Neutralization of five SARS-CoV-2 variants of concern by convalescent and BBIBP-CorV vaccinee serum

The prevalence of SARS-CoV-2 variants of concern (VOCs) is still escalating throughout the world. However, the level of neutralization of the inactivated viral vaccine recipients’ sera and convalescent sera against all VOCs, including B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.617.2 (Delta), and B.1.1.529 (Omicron) remains to be lack of comparative analysis. Therefore, we constructed pseudoviruses of five VOCs using a lentiviral-based system and analyzed their viral infectivity and neutralization resistance to convalescent and BBIBP-CorV vaccinee serum at different times. Our results show that, compared with the wild-type strain (WT), five VOC pseudoviruses showed higher infection, of which B.1.617.2 and B.1.1.529 variant pseudoviruses exhibited higher infection rates than wild-type or other VOC strains, respectively. Sera from 10 vaccinated individuals at the 1, 3 and 5-month post second dose or from 10 convalescent at 14 and 200 days after discharge retained neutralizing activity against all strains but exhibited decreased neutralization activity significantly against the five VOC variant pseudoviruses over time compared to WT. Notably, 100% (30/30) of the vaccinee serum samples showed more than a 2.5-fold reduction in neutralizing activity against B.1.1.529, and 90% (18/20) of the convalescent serum samples showed more than 2.5-fold reduction in neutralization against B.1.1.529. These findings demonstrate the reduced protection against the VOCs in vaccinated and convalescent individuals over time, indicating that it is necessary to have a booster shot and develop new vaccines capable of eliciting broad neutralization antibodies.     

Virus-Like Particle Vaccine Protects against 2009 H1N1 Pandemic Influenza Virus in Mice

Background

The 2009 influenza pandemic and shortages in vaccine supplies worldwide underscore the need for new approaches to develop more effective vaccines.

Methodology/Principal Findings

We generated influenza virus-like particles (VLPs) containing proteins derived from the A/California/04/2009 virus, and tested their efficacy as a vaccine in mice. A single intramuscular vaccination with VLPs provided complete protection against lethal challenge with the A/California/04/2009 virus and partial protection against A/PR/8/1934 virus, an antigenically distant human isolate. VLP vaccination induced predominant IgG2a antibody responses, high hemagglutination inhibition (HAI) titers, and recall IgG and IgA antibody responses. HAI titers after VLP vaccination were equivalent to those observed after live virus infection. VLP immune sera also showed HAI responses against diverse geographic pandemic isolates. Notably, a low dose of VLPs could provide protection against lethal infection.

Conclusion/Significance

This study demonstrates that VLP vaccination provides highly effective protection against the 2009 pandemic influenza virus. The results indicate that VLPs can be developed into an effective vaccine, which can be rapidly produced and avoid the need to isolate high growth reassortants for egg-based production.     

The humoral and cellular immune evasion of SARS-CoV-2 Omicron and sub-lineages

The recently discovered SARS-CoV-2 variant Omicron (B.1.1.529) has rapidly become a global public health issue. The substantial mutations in the spike protein in this new variant have raised concerns about its ability to escape from pre-existing immunity established by natural infection or vaccination. In this review, we give a summary of current knowledge concerning the antibody evasion properties of Omicron and its subvariants (BA.2, BA.2.12.1, BA.4/5, and BA.2.75) from therapeutic monoclonal antibodies and the sera of SARS-CoV-2 vaccine recipients or convalescent patients. We also summarize whether vaccine-induced cellular immunity (memory B cell and T cell response) can recognize Omicron specifically. In brief, the Omicron variants demonstrated remarkable antibody evasion, with even more striking antibody escape seen in the Omicron BA.4 and BA.5 sub-lineages. Luckily, the third booster vaccine dose significantly increased the neutralizing antibodies titers, and the vaccine-induced cellular response remains conserved and provides second-line defense against the Omicron.     

Immunogenicity of a new lot of Francisella tularensis live vaccine strain in human volunteers

Abstract A new lot of Francisella tularensis live vaccine strain (LVS) was tested for immunogenicity in 19 human volunteers. Scarification vaccination induced specific cell-mediated and humoral immune responses. We noted a significant rise in antibodies against irradiation-killed LVS, formalin-killed virulent strain SCHU4, and an ether extracted antigen preparation (EEx) beginning 14 days after vaccination. A main target of the humoral immune response was lipopolysaccharide. Eighty percent of vaccinated volunteers developed a positive IgG response to EEx by day 14 and 100% of vaccinees responded positively by day 21. Background IgA titers were lower than corresponding IgG or IgM titers. No early IgM rise was noted with any antigen. By day 14 after vaccination, in vitro lymphocyte responses to LVS, the rough variant of LVS, and EEx were significantly increased compared to controls. Seventy percent of volunteers had a positive in vitro lymphocyte response to EEx within 14 days of vaccination. We predict that EEx will be a usefull antigen for diagnosing tularemia and for evaluating the immunogenicity of vaccines against tularemia. We are testing this antigen using sera from human cases of tularemia and control sera.     

Antibody responses against SARS-CoV-2 variants induced by four different SARS-CoV-2 vaccines in health care workers in the Netherlands: A prospective cohort study

BackgroundEmerging and future SARS-CoV-2 variants may jeopardize the effectiveness of vaccination campaigns. Therefore, it is important to know how the different vaccines perform against diverse SARS-CoV-2 variants.Methods and findingsIn a prospective cohort of 165 SARS-CoV-2 naive health care workers in the Netherlands, vaccinated with either one of four vaccines (BNT162b2, mRNA-1273, AZD1222 or Ad26.COV2.S), we performed a head-to-head comparison of the ability of sera to recognize and neutralize SARS-CoV-2 variants of concern (VOCs; Alpha, Beta, Gamma, Delta and Omicron). Repeated serum sampling was performed 5 times during a year (from January 2021 till January 2022), including before and after booster vaccination with BNT162b2. Four weeks after completing the initial vaccination series, SARS-CoV-2 wild-type neutralizing antibody titers were highest in recipients of mRNA-1273, followed by recipients of BNT162b2 (geometric mean titers (GMT) of 358 [95% CI 231–556] and 214 [95% CI 153–299], respectively; p<0.05), and substantially lower in those vaccinated with the adenovirus vector-based vaccines AZD1222 and Ad26.COV2.S (GMT of 18 [95% CI 11–30] and 14 [95% CI 8–25] IU/ml, respectively; p<0.001). VOCs neutralization was reduced in all vaccine groups, with the greatest reduction in neutralization GMT observed against the Omicron variant (fold change 0.03 [95% CI 0.02–0.04], p<0.001). The booster BNT162b2 vaccination increased neutralizing antibody titers for all groups with substantial improvement against the VOCs including the Omicron variant. We used linear regression and linear mixed model analysis. All results were adjusted for possible confounding of age and sex. Study limitations include the lack of cellular immunity data.ConclusionsOverall, this study shows that the mRNA vaccines appear superior to adenovirus vector-based vaccines in inducing neutralizing antibodies against VOCs four weeks after initial vaccination and after booster vaccination, which implies the use of mRNA vaccines for both initial and booster vaccination.

Marit J. van Gils and colleagues investigate antibody responses against diverse emerging SARS-CoV-2 variants induced by four different SARS-CoV-2 vaccines in health care workers in the Netherlands.     

Cross-variant protection against SARS-CoV-2 infection in hamsters immunized with monovalent and bivalent inactivated vaccines

Rapid development and successful use of vaccines against SARS-CoV-2 might hold the key to curb the ongoing pandemic of COVID-19. Emergence of vaccine-evasive SARS-CoV-2 variants of concern (VOCs) has posed a new challenge to vaccine design and development. One urgent need is to determine what types of variant-specific and bivalent vaccines should be developed. Here, we compared homotypic and heterotypic protection against SARS-CoV-2 infection of hamsters with monovalent and bivalent whole-virion inactivated vaccines derived from representative VOCs. In addition to the ancestral SARS-CoV-2 Wuhan strain, Delta (B.1.617.2; δ) and Theta (P.3; θ) variants were used in vaccine preparation. Additional VOCs including Omicron (B.1.1.529) and Alpha (B.1.1.7) variants were employed in the challenge experiment. Consistent with previous findings, Omicron variant exhibited the highest degree of immune evasion, rendering all different forms of inactivated vaccines substantially less efficacious. Notably, monovalent and bivalent Delta variant-specific inactivated vaccines provided optimal protection against challenge with Delta variant. Yet, some cross-variant protection against Omicron and Alpha variants was seen with all monovalent and bivalent inactivated vaccines tested. Taken together, our findings support the notion that an optimal next-generation inactivated vaccine against SARS-CoV-2 should contain the predominant VOC in circulation. Further investigations are underway to test whether a bivalent vaccine for Delta and Omicron variants can serve this purpose.     

Microneedle Vaccination Elicits Superior Protection and Antibody Response over Intranasal Vaccination against Swine-Origin Influenza A (H1N1) in Mice

Influenza is one of the critical infectious diseases globally and vaccination has been considered as the best way to prevent. In this study, immunogenicity and protection efficacy between intranasal (IN) and microneedle (MN) vaccination was compared using inactivated swine-origin influenza A/H1N1 virus vaccine. Mice were vaccinated by MN or IN administration with 1 μg of inactivated H1N1 virus vaccine. Antigen-specific antibody responses and hemagglutination-inhibition (HI) titers were measured in all immunized sera after immunization. Five weeks after an immunization, a lethal challenge was performed to evaluate the protective efficacy. Furthermore, mice were vaccinated by IN administration with higher dosages (> 1 μg), analyzed in the same manner, and compared with 1 μg-vaccine-coated MN. Significantly higher antigen-specific antibody responses and HI titer were measured in sera in MN group than those in IN group. While 100% protection, slight weight loss, and reduced viral replication were observed in MN group, 0% survival rate were observed in IN group. As vaccine dose for IN vaccination increased, MN-immunized sera showed much higher antigen-specific antibody responses and HI titer than other IN groups. In addition, protective immunity of 1 μg-MN group was similar to those of 20- and 40 μg-IN groups. We conclude that MN vaccination showed more potential immune response and protection than IN vaccination at the same vaccine dosage.     

Active synthesis of hemagglutinin-specific immunoglobulin A by lung cells of mice that were immunized intragastrically with inactivated influenza virus vaccine

Intragastric inoculation with whole-virion vaccine of inactivated influenza virus resulted in production of hemagglutinin (HA)-specific immunoglobulin A (IgA) and IgG both in lung lavage fluids and in serum samples of mice. HA-specific IgA was the predominant isotypic antibody secreted in the lung lavage fluids (average IgA/IgG ratio, 13:1), whereas HA-specific IgG was the major antibody class in serum (average IgA/IgG ratio, 0.3:1). These responses were similar to the antibody responses stimulated by intranasal infection with live influenza virus. In vitro cultures of lymphoid cells from lungs and Peyer's patches, but not from spleens, in the presence of homologous antigen, from mice vaccinated intragastrically synthesized mostly HA-specific IgA. Mice immunized parenterally with inactivated influenza virus produced only IgG in lung lavage fluids and sera. Cultures of lymphoid cells from their spleens, but not their lungs, synthesized HA-specific IgG upon antigenic stimulation in vitro; neither synthesized IgA. These in vitro cell culture results, as well as the inverse relationship of IgA/IgG ratios in lung lavage fluids and sera, demonstrated that the IgA antibody in lung lavage fluids was actively synthesized locally in the lungs of intragastrically immunized mice. This finding was consistent with the migratory distribution of antigen-primed lymphoid cells from Peyer's patches to distant lymphoid tissue such as lung. Intragastric vaccination conferred protection against intranasal challenge with a lethal dose of virulent virus.     

Human immune responses elicited by an intranasal inactivated H5 influenza vaccine

Intranasally administered influenza vaccines could be more effective than injected vaccines, because intranasal vaccination can induce virus-specific immunoglobulin A (IgA) antibodies in the upper respiratory tract, which is the initial site of infection. In this study, immune responses elicited by an intranasal inactivated vaccine of influenza A(H5N1) virus were evaluated in healthy individuals naive for influenza A(H5N1) virus. Three doses of intranasal inactivated whole-virion H5 influenza vaccine induced strong neutralizing nasal IgA and serum IgG antibodies. In addition, a mucoadhesive excipient, carboxy vinyl polymer, had a notable impact on the induction of nasal IgA antibody responses but not on serum IgG antibody responses. The nasal hemagglutinin (HA)-specific IgA antibody responses clearly correlated with mucosal neutralizing antibody responses, indicating that measurement of nasal HA-specific IgA titers could be used as a surrogate for the mucosal antibody response. Furthermore, increased numbers of plasma cells and vaccine antigen-specific Th cells in the peripheral blood were observed after vaccination, suggesting that peripheral blood biomarkers may also be used to evaluate the intranasal vaccine-induced immune response. However, peripheral blood immune cell responses correlated with neutralizing antibody titers in serum samples but not in nasal wash samples. Thus, analysis of the peripheral blood immune response could be a surrogate for the systemic immune response to intranasal vaccination but not for the mucosal immune response. The current study suggests the clinical potential of intranasal inactivated vaccines against influenza A(H5N1) viruses and highlights the need to develop novel means to evaluate intranasal vaccine-induced mucosal immune responses.     

Recombinant IgA Is Sufficient To Prevent Influenza Virus Transmission in Guinea Pigs

A serum hemagglutination inhibition (HAI) titer of 40 or greater is thought to be associated with reduced influenza virus pathogenesis in humans and is often used as a correlate of protection in influenza vaccine studies. We have previously demonstrated that intramuscular vaccination of guinea pigs with inactivated influenza virus generates HAI titers greater than 300 but does not protect vaccinated animals from becoming infected with influenza virus by transmission from an infected cage mate. Only guinea pigs intranasally inoculated with a live influenza virus or a live attenuated virus vaccine, prior to challenge, were protected from transmission (A. C. Lowen et al., J. Virol. 83:2803–2818, 2009.). Because the serum HAI titer is mostly determined by IgG content, these results led us to speculate that prevention of viral transmission may require IgA antibodies or cellular immune responses. To evaluate this hypothesis, guinea pigs and ferrets were administered a potent, neutralizing mouse IgG monoclonal antibody, 30D1 (Ms 30D1 IgG), against the A/California/04/2009 (H1N1) virus hemagglutinin and exposed to respiratory droplets from animals infected with this virus. Even though HAI titers were greater than 160 1 day postadministration, Ms 30D1 IgG did not prevent airborne transmission to passively immunized recipient animals. In contrast, intramuscular administration of recombinant 30D1 IgA (Ms 30D1 IgA) prevented transmission to 88% of recipient guinea pigs, and Ms 30D1 IgA was detected in animal nasal washes. Ms 30D1 IgG administered intranasally also prevented transmission, suggesting the importance of mucosal immunity in preventing influenza virus transmission. Collectively, our data indicate that IgG antibodies may prevent pathogenesis associated with influenza virus infection but do not protect from virus infection by airborne transmission, while IgA antibodies are more important for preventing transmission of influenza viruses.     

Mucosal delivery of inactivated influenza vaccine induces B-cell-dependent heterosubtypic cross-protection against lethal influenza A H5N1 virus infection

Influenza vaccines that induce greater cross-reactive or heterosubtypic immunity (Het-I) may overcome limitations in vaccine efficacy imposed by the antigenic variability of influenza A viruses. We have compared mucosal versus traditional parenteral administration of inactivated influenza vaccine for the ability to induce Het-I in BALB/c mice and evaluated a modified Escherichia coli heat-labile enterotoxin adjuvant, LT(R192G), for augmentation of Het-I. Mice that received three intranasal (i.n.) immunizations of H3N2 vaccine in the presence of LT(R192G) were completely protected against lethal challenge with a highly pathogenic human H5N1 virus and had nasal and lung viral titers that were at least 2,500-fold lower than those of control mice receiving LT(R192G) alone. In contrast, mice that received three vaccinations of H3N2 vaccine subcutaneously in the presence or absence of LT(R192G) or incomplete Freund's adjuvant were not protected against lethal challenge and had no significant reductions in tissue virus titers observed on day 5 post-H5N1 virus challenge. Mice that were i.n. administered H3N2 vaccine alone, without LT(R192G), displayed partial protection against heterosubtypic challenge. The immune mediators of Het-I were investigated. The functional role of B and CD8+ T cells in Het-I were evaluated by using gene-targeted B-cell (IgH-6(-/-))- or beta2-microglobulin (beta2m(-/-))-deficient mice, respectively. beta2m(-/-) but not IgH-6(-/-) vaccinated mice were protected by Het-I and survived a lethal infection with H5N1, suggesting that B cells, but not CD8+ T cells, were vital for protection of mice against heterosubtypic challenge. Nevertheless, CD8+ T cells contributed to viral clearance in the lungs and brain tissues of heterotypically immune mice. Mucosal but not parenteral vaccination induced subtype cross-reactive lung immunoglobulin G (IgG), IgA, and serum IgG anti-hemagglutinin antibodies, suggesting the presence of a common cross-reactive epitope in the hemagglutinins of H3 and H5. These results suggest a strategy of mucosal vaccination that stimulates cross-protection against multiple influenza virus subtypes, including viruses with pandemic potential.     

A replication-incompetent PB2-knockout influenza A virus vaccine vector

Vaccination is the primary form of protection from influenza virus infection. We recently developed a replication-incompetent PB2-knockout (PB2-KO) influenza virus that possesses a reporter gene (the green fluorescent protein gene) in the coding region of the PB2 segment. This virus replicated to high titers in PB2-expressing, but not unmodified, cells, suggesting its potential safety and feasibility as a vaccine. Here, we tested its efficacy in a murine model. The levels of IgG and IgA antibodies against influenza virus in sera, nasal washes, and bronchoalveolar lavage fluids of mice immunized with the PB2-KO virus were higher than those induced by a conventional inactivated vaccine. All PB2-KO virus-immunized mice survived challenges with lethal doses of influenza virus. Moreover, importantly, mice immunized with the PB2-KO virus produced antibodies against the reporter protein, suggesting that the PB2-KO virus has potential as a multivalent vaccine to combat infection with not only influenza virus but also other pathogens.     

Humoral and Cellular Immune Responses of COVID-19 vaccines against SARS-Cov-2 Omicron variant: a systemic review

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has undergone multiple mutations since its emergence, and its latest variant, Omicron (B.1.1.529), is the most contagious variant of concern (VOC) which poses a major and imminent threat to public health. Since firstly reported by World Health Organization (WHO) in November 2021, Omicron variant has been spreading rapidly and has become the dominant variant in many countries worldwide. Omicron is the most mutated variant so far, containing 60 mutations in its genome, including 37 mutations in the S-protein. Since all current COVID-19 vaccines in use were developed based on ancestral SARS-CoV-2 strains, whether they are protective against Omicron is a critical question which has been the center of study currently. In this article, we systemically reviewed the studies regarding the effectiveness of 2- or 3-dose vaccines delivered in either homologous or heterologous manner. The humoral and cellular immune responses elicited by various vaccine regimens to protect against Omicron variant are discussed. Current understanding of the molecular basis underlying immune escape of Omicron was also analyzed. These studies indicate that two doses of vaccination are insufficient to elicit neutralizing antibody responses against Omicron variant. Nevertheless, Omicron-specific humoral immune responses can be enhanced by booster dose of almost all type vaccines in certain degree, and heterologous vaccination strategy may represent a better choice than homogenous regimens. Intriguingly, results of studies indicate that all current vaccines are still able to elicit robust T cell response against Omicron. Future focus should be the development of Omicron variant vaccine, which may induce potent humoral as well as cellular immune responses simultaneously against all known variants of the SARS-CoV-2 virus.     

Mucosal but Not Parenteral Immunization with Purified Human Papillomavirus Type 16 Virus-Like Particles Induces Neutralizing Titers of Antibodies throughout the Estrous Cycle of Mice

We have recently shown that nasal immunization of anesthetized mice with human papillomavirus type 16 (HPV16) virus-like particles (VLPs) is highly effective at inducing both neutralizing immunoglobulin A (IgA) and IgG in genital secretions, while parenteral immunization induced only neutralizing IgG. Our data also demonstrated that both isotypes are similarly neutralizing according to an in vitro pseudotyped neutralization assay. However, it is known that various amounts of IgA and IgG are produced in genital secretions along the estrous cycle. Therefore, we have investigated how this variation influences the amount of HPV16 neutralizing antibodies induced after immunization with VLPs. We have compared parenteral and nasal protocols of vaccination with daily samplings of genital secretions of mice. Enzyme-linked immunosorbent assay analysis showed that total IgA and IgG inversely varied along the estrous cycle, with the largest amounts of IgA in proestrus-estrus and the largest amount of IgG in diestrus. This resulted in HPV16 neutralizing titers of IgG only being achieved during diestrus upon parenteral immunization. In contrast, nasal vaccination induced neutralizing titers of IgA plus IgG throughout the estrous cycle, as confirmed by in vitro pseudotyped neutralization assays. Our data suggest that mucosal immunization might be more efficient than parenteral immunization at inducing continuous protection of the female genital tract.     

Safety,Immunogenicity and Duration of Immunity Elicited by an Inactivated Bovine Ephemeral Fever Vaccine

Bovine ephemeral fever (BEF) is an economically important viral vector-borne cattle disease. Several live-attenuated, inactivated and recombinant vaccines have been tested, demonstrating varying efficacy. However, to the best of our knowledge, duration of immunity conferred by an inactivated vaccine has never been reported. In the last decade, Israel has faced an increasing number of BEF outbreaks. The need for an effective vaccine compatible with strains circulating in the Middle East region led to the development of a MONTANIDE™ ISA 206 VG (water-in-oil-in-water), inactivated vaccine based on a local strain. We tested the safety, immunogenicity and duration of immunity conferred by this vaccine. The induced neutralizing antibody (NA) response was followed for 493 days in 40 cows vaccinated by different protocols. The vaccine did not cause adverse reactions or a decrease in milk production. All cows [except 2 (6.7%) which did not respond to vaccination] showed a significant rise in NA titer of up to 1:256 following the second, third or fourth booster vaccination. Neutralizing antibody levels declined gradually to 1:16 up to 120 days post vaccination. This decline continued in cows vaccinated only twice, whereas cows vaccinated 3 or 4 times showed stable titers of approximately 1:16 for up to 267 days post vaccination. At least three vaccinations with the inactivated BEF vaccine were needed to confer long-lasting immunity. These results may have significant implications for the choice of vaccination protocol with inactivated BEF vaccines. Complementary challenge data should however be added to the above results in order to determine what is the minimal NA response conferring protection from clinical disease.     

A human coronavirus evolves antigenically to escape antibody immunity

There is intense interest in antibody immunity to coronaviruses. However, it is unknown if coronaviruses evolve to escape such immunity, and if so, how rapidly. Here we address this question by characterizing the historical evolution of human coronavirus 229E. We identify human sera from the 1980s and 1990s that have neutralizing titers against contemporaneous 229E that are comparable to the anti-SARS-CoV-2 titers induced by SARS-CoV-2 infection or vaccination. We test these sera against 229E strains isolated after sera collection, and find that neutralizing titers are lower against these “future” viruses. In some cases, sera that neutralize contemporaneous 229E viral strains with titers >1:100 do not detectably neutralize strains isolated 8–17 years later. The decreased neutralization of “future” viruses is due to antigenic evolution of the viral spike, especially in the receptor-binding domain. If these results extrapolate to other coronaviruses, then it may be advisable to periodically update SARS-CoV-2 vaccines.     

Evaluation of the European tick‐borne encephalitis vaccine against Omsk hemorrhagic fever virus

This study focused on the antigenic cross‐reactivity between tick‐borne encephalitis virus (TBEV) and Omsk hemorrhagic fever virus (OHFV) to assess the efficacy of the commercial TBE vaccine against OHFV infection. Neutralization tests performed on sera from OHFV‐ and TBEV‐infected mice showed that neutralizing antibodies are cross‐protective. The geometric mean titers of antibodies against TBEV and OHFV from TBEV‐infected mice were similar. However, the titers of anti‐TBEV antibodies in OHFV‐infected mice were significantly lower than those of anti‐OHFV antibodies in the same animals. In mouse vaccination and challenge tests, the TBE vaccine provided 100% protection against OHFV infection. Eighty‐six percent of vaccinees seroconverted against OHFV following complete vaccination, and the geometric mean titers of neutralizing antibodies against OHFV were comparable to those against TBEV. These data suggest that the TBE vaccine can prevent OHFV infection.     

SARS-CoV-2重组S1和S蛋白疫苗诱导保护性免疫的研究*

目的:评价新型冠状病毒(SARS-CoV-2)重组S1蛋白和S蛋白疫苗对SARS-CoV-2的免疫保护效果。方法:将SARS-CoV-2重组S1蛋白和S蛋白分别联合氢氧化铝佐剂以0.1 μg/只、1 μg/只、5 μg/只、10 μg/只不同剂量接种6~8周BALB/c纯系健康雌性小鼠。第二次免疫后采血通过酶联免疫吸附试验(ELISA)检测血清中IgG抗体效价,通过假病毒中和试验比较免疫小鼠血清对SARS-CoV-2野生型株(WT)、英国株(B.1.1.7)、巴西株(P.1)、印度株(B.1.617.2)、Mu毒株(B.1.621)和南非株(501Y.V2-1)六种假病毒毒株中和活性效价,取脾细胞通过酶联免疫斑点技术(ELISpot)检测免疫小鼠的细胞免疫水平。结果:SARS-CoV-2重组S和S1蛋白都能诱导小鼠产生较强的IgG抗体水平。免疫S1蛋白的小鼠血清对SARS-CoV-2野生型株、英国株、巴西株有明显的中和活性,免疫S蛋白的小鼠血清除了对SARS-CoV-2野生型株、英国株、巴西株有明显中和活性之外,对印度株也有明显的中和活性,两种蛋白质免疫的小鼠血清均对野生型株中和效果最强。S蛋白免疫的小鼠脾细胞能够显著诱导出γ干扰素(IFN-γ)和白介素-4(IL-4)的产生。S蛋白诱导产生的IgG抗体、中和抗体、细胞免疫水平均高于S1。结论:SARS-CoV-2重组S蛋白疫苗能够诱导产生较强的保护性免疫应答。     

Evaluation of tri-combinant vaccine for feline herpesvirus, calicivirus and panleukopenia virus infections in Japanese native cats

Tri-combinant vaccine consisting of attenuated feline herpesvirus (FHV) and feline calicivirus (FCV) and inactivated feline panleukopenia virus (FPLV), were evaluated for safety and efficacy, using Japanese native cats and the viral strains isolated in Japan. Thirty-eight 9- to 12-week-old kittens were inoculated intramuscularly and subcutaneously with the vaccine. Consequently, no adverse reaction was found, and protective efficacy was confirmed by challenge tests with the virulent strains of each virus. Serum-neutralizing antibodies against FCV and FPLV were maintained for at least one year after vaccination, whereas antibody against FHV disappeared in two cases at 24 weeks after vaccination. Application of this vaccine seemed effective for control of feline viral disease in cats for experimental use.     

Vaccination with M2e-based multiple antigenic peptides: characterization of the B cell response and protection efficacy in inbred and outbred mice

Background

The extracellular domain of the influenza A virus protein matrix protein 2 (M2e) is remarkably conserved between various human isolates and thus is a viable target antigen for a universal influenza vaccine. With the goal of inducing protection in multiple mouse haplotypes, M2e-based multiple antigenic peptides (M2e-MAP) were synthesized to contain promiscuous T helper determinants from the Plasmodium falciparum circumsporozoite protein, the hepatitis B virus antigen and the influenza virus hemagglutinin. Here, we investigated the nature of the M2e-MAP-induced B cell response in terms of the distribution of antibody (Ab) secreting cells (ASCs) and Ab isotypes, and tested the protective efficacy in various mouse strains.

Methodology/Principal Findings

Immunization of BALB/c mice with M2e-MAPs together with potent adjuvants, CpG 1826 oligonucleotides (ODN) and cholera toxin (CT) elicited high M2e-specific serum Ab titers that protected mice against viral challenge. Subcutaneous (s.c.) and intranasal (i.n.) delivery of M2e-MAPs resulted in the induction of IgG in serum and airway secretions, however only i.n. immunization induced anti-M2e IgA ASCs locally in the lungs, correlating with M2-specific IgA in the bronchio-alveolar lavage (BAL). Interestingly, both routes of vaccination resulted in equal protection against viral challenge. Moreover, M2e-MAPs induced cross-reactive and protective responses to diverse M2e peptides and variant influenza viruses. However, in contrast to BALB/c mice, immunization of other inbred and outbred mouse strains did not induce protective Abs. This correlated with a defect in T cell but not B cell responsiveness to the M2e-MAPs.

Conclusion/Significance

Anti-M2e Abs induced by M2e-MAPs are highly cross-reactive and can mediate protection to variant viruses. Although synthetic MAPs are promising designs for vaccines, future constructs will need to be optimized for use in the genetically heterogeneous human population.