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Browsing School of Pathology (ETDs) by Keyword "Antibodies"
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Item Defining Fc-mediated Functions in People Living with HIV during Respiratory Viral Infection and Vaccination(University of the Witwatersrand, Johannesburg, 2024) Motsoeneng, Boitumelo Madika; Moore, PennyThere are approximately 39 million people living with human immunodeficiency virus (HIV) (PLWH) worldwide. Furthering our understanding of humoral immune responses to respiratory viral infection and vaccination in PLWH is essential for reducing the burden of these diseases, in high HIV prevalence settings, and informing vaccine implementation in this population. Influenza virus hemagglutinin (HA) stalk-specific antibodies have been associated with protection and shown to mediate Fc-mediated functions. This thesis describes HA stalk-specific antibody- dependent cellular phagocytosis (ADCP), cellular cytotoxicity (ADCC) and complement deposition (ADCD) between PLWH and people without HIV (PWOH) following immunization with a seasonal trivalent inactivated influenza vaccine (TIV). Irrespective of HIV status, ADCD was boosted while ADCC was not. ADCP was only enhanced in PWOH. The coordination of these functions differed by HIV status. Additionally, differences in the regulation of these HA stalk Fc responses by HIV infection was reported. Furthermore, ADCC was not associated with protection in this study. Pre- existing ADCP reduced the risk of influenza virus infection while TIV-induced ADCD provided protection against influenza-illness. Overall, PLWH have unique responses to TIV and HA stalk- specific ADCD correlated with protection following TIV. For SARS-CoV-2, antiretroviral treatment (ART)-naïve PLWH had reduced humoral responses to respiratory infection. The infecting variants D614G and Beta differentially triggered ADCC, ADCD and antibody-dependent cellular trogocytosis (ADCT). Regarding the kinetics, PLWH infected with D614G had delayed neutralization and ADCP while Beta infection delayed ADCT, regardless of HIV status. PLWH showed improved coordination between immune responses following respiratory infection. ChAdOx-1 nCoV-19 vaccination differed from infection in that PLWH had delayed IgG binding while neutralization and ADCP were not delayed, and ADCC was substantially enhanced than in PWOH. In conclusion, despite the delayed and differential kinetics, PLWH on ART developed equivalent responses to PWOH, supporting the rapid rollout of ART and SARS-CoV-2 vaccines to PLWH. This thesis highlights the need to include high-risk groups with different responses in future vaccination trials and also supports the assessment of novel correlates of protection for future vaccines. Overall, this thesis provided insights into the mechanisms required for protection against severe respiratory diseases and improved our understanding of vaccine-induced immunity in PLWHItem Defining the development of gp120-gp41 interface directed broadly neutralizing antibodies in HIV-1 infection(2024) Hlatshwayo, Vincent NkosinathiA prophylactic HIV-1 vaccine will likely need to elicit broadly neutralizing antibodies (bNAbs) against conserved HIV-1 envelope epitopes such as the gp120-gp41 interface which includes the FP. The isolation of gp120-gp41 interface-, and FP-directed bNAbs from chronically HIVinfected donors has made this epitope an appealing vaccine target. Moreover, promising preclinical immunogenicity animal studies have shown the possibility of eliciting such responses in animals. However, little is known about the population prevalence or kinetics of gp120-gp41 interface responses, including FP-directed responses. Lastly, few FP-directed antibodies have been isolated from people living with HIV (PLWH), limiting our understanding of common developmental pathways that can be explored for vaccine purposes. Here, we first assessed the prevalence of bNAbs in participants previously enrolled in the CAPRISA 004 Tenofovir gel trial (CAP004). We show that in this cohort, only 12% of individuals developed breadth at three years post-infection, and that high viral load and low CD4 count were associated with bNAb development, as previously reported. ELISA screening showed that only 13% of individuals developed FP-directed responses at three years postinfection. Of the 13% (n=9), only two donors had broad plasma responses, including donor CAP312, whose plasma exhibited 64% neutralization breadth at three years post-infection. In CAP312, FP binding and heterologous neutralization against a multi-clade 22 virus panel appeared simultaneously, within one year (~ 50 weeks post-infection). Taken together, our findings suggest that gp120-gp41 interface- and FP-directed responses are infrequently elicited during infection. As few FP-specific bNAbs have been isolated to date, little is known about their shared features that could be exploited for eliciting FP-specific bNAbs by vaccination. We next isolated three FP-specific mAbs from donor CAP312 at three years post-infection; AIRU-F8, AIRU-G9 and AIRU-G4 with 64, 45 and 5% breadth, respectively. We showed that our mAbs, and previously isolated bNAbs PGT151 and ACS202 share gene usage and have a similar unusually long CDRH3, as a result of a conserved motif inherited from the germline IGHJ6*02 gene. Furthermore, we showed that CAP312 mAbs have even longer CDRH3s compared to PGT151 and ACS202 despite this shared motif. We also showed, using point mutants and glycan mutants that our FP-specific mAbs have a unique neutralization profile compared to published mAbs. Overall, these results suggest that FP-specific mAbs share structural and genetic features that could be explored further for lineage vaccine development. Lastly, we delineated the ontogeny of the gp120-gp41 interface-directed nAb CAP248-2B by tracing the evolutionary pathways utilising longitudinal samples from 11-281 weeks postinfection (wpi). CAP248-2B interacts with the HIV-1 Env trimer through a long light chain CDRL3 that inserts into the viral membrane, and a heavy chain CDRH1 32ED33 motif that interacts with gp41. We showed that the unusually long light chain CDRL3 and the heavy chain 32ED33 motif are functionally redundant against heterologous viruses. We also showed that affinity maturation mutations in this lineage selected a lineage with limited heterologous neutralization breadth. In summary, these findings support further research into gp120-gp41- and FP-specific responses in multiple cohorts. Furthermore, future studies should aim to elucidate mechanisms governing the development of these responses so that productive developmental pathways can be identified and exploited for vaccine design.Item Delineating the ontogeny of an N332-directed anti-HIV-1 broadly neutralising antibody lineage(2024) Naidoo, ThamaraBroadly neutralising antibodies (bNAbs) develop in chronically HIV-1 infected individuals and can neutralise a variety of HIV-1 Env strains, making them an important element contributing to the design of HIV-1 vaccines. By understanding and delineating the long affinity maturation pathways that bNAb lineages follow against evolving viruses, it is hoped that this process will be able to be replicated in uninfected people with a series of vaccine immunogens. Investigating the ontogeny of a N332-directed bNAb lineage will provide insights into the key somatic hypermutations necessary for the development of neutralisation breadth. CAP255.G3 is an N332-directed bNAb isolated from CAP255, a participant in the CAPRISA 002 cohort, at 149 weeks post-infection (wpi). Six key antibody intermediates were selected from the CAP255.G3 lineage arm between 17 and 47 wpi, based on their position on a phylogenetic tree and because they contained mutations that were present in broad members of the lineage. We hypothesized that these intermediates would exhibit breadth similar to CAP255.G3. The intermediates were tested against a panel of eight autologous and six heterologous pseudoviruses using a TZM-bl neutralisation assay. The sequence identity of the first heavy chain complementarity-determining region (CDRH1) of CAP255.G3 differed from the closest intermediate and therefore, a CDRH1 chimera was constructed to determine if the CDRH1 from CAP255.G3 affected neutralisation activity. Later intermediates from 39 and 47 wpi, had moderate neutralisation activity against the autologous pseudoviruses, but only theintermediate closest to CAP255.G3 had limited neutralising activity against the heterologous pseudoviruses. Although the CDRH1 chimera had increased neutralisation activity against the heterologous viruses relative to the intermediates, it was less broad and potent than CAP255.G3. This indicates that additional affinity maturation between 47 and 149 wpi, at sites outside of the CDRH1, was required for the development of neutralisation breadth in the CAP255.G3 lineage arm..