Gonadal androgens are associated with decreased type I interferon production by pDCs and increased IgG titres to BNT162b2 following co-vaccination with live attenuated influenza vaccine in adolescents (preprint)

mRNA vaccine technologies introduced following the SARS-CoV-2 pandemic have highlighted the need to better understand the interaction of adjuvants and the early innate immune response. Interferon type I (IFN-I) is an integral part of this early innate response and can prime several components of the adaptive immune response. Females are widely reported to respond better than males to seasonal tri- and quad-valent influenza vaccines. Plasmacytoid dendritic cells (pDCs) are the primary cell type responsible for IFN-I production and female pDCs produce more IFN-I than male pDCs since the upstream receptor TLR7 is encoded by the X-chromosome and is biallelically expressed by up to 30% of female immune cells. Additionally, the TLR7 promoter contains putative androgen response elements and androgens have been reported to suppress pDC IFN-I in-vitro. Unexpectedly, therefore, we recently observed that male adolescents mount stronger antibody responses to the Pfizer BNT162b2 mRNA vaccine than female adolescents after controlling for natural SARS-CoV-2 infection. We here examined pDC behaviour in this cohort to determine the impact of IFN-I on anti-Spike and anti-receptor-binding domain titres to BNT162b2. Through LASSO modelling we determined that serum free testosterone was associated with reduced pDC IFN-I but, contrary to the well-described immunosuppressive role for androgens, the more potent androgen dihydrotestosterone was associated with increased IgG titres to BNT162b2. Also unexpectedly, we observed that co-vaccination with live-attenuated influenza vaccine boosted the magnitude of IgG responses to BNT162b2. Together these data support a model where systemic IFN-I increased vaccine-mediated immune responses, but for vaccines with intracellular stages, modulation of the local IFN-I response may alter antigen longevity and consequently vaccine-driven immunity.

Age- and sex-specific differences in immune responses to BNT162b2 COVID-19 and live-attenuated influenza vaccines in UK adolescents (preprint)

Key to understanding COVID-19 correlates of protection is assessing vaccine-induced immunity in different demographic groups. Sex- and age-specific immune differences have a wide impact on outcomes from infections and immunisations. Typically, adult females make stronger immune responses and have better disease outcomes but suffer more adverse events following vaccination and are more prone to autoimmune disease. To understand better the mechanisms underlying these differences in vaccine responses, we studied immune responses to two doses of BNT162b2 Pfizer COVID-19 vaccine in an adolescent cohort (n=34, ages 12-16), an age group previously shown to make significantly greater immune responses to the same vaccine compared to young adults. At the same time, we were able to evaluate immune responses to the co-administered live attenuated influenza vaccine, which has been shown to induce stronger immune responses in adult females. Blood samples from 34 adolescents taken pre- and post-vaccination with COVID-19 and influenza vaccines were assayed for SARS-CoV-2-specific IgG and neutralising antibodies, and cellular immunity specific for SARS-CoV-2 and endemic betacoronaviruses. IgG targeting influenza lineages contained in the influenza vaccine was also assessed. As previously demonstrated, total IgG responses to SARS-CoV-2 Spike antigens were significantly higher among vaccinated adolescents compared to adults (aged 32-52) who received the BNT162b2 vaccine (comparing infection-naive, 49,696 vs 33,339; p=0.03; comparing SARS-CoV-2 previously-infected, 743,691 vs 269,985; p<0.0001) by MSD v-plex assay. However, unexpectedly, antibody responses to BNT162b2 and the live-attenuated influenza vaccine were not higher among female adolescents compared to males; among infection-naive adolescents, antibody responses to BNT162b2 were higher in males than females (62,270 vs 36,951 p=0.008). No sex difference was identified in vaccinated adults. These unexpected findings may result from the introduction of novel mRNA vaccination platforms, generating patterns of immunity divergent from established trends, and providing new insights into what might be protective following COVID-19 vaccination.

Evaluation of QuantiFERON SARS-CoV-2 interferon-γ release assay following SARS-CoV-2 infection and vaccination (preprint)

Background: T cells are important in preventing severe disease from SARS-CoV-2, but scalable and field-adaptable alternatives to expert T cell assays are needed. The interferon-gamma release assay QuantiFERON platform was developed to detect T cell responses to SARS-CoV-2 from whole blood with relatively basic equipment and flexibility of processing timelines. Methods: 48 participants with different infection and vaccination backgrounds were recruited. Whole blood samples were analysed using the QuantiFERON SARS-CoV-2 assay in parallel with the well-established Protective Immunity from T Cells in Healthcare workers (PITCH) ELISpot, which can evaluate spike-specific T cell responses. Aims: The primary aims of this cross-sectional observational cohort study were to establish if the QuantiFERON SARS-Co-V-2 assay could discern differences between specified groups and to assess the sensitivity of the assay compared to the PITCH ELISpot. Findings: The QuantiFERON SARS-CoV-2 distinguished acutely infected individuals (12-21 days post positive PCR) from naive individuals (p< 0.0001) with 100% sensitivity and specificity for SARS-CoV-2 T cells, whilst the PITCH ELISpot had reduced sensitivity (62.5%) for the acute infection group. Sensitivity with QuantiFERON for previous infection was 12.5% (172-444 days post positive test) and was inferior to the PITCH ELISpot (75%). Although the QuantiFERON assay could discern differences between unvaccinated and vaccinated individuals (55-166 days since second vaccination), the latter also had reduced sensitivity (55.5%) compared to the PITCH ELISpot (66.6%). Conclusion: The QuantiFERON SARS-CoV-2 assay showed potential as a T cell evaluation tool soon after SARS-CoV-2 infection but has lower sensitivity for use in reliable evaluation of vaccination or more distant infection.

Further antibody escape by Omicron BA.4 and BA.5 from vaccine and BA.1 serum (preprint)

The Omicron lineage of SARS-CoV-2, first described in November 2021, spread rapidly to become globally dominant and has split into a number of sub-lineages. BA.1 dominated the initial wave but has been replaced by BA.2 in many countries. Recent sequencing from South Africa's Gauteng region uncovered two new sub-lineages, BA.4 and BA.5 which are taking over locally, driving a new wave. BA.4 and BA.5 contain identical spike sequences and, although closely related to BA.2, contain further mutations in the receptor binding domain of spike. Here, we study the neutralization of BA.4/5 using a range of vaccine and naturally immune serum and panels of monoclonal antibodies. BA.4/5 shows reduced neutralization by serum from triple AstraZeneca or Pfizer vaccinated individuals compared to BA.1 and BA.2. Furthermore, using serum from BA.1 vaccine breakthrough infections there are likewise, significant reductions in the neutralization of BA.4/5, raising the possibility of repeat Omicron infections.

Durability of ChAdOx1 nCov-19 (AZD1222) vaccination in people living with HIV - responses to SARS-CoV-2, variants of concern and circulating coronaviruses (preprint)

Duration of protection from SARS-CoV-2 infection in people with HIV (PWH) following vaccination is unclear. In a sub-study of the phase 2/3 the COV002 trial (NCT04400838), 54 HIV positive male participants on antiretroviral therapy (undetectable viral loads, CD4+ T cells >350 cells/ul) received two doses of ChAdOx1 nCoV-19 (AZD1222) 4-6 weeks apart and were followed for 6 months. Responses to vaccination were determined by serology (IgG ELISA and MesoScale Discovery (MSD)), neutralisation, ACE-2 inhibition, gamma interferon ELISpot, activation-induced marker (AIM) assay and T cell proliferation. We show that 6 months after vaccination the majority of measurable immune responses were greater than pre-vaccination baseline, but with evidence of a decline in both humoral and cell mediated immunity. There was, however, no significant difference compared to a cohort of HIV-uninfected individuals vaccinated with the same regimen. Responses to the variants of concern were detectable, although were lower than wild type. Pre-existing cross-reactive T cell responses to SARS-CoV-2 spike were associated with greater post-vaccine immunity and correlated with prior exposure to beta coronaviruses. These data support the on-going policy to vaccinate PWH against SARS-CoV-2, and underpin the need for long-term monitoring of responses after vaccination.

Safety and Immunogenicity of the ChAdox1 nCoV-19 (AZD1222) Vaccine Against SARS-CoV-2 in HIV Infection (preprint)

Background: The ChAdOx1 nCoV-19 (AZD1222) vaccine is immunogenic and protects against COVID-19. However, data on vaccine immunogenicity are needed for the 40 million people living with HIV (PWH), who may have less functional immunity and more associated co-morbidities than the general population. Methods: Between the 5th and 24th November 2020, 54 adults with HIV, aged 18-55 years, were enrolled into a single arm open label vaccination study within the protocol of the larger phase 2/3 COV002 trial. A prime-boost regimen of ChAdOx1 nCoV-19, with two doses (5 × 1010 vp) was given 4-6 weeks apart. All participants were on antiretroviral therapy (ART) with undetectable plasma HIV viral loads and CD4+ T cell counts >350 cells/µl at enrolment. Data were captured on adverse events. Humoral responses were measured by anti-spike IgG ELISA and antibody-mediated live virus neutralisation. Cell-mediated immune responses were measured by ex-vivo interferon-γ enzyme-linked immunospot assay (ELISpot) and T cell proliferation. All outcomes were compared with a HIV uninfected group from the main COV002 study.Findings: 54 participants with HIV (median age 42.5 years (IQR 37.2-49.8)) received two doses of ChAdOx1 nCoV-19. Median CD4+ T cell count at enrolment was 694 cells/µl (IQR 562-864). Results are reported for 56 days of follow-up. Local and systemic reactions occurring during the first 7 days after prime vaccination included pain at the injection site (49%), fatigue (47%), headache (47%), malaise (34%), chills (23%), and muscle or (36%) joint pain (9%), the frequencies of which were similar to the HIV-negative participants. There were no serious adverse events. Anti-spike IgG responses by ELISA peaked at Day 42 (median 1440 ELISA units, IQR 704-2728) and were sustained out to Day 56. There was no correlation with CD4+ T cell count or age and the magnitude of the anti-spike IgG response at Day 56 (P>0.05 for both). ELISpot and T cell proliferative responses peaked between Day 14 and 28 after prime and were sustained through to Day 56. When compared to participants without HIV there was no statistical difference in magnitude or persistence of SARS-CoV-2 spike-specific humoral or cellular responses (P>0.05 for all analyses).Interpretation: In this study of PWH, vaccination with ChAdOx1 nCoV-19 was well tolerated and there was no difference in humoral and cell-mediated immune responses compared to an adult cohort without HIV who received the same vaccination regime. Trial Registration: Trial Registration number is NCT04400838. Funding: UK Research and Innovation, National Institutes for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midlands NIHR Clinical Research Network, and AstraZeneca. The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.Declaration of Interest: Oxford University has entered into a partnership with AstraZeneca for further development of ChAdOx1 nCoV-19 (AZD1222). AstraZeneca reviewed the data from the study and the final manuscript before 474 submission, but the authors retained editorial control. SCG is cofounder of Vaccitech (a collaborator in the early development of this vaccine candidate) and named as an inventor on a patent covering use of ChAdOx1-vectored vaccines (PCT/GB2012/000467) and a patent application covering this SARS-CoV-2 vaccine. TL is named as an inventor on a patent application covering this SARS-CoV-2 vaccine and was consultant to Vaccitech. PMF is a consultant to Vaccitech. AJP is Chair of the UK Department of Health and Social Care’s JCVI, but does not participate in policy advice on coronavirus vaccines, and is a member of the WHO Strategic Advisory Group of Experts (SAGE). AVSH is a cofounder of and consultant to Vaccitech and is named as an inventor on a patent covering design and use of ChAdOx1-vectored vaccines (PCT/GB2012/000467).Ethical Approval: Written informed consent was obtained from all participants, and the trial was done in accordance with the principles of the Declaration of Helsinki and Good Clinical Practice. This study was approved in the UK by the Medicines and Healthcare products Regulatory Agency (reference 21584/0424/001-0001) and the South Central Berkshire Research Ethics Committee (reference 20/SC/0145). Vaccine use was authorised by Genetically Modified Organisms Safety Committees at each participating site.

Vaccine-induced immunity provides more robust heterotypic immunity than natural infection to emerging SARS-CoV-2 variants of concern. (preprint)

Both natural infection with SARS-CoV-2 and immunization with a number of vaccines induce protective immunity. However, the ability of such immune responses to recognize and therefore protect against emerging variants is a matter of increasing importance. Such variants of concern (VOC) include isolates of lineage B1.1.7, first identified in the UK, and B1.351, first identified in South Africa. Our data confirm that VOC, particularly those with substitutions at residues 484 and 417 escape neutralization by antibodies directed to the ACE2-binding Class 1 and the adjacent Class 2 epitopes but are susceptible to neutralization by the generally less potent antibodies directed to Class 3 and 4 epitopes on the flanks RBD. To address this potential threat, we sampled a SARS-CoV-2 uninfected UK cohort recently vaccinated with BNT162b2 (Pfizer-BioNTech, two doses delivered 18-28 days apart), alongside a cohort naturally infected in the first wave of the epidemic in Spring 2020. We tested antibody and T cell responses against a reference isolate (VIC001) representing the original circulating lineage B and the impact of sequence variation in these two VOCs. We identified a reduction in antibody neutralization against the VOCs which was most evident in the B1.351 variant. However, the majority of the T cell response was directed against epitopes conserved across all three strains. The reduction in antibody neutralization was less marked in post-boost vaccine-induced than in naturally-induced immune responses and could be largely explained by the potency of the homotypic antibody response. However, after a single vaccination, which induced only modestly neutralizing homotypic antibody titres, neutralization against the VOCs was completely abrogated in the majority of vaccinees. These data indicate that VOCs may evade protective neutralising responses induced by prior infection, and to a lesser extent by immunization, particularly after a single vaccine, but the impact of the VOCs on T cell responses appears less marked. The results emphasize the need to generate high potency immune responses through vaccination in order to provide protection against these and other emergent variants. We observed that two doses of vaccine also induced a significant increase in binding antibodies to spike of both SARS-CoV-1 & MERS, in addition to the four common coronaviruses currently circulating in the UK. The impact of antigenic imprinting on the potency of humoral and cellular heterotypic protection generated by the next generation of variant-directed vaccines remains to be determined.

Natural and vaccine-induced antibody and cellular responses against emerging SARS-CoV-2 variants of concern (preprint)

Both natural infection with SARS-CoV-2 and immunization with a number of vaccines induce protective immunity. However, the ability of such immune responses to recognize and therefore protect against emerging variants is a matter of increasing importance. Such variants of concern (VOC) include isolates of lineage B1.1.7, first identified in the UK, and B1.351, first identified in South Africa. Our data confirm that VOC, particularly those with substitutions at residues 484 and 417 escape neutralization by antibodies directed to the ACE2-binding Class 1 and the adjacent Class 2 epitopes but are susceptible to neutralization by the generally less potent antibodies directed to Class 3 and 4 epitopes on the flanks RBD. To address this potential threat, we sampled a SARS-CoV-2 uninfected UK cohort recently vaccinated with BNT162b2 (Pfizer-BioNTech, two doses delivered 18-28 days apart), alongside a cohort naturally infected in the first wave of the epidemic in Spring 2020. We tested antibody and T cell responses against a reference isolate (VIC001) representing the original circulating lineage B and the impact of sequence variation in these two VOCs. We identified a reduction in antibody neutralization against the VOCs which was most evident in the B1.351 variant. However, the majority of the T cell response was directed against epitopes conserved across all three strains. The reduction in antibody neutralization was less marked in post-boost vaccine-induced than in naturally-induced immune responses and could be largely explained by the potency of the homotypic antibody response. However, after a single vaccination, which induced only modestly neutralizing homotypic antibody titres, neutralization against the VOCs was completely abrogated in the majority of vaccinees. These data indicate that VOCs may evade protective neutralising responses induced by prior infection, and to a lesser extent by immunization, particularly after a single vaccine, but the impact of the VOCs on T cell responses appears less marked. The results emphasize the need to generate high potency immune responses through vaccination in order to provide protection against these and other emergent variants. We observed that two doses of vaccine also induced a significant increase in binding antibodies to spike of both SARS-CoV-1 & MERS, in addition to the four common coronaviruses currently circulating in the UK. The impact of antigenic imprinting on the potency of humoral and cellular heterotypic protection generated by the next generation of variant-directed vaccines remains to be determined.

T cell assays differentiate clinical and subclinical SARS-CoV-2 infections from cross-reactive antiviral responses (preprint)

A major issue in identification of protective T cell responses against SARS-CoV-2 lies in distinguishing people infected with SARS-CoV-2 from those with cross-reactive immunity generated by exposure to other coronaviruses. We characterised SARS-CoV-2 T cell immune responses in 168 PCR-confirmed SARS-CoV-2 infected subjects and 118 seronegative subjects without known SARS-CoV-2 exposure using a range of T cell assays that differentially capture immune cell function. Strong ex vivo ELISpot and proliferation responses to multiple antigens (including M, NP and ORF3) were found in those who had been infected by SARS-CoV-2 but were rare in pre-pandemic and unexposed seronegative subjects. However, seronegative doctors with high occupational exposure and recent COVID-19 compatible illness showed patterns of T cell responses characteristic of infection, indicating that these readouts are highly sensitive. By contrast, over 90% of convalescent or unexposed people showed proliferation and cellular lactate responses to spike subunits S1/S2, indicating pre-existing cross-reactive T cell populations. The detection of T cell responses to SARS-CoV-2 is therefore critically dependent on the choice of assay and antigen. Memory responses to specific non-spike proteins provides a method to distinguish recent infection from pre-existing immunity in exposed populations.

De Novo Discovery of High Affinity Peptide Binders for the SARS-CoV-2 Spike Protein (preprint)

The beta-coronavirus SARS-CoV-2 has caused a global pandemic. Affinity reagents targeting the SARS-CoV-2 spike protein, the most exposed surface structure of the virus, are of interest for the development of therapeutics and diagnostics. We used affinity selection-mass spectrometry for the rapid discovery of synthetic high affinity peptide binders for the receptor binding domain (RBD) of the SARS-CoV-2 spike protein. From library screening with 800 million synthetic peptides, we identified three sequences with nanomolar affinities (dissociation constants of 80 to 970 nM) for RBD and selectivity over human serum proteins. Picomolar RBD concentrations in biological matrix could be detected using the biotinylated lead peptide in ELISA format. These peptides might associate with the SARS-CoV-2-spike-RBD at a site unrelated to ACE2 binding, making them potential orthogonal reagents for sandwich immunoassays. We envision our discovery as a robust starting point for the development of SARS-CoV-2 diagnostics or conjugates for virus directed delivery of therapeutics.

Broad and strong memory CD4+ and CD8+ T cells induced by SARS-CoV-2 in UK convalescent COVID-19 patients. (preprint)

COVID-19 is an ongoing global crisis in which the development of effective vaccines and therapeutics will depend critically on understanding the natural immunity to the virus, including the role of SARS-CoV-2-specific T cells. We have conducted a study of 42 patients following recovery from COVID-19, including 28 mild and 14 severe cases, comparing their T cell responses to those of 16 control donors. We assessed the immune memory of T cell responses using IFN{gamma} based assays with overlapping peptides spanning SARS-CoV-2 apart from ORF1. We found the breadth, magnitude and frequency of memory T cell responses from COVID-19 were significantly higher in severe compared to mild COVID-19 cases, and this effect was most marked in response to spike, membrane, and ORF3a proteins. Total and spike-specific T cell responses correlated with the anti-Spike, anti-Receptor Binding Domain (RBD) as well as anti-Nucleoprotein (NP) endpoint antibody titre (p<0.001, <0.001 and =0.002). We identified 39 separate peptides containing CD4+ and/or CD8+ epitopes, which strikingly included six immunodominant epitope clusters targeted by T cells in many donors, including 3 clusters in spike (recognised by 29%, 24%, 18% donors), two in the membrane protein (M, 32%, 47%) and one in the nucleoprotein (Np, 35%). CD8+ responses were further defined for their HLA restriction, including B*4001-restricted T cells showing central memory and effector memory phenotype. In mild cases, higher frequencies of multi-cytokine producing M- and NP-specific CD8+ T cells than spike-specific CD8+ T cells were observed. They furthermore showed a higher ratio of SARS-CoV-2-specific CD8+ to CD4+ T cell responses. Immunodominant epitope clusters and peptides containing T cell epitopes identified in this study will provide critical tools to study the role of virus-specific T cells in control and resolution of SARS-CoV-2 infections. The identification of T cell specificity and functionality associated with milder disease, highlights the potential importance of including non-spike proteins within future COVID-19 vaccine design.