SARS-CoV-2 BA.1 variant is neutralized by vaccine booster-elicited serum but evades most convalescent serum and therapeutic antibodies

SARS-CoV-2 ferritin nanoparticle vaccines produce hyperimmune equine sera with broad sarbecovirus activity

The rapid emergence of SARS-CoV-2 variants of concern (VoC) and the threat of future zoonotic sarbecovirus spillover emphasizes the need for broadly protective next-generation vaccines and therapeutics. We utilized SARS-CoV-2 spike ferritin nanoparticle (SpFN), and SARS-CoV-2 receptor binding domain ferritin nanoparticle (RFN) immunogens, in an equine model to elicit hyperimmune sera and evaluated its sarbecovirus neutralization and protection capacity. Immunized animals rapidly elicited sera with the potent neutralization of SARS-CoV-2 VoC, and SARS-CoV-1 pseudoviruses, and potent binding against receptor binding domains from sarbecovirus clades 1b, 1a, 2, 3, and 4. Purified equine polyclonal IgG provided protection against Omicron XBB.1.5 virus in the K18-hACE2 transgenic mouse model. These results suggest that SARS-CoV-2-based nanoparticle vaccines can rapidly produce a broad and protective sarbecovirus response in the equine model and that equine serum has therapeutic potential against emerging SARS-CoV-2 VoC and diverse sarbecoviruses, presenting a possible alternative or supplement to monoclonal antibody immunotherapies.

Human and hamster sera correlate well in identifying antigenic drift among SARS-CoV-2 variants, including JN.1

Antigenic assessments of SARS-CoV-2 variants inform decisions to update COVID-19 vaccines. Primary infection sera are often used for assessments, but such sera are rare due to population immunity from SARS-CoV-2 infections and COVID-19 vaccinations. Here, we show that neutralization titers and breadth of matched human and hamster pre-Omicron variant primary infection sera correlate well and generate similar antigenic maps. The hamster antigenic map shows modest antigenic drift among XBB sub-lineage variants, with JN.1 and BA.4/BA.5 variants within the XBB cluster, but with fivefold to sixfold antigenic differences between these variants and XBB.1.5. Compared to sera following only ancestral or bivalent COVID-19 vaccinations, or with post-vaccination infections, XBB.1.5 booster sera had the broadest neutralization against XBB sub-lineage variants, although a fivefold titer difference was still observed between JN.1 and XBB.1.5 variants. These findings suggest that antibody coverage of antigenically divergent JN.1 could be improved with a matched vaccine antigen.IMPORTANCEUpdates to COVID-19 vaccine antigens depend on assessing how much vaccine antigens differ antigenically from newer SARS-CoV-2 variants. Human sera from single variant infections are ideal for discriminating antigenic differences among variants, but such primary infection sera are now rare due to high population immunity. It remains unclear whether sera from experimentally infected animals could substitute for human sera for antigenic assessments. This report shows that neutralization titers of variant-matched human and hamster primary infection sera correlate well and recognize variants similarly, indicating that hamster sera can be a proxy for human sera for antigenic assessments. We further show that human sera following an XBB.1.5 booster vaccine broadly neutralized XBB sub-lineage variants but titers were fivefold lower against the more recent JN.1 variant. These findings support updating the current COVID-19 vaccine variant composition and developing a framework for assessing antigenic differences in future variants using hamster primary infection sera.

SARS-CoV-2 variant replacement constrains vaccine-specific viral diversification

Coronavirus disease 2019 (COVID-19) vaccine breakthrough infections have been important for all circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant periods, but the contribution of vaccine-specific SARS-CoV-2 viral diversification to vaccine failure remains unclear. This study analyzed 595 SARS-CoV-2 sequences collected from the Military Health System beneficiaries between December 2020 and April 2022 to investigate the impact of vaccination on viral diversity. By comparing sequences based on the vaccination status of the participant, we found limited evidence indicating that vaccination was associated with increased viral diversity in the SARS-CoV-2 spike, and we show little to no evidence of a substantial sieve effect within major variants; rather, we show that rapid variant replacement constrained intragenotype COVID-19 vaccine strain immune escape. These data suggest that, during past and perhaps future periods of rapid SARS-CoV-2 variant replacement, vaccine-mediated effects were subsumed with other drivers of viral diversity due to the massive scale of infections and vaccinations that occurred in a short time frame. However, our results also highlight some limitations of using sieve analysis methods outside of placebo-controlled clinical trials.

Inducing Long Lasting B Cell and T Cell Immunity Against Multiple Variants of SARS-CoV-2 Through Mutant Bacteriophage Qβ-Receptor Binding Domain Conjugate

More than 3 years into the global pandemic, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains a significant threat to public health. Immunities acquired from infection or current vaccines fail to provide long term protection against subsequent infections, mainly due to their fast-waning nature and the emergence of variants of concerns (VOCs) such as Omicron. To overcome these limitations, SARS-CoV-2 Spike protein receptor binding domain (RBD)-based epitopes are investigated as conjugates with a powerful carrier, the mutant bacteriophage Qβ (mQβ). The epitope design is critical to eliciting potent antibody responses with the full length RBD being superior to peptide and glycopeptide antigens. The full length RBD conjugated with mQβ activates both humoral and cellular immune systems in vivo, inducing broad spectrum, persistent, and comprehensive immune responses effective against multiple VOCs including Delta and Omicron variants, rendering it a promising vaccine candidate.

From bench to bedside: potential of translational research in COVID-19 and beyond

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease 2019 (COVID-19) have been around for more than 3 years now. However, due to constant viral evolution, novel variants are emerging, leaving old treatment protocols redundant. As treatment options dwindle, infection rates continue to rise and seasonal infection surges become progressively common across the world, rapid solutions are required. With genomic and proteomic methods generating enormous amounts of data to expand our understanding of SARS-CoV-2 biology, there is an urgent requirement for the development of novel therapeutic methods that can allow translational research to flourish. In this review, we highlight the current state of COVID-19 in the world and the effects of post-infection sequelae. We present the contribution of translational research in COVID-19, with various current and novel therapeutic approaches, including antivirals, monoclonal antibodies and vaccines, as well as alternate treatment methods such as immunomodulators, currently being studied and reiterate the importance of translational research in the development of various strategies to contain COVID-19.

Impact of vaccine coverage and disruption to health services on COVID-19 in Ukraine

COVID-19 surveillance in Ukraine ceased after the Russian invasion of the country in 2022, on a background of low vaccination rates of 34.5% for two doses at this time. We conducted a modelling study to estimate the epidemic trajectory of SARS-COV-2 in Ukraine after the start of the war. We use a COVID-19 deterministic Susceptible-Exposed-Infected-Recovered (SEIR) model for Ukraine to estimate the impact of increased vaccination coverage and masking as public health interventions. We fit the model output to case notification data between 6 January and 25 February 2022, then we forecast the COVID-19 epidemic trajectory in different scenarios of mask use and vaccine coverage. In the best-case scenario, 69% of the Ukrainian population would have been infected in the first half of 2022. Increasing mask use from 50 to 80% reduces cases and deaths by 17% and 30% respectively, while increasing vaccination rates to 60% and 9.6% for two and three doses respectively results in a 3% reduction in cases and 28% in deaths. However, if vaccination is increased to a higher coverage of 80% with two doses and 12.8% with three, or mask effectiveness is reduced to 40%, increasing vaccination coverage is more effective. The loss of health services, displacement, and destruction of infrastructure will amplify the risk of COVID-19 in Ukraine and make vaccine programs less feasible. Masks do not need the health infrastructure or cold-chain logistics required for vaccines and are more feasible for rapid epidemic control during war. However, increasing vaccine coverage will save more lives. Vaccination of refugees who have fled to other countries can be more feasibly achieved.

Protective effectiveness of previous infection against subsequent SARS-Cov-2 infection: systematic review and meta-analysis

Background

The protective effectiveness provided by naturally acquired immunity against SARS-CoV-2 reinfection remain controversial.

Objective

To systematically evaluate the protective effect of natural immunity against subsequent SARS-CoV-2 infection with different variants.

Methods

We searched for related studies published in seven databases before March 5, 2023. Eligible studies included in the analysis reported the risk of subsequent infection for groups with or without a prior SARS-CoV-2 infection. The primary outcome was the overall pooled incidence rate ratio (IRR) of SARS-CoV-2 reinfection/infection between the two groups. We also focused on the protective effectiveness of natural immunity against reinfection/infection with different SARS-CoV-2 variants. We used a random-effects model to pool the data, and obtained the bias-adjusted results using the trim-and-fill method. Meta-regression and subgroup analyses were conducted to explore the sources of heterogeneity. Sensitivity analysis was performed by excluding included studies one by one to evaluate the stability of the results.

Results

We identified 40 eligible articles including more than 20 million individuals without the history of SARS-CoV-2 vaccination. The bias-adjusted efficacy of naturally acquired antibodies against reinfection was estimated at 65% (pooled IRR = 0.35, 95% CI = 0.26-0.47), with higher efficacy against symptomatic COVID-19 cases (pooled IRR = 0.15, 95% CI = 0.08-0.26) than asymptomatic infection (pooled IRR = 0.40, 95% CI = 0.29-0.54). Meta-regression revealed that SARS-CoV-2 variant was a statistically significant effect modifier, which explaining 46.40% of the variation in IRRs. For different SARS-CoV-2 variant, the pooled IRRs for the Alpha (pooled IRR = 0.11, 95% CI = 0.06-0.19), Delta (pooled IRR = 0.19, 95% CI = 0.15-0.24) and Omicron (pooled IRR = 0.61, 95% CI = 0.42-0.87) variant were higher and higher. In other subgroup analyses, the pooled IRRs of SARS-CoV-2 infection were statistically various in different countries, publication year and the inclusion end time of population, with a significant difference (p = 0.02, p < 0.010 and p < 0.010), respectively. The risk of subsequent infection in the seropositive population appeared to increase slowly over time. Despite the heterogeneity in included studies, sensitivity analyses showed stable results.

Conclusion

Previous SARS-CoV-2 infection provides protection against pre-omicron reinfection, but less against omicron. Ongoing viral mutation requires attention and prevention strategies, such as vaccine catch-up, in conjunction with multiple factors.

Durability of immune responses to SARS-CoV-2 infection and vaccination

Infection with SARS-CoV-2 in humans has caused a pandemic of unprecedented dimensions. SARS-CoV-2 is primarily transmitted through respiratory droplets and targets ciliated epithelial cells in the nasal cavity, trachea, and lungs by utilizing the cellular receptor angiotensin-converting enzyme 2 (ACE2). The innate immune response, including type I and III interferons, inflammatory cytokines (IL-6, TNF-α, IL-1β), innate immune cells (monocytes, DCs, neutrophils, natural killer cells), antibodies (IgG, sIgA, neutralizing antibodies), and adaptive immune cells (B cells, CD8+ and CD4+ T cells) play pivotal roles in mitigating COVID-19 disease. Broad and durable B-cell- and T-cell immunity elicited by infection and vaccination is essential for protection against severe disease, hospitalization and death. However, the emergence of SARS-CoV-2 variants that evade neutralizing antibodies continue to jeopardize vaccine efficacy. In this review, we highlight our understanding the infection- and vaccine-mediated humoral, B and T cell responses, the durability of the immune responses, and how variants continue to threaten the efficacy of SARS-CoV-2 vaccines.

Antigenic Cartography of SARS-CoV-2

Antigenic cartography is a tool for interpreting and visualizing antigenic differences between virus variants based on virus neutralization data. This approach has been successfully used in the selection of influenza vaccine seed strains. With the emergence of SARS-CoV-2 variants escaping vaccine-induced antibody response, adjusting COVID-19 vaccines has become essential. This review provides information on the antigenic differences between SARS-CoV-2 variants revealed by antigenic cartography and explores a potential of antigenic cartography-based methods (e.g., building antibody landscapes and neutralization breadth gain plots) for the quantitative assessment of the breadth of the antibody response. Understanding the antigenic differences of SARS-CoV-2 and the possibilities of the formed humoral immunity aids in the prompt modification of preventative vaccines against COVID-19.

Antigenic cartography using hamster sera identifies SARS-CoV-2 JN.1 evasion seen in human XBB.1.5 booster sera

Antigenic assessments of SARS-CoV-2 variants inform decisions to update COVID-19 vaccines. Primary infection sera are often used for assessments, but such sera are rare due to population immunity from SARS-CoV-2 infections and COVID-19 vaccinations. Here, we show that neutralization titers and breadth of matched human and hamster pre-Omicron variant primary infection sera correlate well and generate similar antigenic maps. The hamster antigenic map shows modest antigenic drift among XBB sub-lineage variants, with JN.1 and BA.4/BA.5 variants within the XBB cluster, but with five to six-fold antigenic differences between these variants and XBB.1.5. Compared to sera following only ancestral or bivalent COVID-19 vaccinations, or with post-vaccination infections, XBB.1.5 booster sera had the broadest neutralization against XBB sub-lineage variants, although a five-fold titer difference was still observed between JN.1 and XBB.1.5 variants. These findings suggest that antibody coverage of antigenically divergent JN.1 could be improved with a matched vaccine antigen.

Immune and behavioral correlates of protection against symptomatic post-vaccination SARS-CoV-2 infection

Introduction

We sought to determine pre-infection correlates of protection against SARS-CoV-2 post-vaccine inzfections (PVI) acquired during the first Omicron wave in the United States.

Methods

Serum and saliva samples from 176 vaccinated adults were collected from October to December of 2021, immediately before the Omicron wave, and assessed for SARS-CoV-2 Spike-specific IgG and IgA binding antibodies (bAb). Sera were also assessed for bAb using commercial assays, and for neutralization activity against several SARS-CoV-2 variants. PVI duration and severity, as well as risk and precautionary behaviors, were assessed by questionnaires.

Results

Serum anti-Spike IgG levels assessed by research assay, neutralization titers against Omicron subvariants, and low home risk scores correlated with protection against PVIs after multivariable regression analysis. Commercial assays did not perform as well as research assay, likely due to their lower dynamic range.

Discussion

In the 32 participants that developed PVI, anti-Spike IgG bAbs correlated with lower disease severity and shorter duration of illness.

Investigating vulnerability of the conserved SARS-CoV-2 spike's heptad repeat 2 as target for fusion inhibitors using chimeric miniproteins

Inhibition of SARS-CoV-2 membrane fusion is a highly desired target to combat COVID-19. The interaction between the spike's heptad repeat (HR) regions 1 (HR1) and 2 (HR2) is a crucial step during the fusion process and these highly conserved HR regions constitute attractive targets for fusion inhibitors. However, the relative importance of each subregion of the long HR1-HR2 interface for viral inhibition remains unclear. Here, we designed, produced, and characterized a series of chimeric miniproteins that mimic two different half subdomains of HR1. The proteins were designed as single polypeptide chains that spontaneously fold into antiparallel trimeric helical bundles aimed at structurally imitate the molecular surface of each HR1 half subregion. All the miniproteins folded stably as helical structures and could bind complementary HR2 peptides with moderate affinity. However, only the miniproteins mimicking the N-terminal HR1 half subdomain, but not those imitating C-terminal one, could inhibit cell infection by SARS-COV-2 real viruses in cell cultures. Most interestingly, the inhibitory activity of the miniproteins correlated with their structural stability, but not with their relative binding affinity for HR2 peptides. These results are highly relevant for designing more focused and active fusion inhibitors targeting the highly conserved HR2 region of the Spike.

Diverse array of neutralizing antibodies elicited upon Spike Ferritin Nanoparticle vaccination in rhesus macaques

The repeat emergence of SARS-CoV-2 variants of concern (VoC) with decreased susceptibility to vaccine-elicited antibodies highlights the need to develop next-generation vaccine candidates that confer broad protection. Here we describe the antibody response induced by the SARS-CoV-2 Spike Ferritin Nanoparticle (SpFN) vaccine candidate adjuvanted with the Army Liposomal Formulation including QS21 (ALFQ) in non-human primates. By isolating and characterizing several monoclonal antibodies directed against the Spike Receptor Binding Domain (RBD), N-Terminal Domain (NTD), or the S2 Domain, we define the molecular recognition of vaccine-elicited cross-reactive monoclonal antibodies (mAbs) elicited by SpFN. We identify six neutralizing antibodies with broad sarbecovirus cross-reactivity that recapitulate serum polyclonal antibody responses. In particular, RBD mAb WRAIR-5001 binds to the conserved cryptic region with high affinity to sarbecovirus clades 1 and 2, including Omicron variants, while mAb WRAIR-5021 offers complete protection from B.1.617.2 (Delta) in a murine challenge study. Our data further highlight the ability of SpFN vaccination to stimulate cross-reactive B cells targeting conserved regions of the Spike with activity against SARS CoV-1 and SARS-CoV-2 variants.

Durability and cross-reactive immune memory to SARS-CoV-2 in individuals 2 years after recovery from COVID-19: a longitudinal cohort study

BACKGROUND

SARS-CoV-2-specific adaptive immunity more than 1 year after initial infection has not been well characterised. The aim of this study was to investigate the durability and cross-reactivity of immunological memory acquired from natural infection against SARS-CoV-2 in individuals recovered from COVID-19 2 years after infection.

METHODS

In this longitudinal cohort study, we recruited patients who had recovered from laboratory-confirmed COVID-19 and were discharged from Jinyintan Hospital (Wuhan, China) between Jan 7 and May 29, 2020. We carried out three successive follow-ups between June 16 and Sept 3, 2020 (6 months), Dec 16, 2020, and Feb 7, 2021 (1 year), and Nov 16, 2021, and Jan 10, 2022 (2 years), in which blood samples were taken. We included participants who did not have re-infection or receive a SARS-CoV-2 vaccination (infected-unvaccinated), and participants who received one to three doses of inactivated vaccine 1-2 years after infection (infected-vaccinated). We evaluated the presence of IgG antibodies, neutralising antibodies, and memory B-cell and memory T-cell responses against the prototype strain and delta and omicron variants.

FINDINGS

In infected-unvaccinated participants, neutralising antibody titres continually declined from 6-month to 2-year follow-up visits, with a half-life of about 141·2 days. Neutralising antibody responses to omicron sublineages (BA.1, BA.1.1, BA.2, BA.4/5, BF.7, BQ.1, and XBB) were poor. Memory B-cell responses to the prototype strain were retained at 2 years and presented cross-reactivity to the delta and omicron BA.1 variants. The magnitude of interferon γ and T-cell responses to SARS-CoV-2 were not significantly different between 1 year and 2 years after infection. Multifunctional T-cell responses against SARS-CoV-2 spike protein and nucleoprotein were detected in most participants. Recognition of the BA.1 variant by memory T cells was not affected in most individuals. The antibody titres and the frequencies of memory B cells, but not memory T cells, increased in infected-vaccinated participants after they received the inactivated vaccine.

INTERPRETATION

This study improves the understanding of the duration of SARS-CoV-2-specific immunity without boosting, which has implications for the design of vaccination regimens and programmes. Our data suggest that memory T-cell responses primed by initial viral infection remain highly cross-reactive after 2 years. With the increasing emergence of variants, effective vaccines should be introduced to boost neutralising antibody and overall T-cell responses to newly emerged SARS-CoV-2 variants.

FUNDING

Chinese Academy of Medical Sciences, National Natural Science Foundation of China, Fundamental Research Funds for the Central Universities for Peking Union Medical College, Beijing Natural Science Foundation, UK Medical Research Council.

Comparing the immune response and protective effect of COVID-19 vaccine under different vaccination strategies

Although highly infectious respiratory viral infections spread rapidly, humans have evolved a precise and complex immune mechanism to deal with respiratory viruses, with strong intrinsic, highly adaptive and specific humoral and cellular immunity. At the same time, vaccination against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is one of the most cost-effective and efficient means of preventing morbidity, severe illness, and death from Coronavirus disease 2019 (COVID-19). As the global epidemic of COVID-19 continues to evolve and vaccines are being developed, it is important to conduct studies on immunization strategies to optimize vaccination strategies when appropriate. This review was conducted to investigate the relationship between the immune response and the protective effect of different vaccination scenarios (including booster, sequential and hybrid immunity), and to provide a basis for the optimization of vaccination strategies and the development of new vaccines in the future.

Omicron variants escape the persistent SARS-CoV-2-specific antibody response in 2-year COVID-19 convalescents regardless of vaccination

With the ongoing COVID-19 pandemic and the emergence of various SARS-CoV-2 variants, a comprehensive evaluation of long-term efficacy of antibody response in convalescent individuals is urgently needed. Several longitudinal studies had reported the antibody dynamics after SARS-CoV-2 acute infection, but the follow-up was mostly limited to 1 year or 18 months at the maximum. In this study, we investigated the durability, potency, and susceptibility to immune evasion of SARS-CoV-2-specific antibody in COVID-19 convalescents for 2 years after discharge. These results showed the persistent antibody-dependent immunity could protect against the WT and Delta variant to some extent. However, the Omicron variants (BA.1, BA.2, and BA.4/5) largely escaped this preexisting immunity in recovered individuals. Furthermore, we revealed that inactivated vaccines (BBIBP-CorV, CoronaVac, or KCONVAC) could improve the plasma neutralization and help to maintain the broadly neutralizing antibodies at a certain level. Notably, with the time-dependent decline of antibody, 1-dose or 2-dose vaccination strategy seemed not to be enough to provide immune protection against the emerging variants. Overall, these results facilitated our understanding of SARS-CoV-2-induced antibody memory, contributing to the development of immunization strategy against SARS-CoV-2 variants for such a large number of COVID-19 survivors.

Omicron BA.1 breakthrough infections in inactivated COVID-19 vaccine recipients induced distinct pattern of antibody and T cell responses to different Omicron sublineages

The adaptive immunity against SARS-CoV-2 prototype strain and Omicron sublineages induced by BA.1 breakthrough infection in vaccinees of inactivated COVID-19 vaccines have not been well characterized. Here, we report that BA.1 breakthrough infection induced mucosal sIgA and resulted in higher IgG titers against prototype strain and Omicron sublineages in vaccinees than in vaccine naïve-infected individuals. BA.1 breakthrough infection boosted antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis to prototype strain and BA.1, BA.1.1, BA.2, BA.2.12.1, and BA.2.75 but not BA.4/5 and induced neutralization against prototype strain and BA.1, BA.1.1, BA.2, BA.2.12.1, BA.2.75, and BA.4/5 but not BF.7, BQ.1, and XBB. In total, BA.1 breakthrough infection individuals produced less extensive sIgA, plasma IgG and NAb responses against Omicron sublineages compared with those against prototype strain. Further, BA.1 breakthrough infection induced recall B cell response to prototype strain and Omicron variant, primarily targeting memory B cells producing conserved epitopes. Memory T cell responses against Omicron is largely preserved. Individuals with vaccine booster did not induce more beneficial immune responses to Omicron sublineages upon BA.1 breakthrough infection than those with primary vaccine dose only. The breakthrough infection individuals produced stronger adaptive immunity than those of inactivated vaccine-healthy individuals. These data have important implications for understanding the vaccine effectiveness and adaptive immunity to breakthrough infection in individuals fully immunized with inactivated vaccines. Omicron sublineages, especially for those emerged after BA.4/5 strain, evade NAb responses induced by BA.1 breakthrough infection. It is urgent to optimize the vaccine immunogen design and formulations to SARS-CoV-2 variants.

Antigenic evolution of SARS coronavirus 2

SARS coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, emerged in China in December 2019. Vaccines developed were very effective initially, however, the virus has shown remarkable evolution with multiple variants spreading globally over the last three years. Nowadays, newly emerging Omicron lineages are gaining substitutions at a fast rate, resulting in escape from neutralization by antibodies that target the Spike protein. Tools to map the impact of substitutions on the further antigenic evolution of SARS-CoV-2, such as antigenic cartography, may be helpful to update SARS-CoV-2 vaccines. In this review, we focus on the antigenic evolution of SARS-CoV-2, highlighting the impact of Spike protein substitutions individually and in combination on immune escape.

Humoral Immune Responses in Patients with Severe COVID-19: A Comparative Pilot Study between Individuals Infected by SARS-CoV-2 during the Wild-Type and the Delta Periods

Since the onset of the COVID-19 pandemic, humanity has experienced the spread and circulation of several SARS-CoV-2 variants that differed in transmissibility, contagiousness, and the ability to escape from vaccine-induced neutralizing antibodies. However, issues related to the differences in the variant-specific immune responses remain insufficiently studied. The aim of this study was to compare the parameters of the humoral immune responses in two groups of patients with acute COVID-19 who were infected during the circulation period of the D614G and the Delta variants of SARS-CoV-2. Sera from 48 patients with acute COVID-19 were tested for SARS-CoV-2 binding and neutralizing antibodies using six assays. We found that serum samples from the D614G period demonstrated 3.9- and 1.6-fold increases in RBD- and spike-specific IgG binding with wild-type antigens compared with Delta variant antigens (p < 0.01). Cluster analysis showed the existence of two well-separated clusters. The first cluster mainly consisted of D614G-period patients and the second cluster predominantly included patients from the Delta period. The results thus obtained indicate that humoral immune responses in D614G- and Delta-specific infections can be characterized by variant-specific signatures. This can be taken into account when developing new variant-specific vaccines.

Outpatient Treatment with AZD7442 (Tixagevimab/Cilgavimab) Prevented COVID-19 Hospitalizations over 6 Months and Reduced Symptom Progression in the TACKLE Randomized Trial

INTRODUCTION

We assessed effects of AZD7442 (tixagevimab/cilgavimab) on deaths from any cause or hospitalizations due to coronavirus disease 2019 (COVID-19) and symptom severity and longer-term safety in the TACKLE adult outpatient treatment study.

METHODS

Participants received 600 mg AZD7442 (n = 452) or placebo (n = 451) ≤ 7 days of COVID-19 symptom onset.

RESULTS

Death from any cause or hospitalization for COVID-19 complications or sequelae through day 169 (key secondary endpoint) occurred in 20/399 (5.0%) participants receiving AZD7442 versus 40/407 (9.8%) receiving placebo [relative risk reduction (RRR) 49.1%; 95% confidence interval (CI) 14.5, 69.7; p = 0.009] or 50.7% (95% CI 17.5, 70.5; p = 0.006) after excluding participants unblinded before day 169 for consideration of vaccination). AZD7442 reduced progression of COVID-19 symptoms versus placebo through to day 29 (RRR 12.5%; 95% CI 0.5, 23.0) and improved most symptoms within 1-2 weeks. Over median safety follow-up of 170 days, adverse events occurred in 174 (38.5%) and 196 (43.5%) participants receiving AZD7442 or placebo, respectively. Cardiac serious adverse events occurred in two (0.4%) and three (0.7%) participants receiving AZD7442 or placebo, respectively.

CONCLUSIONS

AZD7442 was well tolerated and reduced hospitalization and mortality through 6 months, and symptom burden through 29 days, in outpatients with mild-to-moderate COVID-19.

CLINICAL TRIAL REGISTRATION

Clinicaltrials.gov, NCT04723394. ( https://beta.

CLINICALTRIALS

gov/study/NCT04723394 ).

SARS-CoV-2 neutralizing antibody bebtelovimab - a systematic scoping review and meta-analysis

Introduction

The COVID-19 pandemic is a major global public health crisis. More than 2 years into the pandemic, effective therapeutic options remain limited due to rapid viral evolution. Stemming from the emergence of multiple variants, several monoclonal antibodies are no longer suitable for clinical use. This scoping review aimed to summarize the preclinical and clinical evidence for bebtelovimab in treating newly emerging SARS-CoV-2 variants.

Methods

We systematically searched five electronic databases (PubMed, CENTRAL, Embase, Global Health, and PsycINFO) from date of inception to September 30, 2022, for studies reporting on the effect of bebtelovimab in SARS-CoV-2 infection, using a combination of search terms around -bebtelovimab‖, -LY-CoV1404‖, -LY3853113‖, and -coronavirus infection‖. All citations were screened independently by two researchers. Data were extracted and thematically analyzed based on study design by adhering to the stipulated scoping review approaches.

Results

Thirty-nine studies were included, thirty-four non-clinical studies were narratively synthesized, and five clinical studies were meta-analyzed. The non-clinical studies revealed bebtelovimab not only potently neutralized wide-type SARS-CoV-2 and existing variants of concern such as B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), and B.1.617.2 (Delta), but also retained appreciable activity against Omicron lineages, including BA.2.75, BA.4, BA.4.6, and BA.5. Unlike other monoclonal antibodies, bebtelovimab was able to bind to epitope of the SARS-CoV-2 S protein by exploiting loop mobility or by minimizing side-chain interactions. Pooled analysis from clinical studies depicted that the rates of hospitalization, ICU admission, and death were similar between bebtelovimab and other COVID-19 therapies. Bebtelovimab was associated with a low incidence of treatment-emergent adverse events.

Conclusion

Preclinical evidence suggests bebtelovimab be a potential treatment for COVID-19 amidst viral evolution. Bebtelovimab has comparable efficacy to other COVID-19 therapies without evident safety concerns.

Single Ad26.COV2.S booster dose following two doses of BBIBP-CorV vaccine against SARS-CoV-2 infection in adults: Day 28 results of a phase 1/2 open-label trial

BACKGROUND

The inactivated COVID-19 whole-virus vaccine BBIBP-CorV has been extensively used worldwide. Heterologous boosting after primary vaccination can induce higher immune responses against SARS-CoV-2 than homologous boosting. The safety and immunogenicity after 28 days of a single Ad26.COV2.S booster dose given at different intervals after 2 doses of BBIBP-CorV are presented.

METHODS

This open-label phase 1/2 trial was conducted in healthy adults in Thailand who had completed 2-dose primary vaccination with BBIBP-CorV. Participants received a single booster dose of Ad26.COV2.S (5 × 1010 virus particles) 90-240 days (Group A1; n = 360) or 45-75 days (Group A2; n = 66) after the second BBIBP-CorV dose. Safety and immunogenicity were assessed over 28 days. Binding IgG antibodies to the full-length pre-fusion Spike and anti-nucleocapsid proteins of SARS-CoV-2 were measured by enzyme-linked immunosorbent assay. The SARS-CoV-2 pseudovirus neutralization assay and live virus microneutralization assay were used to quantify the neutralizing activity of antibodies against ancestral SARS-CoV-2 (Wuhan-Hu-1) and the delta (B.1.617.2) and omicron (B.1.1.529/BA.1 and BA.2) variants. The cell-mediated immune response was measured using a quantitative interferon (IFN)-γ release assay in whole blood.

RESULTS

Solicited local and systemic adverse events (AEs) on days 0-7 were mostly mild, as were unsolicited vaccine-related AEs during days 0-28, with no serious AEs. On day 28, anti-Spike binding antibodies increased from baseline by 487- and 146-fold in Groups A1 and A2, and neutralizing antibodies against ancestral SARS-CoV-2 by 55- and 37-fold, respectively. Humoral responses were strongest against ancestral SARS-CoV-2, followed by the delta, then the omicron BA.2 and BA.1 variants. T-cell-produced interferon-γ increased approximately 10-fold in both groups.

CONCLUSIONS

A single heterologous Ad26.COV2.S booster dose after two BBIBP-CorV doses was well tolerated and induced robust humoral and cell-mediated immune responses measured at day 28 in both interval groups.

CLINICAL TRIALS REGISTRATION

NCT05109559.

A modeling-based approach to optimize COVID-19 vaccine dosing schedules for improved protection

While the development of different vaccines slowed the dissemination of SARS-CoV-2, the occurrence of breakthrough infections has continued to fuel the COVID-19 pandemic. To secure at least partial protection in the majority of the population through 1 dose of a COVID-19 vaccine, delayed administration of boosters has been implemented in many countries. However, waning immunity and emergence of new variants of SARS-CoV-2 suggest that such measures may induce breakthrough infections due to intermittent lapses in protection. Optimizing vaccine dosing schedules to ensure prolonged continuity in protection could thus help control the pandemic. We developed a mechanistic model of immune response to vaccines as an in silico tool for dosing schedule optimization. The model was calibrated with clinical data sets of acquired immunity to COVID-19 mRNA vaccines in healthy and immunocompromised participants and showed robust validation by accurately predicting neutralizing antibody kinetics in response to multiple doses of COVID-19 mRNA vaccines. Importantly, by estimating population vulnerability to breakthrough infections, we predicted tailored vaccination dosing schedules to minimize breakthrough infections, especially for immunocompromised individuals. We identified that the optimal vaccination schedules vary from CDC-recommended dosing, suggesting that the model is a valuable tool to optimize vaccine efficacy outcomes during future outbreaks.

Antigenic Cartography Indicates That the Omicron BA.1 and BA.4/BA.5 Variants Remain Antigenically Distant to Ancestral SARS-CoV-2 after Sputnik V Vaccination Followed by Homologous (Sputnik V) or Heterologous (Comirnaty) Revaccination

The rapid emergence of evasive SARS-CoV-2 variants is an ongoing challenge for COVID-19 vaccinology. Traditional virus neutralization tests provide detailed datasets of neutralization titers against the viral variants. Such datasets are difficult to interpret and do not immediately inform of the sufficiency of the breadth of the antibody response. Some of these issues could be tackled using the antigenic cartography approach. In this study, we created antigenic maps using neutralization titers of sera from donors who received the Sputnik V booster vaccine after primary Sputnik V vaccination and compared them with the antigenic maps based on serum neutralization titers of Comirnaty-boosted donors. A traditional analysis of neutralization titers against the WT (wild-type), Alpha, Beta, Delta, Omicron BA.1, and BA.4/BA.5 variants showed a significant booster humoral response after both homologous (Sputnik V) and heterologous (Comirnaty) revaccinations against all of the studied viral variants. However, despite this, a more in-depth analysis using antigenic cartography revealed that Omicron variants remain antigenically distant from the WT, which is indicative of the formation of insufficient levels of cross-neutralizing antibodies. The implications of these findings may be significant when developing a new vaccine regimen.

COVID-19 vaccine effectiveness against symptomatic infection and hospitalisation in Belgium, July 2021 to May 2022

BackgroundThe Belgian COVID-19 vaccination campaign aimed to reduce disease spread and severity.AimWe estimated SARS-CoV-2 variant-specific vaccine effectiveness against symptomatic infection (VEi) and hospitalisation (VEh), given time since vaccination and prior infection.MethodsNationwide healthcare records from July 2021 to May 2022 on testing and vaccination were combined with a clinical hospital survey. We used a test-negative design and proportional hazard regression to estimate VEi and VEh, controlling for prior infection, time since vaccination, age, sex, residence and calendar week of sampling.ResultsWe included 1,932,546 symptomatic individuals, of whom 734,115 tested positive. VEi against Delta waned from an initial estimate of 80% (95% confidence interval (CI): 80-81) to 55% (95% CI: 54-55) 100-150 days after the primary vaccination course. Booster vaccination increased initial VEi to 85% (95% CI: 84-85). Against Omicron, an initial VEi of 33% (95% CI: 30-36) waned to 17% (95% CI: 15-18), while booster vaccination increased VEi to 50% (95% CI: 49-50), which waned to 20% (95% CI: 19-21) 100-150 days after vaccination. Initial VEh for booster vaccination decreased from 96% (95% CI: 95-96) against Delta to 87% (95% CI: 86-89) against Omicron. VEh against Omicron waned to 73% (95% CI: 71-75) 100-150 days after booster vaccination. While recent prior infections conferred higher protection, infections occurring before 2021 remained associated with significant risk reduction against symptomatic infection. Vaccination and prior infection outperformed vaccination or prior infection only.ConclusionWe report waning and a significant decrease in VEi and VEh from Delta to Omicron-dominant periods. Booster vaccination and prior infection attenuated these effects.

Uses and Challenges of Antiviral Polyclonal and Monoclonal Antibody Therapies

Viral diseases represent a major public health concerns and ever-present risks for developing into future pandemics. Antiviral antibody therapeutics, either alone or in combination with other therapies, emerged as valuable preventative and treatment options, including during global emergencies. Here we will discuss polyclonal and monoclonal antiviral antibody therapies, focusing on the unique biochemical and physiological properties that make them well-suited as therapeutic agents. We will describe the methods of antibody characterization and potency assessment throughout development, highlighting similarities and differences between polyclonal and monoclonal products as appropriate. In addition, we will consider the benefits and challenges of antiviral antibodies when used in combination with other antibodies or other types of antiviral therapeutics. Lastly, we will discuss novel approaches to the characterization and development of antiviral antibodies and identify areas that would benefit from additional research.

Changes in serum-neutralizing antibody potency and breadth post-SARS-CoV-2 mRNA vaccine boost

A better understanding of the durability and breadth of serum-neutralizing antibody responses against multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants elicited by COVID-19 vaccines is crucial in addressing the current pandemic. In this study, we quantified the decay of serum neutralization antibodies (nAbs) after second and third doses of the original COVID-19 mRNA vaccine. Using an authentic virus-neutralization assay, we found that decay half-lives of WA1- and Delta-nAbs were both ∼60 days after second and third vaccine dose. Unexpectedly, the durability of serum antibodies that neutralize three different Omicron subvariants (BA.1.1, BA.5, BA.2.12.1) was substantially better, with half-lives of ≥6 months. A booster dose of the original COVID-19 vaccine was also found to broaden antibody responses against SARS-CoV and four other sarbecoviruses, in addition to multiple SARS-CoV-2 strains. These findings suggest that repeated vaccinations with the COVID-19 vaccine may confer a degree of protection against future spillover of sarbecoviruses from animal reservoirs.

Computational design of nanomolar-binding antibodies specific to multiple SARS-CoV-2 variants by engineering a specificity switch of antibody 80R using RosettaAntibodyDesign (RAbD) results in potential generalizable therapeutic antibodies for novel SARS-CoV-2 virus

The human infectious disease COVID-19 caused by the SARS-CoV-2 virus has become a major threat to global public health. Developing a vaccine is the preferred prophylactic response to epidemics and pandemics. However, for individuals who have contracted the disease, the rapid design of antibodies that can target the SARS-CoV-2 virus fulfils a critical need. Further, discovering antibodies that bind multiple variants of SARS-CoV-2 can aid in the development of rapid antigen tests (RATs) which are critical for the identification and isolation of individuals currently carrying COVID-19. Here we provide a proof-of-concept study for the computational design of high-affinity antibodies that bind to multiple variants of the SARS-CoV-2 spike protein using RosettaAntibodyDesign (RAbD). Well characterized antibodies that bind with high affinity to the SARS-CoV-1 (but not SARS-CoV-2) spike protein were used as templates and re-designed to bind the SARS-CoV-2 spike protein with high affinity, resulting in a specificity switch. A panel of designed antibodies were experimentally validated. One design bound to a broad range of variants of concern including the Omicron, Delta, Wuhan, and South African spike protein variants.

Deep Structural Analysis of Myriads of Omicron Sub-Variants Revealed Hotspot for Vaccine Escape Immunity

The emergence of the Omicron variant has reinforced the importance of continued SARS-CoV-2 evolution and its possible impact on vaccine effectiveness. Specifically, mutations in the receptor-binding domain (RBD) are critical to comprehend the flexibility and dynamicity of the viral interaction with the human agniotensin-converting enzyme 2 (hACE2) receptor. To this end, we have applied a string of deep structural and genetic analysis tools to map the substitution patterns in the S protein of major Omicron sub-variants (n = 51) with a primary focus on the RBD mutations. This head-to-head comparison of Omicron sub-variants revealed multiple simultaneous mutations that are attributed to antibody escape, and increased affinity and binding to hACE2. Our deep mapping of the substitution matrix indicated a high level of diversity at the N-terminal and RBD domains compared with other regions of the S protein, highlighting the importance of these two domains in a matched vaccination approach. Structural mapping identified highly variable mutations in the up confirmation of the S protein and at sites that critically define the function of the S protein in the virus pathobiology. These substitutional trends offer support in tracking mutations along the evolutionary trajectories of SAR-CoV-2. Collectively, the findings highlight critical areas of mutations across the major Omicron sub-variants and propose several hotspots in the S proteins of SARS-CoV-2 sub-variants to train the future design and development of COVID-19 vaccines.

The protection quest is a primary key to sharing the neutralizing antibody response to cover against all emerging VOCs based on BIV1-CovIran studies

Over time, the antigenic evolution of emerging variants of SARS-CoV-2 has demanded the development of potential protective vaccines. Administration of additional doses of current vaccines based on the WT spike protein may boost immunity, but their effectiveness has dwindled for patients with more recent variants. Here, we studied the neutralization activity of post-WT strain-based vaccination and a structural simulation in-silico based on the interactions of the RBD-hACE2 as the key to initiating infection among the VOCs of SARS-CoV-2. Our data display shows that WT sera showed a markedly greater reduction in Delta and Omicron, suggesting that the Wuhan-based vaccines may be more susceptible to breakthrough and new VOCs. According to the MD simulation, mutations of Omicron result in a significant change in the variant charge distribution throughout the binding interface that consequently alters the critical interface electrostatic potential in comparison to other variants. This observation provides new insights into immunization policy and next-generation vaccine development.

Comparative Binding Ability of Human Monoclonal Antibodies against Omicron Variants of SARS-CoV-2: An In Silico Investigation

Mutation(s) in the spike protein is the major characteristic trait of newly emerged SARS-CoV-2 variants such as Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Delta-plus. Omicron (B.1.1.529) is the latest addition and it has been characterized by high transmissibility and the ability to escape host immunity. Recently developed vaccines and repurposed drugs exert limited action on Omicron strains and hence new therapeutics are immediately needed. Herein, we have explored the efficiency of twelve therapeutic monoclonal antibodies (mAbs) targeting the RBD region of the spike glycoprotein against all the Omicron variants bearing a mutation in spike protein through molecular docking and molecular dynamics simulation. Our in silico evidence reveals that adintivimab, beludivimab, and regadanivimab are the most potent mAbs to form strong biophysical interactions and neutralize most of the Omicron variants. Considering the efficacy of mAbs, we incorporated CDRH3 of beludavimab within the framework of adintrevimab, which displayed a more intense binding affinity towards all of the Omicron variants viz. BA.1, BA.2, BA.2.12.1, BA.4, and BA.5. Furthermore, the cDNA of chimeric mAb was cloned in silico within pET30ax for recombinant production. In conclusion, the present study represents the candidature of human mAbs (beludavimab and adintrevimab) and the therapeutic potential of designed chimeric mAb for treating Omicron-infected patients.

Neutralization Effect of Sera against Delta and Omicron in Patients Recovering from COVID-19 and Inactivated Vaccine Recipients

This study aims to analyze the serum neutralization capacity against Delta and Omicron variants in three clusters of individuals, including those who had recovered from COVID-19 and those who had received two and three doses of inactivated vaccine. Pseudovirus neutralization tests were performed on serum samples. The neutralizing titers between different groups were compared using the Wilcoxon's signed-rank test. Among the two-dose vaccinees, the neutralization titers of the Omicron variant were reduced by approximately 3.1-fold compared to the wild-type virus (p < 0.05). Meanwhile, among the three-dose vaccinees, the neutralization titers for Delta and Omicron variants were 3.5-fold (p < 0.05) and 5.0-fold (p < 0.05) lower, respectively, as compared to the wild-type virus. In addition, among the recovering patients, the neutralization titers for Delta and Omicron variants were 3.9-fold (p < 0.05) and 29.1-fold (p < 0.05) lower, respectively, as compared to the wild-type virus. Overall, only 12.0% (11/92) of participants showed neutralizing titers against Omicron above the detection limit. The ability to neutralize wild-type pseudovirus was significantly boosted in three-dose vaccinees as compared to two-dose vaccinees. Sera from recovered patients showed greater neutralizing titers for the wild-type and Delta pseudoviruses than the two- and three-dose inactivated vaccine groups. The present study revealed a loss of neutralizing activity against the Omicron variant in almost all samples. Moreover, the immunization effect obtained through natural infection is more robust than that from the active immunization method of vaccination.

Non-Omicron breakthrough infection with higher viral load and longer vaccination-infection interval improves SARS-CoV-2 BA.4/5 neutralization

The immune responses to SARS-CoV-2 variants in COVID-19 cases are influenced by various factors including pre-existing immunity via vaccination and prior infection. Elucidating the drivers for upgrading neutralizing activity to SARS-CoV-2 in COVID-19 cases with pre-existing immunity will aid in improving COVID-19 booster vaccines with enhanced cross-protection against antigenically distinct variants, including the Omicron sub-lineage BA.4/5. This study revealed that the magnitude and breadth of neutralization activity to SARS-CoV-2 variants after breakthrough infections are determined primarily by upper respiratory viral load and vaccination-infection time interval. Extensive neutralizing breadth, covering even the most antigenically distant BA.4/5, was observed in cases with higher viral load and longer time intervals. Antigenic cartography depicted a critical role of the time interval in expanding the breadth of neutralization to SARS-CoV-2 variants. Our results illustrate the importance of dosing interval optimization as well as antigen design in developing variant-proof booster vaccines.

SARS-CoV-2 variant evasion of monoclonal antibodies based on in vitro studies

Monoclonal antibodies (mAbs) offer a treatment option for individuals with severe COVID-19 and are especially important in high-risk individuals where vaccination is not an option. Given the importance of understanding the evolution of resistance to mAbs by SARS-CoV-2, we reviewed the available in vitro neutralization data for mAbs against live variants and viral constructs containing spike mutations of interest. Unfortunately, evasion of mAb-induced protection is being reported with new SARS-CoV-2 variants. The magnitude of neutralization reduction varied greatly among mAb-variant pairs. For example, sotrovimab retained its neutralization capacity against Omicron BA.1 but showed reduced efficacy against BA.2, BA.4 and BA.5, and BA.2.12.1. At present, only bebtelovimab has been reported to retain its efficacy against all SARS-CoV-2 variants considered here. Resistance to mAb neutralization was dominated by the action of epitope single amino acid substitutions in the spike protein. Although not all observed epitope mutations result in increased mAb evasion, amino acid substitutions at non-epitope positions and combinations of mutations also contribute to evasion of neutralization. This Review highlights the implications for the rational design of viral genomic surveillance and factors to consider for the development of novel mAb therapies.

A modeling-based approach to optimize COVID-19 vaccine dosing schedules for improved protection

While the development of different vaccines has slowed the dissemination of SARS-CoV-2, the occurrence of breakthrough infections continues to fuel the pandemic. As a strategy to secure at least partial protection, with a single dose of a given COVID-19 vaccine to maximum possible fraction of the population, delayed administration of subsequent doses (or boosters) has been implemented in many countries. However, waning immunity and emergence of new variants of SARS-CoV-2 suggest that such measures may jeopardize the attainment of herd immunity due to intermittent lapses in protection. Optimizing vaccine dosing schedules could thus make the difference between periodic occurrence of breakthrough infections or effective control of the pandemic. To this end, we have developed a mechanistic mathematical model of adaptive immune response to vaccines and demonstrated its applicability to COVID-19 mRNA vaccines as a proof-of-concept for future outbreaks. The model was thoroughly calibrated against multiple clinical datasets involving immune response to SARS-CoV-2 infection and mRNA vaccines in healthy and immunocompromised subjects (cancer patients undergoing therapy); the model showed robust clinical validation by accurately predicting neutralizing antibody kinetics, a correlate of vaccine-induced protection, in response to multiple doses of mRNA vaccines. Importantly, we estimated population vulnerability to breakthrough infections and predicted tailored vaccination dosing schedules to maximize protection and thus minimize breakthrough infections, based on the immune status of a sub-population. We have identified a critical waiting window for cancer patients (or, immunocompromised subjects) to allow recovery of the immune system (particularly CD4+ T-cells) for effective differentiation of B-cells to produce neutralizing antibodies and thus achieve optimal vaccine efficacy against variants of concern, especially between the first and second doses. Also, we have obtained optimized dosing schedules for subsequent doses in healthy and immunocompromised subjects, which vary from the CDC-recommended schedules, to minimize breakthrough infections. The developed modeling tool is based on generalized adaptive immune response to antigens and can thus be leveraged to guide vaccine dosing schedules during future outbreaks.

Recent insights into SARS-CoV-2 omicron variant

The SARS-CoV-2 omicron variant (B.1.1.529) was first identified in Botswana and South Africa, and its emergence has been associated with a steep increase in the number of SARS-CoV-2 infections. The omicron variant has subsequently spread very rapidly across the world, resulting in the World Health Organization classification as a variant of concern on 26 November 2021. Since its emergence, great efforts have been made by research groups around the world that have rapidly responded to fill our gaps in knowledge for this novel variant. A growing body of data has demonstrated that the omicron variant shows high transmissibility, robust binding to human angiotensin-converting enzyme 2 receptor, attenuated viral replication, and causes less severe disease in COVID-19 patients. Further, the variant has high environmental stability, high resistance against most therapeutic antibodies, and partial escape neutralisation by antibodies from convalescent patients or vaccinated individuals. With the pandemic ongoing, there is a need for the distillation of literature from primary research into an accessible format for the community. In this review, we summarise the key discoveries related to the SARS-CoV-2 omicron variant, highlighting the gaps in knowledge that guide the field's ongoing and future work.

Antigenic cartography of well-characterized human sera shows SARS-CoV-2 neutralization differences based on infection and vaccination history

The rapid emergence of SARS-CoV-2 variants challenges vaccination strategies. Here, we collected 201 serum samples from persons with a single infection or multiple vaccine exposures, or both. We measured their neutralization titers against 15 natural variants and 7 variants with engineered spike mutations and analyzed antigenic diversity. Antigenic maps of primary infection sera showed that Omicron sublineages BA.2, BA.4/BA.5, and BA.2.12.1 are distinct from BA.1 and more similar to Beta/Gamma/Mu variants. Three mRNA COVID-19 vaccinations increased neutralization of BA.1 more than BA.4/BA.5 or BA.2.12.1. BA.1 post-vaccination infection elicited higher neutralization titers to all variants than three vaccinations alone, although with less neutralization to BA.2.12.1 and BA.4/BA.5. Those with BA.1 infection after two or three vaccinations had similar neutralization titer magnitude and antigenic recognition. Accounting for antigenic differences among variants when interpreting neutralization titers can aid the understanding of complex patterns in humoral immunity that informs the selection of future COVID-19 vaccine strains.

Exploring Highly Conserved Regions of SARS-CoV-2 Spike S2 Subunit as Targets for Fusion Inhibition Using Chimeric Proteins

Since the beginning of the COVID-19 pandemic, considerable efforts have been made to develop protective vaccines against SARS-CoV-2 infection. However, immunity tends to decline within a few months, and new virus variants are emerging with increased transmissibility and capacity to evade natural or vaccine-acquired immunity. Therefore, new robust strategies are needed to combat SARS-CoV-2 infection. The viral spike composed of S1 and S2 subunits mediates viral attachment and membrane fusion to infect the host cell. In this process, interaction between the highly conserved heptad repeat 1 and 2 regions (HR1 and HR2) of S2 is crucial and for this reason; these regions are promising targets to fight SARS-CoV-2. Here, we describe the design and characterization of chimeric proteins that structurally imitate the S2 HR1 region in a trimeric coiled-coil conformation. We biophysically characterized the proteins and determined their capacity to bind the HR2 region, as well as their inhibitory activity of SARS-CoV-2 infection in vitro. HR1 mimetic proteins showed conformational heterogeneity and a propensity to form oligomers. Moreover, their structure is composed of subdomains with varied stability. Interestingly, the full HR1 proteins showed high affinity for HR2-derived peptides and SARS-CoV-2 inhibitory activity, whereas smaller proteins mimicking HR1 subdomains had a decreased affinity for their complementary HR2 region and did not inhibit the virus. The results provide insight into effective strategies to create mimetic proteins with broad inhibitory activity and therapeutic potential against SARS-CoV-2.

The clinical effectiveness of REGEN-COV in SARS-CoV-2 infection with Omicron versus Delta variants

BACKGROUND

In vitro studies suggesting that REGEN-COV (casirivimab plus imdevimab monoclonal antibodies) had poor efficacy against Omicron-variant SARS-CoV-2 infection led to amendment of REGEN-COV's Emergency Use Authorization to recommend use only in regions without high Omicron prevalence. REGEN-COV's relative clinical effectiveness for Omicron is unknown.

METHODS AND FINDINGS

We conducted a retrospective cohort study of non-hospitalized adults who tested positive for SARS-CoV-2 by polymerase chain reaction at the University of Miami Health System from July 19 -November 21, 2021 (Delta period) and December 6, 2021 -January 7, 2022 (Omicron period). Subjects were stratified be REGEN-COV receipt within 72h of test positivity and by time period of infection. We constructed multivariable logistic regression models to assess the differential association of REGEN-COV receipt with hospitalization within 30 days (primary outcome) and ED presentation; all models included three exposure terms (REGEN-COV receipt, Omicron vs Delta period, interaction of REGEN-COV with time period) and potential confounders (vaccination status, vaccine boosting, cancer diagnosis). Our cohort consisted of 2,083 adults in the Delta period (213 [10.2%] received REGEN-COV) and 4,201 in the Omicron period (156 [3.7%] received REGEN-COV). Hospitalization was less common during the Omicron period than during Delta (0.9% vs 1.7%, p = 0.78) and more common for patients receiving REGEN-COV than not (5.7% vs 0.9%, p<0.001). After adjustment, we found no differential association of REGEN-COV use during Omicron vs Delta with hospitalization within 30d (adjusted odds ratio [95% confidence interval] for the interaction term: 2.31 [0.76-6.92], p = 0.13). Similarly, we found no differential association for hospitalization within 15d (2.45 [0.63-9.59], p = 0.20) or emergency department presentation within 30d (1.43 [0.57-3.51], p = 0.40) or within 15d (1.79 [0.65-4.82], p = 0.30).

CONCLUSIONS

Within the limitations of this study's power to detect a difference, we identified no differential effectiveness of REGEN-COV in the context of Omicron vs Delta SARS-CoV-2 infection.

Neutralizing antibodies to SARS-CoV-2 variants of concern including Delta and Omicron in subjects receiving mRNA-1273, BNT162b2, and Ad26.COV2.S vaccines

SARS-CoV-2 vaccines have contributed to the control of COVID-19 in some parts of the world. However, the constant emergence of variants of concern (VOCs) challenges the effectiveness of SARS-CoV-2 vaccines over time. In particular, Omicron contains a high number of mutations in the spike (S) protein gene, on which most vaccines were developed. In this study, we quantitated neutralizing antibodies in vaccine recipients at various times postvaccination using S protein-based pseudoviruses derived from wild type (WT) SARS-CoV-2 and five VOCs including Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529). We found that two-dose mRNA-1273 and BNT162b2 vaccines elicited robust neutralizing antibodies against WT, Alpha, Beta, Gamma, and Delta, but wanned after 6 months with a faster decline observed for BNT162b2. Both mRNA-1273 and BNT162b2 elicited weak neutralizing antibodies against Omicron. One dose of Ad26.COV2.S vaccine induced weaker neutralizing antibodies against WT and most VOCs than mRNA-1273 and BNT162b2 did but moderate neutralizing antibodies against Delta and Omicron, which lasted for 6 months. These results support current recommendations of the Centers for Disease Control and Prevention for a booster 5 months after full immunization with an mRNA-based vaccine and the use of an mRNA-based vaccine 2 months after Ad26.COV2.S vaccination.

Emergence of SARS-CoV-2 Omicron variant and strategies for tackling the infection

INTRODUCTION

Nowadays, emerging SARS-CoV-2 Omicron, the novel highly mutated VOC, has quickly spread as the dominant variant in over 190 countries worldwide through the first part of 2022, which is influencing the infectivity, transmissibility, pathogenicity, and severity of COVID-19 pandemic. Additionally, clinical cases and experimental studies have reported that Omicron variant likely leads to weakened immune protection elicited by infection, antibody therapies, and vaccines. The new wave, from late February, 2022, was escalated abruptly by higher levels of transmission of Omicron BA.2 sublineage in China.

METHODS AND RESULTS

Following a systematic database search, this review summarizes the salient features of Omicron sublineages, and their impact on transmissibility, disease severity as well as the efficacy of the available vaccines and treatment against the Omicron.

CONCLUSION

We hope this study will provide a scientific reference for alleviating the burden of COVID-19.

The humoral and cellular immune evasion of SARS-CoV-2 Omicron and sub-lineages

The recently discovered SARS-CoV-2 variant Omicron (B.1.1.529) has rapidly become a global public health issue. The substantial mutations in the spike protein in this new variant have raised concerns about its ability to escape from pre-existing immunity established by natural infection or vaccination. In this review, we give a summary of current knowledge concerning the antibody evasion properties of Omicron and its subvariants (BA.2, BA.2.12.1, BA.4/5, and BA.2.75) from therapeutic monoclonal antibodies and the sera of SARS-CoV-2 vaccine recipients or convalescent patients. We also summarize whether vaccine-induced cellular immunity (memory B cell and T cell response) can recognize Omicron specifically. In brief, the Omicron variants demonstrated remarkable antibody evasion, with even more striking antibody escape seen in the Omicron BA.4 and BA.5 sub-lineages. Luckily, the third booster vaccine dose significantly increased the neutralizing antibodies titers, and the vaccine-induced cellular response remains conserved and provides second-line defense against the Omicron.

Pre-exposure prophylaxis with tixagevimab and cilgavimab (Evusheld) for COVID-19 among 1112 severely immunocompromised patients

OBJECTIVE

Immunocompromised patients have an increased risk of a severe form of COVID-19. The clinical efficacy of the tixagevimab/cilgavimab monoclonal antibody combination as pre-exposure prophylaxis against BA.1 and BA.2 SARS-CoV-2 Omicron sublineages is unknown. We aimed to describe the incidence and outcomes of COVID-19 among immunocompromised patients receiving tixagevimab/cilgavimab as preexposure prophylaxis during the Omicron wave in France.

METHODS

This was an observational multicentre cohort study of immunocompromised patients receiving tixagevimab/cilgavimab as preexposure prophylaxis between December 28, 2021 and March 31, 2022. Patients received tixagevimab/cilgavimab 150/150 mg intramuscularly if they had impaired vaccine response and a high risk of severe form of COVID-19.

RESULTS

Tixagevimab/cilgavimab was administered to 1112 immunocompromised patients. After a median (range) follow-up of 63 (49-73) days, COVID-19 was confirmed in 49/1112 (4.4%) ≥5 days after treatment. During the study period, mean weekly incidence rate was 1669 in 100 000 inhabitants in Ile-de-France and 530 in 100 000 among patients who received tixagevimab/cilgavimab prophylaxis. Among infected patients, 43/49 (88%) had a mild-to-moderate form and 6/49 (12%) had a moderate-to-severe form of COVID-19. Patients with moderate-to-severe illnesses were less likely to have received early therapies than patients with mild forms (53.5% vs. 16.7% respectively) and 2/49 (4%) patients died from COVID-19.

DISCUSSION

Our study reported a low rate of infections and severe illnesses among immunocompromised patients treated with tixagevimab/cilgavimab. A global preventive strategy including vaccines, preexposure prophylaxis with monoclonal antibodies, and early therapies might be effective to prevent severe forms of COVID-19 among severely immunocompromised patients.

Novel chimeric proteins mimicking SARS-CoV-2 spike epitopes with broad inhibitory activity

SARS-CoV-2 spike (S) protein mediates virus attachment to the cells and fusion between viral and cell membranes. Membrane fusion is driven by mutual interaction between the highly conserved heptad-repeat regions 1 and 2 (HR1 and HR2) of the S2 subunit of the spike. For this reason, these S2 regions are interesting therapeutic targets for COVID-19. Although HR1 and HR2 have been described as transiently exposed during the fusion process, no significant antibody responses against these S2 regions have been reported. Here we designed chimeric proteins that imitate highly stable HR1 helical trimers and strongly bind to HR2. The proteins have broad inhibitory activity against WT B.1 and BA.1 viruses. Sera from COVID-19 convalescent donors showed significant levels of reactive antibodies (IgG and IgA) against the HR1 mimetic proteins, whereas these antibody responses were absent in sera from uninfected donors. Moreover, both inhibitory activity and antigenicity of the proteins correlate positively with their structural stability but not with the number of amino acid changes in their HR1 sequences, indicating a conformational and conserved nature of the involved epitopes. Our results reveal previously undetected spike epitopes that may guide the design of new robust COVID-19 vaccines and therapies.

Optimization of Vaccination Clinics to Improve Staffing Decisions for COVID-19: A Time-Motion Study

As the COVID-19 pandemic disturbed people's daily life for more than 2 years, many COVID-19 vaccines have been carried forward systematically to curb the transmission of the virus. However, high vaccination tasks bring great challenges to personnel allocation. We observed nine vaccination clinics in Huzhou and Shanghai and built a discrete-event simulation model to simulate the optimal staffing of vaccination clinics under 10 different scenarios. Based on the result of the simulations, we optimized the allocation of vaccination staff in different stages of epidemic development by province in China. The results showed that optimizing staffing could both boost service utilization and shorten the queuing time for vaccination recipients. Taking Jilin Province as an example, to increase the booster vaccination rate within 3 months, the number of vaccination staff members needed was 2028, with a continuous small-scale breakout and 2,416 under a stable epidemic situation. When there was a shortage of vaccination staff, the total number of vaccination clinic staff members needed could be significantly reduced by combining the preview and registration steps. This study provides theoretical support for the personnel arrangement of COVID-19 vaccinations of a booster dose by province and the assessment of current vaccination staff reserves.

A flow cytometry-based neutralization assay for simultaneous evaluation of blocking antibodies against SARS-CoV-2 variants

Vaccines against SARS-CoV-2 have alleviated infection rates, hospitalization and deaths associated with COVID-19. In order to monitor humoral immunity, several serology tests have been developed, but the recent emergence of variants of concern has revealed the need for assays that predict the neutralizing capacity of antibodies in a fast and adaptable manner. Sensitive and fast neutralization assays would allow a timely evaluation of immunity against emerging variants and support drug and vaccine discovery efforts. Here we describe a simple, fast, and cell-free multiplexed flow cytometry assay to interrogate the ability of antibodies to prevent the interaction of Angiotensin-converting enzyme 2 (ACE2) and the receptor binding domain (RBD) of the original Wuhan-1 SARS-CoV-2 strain and emerging variants simultaneously, as a surrogate neutralization assay. Using this method, we demonstrate that serum antibodies collected from representative individuals at different time-points during the pandemic present variable neutralizing activity against emerging variants, such as Omicron BA.1 and South African B.1.351. Importantly, antibodies present in samples collected during 2021, before the third dose of the vaccine was administered, do not confer complete neutralization against Omicron BA.1, as opposed to samples collected in 2022 which show significant neutralizing activity. The proposed approach has a comparable performance to other established surrogate methods such as cell-based assays using pseudotyped lentiviral particles expressing the spike of SARS-CoV-2, as demonstrated by the assessment of the blocking activity of therapeutic antibodies (i.e. Imdevimab) and serum samples. This method offers a scalable, cost effective and adaptable platform for the dynamic evaluation of antibody protection in affected populations against variants of SARS-CoV-2.

Safety of anti-SARS-CoV-2 messenger RNA vaccine in lung cancer patients undergoing anticancer chemotherapy: A multicenter, prospective, observational, patient-reported outcome study

BACKGROUND

COVID-19 incidence is high in patients with cancer. The fatality rate was high for the Delta variant, necessitating infection prevention by vaccination. This study evaluated the safety of a SARS-CoV-2 vaccine in patients with advanced lung cancer receiving anticancer therapy.

METHODS

We prospectively enrolled patients receiving anticancer drugs for advanced lung cancer and planning SARS-CoV-2 vaccination. Early side effects within 7 days of vaccination were evaluated using patient-reported outcome (PRO) surveys. Chi-square test and multivariate logistic regression analyses were used.

RESULTS

Post-vaccination PROs were collected from 406 patients (252 were males). The mean age was 72 years. Treatment at the time of initial vaccination included chemotherapy, immune checkpoint inhibitors (ICI), a combination of chemotherapy and ICI, targeted therapy including tyrosine kinase inhibitors, and others in 115, 93, 45, 147, and six cases, respectively. The vaccines administered were BNT162b2 and mRNA273 in 361 and three cases, respectively and unknown in 42 cases. A total of 16.1% of patients developed fever (38°C) after the second mRNA vaccination (95% confidence interval: 12.6%-20.1%). This rate is comparable to data previously reported in 120 patients and slightly higher than that of healthy participants of the BNT162b2 study. Patients receiving treatment with cytotoxic anticancer agents were more likely to have high fever. Multivariate analysis showed no correlation between fever frequency and patient background. No serious initial adverse events due to vaccination were observed.

CONCLUSIONS

Anti-SARS-CoV-2 mRNA vaccination is safe; however, post-vaccination fever is more common in patients undergoing lung cancer treatment than in healthy individuals.

Quantifying the impact of immune history and variant on SARS-CoV-2 viral kinetics and infection rebound: A retrospective cohort study

Background

The combined impact of immunity and SARS-CoV-2 variants on viral kinetics during infections has been unclear.

Methods

We characterized 1,280 infections from the National Basketball Association occupational health cohort identified between June 2020 and January 2022 using serial RT-qPCR testing. Logistic regression and semi-mechanistic viral RNA kinetics models were used to quantify the effect of age, variant, symptom status, infection history, vaccination status and antibody titer to the founder SARS-CoV-2 strain on the duration of potential infectiousness and overall viral kinetics. The frequency of viral rebounds was quantified under multiple cycle threshold (Ct) value-based definitions.

Results

Among individuals detected partway through their infection, 51.0% (95% credible interval [CrI]: 48.3-53.6%) remained potentially infectious (Ct <30) 5 days post detection, with small differences across variants and vaccination status. Only seven viral rebounds (0.7%; N=999) were observed, with rebound defined as 3+days with Ct <30 following an initial clearance of 3+days with Ct ≥30. High antibody titers against the founder SARS-CoV-2 strain predicted lower peak viral loads and shorter durations of infection. Among Omicron BA.1 infections, boosted individuals had lower pre-booster antibody titers and longer clearance times than non-boosted individuals.

Conclusions

SARS-CoV-2 viral kinetics are partly determined by immunity and variant but dominated by individual-level variation. Since booster vaccination protects against infection, longer clearance times for BA.1-infected, boosted individuals may reflect a less effective immune response, more common in older individuals, that increases infection risk and reduces viral RNA clearance rate. The shifting landscape of viral kinetics underscores the need for continued monitoring to optimize isolation policies and to contextualize the health impacts of therapeutics and vaccines.

Funding

Supported in part by CDC contract #200-2016-91779, a sponsored research agreement to Yale University from the National Basketball Association contract #21-003529, and the National Basketball Players Association.

An efficient approach for SARS-CoV-2 monoclonal antibody production via modified mRNA-LNP immunization

Throughout the COVID-19 pandemic, many prophylactic and therapeutic drugs have been evaluated and introduced. Among these treatments, monoclonal antibodies (mAbs) that bind to and neutralize SARS-CoV-2 virus have been applied as complementary and alternative treatments to vaccines. Although different methodologies have been utilized to produce mAbs, traditional hybridoma fusion technology is still commonly used for this purpose due to its unmatched performance record. In this study, we coupled the hybridoma fusion strategy with mRNA-lipid nanoparticle (LNP) immunization. This time-saving approach can circumvent biological and technical hurdles, such as difficult-to-express membrane proteins, antigen instability, and the lack of posttranslational modifications on recombinant antigens. We used mRNA-LNP immunization and hybridoma fusion technology to generate mAbs against the receptor binding domain (RBD) of SARS-CoV-2 spike (S) protein. Compared with traditional protein-based immunization approaches, inoculation of mice with RBD mRNA-LNP induced higher titers of serum antibodies and markedly increased serum neutralizing activity. The mAbs we obtained can bind to SARS-CoV-2 RBDs from several variants. Notably, RBD-mAb-3 displayed particularly high binding affinities and neutralizing potencies against both Alpha and Delta variants. In addition to introducing specific mAbs against SARS-CoV-2, our data generally demonstrate that mRNA-LNP immunization may be useful to quickly generate highly functional mAbs against emerging infectious diseases.

Effect of Vaccination Time Intervals on SARS-COV-2 Omicron Variant Strain Infection in Guangzhou: A Real-World Matched Case–Control Study

In April 2022, a COVID-19 outbreak caused by the Omicron variant emerged in Guangzhou. A case–control study was conducted to explore the relationship between vaccination intervals and SARS-CoV-2 infection in the real world. According to the vaccination dose and age information of the cases, a 1:4 matched case–control sample was established, finally including n = 242 for the case group and n = 968 for the control group. The results indicated that among the participants who received three vaccine doses, those with an interval of more than 300 days between the receipt of the first vaccine dose and infection (or the first contact with a confirmed case) were less likely to be infected with SARS-CoV-2 than those with an interval of less than 300 days (OR = 0.67, 95% CI = 0.46–0.99). After age-stratified analysis, among participants aged 18–40 years who received two doses of vaccine, those who received the second dose more than 30 days after the first dose were less likely to be infected with SARS-CoV-2 (OR = 0.53, 95% CI = 0.30–0.96). Our findings suggest that we need to extend the interval between the first dose and the second dose and further explore the optimal interval between the first and second and between the second and third doses in order to improve vaccine efficacy.