HIV DNA reservoir and elevated PD-1 expression of CD4 T-cell subsets particularly persist in the terminal ileum of HIV-positive patients despite cART

OBJECTIVES

Despite its importance as an HIV anatomic sanctuary, little is known about the characteristics of the HIV reservoir in the terminal ileum (TI). In blood, the immune checkpoint inhibitor programmed-death-1 (PD-1) has been linked to the HIV reservoir and T-cell immune dysfunction. We thus evaluated PD-1 expression and cell-associated HIV DNA in memory CD4 T-cell subsets from TI, peripheral blood (PB) and rectum (RE) of untreated and treated HIV-positive patients to identify associations between PD-1 and HIV reservoir in other sites.

METHODS

Using mononuclear cells from PB, TI and RE of untreated HIV-positive (N = 6), treated (n = 18) HIV-positive and uninfected individuals (n = 16), we identified and sorted distinct memory CD4 T-cell subsets by flow cytometry, quantified their cell-associated HIV DNA using quantitative PCR and assessed PD-1 expression levels using geometric mean fluorescence intensity. Combined HIV-1 RNA in situ hybridization and immunohistochemistry was performed on ileal biopsy sections.

RESULTS

Combined antiretroviral therapy (cART)-treated patients with undetectable HIV RNA and significantly lower levels of HIV DNA in PB showed particularly high PD-1 expression in PB and TI, and high HIV DNA levels in TI, irrespective of clinical characteristics. By contrast, in treatment-naïve patients HIV DNA levels in memory CD4 T-cell subsets were high in PB and TI.

CONCLUSION

Elevated PD-1 expression on memory CD4 T-cells in PB and TI despite treatment points to continuous immune dysfunction and underlines the importance of evaluating immunotherapy in reversing HIV latency and T-cell reconstitution. As HIV DNA particularly persists in TI despite cART, investigating samples from TI is crucial in understanding HIV immunopathogenesis.

Predictors and Barriers to Condom Use in the African Cohort Study

Consistent condom use is an inexpensive and efficacious HIV prevention strategy. Understanding factors associated with condom use and barriers to use can inform strategies to increase condom uptake. The ongoing African Cohort Study prospectively enrolls adults at 12 clinical sites in Uganda, Kenya, Tanzania, and Nigeria. At enrollment, participants are asked about condom use at last sex with a regular partner. Robust Poisson regression models were used to evaluate predictors of self-reported condom use. Participants who reported not using condoms were asked to provide reasons. From January 2013 to September 2019, 2482 participants reported having at least one regular sexual partner in the preceding 6 months. Of those, 1577 (63.5%) reported using a condom at last sex. Condom use was more common among older participants, males, HIV-infected participants, and those with an HIV-infected partner. Married participants, those with a partner of unknown HIV status, and those reporting alcohol use were less likely to report condom use at last sex. Condom use at last sex also varied significantly by clinical site. Partner disapproval or refusal to use a condom was a consistent driver of disparities in condom use among participants who were HIV infected, female, and aged 18-24 years. Effective HIV prevention programs should integrate condom education with the tools necessary to negotiate condom use with regular partners.

Identification of vaccine candidates for experimental visceral leishmaniasis by immunization with sequential fractions of a cDNA expression library

Visceral leishmaniasis caused by the intracellular parasite Leishmania donovani is a significant public health problem in many regions of the world. Because of its large genome and complex biology, developing a vaccine for this pathogen has proved to be a challenging task and, to date, protective recombinant vaccine candidates have not been identified. To tackle this difficult problem, we adopted a reductionist approach with the intention of identifying cDNA sequences in an L. donovani amastigote cDNA library that collectively or singly conferred protection against parasite challenge in a murine model of visceral leishmaniasis. We immunized BALB/c mice with plasmid DNA isolated and pooled from 15 cDNA sublibraries ( approximately 2,000 cDNAs/sublibrary). Following systemic challenge with L. donovani, mice immunized with 6 of these 15 sublibraries showed a significantly reduced (35- to 1,000-fold) hepatic parasite burden. Because of the complexity and magnitude of the sequential fractionation-immunization-challenge approach, we restricted our attention to the two sublibraries that conferred the greatest in vivo protection. From one of these two sublibraries, we identified several groups of cDNAs that afforded protection, including a set of nine novel cDNAs and, surprisingly, a group of five cDNAs that encoded L. donovani histone proteins. At each fractionation step, the cDNA sublibraries or the smaller DNA fractions that afforded in vivo protection against the parasite also induced in vitro parasite-specific T helper 1 immune responses. Our studies demonstrate that immunization with sequential fractions of a cDNA library is a powerful strategy for identifying anti-infective vaccine candidates.