Biology subjects

Hwa, S.-H.

Publications and source records attributed to Hwa, S.-H..

4 recordsLinked to original sources

bioRxiv2022

HIV skews the SARS-CoV-2 B cell response toward an extrafollicular maturation pathway

BackgroundHIV infection dysregulates the B cell compartment, affecting memory B cell formation and the antibody response to infection and vaccination. Understanding the B cell response to SARS-CoV-2 in people living with HIV (PLWH) may explain the increased morbidity, reduced vaccine efficacy, reduced clearance, and intra-host evolution of SARS-CoV-2 observed in some HIV-1 coinfections. MethodsWe compared B cell responses to COVID-19 in PLWH and HIV negative (HIV-ve) patients in a cohort recruited in Durban, South Africa, during the first pandemic wave in July 2020 using detailed flow cytometry phenotyping of longitudinal samples with markers of B cell maturation, homing and regulatory features. ResultsThis revealed a coordinated B cell response to COVID-19 that differed significantly between HIV-ve and PLWH. Memory B cells in PLWH displayed evidence of reduced germinal center (GC) activity, homing capacity and class-switching responses, with increased PD-L1 expression, and decreased Tfh frequency. This was mirrored by increased extrafollicular (EF) activity, with dynamic changes in activated double negative (DN2) and activated naive B cells, which correlated with anti-RBD-titres in these individuals. An elevated SARS-CoV-2 specific EF response in PLWH was confirmed using viral spike and RBD bait proteins. ConclusionsDespite similar disease severity, these trends were highest in participants with uncontrolled HIV, implicating HIV in driving these changes. EF B cell responses are rapid but give rise to lower affinity antibodies, less durable long-term memory, and reduced capacity to adapt to new variants. Further work is needed to determine the long-term effects of HIV on SARS-CoV-2 immunity, particularly as new variants emerge. FundingThis work was supported by a grant from the Wellcome Trust to the Africa Health Research Institute (Wellcome Trust Strategic Core Award [grant number 201433/Z/16/Z]). Additional funding was received from the South African Department of Science and Innovation through the National Research Foundation (South African Research Chairs Initiative, [grant number 64809]), and the Victor Daitz Foundation.

immunology↗

bioRxiv2021

SARS-CoV-2 cell-to-cell spread occurs rapidly and is insensitive to antibody neutralization

Viruses increase the efficiency of close-range transmission between cells by manipulating cellular physiology and behavior, and SARS-CoV-2 uses cell fusion as one mechanism for cell-to-cell spread. Here we visualized infection using time-lapse microscopy of a human lung cell line and used live virus neutralization to determine the sensitivity of SARS-CoV-2 cell-to-cell spread to neutralizing antibodies. SARS-CoV-2 infection rapidly led to cell fusion, forming multinucleated cells with clustered nuclei which started to be detected at 6h post-infection. To compare sensitivity of cell-to-cell spread to neutralization, we infected either with cell-free virus or with single infected cells expressing on their surface the SARS-CoV-2 spike protein. We tested two variants of SARS-CoV-2: B.1.117 containing only the D614G substitution, and the escape variant B.1.351. We used the much smaller area of single infected cells relative to infection foci to exclude any input infected cells which did not lead to transmission. The monoclonal antibody and convalescent plasma we tested neutralized cell-free SARS-CoV-2, with the exception of B.1.351 virus, which was poorly neutralized with plasma from non-B.1.351 infections. In contrast, cell-to-cell spread of SARS-CoV-2 showed no sensitivity to monoclonal antibody or convalescent plasma neutralization. These observations suggest that, once cells are infected, SARS-CoV-2 may be more difficult to neutralize in cell types and anatomical compartments permissive for cell-to-cell spread.

microbiology↗

bioRxiv2021

Development of highly potent neutralising nanobodies against multiple SARS-CoV-2 variants including the variant of concern B.1.351

The pathogenic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic. During the years of 2020-2021, millions of humans have died due to SARS-CoV-2 infection and severe economic damage to the global economy has occurred. Unprecedented rapid investments in vaccine development have been made to counter the spread of SARS-CoV-2 among humans. While vaccines are a key pillar of modern medicine, SARS-CoV-2 has mutated as it spread among humans. Vaccines previously developed and approved by regulators are becoming less effective against new variants. One variant of SARS-CoV-2 known as B.1.351 that was first reported to be present in South Africa significantly reduces the efficacy of vaccines developed to date. Therapeutic options that work against the B.1.351 variant are therefore urgently needed to counteract reduced vaccine efficacy. We present here the discovery of recombinant alpaca antibodies that neutralise live virus of B.1.351 and other SARS-CoV-2 variants potently. The antibodies described here may be a useful tool for clinicians who are treating patients infected with B.1.351 and other SARS-CoV-2 for which there is currently no known highly effective treatment.

immunology↗

bioRxiv2021

Aggregated Mycobacterium tuberculosis enhances the inflammatory response

Mycobacterium tuberculosis (Mtb) readily aggregates in culture and Mtb aggregates in the lung were observed in experimental Mtb infection. However, the physiological consequences of Mtb aggregation are incompletely understood. Here we examined the human macrophage transcriptional response to aggregated Mtb relative to infection with non-aggregated single or multiple bacilli per host cell. Infection with aggregated Mtb led to an early upregulation of pro-inflammatory associated genes and enhanced TNF signaling via the NF{kappa}B pathway. Both these pathways were significantly upregulated relative to infection with single bacilli, and TNF signaling was also significantly elevated relative to infection with multiple non-aggregated Mtb. Secretion of TNF and downstream cytokines were also enhanced. On a longer timescale, aggregate infection led to overall increased acidification per macrophage and a high proportion of death in these cells after aggregate phagocytosis. Host cell death did not occur when Mtb aggregates were heat killed despite such clumps being readily picked up. To validate that Mtb aggregates do occur in the human lung, we document Mtb aggregates surrounding a cavity in a human TB lesion. Aggregates may therefore be present in some lesions and elicit a stronger inflammatory response resulting in recruitment of additional phagocytes and their subsequent death, potentially leading to necrosis and transmission.

microbiology↗