CROI 2025 Abstract eBook

Abstract eBook

Poster Abstracts

500

The Asymmetric Opening of HIV-1 Env by a Potent CD4 Mimetic Enables Anti-CoRBS Abs to Mediate ADCC Jonathan Richard 1 , Michael W. Grunst 2 , Ling Niu 3 , Marco A. Díaz-Salinas 4 , Li Zhu 2 , William D. Tolbert 3 , Lorie Marchitto 1 , Derek Yang 5 , Joseph Sodroski 6 , Amos B. Smith III 5 , Priti Kumar 2 , Walther Mothes 2 , James B. Munro 4 , Marzena Pazgier 3 , Andrés Finzi 1 1 Centre de Recherche du CHUM, Montreal, Canada, 2 Yale University, New Haven, CT, USA, 3 Uniformed Services University of the Health Sciences, Bethesda, MD, USA, 4 University of Massachusetts, Worcester, MA, USA, 5 University of Pennsylvania, Philadelphia, PA, USA, 6 Dana–Farber Cancer Institute, Boston, MA, USA Background: HIV-1 envelope glycoproteins (Env) from primary HIV-1 isolates typically adopt a "closed" conformation resistant to the binding of non neutralizing antibodies (nnAbs). CD4-mimetic compounds (CD4mcs) “open-up” Env, sensitizing infected cells to antibody-dependent cellular cytotoxicity (ADCC) by CD4-induced (CD4i) nnAbs. Two CD4i nnAb families, anti-cluster A and anti-coreceptor binding site (CoRBS) Abs, are necessary for ADCC with the indane CD4mc BNM-III-170. While indane CD4mcs boost recognition of infected cells by anti-CoRBS Abs, these nnAbs alone mediate ADCC poorly. The combination of anti-CoRBS Abs, indane CD4mc and anti-Cluster A Abs mediates ADCC, reducing the HIV-1 reservoir and delaying viral rebound after ART interruption in humanized mice. New indoline CD4mcs with improved potency and breath over indane CD4mcs were recently described. Here, we investigate the mechanism behind their improved ADCC activity. Methods: The ability of nnAbs to mediate ADCC with indane or indoline CD4mcs was tested in vitro , and their impact on viral rebound was evaluated in vivo in HIV-1-infected humanized mice. The impact of indoline CD4mc on Env conformation was evaluated by smFRET, cryo-EM and cryo-ET. Results: Unlike indane CD4mcs, the lead indoline CD4mc CJF-III-288 enables anti-CoRBS Abs to mediate ADCC across multiple HIV-1 primary strains. Strikingly, CJF-III-288 exposes the CoRBS and sensitizes infected cells to ADCC by anti-CoRBS Abs or plasma from PLWH, at concentrations where indane CD4mcs fail. Masking the CoRBS with anti-CoRBS Fabs significantly reduced ADCC mediated by plasma from PLWH in the presence of CJF-III-288. In humanized mice, CJF-III-288 with a CoRBS Ab alone delays viral rebound after ART interruption. Structural and conformational analyses reveal that CJF-III-288 stabilizes an asymmetric “open” State-3 Env conformation that alters anti CoRBS Ab binding orientation. Our analyses also reveal a variation in the Env’s tilting and the anti-CoRBS Ab binding angle, which likely facilitates Fc receptor engagement on effector cells. Conclusions: Overall, functional and structural data support that CJF-III 288 induces an “open” asymmetric Env conformation modifying the binding orientation of anti-CoRBS Abs, boosting their ADCC activity. This highlights CJF-III-288's therapeutic potential to eliminate HIV-1-infected cells by ADCC. TCR-Mimic ScDb Reduced HIV Provirus and Delayed the Viral Rebound in HLA Specific BLT Hu-Mice Zhe Yuan 1 , Nathan L. Board 2 , Srona Sengupta 3 , Guorui Zu 1 , Janet M. Siliciano 3 , Robert F. Siliciano 3 , Luis J. Montaner 1 1 The Wistar Institute, Philadelphia, PA, USA, 2 Weill Cornell Medicine, New York, NY, USA, 3 The Johns Hopkins University School of Medicine, Baltimore, MD, USA Background: Despite the efficient suppression of HIV-1 replication with combined antiretroviral therapy, viral latency is a barrier to HIV cure. Bispecific antibodies against Env and CD3 have resulted in the ex vivo killing of HIV containing cells from PLWH. However, the low level of Env expression on the cell surface and the sequence variation in the env protein highlight the need for alternative approaches. We previously generated bispecific TCR mimic (TCRm) reagents against CD3 and HIV-1 Pol region, capable of linking CTLs to infected cells and promoting target cell lysis. Based on this ex vivo killing capability, we investigated whether the TCR-mimic single-chain diabodies (ScDb) could reduce the provirus and delay viral rebound post ATI. Methods: Novel BLT hu-mice generated from donors with the HLA-A*02:01 allele were infected with transmitted/ founder (T/F) virus HIVsuma. Viremia was suppressed on cART. ScDb HI12 against the Pol region and control ScDb H2 against a p53 epitope were used to treat the animals from 3 to 5 weeks post inoculation. ScDb in vivo kinetics were measured. HI12 or H2 were administered daily to animals with partially suppressed viremia. Weekly plasma viral load and proviral reservoir size by IPDA on cART and viral rebound after cART interruption were measured. CD4 depletion and T cell activation were also evaluated.

CA-vDNA lo <100cps/10^6 CD4 T cells). Integrative analysis revealed that CA-VDNA lo RMs presented increased chromatin accessibility for target genes of IRF7/3 and STAT1, which resulted in significantly higher expression of IFN stimulated antiviral machineries in myeloid cells and CD4+ T cells. On the other hand, combo-treated CA-vDNA hi RMs showed increased chromatin accessibility for the SMAD2/SMAD3, AP-1, and NFKB1 target genes and consequently higher expression of its downstream pathways (i.e. TGF-b signaling), resulting in higher SIV reservoir and higher susceptibility to infection during ATI. Of note, CA-vDNA hi RMs, presented significantly higher TGF-b plasma levels pre-ATI, and significantly higher frequencies of TGF-b+ Tregs prior to the immune intervention, which contributed to the increased downstream TGF-b signaling in these RMs. In vitro assays confirmed the detrimental impact of TGF-b on IFN-signaling, by blocking STAT1 phosphorylation, while the abrogation of such upstream signal, by using anti-TGFb antibody, unleashed the IFN-signaling and blocked HIV-infection. Signatures of the CA-vDNA lo RMs were observed in HIV elite controllers, who maintain undetectable levels of virus in the absence of ART and who present a small HIV reservoir size. Conclusions: Overall, these results highlight the critical role of the interplay between TGF-b and IFN in the development of epigenetically regulated innate antiviral immune responses that can impact the viral reservoir. The figure, table, or graphic for this abstract has been removed. Genetic Regulation of Immune Responses to CMV in Spontaneous HIV Controllers Suzanne D. E. Ruijten 1 , Jéssica dos Santos 1 , Adriana Navas 1 , Nadira Vadaq 1 , Alisa Huber 1 , Victoria Rios Vazquez 1 , Albert L. Groenendijk 2 , Louise E. van Eekeren 1 , Wilhelm A. Vos 3 , Marc J. T. Blaauw 4 , Mihai G. Netea 1 , Vasiliki Matzaraki 1 , Andre van der Ven 1 , for the 2000HIV Human Functional Genomics Partnership Program 1 Radboud University Medical Center, Nijmegen, Netherlands, 2 Erasmus University Medical Center, Rotterdam, Netherlands, 3 OLVG, Amsterdam, Netherlands, 4 Elisabeth-TweeSteden Ziekenhuis, Tilburg, Netherlands Background: HIV controllers (HICs) spontaneously control an HIV infection and are important to understand HIV immunopathogenesis. We previously showed that HIV-control associated genetic variants in the MHC locus downregulate IL-1β and TNF-α responses to CMV pp65 in PBMCs in people living with HIV (PLHIV) (CROI 2024, abstract 319). Here, we investigated how cytokine responses are organized in HICs versus non-controllers on cART (non-HICs), and how genetic factors regulate these responses. Methods: 1895 virally suppressed PLHIV were included in the 2000HIV study (NTC03994835), of which 114 were HICs. Cytokine production was measured upon PBMC stimulation with a range of stimuli, and co-regulation was assessed using unsupervised hierarchical clustering in HICs and non-HICs separately. Functional effects of HIV control and CMV response associated SNPs were assessed using gene expression QTL summary statistics from the 2000HIV cohort. Memory responses to CMV pp65 and HIVENV peptides were evaluated by measuring IFN-γ and granzyme B production upon 24-hour PBMC stimulation in 57 PLHIV (55 CMV+) and 41 healthy controls (HC) (23 CMV+) from the 2000HIV-TRAINED cohort (NCT04968717). Finally, we tested the association of imputed classical HLA alleles and amino acids with CMV serostatus using logistic regression in 87 CMV seronegative (CMV-) and 1180 CMV-seropositive (CMV+) PLHIV. Results: We observed that pro-inflammatory cytokine responses to CMV pp65 and HIVENV clustered more closely in non-HICs compared to HICs (Figure 1). The HIV-control associated SNPs regulating response to CMV were found to regulate the expression of HLA-B , HLA-C and long non-coding RNAs in the MHC locus, suggesting regulation of memory cell responses to CMV pp65. We confirmed the presence of memory IFN-γ responses to CMV pp65, which were stronger in CMV+PLHIV compared to CMV+HC, and more pronounced than responses to HIVENV in PLHIV. Since MHC variants regulate response to CMV, we tested their effect on CMV serostatus. We found suggestive associations (P < 0.05) with 7 classical HLA alleles and 14 HLA amino acids, of which only HLA-A*31:01 has been associated to HIV control. Conclusions: HICs have a particular co-regulation of CMV-specific responses. HIV control associated SNPs in the MHC locus downregulate IL-1β and TNF-α responses to CMV pp65, presumably through modulating memory responses, which are stronger in PLHIV compared to healthy controls. The role of CMV driven inflammation should be considered in functional cure efforts.

Poster Abstracts

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