The ChAdOx1 vectored vaccine, AZD2816, induces strong immunogenicity against SARS-CoV-2 beta (B.1.351) and other variants of concern in preclinical studies

Preclinical immune efficacy against SARS-CoV-2 beta B.1.351 variant by MVA-based vaccine candidates

The constant appearance of new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VoCs) has jeopardized the protective capacity of approved vaccines against coronavirus disease-19 (COVID-19). For this reason, the generation of new vaccine candidates adapted to the emerging VoCs is of special importance. Here, we developed an optimized COVID-19 vaccine candidate using the modified vaccinia virus Ankara (MVA) vector to express a full-length prefusion-stabilized SARS-CoV-2 spike (S) protein, containing 3 proline (3P) substitutions in the S protein derived from the beta (B.1.351) variant, termed MVA-S(3Pbeta). Preclinical evaluation of MVA-S(3Pbeta) in head-to-head comparison to the previously generated MVA-S(3P) vaccine candidate, expressing a full-length prefusion-stabilized Wuhan S protein (with also 3P substitutions), demonstrated that two intramuscular doses of both vaccine candidates fully protected transgenic K18-hACE2 mice from a lethal challenge with SARS-CoV-2 beta variant, reducing mRNA and infectious viral loads in the lungs and in bronchoalveolar lavages, decreasing lung histopathological lesions and levels of proinflammatory cytokines in the lungs. Vaccination also elicited high titers of anti-S Th1-biased IgGs and neutralizing antibodies against ancestral SARS-CoV-2 Wuhan strain and VoCs alpha, beta, gamma, delta, and omicron. In addition, similar systemic and local SARS-CoV-2 S-specific CD4+ and CD8+ T-cell immune responses were elicited by both vaccine candidates after a single intranasal immunization in C57BL/6 mice. These preclinical data support clinical evaluation of MVA-S(3Pbeta) and MVA-S(3P), to explore whether they can diversify and potentially increase recognition and protection of SARS-CoV-2 VoCs.

Immunogenicity and safety of AZD2816, a beta (B.1.351) variant COVID-19 vaccine, and AZD1222 (ChAdOx1 nCoV-19) as third-dose boosters for previously vaccinated adults: a multicentre, randomised, partly double-blinded, phase 2/3 non-inferiority immunobridging study in the UK and Poland

BACKGROUND

This study aimed to evaluate AZD2816, a variant-updated COVID-19 vaccine expressing the full-length SARS-CoV-2 beta (B.1.351) variant spike protein that is otherwise similar to AZD1222 (ChAdOx1 nCoV-19), and AZD1222 as third-dose boosters.

METHODS

This phase 2/3, partly double-blinded, randomised, active-controlled study was done at 19 sites in the UK and four in Poland. Adult participants who had received a two-dose AZD1222 or mRNA vaccine primary series were randomly assigned by means of an Interactive Response Technology-Randomisation and Trial Supply Management system (1:1 within each primary-series cohort, stratified by age, sex, and comorbidities) to receive AZD1222 or AZD2816 (intramuscular injection; 5 × 1010 viral particles). Participants, investigators, and all sponsor staff members involved in study conduct were masked to randomisation. AZD1222 and AZD2816 doses were prepared by unmasked study staff members. The primary objectives were to evaluate safety and humoral immunogenicity (non-inferiority of day-29 pseudovirus neutralising antibody geometric mean titre [GMT] against ancestral SARS-CoV-2: AZD1222 booster vs AZD1222 primary series [historical controls]; margin 0·67; SARS-CoV-2-seronegative participants). This study is registered with ClinicalTrials.gov, NCT04973449, and is completed.

FINDINGS

Between June 27 and Sept 30, 2021, 1394 participants of the 1741 screened were randomly assigned to AZD1222 or AZD2816 following an AZD1222 (n=373, n=377) or mRNA vaccine (n=322, n=322) primary series. In SARS-CoV-2-seronegative participants receiving AZD1222 or AZD2816, 78% and 80% (AZD1222 primary series) and 90% and 93%, respectively (mRNA vaccine primary series) reported solicited adverse events to the end of day 8; 2%, 2%, 1%, and 1% had serious adverse events and 12%, 12%, 10%, and 11% had adverse events of special interest, respectively, to the end of day 180. The primary immunogenicity non-inferiority endpoint was met: day-29 neutralising antibody GMT ratios (ancestral SARS-CoV-2) were 1·02 (95% CI 0·90-1·14) and 3·47 (3·09-3·89) with AZD1222 booster versus historical controls (AZD1222 and mRNA vaccine primary series, respectively). Responses against beta were greater with AZD2816 versus AZD1222 (GMT ratios, AZD1222, mRNA vaccine primary series 1·84 [1·63-2·08], 2·22 [1·99-2·47]).

INTERPRETATION

Both boosters were well tolerated, with immunogenicity against ancestral SARS-CoV-2 similar to AZD1222 primary-series vaccination. AZD2816 gave greater immune responses against beta versus AZD1222.

FUNDING

AstraZeneca.

ChAdOx1 COVID vaccines express RBD open prefusion SARS-CoV-2 spikes on the cell surface

Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been proven to be an effective means of decreasing COVID-19 mortality, hospitalization rates, and transmission. One of the vaccines deployed worldwide is ChAdOx1 nCoV-19, which uses an adenovirus vector to drive the expression of the original SARS-CoV-2 spike on the surface of transduced cells. Using cryo-electron tomography and subtomogram averaging, we determined the native structures of the vaccine product expressed on cell surfaces in situ. We show that ChAdOx1-vectored vaccines expressing the Beta SARS-CoV-2 variant produce abundant native prefusion spikes predominantly in one-RBD-up conformation. Furthermore, the ChAdOx1-vectored HexaPro-stabilized spike yields higher cell surface expression, enhanced RBD exposure, and reduced shedding of S1 compared to the wild type. We demonstrate in situ structure determination as a powerful means for studying antigen design options in future vaccine development against emerging novel SARS-CoV-2 variants and broadly against other infectious viruses.

Preclinical evaluation of a SARS-CoV-2 variant B.1.351-based candidate DNA vaccine

The SARS-CoV-2 pandemic revealed the critical shortfalls of global vaccine availability for emergent pathogens and the need for exploring additional vaccine platforms with rapid update potential in response to new variants. Thus, it remains essential, for the present evolving SARS-CoV-2/Covid-19 and future pandemics, to continuously develop and characterize new and different vaccine platforms. Here, we describe an expression-optimized DNA vaccine candidate based on the SARS-CoV-2 spike protein of the Beta variant (B.1.351), pNTC-Spike.351, and, in animal models, compare its immunogenicity with a similar DNA vaccine encoding the ancestral index strain spike protein, pNTC-Spike. Both DNA vaccines induced neutralizing antibodies and a Th1 biased immune response. In contrast to the index-specific vaccine, the Beta-specific DNA vaccine induced antibodies in mice and rabbits that, even at low levels, efficiently neutralize the otherwise antibody resistant Beta variant. It similarly neutralized unrelated variants bearing the neutralization resistant E484K spike mutation. Intensive priming using two vaccinations with pNTC-Spike and a single booster immunization with the pNTC-Spike.351 induced a more robust neutralizing antibody response with comparable magnitude against different variants of concern. Thus, DNA vaccine technology with heterologous spike protein prime-boost should be explored further using the Beta derived pNTC-Spike.351 to broaden neutralizing antibody responses against emerging variants of concern.

Atypical B cells and impaired SARS-CoV-2 neutralization following heterologous vaccination in the elderly

Suboptimal responses to a primary vaccination course have been reported in the elderly, but there is little information regarding the impact of age on responses to booster third doses. Here, we show that individuals 70 years or older (median age 73, range 70-75) who received a primary two-dose schedule with AZD1222 and booster third dose with mRNA vaccine achieve significantly lower neutralizing antibody responses against SARS-CoV-2 spike pseudotyped virus compared with those younger than 70 (median age 66, range 54-69) at 1 month post booster. Impaired neutralization potency and breadth post third dose in the elderly is associated with circulating "atypical" spike-specific B cells expressing CD11c and FCRL5. However, when considering individuals who received three doses of mRNA vaccine, we did not observe differences in neutralization or enrichment in atypical B cells. This work highlights the finding that AdV and mRNA COVID-19 vaccine formats differentially instruct the memory B cell response.

The End or a New Era of Development of SARS-CoV-2 Virus: Genetic Variants Responsible for Severe COVID-19 and Clinical Efficacy of the Most Commonly Used Vaccines in Clinical Practice

Although the chief of the World Health Organization (WHO) has declared the end of the coronavirus disease 2019 (COVID-19) as a global health emergency, the disease is still a global threat. To be able to manage such pandemics in the future, it is necessary to develop proper strategies and opportunities to protect human life. The data on the SARS-CoV-2 virus must be continuously analyzed, and the possibilities of mutation and the emergence of new, more infectious variants must be anticipated, as well as the options of using different preventive and therapeutic techniques. This is because the fast development of severe acute coronavirus 2 syndrome (SARS-CoV-2) variants of concern have posed a significant problem for COVID-19 pandemic control using the presently available vaccinations. This review summarizes data on the SARS-CoV-2 variants that are responsible for severe COVID-19 and the clinical efficacy of the most commonly used vaccines in clinical practice. The consequences after the disease (long COVID or post-COVID conditions) continue to be the subject of studies and research, and affect social and economic life worldwide.

Immunogenicity and protective efficacy of SARS-CoV-2 mRNA vaccine encoding secreted non-stabilized spike in female mice

Establishment of an mRNA vaccine platform in low- and middle-income countries (LMICs) is important to enhance vaccine accessibility and ensure future pandemic preparedness. Here, we describe the preclinical studies of "ChulaCov19", a SARS-CoV-2 mRNA encoding prefusion-unstabilized ectodomain spike protein encapsulated in lipid nanoparticles (LNP). In female BALB/c mice, ChulaCov19 at 0.2, 1, 10, and 30 μg elicits robust neutralizing antibody (NAb) and T cell responses in a dose-dependent relationship. The geometric mean titers (GMTs) of NAb against wild-type (WT, Wuhan-Hu1) virus are 1,280, 11,762, 54,047, and 62,084, respectively. Higher doses induce better cross-NAb against Delta (B.1.617.2) and Omicron (BA.1 and BA.4/5) variants. This elicited immunogenicity is significantly higher than those induced by homologous CoronaVac or AZD1222 vaccination. In a heterologous prime-boost study, ChulaCov19 booster dose generates a 7-fold increase of NAb against Wuhan-Hu1 WT virus and also significantly increases NAb response against Omicron (BA.1 and BA.4/5) when compared to homologous CoronaVac or AZD1222 vaccination. Challenge studies show that ChulaCov19 protects human-ACE-2-expressing female mice from COVID-19 symptoms, prevents viremia and significantly reduces tissue viral load. Moreover, anamnestic NAb response is undetectable in challenge animals. ChulaCov19 is therefore a promising mRNA vaccine candidate either as a primary or boost vaccination and has entered clinical development.

Adenoviral vectored vaccination protects against Crimean-Congo Haemorrhagic Fever disease in a lethal challenge model

BACKGROUND

The tick-borne bunyavirus, Crimean-Congo Haemorrhagic Fever virus (CCHFV), can cause severe febrile illness in humans and has a wide geographic range that continues to expand due to tick migration. Currently, there are no licensed vaccines against CCHFV for widespread usage.

METHODS

In this study, we describe the preclinical assessment of a chimpanzee adenoviral vectored vaccine (ChAdOx2 CCHF) which encodes the glycoprotein precursor (GPC) from CCHFV.

FINDINGS

We demonstrate here that vaccination with ChAdOx2 CCHF induces both a humoral and cellular immune response in mice and 100% protection in a lethal CCHF challenge model. Delivery of the adenoviral vaccine in a heterologous vaccine regimen with a Modified Vaccinia Ankara vaccine (MVA CCHF) induces the highest levels of CCHFV-specific cell-mediated and antibody responses in mice. Histopathological examination and viral load analysis of the tissues of ChAdOx2 CCHF immunised mice reveals an absence of both microscopic changes and viral antigen associated with CCHF infection, further demonstrating protection against disease.

INTERPRETATION

There is the continued need for an effective vaccine against CCHFV to protect humans from lethal haemorrhagic disease. Our findings support further development of the ChAd platform expressing the CCHFV GPC to seek an effective vaccine against CCHFV.

FUNDING

This research was supported by funding from the Biotechnology and Biological Sciences Research Council (UKRI-BBSRC) [BB/R019991/1 and BB/T008784/1].

Antiviral potential of anthraquinones from Polygonaceae, Rubiaceae and Asphodelaceae: Potent candidates in the treatment of SARS-COVID-19, A comprehensive review

Medicinal plants are being used as an alternative source of health management to cure various human ailments. The healing role is attributed to the hidden dynamic groups of various phytoconstituents, most of which have been recorded from plants and their derivatives. Nowadays, medicinal plants have gained more attention due to their pharmacological and industrial potential. Aromatic compounds are one of the dynamic groups of secondary metabolites (SM) naturally present in plants; and anthraquinones of this group are found to be attractive due to their high bioactivity and low toxicity. They have been reported to exhibit anticancer, antimicrobial, immune-suppressive, antioxidant, antipyretic, diuretic and anti-inflammatory activities. Anthraquinones have been also shown to exhibit potent antiviral effects against different species of viruses. Though, it has been reported that a medicinal plant with antiviral activity against one viral infection may be used to combat other types of viral infections. Therefore, in this review, we explored and highlighted the antiviral properties of anthraquinones of Polygonaceae, Rubiaceae and Asphodelaceae families. Anthraquinones from these plant families have been reported for their effects on human respiratory syncytial virus and influenza virus. They are hence presumed to have antiviral potential against SARS-CoV as well. Thus, anthraquinones are potential candidates that need to be screened thoroughly and developed as drugs to combat COVID-19. The information documented in this review could therefore serve as a starting point in developing novel drugs that may help to curb the SARS-COVID-19 pandemic.

COVID-19 vaccine update: vaccine effectiveness, SARS-CoV-2 variants, boosters, adverse effects, and immune correlates of protection

Coronavirus Disease 2019 (COVID-19) has been the most severe public health challenge in this century. Two years after its emergence, the rapid development and deployment of effective COVID-19 vaccines have successfully controlled this pandemic and greatly reduced the risk of severe illness and death associated with COVID-19. However, due to its ability to rapidly evolve, the SARS-CoV-2 virus may never be eradicated, and there are many important new topics to work on if we need to live with this virus for a long time. To this end, we hope to provide essential knowledge for researchers who work on the improvement of future COVID-19 vaccines. In this review, we provided an up-to-date summary for current COVID-19 vaccines, discussed the biological basis and clinical impact of SARS-CoV-2 variants and subvariants, and analyzed the effectiveness of various vaccine booster regimens against different SARS-CoV-2 strains. Additionally, we reviewed potential mechanisms of vaccine-induced severe adverse events, summarized current studies regarding immune correlates of protection, and finally, discussed the development of next-generation vaccines.

ChAdOx1 nCoV-19 (AZD1222) or nCoV-19-Beta (AZD2816) protect Syrian hamsters against Beta Delta and Omicron variants

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient simian adenovirus-vectored vaccine encoding the spike (S) protein of SARS-CoV-2, based on the first published full-length sequence (Wuhan-1). AZD1222 has been shown to have 74% vaccine efficacy against symptomatic disease in clinical trials. However, variants of concern (VoCs) have been detected, with substitutions that are associated with a reduction in virus neutralizing antibody titer. Updating vaccines to include S proteins of VoCs may be beneficial, even though current real-world data is suggesting good efficacy following boosting with vaccines encoding the ancestral S protein. Using the Syrian hamster model, we evaluate the effect of a single dose of AZD2816, encoding the S protein of the Beta VoC, and efficacy of AZD1222/AZD2816 as a heterologous primary series against challenge with the Beta or Delta variant. Minimal to no viral sgRNA could be detected in lungs of vaccinated animals obtained at 3- or 5- days post inoculation, in contrast to lungs of control animals. In Omicron-challenged hamsters, a single dose of AZD2816 or AZD1222 reduced virus shedding. Thus, these vaccination regimens are protective against the Beta, Delta, and Omicron VoCs in the hamster model.

Antigenicity comparison of SARS-CoV-2 Omicron sublineages with other variants contained multiple mutations in RBD

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, particularly those with multiple mutations in receptor-binding domain (RBD), pose a critical challenge to the efficacy of coronavirus disease 2019 (COVID-19) vaccines and therapeutic neutralizing monoclonal antibodies (mAbs). Omicron sublineages BA.1, BA.2, BA.3, as well as the recent emergence of C.1.2, B.1.630, B.1.640.1, and B.1.640.2, have multiple mutations in RBD and may lead to severe neutralizing antibody evasion. It is urgent to evaluate the antigenic change of the above seven variants against mAbs and sera from guinea pigs immunized with variants of concern (VOCs) (Alpha, Beta, Gamma, Delta, Omicron) and variants of interest (VOIs) (Lambda, Mu) immunogens. Only seven out of the 24 mAbs showed no reduction in neutralizing activity against BA.1, BA.2, and BA.3. However, among these seven mAbs, the neutralization activity of XGv337 and XGv338 against C.1.2, B.1.630, B.1.640.1, and B.1.640.2 were decreased. Therefore, only five neutralizing mAbs showed no significant change against these seven variants. Using VOCs and VOIs as immunogens, we found that the antigenicity of variants could be divided into three clusters, and each cluster showed similar antigenicity to different immunogens. Among them, D614G, B.1.640.1, and B.1.630 formed a cluster, C.1.2 and B.1.640.2 formed a cluster, and BA.1, BA.2, and BA.3 formed a cluster.

COVID-19 vaccines in patients with cancer: immunogenicity, efficacy and safety

Patients with cancer have a higher risk of severe coronavirus disease (COVID-19) and associated mortality than the general population. Owing to this increased risk, patients with cancer have been prioritized for COVID-19 vaccination globally, for both primary and booster vaccinations. However, given that these patients were not included in the pivotal clinical trials, considerable uncertainty remains regarding vaccine efficacy, and the extent of humoral and cellular immune responses in these patients, as well as the risks of vaccine-related adverse events. In this Review, we summarize the current knowledge generated in studies conducted since COVID-19 vaccines first became available. We also highlight critical points that might affect vaccine efficacy in patients with cancer in the future.

Efficacy of ChAdOx1 vaccines against SARS-CoV-2 Variants of Concern Beta, Delta and Omicron in the Syrian hamster model

ChAdOx1 nCoV-19 (AZD1222) is a replication-deficient simian adenovirusâ€"vectored vaccine encoding the spike (S) protein of SARS-CoV-2, based on the first published full-length sequence (Wuhan-1). AZD1222 was shown to have 74% vaccine efficacy (VE) against symptomatic disease in clinical trials and over 2.5 billion doses of vaccine have been released for worldwide use. However, SARS-CoV-2 continues to circulate and consequently, variants of concern (VoCs) have been detected, with substitutions in the S protein that are associated with a reduction in virus neutralizing antibody titer. Updating vaccines to include S proteins of VoCs may be beneficial over boosting with vaccines encoding the ancestral S protein, even though current real-world data is suggesting good efficacy against hospitalization and death following boosting with vaccines encoding the ancestral S protein. Using the Syrian hamster model, we evaluated the effect of a single dose of AZD2816, encoding the S protein of the Beta VoC, and efficacy of AZD1222/AZD2816 as a heterologous primary series against challenge with the Beta or Delta variant. We then investigated the efficacy of a single dose of AZD2816 or AZD1222 against the Omicron VoC. As seen previously, minimal to no viral sgRNA could be detected in lungs of vaccinated animals obtained at 5 days post inoculation, in contrast to lungs of control animals. Thus, these vaccination regimens are protective against the Beta, Delta, and Omicron VoCs in the hamster model.