, and 3) intact HIV proviral DNA (IPD) and two cellular assays, including 1) quantitative coculture (QC) and 2) inducible virion-associated (IVA) HIV RNA. Measurements of the size of the HIV reservoir correlated well across all assays performed, except for the CA HIV RNA assay. The level of CA HIV RNA correlated only with that of total HIV DNA (P=0.0002). The lack of correlation between CA HIV RNA and the other virologic markers could be because CA HIV RNA levels are influenced by cellular activation and reflect replication-defective HIV. In contrast, data from the other assays showed highly significant correlations with one another. Although the level of total HIV DNA significantly correlated with all other parameters, including IPD (P<0.0001), a significant proportion of the signal detected by the total HIV DNA assay originates from defective HIV DNA. In this regard, the QC assay, which detects replication-competent HIV, has long been recognized as the gold standard for measuring the infectious HIV burden in PWH. The infectious reservoir burden measured by the QC assay correlated significantly with that of the IPD (P=0.0065) and IVA HIV RNA (P=0.0005) assays. However, the shortcomings of this assay, including the need for large numbers of cells and lengthy culture periods, led to the development of the IPD assay, which enables the detection of intact, likely infectious viral DNA using PCR. However, the IPD assay could detect defective HIV DNA that does not contribute to the infectious viral reservoir and/or may lack specificity to detect HIV sequences in a minority of PWH. In this regard, the assay for detecting IVA HIV RNA can detect inducible HIV irrespective of its viral diversity or subtypes and uses an automated PCR detection system with a relatively short culture period (48 hours). The level of IVA HIV RNA correlated with that of infectious HIV (P=0.0005) and IPD (P=0.0005). Notably, the degree of correlation between the IVA HIV RNA and QC assays (P=0.0005) was stronger than that between the IPDA and QC assays (P=0.0065), suggesting that measurements of IVA HIV RNA could provide a quantitative estimate of the infectious viral reservoir, similar to QC assays, within a shorter timeframe. Modern ART is highly effective in suppressing viral replication and has led to transformative improvements in the health of PWH. Although ART is not curative and requires life-long adherence, the vast majority of PWH receiving antiretroviral drugs achieve sustained virologic suppression provided that they do not harbor MDR HIV. Unfortunately, some PWH with MDR HIV, including those with multiple treatment failures and significant resistance to existing antiretroviral drugs, present compelling challenges in the clinical management of HIV infection. Although the prevalence of MDR HIV infection remains relatively low in developed countries, cases of pretreatment and acquired HIV resistance to antiretroviral drugs, including the integrase inhibitor dolutegravir, are rising in developing countries. In addition, PWH with MDR HIV are at greater risk for disease progression, hospitalization, opportunistic infections, and death. A 58-year-old male PWH receiving a failing ART regimen with near pan-resistant HIV was referred to the HIV Outpatient Clinic at the National Institute of Allergy and Infectious Diseases (NIAID) for evaluation of alternative treatment options. His HIV plasma viremia was 295,656 copies/ml and CD4+ T cell count was 23 cells per µl. In addition, he had developed lesions that were diagnosed as Kaposi sarcoma (KS) by biopsy and lymphedema on his left ankle. Given the ineffectiveness of his ART regimen in suppressing his HIV plasma viremia as well as the low CD4+ T cell count and the presence of KS, we sought expanded access to UB-421 from the Food and Drug Administration (FDA). UB-421 is an Fc-aglycosylated, non-T cell-depleting, humanized IgG1 that binds to the domain 1 of the CD4 molecule on human lymphocytes. The patient subsequently discontinued ibalizumab and fostemsavir and initiated weekly infusions of UB-421 (5mg/kg) and injections of lenacapavir, a capsid inhibitor of HIV, every 6 months. Initiation of UB-421 and lenacapavir led to a rapid reduction in his HIV plasma viremia, followed by protracted second phase decay lasting more than 30 weeks. The sensitivity (80% inhibitory concentration, IC80) to UB-421 of his infectious HIV isolates remained unchanged at week 12 compared to baseline. The IC80 of lenacapavir against the infectious HIV isolates remained unchanged, suggesting that despite the persistence of residual plasma viremia for a prolonged period, the viruses in the patient remained sensitive to both UB-421 and lenacapavir. The frequency of cells carrying intact HIV proviral DNA decreased by 0.64 log between baseline and Week 68 but infected cells persisted throughout the treatment period. The level of cell-associated HIV RNA decreased rapidly by Week 8 but remained stable thereafter. Genetic analyses of plasma HIV sequences demonstrated that persistent residual plasma viremia during the treatment period was attributable to a continuous release of virions from diverse and short-lived cellular reservoirs, not ongoing HIV evolution during therapy. Collectively, our data demonstrate that combination therapy with UB-421 could provide sustained virologic suppression in persons harboring MDR HIV with limited therapeutic alternatives.