Recombinant parainfluenza virus 5 (PIV5) expressing the influenza A virus hemagglutinin provides immunity in mice to influenza A virus challenge

A J Paramyxovirus-vectored HIV vaccine induces humoral and cellular responses in mice

Human immunodeficiency virus (HIV) infects and depletes CD4+ T-cells, resulting in Acquired Immunodeficiency Syndrome (AIDS) and death. Despite numerous clinical trials, there is no licensed HIV vaccine. The HIV envelope glycoprotein (env) is a major target for vaccine development, especially for the development of antibody-mediated protection. In this study, we used J paramyxovirus (JPV) as a viral vector to express HIV-env. We replaced the JPV small hydrophobic (SH) gene with HIV-env (rJPV-env). Intranasal rJPV-env immunization induced anti-HIV-gp120 IgG antibodies in mice. Furthermore, we examined the immunogenicity of homologous and heterologous prime/boost regimens with rJPV-env, parainfluenza virus 5 (rPIV5)-vectored HIV-env, and HIV-Gag-Env virus-like particles (VLPs). The rJPV-env/rPIV5-env heterologous prime/boost regimen induced the strongest humoral and cellular responses. Introducing a third dose of immunization, mice that received a viral-vectored prime had high levels of HIV-env-specific cellular responses, with group rJPV-env/rPIV5-env/VLP having the highest. Together, this work indicates that a heterologous combination of viral-vectored HIV-env vaccines and a HIV-Gag-Env VLP induces high levels of humoral and cellular responses against HIV in mice.

Recombinant parainfluenza virus 5 expressing clade 2.3.4.4b H5 hemagglutinin protein confers broad protection against H5Ny influenza viruses

The global circulation of clade 2.3.4.4b H5Ny highly pathogenic avian influenza viruses (HPAIVs) in poultry and wild birds, increasing mammal infections, continues to pose a public health threat and may even form a pandemic. An efficacious vaccine against H5Ny HPAIVs is crucial for emergency use and pandemic preparedness. In this study, we developed a parainfluenza virus 5 (PIV5)-based vaccine candidate expressing hemagglutinin (HA) protein of clade 2.3.4.4b H5 HPAIV, termed rPIV5-H5, and evaluated its safety and efficacy in mice and ferrets. Our results demonstrated that intranasal immunization with a single dose of rPIV5-H5 could stimulate H5-specific antibody responses, moreover, a prime-boost regimen using rPIV5-H5 stimulated robust humoral, cellular, and mucosal immune responses in mice. Challenge study showed that rPIV5-H5 prime-boost regimen provided sterile immunity against lethal clade 2.3.4.4b H5N1 virus infection in mice and ferrets. Notably, rPIV5-H5 prime-boost regimen provided protection in mice against challenge with lethal doses of heterologous clades 2.2, 2.3.2, and 2.3.4 H5N1, and clade 2.3.4.4h H5N6 viruses. These results revealed that rPIV5-H5 can elicit protective immunity against a diverse clade of highly pathogenic H5Ny virus infection in mammals, highlighting the potential of rPIV5-H5 as a pan-H5 influenza vaccine candidate for emergency use.IMPORTANCEClade 2.3.4.4b H5Ny highly pathogenic avian influenza viruses (HPAIVs) have been widely circulating in wild birds and domestic poultry all over the world, leading to infections in mammals, including humans. Here, we developed a recombinant PIV5-vectored vaccine candidate expressing the HA protein of clade 2.3.4.4b H5 virus. Intranasal immunization with rPIV5-H5 in mice induced airway mucosal IgA responses, high levels of antibodies, and robust T-cell responses. Importantly, rPIV5-H5 conferred complete protection in mice and ferrets against clade 2.3.4.4b H5N1 virus challenge, the protective immunity was extended against heterologous H5Ny viruses. Taken together, our data demonstrate that rPIV5-H5 is a promising vaccine candidate against diverse H5Ny influenza viruses in mammals.

Intranasal vaccine for Lyme disease provides protection against tick transmitted Borrelia burgdorferi beyond one year

Strategies for disease control are necessary to reduce incidence of Lyme Disease (LD) including development of safe vaccines for human use. Parainfluenza virus 5 (PIV5) vector has an excellent safety record in animals and PIV5-vectored vaccines are currently under clinical development. We constructed PIV5-vectored LD vaccine candidates expressing OspA from B. burgdorferi (OspAB31) and a chimeric protein containing sequences from B. burgdorferi and B. afzelii (OspABPBPk). Immunogenicity and vaccine efficacy were analyzed in C3H-HeN mice after prime-boost intranasal vaccination with live PIV5-OspAB31 or PIV5-OspABPBPk, subcutaneous (s.c.) vaccination with rOspAB31+Alum, and the respective controls. Mice vaccinated intranasally with live PIV5-AB31 or PIV5-ABPBPk had higher endpoint titers of serum antibody against OspAB31 at 6- and 12- months post vaccination, compared to mice vaccinated s.c. with rOspAB31. Neutralization activity of antibody was maintained up to 18-months post-immunization, with the response greater in live PIV5-delivered OspA vaccines, than that induced by s.c. rOspAB31. Challenge with infected ticks carrying 10-19 strains of B. burgdorferi performed at 4-, 9- or 15-months post-immunization showed increased breakthrough infections in mice vaccinated with s.c. rOspAB31 compared to intranasal PIV5-AB31 or PIV5-ABPBPk at 9- and 15-months, as determined by quantification of serologic antibodies to B. burgdorferi proteins as well as flaB DNA in tissues, and by visualization of motile B. burgdorferi in culture of tissues under dark field microscope. These findings indicate that immunization of mice with PIV5 delivered OspA generates immune responses that produce longer-lasting protection ( > 1 year) against tick-transmitted B. burgdorferi than a parenteral recombinant OspA vaccine.

Intranasal parainfluenza virus type 5 (PIV5)-vectored RSV vaccine is safe and immunogenic in healthy adults in a phase 1 clinical study

Respiratory syncytial virus (RSV) can lead to serious disease in infants, and no approved RSV vaccine is available for infants. This first in-human clinical trial evaluated a single dose of BLB201, a PIV5-vectored RSV vaccine administrated via intranasal route, for safety and immunogenicity in RSV-seropositive healthy adults (33 to 75 years old). No severe adverse events (SAEs) were reported. Solicited local and systemic AEs were reported by <50% of participants and were mostly mild in intensity. Vaccine virus shedding was detected in 17% of participants. Nasal RSV-specific immunoglobulin A responses were detected in 48%, the highest level observed in adults among all intranasal RSV vaccines evaluated in humans. RSV-neutralizing antibodies titers in serum rose ≥1.5-fold. Peripheral blood RSV F-specific CD4+ and CD8+ T cells increased from ≤0.06% at baseline to ≥0.26 and 0.4% after vaccination, respectively, in >93% participants. The safety and immunogenicity profile of BLB201 in RSV-seropositive adults supports the further clinical development of BLB201.

Combined intranasal and intramuscular parainfluenza 5-, simian adenovirus ChAdOx1- and poxvirus MVA-vectored vaccines induce synergistically HIV-1-specific T cells in the mucosa

Introduction

The primary goal of this work is to broaden and enhance the options for induction of protective CD8⁺ T cells against HIV-1 and respiratory pathogens.

Methods

We explored the advantages of the parainfluenza virus 5 (PIV5) vector for delivery of pathogen-derived transgenes alone and in combination with the in-human potent regimen of simian adenovirus ChAdOx1 prime-poxvirus MVA boost delivering bi-valent mosaic of HIV-1 conserved regions designated HIVconsvX.

Results

We showed in BALB/c mice that the PIV5 vector expressing the HIVconsvX immunogens could be readily incorporated with the other two vaccine modalities into a single regimen and that for specific vector combinations, mucosal CD8⁺ T-cell induction was enhanced synergistically by a combination of the intranasal and intramuscular routes of administration.

Discussion

Encouraging safety and immunogenicity data from phase 1 human trials of ChAdOx1- and MVA-vectored vaccines for HIV-1, and PIV5-vectored vaccines for SARS-CoV-2 and respiratory syncytial virus pave the way for combining these vectors for HIV-1 and other indications in humans.

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

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

Efficacy of Parainfluenza Virus 5 (PIV5)-vectored Intranasal COVID-19 Vaccine as a Single Dose Vaccine and as a Booster against SARS-CoV-2 Variants

Immunization with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines has greatly reduced coronavirus disease 2019 (COVID-19)-related deaths and hospitalizations, but waning immunity and the emergence of variants capable of immune escape indicate the need for novel SARS-CoV-2 vaccines. An intranasal parainfluenza virus 5 (PIV5)-vectored COVID-19 vaccine CVXGA1 has been proven efficacious in animal models and blocks contact transmission of SARS-CoV-2 in ferrets. CVXGA1 vaccine is currently in human clinical trials in the United States. This work investigates the immunogenicity and efficacy of CVXGA1 and other PIV5-vectored vaccines expressing additional antigen SARS-CoV-2 nucleoprotein (N) or SARS-CoV-2 variant spike (S) proteins of beta, delta, gamma, and omicron variants against homologous and heterologous challenges in hamsters. A single intranasal dose of CVXGA1 induces neutralizing antibodies against SARS-CoV-2 WA1 (ancestral), delta variant, and omicron variant and protects against both homologous and heterologous virus challenges. Compared to mRNA COVID-19 vaccine, neutralizing antibody titers induced by CVXGA1 were well-maintained over time. When administered as a boost following two doses of a mRNA COVID-19 vaccine, PIV5-vectored vaccines expressing the S protein from WA1 (CVXGA1), delta, or omicron variants generate higher levels of cross-reactive neutralizing antibodies compared to three doses of a mRNA vaccine. In addition to the S protein, the N protein provides added protection as assessed by the highest body weight gain post-challenge infection. Our data indicates that PIV5-vectored COVID-19 vaccines, such as CVXGA1, can serve as booster vaccines against emerging variants.

Characterization of parainfluenza virus 5 from diarrheic piglet highlights its zoonotic potential

Parainfluenza virus 5 (PIV5), a member of paramyxoviruses, causes respiratory and neurological infection in several animal species. Whereas information on PIV5 infection in digestive system is very scarce. Here, we successfully isolated one PIV5 strain from diarrhetic piglets. After four times plaque purification and ultracentrifugation, the paramyxovirus-like particles were observed by electron microscopy. The genome-wide phylogenetic analysis showed that the isolated strain was closely related to the PIV5 strain from a lesser panda and pigs in China. Therefore, we characterized this isolated PIV5 and found that this virus could hemagglutinate red blood cells from both guinea pigs and chickens. Further, we observed that this PIV5 could infect cell lines from various host species including pig, human, monkey, bovine, dog, cat, rabbit, hamster, and mouse, which was confirmed with the immunofluorescent assay. To evaluate the distribution of PIV5 in the field, we developed an indirect ELISA (iELISA) for the first time to detect the specific antibodies based on recombinant nucleocapsid protein. A total of 530 porcine serum samples were tested and the PIV5-positive rate was 75.7%. To our knowledge, this is the first report describing the full characterization of PIV5 strain isolated from a diarrheic piglet. The ability of this PIV5 strain to infect a wide range of mammalian cell types indicates that PIV5 can transmit across different species, providing a remarkable insight into potential zoonosis. The virus strain and iELISA developed in this study can be used to investigate the pathogenesis, epidemiology, and zoonotic potential of PIV5. This article is protected by copyright. All rights reserved.

Rescue of dual reporter-tagged parainfluenza virus 5 as tool for rapid screening of antivirals in vitro

Parainfluenza virus 5 (PIV5) belongs to the genus Orthorubulavirus in the family Paramyxoviridae. PIV5 can infect a range of mammals, but induce mild or even unobservable clinical signs in some animals, except kennel cough in dogs. It is also able to infect a variety of cell lines, but causes minimal or even invisible cytopathic effects on many cells. Sometimes, owing to neither observable cytopathic effects in vitro nor typical clinical signs in vivo, the PIV5 is not easily usable for screening antiviral drugs. To solve this issue, we used reverse genetics to recover a dual reporter-tagged recombinant PIV5 that could simultaneously express enhanced green fluorescence protein (eGFP) and NanoLuc® luciferase (NLuc) in virus-infected cells. Both reporters were genetically stable during twenty serial passages of virus in MDBK cells. The eGFP allowed us to observe virus-infected MDBK cells in real time, and moreover the NLuc made it possible to quantify the degree of viral replication for determining antiviral activity of a given drug. Subsequently, the recombinant PIV5 was used for antiviral assays on five common drugs, i.e., ribavirin, apigenin, 1-adamantylamine hydrochloride, moroxydine hydrochloride and tea polyphenol. The results showed that only the ribavirin had an anti-PIV5 effect in MDBK cells. This study proposed a novel method for rapid screening (or prescreening) of anti-PIV5 drugs.

Parainfluenza Virus 5 Priming Followed by SIV/HIV Virus-Like-Particle Boosting Induces Potent and Durable Immune Responses in Nonhuman Primates

The search for a preventive vaccine against HIV infection remains an ongoing challenge, indicating the need for novel approaches. Parainfluenza virus 5 (PIV5) is a paramyxovirus replicating in the upper airways that is not associated with any animal or human pathology. In animal models, PIV5-vectored vaccines have shown protection against influenza, RSV, and other human pathogens. Here, we generated PIV5 vaccines expressing HIV envelope (Env) and SIV Gag and administered them intranasally to macaques, followed by boosting with virus-like particles (VLPs) containing trimeric HIV Env. Moreover, we compared the immune responses generated by PIV5-SHIV prime/VLPs boost regimen in naïve vs a control group in which pre-existing immunity to the PIV5 vector was established. We demonstrate for the first time that intranasal administration of PIV5-based HIV vaccines is safe, well-tolerated and immunogenic, and that boosting with adjuvanted trimeric Env VLPs enhances humoral and cellular immune responses. The PIV5 prime/VLPs boost regimen induced robust and durable systemic and mucosal Env-specific antibody titers with functional activities including ADCC and neutralization. This regimen also induced highly polyfunctional antigen-specific T cell responses. Importantly, we show that diminished responses due to PIV5 pre-existing immunity can be overcome in part with VLP protein boosts. Overall, these results establish that PIV5-based HIV vaccine candidates are promising and warrant further investigation including moving on to primate challenge studies.

A chimeric influenza hemagglutinin delivered by parainfluenza virus 5 vector induces broadly protective immunity against genetically divergent influenza a H1 viruses in swine

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An HA-based vaccine candidate, created by DNA shuffling (HA-113), can be immunogenic when recombinant antigen is expressed by PIV5 (PIV5-113).

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Immunity induced by the PIV5-113 vaccine can protect mice against infection with 4 of 5 parental HAs used to create the vaccine.

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Immunity induced by PIV5-113 can protect pigs against infection with an influenza virus isolate that is known to be infectious in pigs.

Pigs are an important reservoir for human influenza viruses, and influenza causes significant economic loss to the swine industry. As demonstrated during the 2009 H1N1 pandemic, control of swine influenza virus infection is a critical step toward blocking emergence of human influenza virus. An effective vaccine that can induce broadly protective immunity against heterologous influenza virus strains is critically needed. In our previous studies [McCormick et al., 2015; PLoS One, 10(6):e0127649], we used molecular breeding (DNA shuffling) strategies to increase the breadth of the variable and conserved epitopes expressed within a single influenza A virus chimeric hemagglutinin (HA) protein. Chimeric HAs were constructed using parental HAs from the 2009 pandemic virus and swine influenza viruses that had a history of zoonotic transmission to humans. In the current study, we used parainfluenza virus 5 (PIV-5) as a vector to express one of these chimeric HA antigens, HA-113. Recombinant PIV-5 expressing HA-113 (PIV5-113) were rescued, and immunogenicity and protective efficacy were tested in both mouse and pig models. The results showed that PIV5-113 can protect mice and pigs against challenge with viruses expressing parental HAs. The protective immunity was extended against other genetically diversified influenza H1-expressing viruses. Our work demonstrates that PIV5-based influenza vaccines are efficacious as vaccines for pigs. The PIV5 vaccine vector and chimeric HA-113 antigen are discussed in the context of the development of universal influenza vaccines and the potential contribution of PIV5-113 as a candidate universal vaccine.

Single-Dose, Intranasal Immunization with Recombinant Parainfluenza Virus 5 Expressing Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Spike Protein Protects Mice from Fatal MERS-CoV Infection

Middle East respiratory syndrome coronavirus (MERS-CoV) can cause severe and fatal acute respiratory disease in humans and remains endemic in the Middle East since first being identified in 2012. There are currently no approved vaccines or therapies available for MERS-CoV. In this study, we evaluated parainfluenza virus 5 (PIV5)-based vaccine expressing the MERS-CoV envelope spike protein (PIV5/MERS-S) in a human DPP4 knockin C57BL/6 congenic mouse model (hDPP4 KI). Following a single-dose intranasal immunization, PIV5-MERS-S induced neutralizing antibody and robust T cell responses in hDPP4 KI mice. A single intranasal administration of 10⁴ PFU PIV5-MERS-S provided complete protection against a lethal challenge with mouse-adapted MERS-CoV (MERS_MA6.1.2) and improved virus clearance in the lung. In comparison, single-dose intramuscular immunization with 10⁶ PFU UV-inactivated MERS_MA6.1.2 mixed with Imject alum provided protection to only 25% of immunized mice. Intriguingly, an influx of eosinophils was observed only in the lungs of mice immunized with inactivated MERS-CoV, suggestive of a hypersensitivity-type response. Overall, our study indicated that PIV5-MERS-S is a promising effective vaccine candidate against MERS-CoV infection.IMPORTANCE MERS-CoV causes lethal infection in humans, and there is no vaccine. Our work demonstrates that PIV5 is a promising vector for developing a MERS vaccine. Furthermore, success of PIV5-based MERS vaccine can be employed to develop a vaccine for emerging CoVs such as SARS-CoV-2, which causes COVID-19.

The autotransporter protein BatA is a protective antigen against lethal aerosol infection with Burkholderia mallei and Burkholderia pseudomallei

BACKGROUND

Burkholderia mallei and Burkholderia pseudomallei are the causative agents of glanders and melioidosis, respectively. There is no vaccine to protect against these highly-pathogenic and intrinsically antibiotic-resistant bacteria, and there is concern regarding their use as biological warfare agents. For these reasons, B. mallei and B. pseudomallei are classified as Tier 1 organisms by the U.S. Federal Select Agent Program and the availability of effective countermeasures represents a critical unmet need.

METHODS

Vaccines (subunit and vectored) containing the surface-exposed passenger domain of the conserved Burkholderia autotransporter protein BatA were administered to BALB/c mice and the vaccinated animals were challenged with lethal doses of wild-type B. mallei and B. pseudomallei strains via the aerosol route. Mice were monitored for signs of illness for a period of up to 40 days post-challenge and tissues from surviving animals were analyzed for bacterial burden at study end-points.

RESULTS

A single dose of recombinant Parainfluenza Virus 5 (PIV5) expressing BatA provided 74% and 60% survival in mice infected with B. mallei and B. pseudomallei, respectively. Vaccination with PIV5-BatA also resulted in complete bacterial clearance from the lungs and spleen of 78% and 44% of animals surviving lethal challenge with B. pseudomallei, respectively. In contrast, all control animals vaccinated with a PIV5 construct expressing an irrelevant antigen and infected with B. pseudomallei were colonized in those tissues.

CONCLUSION

Our study indicates that the autotransporter BatA is a valuable target for developing countermeasures against B. mallei and B. pseudomallei and demonstrates the utility of the PIV5 viral vaccine delivery platform to elicit cross-protective immunity against the organisms.

Parainfluenza virus 5-vectored vaccines against human and animal infectious diseases

Parainfluenza virus 5 (PIV5), known as canine parainfluenza virus in the veterinary field, is a negative‐sense, nonsegmented, single‐stranded RNA virus belonging to the Paramyxoviridae family. Parainfluenza virus 5 is an excellent viral vector and has been used as a live vaccine for kennel cough for many years in dogs without any safety concern. It can grow to high titers in many cell types, and its genome is stable even in the presence of foreign gene insertions. So far, PIV5 has been used to develop vaccines against influenza virus, respiratory syncytial virus, rabies virus, and Mycobacterium tuberculosis, demonstrating its ability to elicit robust and protective immune responses in preclinical animal models. Parainfluenza virus 5–based vaccines can be administered intranasally, intramuscularly, or orally. Interestingly, prior exposure of PIV5 does not prevent a PIV5‐vectored vaccine from generating robust immunity, indicating that the vector can be used more than once. Here, these encouraging results are reviewed together along with discussion of the desirable advantages of the PIV5 vaccine vector to aid future vaccine design and to accelerate progression of PIV5‐based vaccines into clinical trials.

Cross-Protective Efficacy of Influenza Virus M2e Containing Virus-Like Particles Is Superior to Hemagglutinin Vaccines and Variable Depending on the Genetic Backgrounds of Mice

Influenza virus M2 extracellular domain (M2e) has been a target for developing cross-protective vaccines. However, the efficacy and immune correlates of M2e vaccination are poorly understood in the different host genetic backgrounds in comparison with influenza vaccines. We previously reported the cross-protective efficacy of virus-like particle (M2e5x VLP) vaccines containing heterologous tandem M2e repeats (M2e5x) derived from human, swine, and avian influenza viruses. In this study to gain better understanding of cross-protective influenza vaccines, we compared immunogenicity and efficacy of M2e5x VLP, H5 hemagglutinin VLP (HA VLP), and inactivated H3N2 virus (H3N2i) in wild-type strains of BALB/c and C57BL/6 mice, and CD4 and CD8 knockout (KO) mice. M2e5x VLP was superior to HA VLP in conferring cross-protection whereas H3N2i inactivated virus vaccine provided high efficacy of homologous protection. After M2e5x VLP vaccination and challenge, BALB/c mice induced higher IgG responses, lower lung viral loads, and less body weight loss when compared with those in C57BL/6 mice. M2e5x VLP but not H3N2i immune mice after primary challenges developed strong immunity against a secondary heterosubtypic virus as a model of future pandemics. M2e5x VLP and HA VLP vaccines were able to raise IgG isotypes in CD4 KO mice. T cells were found to contribute to cross-protection by playing a role in reducing lung viral loads. In conclusion, M2e5x VLP vaccination induced better cross-protection than HA VLP, and its efficacy varied depending on the genetic backgrounds of mice, supporting the important roles of T cells.

Developing a platform system for gene delivery: amplifying virus-like particles (AVLP) as an influenza vaccine

Delivery of a gene of interest to target cells is highly desirable for translational medicine, such as gene therapy, regenerative medicine, vaccine development, and studies of gene function. Parainfluenza virus 5 (PIV5), a paramyxovirus with a negative-sense RNA genome, normally infects cells without causing obvious cytopathic effect, and it can infect many cell types. To exploit these features of PIV5, we established a system generating self-amplifying, virus-like particles (AVLP). Using enhanced green fluorescent protein (EGFP) as a reporter, AVLP encoding EGFP (AVLP–EGFP) successfully delivered and expressed the EGFP gene in primary human cells, including stem cells, airway epithelial cells, monocytes, and T cells. To demonstrate the application of this system for vaccine development, we generated AVLPs to express the HA and M1 antigens from the influenza A virus strain H5N1 (AVLP–H5 and AVLP–M1H5). Immunization of mice with AVLP–H5 and AVLP–M1H5 generated robust antibody and cellular immune responses. Vaccination with a single dose of AVLP–H5 and M1H5 completely protected mice against lethal H5N1 challenge, suggesting that the AVLP-based system is a promising platform for delivery of desirable genes.

An ‘imitation virus’ can be used to deliver genetic material to target cells, with farreaching potential for medical application. The capacity to safely and affordably introduce genes into cells is highly-sought. A team led by the University of Georgia’s Biao He created a protein shell using parainfluenza virus 5 proteins, with the resultant particles possessing the ability to infect multiple types of cell and deliver desired genetic material. The team proved the utility of their system by using it to express immunity-promoting components of avian influenza virus in live mice—successfully vaccinating the animals, and enabling them to survive a subsequent lethal infection. His group also showed that their system is also able to deliver and express genes in human cells, prompting further research into this useful tool.

Vaccination with Recombinant Parainfluenza Virus 5 Expressing Neuraminidase Protects against Homologous and Heterologous Influenza Virus Challenge

Seasonal human influenza virus continues to cause morbidity and mortality annually, and highly pathogenic avian influenza (HPAI) viruses along with other emerging influenza viruses continue to pose pandemic threats. Vaccination is considered the most effective measure for controlling influenza; however, current strategies rely on a precise vaccine match with currently circulating virus strains for efficacy, requiring constant surveillance and regular development of matched vaccines. Current vaccines focus on eliciting specific antibody responses against the hemagglutinin (HA) surface glycoprotein; however, the diversity of HAs across species and antigenic drift of circulating strains enable the evasion of virus-inhibiting antibody responses, resulting in vaccine failure. The neuraminidase (NA) surface glycoprotein, while diverse, has a conserved enzymatic site and presents an appealing target for priming broadly effective antibody responses. Here we show that vaccination with parainfluenza virus 5 (PIV5), a promising live viral vector expressing NA from avian (H5N1) or pandemic (H1N1) influenza virus, elicited NA-specific antibody and T cell responses, which conferred protection against homologous and heterologous influenza virus challenges. Vaccination with PIV5-N1 NA provided cross-protection against challenge with a heterosubtypic (H3N2) virus. Experiments using antibody transfer indicate that antibodies to NA have an important role in protection. These findings indicate that PIV5 expressing NA may be effective as a broadly protective vaccine against seasonal influenza and emerging pandemic threats.IMPORTANCE Seasonal influenza viruses cause considerable morbidity and mortality annually, while emerging viruses pose potential pandemic threats. Currently licensed influenza virus vaccines rely on the antigenic match of hemagglutinin (HA) for vaccine strain selection, and most vaccines rely on HA inhibition titers to determine efficacy, despite the growing awareness of the contribution of neuraminidase (NA) to influenza virus vaccine efficacy. Although NA is immunologically subdominant to HA, and clinical studies have shown variable NA responses to vaccination, in this study, we show that vaccination with a parainfluenza virus 5 recombinant vaccine candidate expressing NA (PIV5-NA) from a pandemic influenza (pdmH1N1) virus or highly pathogenic avian influenza (H5N1) virus elicits robust, cross-reactive protection from influenza virus infection in two animal models. New vaccination strategies incorporating NA, including PIV5-NA, could improve seasonal influenza virus vaccine efficacy and provide protection against emerging influenza viruses.

Parainfluenza Virus 5 Expressing Wild-Type or Prefusion Respiratory Syncytial Virus (RSV) Fusion Protein Protects Mice and Cotton Rats from RSV Challenge

Human respiratory syncytial virus (RSV) is the leading cause of pediatric bronchiolitis and hospitalizations. RSV can also cause severe complications in elderly and immunocompromised individuals. There is no licensed vaccine. We previously generated a parainfluenza virus 5 (PIV5)-vectored vaccine candidate expressing the RSV fusion protein (F) that was immunogenic and protective in mice. In this work, our goal was to improve the original vaccine candidate by modifying the PIV5 vector or by modifying the RSV F antigen. We previously demonstrated that insertion of a foreign gene at the PIV5 small hydrophobic (SH)-hemagglutinin-neuraminidase (HN) junction or deletion of PIV5 SH increased vaccine efficacy. Additionally, other groups have demonstrated that antibodies against the prefusion conformation of RSV F have more potent neutralizing activity than antibodies against the postfusion conformation. Therefore, to improve on our previously developed vaccine candidate, we inserted RSV F at the PIV5 SH-HN gene junction or used RSV F to replace PIV5 SH. We also engineered PIV5 to express a prefusion-stabilized F mutant. The candidates were tested in BALB/c mice via the intranasal route and induced both humoral and cell-mediated immunity. They also protected against RSV infection in the mouse lung. When they were administered intranasally or subcutaneously in cotton rats, the candidates were highly immunogenic and reduced RSV loads in both the upper and lower respiratory tracts. PIV5-RSV F was equally protective when administered intranasally or subcutaneously. In all cases, the prefusion F mutant did not induce higher neutralizing antibody titers than wild-type F. These results show that antibodies against both pre- and postfusion F are important for neutralizing RSV and should be considered when designing a vectored RSV vaccine. The findings also that indicate PIV5-RSV F may be administered subcutaneously, which is the preferred route for vaccinating infants, who may develop nasal congestion as a result of intranasal vaccination.IMPORTANCE Despite decades of research, human respiratory syncytial virus (RSV) is still a major health concern for which there is no vaccine. A parainfluenza virus 5-vectored vaccine expressing the native RSV fusion protein (F) has previously been shown to confer robust immunity against RSV infection in mice, cotton rats, and nonhuman primates. To improve our previous vaccine candidate, we developed four new candidates that incorporate modifications to the PIV5 backbone, replace native RSV F with a prefusion-stabilized RSV F mutant, or combine both RSV F and PIV5 backbone modifications. In this work, we characterized the new vaccine candidates and tested their efficacies in both murine and cotton rat models of RSV infection. Most importantly, we found that PIV5-based RSV vaccine candidates were efficacious in preventing lower respiratory tract infection as well as in reducing the nasal viral load when administered via the subcutaneous route.

Genetic Stability of Parainfluenza Virus 5-Vectored Human Respiratory Syncytial Virus Vaccine Candidates after In Vitro and In Vivo Passage

Human respiratory syncytial virus (RSV) is the leading etiologic agent of lower respiratory tract infections in children, but no licensed vaccine exists. Previously, we developed two parainfluenza virus 5 (PIV5)-based RSV vaccine candidates that protect mice against RSV challenge. PIV5 was engineered to express either the RSV fusion protein (F) or the RSV major attachment glycoprotein (G) between the hemagglutinin-neuraminidase (HN) and RNA-dependent RNA polymerase (L) genes of the PIV5 genome [PIV5-RSV-F (HN-L) and PIV5-RSV-G (HN-L), respectively]. To investigate the stability of the vaccine candidates in vitro, they were passaged in Vero cells at high and low multiplicities of infection (MOIs) for 11 generations and the genome sequences, growth kinetics, and protein expression of the resulting viruses were compared with those of the parent viruses. Sporadic mutations were detected in the consensus sequences of the viruses after high-MOI passages, and mutation rates increased under low-MOI-passage conditions. None of the mutations abolished antigen expression. Increased numbers of mutations correlated with increased growth rates in vitro, indicating that the viruses evolved through the course of serial passages. We also examined the in vivo stability of the vaccine candidates after a single passage in African green monkeys. No mutations were detected in the consensus sequences of viruses collected from the bronchoalveolar lavage (BAL) fluid of the animals. In vivo, mutations in RSV G and PIV5 L were found in individual isolates of PIV5-RSV-G (HN-L), but plaque isolates of PIV5-RSV-F (HN-L) had no mutations. To improve upon the PIV5-RSV-F (HN-L) candidate, additional vaccine candidates were generated in which the gene for RSV F was inserted into earlier positions in the PIV5 genome. These insertions did not negatively impact the sequence stability of the vaccine candidates. The results suggest that the RSV F and G gene insertions are stable in the PIV5 genome. However, the function of the foreign gene insertion may need to be considered when designing PIV5-based vaccines.IMPORTANCE The genetic stability of live viral vaccines is important for safety and efficacy. PIV5 is a promising live viral vector and has been used to develop vaccines. In this work, we examined the genetic stability of a PIV5-based RSV vaccine in vitro and in vivo We found that insertions of foreign genes, such as the RSV F and G genes, were stably maintained in the PIV5 genome and there was no mutation that abolished the expression of RSV F or G. Interestingly, the function of the inserted gene may have an impact on PIV5 genome stability.

A Single-Dose Recombinant Parainfluenza Virus 5-Vectored Vaccine Expressing Respiratory Syncytial Virus (RSV) F or G Protein Protected Cotton Rats and African Green Monkeys from RSV Challenge

Human respiratory syncytial virus (RSV) is a common cause of severe respiratory disease among infants, immunocompromised individuals, and the elderly. No licensed vaccine is currently available. In this study, we evaluated two parainfluenza virus 5 (PIV5)-vectored vaccines expressing RSV F (PIV5/F) or G (PIV5/G) protein in the cotton rat and African green monkey models for their replication, immunogenicity, and efficacy of protection against RSV challenge. Following a single intranasal inoculation, both animal species shed the vaccine viruses for a limited time but without noticeable clinical symptoms. In cotton rats, the vaccines elicited RSV F- or G-specific serum antibodies and conferred complete lung protection against RSV challenge at doses as low as 10³ PFU. Neither vaccine produced the enhanced lung pathology observed in animals immunized with formalin-inactivated RSV. In African green monkeys, vaccine-induced serum and mucosal antibody responses were readily detected, as well. PIV5/F provided nearly complete protection against RSV infection in the upper and lower respiratory tract at a dose of 10⁶ PFU of vaccine. At the same dose levels, PIV5/G was less efficacious. Both PIV5/F and PIV5/G were also able to boost neutralization titers in RSV-preexposed African green monkeys. Overall, our data indicated that PIV5/F is a promising RSV vaccine candidate.IMPORTANCE A safe and efficacious respiratory syncytial virus (RSV) vaccine remains elusive. We tested the recombinant parainfluenza virus 5 (PIV5) vectors expressing RSV glycoproteins for their immunogenicity and protective efficacy in cotton rats and African green monkeys, which are among the best available animal models to study RSV infection. In both species, a single dose of intranasal immunization with PIV5-vectored vaccines was able to produce systemic and local immunity and to protect animals from RSV challenge. The vaccines could also boost RSV neutralization antibody titers in African green monkeys that had been infected previously. Our data suggest that PIV5-vectored vaccines could potentially protect both the pediatric and elderly populations and support continued development of the vector platform.

Allergy Vaccines Using a Mycobacterium-Secreted Antigen, Ag85B, and an IL-4 Antagonist

In recent decades, the prevalence of allergic diseases, including bronchial asthma, airway hypersensitivity, hay fever, and atopic dermatitis, has been increasing in the industrialized world, and effective treatments probably require manipulating the inflammatory response to pathogenic allergens. T helper (Th) 2 cells are thought to play a crucial role in the initiation, progression, and persistence of allergic responses in association with production of interleukin (IL)-4, IL-5, and IL-13. Therefore, a strategy of a shift from Th2- to Th1-type immune response may be valuable in the prophylaxis and management of allergic diseases. It is also necessary to develop prophylactic and therapeutic treatment that induces homeostatic functions in the multifaceted allergic environment, because various factors including innate and adaptive immunity, mucosal immune response, and functional and structural maintenance of local tissue might be involved in the pathogenesis of allergic disorders. We review herein recent findings related to the curative effect for mouse models of asthma and atopic dermatitis using DNA-, virus-, and protein-based vaccines of a Mycobacterium secretion antigen, Ag85B, and a plasmid encoding cDNA of antagonistic IL-4 mutant.

Viral vector-based influenza vaccines

Antigenic drift of seasonal influenza viruses and the occasional introduction of influenza viruses of novel subtypes into the human population complicate the timely production of effective vaccines that antigenically match the virus strains that cause epidemic or pandemic outbreaks. The development of game-changing vaccines that induce broadly protective immunity against a wide variety of influenza viruses is an unmet need, in which recombinant viral vectors may provide. Use of viral vectors allows the delivery of any influenza virus antigen, or derivative thereof, to the immune system, resulting in the optimal induction of virus-specific B- and T-cell responses against this antigen of choice. This systematic review discusses results obtained with vectored influenza virus vaccines and advantages and disadvantages of the currently available viral vectors.

Efficacy of parainfluenza virus 5 (PIV5)-based tuberculosis vaccines in mice

Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), is an important human pathogen. Bacillus Calmette-Guérin (BCG), a live, attenuated variant of Mycobacterium bovis, is currently the only available TB vaccine despite its low efficacy against the infectious pulmonary form of the disease in adults. Thus, a more-effective TB vaccine is needed. Parainfluenza virus 5 (PIV5), a paramyxovirus, has several characteristics that make it an attractive vaccine vector. It is safe, inexpensive to produce, and has been previously shown to be efficacious as the backbone of vaccines for influenza, rabies, and respiratory syncytial virus. In this work, recombinant PIV5 expressing M. tuberculosis antigens 85A (PIV5-85A) and 85B (PIV5-85B) have been generated and their immunogenicity and protective efficacy evaluated in a mouse aerosol infection model. In a long-term protection study, a single dose of PIV5-85A was found to be most effective in reducing M. tuberculosis colony forming units (CFU) in lungs when compared to unvaccinated, whereas the BCG vaccinated animals had similar numbers of CFUs to unvaccinated animals. BCG-prime followed by a PIV5-85A or PIV5-85B boost produced better outcomes highlighted by close to three-log units lower lung CFUs compared to PBS. The results indicate that PIV5-based M. tuberculosis vaccines are promising candidates for further development.

In ovo and in vitro susceptibility of American alligators (Alligator mississippiensis) to avian influenza virus infection

Avian influenza has emerged as one of the most ubiquitous viruses within our biosphere. Wild aquatic birds are believed to be the primary reservoir of all influenza viruses; however, the spillover of H5N1 highly pathogenic avian influenza (HPAI) and the recent swine-origin pandemic H1N1 viruses have sparked increased interest in identifying and understanding which and how many species can be infected. Moreover, novel influenza virus sequences were recently isolated from New World bats. Crocodilians have a slow rate of molecular evolution and are the sister group to birds; thus they are a logical reptilian group to explore susceptibility to influenza virus infection and they provide a link between birds and mammals. A primary American alligator (Alligator mississippiensis) cell line, and embryos, were infected with four, low pathogenic avian influenza (LPAI) strains to assess susceptibility to infection. Embryonated alligator eggs supported virus replication, as evidenced by the influenza virus M gene and infectious virus detected in allantoic fluid and by virus antigen staining in embryo tissues. Primary alligator cells were also inoculated with the LPAI viruses and showed susceptibility based upon antigen staining; however, the requirement for trypsin to support replication in cell culture limited replication. To assess influenza virus replication in culture, primary alligator cells were inoculated with H1N1 human influenza or H5N1 HPAI viruses that replicate independent of trypsin. Both viruses replicated efficiently in culture, even at the 30 C temperature preferred by the alligator cells. This research demonstrates the ability of wild-type influenza viruses to infect and replicate within two crocodilian substrates and suggests the need for further research to assess crocodilians as a species potentially susceptible to influenza virus infection.

Regulation of Viral RNA Synthesis by the V Protein of Parainfluenza Virus 5

Paramyxoviruses include many important animal and human pathogens. The genome of parainfluenza virus 5 (PIV5), a prototypical paramyxovirus, encodes a V protein that inhibits viral RNA synthesis. In this work, the mechanism of inhibition was investigated. Using mutational analysis and a minigenome system, we identified regions in the N and C termini of the V protein that inhibit viral RNA synthesis: one at the very N terminus of V and the second at the C terminus of V. Furthermore, we determined that residues L16 and I17 are critical for the inhibitory function of the N-terminal region of the V protein. Both regions interact with the nucleocapsid protein (NP), an essential component of the viral RNA genome complex (RNP). Mutations at L16 and I17 abolished the interaction between NP and the N-terminal domain of V. This suggests that the interaction between NP and the N-terminal domain plays a critical role in V inhibition of viral RNA synthesis by the N-terminal domain. Both the N- and C-terminal regions inhibited viral RNA replication. The C terminus inhibited viral RNA transcription, while the N-terminal domain enhanced viral RNA transcription, suggesting that the two domains affect viral RNA through different mechanisms. Interestingly, V also inhibited the synthesis of the RNA of other paramyxoviruses, such as Nipah virus (NiV), human parainfluenza virus 3 (HPIV3), measles virus (MeV), mumps virus (MuV), and respiratory syncytial virus (RSV). This suggests that a common host factor may be involved in the replication of these paramyxoviruses.

IMPORTANCE

We identified two regions of the V protein that interact with NP and determined that one of these regions enhances viral RNA transcription via its interaction with NP. Our data suggest that a common host factor may be involved in the regulation of paramyxovirus replication and could be a target for broad antiviral drug development. Understanding the regulation of paramyxovirus replication will enable the rational design of vaccines and potential antiviral drugs.

Efficacy of a parainfluenza virus 5 (PIV5)-based H7N9 vaccine in mice and guinea pigs: antibody titer towards HA was not a good indicator for protection

H7N9 has caused fatal infections in humans. A safe and effective vaccine is the best way to prevent large-scale outbreaks in the human population. Parainfluenza virus 5 (PIV5), an avirulent paramyxovirus, is a promising vaccine vector. In this work, we generated a recombinant PIV5 expressing the HA gene of H7N9 (PIV5-H7) and tested its efficacy against infection with influenza virus A/Anhui/1/2013 (H7N9) in mice and guinea pigs. PIV5-H7 protected the mice against lethal H7N9 challenge. Interestingly, the protection did not require antibody since PIV5-H7 protected JhD mice that do not produce antibody against lethal H7N9 challenge. Furthermore, transfer of anti-H7 serum did not protect mice against H7N9 challenge. PIV5-H7 generated high HAI titers in guinea pigs, however it did not protect against H7N9 infection or transmission. Intriguingly, immunization of guinea pigs with PIV5-H7 and PIV5 expressing NP of influenza A virus H5N1 (PIV5-NP) conferred protection against H7N9 infection and transmission. Thus, we have obtained a H7N9 vaccine that protected both mice and guinea pigs against lethal H7N9 challenge and infection respectively.

Parainfluenza virus 5 expressing the G protein of rabies virus protects mice after rabies virus infection

Rabies remains a major public health threat around the world. Once symptoms appear, there is no effective treatment to prevent death. In this work, we tested a recombinant parainfluenza virus 5 (PIV5) strain expressing the glycoprotein (G) of rabies (PIV5-G) as a therapy for rabies virus infection: we have found that PIV5-G protected mice as late as 6 days after rabies virus infection. PIV5-G is a promising vaccine for prevention and treatment of rabies virus infection.

RNA-based viral vectors

The advent of reverse genetic approaches to manipulate the genomes of both positive (+) and negative (-) sense RNA viruses allowed researchers to harness these genomes for basic research. Manipulation of positive sense RNA virus genomes occurred first largely because infectious RNA could be transcribed directly from cDNA versions of the RNA genomes. Manipulation of negative strand RNA virus genomes rapidly followed as more sophisticated approaches to provide RNA-dependent RNA polymerase complexes coupled with negative-strand RNA templates were developed. These advances have driven an explosion of RNA virus vaccine vector development. That is, development of approaches to exploit the basic replication and expression strategies of RNA viruses to produce vaccine antigens that have been engineered into their genomes. This study has led to significant preclinical testing of many RNA virus vectors against a wide range of pathogens as well as cancer targets. Multiple RNA virus vectors have advanced through preclinical testing to human clinical evaluation. This review will focus on RNA virus vectors designed to express heterologous genes that are packaged into viral particles and have progressed to clinical testing.

Virus-vectored influenza virus vaccines

Despite the availability of an inactivated vaccine that has been licensed for >50 years, the influenza virus continues to cause morbidity and mortality worldwide. Constant evolution of circulating influenza virus strains and the emergence of new strains diminishes the effectiveness of annual vaccines that rely on a match with circulating influenza strains. Thus, there is a continued need for new, efficacious vaccines conferring cross-clade protection to avoid the need for biannual reformulation of seasonal influenza vaccines. Recombinant virus-vectored vaccines are an appealing alternative to classical inactivated vaccines because virus vectors enable native expression of influenza antigens, even from virulent influenza viruses, while expressed in the context of the vector that can improve immunogenicity. In addition, a vectored vaccine often enables delivery of the vaccine to sites of inductive immunity such as the respiratory tract enabling protection from influenza virus infection. Moreover, the ability to readily manipulate virus vectors to produce novel influenza vaccines may provide the quickest path toward a universal vaccine protecting against all influenza viruses. This review will discuss experimental virus-vectored vaccines for use in humans, comparing them to licensed vaccines and the hurdles faced for licensure of these next-generation influenza virus vaccines.

Vero/BC-F: an efficient packaging cell line stably expressing F protein to generate single round-infectious human parainfluenza virus type 2 vector

A stable packaging cell line (Vero/BC-F) constitutively expressing fusion (F) protein of the human parainfluenza virus type 2 (hPIV2) was established for production of the F-defective and single round-infectious hPIV2 vector in a strategy for recombinant vaccine development. The F gene expression has not evoked cytostatic or cytotoxic effects on the Vero/BC-F cells and the F protein was physiologically active to induce syncytial formation with giant polykaryocytes when transfected with a plasmid expressing hPIV2 hemagglutinin-neuraminidase (HN). Transduction of the F-defective replicon RNA into the Vero/BC-F cells led to the release of the infectious particles that packaged the replicon RNA (named as hPIV2ΔF) without detectable mutations, limiting the infectivity to a single round. The maximal titer of the hPIV2ΔF was 6.0 × 10(8) median tissue culture infections dose per ml. The influenza A virus M2 gene was inserted into hPIV2ΔF, and the M2 protein was found to be highly expressed in a human lung cancer cell line after transduction. Furthermore, in vivo airway infection experiments revealed that the hPIV2ΔF was capable of delivering transgenes to hamster tracheal cells. Thus, non-transmissible or single round-infectious hPIV2 vector will be potentially applicable to human gene therapy or recombinant vaccine development.

The neutralizing capacity of antibodies elicited by parainfluenza virus infection of African Green Monkeys is dependent on complement

The African Green Monkey (AGM) model was used to analyze the role of complement in neutralization of parainfluenza virus. Parainfluenza virus 5 (PIV5) and human parainfluenza virus type 2 were effectively neutralized in vitro by naïve AGM sera, but neutralizing capacity was lost by heat-inactivation. The mechanism of neutralization involved formation of massive aggregates, with no evidence of virion lysis. Following inoculation of the respiratory tract with a PIV5 vector expressing HIV gp160, AGM produced high levels of serum and tracheal antibodies against gp120 and the viral F and HN proteins. However, in the absence of complement these anti-PIV5 antibodies had very poor neutralizing capacity. Virions showed extensive deposition of IgG and C1q with post- but not pre-immune sera. These results highlight the importance of complement in the initial antibody response to parainfluenza viruses, with implications for understanding infant immune responses and design of vaccine strategies for these pediatric pathogens.

Characterization in vitro and in vivo of a novel porcine parainfluenza virus 5 isolate in Korea

A novel porcine parainfluenza 5 (pPIV5), KNU-11, in the genus Rubulavirus of the subfamily Paramyxovirinae, was isolated from the lung of a piglet in Korea in 2011. To understand the importance of this virus as an infectious agent, in vitro and in vivo characteristics of KNU-11 virus was investigated. KNU-11 was remarkably cytopathogenic, showing distinct cell rounding and clumping evident in porcine alveolar macrophage (PAM), porcine kidney (PK-15), and swine testicle (ST) cells within 12h postinfection and capable of hemagglutinating guinea pig red blood cells. Interestingly, this cytopathology was found to be absent in cell lines from other mammalian species. To evaluate the in vitro immunity of the pPIV5 isolate, we sought to explore alteration of inflammatory cytokine and chemokine expression in PAM cells infected with KNU-11 by using quantitative real-time RT-PCR. Most cytokine and chemokine genes including type 1 interferons (IFN-α/β) and IFN-related antiviral genes were found to be significantly elevated in KNU-11 virus-infected PAM cells. A serum neutralization test-based serosurvey demonstrated that neutralizing antibodies against KNU-11 are readily detected in domestic swine populations, suggesting high prevalence of pPIV5 in Korean pig farms. Animal studies showed that KNU-11 fails to establish an acute respiratory illness, indicating that pPIV5 is non- or very mildly pathogenic to pigs.

Intranasally administered antigen 85B gene vaccine in non-replicating human Parainfluenza type 2 virus vector ameliorates mouse atopic dermatitis

Atopic dermatitis (AD) is a refractory and recurrent inflammatory skin disease. Various factors including heredity, environmental agent, innate and acquired immunity, and skin barrier function participate in the pathogenesis of AD. T -helper (Th) 2-dominant immunological milieu has been suggested in the acute phase of AD. Antigen 85B (Ag85B) is a 30-kDa secretory protein well conserved in Mycobacterium species. Ag85B has strong Th1-type cytokine inducing activity, and is expected to ameliorate Th2 condition in allergic disease. To perform Ag85B function in vivo, effective and less invasive vaccination method is required. Recently, we have established a novel functional virus vector; recombinant human parainfluenza type 2 virus vector (rhPIV2): highly expressive, replication-deficient, and very low-pathogenic vector. In this study, we investigated the efficacy of rhPIV2 engineered to express Ag85B (rhPIV2/Ag85B) in a mouse AD model induced by repeated oxazolone (OX) challenge. Ear swelling, dermal cell infiltrations and serum IgE level were significantly suppressed in the rhPIV2/Ag85B treated mouse group accompanied with elevated IFN-γ and IL-10 mRNA expressions, and suppressed IL-4, TNF-α and MIP-2 mRNA expressions. The treated mice showed no clinical symptom of croup or systemic adverse reactions. The respiratory tract epithelium captured rhPIV2 effectively without remarkable cytotoxic effects. These results suggested that rhPIV2/Ag85B might be a potent therapeutic tool to control allergic disorders.

Efficacy of parainfluenza virus 5 mutants expressing hemagglutinin from H5N1 influenza A virus in mice

Parainfluenza virus 5 (PIV5) is a promising viral vector for vaccine development. PIV5 is safe, stable, efficacious, cost-effective to produce and, most interestingly, it overcomes preexisting antivector immunity. We have recently reported that PIV5 expressing the hemagglutinin (HA) from highly pathogenic avian influenza (HPAI) virus H5N1 (PIV5-H5) provides sterilizing immunity against lethal doses of HPAI H5N1 infection in mice. It is thought that induction of apoptosis can lead to enhanced antigen presentation. Previously, we have shown that deleting the SH gene and the conserved C terminus of the V gene in PIV5 results in mutant viruses (PIV5ΔSH and PIV5VΔC) that enhance induction of apoptosis. In this study, we inserted the HA gene of H5N1 into PIV5ΔSH (PIV5ΔSH-H5) or PIV5VΔC (PIV5VΔC-H5) and compared their efficacies as vaccine candidates to PIV5-H5. We have found that PIV5ΔSH-H5 induced the highest levels of anti-HA antibodies, the strongest T cell responses, and the best protection against an H5N1 lethal challenge in mice. These results suggest that PIV5ΔSH is a better vaccine vector than wild-type PIV5.

Influence of antigen insertion site and vector dose on immunogenicity and protective capacity in Sendai virus-based human parainfluenza virus type 3 vaccines

Recombinant Sendai virus (rSeV) was used as a live, attenuated vaccine vector for intranasal inoculation and mucosal expression of the hemagglutinin-neuraminidase (HN) surface glycoprotein of human parainfluenza virus type 3 (HPIV3). Two vaccine candidates rSeV-HPIV3HN(P-M) and rSeV-HPIV3(F-HN) were constructed in which the HPIV3 HN open reading frame and an additional gene junction was inserted in the P-M and F-HN gene junctions of rSeV, respectively. The rSeV-HPIV3HN(P-M) virus was attenuated compared to rSeV-HPIV3(F-HN) in LLC-MK2 cells, and yet both vaccine candidates grew to similar extents in NHBE cells and in the respiratory tracts of cotton rats. These results suggest that in vitro vector growth in NHBE cells more accurately predicts virus yield in cotton rats than does growth in LLC-MK2 cells. Both vaccine vectors elicited high levels of serum neutralizing antibodies and conferred protection from HPIV3 challenge in cotton rats. Compared to vaccination with a high dose (2,000,000 PFU), intranasal inoculation with a low dose (200 PFU) resulted in a 10-fold decrease in vector growth in the nasal cavity and trachea and a 50-fold decrease in the lungs. However, low-dose vaccination resulted in only modest decreases in anti-HPIV3 antibodies in sera and was sufficient to confer complete protection from HPIV3 challenge. Varying the HPIV3 antigen insertion site and vector dose allowed fine-tuning of the in vivo growth and immunogenicity of rSeV-based vaccines, but all four vaccination strategies tested resulted in complete protection from HPIV3 challenge. These results highlight the versatility of the rSeV platform for developing intranasally administered respiratory virus vaccines.

Single-dose vaccination of a recombinant parainfluenza virus 5 expressing NP from H5N1 virus provides broad immunity against influenza A viruses

Influenza viruses often evade host immunity via antigenic drift and shift despite previous influenza virus infection and/or vaccination. Vaccines that match circulating virus strains are needed for optimal protection. Development of a universal influenza virus vaccine providing broadly cross-protective immunity will be of great importance. The nucleoprotein (NP) of influenza A virus is highly conserved among all strains of influenza A viruses and has been explored as an antigen for developing a universal influenza virus vaccine. In this work, we generated a recombinant parainfluenza virus 5 (PIV5) containing NP from H5N1 (A/Vietnam/1203/2004), a highly pathogenic avian influenza (HPAI) virus, between HN and L (PIV5-NP-HN/L) and tested its efficacy. PIV5-NP-HN/L induced humoral and T cell responses in mice. A single inoculation of PIV5-NP-HN/L provided complete protection against lethal heterosubtypic H1N1 challenge and 50% protection against lethal H5N1 HPAI virus challenge. To improve efficacy, NP was inserted into different locations within the PIV5 genome. Recombinant PIV5 containing NP between F and SH (PIV5-NP-F/SH) or between SH and HN (PIV5-NP-SH/HN) provided better protection against H5N1 HPAI virus challenge than did PIV5-NP-HN/L. These results suggest that PIV5 expressing NP from H5N1 has the potential to be utilized as a universal influenza virus vaccine.

Experimental vaccines against potentially pandemic and highly pathogenic avian influenza viruses

Influenza A viruses continue to emerge and re-emerge, causing outbreaks, epidemics and occasionally pandemics. While the influenza vaccines licensed for public use are generally effective against seasonal influenza, issues arise with production, immunogenicity, and efficacy in the case of vaccines against pandemic and emerging influenza viruses, and highly pathogenic avian influenza virus in particular. Thus, there is need of improved influenza vaccines and vaccination strategies. This review discusses advances in alternative influenza vaccines, touching briefly on licensed vaccines and vaccine antigens; then reviewing recombinant subunit vaccines, virus-like particle vaccines and DNA vaccines, with the main focus on virus-vectored vaccine approaches.

A novel rabies vaccine based on a recombinant parainfluenza virus 5 expressing rabies virus glycoprotein

Untreated rabies virus (RABV) infection leads to death. Vaccine and postexposure treatment have been effective in preventing RABV infection. However, due to cost, rabies vaccination and treatment have not been widely used in developing countries. There are 55,000 human death caused by rabies annually. An efficacious and cost-effective rabies vaccine is needed. Parainfluenza virus 5 (PIV5) is thought to contribute to kennel cough, and kennel cough vaccines containing live PIV5 have been used in dogs for many years. In this work, a PIV5-vectored rabies vaccine was tested in mice. A recombinant PIV5 encoding RABV glycoprotein (G) (rPIV5-RV-G) was administered to mice via intranasal (i.n.), intramuscular (i.m.), and oral inoculation. The vaccinated mice were challenged with a 50% lethal challenge dose (LD(50)) of RABV challenge virus standard 24 (CVS-24) intracerebrally. A single dose of 10(6) PFU of rPIV5-RV-G was sufficient for 100% protection when administered via the i.n. route. The mice vaccinated with a single dose of 10(8) PFU of rPIV5-RV-G via the i.m. route showed very robust protection (90% to 100%). Intriguingly, the mice vaccinated orally with a single dose of 10(8) PFU of rPIV5-RV-G showed a 50% survival rate, which is comparable to the 60% survival rate among mice inoculated with an attenuated rabies vaccine strain, recombinant LBNSE. This is first report of an orally effective rabies vaccine candidate in animals based on PIV5 as a vector. These results indicate that rPIV5-RV-G is an excellent candidate for a new generation of recombinant rabies vaccine for humans and animals and PIV5 is a potential vector for oral vaccines.

Evaluating a parainfluenza virus 5-based vaccine in a host with pre-existing immunity against parainfluenza virus 5

Parainfluenza virus 5 (PIV5), formerly known as simian virus 5 (SV5), is a paramyxovirus often referred to as canine parainfluenza virus (CPI) in the veterinary field. PIV5 is thought to be a contributing factor to kennel cough. Kennel cough vaccines containing live PIV5 have been used in dogs for many decades. PIV5 is not known to cause any diseases in humans or other animals. PIV5 has been used as a vector for vaccine development for humans and animals. One critical question concerning the use of PIV5 as a vector is whether prior exposure to PIV5 would prevent the use of PIV5-based vaccines. In this work, we have examined immunogenicity of a recombinant PIV5 expressing hemagglutinin (HA) of influenza A virus subtype 3 (rPIV5-H3) in dogs that were immunized against PIV5. We found that vaccination of the dogs containing neutralizing antibodies against PIV5 with rPIV5-H3 generated immunity against influenza A virus, indicting that PIV5-based vaccine is immunogenic in dogs with prior exposure. Furthermore, we have examined exposure of PIV5 in human populations. We have detected neutralizing antibody (nAb) against PIV5 in 13 out of 45 human serum samples (about 29 percent). The nAb titers in humans were lower than that in vaccinated dogs, suggesting that nAb in humans is unlikely to prevent PIV5 from being an efficacious vector in humans.

Recombinant parainfluenza virus 5 vaccine encoding the influenza virus hemagglutinin protects against H5N1 highly pathogenic avian influenza virus infection following intranasal or intramuscular vaccination of BALB/c mice

New approaches for vaccination to prevent influenza virus infection are needed. Emerging viruses, such as the H5N1 highly pathogenic avian influenza (HPAI) virus, pose not only pandemic threats but also challenges in vaccine development and production. Parainfluenza virus 5 (PIV5) is an appealing vector for vaccine development, and we have previously shown that intranasal immunization with PIV5 expressing the hemagglutinin from influenza virus was protective against influenza virus challenge (S. M. Tompkins, Y. Lin, G. P. Leser, K. A. Kramer, D. L. Haas, E. W. Howerth, J. Xu, M. J. Kennett, J. E. Durbin, R. A. Tripp, R. A. Lamb, and B. He, Virology 362:139-150, 2007). While intranasal immunization is an appealing approach, PIV5 may have the potential to be utilized in other formats, prompting us to test the efficacy of rPIV5-H5, which encodes the HA from H5N1 HPAI virus, in different vaccination schemes. In the BALB/c mouse model, a single intramuscular or intranasal immunization with a live rPIV5-H5 (ZL46) rapidly induced robust neutralizing serum antibody responses and protected against HPAI challenge, although mucosal IgA responses primed by intranasal immunization more effectively controlled virus replication in the lung. The rPIV5-H5 vaccine incorporated the H5 HA into the virion, so we tested the efficacy of an inactivated form of the vaccine. Inactivated rPIV5-H5 primed neutralizing serum antibody responses and controlled H5N1 virus replication; however, similar to other H5 antigen vaccines, it required a booster immunization to prime protective immune responses. Taken together, these results suggest that rPIV5-HA vaccines and H5-specific vaccines in particular can be utilized in multiple formats and by multiple routes of administration. This could avoid potential contraindications based on intranasal administration alone and provide opportunities for broader applications with the use of a single vaccine vector.

Recombinant parainfluenza virus 5 expressing hemagglutinin of influenza A virus H5N1 protected mice against lethal highly pathogenic avian influenza virus H5N1 challenge

A safe and effective vaccine is the best way to prevent large-scale highly pathogenic avian influenza virus (HPAI) H5N1 outbreaks in the human population. The current FDA-approved H5N1 vaccine has serious limitations. A more efficacious H5N1 vaccine is urgently needed. Parainfluenza virus 5 (PIV5), a paramyxovirus, is not known to cause any illness in humans. PIV5 is an attractive vaccine vector. In our studies, a single dose of a live recombinant PIV5 expressing a hemagglutinin (HA) gene of H5N1 (rPIV5-H5) from the H5N1 subtype provided sterilizing immunity against lethal doses of HPAI H5N1 infection in mice. Furthermore, we have examined the effect of insertion of H5N1 HA at different locations within the PIV5 genome on the efficacy of a PIV5-based vaccine. Interestingly, insertion of H5N1 HA between the leader sequence, the de facto promoter of PIV5, and the first viral gene, nucleoprotein (NP), did not lead to a viable virus. Insertion of H5N1 HA between NP and the next gene, V/phosphorprotein (V/P), led to a virus that was defective in growth. We have found that insertion of H5N1 HA at the junction between the small hydrophobic (SH) gene and the hemagglutinin-neuraminidase (HN) gene gave the best immunity against HPAI H5N1 challenge: a dose as low as 1,000 PFU was sufficient to protect against lethal HPAI H5N1 challenge in mice. The work suggests that recombinant PIV5 expressing H5N1 HA has great potential as an HPAI H5N1 vaccine.

Comparison of differing cytopathic effects in human airway epithelium of parainfluenza virus 5 (W3A), parainfluenza virus type 3, and respiratory syncytial virus

Parainfluenza virus 5 (PIV5) infects a wide range of animals including dogs, pigs, cats, and humans; however, its association with disease in humans remains controversial. In contrast to parainfluenza virus 3 (PIV3) or respiratory syncytial virus (RSV), PIV5 is remarkably non-cytopathic in monolayer cultures of immortalized epithelial cells. To compare the cytopathology produced by these viruses in a relevant human tissue, we infected an in vitro model of human ciliated airway epithelium and measured outcomes of cytopathology. PIV5, PIV3 and, RSV all infected ciliated cells, and PIV5 and PIV3 infection was dependent on sialic acid residues. Only PIV5-infected cells formed syncytia. PIV5 infection resulted in a more rapid loss of infected cells by shedding of infected cells into the lumen. These studies revealed striking differences in cytopathology of PIV5 versus PIV3 or RSV and indicate the extent of cytopathology determined in cell-lines does not predict events in differentiated airway cells.

Parainfluenza virus 5-based vaccine vectors expressing vaccinia virus (VACV) antigens provide long-term protection in mice from lethal intranasal VACV challenge

To test the potential for parainfluenza virus 5 (PIV5)-based vectors to provide protection from vaccinia virus (VACV) infection, PIV5 was engineered to express secreted VACV L1R and B5R proteins, two important antigens for neutralization of intracellular mature (IMV) and extracellular enveloped (EEV) virions, respectively. Protection of mice from lethal intranasal VACV challenge required intranasal immunization with PIV5-L1R/B5R in a prime-boost protocol, and correlated with low VACV-induced pathology in the respiratory tract and anti-VACV neutralizing antibody. Mice immunized with PIV5-L1R/B5R showed some disease symptoms following VACV challenge such as loss of weight and hunching, but these symptoms were delayed and less severe than with unimmunized control mice. While immunization with PIV5 expressing B5R alone conferred at least some protection, the most effective immunization included the PIV5 vector expressing L1R alone or in combination with PIV5-B5R. PIV5-L1R/B5R vectors elicited protection from VACV challenge even when CD8+ cells were depleted, but not in the case of mice that were defective in B cell production. Mice were protected from VACV challenge out to at least 1.5 years after immunization with PIV5-L1R/B5R vectors, and showed significant levels of anti-VACV neutralizing antibodies. These results demonstrate the potential for PIV5-based vectors to provide long lasting protection against complex human respiratory pathogens such as VACV, but also highlight the need to understand mechanisms for the generation of strong immune responses against poorly immunogenic viral proteins.

Induction of influenza-specific mucosal immunity by an attenuated recombinant Sendai virus

BACKGROUND

Many pathogens initiate infection at the mucosal surfaces; therefore, induction of mucosal immune responses is a first level of defense against infection and is the most powerful means of protection. Although intramuscular injection is widely used for vaccination and is effective at inducing circulating antibodies, it is less effective at inducing mucosal antibodies.

METHODOLOGY/PRINCIPAL FINDINGS

Here we report a novel recombinant, attenuated Sendai virus vector (GP42-H1) in which the hemagglutinin (HA) gene of influenza A virus was introduced into the Sendai virus genome as an additional gene. Infection of CV-1 cells by GP42-H1 resulted in cell surface expression of the HA protein. Intranasal immunization of mice with 1,000 plaque forming units (pfu) of GP42-H1 induced HA-specific IgG and IgA antibodies in the blood, bronchoalveolar lavage fluid, fecal pellet extracts and saliva. The HA-specific antibody titer induced by GP42-H1 closely resembles the titer induced by sublethal infection by live influenza virus; however, in contrast to infection by influenza virus, immunization with GP42-H1 did not result in disease symptoms or the loss of body weight. In mice that were immunized with GP42-H1 and then challenged with 5LD(50) (1250 pfu) of influenza virus, no significant weight loss was observed and other visual signs of morbidity were not detected.

CONCLUSIONS

These results demonstrate that the GP42-H1 Sendai virus recombinant is able to confer full protection from lethal infection by influenza virus, supporting the conclusion that it is a safe and effective mucosal vaccine vector.

Function of the small hydrophobic protein of J paramyxovirus

At 18,954 nucleotides, the J paramyxovirus (JPV) genome is one of the largest in the family Paramyxoviridae, consisting of eight genes in the order 3'-N-P/V/C-M-F-SH-TM-G-L-5'. To study the function of novel paramyxovirus genes in JPV, a plasmid containing a full-length cDNA clone of the genome of JPV was constructed. In this study, the function of the small hydrophobic (SH) protein of JPV was examined by generating a recombinant JPV lacking the coding sequence of the SH protein (rJPVΔSH). rJPVΔSH was viable and had no growth defect in tissue culture cells. However, more tumor necrosis factor alpha (TNF-α) was produced during rJPVΔSH infection, suggesting that SH plays a role in inhibiting TNF-α production. rJPVΔSH induced more apoptosis in tissue culture cells than rJPV. Virus-induced apoptosis was inhibited by neutralizing antibody against TNF-α, suggesting that TNF-α contributes to JPV-induced apoptosis in vitro. The expression of JPV SH protein inhibited TNF-α-induced NF-κB activation in a reporter gene assay, suggesting that JPV SH protein can inhibit TNF-α signaling in vitro. Furthermore, infection of mice with rJPVΔSH induced more TNF-α expression, indicating that SH plays a role in blocking TNF-α expression in vivo.

Development of a safe and convenient neutralization assay for rapid screening of influenza HA-specific neutralizing monoclonal antibodies

The worldwide outbreak of the swine-origin 2009 H1N1 influenza A virus (IAV) and an increasing number of influenza cases caused by a highly pathogenic avian influenza (HPAI) H5N1 have accelerated the need to develop vaccines and antiviral agents against IAVs. Among various antivirals, neutralizing monoclonal antibodies (mAbs) are considered important passive therapeutics having an immediate effect against viral pathogens. Here we report a pseudovirus neutralization assay for rapid screening of neutralizing mAbs targeting hemagglutinin (HA) of H5N1 and H1N1 IAV. In this study, we generated six pseudoviruses with an HIV-1 backbone, respectively, expressing HA of four clades of H5N1 IAV and the 2009 epidemic H1N1 IAV. The resulting pseudoviruses were able to infect a variety of human and non-human cells, with 293T cells from human kidney as the most susceptible target cells. Using the established pseudovirus neutralization assay, we showed that three of ten selected mAbs specific to HA could potently neutralize infection of a pseudovirus bearing HA from the homologous IAV A/VietNam/1194/2004(H5N1) strain. This was highly consistent with the result of a microneutralization assay testing the same strain of a live IAV. Since the pseudovirus neutralization assay does not involve an infectious virus and can be performed without the requirement of a biosafety-3 laboratory, it may be applied for safe and rapid screening of neutralizing mAbs and antiviral agents targeting HA of IAVs.

Roles of the hemagglutinin of influenza A virus in viral entry and development of antiviral therapeutics and vaccines

Seasonal influenza epidemics and influenza pandemics caused by influenza A virus (IAV) has resulted in millions of deaths in the world. The development of anti-IAV vaccines and therapeutics is urgently needed for prevention and treatment of IAV infection and for controlling future influenza pandemics. Hemagglutinin (HA) of IAV plays a critical role in viral binding, fusion and entry, and contains the major neutralizing epitopes. Therefore, HA is an attractive target for developing anti-IAV drugs and vaccines. Here we have reviewed the recent progress in study of conformational changes of HA during viral fusion process and development of HA-based antiviral therapeutics and vaccines.

Engineered expression of the TLR5 ligand flagellin enhances paramyxovirus activation of human dendritic cell function

The paramyxovirus simian virus 5 (SV5) is a poor activator of human dendritic cell (DC) maturation pathways in vitro, and infected DC do not upregulate cell surface costimulatory proteins or secretion of immunomodulatory cytokines. We evaluated the hypothesis that activation of SV5-infected DC would be enhanced by engineering SV5 to express a Toll-like-receptor (TLR) ligand. To test this hypothesis, a novel virus was engineered such that the gene encoding an intracellular form of the TLR5 ligand flagellin was expressed from the genome of wild-type (WT) SV5 (SV5-flagellin). Cells infected in vitro with the flagellin-expressing virus released low levels of biologically active flagellin, which was capable of stimulating TLR5 signaling. Infection of human peripheral blood mononuclear cell-derived immature DC with SV5-flagellin resulted in enhanced levels of interleukin-6 (IL-6) and IL-12 compared to infection with DC with the parental virus, WT SV5. In contrast to cytokine induction, the flagellin-expressing virus did not appreciably increase DC surface expression of the costimulatory molecule CD80 or CD86 above the level seen with WT SV5 alone. In mixed-culture assays, DC infected with the flagellin-expressing virus were more effective at activating gamma interferon secretion from both CD8(+) and CD4(+) allogeneic T cells than DC infected with WT SV5. Our results with SV5-directed intracellular expression of flagellin may be applicable to other vectors or pathogenic viruses where overcoming impairment of DC activation could contribute to the development of safer and more effective vaccines.