Atypical B cells and impaired SARS-CoV-2 neutralisation following booster vaccination in the elderly.

Age is a major risk factor for hospitalization and death after SARS-CoV-2 infection, even in vaccinees. Suboptimal responses to a primary vaccination course have been reported in the elderly, but there is little information regarding the impact of age on responses to booster third doses. Here we show that individuals 70 or older who received a primary two dose schedule with AZD1222 and booster third dose with mRNA vaccine achieved significantly lower neutralizing antibody responses against SARS-CoV-2 spike pseudotyped virus compared to those younger than 70. One month after the booster neither the concentration of serum binding anti spike IgG antibody, nor the frequency of spike-specific B cells showed differences by age grouping. However, the impaired neutralization potency and breadth post-third dose in the elderly was associated with enrichment of circulating "atypical" spike-specific B cells expressing CD11c and FCRL5. Single cell RNA sequencing confirmed an expansion of TBX21-, ITGAX-expressing B cells in the elderly that enriched for B cell activation/receptor signalling pathway genes. Importantly we also observed impaired T cell responses to SARS-CoV-2 spike peptides in the elderly post-booster, both in terms of IFNgamma and IL2 secretion, as well as a decrease in T cell receptor signalling pathway genes. This expansion of atypical B cells and impaired T cell responses may contribute to the generation of less affinity-matured antibodies, with lower neutralizing capacity post-third dose in the elderly. Altogether, our data reveal the extent and potential mechanistic underpinning of the impaired vaccine responses present in the elderly after a booster dose, contributing to their increased susceptibility to COVID-19 infection.

Accelerated waning of the humoral response to SARS-CoV-2 vaccines in obesity

Obesity is associated with an increased risk of severe Covid-19. However, the effectiveness of SARS-CoV-2 vaccines in people with obesity is unknown. Here we studied the relationship between body mass index (BMI), hospitalization and mortality due to Covid-19 amongst 3.5 million people in Scotland. Vaccinated people with severe obesity (BMI>40 kg/m2) were significantly more likely to experience hospitalization or death from Covid-19. Excess risk increased with time since vaccination. To investigate the underlying mechanisms, we conducted a prospective longitudinal study of the immune response in a clinical cohort of vaccinated people with severe obesity. Compared with normal weight people, six months after their second vaccine dose, significantly more people with severe obesity had unquantifiable titres of neutralizing antibody against authentic SARS-CoV-2 virus, reduced frequencies of antigen-experienced SARS-CoV-2 Spike-binding B cells, and a dissociation between anti-Spike antibody levels and neutralizing capacity. Neutralizing capacity was restored by a third dose of vaccine, but again declined more rapidly in people with severe obesity. We demonstrate that waning of SARS-CoV-2 vaccine-induced humoral immunity is accelerated in people with severe obesity and associated with increased hospitalization and mortality from breakthrough infections. Given the prevalence of obesity, our findings have significant implications for global public health.

Antibody responses to AZD1222 vaccination in West Africa

BackgroundThere are no real world data on vaccine elicited neutralising antibody responses for the worlds most widely used vaccine, AZD1222, in African populations following scale up. Here, we measured i) baseline SARS-CoV-2 seroprevalence and levels of protective neutralizing antibodies prior to vaccination rollout using both flow cytometric based analysis of binding antibodies to nucleocapsid (N), coupled with virus neutralisation approaches and ii) neutralizing antibody responses to VOC prior to vaccination (January 2021) and after two-doses of AZD1222 vaccine administered with a 12 week interval in Lagos, Nigeria - a period when the Delta variant was circulating. MethodsHealth workers at multiple sites in Lagos were recruited to the study. For binding antibody measurement, IgG antibodies against SARS-COV-2 Wuhan-1 receptor-binding domain (RBD), trimeric spike protein (S), nucleocapsid protein (N) and Omicron S1 were measured using the Luminex-based SARS-CoV-2-IgG assay by flow cytometry. For plasma neutralising antibody measurement, SARS-CoV-2 lentiviral pseudovirus (PV) were prepared by transfecting 293T cells with Wuhan-614G wild type (WT), B.1.617.2 (Delta) and BA.1 (Omicron) plasmids in conjunction with HIV-1 expression vectors and luciferase encoding genome flanked by LTRs. We performed serial plasma dilutions from each time point and mixed plasma with PV before infecting HeLa-ACE2 cell lines, reading out luminescence and calculating ID50 (reciprocal dilution of sera required to inhibit 50% of PV infection). ResultsOur underlying study population receiving at least one dose of vaccine comprised 140 participants with a median age of 40 (interquartile range: 33, 48). 62/140 (44%) participants were anti-N IgG positive prior to administration of first vaccine dose. 49 had plasma samples available at baseline prior to vaccination and at two follow-up timepoints post two dose vaccination for neutralization assays. Half of the participants, 25/49 (51%) were IgG anti-N positive at baseline. Of the 24 individuals anti-N Ab negative at baseline, 12/24 had ID50 above the cut-off of 20. In these individuals, binding antibodies to S were also detectable, and neutralisation correlated with IgG anti-S, suggesting waning of N antibody after infection. Overall, neutralizing Ab titres to WT 1 month after second dose were 2579 and at 3 months post second-dose were 1695. As expected, lower levels of neutralization were observed against the Delta GMT 549 and Omicron variants 269 at 1 month. Positive anti-N IgG Ab status at baseline was associated with significantly higher titres of neutralizing antibodies following vaccination across all tested VOC. Those with anti-N Abs present at baseline did not experience waning of responses between months 1 and 3 post second dose. When data were analysed for negative anti-N IgG status at any timepoint, there was a significant decline in neutralization and binding antibodies between 1 month and 3 months post second-dose. The GMT in these individuals for Delta and Omicron was approximately 100, nearly a log lower in comparison to WT. We tested anti-N IgG in subjects who were anti-N IgG negative at baseline (n=78) and became positive between 1- and 3-months post second dose and found 7/49 (14%) with de-novo infection, with one additional participant demonstrating both reinfection and breakthrough infection to yield a total breakthrough rate of 8/49 (16%). Neutralising and binding Ab titres 1 month post vaccine, prior to breakthrough, were not associated with breakthrough infection. Neutralizing titres were higher at the last time point in individuals who had experienced vaccine breakthrough infection (with no evidence of infection prior to vaccine), indicating a boosting effect of infection in addition to vaccine. However, neutralisation and binding S antibodies against Omicron were low in those with either prior exposure or infection following two dose AZD1222. ConclusionsAZD1222 is immunogenic in this real world west African cohort with significant background seroprevalence and incidence of breakthrough infection over a short time period. Prior infection and breakthrough infection induced higher anti-SARS-CoV-2 Ab responses at 3 months post vaccine against all widely circulating VOC. However, responses to Omicron BA.1 were low at three months regardless of hybrid immunity from prior exposure or breakthrough infection. Booster doses after AZD1222 should be considered in the African setting, even after natural infection, as future variants may be more pathogenic as well as immune evasive in the context of waning immunity.

Critical care workers have lower seroprevalence of SARS-CoV-2 IgG compared with non-patient facing staff in first wave of COVID19.

With the first 2020 surge of the COVID-19 pandemic, many health care workers (HCW) were re-deployed to critical care environments to support intensive care teams to look after high numbers of patients with severe COVID-19. There was considerable anxiety of increased risk of COVID19 for staff working in these environments. Using a multiplex platform to assess serum IgG responses to SARS-CoV-2 N, S and RBD proteins, and detailed symptom reporting, we screened over 500 HCW (25% of the total workforce) in a quaternary level hospital to explore the relationship between workplace and evidence of exposure to SARS-CoV-2. Whilst 45% of the cohort reported symptoms that they consider may have represented COVID-19, overall seroprevalence was 14% with anosmia and fever being the most discriminating symptoms for seropositive status. There was a significant difference in seropositive status between staff working in clinical and non-clinical roles (9% patient facing critical care, 15% patient facing non-critical care, 22% nonpatient facing). In the seropositive cohort, symptom severity increased with age for men and not for women. In contrast, there was no relationship between symptom severity and age or sex in the seronegative cohort reporting possible COVID-19 symptoms. Of the 12 staff screened PCR positive (10 symptomatic), 3 showed no evidence of seroconversion in convalescence. ConclusionThe current approach to Personal Protective Equipment (PPE) appears highly effective in protecting staff from patient acquired infection in the critical care environment including protecting staff managing interhospital transfers of COVID-19 patients. The relationship between seroconversion and disease severity in different demographics warrants further investigation. Longitudinally paired virological and serological surveillance, with symptom reporting are urgently required to better understand the role of antibody in the outcome of HCW exposure during subsequent waves of COVID-19 in health care environments.