Immunogenicity and protective efficacy of a recombinant protein subunit vaccine and an inactivated vaccine against SARS-CoV-2 variants in non-human primates.

Emerging SARS-CoV-2 variants and the gradually decreasing neutralizing antibodies over time post vaccination have led to an increase in incidents of breakthrough infection across the world. To investigate the potential protective effect of the recombinant protein subunit COVID-19 vaccine targeting receptor-binding domain (RBD) (PS-RBD) and whole inactivated virus particle vaccine (IV) against the variant strains, in this study, rhesus macaques were immunized with PS-RBD or IV vaccine, followed by a Beta variant (B.1.351) challenge. Although neutralizing activity against the Beta variant was reduced compared with that against the prototype, the decreased viral load in both upper and lower respiratory tracts, milder pathological changes, and downregulated inflammatory cytokine levels in lung tissues after challenge demonstrated that PS-RBD and IV still provided effective protection against the Beta variant in the macaque model. Furthermore, PS-RBD-induced macaque sera possessed general binding and neutralizing activity to Alpha, Beta, Delta, and Omicron variants in our study, though the neutralizing antibody (NAb) titers declined by varying degrees, demonstrating potential protection of PS-RBD against current circulating variants of concern (VOCs). Interestingly, although the IV vaccine-induced extremely low neutralizing antibody titers against the Beta variant, it still showed reduction for viral load and significantly alleviated pathological change. Other correlates of vaccine-induced protection (CoP) like antibody-dependent cellular cytotoxicity (ADCC) and immune memory were both confirmed to be existing in IV vaccinated group and possibly be involved in the protective mechanism.

Human IgM and IgG Responses to an Inactivated SARS-CoV-2 Vaccine.

OBJECTIVE: The ongoing COVID-19 pandemic warrants accelerated efforts to test vaccine candidates. To explore the influencing factors on vaccine-induced effects, antibody responses to an inactivated SARS-CoV-2 vaccine in healthy individuals who were not previously infected by COVID-19 were assessed. METHODS: All subjects aged 18-60 years who did not have SARS-CoV-2 infection at the time of screening from June 19, 2021, to July 02, 2021, were approached for inclusion. All participants received two doses of inactivated SARS-CoV-2 vaccine. Serum IgM and IgG antibodies were detected using a commercial kit after the second dose of vaccination. A positive result was defined as 10 AU/mL or more and a negative result as less than 10 AU/mL. This retrospective study included 97 infection-naïve individuals (mean age 35.6 years; 37.1% male, 62.9% female). RESULTS: The seropositive rates of IgM and IgG antibody responses elicited after the second dose of inactivated SARS-CoV-2 vaccine were 3.1% and 74.2%, respectively. IgG antibody levels were significantly higher than IgM levels (P<0.0001). Sex had no effect on IgM and IgG antibody response after the second dose. The mean anti-IgG level in older persons (⩾42 years) was significantly lower than that of younger recipients. There was a significantly lower antibody level at > 42 days compared to that at 0-20 days (P<0.05) and 21-31 days (P<0.05) after the second dose. CONCLUSION: IgG antibody response could be induced by inactivated SARS-CoV-2 vaccine in healthy individuals (>18 years), which can be influenced by age and detection time after the second dose of vaccination.

Effect of vaccines against pancreas disease in farmed Atlantic salmon.

Pancreas disease (PD) caused by salmonid alphavirus (SAV) continues to negatively impact salmon farming. To assess the effect on growth and mortality of three vaccines against PD, two controlled field designs were employed: one controlled field study with individual marked fish (PIT tag) assessing three PD vaccines and three controls groups, and a second controlled field study with group marked fish (Maxilla) comparing two PD vaccines against controls. In addition, a descriptive study using whole cages compared fish immunized with two different PD vaccines against controls. The target populations experienced a natural PD outbreak where both SAV 2 and SAV 3 were identified. Only one of the PD vaccines provided statistically significant improvements in harvest weight of 0.43 kg (CI: 0.29-0.57) and 0.51 kg (CI: 0.36-0.65) compared with the control in the PIT tag and the Maxilla study, respectively. In the latter, a significant reduction in mortality of 1.31 (CI:0.8-1.8) per cent points was registered for the same vaccine compared with controls. These results aligned with the growth and PD-specific mortality registered in the descriptive Cage study. The data in this study show a difference in the efficacy of PD vaccines in farmed Atlantic salmon.

Single dose of multi-clade virus-like particle vaccine protects chickens against clade 2.3.2.1 and clade 2.3.4.4 highly pathogenic avian influenza viruses.

Virus-like particles (VLPs) are recognized as an alternative vaccine platform that provide effective protection against various highly pathogenic avian influenza viruses (HPAIVs). Here, we developed multi-clade VLPs expressing two HAs (a chimera of clade 2.3.2.1c and clade 2.3.4.4c HA) within a single vector. We then compared its protective efficacy with that of a monovalent VLP and evaluated its potency against each homologous strain. Chickens vaccinated with the multi-clade VLP shed less virus and were better protected against challenge than birds receiving monovalent vaccines. Single vaccination with a multi-clade VLP resulted in 100% survival, with no clinical symptoms and high levels of pre-challenge protective immunity (7.6-8.5 log2). Moreover, the multi-clade VLP showed high productivity (128-256 HAU) both in the laboratory and on a large scale, making it cheaper than whole inactivated vaccines produced in eggs. However, the PD50 (protective dose 50%) of the multi-clade VLP against clades 2.3.2.1c and 2.3.4.4c was < 50 PD50 (28 and 42 PD50, respectively), and effective antibody response was maintained for 2-3 months. This multi-clade VLP protects against both clades of HPAI viruses and can be produced in high amounts at low cost. Thus, the vaccine has potential as a pandemic preparedness vaccine.

Proteomic analysis of chicken bone marrow-derived dendritic cells in response to an inactivated IBV + NDV poultry vaccine.

Inactivated poultry vaccines are subject to routine potency testing for batch release, requiring large numbers of animals. The replacement of in vivo tests for cell-based alternatives can be facilitated by the identification of biomarkers for vaccine-induced immune responses. In this study, chicken bone marrow-derived dendritic cells were stimulated with an inactivated vaccine for infectious bronchitis virus and Newcastle disease virus, as well as inactivated infectious bronchitis virus only, and lipopolysaccharides as positive control, or left unstimulated for comparison with the stimulated samples. Next, the cells were lysed and subjected to proteomic analysis. Stimulation with the vaccine resulted in 66 differentially expressed proteins associated with mRNA translation, immune responses, lipid metabolism and the proteasome. For the eight most significantly upregulated proteins, mRNA expression levels were assessed. Markers that showed increased expression at both mRNA and protein levels included PLIN2 and PSMB1. Stimulation with infectious bronchitis virus only resulted in 25 differentially expressed proteins, which were mostly proteins containing Src homology 2 domains. Stimulation with lipopolysaccharides resulted in 118 differentially expressed proteins associated with dendritic cell maturation and antimicrobial activity. This study provides leads to a better understanding of the activation of dendritic cells by an inactivated poultry vaccine, and identified PLIN2 and PSMB1 as potential biomarkers for cell-based potency testing.

Humoral immune response to circulating SARS-CoV-2 variants elicited by inactivated and RBD-subunit vaccines.

SARS-CoV-2 variants could induce immune escape by mutations on the receptor-binding domain (RBD) and N-terminal domain (NTD). Here we report the humoral immune response to circulating SARS-CoV-2 variants, such as 501Y.V2 (B.1.351), of the plasma and neutralizing antibodies (NAbs) elicited by CoronaVac (inactivated vaccine), ZF2001 (RBD-subunit vaccine) and natural infection. Among 86 potent NAbs identified by high-throughput single-cell VDJ sequencing of peripheral blood mononuclear cells from vaccinees and convalescents, near half anti-RBD NAbs showed major neutralization reductions against the K417N/E484K/N501Y mutation combination, with E484K being the dominant cause. VH3-53/VH3-66 recurrent antibodies respond differently to RBD variants, and K417N compromises the majority of neutralizing activity through reduced polar contacts with complementarity determining regions. In contrast, the 242-244 deletion (242-244Δ) would abolish most neutralization activity of anti-NTD NAbs by interrupting the conformation of NTD antigenic supersite, indicating a much less diversity of anti-NTD NAbs than anti-RBD NAbs. Plasma of convalescents and CoronaVac vaccinees displayed comparable neutralization reductions against pseudo- and authentic 501Y.V2 variants, mainly caused by E484K/N501Y and 242-244Δ, with the effects being additive. Importantly, RBD-subunit vaccinees exhibit markedly higher tolerance to 501Y.V2 than convalescents, since the elicited anti-RBD NAbs display a high diversity and are unaffected by NTD mutations. Moreover, an extended gap between the third and second doses of ZF2001 leads to better neutralizing activity and tolerance to 501Y.V2 than the standard three-dose administration. Together, these results suggest that the deployment of RBD-vaccines, through a third-dose boost, may be ideal for combating SARS-CoV-2 variants when necessary, especially for those carrying mutations that disrupt the NTD supersite.

Enhancing immune responses to inactivated foot-and-mouth virus vaccine by a polysaccharide adjuvant of aqueous extracts from Artemisia rupestris L.

BACKGROUND: New-generation adjuvants for foot-and-mouth disease virus (FMDV) vaccines can improve the efficacy of existing vaccines. Chinese medicinal herb polysaccharide possesses better promoting effects. OBJECTIVES: In this study, the aqueous extract from Artemisia rupestris L. (AEAR), an immunoregulatory crude polysaccharide, was utilized as the adjuvant of inactivated FMDV vaccine to explore their immune regulation roles. METHODS: The mice in each group were subcutaneously injected with different vaccine formulations containing inactivated FMDV antigen adjuvanted with three doses (low, medium, and high) of AEAR or AEAR with ISA-206 adjuvant for 2 times respectively in 1 and 14 days. The variations of antibody level, lymphocyte count, and cytokine secretion in 14 to 42 days after first vaccination were monitored. Then cytotoxic T lymphocyte (CTL) response and antibody duration were measured after the second vaccination. RESULTS: AEAR significantly induced FMDV-specific antibody titers and lymphocyte activation. AEAR at a medium dose stimulated Th1/Th2-type response through interleukin-4 and interferon-γ secreted by CD4⁺ T cells. Effective T lymphocyte counts were significantly elevated by AEAR. Importantly, the efficient CTL response was remarkably provoked by AEAR. Furthermore, AEAR at a low dose and ISA-206 adjuvant also synergistically promoted immune responses more significantly in immunized mice than those injected with only ISA-206 adjuvant and the stable antibody duration without body weight loss was 6 months. CONCLUSIONS: These findings suggested that AEAR had potential utility as a polysaccharide adjuvant for FMDV vaccines.

Efficacy of live attenuated and inactivated influenza vaccines among children in rural India: A 2-year, randomized, triple-blind, placebo-controlled trial.

BACKGROUND: Influenza is a cause of febrile acute respiratory infection (FARI) in India; however, few influenza vaccine trials have been conducted in India. We assessed absolute and relative efficacy of live attenuated influenza vaccine (LAIV) and inactivated influenza vaccine (IIV) among children aged 2 to 10 years in rural India through a randomized, triple-blind, placebo-controlled trial conducted over 2 years. METHODS AND FINDINGS: In June 2015, children were randomly allocated to LAIV, IIV, intranasal placebo, or inactivated polio vaccine (IPV) in a 2:2:1:1 ratio. In June 2016, vaccination was repeated per original allocation. Overall, 3,041 children received LAIV (n = 1,015), IIV (n = 1,010), nasal placebo (n = 507), or IPV (n = 509). Mean age of children was 6.5 years with 20% aged 9 to 10 years. Through weekly home visits, nasal and throat swabs were collected from children with FARI and tested for influenza virus by polymerase chain reaction. The primary outcome was laboratory-confirmed influenza-associated FARI; vaccine efficacy (VE) was calculated using modified intention-to-treat (mITT) analysis by Cox proportional hazards model (PH) for each year. In Year 1, VE was 40.0% (95% confidence interval (CI) 25.2 to 51.9) for LAIV and 59.0% (95% CI 47.8 to 67.9) for IIV compared with controls; relative efficacy of LAIV compared with IIV was -46.2% (95% CI -88.9 to -13.1). In Year 2, VE was 51.9% (95% CI 42.0 to 60.1) for LAIV and 49.9% (95% CI 39.2 to 58.7) for IIV; relative efficacy of LAIV compared with IIV was 4.2% (95% CI -19.9 to 23.5). No serious adverse vaccine-attributable events were reported. Study limitations include differing dosage requirements for children between nasal and injectable vaccines (single dose of LAIV versus 2 doses of IIV) in Year 1 and the fact that immunogenicity studies were not conducted. CONCLUSIONS: In this study, we found that LAIV and IIV vaccines were safe and moderately efficacious against influenza virus infection among Indian children. TRIAL REGISTRATION: Clinical Trials Registry of India CTRI/2015/06/005902.

Alginate-chitosan microcapsules improve vaccine potential of gamma-irradiated Listeria monocytogenes against listeriosis in murine model.

Listeria monocytogenes is a cause of infectious food-borne disease in humans, characterized by neurological manifestations, abortion, and neonatal septicemia. It is intracellular bacterium, which limits the development of protective inactivated vacines. Adjuvants capable of stimulating cellular immune response are important tools for developing novel vaccines against intracellular bacteria. The aim of this study was to evaluate the vaccine potential of L. monocytogenes inactivated by gamma irradiation (KLM-γ) encapsulated in alginate microcapsules associated or not with chitosan against listeriosis in the murine model. At the fourth day after challenge there was a reduction in bacterial recovery in mice vaccinated with KLM-γ encapsulated with alginate or alginate-chitosan, with lower bacterial loads in the spleen (10 fold) and liver (100 fold) when compared to non-vaccinated mice. In vitro stimulation of splenocytes from mice vaccinated with alginate-chitosan-encapsulated KLM-γ resulted in lymphocyte proliferation, increase of proportion of memory CD4+ and CD8+ T cell and production of IL-10 and IFN-γ. Interestingly, the group vaccinated with alginate-chitosan-encapsulated KLM-γ had increased survival to lethal infection with lower L. monocytogenes-induced hepatic inflammation and necrosis. Therefore, KLM-γ encapsulation with alginate-chitosan proved to have potential for development of novel and safe inactivated vaccine formulations against listeriosis.

Efficacy of a formalin-inactivated Lactococcus garvieae vaccine in farmed grey mullet (Mugil cephalus).

Lactococcosis [Lactococcus garvieae (LG)] is one of the most prevalent bacterial diseases affecting grey mullet (Mugil cephalus) aquaculture. Therefore, the present research evaluated the efficacy of formalin-killed LG vaccine with an oil-based adjuvant in grey mullet under laboratory and field trials. The laboratory evaluation for LG vaccine and its cross-protection upon challenge in grey mullet found that single-dose immunization of formalin-killed LG with adjuvant resulted in 91.4% and 100% relative per cent survival (RPS) when challenged with homologous and heterologous strains. The levels of specific antibody titre and lysozyme activity increased significantly in the vaccinated group. Immune gene expression at 24 hr after challenge showed an increase in levels of pro-inflammatory and anti-inflammatory cytokines. A parallel field trial experiment was conducted to investigate the long-term effectiveness of the LG vaccine. Results demonstrated that at one month and three months post-immunization with heterologous strain, 100% RPS was recorded in the vaccinated group. The findings suggested that the formalin-inactivated LG vaccine strain (S3) protected grey mullet against LG infection for a period of three months.

Protective effects of ß-glucan as adjuvant combined inactivated Vibrio harveyi vaccine in pearl gentian grouper.

Vaccination is one of the strategies for preventing Vibrio harveyi infection in marine-cultured animals. In this study, we prepared a formalin-killed cells of V. harveyi ZJ0603 vaccine (FKC) combined with ß-glucan to immune pearl gentian grouper. The results indicated that the expression levels of IgM, TNF-α, MHC-Iα, IL-1ß and IL-16 significantly increased in the spleen of the vaccinated fish. Antibody titers, activities of lysozyme and superoxide dismutase were significantly prompted in blood of the vaccinated fish. After 35 d post-vaccination, all fish were challenged intraperitoneally by virulent V. harveyi, and the relative percentage of survival (RPS) of FKC+ß-glucan, FKC, ß-glucan and PBS were 68 ± 5.7%, 55 ± 8.5%, 42 ± 7.5% and 32 ± 6.9%, respectively. These results demonstrated that ß-glucan could be as a potential adjuvant of FKC and provide good protective effect against V. harveyi infection in the pearl gentian grouper culture.

Protection of layers and breeders against homologous or heterologous HPAIv by vaccines from Korean national antigen bank.

Korean government has selected and stocked five type antigens of two clades as Korean national antigen bank having high possibility of introduction to Korea. We aimed to evaluate the efficacy of the clade 2.3.2.1c and 2.3.4.4c H5Nx vaccines from the Korean avian influenza (AI) national antigen bank for emergency preparedness for their potency and protective efficacy against lethal homologous and heterologous viruses in layer and breeder chickens practically. The PD50 (dose of vaccine that protects 50% of chickens from viral challenge) of all vaccinated groups was >50, which was satisfied with minimum antigen requirement of OIE, and the PD50 levels of the two vaccines differed depending on strain and chicken breed. In homologous challenge, all vaccinated groups exhibited 100% survival with no clinical symptoms and high levels of pre-challenge protective immunity (7.2-8.5 log2), although they did not completely prevent virus shedding. On the other hand, against heterologous virus challenge, vaccinated animals exhibited 62.5-80% survival with lower antibody titers (2.3-3.4 log2) and a longer period of virus shedding (14 days post infection [dpi]). Our results suggest that the clade 2.3.2.1c and 2.3.4.4c H5Nx vaccines are good candidates for emergency vaccination of commercial chickens and support the idea that close genetic matching between vaccine and challenge virus provides the best protection.

Alternative methods to reduce the animal use in quality controls of inactivated BTV8 Bluetongue vaccines.

The acceptance of serology data instead of challenge for market release of new batches of commercial vaccine is under evaluation by regulatory agencies in order to reduce the use of animals and costs for manufacturers. In this study two vaccines for Bluetongue virus serotype 8 were submitted to quality controls required by the European Pharmacopoeia and tested on sheep in comparison with a commercial inactivated vaccine. Body temperature, antibody titres and viraemia of vaccinated and controls sheep were recorded. In addition IL4 and IFNγ in sera and supernatant derived from in vitro stimulation of blood cells were also quantified using two commercial ELISA kit. The outer-capsid protein VP2 contained in vaccine formulations was quantified using a home-made capture-ELISA. Results obtained indicates that in-lab evaluation of cell-mediated and humoral immune response are useful parameters to predict the efficacy of BTV inactivated vaccines avoiding the challenge phase required to release new batches of vaccines with proven clinical efficacy and safety. The correlation observed between serology data and VP2 protein concentration of final product could be useful in-process control to predict if a new vaccine batch of BTV must be discarded or released to the market.

Development of an Enterovirus 71 Vaccine Efficacy Test Using Human Scavenger Receptor B2 Transgenic Mice.

Enterovirus 71 (EV71) is a causative agent of hand-foot-mouth disease, and it sometimes causes severe neurological disease. Development of effective vaccines and animal models to evaluate vaccine candidates are needed. However, the animal models currently used for vaccine efficacy testing, monkeys and neonatal mice, have economic, ethical, and practical drawbacks. In addition, EV71 strains prepared for lethal challenge often develop decreased virulence during propagation in cell culture. To overcome these problems, we used a mouse model expressing human scavenger receptor B2 (hSCARB2) that showed lifelong susceptibility to EV71. We selected virulent EV71 strains belonging to the subgenogroups B4, B5, C1, C2, and C4 and propagated them using a culture method for EV71 without an apparent reduction in virulence. Here, we describe a novel EV71 vaccine efficacy test based on these hSCARB2 transgenic (Tg) mice and these virulent viruses. Adult Tg mice were immunized subcutaneously with formalin-inactivated EV71. The vaccine elicited sufficient levels of neutralizing antibodies in the immunized mice. The mice were subjected to lethal challenge with virulent viruses via intravenous injection. Survival, clinical signs, and body weight changes were observed for 2 weeks. Most immunized mice survived without clinical signs or histopathological lesions. The viral replication in immunized mice was much lower than that in nonimmunized mice. Mice immunized with the EV71 vaccine were only partially protected against lethal challenge with coxsackievirus A16. These results indicate that this new model is useful for in vivo EV71 vaccine efficacy testing.IMPORTANCE The development of new vaccines for EV71 relies on the availability of small animal models suitable for in vivo efficacy testing. Monkeys and neonatal mice have been used, but the use of these animals has several drawbacks, including high costs, limited susceptibility, and poor experimental reproducibility. In addition, the related ethical issues are considerable. The new efficacy test based on hSCARB2 Tg mice and virulent EV71 strains propagated in genetically modified cell lines presented here can overcome these disadvantages and is expected to accelerate the development of new EV71 vaccines.

Limited impact of influenza A virus vaccination of piglets in an enzootic infected sow herd.

Recent studies have questioned the effect of maternal derived antibodies (MDAs) to protect piglets against infection with influenza A virus (IAV). The lack of protection against IAV infections provided by MDAs has encouraged alternative vaccination strategies targeting young piglets in an attempt to stimulate an early antibody response. There is a lack of studies documenting the efficacy of piglet vaccination. In the present study, we monitored a group of vaccinated and non-vaccinated piglets in a Danish sow herd that initiated piglet vaccination with » dose of an inactivated swine influenza vaccine at the time of castration (day 3-4). A total of 160 piglets from 11 sows were included and either vaccinated with 0.5 mL inactivated swine influenza vaccine or sham-vaccinated. From week 0 until week 6, all included piglets were clinically examined and nasal swapped once per week and weighed at weeks 0, 3 and 6. Blood samples were collected from sows at week 0 and from piglets at week 3. Vaccination of piglets had limited effect on clinical signs, body weight, antibody development and viral shedding, within the first 6 weeks of life. At least 50% of all pigs of each treatment group tested positive for IAV at week 2, and very early onset of IAV shedding was observed. In total, 18 pigs were IAV positive in nasal swabs for more than one consecutive sampling time indicating prolonged shedding and 14 pigs were IAV positive with negative samplings in between indicating re-infection with the same IAV strain.

Changes of urine metabolite profiles are induced by inactivated influenza vaccine inoculations in mice.

The safety evaluation of vaccines is critical to avoid the development of side effects in humans. To increase the sensitivity of detection for toxicity tests, it is important to capture not only pathological changes but also physiological changes. 1H nuclear magnetic resonance (NMR) spectroscopy analysis of biofluids produces profiles that show characteristic responses to changes in physiological status. In this study, mouse urine metabolomics analysis with 1H NMR was performed using different influenza vaccines of varying toxicity to assess the usefulness of 1H NMR in evaluating vaccine toxicity. Two types of influenza vaccines were used as model vaccines: a toxicity reference vaccine (RE) and a hemagglutinin split vaccine. According to the blood biochemical analyses, the plasma alanine transaminase levels were increased in RE-treated mice. Changes in metabolite levels between mice administered different types of influenza vaccines were observed in the 1H NMR spectra of urine, and a tendency toward dosage-dependent responses for some spectra was observed. Hierarchical clustering analyses and principal component analyses showed that the changes in various urine metabolite levels allowed for the classification of different types of vaccines. Among them, two liver-derived metabolites were shown to largely contribute to the formation of the cluster. These results demonstrate the possibility that urine metabolomics analysis could provide information about vaccine-induced toxicity and physiological changes.

Nanoparticle-based vaccine development and evaluation against viral infections in pigs.

Virus infections possess persistent health challenges in swine industry leading to severe economic losses worldwide. The economic burden caused by virus infections such as Porcine Reproductive and Respiratory Syndrome Virus, Swine influenza virus, Porcine Epidemic Diarrhea Virus, Porcine Circovirus 2, Foot and Mouth Disease Virus and many others are associated with severe morbidity, mortality, loss of production, trade restrictions and investments in control and prevention practices. Pigs can also have a role in zoonotic transmission of some viral infections to humans. Inactivated and modified-live virus vaccines are available against porcine viral infections with variable efficacy under field conditions. Thus, improvements over existing vaccines are necessary to: (1) Increase the breadth of protection against evolving viral strains and subtypes; (2) Control of emerging and re-emerging viruses; (3) Eradicate viruses localized in different geographic areas; and (4) Differentiate infected from vaccinated animals to improve disease control programs. Nanoparticles (NPs) generated from virus-like particles, biodegradable and biocompatible polymers and liposomes offer many advantages as vaccine delivery platform due to their unique physicochemical properties. NPs help in efficient antigen internalization and processing by antigen presenting cells and activate them to elicit innate and adaptive immunity. Some of the NPs-based vaccines could be delivered through both parenteral and mucosal routes to trigger efficient mucosal and systemic immune responses and could be used to target specific immune cells such as mucosal microfold (M) cells and dendritic cells (DCs). In conclusion, NPs-based vaccines can serve as novel candidate vaccines against several porcine viral infections with the potential to enhance the broader protective efficacy under field conditions. This review highlights the recent developments in NPs-based vaccines against porcine viral pathogens and how the NPs-based vaccine delivery system induces innate and adaptive immune responses resulting in varied level of protective efficacy.

Evaluation of biofilm of Vibrio anguillarum for oral vaccination of Asian seabass, Lates calcarifer (BLOCH, 1790).

The present study evaluated the biofilm (BF) of Vibrio anguillarum for oral vaccination of Asian seabass, Lates calcarifer. An 80-day experiment was carried out in circular fiber-reinforced plastic (FRP) tanks using free cell (FC) and BF of Vibrio anguillarum with triplicate in each. Heat-inactivated FC and BF cells at 107, 1010 and 1013 CFU/g fish/d were fed to fish for 20 days, agglutination antibody titer estimated at each 10 days interval up to 60-day post vaccination. As compared to FC and control there was a significant increase in agglutinating antibody titer in the biofilm vaccinated fishes. Among the 3 doses, BF at 1010 cfu/g fish/d was considered the ideal dose for vaccination. Relative percentage survival (RPS) was higher in biofilm vaccinated fish (85.4%) compared to that with free cells (27.0%). The study demonstrated the better performance of V. anguillarum biofilm oral vaccine compared that with free cell vaccine in L. calcarifer. The study further supports better performance of biofilm vaccine model with one more bacterial pathogen in a high carnivore fish.

Efficacy of Two Licensed Avian Influenza H5 Vaccines Against Challenge with a 2015 U.S. H5N2 clade 2.3.4.4 Highly Pathogenic Avian Influenza Virus in Domestic Ducks.

Highly pathogenic avian influenza (HPAI) clade 2.3.4.4 viruses from the H5 goose/Guangdong lineage caused a major outbreak in poultry in the United States in 2015. Although the outbreak was controlled, vaccines were considered as an alternative control method, and new vaccines were approved and purchased by the U.S. Department of Agriculture National Veterinary Stockpile for emergency use. In this study, we evaluated the efficacy of two of these vaccines in protecting Pekin ducks (Anas platyrhynchos var. domestica) against challenge with a H5N2 HPAI poultry isolate. A recombinant alphavirus-based vaccine and an inactivated adjuvanted reverse genetics vaccine, both expressing the hemagglutinin gene of a U.S. H5 clade 2.3.4.4 isolate (A/Gyrfalcon/Washington/41088-6/2014 H5N8), were used to immunize the ducks. The vaccines were given either as single vaccination at 2 days of age or in a prime-boost strategy at 2 and 15 days of age. At 32 days of age, all ducks were challenged with A/turkey/Minnesota/12582/15 H5N2 HPAI virus clade 2.3.4.4. All ducks from the nonvaccinated challenge control group became infected and shed virus; one duck in this group presented mild ataxia, and a second duck died. No mortality or clinical signs were observed in vaccinated and challenged ducks, with the exception of one duck presenting with mild ataxia. Both vaccines, regardless of the vaccination strategy used, were immunogenic in ducks and reduced or prevented virus shedding after challenge. In conclusion, good protection against H5Nx infection was achieved in ducks vaccinated with the vaccines examined, which were homologous to the challenge virus, with prime-boost strategies conferring the best protection against infection.

Eficacia de dos vacunas con licencia contra influenza aviar H5 frente a un desafío con un virus de la influenza aviar altamente patógeno H5N2 en patos domésticos de los Estados Unidos del año 2015 y del clado 2015 2.3.4.4. Los virus de la influenza aviar altamente patógena (HPAI) 2.3.4.4 del linaje H5 ganso/Guangdong causaron un brote importante en la avicultura de los Estados Unidos en el año 2015. Aunque el brote fue controlado, las vacunas se consideraron un método de control alternativo y nuevas vacunas fueron aprobadas y adquiridas por la Reserva Nacional Veterinaria del Departamento de Agricultura de los Estados Unidos para uso en caso de emergencia. En este estudio, se evaluó la eficacia de dos de estas vacunas en la protección de patos Pekin frente al desafío con un aislamiento aviar H5N2 de alta patogenicidad. Se utilizaron una vacuna recombinante basada en alfavirus y una vacuna generada por genética inversa, inactivada y con adyuvante, ambas expresando el gene de la hemaglutinina de un aislamiento H5 clado 2.3.4.4 (A/Gyrfalcon/Washington/41088-6/2014 H5N8), para inmunizar los patos. Las vacunas se administraron como vacunación única a los 2 días de edad o con un programa de primovacunación y refuerzo a los 2 y 15 días de edad. A los 32 días de edad, todos los patos fueron desafiados con el virus de alta patogenicidad A/turkey/Minnesota/12582/15 H5N2 clado 2.3.4.4. Todos los patos del grupo control no vacunado y desafiado se infectaron y excretaron al virus; un pato en este grupo presentó ataxia leve y un segundo pato murió. No se observó mortalidad o signos clínicos en patos vacunados y desafiados, con la excepción de un pato que presentó ataxia leve. Ambas vacunas, independientemente de la estrategia de vacunación utilizada, fueron inmunogénicas en patos y redujeron o evitaron la diseminación del virus después del desafío. En conclusión, se logró una buena protección contra la infección por H5N2 en los patos vacunados con las vacunas evaluadas, las cuales eran homólogas al virus de desafío y las estrategias de primovacunación y refuerzo confirieron la mejor protección contra la infección.