A Spike Protein-Based Subunit SARS-CoV-2 Vaccine for Pets: Safety, Immunogenicity, and Protective Efficacy in Juvenile Cats

Detection and genomic characterization of an avian influenza virus A/mute swan/Mangystau/1-S24R-2/2024 (H5N1; clade 2.3.4.4b) strain isolated from the lung of a dead swan in Kazakhstan

The influenza virus strain A/mute swan/Mangystau/1-S24R-2/2024 (H5N1; clade 2.3.4.4b) was isolated in embryonated chicken eggs from the lung of a dead swan found around Lake Karakol (Kazakhstan) during a highly pathogenic avian influenza outbreak in 2024. The aim of this study was to characterize the genetic profile of the isolated strain.

Safety and immunogenicity of an adjuvanted recombinant spike protein-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine, SpikeVet™, in selected Carnivora, Primates and Artiodactyla in Australian zoos

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect a broad range of animal species and has been associated with severe disease in some taxa. Few studies have evaluated optimal strategies to mitigate the risk to susceptible zoo animals. This study evaluated the safety and immunogenicity of a protein-based veterinary SARS-CoV-2 vaccine (SpikeVet™) in zoo animals. Two to three doses of SpikeVet™ were administered intramuscularly or subcutaneously 3-4 weeks apart to 354 zoo animals representing 38 species. SpikeVet™ was very well tolerated across all species. Minor adverse effects were observed in 1.69% of animals vaccinated, or 1.04% of vaccine doses administered. Preliminary immunogenicity analyses in representative carnivores (meerkats, lions) and an artiodactylid (domestic goat) showed SpikeVet™-immunized animals developed serum antibodies able to neutralize a range of SARS-CoV-2 variants, including the vaccine-homologous Wuhan and Mu variants, as well as vaccine-heterologous Omicron BA.2 and XBB.1 strains. Prior to vaccination, all eight lions were seropositive for Wuhan strain by surrogate viral neutralization testing, suggesting past infection with SARS-CoV-2 or cross-reactive antibodies generated by another closely related coronavirus. These results from a range of zoo species support the ongoing development of SpikeVet™ as a safe and effective veterinary SARS-CoV-2 vaccine.

Breaking the Barrier: SARS-CoV-2 Infections in Wild and Companion Animals and Their Implications for Public Health

The emergence of the novel coronavirus SARS-CoV-2 has led to significant interest in its potential transmission between animals and humans, especially pets. This review article summarises the literature on coronavirus infections in domestic animals, emphasising epidemiology, transmission dynamics, clinical manifestations, and public health implications. This article highlights current understandings of the relationship between infections in companion animals and humans, identifies research gaps, and suggests directions for future research. Cases of disease in cats, dogs, and other domestic animals, often occurring through close contact with infected owners, are reviewed, raising concerns about possible zoonotic and reverse zoonotic transmission. Precautions and recommendations for pet owners and healthcare workers are also discussed. The scientific evidence presented in the article highlights the need for a One Health approach that considers the health of people, animals, and the environment to combat future pandemics.

Transmission of severe acute respiratory syndrome coronavirus 2 from humans to animals: is there a risk of novel reservoirs?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a zoonotic virus able to infect humans and multiple nonhuman animal species. Most natural infections in companion, captive zoo, livestock, and wildlife species have been related to a reverse transmission, raising concern about potential generation of animal reservoirs due to human-animal interactions. To date, American mink and white-tailed deer are the only species that led to extensive intraspecies transmission of SARS-CoV-2 after reverse zoonosis, leading to an efficient spread of the virus and subsequent animal-to-human transmission. Viral host adaptations increase the probability of new SARS-CoV-2 variants' emergence that could cause a major global health impact. Therefore, applying the One Health approach is crucial to prevent and overcome future threats for human, animal, and environmental fields.

Ability of SpikoGen®, an Advax-CpG adjuvanted recombinant spike protein vaccine, to induce cross-neutralising antibodies against SARS-CoV-2 variants

SpikoGen® vaccine is a subunit COVID-19 vaccine expressed in insect cells comprising recombinant spike protein extracellular domain formulated with Advax-CpG55.2™ adjuvant. A Phase 2 trial was conducted in 400 adult participants randomised 3:1 to receive two intramuscular doses of SpikoGen® vaccine or saline placebo 3 weeks apart. Some Phase 2 trial participants later enrolled in a separate booster study and received a third dose of SpikoGen® vaccine. This stored serum was used to assess the ability of SpikoGen® vaccine to induce cross-neutralising antibodies against SARS-CoV-2 variants of concern. Sera taken at baseline and 2 weeks after the second vaccine dose from baseline seronegative Phase 2 subjects was evaluated using a panel of spike pseudotype lentivirus neutralisation assays for the ability to cross-neutralise a wide range of SARS-CoV-2 variants, including Omicron BA.1, BA.2 and BA.4/5. Stored samples of subjects who participated in both the 2-dose Phase 2 trial and a third dose booster trial 6 months later were also analysed for changes in cross-neutralising antibodies over time and dose. Two weeks after the second dose, sera broadly cross-neutralised most variants of concern, albeit with titres against Omicron variants being ~10-fold lower. While Omicron titres fell to low levels 6 months after the second vaccine dose in most subjects, they showed a ~20-fold rise after the third dose booster, after which there was only a ~2-3-fold difference in neutralisation of Omicron and the ancestral strains. Despite being based on the ancestral Wuhan sequence, after two doses, SpikoGen® vaccine induced broadly cross-neutralising serum antibodies. Titres then reduced over time but were rapidly restored by a third dose booster. This resulted in high neutralisation including against the Omicron variants. This data supports ongoing use of SpikoGen® vaccine for protection against recent SARS-CoV-2 Omicron variants.

Evaluation of a SARS-CoV-2 spike protein ectodomain subunit vaccine with a squalene emulsion adjuvant in rodents and rhesus macaques

COVID-19 vaccines have played an important role in reducing the impact of the current pandemic. Previously, we developed NARUVAX-C19 vaccine based on a recombinant Wuhan spike protein extracellular domain expressed in insect cells and formulated with a squalene emulsion adjuvant (Sepivac SWE™). The current study assessed the immunogenicity, efficacy, and safety of NARUVAX-C19 vaccine in rhesus macaques and hamsters. Macaques immunized intramuscularly with two doses of NARUVAX-C19 vaccine showed no adverse effects and demonstrated cellular immunity as assessed by T cell IFN-γ responses against spike protein, in addition to inducing a humoral response. Serum from immunized animals neutralized the homologous wild-type SARS-CoV-2 virus as well as the Alpha and Delta variants. In hamsters, immunization with NARUVAX-C19 vaccine protected against a heterologous challenge with the Delta virus, as reflected by reduced lung and nasal viral loads and lung pathology in immunized animals. Nevertheless, some NARUVAX-C19 vaccinated animals were still shown to transmit infection to naïve sentinel animals. Overall, NARUVAX-C19 vaccine induced broadly cross-neutralizing antibody and T cell IFN-γ responses in rhesus macaques and provided heterologous protection of hamsters against infection by the Delta virus variant. This data supports the utility of squalene emulsion-based adjuvanted recombinant vaccine in protection against SARS-CoV-2 and supports their continued clinical development.

An intranasal vaccine comprising SARS-CoV-2 spike receptor-binding domain protein entrapped in mannose-conjugated chitosan nanoparticle provides protection in hamsters

We developed a novel intranasal SARS-CoV-2 subunit vaccine called NARUVAX-C19/Nano based on the spike protein receptor-binding domain (RBD) entrapped in mannose-conjugated chitosan nanoparticles (NP). A toll-like receptor 9 agonist, CpG55.2, was also added as an adjuvant to see if this would potentiate the cellular immune response to the NP vaccine. The NP vaccine was assessed for immunogenicity, protective efficacy, and ability to prevent virus transmission from vaccinated animals to naive cage-mates. The results were compared with a RBD protein vaccine mixed with alum adjuvant and administered intramuscularly. BALB/c mice vaccinated twice intranasally with the NP vaccines exhibited secretory IgA and a pronounced Th1-cell response, not seen with the intramuscular alum-adjuvanted RBD vaccine. NP vaccines protected Syrian hamsters against a wild-type SARS-CoV-2 infection challenge as indicated by significant reductions in weight loss, lung viral load and lung pathology. However, despite significantly reduced viral load in the nasal turbinates and oropharyngeal swabs from NP-vaccinated hamsters, virus transmission was not prevented to naïve cage-mates. In conclusion, intranasal RBD-based NP formulations induced mucosal and Th1-cell mediated immune responses in mice and protected Syrian hamsters against SARS-CoV-2 infection but not against viral transmission.

Cytokine response and damages in the lungs of aging Syrian hamsters on a high-fat diet infected with the SARS-CoV-2 virus

Hypertriglyceridemia, obesity, and aging are among the key risk factors for severe COVID-19 with acute respiratory distress syndrome (ARDS). One of the main prognostic biomarkers of ARDS is the level of cytokines IL-6 and TNF-α in the blood. In our study, we modeled hyperglyceridemia and hypercholesterolemia on 18-month-old Syrian hamsters (Mesocricetus auratus). By 18 months, the animals showed such markers of aging as weight stabilization with a tendency to reduce it, polycystic liver disease, decreased motor activity, and foci of alopecia. The high-fat diet caused an increase in triglycerides and cholesterol, as well as fatty changes in the liver. On the third day after infection with the SARS-CoV-2 virus, animals showed a decrease in weight in the groups with a high-fat diet. In the lungs of males on both diets, there was an increase in the concentration of IFN-α, as well as IL-6 in both males and females, regardless of the type of diet. At the same time, the levels of TNF-α and IFN-γ did not change in infected animals. Morphological studies of the lungs of hamsters with SARS-CoV-2 showed the presence of a pathological process characteristic of ARDS. These included bronchointerstitial pneumonia and diffuse alveolar damages. These observations suggest that in aging hamsters, the immune response to pro-inflammatory cytokines may be delayed to a later period. Hypertriglyceridemia, age, and gender affect the severity of COVID-19. These results will help to understand the pathogenesis of COVID-19 associated with age, gender, and disorders of fat metabolism in humans.

In Silico Structure-Based Vaccine Design

Structure-based vaccine design (SBVD) is an important technique in computational vaccine design that uses structural information on a targeted protein to design novel vaccine candidates. This increasing ability to rapidly model structural information on proteins and antibodies has provided the scientific community with many new vaccine targets and novel opportunities for future vaccine discovery. This chapter provides a comprehensive overview of the status of in silico SBVD and discusses the current challenges and limitations. Key strategies in the field of SBVD are exemplified by a case study on design of COVID-19 vaccines targeting SARS-CoV-2 spike protein.

Vaccine research and development capacity in Central and West Asia: A path toward sustainable vaccine R&D programs

The ability to support a comprehensive vaccine research and development (R&D) portfolio from a health security perspective has taken on enhanced significance over the past 3 years whereby countries that had existing vaccine R&D infrastructure (G7, Russia and China) have been at the forefront of global efforts to combat COVID-19. Few countries outside of these key players have the infrastructure necessary to develop national vaccine programs, though this is beginning to change with investment across many low- and middle-income countries. These same opportunities exist for countries in Central and West Asia, and in this perspective, we highlight the existing infrastructure and expertise across seven countries (Armenia, Azerbaijan, Georgia, Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan) and propose opportunities for enhanced collaboration along with a bold proposal for establishing a new-build, regional vaccine translational research institute to facilitate the development of a robust, regional vaccine R&D environment to combat existing and future health challenges.

Enzyme linked oligonucleotide assay for the sensitive detection of SARS-CoV-2 variants

The exponential spread of COVID-19 has prompted the need to develop a simple and sensitive diagnostic tool. Aptamer-based detection assays like ELONA are promising since they are inexpensive and sensitive. Aptamers have advantages over antibodies in wide modification, small size, in vitro selection, and stability under stringent conditions, which aid in scalable and reliable detection. In this work, we used aptamers against SARS-CoV-2 RBD S protein to design a simple and sensitive ELONA detection tool. Screening CoV2-RBD-1C and CoV2-RBD-4C aptamers and optimizing assay conditions led to the development of a direct ELONA that can detect SARS-CoV-2 RBD S glycoprotein in buffer solution and 0.1 % human nasal fluid with a detection limit of 2.16 ng/mL and 1.02 ng/mL, respectively. We detected inactivated Alpha, Wuhan, and Delta variants of SARS-CoV-2 with the detection limit of 3.73, 5.72, and 6.02 TCID₅₀/mL, respectively. Using the two aptamers as capture and reporter elements, we designed a more sensitive sandwich assay to identify the three SARS-CoV-2 variants employed in this research. As predicted, a lower detection limit was obtained. Sandwich assay LOD was 2.31 TCID₅₀/mL for Alpha, 1.15 TCID₅₀/mL for Wuhan, and 2.96 TCID₅₀/mL for Delta. The sensitivity of sandwich ELONA was validated using Alpha and Wuhan variants spiked in 0.1% human nasal fluid sample condition and were detected in 1.41 and 1.79 TCID₅₀/mL LOD, respectively. SEM was used to visualize the presence of viral particles in the Delta variant sample. The effective detection of SARS-CoV-2 in this study confirms the potential of our aptamer-based technique as a screening tool.

Vaccination of cats with Sad23L-nCoV-S vaccine candidate against major variants of SARS-CoV-2

Cats are susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and risk transmitting viruses to naive cats or humans. Here, based on our novel adenovirus-vectored COVID-19 vaccine, the immunogenicity of Sad23L-nCoV-S vaccine was evaluated in cats by prime-boost vaccinations. Five cats were primed with a dose of 10⁸ plaque-forming units (PFUs) Sad23L-nCoV-S vaccine and then boosted with an equal dose of same vaccine at a 4-week interval. Cat serum neutralizing antibody (NAb) titers (the sample dilution at which 50% inhibitory concentration [IC₅₀]) were measured as IC₅₀ 15,849 to wild-type strain, IC₅₀ 6,591 to Alpha, IC₅₀ 2,315 to Beta, IC₅₀ 2,744 to Gamma, IC₅₀ 1,848 to Delta, and IC₅₀ 318 to Omicron variants of pseudotyped SARS-CoV-2 viruses at week 6 post-prime vaccination. All NAb levels to these five variants were ≥IC₅₀ 49 from vaccinated cats at week 10, while 48.8% to Delta and 100% to Omicron variants were <IC₅₀ 10 from human vaccinees at week 2 or 4 after receiving two injections of the inactivated SARS-CoV-2 vaccines. Robust T cell response of interferon (IFN)-γ to S peptides were detected in vaccinated cats. It was concluded that Sad23L-nCoV-S vaccine could be a promising vaccine candidate against SARS-CoV-2 infection in cats by prime or plus boost vaccinations.