Intranasal vaccination with a recombinant vesicular stomatitis virus expressing cottontail rabbit papillomavirus L1 protein provides complete protection against papillomavirus-induced disease

Immunizations with live recombinant vesicular stomatitis viruses (rVSV) expressing foreign viral proteins have successfully protected animals from challenges with several heterologous viruses. We developed an rVSV expressing the major capsid protein (L1) of cottontail rabbit papillomavirus (CRPV) and tested the efficacy of protection following CRPV challenge. An rVSV expressing L1 of CRPV (VSV-L1) was characterized for the protective ability afforded by intranasal, intradermal, or intramuscular vaccination in rabbits subsequently challenged with CRPV. Protein expression of L1 in VSV-L1 was confirmed by radioimmunoprecipitation assays. Nuclear localization of L1 was demonstrated by indirect immunofluorescence assays. Immunized rabbits elicited significant VSV neutralization and VLP-L1 enzyme-linked immunosorbent assay titers. VSV-L1 vaccination was not associated with weight loss or any other adverse clinical signs in the rabbit model. VSV shedding in nasal secretions occurred in some rabbits, peaking at 4 to 6 days after intranasal vaccination, with no further shedding after day 6. Specific humoral immunity to the L1 protein was consistently seen after a single VSV-L1 vaccination when administered through an intradermal or intramuscular route or after a boost via the intranasal route. Rabbits were completely protected from CRPV-induced papillomas after VSV-L1 vaccination and boost given intranasally or intramuscularly. Vaccination with VSV-L1 is a novel approach to prevent papillomavirus-induced disease and demonstrates a potential strategy for developing a human papillomavirus vaccine that can be given without injection.     

Synthetic double-stranded RNA poly(I:C) combined with mucosal vaccine protects against influenza virus infection

The mucosal adjuvant effect of synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid [poly(I:C)] against influenza virus was examined under intranasal coadministration with inactivated hemagglutinin (HA) vaccine in BALB/c mice and was shown to have a protective effect against both nasal-restricted infection and lethal lung infection. Intranasal administration of vaccine from PR8 (H1N1) with poly(I:C) induced a high anti-HA immunoglobulin A (IgA) response in the nasal wash and IgG antibody response in the serum, while vaccination without poly(I:C) induced little response. Intracerebral injection confirmed the safety of poly(I:C). In addition, we demonstrated that administration of poly(I:C) with either A/Beijing (H1N1) or A/Yamagata (H1N1) vaccine conferred complete protection against PR8 challenge in this mouse nasal infection model, suggesting that poly(I:C) possessed cross-protection ability against variant viruses. To investigate the mechanism of the protective effect of poly(I:C), mRNA levels of Toll-like receptors and cytokines were examined in the nasal-associated lymphoid tissue after vaccination or virus challenge. Intranasal administration of HA vaccine with poly(I:C) up-regulated expression of Toll-like receptor 3 and alpha/beta interferons as well as Th1- and Th2-related cytokines. We propose that poly(I:C) is a new effective intranasal adjuvant for influenza virus vaccine.     

A DNA vaccine prime followed by a liposome-encapsulated protein boost confers enhanced mucosal immune responses and protection

A variety of DNA vaccine prime and recombinant viral boost immunization strategies have been developed to enhance immune responses in humans, but inherent limitations to these strategies exist. There is still an overwhelming need to develop safe and effective approaches that raise broad humoral and T cell-mediated immune responses systemically and on mucosal surfaces. We have developed a novel mucosal immunization regimen that precludes the use of viral vectors yet induces potent T cell responses. Using hepatitis B surface Ag (HBsAg), we observed that vaccination of BALB/c mice with an i.m. HBsAg-DNA vaccine prime followed by an intranasal boost with HBsAg protein encapsulated in biologically inert liposomes enhanced humoral and T cell immune responses, particularly on mucosal surfaces. Intranasal live virus challenge with a recombinant vaccinia virus expressing HBsAg revealed a correlation between T cell immune responses and protection of immunized mice. A shortened immunization protocol was developed that was successful in both adult and neonatal mice. These results support the conclusion that this new approach is capable of generating a Th-type-1-biased, broad spectrum immune response, specifically at mucosal surfaces. The success of this design may provide a safe and effective vaccination alternative for human use.     

A replication-deficient murine gamma-herpesvirus blocked in late viral gene expression can establish latency and elicit protective cellular immunity

The human gamma-herpesviruses, EBV and Kaposi's sarcoma-associated herpesvirus, are widely disseminated and are associated with the onset of a variety of malignancies. Thus, the development of prophylactic and therapeutic vaccination strategies is an important goal. The experimental mouse gamma-herpesvirus, gammaHV68 (or MHV-68), has provided an in vivo model for studying immune control of these persistent viruses. In the current studies, we have examined infectivity, immunogenicity, and protective efficacy following infection with a replication-deficient gammaHV68 blocked in late viral gene expression, ORF31STOP. The data show that ORF31STOP was able to latently infect B cells. However, the anatomical site and persistence of the infection depended on the route of inoculation, implicating a role for viral replication in viral spread but not the infectivity per se. Furthermore, i.p. infection with ORF31STOP elicited strong cellular immunity but a non-neutralizing Ab response. In contrast, intranasal infection was poorly immunogenic. Consistent with this, mice infected i.p. had enhanced control of both the lytic and latent viral loads following challenge with wild-type gammaHV68, whereas intranasal infected mice were not protected. These data provide important insight into mechanisms of infection and protective immunity for the gamma-herpesviruses and demonstrate the utility of replication-deficient mutant viruses in direct testing of "proof of principal" vaccination strategies.     

The envelope proteins from purified respiratory syncytial virus protect mice from intranasal virus challenge

A lyophilized subunit vaccine prepared from purified respiratory syncytial virus, which contained the envelope glycoproteins F and G and the nonglycosylated matrix protein VPM, was tested in SJL mice for its ability to protect the lungs of mice from intranasal viral challenge. Initially, the mice were injected subcutaneously with one, two, or three doses of 5 or 25 micrograms of vaccine in 50% complete Freund's adjuvant or with complete Freund's adjuvant or phosphate-buffered saline only. Although none of the mice produced neutralizing serum antibody, three doses of 25 micrograms elicited antibodies to F, G, and VPM. Despite the absence of detectable neutralizing antibodies, the lungs of 93% of the vaccinated mice were protected from intranasal viral challenge. Because the initial protocol did not elicit neutralizing antibodies and a few single-dose animals were not protected, a second vaccine trial was carried out. For these studies the priming dose was increased to 50 micrograms, which was followed, in half the vaccine recipients, by a second dose of 25 micrograms. Mice given the priming dose of vaccine produced antibody to G and showed no neutralizing activity, whereas the mice given two doses of vaccine produced antibodies to G, F, and VPM and also displayed neutralizing activity for respiratory syncytial virus. The lungs of 100% of the vaccine recipients in this trial were protected from intranasal challenge. Although the vaccine elicited antibody to VPM, this response did not correlate with protection. In addition, examination of the sera from unimmunized mice recovering from respiratory syncytial virus infection revealed a serum antibody profile similar to that noted for humans, lacking antibody to VPM. Thus, the data show that a combined glycoprotein subunit vaccine affords complete protection to viral challenge and offers an approach to develop a multivalent subunit vaccine.     

Engineering attenuated virus vaccines by controlling replication fidelity

Long-lasting protection against viral infection is best achieved by vaccination with attenuated viruses. Obtaining stably attenuated vaccine strains has traditionally been an empirical process, which greatly restricts the number of effective vaccines for viral diseases. Here we describe a rational approach for engineering stably attenuated viruses that can serve as safe and effective vaccines. Our approach exploits the observation that restricting viral population diversity by increasing replication fidelity greatly reduces viral tissue tropism and pathogenicity. We show that poliovirus variants with reduced genetic diversity elicit a protective immune response in an animal model of infection. Indeed, these novel vaccine candidates are comparable in efficacy to the currently available Sabin type 1 vaccine strain, but have the added advantage of being more stable, as their increased replication fidelity prevents reversion to the pathogenic wild-type phenotype. We propose that restricting viral quasispecies diversity provides a general approach for the rational design of stable, attenuated vaccines for a wide variety of viruses.     

Preexisting immunity to poliovirus does not impair the efficacy of recombinant poliovirus vaccine vectors

Recombinant viruses are attractive candidates for the development of novel vaccines. A number of viruses have been engineered as vaccine vectors to express antigens from other pathogens or tumors. Inoculation of susceptible animals with this type of recombinant virus results in the induction of both humoral and cellular immune responses directed against the foreign antigens. A general problem to this approach is that existing immunity to the vector can diminish or completely abolish the efficacy of the viral vector. In this study, we investigated whether poliovirus recombinants are capable of inducing effective immunity to the foreign antigen in previously vaccinated animals. Antipoliovirus immunity was induced in susceptible mice by intraperitoneal immunization with live poliovirus. Immunized mice developed antibodies directed against capsid proteins that effectively neutralized poliovirus in vitro and protected animals from a lethal challenge with a high dose of pathogenic poliovirus. To test whether preexisting immunity reduces the efficacy of vaccination with recombinant poliovirus, immunized mice were inoculated with a recombinant poliovirus expressing the C-terminal half of chicken ovalbumin (Polio-Ova). Animals developed ovalbumin-specific antibodies and cytotoxic T lymphocytes (CTL). While the antibody titers observed in preimmune and naive mice were similar, the overall CTL response appeared to be reduced in preimmune mice. Importantly, vaccination with Polio-Ova was able to effectively protect preimmune mice against lethal challenge with a tumor expressing the antigen. Thus, preexisting immunity to poliovirus does not compromise seriously the efficacy of replication-competent poliovirus vaccine vectors. These results contrast with those observed for other viral vaccine vectors and suggest that preexisting immunity does not equally affect the vaccine potential of individual viral vectors.     

Induction of protective immune response to intranasal administration of influenza virus-like particles in a mouse model

Human influenza A viruses (IAVs) cause global pandemics and epidemics, which remains a nonignorable serious concern for public health worldwide. To combat the surge of viral outbreaks, new treatments are urgently needed. Here, we design a new vaccine based on virus-like particles (VLPs) and show how intranasal administration of this vaccine triggers protective immunity, which can be exploited for the development of new therapies. H1N1 VLPs were produced in baculovirus vectors and were injected into BALB/c mice by the intramuscular (IM) or intranasal (IN) route. We found that there were significantly higher inflammatory cell and lymphocyte concentrations in bronchoalveolar lavage samples and the lungs of IN immunized mice; however, the IM group had little signs of inflammatory responses. On the basis of our results, immunization with H1N1 influenza VLP elicited a strong T cell immunity in BALB/c mice. Despite T cell immunity amplification after both IN and IM vaccination methods in mice, IN-induced T cell responses were significantly more intense than IM-induced responses, and this was likely related to an increased number of both CD11b^high and CD103⁺ dendritic cells in mice lungs after IN administration of VLP. Furthermore, evaluation of interleukin-4 and interferon gamma cytokines along with several chemokine receptors showed that VLP vaccination via IN and IM routes leads to a greater CD4⁺ Th1 and Th2 response, respectively. Our findings indicated that VLPs represent a potential strategy for the development of an effective influenza vaccine; however, employing relevant routes for vaccination can be another important part of the universal influenza vaccine puzzle.     

Do we need nasal vaccines against COVID 19 to suppress the transmission of infections?

Covid-19 vaccines have within the first year prevented about 14 million deaths but did not induce a strong mucosal immune response. Data from US, UK, Singapore and Israel showed a variable and mostly modest effects of vaccination on virus excretion during breakthrough infections. Contact studies showed decreased transmission of infection from vaccinated index cases, but the effect varied according to dominant virus type, with study type and the nature of the contact group and diminished with time after vaccination. Some researchers suspect that it is unlikely to stop the pandemic with injected vaccines alone. Promising animal experiments were conducted with mucosal vaccines. Mice nasally immunized with a chimpanzee adenovirus vector mounted a mucosal immune response, were protected against viral challenge after a single vaccine dose and suppressed nasal replication of the challenge virus. Phage T4 expressing SARS-CoV-2 spike and nucleocapsid induced a sterilizing lung immunity in nasally vaccinated mice. Also hamsters intranasally immunized with the prefusion-stabilized spike protein showed no infectious virus in nasal turbinates upon challenge. Other studies showed that intranasal vaccination with an adenovirus vaccine reduced but did not eliminated viral transmission from infected to naïve hamsters. Intranasal vaccination of rhesus macaques with adenovirus vaccines also substantially reduced or even suppressed viral replication in the upper and lower respiratory tract. Human data on mucosal SARS-CoV-2 vaccines are so far limited to safety and immunogenicity studies. Aerosolized adenovirus vaccines given either as a booster or as primary immunization were safe and induced similar or superior immune response than injected vaccines while an aerosolized influenza vectored vaccine induced only a weak humoral and cellular immune response. Overall 100 mucosal SARS-CoV-2 vaccines are in development and 20 are in clinical trials. First human trials demonstrate that this will not be an easy task.     

Comparative studies of the capsid precursor polypeptide P1 and the capsid protein VP1 cDNA vectors for DNA vaccination against foot-and-mouth disease virus

BACKGROUND: Foot-and-mouth disease virus (FMDV) causes a severe livestock disease, and the virus is an interesting target for virology and vaccine studies. MATERIALS AND METHODS: Here we evaluated comparatively three different viral antigen-encoding DNA sequences, delivered via two physical means (i.e., gene gun delivery into skin and electroporation delivery into muscle), for naked DNA-mediated vaccination in a mouse system. RESULTS: Both methods gave similar results, demonstrating commonality of the observed DNA vaccine effects. Immunization with a cDNA vector expressing the major viral antigen (VP1) alone routinely failed to induce the production of anti-VP1 or neutralizing antibodies in test mice. As a second approach, the plasmid L-VP1 that produces a transgenic membrane-anchored VP1 protein elicited a strong antibody response, but all test mice failed in the FMDV challenge experiment. In contrast, for mice immunized with the viral capsid precursor protein (P1) cDNA expression vector, both neutralizing antibodies and 80-100% protection in test mice were detected. CONCLUSIONS: This strategy of using the whole capsid precursor protein P1 cDNA for vaccination, intentionally without the use of virus-specific protease or other encoding genes for safety reasons, may thus be employed as a relevant experimental system for induction or upgrading of effective neutralizing antibody response, and as a convenient surrogate test system for DNA vaccination studies of FMDV and presumably other viral diseases.     

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.     

Durability of a Vesicular Stomatitis Virus-Based Marburg Virus Vaccine in Nonhuman Primates

The filoviruses, Marburg virus (MARV) and Ebola virus, causes severe hemorrhagic fever with high mortality in humans and nonhuman primates. A promising filovirus vaccine under development is based on a recombinant vesicular stomatitis virus (rVSV) that expresses individual filovirus glycoproteins (GPs) in place of the VSV glycoprotein (G). These vaccines have shown 100% efficacy against filovirus infection in nonhuman primates when challenge occurs 28–35 days after a single injection immunization. Here, we examined the ability of a rVSV MARV-GP vaccine to provide protection when challenge occurs more than a year after vaccination. Cynomolgus macaques were immunized with rVSV-MARV-GP and challenged with MARV approximately 14 months after vaccination. Immunization resulted in the vaccine cohort of six animals having anti-MARV GP IgG throughout the pre-challenge period. Following MARV challenge none of the vaccinated animals showed any signs of clinical disease or viremia and all were completely protected from MARV infection. Two unvaccinated control animals exhibited signs consistent with MARV infection and both succumbed. Importantly, these data are the first to show 100% protective efficacy against any high dose filovirus challenge beyond 8 weeks after final vaccination. These findings demonstrate the durability of VSV-based filovirus vaccines.     

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.     

Elicitation of neutralizing antibodies by intranasal administration of recombinant vesicular stomatitis virus expressing human immunodeficiency virus type 1 gp120

Recombinant viral vectors are useful tools for AIDS vaccine development. However, expression of HIV-1 envelope genes using viral vectors has not been successful in the induction of potent neutralizing antibodies in vivo. We took advantage of the strong immunogenicity of vesicular stomatitis virus (VSV)-based vector and expressed HIV-1 HXB2 gp120 gene in the recombinant VSV. Our results showed that HIV-1 gp120 protein expressed by the recombinant VSV retained the native conformation of the protein to some degree and was recognized by two well-characterized broad anti-HIV-1 neutralizing monoclonal antibodies b12, 2G12. We further showed that only one time intranasal immunization with the recombinant VSV led to production of anti-HIV-1 anti-sera in mice. In addition, we found that the anti-sera had the ability to neutralize not only HXB2 envelope-pseudotyped HIV-1 viruses but also HIV-1 pseudotyped viruses with JRFL envelopes. These results suggest that HIV-1 gp120 expressed by the recombinant VSV, in combination with the route of intranasal administration, is an effective strategy to evaluate the immunogenicity of HIV-1 envelope protein and its variants in mice.     

DNA immunization with plasmids encoding fusion and nucleocapsid proteins of bovine respiratory syncytial virus induces a strong cell-mediated immunity and protects calves against challenge

Respiratory syncytial viruses (RSV) are one of the most important respiratory pathogens of humans and cattle, and there is currently no safe and effective vaccine prophylaxis. In this study, we designed two codon-optimized plasmids encoding the bovine RSV fusion (F) and nucleocapsid (N) proteins and assessed their immunogenicity in young calves. Two administrations of both plasmids elicited low antibody levels but primed a strong cell-mediated immunity characterized by lymphoproliferative response and gamma interferon production in vitro and in vivo. Interestingly, this strong cellular response drastically reduced viral replication, clinical signs, and pulmonary lesions after a highly virulent challenge. Moreover, calves that were further vaccinated with a killed-virus vaccine developed high levels of neutralizing antibody and were fully protected following challenge. These results indicate that DNA vaccination could be a promising alternative to the classical vaccines against RSV in cattle and could therefore open perspectives for vaccinating young infants.     

A novel single-dose dengue subunit vaccine induces memory immune responses

To protect against dengue viral infection, a novel lipidated dengue subunit vaccine was rationally designed to contain the consensus amino acid sequences derived from four serotypes of dengue viruses. We found that the lipidated consensus dengue virus envelope protein domain III (LcED III) is capable of activating antigen-presenting cells and enhancing cellular and humoral immune responses. A single-dose of LcED III immunization in mice without extra adjuvant formulation is sufficient to elicit neutralizing antibodies against all four serotypes of dengue viruses. In addition, strong memory responses were elicited in mice immunized with a single-dose of LcED III. Quick, anamnestic neutralizing antibody responses to a live dengue virus challenge were elicited at week 28 post-immunization. These results demonstrate the promising possibility of a future successful tetravalent vaccine against dengue viral infections that utilizes one-dose vaccination with LcED III.     

Harnessing endogenous miRNAs to control virus tissue tropism as a strategy for developing attenuated virus vaccines

Live attenuated vaccines remain the safest, most cost-effective intervention against viral infections. Because live vaccine strains are generated empirically and the basis for attenuation is usually ill defined, many important viruses lack an efficient live vaccine. Here, we present a general strategy for the rational design of safe and effective live vaccines that harnesses the microRNA-based gene-silencing machinery to control viral replication. Using poliovirus as a model, we demonstrate that insertion of small miRNA homology sequences into a viral genome can restrict its tissue tropism, thereby preventing pathogenicity and yielding an attenuated viral strain. Poliovirus strains engineered to become targets of neuronal-specific miRNAs lost their ability to replicate in the central nervous system, leading to significant attenuation of neurovirulence in infected animals. Importantly, these viruses retained the ability to replicate in nonneuronal tissues. As a result, these engineered miRNA-regulated viruses elicited strong protective immunity in mice without producing disease.     

High-level primary CD8(+) T-cell response to human immunodeficiency virus type 1 gag and env generated by vaccination with recombinant vesicular stomatitis viruses

We investigated the primary cellular immune responses to human immunodeficiency virus type 1 (HIV-1) Env and Gag proteins elicited by recombinant vesicular stomatitis viruses (rVSVs). The primary response to Env peaked 5 to 7 days after intraperitoneal vaccination, at which time 40% of CD8(+) cells were Env tetramer positive and activated (CD62L(Lo)). These freshly isolated cells actively lysed target cells pulsed with the p18-I10 peptide and secreted gamma interferon and tumor necrosis factor alpha after stimulation with the Env p18-I10 peptide. The primary response to Env elicited by rVSVs was sixfold higher than that elicited by recombinant vaccinia viruses (rVVs) at 5 days postvaccination. An intranasal route of vaccination with VSV-Env also elicited a strong primary response to Env. The primary immune response to Gag elicited by rVSV peaked 7 days after vaccination, at which time 3% of CD8(+) cells were Gag tetramer positive and CD62L(Lo) and functional by intracellular cytokine staining. This response was eightfold higher than that elicited by rVV expressing Gag. VSV-GagEnv, which expresses both Gag and Env from a single recombinant, also induced strong cytotoxic T-lymphocyte (CTL) responses to both Env and Gag. Our quantitative analyses illustrate the potency of the VSV vector system in CTL induction.     

Single-dose mucosal immunization with a candidate universal influenza vaccine provides rapid protection from virulent H5N1, H3N2 and H1N1 viruses

Background

The sudden emergence of novel influenza viruses is a global public health concern. Conventional influenza vaccines targeting the highly variable surface glycoproteins hemagglutinin and neuraminidase must antigenically match the emerging strain to be effective. In contrast, “universal” vaccines targeting conserved viral components could be used regardless of viral strain or subtype. Previous approaches to universal vaccination have required protracted multi-dose immunizations. Here we evaluate a single dose universal vaccine strategy using recombinant adenoviruses (rAd) expressing the conserved influenza virus antigens matrix 2 and nucleoprotein.

Methodology/Principal Findings

In BALB/c mice, administration of rAd via the intranasal route was superior to intramuscular immunization for induction of mucosal responses and for protection against highly virulent H1N1, H3N2, or H5N1 influenza virus challenge. Mucosally vaccinated mice not only survived, but had little morbidity and reduced lung virus titers. Protection was observed as early as 2 weeks post-immunization, and lasted at least 10 months, as did antibodies and lung T cells with activated phenotypes. Virus-specific IgA correlated with but was not essential for protection, as demonstrated in studies with IgA-deficient animals.

Conclusion/Significance

Mucosal administration of NP and M2-expressing rAd vectors provided rapid and lasting protection from influenza viruses in a subtype-independent manner. Such vaccines could be used in the interval between emergence of a new virus strain and availability of strain-matched vaccines against it. This strikingly effective single-dose vaccination thus represents a candidate off-the-shelf vaccine for emergency use during an influenza pandemic.     

A Mouse Model for the Evaluation of Pathogenesis and Immunity to Influenza A (H5N1) Viruses Isolated from Humans

During 1997 in Hong Kong, 18 human cases of respiratory illness, including 6 fatalities, were caused by highly pathogenic avian influenza A (H5N1) viruses. Since H5 viruses had previously been isolated only from avian species, the outbreak raised questions about the ability of these viruses to cause severe disease and death in humans. To better understand the pathogenesis and immunity to these viruses, we have used the BALB/c mouse model. Four H5N1 viruses replicated equally well in the lungs of mice without prior adaptation but differed in lethality for mice. H5N1 viruses that were highly lethal for mice were detected in multiple organs, including the brain. This is the first demonstration of an influenza A virus that replicates systemically in a mammalian species and is neurotropic without prior adaptation. The mouse model was also used to evaluate a strategy of vaccination against the highly pathogenic avian H5N1 viruses, using an inactivated vaccine prepared from nonpathogenic A/Duck/Singapore-Q/F119-3/97 (H5N3) virus that was antigenically related to the human H5N1 viruses. Mice administered vaccine intramuscularly, with or without alum, were completely protected from lethal challenge with H5N1 virus. Protection from infection was also observed in 70% of animals administered vaccine alone and 100% of mice administered vaccine with alum. The protective effect of vaccination correlated with the level of virus-specific serum antibody. These results suggests a strategy of vaccine preparedness for rapid intervention in future influenza pandemics that uses antigenically related nonpathogenic viruses as vaccine candidates.