Inhibition of respiratory pathogens Mycobacterium tuberculosis and SARS-CoV-2 by human serum and monoclonal antibodies

Antibodies are a key host immune response against pathogens. Yet the effects of antibodies on Mycobacterium tuberculosis (Mtb) at the cellular level are incompletely understood, as is the effect of HIV co-infection on antibody-mediated immunity to SARS-CoV-2. By investigating these questions at the epicenter of the HIV/TB co-epidemic in KwaZulu-Natal, South Africa, I have: 1) Cloned immunoglobulins from B cells of Mtb-exposed donors and investigated the effect of Mtb-specific polyclonal and monoclonal antibodies on infection of macrophages; 2) Characterised antibody responses in viraemic, virologically suppressed, and HIV-negative Covid-19 patients to determine whether HIV status and viraemia influence neutralization of SARS-CoV-2. Sera from TB-exposed individuals on average increased host cell survival and inhibited intracellular bacterial growth compared to non-specific control serum, although there was a wide range of individual variation. I cloned several Mtb-specific antibodies from South African donors including one which significantly inhibited intracellular bacterial growth in THP-1 monocytes and primary macrophages. I developed a live virus neutralisation assay for SARS-CoV-2 to circumvent the problem of a lentiviral pseudovirus neutralization assay being incompatible with samples containing antiretrovirals for HIV. Among Covid-19 patients, the kinetics of RBD-binding and neutralising antibodies differed little between HIV-uninfected and virologically suppressed people living with HIV (PLWH), whereas viraemic PLWH had a much lower and delayed response. In addition, I observed that plasma from individuals either previously infected with earlier variants of SARS-CoV-2 or vaccinated with AstraZeneca’s AZD1222 recombinant adenovirus vaccine showed decreases in neutralisation against newer variants of concern. Taken together, these results demonstrate that antibody-mediated immunity is relevant to the control of TB but is highly heterogeneous. Similarly, there is individual heterogeneity in the neutralisation response to SARS-CoV-2, with the latter partially determined by HIV status and suppression state

Similar Antibody Responses Against Severe Acute Respiratory Syndrome Coronavirus 2 in Individuals Living Without and With Human Immunodeficiency Virus on Antiretroviral Therapy During the First South African Infection Wave

BACKGROUND: There is limited understanding of SARS-CoV-2 pathogenesis in African populations with a high burden of infectious disease comorbidities such as HIV. The kinetics, magnitude and duration of virus-specific antibodies and the underlying B cell responses in people living with HIV (PLWH) in sub-Saharan Africa have not been fully characterized. METHODS: We longitudinally followed SARS-CoV-2 infected individuals in Durban, KwaZulu-Natal, South Africa and characterized SARS-CoV-2 receptor binding domain-specific IgM, IgG and IgA antibodies weekly for a month, and then at 3 months post diagnosis. 7/30 (41.7%) were PLWH, 83% (25/30) of which were on ART and with full HIV suppression. Potency of convalescent plasma neutralization was determined using a live virus neutralization assay and antibody secreting cell population frequencies were determined by flow cytometry. RESULTS: Similar seroconversion rates, time to peak antibody titer, peak magnitude and durability of anti-SARS-CoV-2 IgM, IgG, IgA, were observed in HIV uninfected and PLWH with complete HIV suppression on ART. In addition, similar neutralization potency against an isolate of SARS-CoV-2, circulating at the time of sampling in the first wave of SARS-CoV-2 infections in South Africa was observed in both groups. Loss of IgA was significantly associated with age (p=0.023) and a previous diagnosis of TB (p=0.018). CONCLUSIONS: Similar antibody response kinetics and neutralization potency in HIV negative and PLWH on stable ART in an African setting suggests that COVID-19 natural infections may confer comparable antibody immunity in these groups. This provides hope that COVID-19 vaccines will be effective in PLWH on stable ART

Omicron extensively but incompletely escapes Pfizer BNT162b2 neutralization

The emergence of Omicron (Pango lineage B.1.1.529), first identified in Botswana and South Africa, may compromise vaccine effectiveness and lead to re-infections1. We investigated whether Omicron escapes antibody neutralization in South Africans vaccinated with Pfizer BNT162b2. We also investigated if Omicron requires the ACE2 receptor to infect cells. We isolated and sequence confirmed live Omicron virus from an infected person in South Africa and compared plasma neutralization of Omicron relative to an ancestral SARS-CoV-2 strain, observing that Omicron still required ACE2 to infect. For neutralization, blood samples were taken soon after vaccination from participants who were vaccinated and previously infected or vaccinated with no evidence of previous infection. Neutralization of ancestral virus was much higher in infected and vaccinated versus vaccinated only participants but both groups showed a 22-fold escape from vaccine elicited neutralization by the Omicron variant. However, in the previously infected and vaccinated group, the level of residual neutralization of Omicron was similar to the level of neutralization of ancestral virus observed in the vaccination only group. These data support the notion that, provided high neutralization capacity is elicited by vaccination/boosting approaches, reasonable effectiveness against Omicron may be maintained

Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant.

BACKGROUND: Assessment of the safety and efficacy of vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in different populations is essential, as is investigation of the efficacy of the vaccines against emerging SARS-CoV-2 variants of concern, including the B.1.351 (501Y.V2) variant first identified in South Africa. METHODS: We conducted a multicenter, double-blind, randomized, controlled trial to assess the safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) in people not infected with the human immunodeficiency virus (HIV) in South Africa. Participants 18 to less than 65 years of age were assigned in a 1:1 ratio to receive two doses of vaccine containing 5×1010 viral particles or placebo (0.9% sodium chloride solution) 21 to 35 days apart. Serum samples obtained from 25 participants after the second dose were tested by pseudovirus and live-virus neutralization assays against the original D614G virus and the B.1.351 variant. The primary end points were safety and efficacy of the vaccine against laboratory-confirmed symptomatic coronavirus 2019 illness (Covid-19) more than 14 days after the second dose. RESULTS: Between June 24 and November 9, 2020, we enrolled 2026 HIV-negative adults (median age, 30 years); 1010 and 1011 participants received at least one dose of placebo or vaccine, respectively. Both the pseudovirus and the live-virus neutralization assays showed greater resistance to the B.1.351 variant in serum samples obtained from vaccine recipients than in samples from placebo recipients. In the primary end-point analysis, mild-to-moderate Covid-19 developed in 23 of 717 placebo recipients (3.2%) and in 19 of 750 vaccine recipients (2.5%), for an efficacy of 21.9% (95% confidence interval [CI], -49.9 to 59.8). Among the 42 participants with Covid-19, 39 cases (95.1% of 41 with sequencing data) were caused by the B.1.351 variant; vaccine efficacy against this variant, analyzed as a secondary end point, was 10.4% (95% CI, -76.8 to 54.8). The incidence of serious adverse events was balanced between the vaccine and placebo groups. CONCLUSIONS: A two-dose regimen of the ChAdOx1 nCoV-19 vaccine did not show protection against mild-to-moderate Covid-19 due to the B.1.351 variant. (Funded by the Bill and Melinda Gates Foundation and others; ClinicalTrials.gov number, NCT04444674; Pan African Clinical Trials Registry number, PACTR202006922165132)

Preclinical evaluation of the immunogenicity and safety of an inactivated enterovirus 71 candidate vaccine.

Human enterovirus 71 (EV71) is a significant cause of morbidity and mortality from Hand, Foot and Mouth Disease (HFMD) and neurological complications, particularly in young children in the Asia-Pacific region. There are no vaccines or antiviral therapies currently available for prevention or treatment of HFMD caused by EV71. Therefore, the development of therapeutic and preventive strategies against HFMD is of growing importance. We report the immunogenic and safety profile of inactivated, purified EV71 preparations formulated with aluminum hydroxide adjuvant in preclinical studies in mice and rabbits. In mice, the candidate vaccine formulations elicited high neutralizing antibody responses. A toxicology study of the vaccine formulations planned for human use performed in rabbits showed no vaccine-related pathological changes and all animals remained healthy. Based on these preclinical studies, Phase 1 clinical testing of the EV71 inactivated vaccine was initiated

Dose titration of EV71 antigen.

<p>Groups of BALB/c mice (n = 10) were immunized with purified inactivated EV71 with Alhydrogel, or Alhydrogel control. Symbols represent mean of reciprocal neutralizing antibody titers from groups of 10 animals ± standard deviation. Y-axis is plotted on a logarithmic scale. Dotted line shows titer of 128 (7 log₂).</p

Seroconversion rates in BALB/c mice immunized with purified inactivated EV71.

a<p>PBST = Phosphate Buffered Saline + 0.002% (v/v) Tween 80, buffer base for purified inactivated EV71.</p><p>Mice were immunized with inactivated virus with or without Alhydrogel at 28, 42 and 56 days post primary immunization. Seroconversion is defined as a neutralizing antibody titre of ≥128.</p

Muscular lesions at the site of injection in rabbit toxicological study, 2 days after the last immunization.

a<p>Values shown under total are the total number of observations of muscle degeneration with and without MNC/eosinophil infiltration.</p>b<p>The Alhydrogel Placebo group received an Alhydrogel-only adjuvant formulation.</p

Kinetics of serum neutralizing antibody responses to EV71 with or without adjuvant.

<p>Groups of BALB/c mice (n = 8) were immunized with purified inactivated EV71 with or without Alhydrogel, PBST-only control, or Alhydrogel control. Symbols represent mean of reciprocal neutralizing antibody titers from groups of 8 animals ± standard deviation. Y-axis is plotted on a logarithmic scale. Dotted line shows titer of 128 (7 log₂).</p

Seroconversion rates following varying doses of purified inactivated EV71.

<p>BALB/c mice were immunized with purified inactivated EV71 virus with Alhydrogel, at 28 days and 56 days post primary immunization. Seroconversion is defined as a neutralizing antibody titre of ≥128.</p