CROI 2020 Abstract eBook

Abstract eBook

Poster Abstracts

Results: We demonstrated successful reconstitution of functionally active T Cells (αβ and γδ T cells), NK cells, and antibody-secreting B cells in hBLTS mice, along with the formation B cell follicles within lymphatic tissues. We were also able to generate differentially matured and functionally polarized human dendritic cells from bone marrow of hBLTS mice. We found that the BLTS model also could successfully support HIV infection that could be controlled by antiretroviral therapy. Infection of hBLTS mice with live-attenuated (Nef-deleted) HIV resulted in the establishment of long-term aviremia (below detection limit). Moreover, CD4+ T cell counts were maintained in Nef-deleted HIV infected mice at levels similar to uninfected hBLTS mice. Viral control in these mice was concurrent with induction of human antiviral immune responses and reduced lymphoid tissue pathology compared to that found in hBLTS mice infected with wild type HIV. Conclusion: The immune system of the hBLTS mouse effectively recapitulates that of the human immune system, and therefore provides a robust model for investigating human immunity to HIV. Furthermore, this model provides a means to evaluate novel HIV immunotherapeutic approaches in vivo. 203 FLT3L-MEDIATED EXPANSION OF PLASMACYTOID DCS CONTROLS HIV INFECTION IN HUMANIZED MICE Tram Pham 1 , Oussama Meziane 1 , Mohammad AlamMiah 1 , Olga Volodina 2 , Chloé Colas 2 , Kathie Béland 2 , Yuanyi Li 2 , Frédéric Dallaire 1 , Tibor Keler 3 , Jean V. Guimond 4 , Sylvie Lesage 5 , Cheolho Cheong 6 , Élie Haddad 2 , Eric A. Cohen 7 1 Montreal Clinical Research Institute, Montreal, QC, Canada, 2 CHU Sainte-Justine, Montreal, QC, Canada, 3 Celldex Therapeutics, Hampton, VA, USA, 4 Centre de Santé et de Services Sociaux Jeanne-Mance, Montreal, QC, Canada, 5 Centre de recherche Hôpital Maisonneuve-Rosemont, Montreal, QC, Canada, 6 Montréal Clinical Research Institute, Montreal, QC, Canada, 7 University of Montreal, Montreal, QC, Canada Background: Plasmacytoid dendritic cells (pDCs) play a crucial role in host's immune responses through their ability to secrete high levels of IFN-I and other proinflammatory proteins. HIV infection affects pDCs although the nature of such modulation is less understood. It also remains unclear whether pDCs shape the outcome of early HIV infection. Thus, in this study, we directly assessed the role of pDCs in early phases of infection, evaluating whether modulating levels of pDCs could alter the course of viral replication. Methods: Humanized (hu) NSG and BLT mice were treated with CDX-301 and infected with CCR5-tropic NL4.3-ADA HIV for up to 3 weeks. CDX-301 is a recombinant form of fms-like tyrosine kinase-3 ligand (Flt3L), which binds the Flt3 receptor on progenitor cells and enhances development and mobilization of DCs to tissues. Mice may be treated with pDC-depleting Ab or an Ab that blocks IFN-I signalling prior to HIV exposure. Levels of DCs and infected (p24+) CD4+ T cells were analyzed by flow cytometry (FC). Splenocytes from Flt3L-treated or untreated mice were co-cultured with HIV-infected T cells or treated with TLR7/8 agonist R848 and pDCs expressing IFNα were enumerated by FC. Results: HIV infection led to systemic depletion of pDCs, but not conventional DCs, in various lymphoid organs of hu-NSG and hu-BLT mice. Flt3L treatment led to widespread expansion and mobilization of DCs to multiple tissues but had no discernable effects on levels of T cells or monocytes. Upon viral challenge, Flt3L-treated mice consistently displayed a meaningfully delayed infection and markedly reduced viremia compared to untreated mice. Levels of infected CD4+ T cells were globally reduced in the treated group. Ab-mediated depletion of pDCs abolished the protective effect by Flt3L, demonstrating that the Flt3L-mediated control of HIV was pDC-dependent. Functionally, pDCs from Flt3L-treated mice were more responsive to TLR7 stimulation, leading to a higher frequency of pDCs expressing IFNα relative to those from untreated animals. Lastly, the protective effect of Flt3L treatment was mediated through an enhanced IFN-I response as blocking IFN-I signalling early in Flt3L-treated animals restored viremia to the level of untreated mice. Conclusion: Maintaining pDC levels and functions is key to early viral control and in this context, our findings provide a practical insight for novel anti-HIV strategies and vaccine design. 204 EFFECTS OF CMV ON HIV DNA DIVERSITY IN PERIPHERAL BLOOD CELLS DURING EARLY ART Antoine Chaillon 1 , Masato Nakazawa 2 , Gemma Caballero 2 , Laura Layman 2 , Brianna Scott 2 , Christy M. Anderson 2 , Sara Gianella 2 1 University of California San Diego, San Diego, CA, USA, 2 University of California San Diego, La Jolla, CA, USA

Background: We previously showed that detectable Cytomegalovirus (CMV) DNA was associated with increased activation of CD4+ T cells and with a slower decay of HIV DNA in people starting antiretroviral therapy (ART) during early HIV infection. Here, we investigate changes in HIV DNA molecular diversity associated with CMV DNA in the setting of early ART. Methods: We obtained at least 3 longitudinal peripheral blood mononuclear cell (PBMC) samples from 37 individuals starting ART during early HIV infection and who reached virologic suppression (<50cp/ml, no viral blips) within a median of 3 months of the estimated date of HIV infection (IQR: 2.6-6.8). In each PBMC sample (N=120), levels of HIV, CMV and Epstein-Barr Virus (EBV) DNA were measured by digital droplet (dd)PCR. Deep Sequencing of HIV DNA C2-V3 env was performed using the MiSeq Illumina platform. Cleaned mapped reads were obtained after iterative read mapping and quality filtering using an in-house pipeline. The HIV DNA molecular diversity (Shannon Entropy) was computed for 99 samples. A linear mixed-effect regression model was used to analyze the effect of detectable CMV or EBV DNA on HIV DNA molecular diversity and its change from ART initiation (baseline) to the end of follow-up (approximately 30 months). Results: Participants had a median of 515 (IQR: 363-732) CD4+ T cells/ul at baseline and were followed for a median of 29 months (IQR: 18-39) while on suppressive ART. Overall, 19 (51%) participants had detectable CMV DNA during follow up, while 18 did not. Entropy levels at the time of ART initiation did not differ by CMV status (p=0.2). However, entropy levels were more likely to increase during ART for participants who exhibited CMV shedding and to decrease for those who did not (see Figure), and this change in entropy was significantly different for the 2 groups (interaction p<0.05). Such a relationship was not found for EBV (EBV by time interaction; p=0.66). Conclusion: In addition to slower HIV DNA decay and increased CD4+ T cell activation, we now observe increasing HIV DNA molecular diversity during early ART in the setting of subclinical CMV replication. Taken together, these observations suggest that subclinical CMV DNA shedding might affect HIV persistence by promoting HIV replication at low levels during early ART. Future studies with anti-CMV therapeutics could help determine the underlying mechanisms and if causal associations exist.

Poster Abstracts

205 GUT MICROBIOTA FACILITATES HIV ACQUISITION IN THE GUT

Angela Wahl 1 , Cara Richardson 1 , Wenbo Yao 1 , Allison Rogala 1 , R. Balfour Sartor 1 , J. V. Garcia 1 1 University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Background: Resident microbiota protect the gut from pathogenic organisms. However, gut microbiota can facilitate the transmission and pathogenesis of viruses. The gut is a significant site of HIV acquisition in infants (via breastfeeding) and adults (via receptive anal intercourse) and a primary site of HIV replication and CD4+ T cell depletion. The effect of gut microbiota on HIV acquisition risk, pathogenesis, and disease progression is unknown. Methods: It is not possible to perform the direct experimentation that is needed to establish gut microbiota’s role in HIV acquisition and infection in humans. Bone marrow/liver/thymus (BLT) humanized mice have been extensively utilized to study HIV acquisition, pathogenesis and prevention strategies in vivo. To examine the role of gut microbiota in HIV acquisition risk, we constructed germ-free BLT mice and BLT mice colonized with gut microbiota. First, we rederived the immunodeficient NSG mouse strain germ-free. Next, germ-free NSG mice were implanted with human thymus/liver tissue and transplanted autologous stem cells in a germ-free surgical isolator. Germ-free BLT mice were housed in a gnotobiotic Trexler isolator. The germ-free status of

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CROI 2020