CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

396

Clinical and Immune Characteristics of ART+SIV/ P. fragile Infected Macaques With Persistent Viremia Sydney Nemphos 1 , Hannah Green 1 , James Prusak 1 , Sallie Fell 1 , Natalie Guy 1 , Matilda Mostrom 1 , Coty Tatum 1 , Kelly Goff 1 , Nicholas Maness 1 , Preston Marx 1 , Carolina Allers 1 , Brooke Grasperge 1 , Amitinder Kaur 1 , Berlin Londono-Renteria 2 , Jennifer Manuzak 1 1 Tulane National Primate Research Center, Covington, LA, USA, 2 Tulane School of Public Health and Tropical Medicine, New Orleans, LA, USA Background: Despite the efficacy of contemporary antiretroviral therapy (ART) regimens, some people with HIV (PWH) experience persistent low-level viremia (pLLV). pLLV risk factors include poor ART adherence, high viral loads (VLs) pre-ART, and co-infection. Importantly, HIV and malaria, caused by Plasmodium infection, are geographically co-endemic and both pathogens persist in the gastrointestinal (GI) tract. However, how HIV/ Plasmodium co-infection influences pLLV is unknown. Furthermore, the impact of pLLV on the GI tract, particularly in the context of co-infection, is poorly understood. Here, we used a rhesus macaque (RM) model of SIV/ P. fragile co-infection to characterize clinical and immunological differences between ART-treated RMs that were incomplete virologic responders (IVRs) with pLLV and ART-responders, with the goal of identifying biologic determinants of pLLV in the setting of ART adherence and co-infection. Methods: Male (n=6) RMs were intravenously (i.v.) inoculated with SIVmac239 (TCID50=50); initiated ART at Week(W) 8 post-SIV infection (p.i.); were i.v. inoculated with P. fragile (20x10^6 infected erythrocytes) at W12 p.i.; and euthanized at W20 p.i. Plasma VL, anemia and peripheral parasitemia were monitored via qPCR, clinical blood counts, and Geimsa-staining, respectively. CD4+ T-cell absolute counts and GI immune cell frequencies were assessed using flow cytometry. Results: All RMs exhibited clinical signs of malaria post- P. fragile co-infection. Prior to ART VLs were non-significantly higher ( P =0.093) and significantly increased post P. fragile co-infection ( P =0.034) in IVRs (n=3) as compared to ART-responders (n=3). Absolute CD4+ T-cell counts were similar between IVRs and ART-responders prior to ART, but were non-significantly higher ( P =0.069) in IVRs as compared to ART-responders following P. fragile co-infection. In the duodenum, an SIV reservoir and site of P. fragile sequestration, neutrophil frequencies were significantly increased in ART-responders compared to IVRs following P. fragile co-infection ( P = 0.046). Conclusions: IVRs had elevated pre-ART and post- P. fragile VLs, higher CD4+ T cells post- P. fragile , and fewer GI neutrophils post- P. fragile as compared to ART responders, suggesting an ineffective GI neutrophil response during P. fragile co-infection could influence the viral reservoir and contribute to pLLV during ART-treated SIV infection. Analysis of SIV Envelope Diversity During Untreated Infection Haoyue Li 1 , Emily J. Fray 1 , Vivek Hariharan 1 , Dan H. Barouch 2 , Janet M. Siliciano 1 , Robert F. Siliciano 1 1 The Johns Hopkins University School of Medicine, Baltimore, MD, USA, 2 Beth Israel Deaconess Medical Center, Boston, MA, USA Background: Viral diversification complicates immune-based cure strategies. SIV-infected Rhesus macaques (RMs) treated with antiretroviral therapy (ART) provide insights into viral dynamics and reservoir persistence in people with HIV-1. We previously described a shift in the composition of infected cell populations during ART, with recently infected cells harboring mutated proviruses decaying more rapidly, and ancestral variants seeded during early infection becoming more apparent over time (Fray et al, PMID: 36809762). Here we examine env sequences from pre-ART plasma virus to determine the full extent of viral diversification and identify sequence features that may be targeted in cure strategies. Methods: We used single-genome sequencing (SGS) to collect env sequences from pre-ART plasma from 6 RMs inoculated with SIVmac251 and placed on ART 48 weeks after infection. We analyzed the extent of variation at individual amino acid positions and performed a rarefaction analysis to estimate the number of sequences required to capture the full diversity in a given individual. Results: 800-1400 Env sequences were collected from each animal, providing a comprehensive, longitudinal dataset of viral populations replicating prior to ART within each host. Env mutations became prominent approximately 24 weeks after infection, with accumulation of non-synonymous changes across multiple regions, including the variable loops V1, V2, V4, and V5, and distinct patterns of evolution in individual macaques were observed despite inoculation with

a common stock. Even within the V regions, only certain amino acid positions accumulated mutations, whereas others were strikingly conserved, suggesting constraints on viral evolution and adaptation that limit the positions that can tolerate non-synonymous changes. Rarefaction analysis estimated that between >500 sequences are required to adequately sample the env diversity within a single host. Conclusions: Extensive datasets including pre-ART plasma and on-ART proviral sequences from individual macaques allowed us to estimate the sequencing depth required to accurately estimate the full diversity in a single host. Within each host, we observed both vast diversity and notable conservation in the env gene, likely indicating evolutionary constraints on the env protein structure. These data may be useful to identify potential targets for therapeutic interventions, including personalized vaccine strategies. STLV-1 in Chlorocebus aethiops as a Model for New Approaches to Human Retrovirus Research Víctor Â. Folgosi 1 , Liliane A. Carneiro 2 , Felipe B. Freitas 3 , Mayara N. Santana da Silva 3 , Amanda Lopes Silva 4 , Gerlane N Noronha 2 , Ariela S. Farias 2 , Carlos Fernando Apoliano 1 , Sabri S. Sanabani 1 , Hebert F. Culler 1 , Igor Costa 3 , Luís Alberto de Pádua Covas Lage 1 , Camila Malta Romano 1 , Shirley V. Komninakis 1 , Jorge Casseb 1 1 Universidade de São Paulo, São Paulo, Brazil, 2 National Primate Center (SVSA/MS), Ananindeua, Brazil, 3 Instituto Evandro Chagas, Ananindeua, Brazil, 4 Instituto de Medicina Tropical de São Paulo, São Paulo, Brazil Background: An estimated 5 to 20 million people worldwide are living with HTLV-1. Even though many of them are asymptomatic, some may develop severe conditions such as adult T-cell leukemia/lymphoma (ATLL). Despite advances in research of this infection, there is a lack of in vivo models to study retrovirus cure approaches. STLV-1 remains poorly understood, particularly in terms of natural history of the disease, genetic diversity, and modes of transmission. The aim of this study was to fill these gaps and characterize STLV-1 infection in a captive population of C. aethiops at the National Primate Center in Belém do Pará, Brazil. Methods: Blood samples were collected from 52 C. aethiops maintained in captivity, in early 2024. Serologic analysis for HTLV-1 antibodies was performed by Western blotting. STLV-1 provirus was analyzed by PCR of the LTR and tax genes, followed by genetic and phylogenetic analysis of the sequenced fragments. Clinical and hematological parameters, such as physical characteristics and white blood cell counts, were evaluated to assess immunologic effects. Results: Of the 52 specimens, seven (13.4%) tested positive for STLV-1 infection by Western Blot. The LTR regions were amplified and sequenced for all animals. The phylogeny confirms that the viruses sampled from C. aethiops cluster with other STLV-1 strains, but form a distinct subgroup from those previously described in other primate isolates. Hematological analysis indicated a significantly increased number of white blood cells and lymphocytes in STLV-1+ samples (p = 0.009 and p = 0.039), suggesting the characteristic immortalization of these cells. We did not observe significant differences in terms of weight, mucosal alterations, lymphadenopathy, or palpation examinations. However, STLV-1+ specimens exhibited a predisposition to cutaneous dehydration (p = 0.050). In females, a p-value (p = 0.046) suggests a higher risk of STLV-1 infection, similar to that observed in humans. Crucially, atypical lymphocytes, the so-called "flower cells", typically seen in humans with HTLV-1, were present in all STLV-1+ specimens (figure 1). Conclusions: Considering the great similarities in clinical and hematologic manifestations as well as the common natural course of infection and mechanisms of horizontal transmission with HTLV-1, our results suggest that STLV-1 can be used as a promising tool to validate or develop novel therapeutic or preventive strategies and represents a valuable resource for the evaluation of new antiviral drugs.

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Poster Abstracts

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CROI 2025