CROI 2024 Abstract eBook

Abstract eBook

Poster Abstracts

385

Complement Activation as a Mechanism of Protection by SARS-CoV-2 mRNA Vaccines in Men With HIV-1 Dylan J Tuttle , Nicolas Sluis-Cremer, Robbie B. Mailliard, Charles R. Rinaldo, Ernesto T. Marques University of Pittsburgh, Pittsburgh, PA, USA Background: People living with HIV (PLWH) are recommended to be fully vaccinated against SARS-CoV-2. However, men with HIV-1 (MWH) respond to the COVID-19 vaccine with lower immunoglobulin binding and neutralization titers against SARS-CoV-2 than men without HIV-1 (MWOH). Although neutralization is an important protective mechanism against SARS-CoV-2, other mechanisms can play a key role in protection. Therefore, we assessed antigen-specific complement activation in vaccinated MWH and MWOH. Methods: We quantified activation of the classical compliment cascade through C3 deposition by antibodies specific for SARS-CoV-2 S1 and for the receptor binding domain (RBD) in MWH and MWOH from the MACS/WIHS Combined Cohort Study using a bead-based flow cytometry assay and capture C3/C3a ELISA. Results: When matched on anti-S1 IgG titer, MWH had 10-fold greater C3 deposition than MWOH against the Washington (WA) and Omicron strains. However, the level of complement activation was proportional to the IgG titer. MWH thus, had lower C3 deposition against the RBD of both WA and Omicron strains without titer matching, which is consistent with MWH having lower vaccine induced antibody titers than MWOH. For both MWH and MWOH, C3 deposition against the RBD and full S1 proteins were comparable. However, C3 deposition against the Omicron RBD was lower than for the WA RBD, indicating lower affinity of antibodies binding to the variant RBD. These antibodies still induced a strong activation of the classical complement cascade, even as neutralization titers against the Omicron strain are low, indicating that non neutralizing antibodies that bind to Omicron can mediate protection through complement activation. Finally, we found that the C3 levels significantly declined post-vaccination in MWH, concomitant with a significant increase in C3a levels in serum, suggesting an elevation of the baseline complement activity in this group. Conclusion: Collectively, these data suggest that complement activation is a mechanism of protection of SARS-CoV-2 vaccination, and that it can have a greater impact on protection against SARS-CoV-2 variants in the absence of neutralizing antibody titers. It also suggests that antibodies with greater complement activation potency in MWH can compensate for lower antibody titers. These results highlight a critical mechanism of protection in MWH that can inform further booster vaccination schedules. WITHDRAWN Immunity to Seasonal HCoVs and Cross-Reactivity to SARS-CoV-2 Prior to the COVID-19 Pandemic Dawda Jobe 1 , Natalie Barratt 2 , Aji F. Touray 3 , Ya Jankey Jange 3 , Hailey Hornsby 2 , Madikoi Danso 3 , Rhys Wenlock Wenlock 1 , Alansana Darboe 3 , Beate Kampmann 4 , Thushan d. Silva 2 1 London School of Hygiene & Tropical Medicine, London, UK, 2 University of Sheffield, Sheffield, UK, 3 Medical Research Council Unit The Gambia at the London School of Hygiene & Tropical Medicine, Banjul, The Gambia, 4 Charité Universitqtsmedizin, Berlin, Germany Background: Despite a high burden of infection with SARS-CoV-2 in African countries, disease severity has been surprisingly low in many settings. One potential hypothesis to explain this observation is the presence of cross-reactive immunity due to prior exposure to endemic human coronaviruses (HCoVs). We aimed to assess SARS-CoV-2 reactivity and IgG antibodies to HCoVs in pre pandemic samples in The Gambia. Methods: 805 biobanked pre-pandemic serum samples from the Gambia were used to assess SARS-CoV-2 cross-reactivity using an indirect ELISA to detect SARS-CoV-2 specific IgG antibody responses. A Meso Scale Discovery (MSD) assay was utilized to assess IgG binding to spike proteins of 229E, NL63, OC43, HKU1, SARS and MERS-CoV. Results: 21% of pre-pandemic samples were reactive to SARS-CoV-2 nucleocapsid (N), compared to only 4% reactivity to SARS-CoV-2 spike. A significant association between age and anti-N cross-reactivity was observed with N-IgG positivity seen in 5% of children <5 years, 11% of children aged 5-17 years, 33% of adults 18-50 years and 42% of adults aged >50 years (P<0.0001). Higher IgG titres to all HCoV spike proteins were seen in adults compared to children, with minimal reactivity to SARS and MERS-CoV-2 spike proteins. Samples positive for anti-SARS-CoV-2 nucleocapsid IgG had significantly

and cellular immune responses leading to significant delays in infection followed by rapid and durable plasma viral control to undetectable.

384

Naive B-Cells From Unvaccinated Rhesus Macaques Cross-React With HIV gp140 Protein Michelle Premazzi Papa 1 , Andrew Wilson 1 , Rosemarie Mason 2 , Jennifer A. Manuzak 3 , Nichole R. Klatt 4 , Rebecca M. Lynch 1 1 George Washington University, Washington, DC, USA, 2 National Institutes of Health, Bethesda, MD, USA, 3 Tulane National Primate Research Center, Covington, LA, USA, 4 University of Minnesota, Minneapolis, MN, USA Background: HIV causes a chronic infection that it is not cleared by the normal immune response, in part due to an ineffective early antibody response. Other groups have shown that early in infection, people with HIV-1 (PWH) develop anti-gp41 antibodies that cross-react with commensal bacteria but do not neutralize HIV, and that this same phenomenon occurs after vaccination. Here, we investigate if the baseline antibody response prior to HIV vaccination is comprised of antibodies targeting commensal bacterial that weakly target HIV, and if these antibodies are preferentially activated after subsequent infection. Methods: To test this hypothesis, PBMC samples from a SIV/HIV DNA vaccine (SIV gag (p55), HIV env (gp160), and gp140 trimeric protein) and simian-human immunodeficiency virus (SHIV) challenge study in Rhesus Macaques (RhM; n=8) were collected prior to vaccination (week -7) and stained using an 11-color B cell panel. HIV-1 gp140-specific B cells from these SHIV-naïve RhM were sorted and nested-PCR was performed using specific primers for IgG, IgM, IgA heavy chains, and Kappa and Lambda light chains. PCR products were sequenced and compared to germline using IMGT/V-QUEST. Selected sequences were cloned as IgG1 and tested for function. Results: A total of 120 cells were sorted (ranging from 1-44 cells per RhM). 95 heavy chains were amplified, and 70 had productive ORF sequences. 56 out of 70 were IgM, seven were IgA, and seven were IgG sequences. Analyzing light chains, a total of 110 were amplified and 63 had productive ORF sequences. 42 out 63 were Kappa and 21 were Lambda sequences. From these, 35 had productive heavy and light chain sequences. Fourteen cells that exhibited intermediate and high gp140 binding during cell sorting were selected for cloning. Monoclonal antibodies (mAbs) were generated and tested for binding to gp41, gp120, and gp140 proteins. Ten mAbs recognized gp41, two mAbs bound to gp120, and five recognized gp140. A total of four mAbs bound to MAPK14 with high and low affinities, the two with high affinity also bound to LPS (Fig 1). This data shows that these mAbs not only cross-react with bacteria but also bind to different cellular components suggesting that these are polyreactive antibodies. Conclusion: Here, we show that B cells can recognize HIV without previous vaccination or infection, and they are mostly naïve (IgM+). Future directions include investigating if these clones are expanded after vaccination and/or SHIV infection trough deep sequencing..

Poster Abstracts

386

91

CROI 2024