CROI 2024 Abstract eBook

Abstract eBook

Poster Abstracts

of anti-CD25 monoclonal antibody (mAb) on the germinal center response to immunization. We tested three mAb treatment arms: inhibiting CD25+ Treg cells (Basiliximab), depleting that population (Anti-Tac), and a control (anti-influenza CH65). We immunized a cohort of rhesus macaques (RMs) with sequential gp120CH505 Envelopes (Envs) that mimicked the mutational pattern observed during HIV-1 infection and tested for the development of HIV-1 broadly neutralizing antibodies (bnAbs). Methods: Nine RMs were randomly divided into three groups that received 1 mg per infusion of Basiliximab, Anti-Tac, or CH65. Plasma antibody responses were assayed by ELISA. Linear epitope mapping of plasma antibodies was performed by peptide microarray. Immune cell phenotypes were evaluated by flow cytometry. Single-cell PCR and sequencing were conducted to define the antibody spectrum of HIV-1 Env-specific memory B cells derived from lymph nodes. IgM anti-IgG in RMs was assayed by ELISA. Results: All RMs developed antibodies that blocked CH106 or sCD4 binding to gp120CH505TF and gp12063521. Binding to HIV-1 Env-specific linear epitopes trended lower after each immunization and infusion in RMs that received anti-CD25 treatment, compared to those received CH65. Treg cell and CXCR5-expressing follicular Treg cell frequency was slightly decreased after the first anti-CD25 infusion but was similar after later infusions. Plasma anti-CD25 activity was detectable after the first infusion but limited after later infusions; CH65 infusion did not show the same pattern. We hypothesized that an anti-antibody immune response developed in anti-CD25 infused RMs; these RMs developed rheumatoid factor after anti-CD25 mAb infusion that matched loss of anti-CD25 plasma activity. Notably, the transient Treg cell disruption that we observed was associated with a change in germinal center responses, as assessed by the size and number of vaccine-elicited B- cell clonal lineages in lymphoid tissue. Conclusion: Transient Treg perturbation strategies to break immune tolerance and increase poly-reactive anti-Env antibodies in immunized RMs were limited by anti-antibody responses, indicating that immune manipulation strategies to drive the development of protective bnAbs may have off target effects. Characterizing New and Boosted HIV-Specific T-Cell Responses Elicited by an HIV Therapeutic Vaccine Lily Zemelko 1 , Mansi Purwar 2 , Kara W. Chew 3 , Emma Reuschel 4 , Megan Wise 5 , Nicole M. Bedanova 2 , Laurent Humeau 4 , Nilu Goonetilleke 6 , Rafick P. Sekaly 7 , David B. Weiner 2 , Steven G. Deeks 1 , Rachel Rutishauser 1 1 University of California San Francisco, San Francisco, CA, USA, 2 Wistar Institute, Philadelphia, PA, USA, 3 University of California Los Angeles, Los Angeles, CA, USA, 4 Inovio Pharmaceuticals, Inc, Plymouth Meeting, PA, USA, 5 Merck & Co, Inc, West Point, PA, USA, 6 University of North Carolina at Chapel Hill, Chapel Hill, NC, USA, 7 Emory University, Atlanta, GA, USA Background: Little is known about the capacity of HIV therapeutic vaccines to overcome pre-existing immunodominance hierarchies and elicit functional, long-lived new or boosted HIV-specific CD8+ T cell responses. We previously reported therapeutic vaccine-induced new and boosted HIV-specific T cell responses in people with HIV on ART in the PENNVAX trial. We now characterize the magnitude, proliferative capacity, and durability of these responses. Methods: Participants received gag+pol+IL-12 DNA (GP, n=11), gag+pol+env+IL-12 DNA (GPE, n=15), or placebo (n=13) vaccination via intramuscular electroporation. Individual Gag peptide-specific T cell responses (vaccine-matched 15-mer peptides) were measured via IFNγ ELISpot at baseline (BL), 2 weeks after the last vaccine (Week [Wk] 14), and at Wk48. Responses were defined as "new" at Wk14 if they were absent at BL with a fold change (FC)≥2, and "boosted" if present at BL and Wk14 with FC≥2. We then performed a 6-day in vitro peptide stimulation assay with Cell Trace Violet (CTV) to discern CD4+/CD8+ identity and quantify the proliferative capacity of the responses (%CTVlo of total CD4+ or CD8+ T cells). Results: At Wk14 versus BL, 10 new Gag-specific T cell responses formed in 5 vaccinated participants (4 in GP arm, 1 in GPE) and 26 Gag-specific T cell responses were boosted in 8 vaccinated participants (4 in GP, 4 in GPE; Fig 1A); there were no new or boosted responses in the placebo group. CD8+ T cells responded to 4 of the new and 20 of the boosted peptides. New responses had a median [IQR] magnitude of 48 [36-95] SFU/1e6 PBMC and proliferation of 1.89% [1.13-4.43%]. Between BL and Wk14, boosted response magnitude increased from 23 [17-70] to 114 [60-179] SFU/1e6 PBMC (p=0.02 boosted vs new at Wk14). Proliferation of boosted responses was unchanged (0.70% [0.41 1.00%] at BL, 0.91% [0.39-2.27%] at Wk14). At Wk48, 5 of the new responses

-0.65≤r≤-0.4). Non-significant inverse associations were detected for CD8RE, the custom MHC Class I pool, NSP3 and the HCoV-HKU1 peptide pool (p>0.05, -0.37≤r≤0.18). Conclusion: SARS-CoV-2-specific T cell responses targeting the structural and nonstructural virus proteins, (including the RTC), were associated with airway virus control during early, acute infection before seroconversion. Results show an inverse correlation between the Upper Airway Viral Load (UA-VL) and circulating viral N, ORF3a, RTC, and NSP13-specific T cells, as well as an inverse correlation between UA-VL and MHC Class II-restricted peptides.

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Sex-Specific Transcriptional Profiles Associate With Severe SARS-CoV-2 Infection Guido Massaccesi 1 , Ziqi Fu 2 , Andrea Cox 1 , Weiqiang Zhou 2 , Eileen P Scully 1 1 The Johns Hopkins University, Baltimore, MD, USA, 2 The Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA Background: Rates of severe disease and death from SARS-CoV-2 infection are higher in males than in females, but the mechanisms are unclear. We interrogated the transcriptional profile associated with severe disease in males and females to investigate differences in pathogenesis. Methods: Individuals with SARS-CoV-2 in the CCPSEI cohort from 4-7/2020(Cohort 1) and 7/2020- 1/2021(Cohort 2) were enrolled; Cohort 2 all received dexamethasone. Whole blood RNA was extracted from cryopreserved Paxgene tubes from the earliest timepoint and sequenced (NovaSeq). Plasma N antigen level was measured (Simoa,Quanterix). Participants were classified as mild-moderate and severe by the WHO scale. Differentially expressed genes(DEGs) and pathways and N antigen levels were compared between mild- moderate and severe in the full cohorts and within sex adjusted for age and BMI. A publicly available data set of bulk neutrophil sequencing was used to assess neutrophil phenotype by sex. Results: Cohort 1: n=95, 48% male, median age 53, median sample 4 days after test. Cohort 2: n=59, 56% male, median age 56, median sample 3 days after test+, and on day of dexamethasone. In Cohort 1 there were 3173 DEGs in severe versus mild-moderate, enriching pathways associated with hypoxia. 54% of DEGs were shared in Cohort 1 males. Male DEGs enriched neutrophil activation/ degranulation and granule pathways. In Cohort 1 females, there were few DEGs(n=111)between severe and mild-moderate; female specific DEGs enriched unfolded protein response and ER stress pathways. In Cohort 2, administration of dexamethasone ablated differential gene expression in males(n=1 DEG), but had minimal impact on DEG in females(n=149). CIBERSORT identified quantitative differences in neutrophil enrichment. Sex-stratified analysis of bulk neutrophil sequencing from 370 individuals with SARS-CoV-2 identified increased immature neutrophils in males and increased PDL1+ISG+ neutrophils in females with severe disease. Plasma N antigen level was linked to antiviral responses, and detection was less frequent in males with severe disease. Conclusion: Whole blood transcriptional responses show marked upregulation of neutrophil response genes in severe disease in males. Dexamethasone treatment ablates the transcriptional response in males with severe disease, with less impact in females. Both quantitative and qualitative differences in neutrophils contribute, and N antigen levels suggest that severe disease in males was linked to inflammation. Regulatory T-Cell Manipulation Is Limited by Anti-Antibody Responses in HIV-1 Env- Immunized RMs Shuqin Gu 1 , Kan Luo 1 , Tarra Von Holle 1 , Thaddeus C. Gurley 1 , Hilary Bouton Verville 1 , Xiaoying Shen 1 , Georgia D. Tomaras 2 , Barton F. Haynes 1 , M. Anthony Moody 1 1 Duke Human Vaccine Institute, Durham, NC, USA, 2 Duke University School of Medicine, Durham, NC, USA Background: CD25+FoxP3+CD4+ regulatory T (Treg) cells help mediate antigen tolerance in immune responses. We aimed to dissect the influence

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CROI 2024