CROI 2024 Abstract eBook

Abstract eBook

Poster Abstracts

complexes on antigen-presenting cells (peptide-pulsed targets or HIV-infected cells) in T cell redirection assays. Results: Tandem mass spectrometry analysis of 1 billion infected C8166 cells (19.4% Gag+ by intracellular staining) failed to identify any HIV HLA-E peptides. Of >80 bioinformatically predicted ligands, all were characterised by low or unmeasurable complex thermostability and half-lives and performed poorly in the cell surface stabilisation assay. In T cell redirection assays using the ImmTAX, consistent presentation of Gag275-283 by HLA-E was only demonstrated when peptide was supplied exogenously (peptide pulsing model). Only sporadic and inconsistent peptide presentation was detected when the peptide source was endogenously expressed HIV Gag protein (infected cells). Conclusion: This study provides biochemical and biological evidence for the failure of HIV-derived peptides to form a stable complex with HLA-E, highlighting a major challenge for HLA-E targeted drug or vaccine development. Immune Responses Associated With Mpox Viral Clearance in People With and Without HIV Coinfection Igor Moraes-Cardoso 1 , Susana Benet 2 , Julieta Carabelli 1 , Daniel Perez-Zsolt 1 , Adrià Mendoza 2 , Vicente Descalzo 3 , Yovaninna Alarcón-Soto 2 , Alba Grifoni 4 , Michael Marks 5 , Nuria Izquierdo-Useros 1 , Jorge Carrillo 1 , Clara Suñer 2 , Alex Olvera 1 , Beatriz Mothe 1 , for the MoViE-Immune Study Group 1 IrsiCaixa Institute for AIDS Research, Badalona, Spain, 2 Fundació Lluita Contra la Sida, Badalona, Spain, 3 Hospital Universitario de la Vall d’Hebron, Barcelona, Spain, 4 La Jolla Institute for Allergy and Immunology, La Jolla, CA, USA, 5 London School of Hygiene & Tropical Medicine, London, United Kingdom Background: During the emergence of the global mpox outbreak in May 2022, over 90,000 cases were diagnosed, disproportionately affecting those living with HIV. Milder re-infections have been recently reported. Here, we extensively characterized cellular and humoral responses in people without HIV (PWoH) and with HIV (PWH) at acute mpox, determined their impact on disease severity and viral clearance dynamics, and assessed post-infection immunity 6 months after mpox virus (MPXV) diagnosis. Methods: Thirty-three men (PWoH n=19; PWH n=14, all with CD4 T cell>400) from a prospective, observational cohort study (NCT0547674) were included. Samples from skin lesions were collected weekly to estimate the time to clear MPXV. Blood samples were taken at diagnosis and 29, 91, and 182 days later for immune analysis. IgG and IgA against A35L, H3R and A29L MPXV proteins were quantified by ELISA, and in-vitro neutralization capacity was measured in Vero E6 cells. T-cell responses were characterized upon antigen recall by IFNγ ELISpot and multiparametric flow cytometry. Results: PWoH and PWH had similar clinical severity and time to MPXV clearance in skin lesions. Both PWoH and PWH had comparable levels of anti MPXV IgG and broad IgA-mediated responses. Whilst in-vitro neutralization was not fully observed until 91 days after infection, both titers and breadth of antibodies induced early after infection were associated with reduced clinical severity, lower levels of virus in skin lesions and a shorter and more rapid viral clearance. Levels of antibodies increased one month after MPXV infection and waned thereafter, while frequencies of mpox-specific T-cells were sustained up to 6 months, regardless of HIV status. Although no major differences were observed in cellular activation or cytokine production between study groups, a delay in the contribution of multifunctional CD4+ T-cells was only observed in PWH. Overall, GzmB+ CD4+ and CD8+ T-cells were the predominant subsets contributing across all timepoints in both groups. Conclusion: Although PWoH and PWH had comparable immune responses at acute mpox, a delay on functional T-cell diversity and a faster wane of antibodies was observed in PWH. Mpox-specific antibodies may play a key role in the initial control of infection via non-neutralizing pathways, and a durable cellular immunity is induced following infection, which might help to contain viral spread, contribute to a faster clearance, and reduce severity in future re-infections. Orthopoxvirus-Specific IgG Upon Mpox Vaccination Among People With and Those Without HIV Wang-Da Liu , Tai-Ling Chao, Hsin-Yun Sun, Kuan-Yin Lin, Yu-Chung Chuang, Yu-Shan Huang, Guei-Chi Li, Wen-Chun Liu, Cheng-Hsin Wu, Yi-Ching Su, Lan-Hsin Chang, Chia-Yi Lin, Yi Yao, Sui-Yuan Chang, Chien-Ching Hung National Taiwan University Hospital, Taipei, Taiwan Background: In Taiwan, nationwide routine and compulsory smallpox vaccination with Lister strain had been stopped in 1979. As Mpox continued to spread worldwide, a two-dose Mpox vaccination, with an interval of at least 28

achieved in vivo with peak serum expression around day 21 and expressed for extended duration. Conclusion: Our data highlights the design and characterization of novel DNA launched immunotherapeutic against HIV-1, which possess significant characteristics of a promising immunotherapy having broad neutralization capacities of a Tier 2/3 global virus panel, specific engagement of effector cells and killing of the infected target cells and longer serum half-life in comparison to conventional bispecific T cell engaging molecules. Delivery of LHL-BnKs as combination therapy. Targeting HIV-Infected Cells for Immunotherapy Through HLA-E Niklas Bachmann , Srona Sengupta, Robert F. Siliciano The Johns Hopkins University School of Medicine, Baltimore, MD, USA Background: Cytolytic T lymphocytes (CTLs) help control viremia in people with HIV. HIV evades this response through escape mutations in CTL epitopes and downregulation of HLA molecules. The dimorphic non-canonical HLA-E molecules, however, are upregulated during infection, making them promising targets for CTL-engaging reagents such as single-chain diabodies (scDbs) provided that they present HIV epitopes. Here, we show that HIV-infected cells can be targeted for CTL-mediated lysis using novel scDbs specific for HLA-E- bound epitopes. Methods: To validate HLA-E as a suitable scDb target, we used the previously characterized M. tuberculosis- derived peptide Mtb44 that binds with high affinity to HLA-E. Through phage biopanning, we isolated a novel scDb (RLP13) that recognizes this epitope bound to HLA-E. This scDB also recognizes CD3 and is able to induce CTL activation. The specificity of RLP13 was tested through killing assays with CD8+ effector T cells and target cells presenting cognate Mtb44 peptide or the irrelevant canonical HLA-E epitope VL9. To test whether HIV-encoded peptides can be targeted, an Mtb44-encoding DNA segment was inserted into an HIV reporter virus (NL4.3 ΔEnv-GFP). Target cells were infected with this virus and co-cultured with RLP13 scDb and autologous CTLs to assess killing of infected cells. Results: RLP13 scDb induced antigen-specific lysis of Mtb44-presenting target cells, regardless of the donor HLA type, in an scDb- and antigen-dose dependent manner. Furthermore, addition of the RLP13 scDb to co- cultures of primary CD8+ T cells and autologous CD4+ T cells infected with viral reporter constructs carrying the Mtb44 epitope led to a 50% reduction of the HIV+ population, indicating that targeting of HIV-1 peptides presented on HLA-E can potentially lead to the elimination of infected cells. Conclusion: Our findings with scDb RLP13 demonstrate that virally encoded peptides presented in the context of HLA-E can be targeted by scDbs to induce CTL-mediated lysis of infected cells, regardless of HLA-genotype. The development of novel scDbs recognizing HIV-derived epitopes that bind HLA-E would provide a universal reagent that could be used to promote the killing of HIV-1 infected cells in shock and kill strategies for HIV cure. Instability of the HLA-E Peptidome of HIV Presents a Major Barrier to Therapeutic Targeting Zoe Wallace , Tiaan Heunis, Richard J. Suckling, Dawn Gibbs-Howe, Luis F. Godinho, Praveen K. Singh, Lucy Dorrell Immunocore, Abingdon, United Kingdom Background: Human leukocyte antigen (HLA) class Ia molecules present peptides derived from the ER for recognition by cytotoxic T lymphocytes. As such, HLA class Ia-restricted peptides are well characterised drug targets for infectious diseases. However, their clinical potential is limited by the high polymorphism of the HLA class I genes within the population. In contrast, the HLA class Ib molecule, HLA-E, has only two alleles and thus offers the potential to develop donor-unrestricted therapies. With only a few reported HIV-derived HLA-E restricted peptides, there is limited understanding of the composition and druggability of the HIV HLA-E 'ligandome.' We therefore sought to systematically interrogate the HIV HLA-E ligandome to identify stably presented peptides as drug targets for a potential HIV cure strategy. Methods: The HIV proteome of in vitro infected cells was interrogated for HLA-E presented peptides using both immunopeptidomic (mass spectrometry) and bioinformatic (predictive) approaches. Putative ligands were then ranked based on stability using a panel of biochemical assays as well as an HLA-E cell surface stabilization assay. The stability of the highest ranked peptide, Gag275 283, was further assessed using an affinity-enhanced T cell receptor bispecific molecule (ImmTAX). The ImmTAX was used as a probe for peptide-HLA-E

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