SARS-CoV-2 Spike receptor-binding domain entrapped in mannose-conjugated chitosan nanoparticle vaccine delivered intranasal elicits local and systemic Th1 and Th2 immune responses in mice and antiviral efficacy in Syrian hamsters (preprint)

Given the ongoing COVID-19 pandemic and the need to build sustainable herd immunity in the population, the search for novel and safe vaccines for easy mass vaccination is an urgent task. We developed a novel intranasal subunit vaccine called NARUVAX-C19/Nano which is based on the SARS-CoV-2 spike protein receptor-binding domain (RBD) entrapped in mannose-conjugated chitosan nanoparticles (NP). To potentiate the cell mediated cell immune responses by the NP-vaccine formulation included the adjuvant CpG55.2, a toll-like receptor 9 agonist. The vaccine candidates administered intranasal were assessed for immunogenicity, protective efficacy, and virus transmission from vaccinates in inmates. The results were compared with a soluble RBD mixed with alum adjuvant vaccine administered intramuscular. In BALB/c mice administered with both the NP vaccines intranasal twice induced secretory IgA antibodies and pronounced Th1-cell responses, that was absent in intramuscular alum-adjuvanted RBD vaccine group. In Syrian hamsters delivered with similar NP formulations provided protection against a wild-type SARS-CoV-2 (D614G) challenge infection, indicated by significantly rescue in weight loss, reduced viral load in respiratory organs and lung pathology. However, despite significantly reduced viral load in the nasal turbinates and oropharyngeal swabs in NP vaccinated hamsters the virus transmission to naïve sentinel animals could not be blocked. In conclusion, intranasal delivered RBD-based NP vaccine formulations induced mucosal immune responses in mice and protected Syrian hamsters against SARS-CoV-2 infection. These findings are encouraging and supportive for further investigations to develop an intranasal NP-based vaccine platform to mitigate SARS-CoV-2 infection.

A Spike protein-based subunit SARS-CoV-2 vaccine for pets: safety, immunogenicity, and protective efficacy in juvenile cats (preprint)

Whereas multiple vaccine types have been developed to curb the spread of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) among humans, there are very few vaccines being developed for animals including pets. To combat the threat of human-to-animal, animal-to-animal and animal-to-human transmission and the generation of new virus variants, we developed a subunit SARS-CoV-2 vaccine which is based on recombinant spike protein extracellular domain expressed in insect cells then formulated with appropriate adjuvants. Sixteen 8-12-week-old outbred female and male kittens (n=4/group) were randomly assigned into four treatment groups: Group 1, Antigen alone; Group 2, Sepivac SWE™ adjuvant; Group 3, aluminum hydroxide adjuvant; Group 4, PBS administered control animals. All animals were vaccinated twice at day 0 and 14, intramuscularly in a volume of 0.5 mL (Groups 1-3: 5 µg of Spike protein). On days 0 and 28 serum samples were collected to evaluate anti-spike IgG, inhibition of spike binding to angiotensin-converting enzyme 2 (ACE-2), neutralizing antibodies to Wuhan-01 SARS-CoV-2 D614G (wild-type) and Delta variant viruses, and whole blood for hematology studies. At day 28, all groups were challenged with SARS-CoV-2 wild-type virus 10 6 TCID 50 intranasally. On day 31, tissue samples (lung, heart, and nasal turbinates) were collected for histology, viral RNA detection and virus titration. Parameters evaluated in this study included safety, immunogenicity, and protection from infection with wild-type SARS-CoV-2 virus. After two immunizations, both vaccines induced high titers of serum anti-spike IgG, ACE-2 binding inhibitory and neutralizing antibodies against both wild-type and Delta variant virus in the juvenile cats. Both subunit vaccines provided protection of juvenile cats against virus shedding from the upper respiratory tract, and against viral replication in the lower respiratory tract and hearts. These promising data warrant ongoing evaluation of the vaccine’s ability to protect cats against SARS-CoV-2 Delta variant and in particular to prevent transmission of the infection to naïve cats, before proceeding with large-scale field trials.

Disproportionality analysis of adverse neurological and psychiatric reactions with the ChAdOx1 (Oxford-AstraZeneca) and BNT162b2 (Pfizer-BioNTech) COVID-19 vaccines in the United Kingdom (preprint)

ObjectiveThe information on neurologic or psychiatric adverse reactions to the COVID-19 vaccines is limited. Our objective was to examine the odds of neurological and psychiatric adverse reactions to BNT162b2 (Pfizer-BioNTech) and ChAdOx1 (Oxford-AstraZeneca) COVID-19 vaccines. MethodsWe analyzed all Adverse Vaccine Reaction reports to the United Kingdom Medicines and Healthcare products Regulatory Agency between December 9, 2020 and June 30, 2021 that mentioned the BNT162b2 or ChAdOx1 vaccines. We compared the rates of adverse neurological and psychiatric reactions with ChAdOx1 to those with BNT162b2. P-values were obtained by a Bonferroni-adjusted Z-test for proportions. ResultsAs of June 30, 2021, 53.2 M doses of ChAdOx1 and 46.1 M doses of BNT162b2 had been administered. We extracted information from 300,518 distinct reports. The number of individual adverse neurologic or psychiatric reaction reports were less than 200/M doses administered, except headache which was reported in 1,550 and 395 cases/M doses of ChAdOx1 and BNT162b2, respectively. Compared to BNT162b2, cerebral hemorrhagic or thrombotic events, headaches and migraines, Guillain-Barre syndrome and paresthesias, tremor and freezing, delirium, hallucinations, nervousness, poor sleep quality, and postural dizziness were more frequently reported with ChAdOx1. Reactions more frequently reported with BNT162b2 than ChAdOx1 were Bells palsy, facial paralysis, dysgeusia, anxiety, and presyncope or syncope. ConclusionSignificant differences in the neurologic and psychiatric adverse event profiles of the ChAdOx1 and BNT162b2 vaccines may exist, emphasizing the need for additional research. The beneficial and protective effects of the COVID-19 vaccines far outweigh the low potential risk of neurologic and psychiatric reactions.

An adjuvanted subunit SARS-CoV-2 spike protein vaccine provides protection against Covid-19 infection and transmission (preprint)

Recombinant protein approaches offer major promise for safe and effective vaccine prevention of SARS-CoV-2 infection. We developed a recombinant spike protein vaccine (called NARUVAX-C19) and characterized its ability when formulated with a nanoemulsion adjuvant to induce anti-spike antibody and T-cell responses and provide protection including against viral transmission in rodent. In mice, NARUVAX-C19 vaccine administered intramuscularly twice at 21-day interval elicited balanced Th1/Th2 humoral and T-cell responses with high titers of neutralizing antibodies against wild-type (D614G) and delta (B.1.617.2) variants. In Syrian hamsters, NARUVAX-C19 provided complete protection against wild-type (D614G) infection and prevented its transmission to naïve animals placed in the same cage as challenged animals. The results contrasted with only weak protection seen with a monomeric spike receptor binding domain (RBD) vaccine even when formulated with the same adjuvant. These encouraging results warrant ongoing development of this Covid-19 vaccine candidate.

Immunisation of ferrets and mice with recombinant SARS-CoV-2 spike protein formulated with Advax-SM adjuvant protects against COVID-19 infection (preprint)

The development of a safe and effective vaccine is a key requirement to overcoming the COVID-19 pandemic. Recombinant proteins represent the most reliable and safe vaccine approach but generally require a suitable adjuvant for robust and durable immunity. We used the SARS-CoV-2 genomic sequence and in silico structural modelling to design a recombinant spike protein vaccine (Covax-19). A synthetic gene encoding the spike extracellular domain (ECD) was inserted into a baculovirus backbone to express the protein in insect cell cultures. The spike ECD was formulated with Advax-SM adjuvant and first tested for immunogenicity in C57BL/6 and BALB/c mice. The Advax-SM adjuvanted vaccine induced high titers of binding antibody against spike protein that were able to neutralise the original wildtype virus on which the vaccine was based as well as the variant B.1.1.7 lineage virus. The Covax-19 vaccine also induced potent spike-specific CD4+ and CD8+ memory T-cells with a dominant Th1 phenotype, and this was shown to be associated with cytotoxic T lymphocyte killing of spike labelled target cells in vivo. Ferrets immunised with Covax-19 vaccine intramuscularly twice 2 weeks apart made spike receptor binding domain (RBD) IgG and were protected against an intranasal challenge with SARS-CoV-2 virus 2 weeks after the second immunisation. Notably, ferrets that received two 25 or 50ug doses of Covax-19 vaccine had no detectable virus in their lungs or in nasal washes at day 3 post-challenge, suggesting the possibility that Covax-19 vaccine may in addition to protection against lung infection also have the potential to block virus transmission. This data supports advancement of Covax-19 vaccine into human clinical trials.

Computationally repurposed drugs and natural products against RNA dependent RNA polymerase as potential COVID-19 therapies (preprint)

For fast development of COVID-19, it is only feasible to use drugs (off label use) or approved natural products that are already registered or been assessed for safety in previous human trials. These agents can be quickly assessed in COVID-19 patients, as their safety and pharmacokinetics should already be well understood. Computational methods offer promise for rapidly screening such products for potential SARS-CoV-2 activity by predicting and ranking the affinities of these compounds for specific virus protein targets. The RNA-dependent RNA polymerase (RdRP) is a promising target for SARS-CoV-2 drug development given it has no human homologs making RdRP inhibitors potentially safer, with fewer off-target effects that drugs targeting other viral proteins. We combined robust Vina docking on RdRP with molecular dynamic (MD) simulation of the top 80 identified drug candidates to yield a list of the most promising RdRP inhibitors. Literature reviews revealed that many of the predicted inhibitors had been shown to have activity in in vitro assays or had been predicted by other groups to have activity. The novel hits revealed by our screen can now be conveniently tested for activity in RdRP inhibition assays and if conformed testing for antiviral activity invitro before being tested in human trials

Computational screening of repurposed drugs and natural products against SARS-Cov-2 main protease (Mpro) as potential COVID-19 therapies (preprint)

There remains an urgent need to identify existing drugs that might be suitable for treating patients suffering from COVID-19 infection. Drugs rarely act at a single molecular target, with off target effects often being responsible for undesirable side effects and sometimes, beneficial synergy between targets for a specific illness. Off target activities have also led to blockbuster drugs in some cases, e.g. Viagra for erectile dysfunction and Minoxidil for male pattern hair loss. Drugs already in use or in clinical trials plus approved natural products constitute a rich resource for discovery of therapeutic agents that can be repurposed for existing and new conditions, based on the rationale that they have already been assessed for safety in man. A key question then is how to rapidly and efficiently screen such compounds for activity against new pandemic pathogens such as COVID-19. Here we show how a fast and robust computational process can be used to screen large libraries of drugs and natural compounds to identify those that may inhibit the main protease of SARS-Cov-2 (3CL pro, Mpro). We show how the resulting shortlist of candidates with strongest binding affinities is highly enriched in compounds that have been independently identified as potential antivirals against COVID-19. The top candidates also include a substantial number of drugs and natural products not previously identified as having potential COVID-19 activity, thereby providing additional targets for experimental validation. This in silico screening pipeline may also be useful for repurposing of existing drugs and discovery of new drug candidates against other medically important pathogens and for use in future pandemics.

In silico comparison of spike protein-ACE2 binding affinities across species; significance for the possible origin of the SARS-CoV-2 virus (preprint)

The devastating impact of the COVID-19 pandemic caused by SARS coronavirus 2 (SARS CoV 2) has raised important questions about viral origin, mechanisms of zoonotic transfer to humans, whether companion or commercial animals can act as reservoirs for infection, and why there are large variations in SARS-CoV-2 susceptibilities across animal species. Powerful in silico modelling methods can rapidly generate information on newly emerged pathogens to aid countermeasure development and predict future behaviours. Here we report an in silico structural homology modelling, protein-protein docking, and molecular dynamics simulation study of the key infection initiating interaction between the spike protein of SARS-Cov-2 and its target, angiotensin converting enzyme 2 (ACE2) from multiple species. Human ACE2 has the strongest binding interaction, significantly greater than for any species proposed as source of the virus. Binding to pangolin ACE2 was the second strongest, possibly due to the SARS-CoV-2 spike receptor binding domain (RBD) being identical to pangolin CoV spike RDB. Except for snake, pangolin and bat for which permissiveness has not been tested, all those species in the upper half of the affinity range (human, monkey, hamster, dog, ferret) have been shown to be at least moderately permissive to SARS-CoV-2 infection, supporting a correlation between binding affinity and permissiveness. Our data indicates that the earliest isolates of SARS-CoV-2 were surprisingly well adapted to human ACE2, potentially explaining its rapid transmission.