Characterization of Immune Response Diversity in Rodents Vaccinated with a Vesicular Stomatitis Virus Vectored COVID-19 Vaccine

A surrogate BSL2-compliant infection model recapitulating key aspects of human Marburg virus disease

Marburg virus disease (MVD) is a severe infectious disease caused by the Marburg virus (MARV), posing a significant threat to humans. MARV needs to be operated under strict biosafety Level 4 (BSL-4) laboratory conditions. Therefore, accessible and practical animal models are urgently needed to advance prophylactic and therapeutic strategies for MARV. In this study, we constructed a recombinant vesicular stomatitis virus (VSV) expressing the Marburg virus glycoprotein (VSV-MARV/GP). Syrian hamsters infected with VSV-MARV/GP presented symptoms such as thrombocytopenia, lymphopenia, haemophilia, and multiorgan failure, developing a severe systemic disease akin to that observed in human MARV patients. Notably, the pathogenicity was found to be species-specific, age-related, sex-associated, and challenge route-dependent. Subsequently, the therapeutic efficacy of the MR191 monoclonal antibody was validated in this model. In summary, this alternative model is an effective tool for rapidly screening medical countermeasures against MARV GP in vivo under BSL-2 conditions.

A VSV-based oral rabies vaccine was sentineled by Peyer's patches and induced a timely and durable immune response

The global eradication of canine-mediated human rabies remains an ongoing public health priority. While conventional oral rabies vaccines (ORVs) have demonstrated partial success in interrupting zoonotic transmission, current formulations necessitate improvements in both immunogenic profiles and mechanistic clarity. Herein, we present a recombinant vesicular stomatitis virus (VSV)-vectored vaccine candidate (rVSVΔG-ERA-G) engineered to express the glycoprotein of the rabies virus (RABV) ERA strain, substituting the native VSV glycoprotein. Preclinical evaluation across multiple mammalian species (Mus musculus, Canis lupus familiaris, Felis catus, Vulpes lagopus, and Nyctereutes procyonoides) revealed rapid seroconversion and sustained neutralizing antibody responses. Challenge experiments demonstrated 100% survival efficacy in pre-exposure prophylaxis models, with partial protection observed in post-exposure scenarios. Safety assessments confirmed significant attenuation of neurotropism and absence of horizontal transmission or environmental shedding. Furthermore, evidence showed that rVSVΔG-ERA-G is recognized by Peyer's patches (PPs), where a cascade activation of immune cells occurred. From another perspective, the absence of functional microfold cells in PPs hampered the initiation and progression of immune responses. This proof-of-concept study establishes rVSVΔG-ERA-G as an ORV candidate with enhanced biosafety and cross-species immunogenicity. The elucidation of M cell-dependent mucosal priming mechanisms provides a rational framework for optimizing the targeted delivery of ORVs.

Emerging and reemerging infectious diseases: global trends and new strategies for their prevention and control

To adequately prepare for potential hazards caused by emerging and reemerging infectious diseases, the WHO has issued a list of high-priority pathogens that are likely to cause future outbreaks and for which research and development (R&D) efforts are dedicated, known as paramount R&D blueprints. Within R&D efforts, the goal is to obtain effective prophylactic and therapeutic approaches, which depends on a comprehensive knowledge of the etiology, epidemiology, and pathogenesis of these diseases. In this process, the accessibility of animal models is a priority bottleneck because it plays a key role in bridging the gap between in-depth understanding and control efforts for infectious diseases. Here, we reviewed preclinical animal models for high priority disease in terms of their ability to simulate human infections, including both natural susceptibility models, artificially engineered models, and surrogate models. In addition, we have thoroughly reviewed the current landscape of vaccines, antibodies, and small molecule drugs, particularly hopeful candidates in the advanced stages of these infectious diseases. More importantly, focusing on global trends and novel technologies, several aspects of the prevention and control of infectious disease were discussed in detail, including but not limited to gaps in currently available animal models and medical responses, better immune correlates of protection established in animal models and humans, further understanding of disease mechanisms, and the role of artificial intelligence in guiding or supplementing the development of animal models, vaccines, and drugs. Overall, this review described pioneering approaches and sophisticated techniques involved in the study of the epidemiology, pathogenesis, prevention, and clinical theatment of WHO high-priority pathogens and proposed potential directions. Technological advances in these aspects would consolidate the line of defense, thus ensuring a timely response to WHO high priority pathogens.

Establishment and application of a surrogate model for human Ebola virus disease in BSL-2 laboratory

The Ebola virus (EBOV) is a member of the Orthoebolavirus genus, Filoviridae family, which causes severe hemorrhagic diseases in humans and non-human primates (NHPs), with a case fatality rate of up to 90%. The development of countermeasures against EBOV has been hindered by the lack of ideal animal models, as EBOV requires handling in biosafety level (BSL)-4 facilities. Therefore, accessible and convenient animal models are urgently needed to promote prophylactic and therapeutic approaches against EBOV. In this study, a recombinant vesicular stomatitis virus expressing Ebola virus glycoprotein (VSV-EBOV/GP) was constructed and applied as a surrogate virus, establishing a lethal infection in hamsters. Following infection with VSV-EBOV/GP, 3-week-old female Syrian hamsters exhibited disease signs such as weight loss, multi-organ failure, severe uveitis, high viral loads, and developed severe systemic diseases similar to those observed in human EBOV patients. All animals succumbed at 2-3 days post-infection (dpi). Histopathological changes indicated that VSV-EBOV/GP targeted liver cells, suggesting that the tissue tropism of VSV-EBOV/GP was comparable to wild-type EBOV (WT EBOV). Notably, the pathogenicity of the VSV-EBOV/GP was found to be species-specific, age-related, gender-associated, and challenge route-dependent. Subsequently, equine anti-EBOV immunoglobulins and a subunit vaccine were validated using this model. Overall, this surrogate model represents a safe, effective, and economical tool for rapid preclinical evaluation of medical countermeasures against EBOV under BSL-2 conditions, which would accelerate technological advances and breakthroughs in confronting Ebola virus disease.

Oral delivery of a chitosan adjuvanted COVID-19 vaccine provides long-lasting and broad-spectrum protection against SARS-CoV-2 variants of concern in golden hamsters

Coronavirus disease 2019 (COVID-19) seriously threatens public health safety and the global economy, which warrant effective prophylactic and therapeutic approaches. Currently, vaccination and establishment of immunity have significantly reduced the severity and mortality of COVID-19. However, in regard to COVID-19 vaccines, the broad-spectrum protective efficacy against SARS-CoV-2 variants and the blocking of virus transmission need to be further improved. In this study, an optimum oral COVID-19 vaccine candidate, rVSVΔG-Sdelta, was selected from a panel of vesicular stomatitis virus (VSV)-based constructs bearing spike proteins from different SARS-CoV-2 strains. After chitosan modification, rVSVΔG-Sdelta induced both local and peripheral antibody response, particularly, broad-spectrum and long-lasting neutralizing antibodies against SARS-CoV-2 persisted for 1 year. Cross-protection against SARS-CoV-2 WT, Beta, Delta, BA.1, and BA.2 strains was achieved in golden hamsters, which presented as significantly reduced viral replication in the respiratory tract and alleviated pulmonary pathology post SARS-CoV-2 challenge. Overall, this study provides a convenient, oral-delivered, and effective oral mucosal vaccine against COVID-19, which would supplement pools and facilitate the distribution of COVID-19 vaccines.

Nanobodies with cross-neutralizing activity provide prominent therapeutic efficacy in mild and severe COVID-19 rodent models

The weakened protective efficacy of COVID-19 vaccines and antibodies caused by SARS-CoV-2 variants presents a global health emergency, which underscores the urgent need for universal therapeutic antibody intervention for clinical patients. Here, we screened three alpacas-derived nanobodies (Nbs) with neutralizing activity from twenty RBD-specific Nbs. The three Nbs were fused with the Fc domain of human IgG, namely aVHH-11-Fc, aVHH-13-Fc and aVHH-14-Fc, which could specifically bind RBD protein and competitively inhibit the binding of ACE2 receptor to RBD. They effectively neutralized SARS-CoV-2 pseudoviruses D614G, Alpha, Beta, Gamma, Delta, and Omicron sub-lineages BA.1, BA.2, BA.4, and BA.5 and authentic SARS-CoV-2 prototype, Delta, and Omicron BA.1, BA.2 strains. In mice-adapted COVID-19 severe model, intranasal administration of aVHH-11-Fc, aVHH-13-Fc and aVHH-14-Fc effectively protected mice from lethal challenges and reduced viral loads in both the upper and lower respiratory tracts. In the COVID-19 mild model, aVHH-13-Fc, which represents the optimal neutralizing activity among the above three Nbs, effectively protected hamsters from the challenge of SARS-CoV-2 prototype, Delta, Omicron BA.1 and BA.2 by significantly reducing viral replication and pathological alterations in the lungs. In structural modeling of aVHH-13 and RBD, aVHH-13 binds to the receptor-binding motif region of RBD and interacts with some highly conserved epitopes. Taken together, our study illustrated that alpaca-derived Nbs offered a therapeutic countermeasure against SARS-CoV-2, including those Delta and Omicron variants which have evolved into global pandemic strains.

Viral vectored vaccines: design, development, preventive and therapeutic applications in human diseases

Human diseases, particularly infectious diseases and cancers, pose unprecedented challenges to public health security and the global economy. The development and distribution of novel prophylactic and therapeutic vaccines are the prioritized countermeasures of human disease. Among all vaccine platforms, viral vector vaccines offer distinguished advantages and represent prominent choices for pathogens that have hampered control efforts based on conventional vaccine approaches. Currently, viral vector vaccines remain one of the best strategies for induction of robust humoral and cellular immunity against human diseases. Numerous viruses of different families and origins, including vesicular stomatitis virus, rabies virus, parainfluenza virus, measles virus, Newcastle disease virus, influenza virus, adenovirus and poxvirus, are deemed to be prominent viral vectors that differ in structural characteristics, design strategy, antigen presentation capability, immunogenicity and protective efficacy. This review summarized the overall profile of the design strategies, progress in advance and steps taken to address barriers to the deployment of these viral vector vaccines, simultaneously highlighting their potential for mucosal delivery, therapeutic application in cancer as well as other key aspects concerning the rational application of these viral vector vaccines. Appropriate and accurate technological advances in viral vector vaccines would consolidate their position as a leading approach to accelerate breakthroughs in novel vaccines and facilitate a rapid response to public health emergencies.

Characterization of a Vesicular Stomatitis Virus-Vectored Recombinant Virus Bearing Spike Protein of SARS-CoV-2 Delta Variant

The frequent emergence of SARS-CoV-2 variants thwarts the prophylactic and therapeutic countermeasures confronting COVID-19. Among them, the Delta variant attracts widespread attention due to its high pathogenicity and fatality rate compared with other variants. However, with the emergence of new variants, studies on Delta variants have been gradually weakened and ignored. In this study, a replication-competent recombinant virus carrying the S protein of the SARS-CoV-2 Delta variant was established based on the vesicular stomatitis virus (VSV), which presented a safe alternative model for studying the Delta variant. The recombinant virus showed a replication advantage in Vero E6 cells, and the viral titers reach 10^7.3 TCID₅₀/mL at 36 h post-inoculation. In the VSV-vectored recombinant platform, the spike proteins of the Delta variant mediated higher fusion activity and syncytium formation than the wild-type strain. Notably, the recombinant virus was avirulent in BALB/c mice, Syrian hamsters, 3-day ICR suckling mice, and IFNAR/GR^-/- mice. It induced protective neutralizing antibodies in rodents, and protected the Syrian hamsters against the SARS-CoV-2 Delta variant infection. Meanwhile, the eGFP reporter of recombinant virus enabled the visual assay of neutralizing antibodies. Therefore, the recombinant virus could be a safe and convenient surrogate tool for authentic SARS-CoV-2. This efficient and reliable model has significant potential for research on viral-host interactions, epidemiological investigation of serum-neutralizing antibodies, and vaccine development.

Comparative study of subcutaneous, intramuscular, and oral administration of bovine pathogenic Escherichia coli bacterial ghost vaccine in mice

Escherichia coli is one of the most common bacterial pathogens in cattle. Prophylactic vaccines are considered promising strategies with the potential to reduce the incidence of colibacillosis. Some studies suggested that bacterial ghosts may serve as a novel approach for preventing bacterial infections. However, the roles of administration route on vaccine immunogenicity and efficacy have not been investigated. In this study, the efficacy of vaccination via different immune routes in generating humoral and cellular immune response was compared through subcutaneous (SC), intramuscular (IM), and oral (O) administration in female BALB/c mice with bacterial ghosts prepared using wild type Escherichia coli isolates CE9, while phosphate buffer saline (PBS) and inactivated vaccines containing aluminum adjuvants (Killed) were used as control. Our results showed that the plasmid pBV220-E-aa-SNA containing E. coli was efficiently cleaved at 42°C with 94.8% positive ratio as assessed by colony counts. Transmission electron microscopy (TEM) confirmed bacteria retained intact surface structure while devoid of cytoplasmic component. We found that total IgG titers in killed, IM and SC groups showed significant increase on 7, 14, 21 and 28 days post-immunization. The IgA level of the IM group was higher than that of all other groups on the 28th day. Meanwhile, four experimental groups showed a significant difference in IgA levels compared with PBS control. In the IM group, an increase in the relative percentages of CD3+CD4+ T cells was accompanied by an increase in the relative percentages of splenic CD3+CD8+ T cells. In comparison with the inactivated vaccine, intramuscular CE9 ghosts immunization elicited higher levels of IL-1β, IL-2, IL-6 and IL-12. Subcutaneous and intramuscular immunizations were significantly associated with improved survival in comparison with oral route, traditional vaccine and the control. Pathologic assessment revealed that less severe tissue damage and inflammation were found in lung, kidney, and intestine of IM group compared with other groups. The results above demonstrate that immunization of Escherichia coli CE9 ghosts via intramuscular injection elicits a more robust antigen-specific immune response in mice to prevent the Escherichia coli infection.

GEM-PA-Based Subunit Vaccines of Crimean Congo Hemor-Rhagic Fever Induces Systemic Immune Responses in Mice

The Crimean Congo Hemorrhagic Fever Virus (CCHFV) is a tick-borne bunyavirus of the Narovirus genus, which is the causative agent of Crimean Congo Hemorrhagic Fever (CCHF). CCHF is endemic in Africa, the Middle East, Eastern Europe and Asia, with a high case-fatality rate of up to 50% in humans. Currently, there are no approved vaccines or effective therapies available for CCHF. The GEM-PA is a safe, versatile and effective carrier system, which offers a cost-efficient, high-throughput platform for recovery and purification of subunit proteins for vaccines. In the present study, based on a GEM-PA surface display system, a GEM-PA based vaccine expressing three subunit vaccine candidates (G-GP, including G-eG_N, G-eG_C and G-NAb) of CCHFV was developed, displaying the ectodomains of the structural glycoproteins eG_N, eG_C and NAb, respectively. According to the immunological assays including indirect-ELISA, a micro-neutralization test of pseudo-virus and ELISpot, 5 μg GPBLP₃ combined with Montanide ISA 201VG plus Poly (I:C) adjuvant (A-G-GP-5 μg) elicited GP-specific humoral and cellular immunity in BALB/c mice after three vaccinations via subcutaneous injection (s.c.). The consistent data between IgG subtype and cytokine detection, ELISpot and cytokine detection indicated balanced Th1 and Th2 responses, of which G-eG_N vaccines could elicit a stronger T-cell response post-vaccination, respectively. Moreover, all three vaccine candidates elicited high TNF-α, IL-6, and IL-10 cytokine levels in the supernatant of stimulated splenocytes in vitro. However, the neutralizing antibody (nAb) was only detected in A-G-eG_C and A-G-eG_C vaccination groups with the highest neutralizing titer of 128, suggesting that G-eG_C could elicit a stronger humoral immune response. In conclusion, the GEM-PA surface display system could provide an efficient and convenient purification method for CCHFV subunit antigens, and the G-GP subunit vaccine candidates will be promising against CCHFV infections with excellent immunogenicity.