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Petro-Turnquist E, Pekarek MJ, Weaver EA. Swine influenza A virus: challenges and novel vaccine strategies. Front Cell Infect Microbiol 2024; 14:1336013. [PMID: 38633745 PMCID: PMC11021629 DOI: 10.3389/fcimb.2024.1336013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 03/21/2024] [Indexed: 04/19/2024] Open
Abstract
Swine Influenza A Virus (IAV-S) imposes a significant impact on the pork industry and has been deemed a significant threat to global public health due to its zoonotic potential. The most effective method of preventing IAV-S is vaccination. While there are tremendous efforts to control and prevent IAV-S in vulnerable swine populations, there are considerable challenges in developing a broadly protective vaccine against IAV-S. These challenges include the consistent diversification of IAV-S, increasing the strength and breadth of adaptive immune responses elicited by vaccination, interfering maternal antibody responses, and the induction of vaccine-associated enhanced respiratory disease after vaccination. Current vaccination strategies are often not updated frequently enough to address the continuously evolving nature of IAV-S, fail to induce broadly cross-reactive responses, are susceptible to interference, may enhance respiratory disease, and can be expensive to produce. Here, we review the challenges and current status of universal IAV-S vaccine research. We also detail the current standard of licensed vaccines and their limitations in the field. Finally, we review recently described novel vaccines and vaccine platforms that may improve upon current methods of IAV-S control.
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Affiliation(s)
- Erika Petro-Turnquist
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, United States
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Matthew J. Pekarek
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, United States
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Eric A. Weaver
- Nebraska Center for Virology, University of Nebraska-Lincoln, Lincoln, NE, United States
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
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2
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Kinsley AC, Rossi G, Silk MJ, VanderWaal K. Multilayer and Multiplex Networks: An Introduction to Their Use in Veterinary Epidemiology. Front Vet Sci 2020; 7:596. [PMID: 33088828 PMCID: PMC7500177 DOI: 10.3389/fvets.2020.00596] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 07/27/2020] [Indexed: 11/13/2022] Open
Abstract
Contact network analysis has become a vital tool for conceptualizing the spread of pathogens in animal populations and is particularly useful for understanding the implications of heterogeneity in contact patterns for transmission. However, the transmission of most pathogens cannot be simplified to a single mode of transmission and, thus, a single definition of contact. In addition, host-pathogen interactions occur in a community context, with many pathogens infecting multiple host species and most hosts being infected by multiple pathogens. Multilayer networks provide a formal framework for researching host-pathogen systems in which multiple types of transmission-relevant interactions, defined as network layers, can be analyzed jointly. Here, we provide an overview of multilayer network analysis and review applications of this novel method to epidemiological research questions. We then demonstrate the use of this technique to analyze heterogeneity in direct and indirect contact patterns amongst swine farms in the United States. When contact among nodes can be defined in multiple ways, a multilayer approach can advance our ability to use networks in epidemiological research by providing an improved approach for defining epidemiologically relevant groups of interacting nodes and changing the way we identify epidemiologically important individuals such as superspreaders.
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Affiliation(s)
- Amy C Kinsley
- Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, United States
| | - Gianluigi Rossi
- Roslin Institute and Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Matthew J Silk
- Centre for Ecology and Conservation, University of Exeter Penryn Campus, Penryn, United Kingdom.,Environment and Sustainability Institute, University of Exeter, Penryn, United Kingdom
| | - Kimberly VanderWaal
- Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, United States
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Giurgea LT, Morens DM, Taubenberger JK, Memoli MJ. Influenza Neuraminidase: A Neglected Protein and Its Potential for a Better Influenza Vaccine. Vaccines (Basel) 2020; 8:vaccines8030409. [PMID: 32718039 PMCID: PMC7564061 DOI: 10.3390/vaccines8030409] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 07/14/2020] [Accepted: 07/21/2020] [Indexed: 12/22/2022] Open
Abstract
Neuraminidase (NA) is an influenza surface protein that helps to free viruses from mucin-associated decoy receptors and to facilitate budding from infected cells. Experiments have demonstrated that anti-NA antibodies protect animals against lethal influenza challenge by numerous strains, while decreasing pulmonary viral titers, symptoms, and lung lesions. Studies in humans during the influenza A/H3N2 pandemic and in healthy volunteers challenged with influenza A/H1N1 showed that anti-NA immunity reduced symptoms, nasopharyngeal viral shedding, and infection rates. Despite the benefits of anti-NA immunity, current vaccines focus on immunity against hemagglutinin and are not standardized to NA content leading to limited and variable NA immunogenicity. Purified NA has been shown to be safe and immunogenic in humans. Supplementing current vaccines with NA may be a simple strategy to improve suboptimal effectiveness. Immunity against NA is likely to be an important component of future universal influenza vaccines.
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Affiliation(s)
- Luca T. Giurgea
- LID Clinical Studies Unit, Laboratory of Infectious Diseases, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA;
- Correspondence:
| | - David M. Morens
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA;
| | - Jeffery K. Taubenberger
- Viral Pathogenesis and Evolution Section, Laboratory of Infectious Diseases, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA;
| | - Matthew J. Memoli
- LID Clinical Studies Unit, Laboratory of Infectious Diseases, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA;
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Rajão DS, Pérez DR. Universal Vaccines and Vaccine Platforms to Protect against Influenza Viruses in Humans and Agriculture. Front Microbiol 2018; 9:123. [PMID: 29467737 PMCID: PMC5808216 DOI: 10.3389/fmicb.2018.00123] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 01/18/2018] [Indexed: 01/22/2023] Open
Abstract
Influenza virus infections pose a significant threat to public health due to annual seasonal epidemics and occasional pandemics. Influenza is also associated with significant economic losses in animal production. The most effective way to prevent influenza infections is through vaccination. Current vaccine programs rely heavily on the vaccine's ability to stimulate neutralizing antibody responses to the hemagglutinin (HA) protein. One of the biggest challenges to an effective vaccination program lies on the fact that influenza viruses are ever-changing, leading to antigenic drift that results in escape from earlier immune responses. Efforts toward overcoming these challenges aim at improving the strength and/or breadth of the immune response. Novel vaccine technologies, the so-called universal vaccines, focus on stimulating better cross-protection against many or all influenza strains. However, vaccine platforms or manufacturing technologies being tested to improve vaccine efficacy are heterogeneous between different species and/or either tailored for epidemic or pandemic influenza. Here, we discuss current vaccines to protect humans and animals against influenza, highlighting challenges faced to effective and uniform novel vaccination strategies and approaches.
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Affiliation(s)
- Daniela S. Rajão
- Department of Population Health, University of Georgia, Athens, GA, United States
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Hatta Y, Boltz D, Sarawar S, Kawaoka Y, Neumann G, Bilsel P. M2SR, a novel live influenza vaccine, protects mice and ferrets against highly pathogenic avian influenza. Vaccine 2017; 35:4177-4183. [PMID: 28668565 DOI: 10.1016/j.vaccine.2017.06.039] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Revised: 06/08/2017] [Accepted: 06/12/2017] [Indexed: 11/27/2022]
Abstract
The emergence of highly pathogenic avian influenza H5N1 viruses has heightened global concern about the threat posed by pandemic influenza. To address the need for a highly effective universal influenza vaccine, we developed a novel M2-deficient single replication (M2SR) influenza vaccine virus and previously reported that it provided strong heterosubtypic protection against seasonal influenza viruses in mice. In the current study, we assessed M2SR induced protection against H5N1 influenza in mice and ferrets. Mice were intranasally inoculated with M2SR viruses containing the HA and NA from A/Vietnam/1203/2004 (M2SR H5N1) or A/California/07/2009 (M2SR H1N1). All M2SR vaccinated mice survived lethal challenge with influenza A/Vietnam/1203/2004 (H5N1), whereas 40% of mice vaccinated with recombinant H5 HA and none of the naïve controls survived. M2SR H5N1 provided sterile immunity, whereas low levels of virus were detected in the lungs of some M2SR H1N1 vaccinated mice. In contrast, recombinant H5 HA vaccinated mice and naïve controls showed systemic infection. M2SR H5N1 induced strong serum and mucosal antibody responses (IgG and IgA classes) against H5 HA, with high hemagglutination inhibition (HAI) titers. In contrast, while M2SR H1N1 elicited cross-reactive antibodies recognizing the H5 HA2 stalk region or the neuraminidase, no HAI activity against H5N1 virus was detected after M2SR H1N1 immunization. Both M2SR H5N1 and H1N1 also protected ferrets against lethal challenge with A/Vietnam/1203/2004. A prime-boost regimen provided optimal protection with no virus detected in the respiratory tract or brain after challenge. As in the mouse model, only the M2SR H5N1 vaccine induced HAI antibodies against the challenge virus in ferrets, while the M2SR H1N1 was able to provide protection without the induction of HAI antibodies. In summary, effective protection against highly pathogenic H5N1 influenza virus was provided by both homologous H5N1 M2SR and heterologous H1N1 M2SR demonstrating the cross-protective attributes of the M2SR platform.
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Affiliation(s)
| | - David Boltz
- IIT Research Institute, Chicago, IL 60616, USA
| | - Sally Sarawar
- The Biomedical Research Institute of Southern California, Oceanside, CA 92056, USA
| | - Yoshihiro Kawaoka
- Influenza Research Institute, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53711, USA; Division of Virology, Department of Microbiology and Immunology, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan; Division of Virology, Department of Special Pathogens, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan
| | - Gabriele Neumann
- Influenza Research Institute, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, WI 53711, USA
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Schmidt R, Holznagel E, Neumann B, Alex N, Sawatsky B, Enkirch T, Pfeffermann K, Kruip C, von Messling V, Wagner R. Squalene-containing licensed adjuvants enhance strain-specific antibody responses against the influenza hemagglutinin and induce subtype-specific antibodies against the neuraminidase. Vaccine 2016; 34:5329-5335. [DOI: 10.1016/j.vaccine.2016.08.082] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/22/2016] [Accepted: 08/29/2016] [Indexed: 11/24/2022]
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Esmagambetov IB, Alekseeva SV, Sayadyan KS, Shmarov MM. CURRENT APPROACHES TO UNIVERSAL VACCINE AGAINST INFLUENZA VIRUS. RUSSIAN JOURNAL OF INFECTION AND IMMUNITY 2016. [DOI: 10.15789/2220-7619-2016-2-117-132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Decorte I, Steensels M, Lambrecht B, Cay AB, De Regge N. Detection and Isolation of Swine Influenza A Virus in Spiked Oral Fluid and Samples from Individually Housed, Experimentally Infected Pigs: Potential Role of Porcine Oral Fluid in Active Influenza A Virus Surveillance in Swine. PLoS One 2015; 10:e0139586. [PMID: 26431039 PMCID: PMC4592207 DOI: 10.1371/journal.pone.0139586] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 09/15/2015] [Indexed: 12/31/2022] Open
Abstract
Background The lack of seasonality of swine influenza A virus (swIAV) in combination with the capacity of swine to harbor a large number of co-circulating IAV lineages, resulting in the risk for the emergence of influenza viruses with pandemic potential, stress the importance of swIAV surveillance. To date, active surveillance of swIAV worldwide is barely done because of the short detection period in nasal swab samples. Therefore, more sensitive diagnostic methods to monitor circulating virus strains are requisite. Methods qRT-PCR and virus isolations were performed on oral fluid and nasal swabs collected from individually housed pigs that were infected sequentially with H1N1 and H3N2 swIAV strains. The same methods were also applied to oral fluid samples spiked with H1N1 to study the influence of conservation time and temperature on swIAV infectivity and detectability in porcine oral fluid. Results All swIAV infected animals were found qRT-PCR positive in both nasal swabs and oral fluid. However, swIAV could be detected for a longer period in oral fluid than in nasal swabs. Despite the high detectability of swIAV in oral fluid, virus isolation from oral fluid collected from infected pigs was rare. These results are supported by laboratory studies showing that the PCR detectability of swIAV remains unaltered during a 24 h incubation period in oral fluid, while swIAV infectivity drops dramatically immediately upon contact with oral fluid (3 log titer reduction) and gets lost after 24 h conservation in oral fluid at ambient temperature. Conclusions Our data indicate that porcine oral fluid has the potential to replace nasal swabs for molecular diagnostic purposes. The difficulty to isolate swIAV from oral fluid could pose a drawback for its use in active surveillance programs.
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Affiliation(s)
- Inge Decorte
- Operational Direction Viral Diseases, Enzootic and (re)emerging diseases, CODA-CERVA, Ukkel, Belgium
| | - Mieke Steensels
- Operational Direction Viral Diseases, Avian virology and immunology, CODA-CERVA, Ukkel, Belgium
| | - Bénédicte Lambrecht
- Operational Direction Viral Diseases, Avian virology and immunology, CODA-CERVA, Ukkel, Belgium
| | - Ann Brigitte Cay
- Operational Direction Viral Diseases, Enzootic and (re)emerging diseases, CODA-CERVA, Ukkel, Belgium
| | - Nick De Regge
- Operational Direction Viral Diseases, Enzootic and (re)emerging diseases, CODA-CERVA, Ukkel, Belgium
- * E-mail:
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Sun H, Cunningham FL, Harris J, Xu Y, Long LP, Hanson-Dorr K, Baroch JA, Fioranelli P, Lutman MW, Li T, Pedersen K, Schmit BS, Cooley J, Lin X, Jarman RG, DeLiberto TJ, Wan XF. Dynamics of virus shedding and antibody responses in influenza A virus-infected feral swine. J Gen Virol 2015; 96:2569-2578. [PMID: 26297148 DOI: 10.1099/jgv.0.000225] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Given their free-ranging habits, feral swine could serve as reservoirs or spatially dynamic 'mixing vessels' for influenza A virus (IAV). To better understand virus shedding patterns and antibody response dynamics in the context of IAV surveillance amongst feral swine, we used IAV of feral swine origin to perform infection experiments. The virus was highly infectious and transmissible in feral swine, and virus shedding patterns and antibody response dynamics were similar to those in domestic swine. In the virus-inoculated and sentinel groups, virus shedding lasted ≤ 6 and ≤ 9 days, respectively. Antibody titres in inoculated swine peaked at 1 : 840 on day 11 post-inoculation (p.i.), remained there until 21 days p.i. and dropped to < 1 : 220 at 42 days p.i. Genomic sequencing identified changes in wildtype (WT) viruses and isolates from sentinel swine, most notably an amino acid divergence in nucleoprotein position 473. Using data from cell culture as a benchmark, sensitivity and specificity of a matrix gene-based quantitative reverse transcription-PCR method using nasal swab samples for detection of IAV in feral swine were 78.9 and 78.1 %, respectively. Using data from haemagglutination inhibition assays as a benchmark, sensitivity and specificity of an ELISA for detection of IAV-specific antibody were 95.4 and 95.0 %, respectively. Serological surveillance from 2009 to 2014 showed that ∼7.58 % of feral swine in the USA were positive for IAV. Our findings confirm the susceptibility of IAV infection and the high transmission ability of IAV amongst feral swine, and also suggest the need for continued surveillance of IAVs in feral swine populations.
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Affiliation(s)
- Hailiang Sun
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MI, USA
| | - Fred L Cunningham
- Mississippi Field Station, National Wildlife Research Center, Wildlife Services, Animal and Plant Health Inspection Service, US Department of Agriculture, Mississippi State, MI, USA
| | - Jillian Harris
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MI, USA
| | - Yifei Xu
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MI, USA
| | - Li-Ping Long
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MI, USA
| | - Katie Hanson-Dorr
- Mississippi Field Station, National Wildlife Research Center, Wildlife Services, Animal and Plant Health Inspection Service, US Department of Agriculture, Mississippi State, MI, USA
| | - John A Baroch
- National Wildlife Research Center, Wildlife Services, Animal and Plant Health Inspection Service, US Department of Agriculture, Fort Collins, CO, USA
| | - Paul Fioranelli
- Mississippi Field Station, National Wildlife Research Center, Wildlife Services, Animal and Plant Health Inspection Service, US Department of Agriculture, Mississippi State, MI, USA
| | - Mark W Lutman
- US Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, Fort Collins, CO, USA
| | - Tao Li
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Kerri Pedersen
- US Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, Fort Collins, CO, USA
| | - Brandon S Schmit
- National Wildlife Research Center, Wildlife Services, Animal and Plant Health Inspection Service, US Department of Agriculture, Fort Collins, CO, USA
| | - Jim Cooley
- Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, MI, USA
| | - Xiaoxu Lin
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Richard G Jarman
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Thomas J DeLiberto
- National Wildlife Research Center, Wildlife Services, Animal and Plant Health Inspection Service, US Department of Agriculture, Fort Collins, CO, USA
| | - Xiu-Feng Wan
- Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MI, USA
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Vaccination with adjuvanted recombinant neuraminidase induces broad heterologous, but not heterosubtypic, cross-protection against influenza virus infection in mice. mBio 2015; 6:e02556. [PMID: 25759506 PMCID: PMC4453582 DOI: 10.1128/mbio.02556-14] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In an attempt to assess the cross-protective potential of the influenza virus neuraminidase (NA) as a vaccine antigen, different subtypes of recombinant NA were expressed in a baculovirus system and used to vaccinate mice prior to lethal challenge with homologous, heterologous, or heterosubtypic viruses. Mice immunized with NA of subtype N2 were completely protected from morbidity and mortality in a homologous challenge and displayed significantly reduced viral lung titers. Heterologous challenge with a drifted strain resulted in morbidity but no mortality. Similar results were obtained for challenge experiments with N1 NA. Mice immunized with influenza B virus NA (from B/Yamagata/16/88) displayed no morbidity when sublethally infected with the homologous strain and, importantly, were completely protected from morbidity and mortality when lethally challenged with the prototype Victoria lineage strain or a more recent Victoria lineage isolate. Upon analyzing the NA content in 4 different inactivated-virus vaccine formulations from the 2013-2014 season via Western blot assay and enzyme-linked immunosorbent assay quantification, we found that the amount of NA does indeed vary across vaccine brands. We also measured hemagglutinin (HA) and NA endpoint titers in pre- and postvaccination human serum samples from individuals who received a trivalent inactivated seasonal influenza vaccine from the 2004-2005 season; the induction of NA titers was statistically less pronounced than the induction of HA titers. The demonstrated homologous and heterologous protective capacity of recombinant NA suggests that supplementing vaccine formulations with a standard amount of NA may offer increased protection against influenza virus infection. Despite the existence of vaccine prophylaxis and antiviral therapeutics, the influenza virus continues to cause morbidity and mortality in the human population, emphasizing the continued need for research in the field. While the majority of influenza vaccine strategies target the viral hemagglutinin, the immunodominant antigen on the surface of the influenza virion, antibodies against the viral neuraminidase (NA) have been correlated with less severe disease and decreased viral shedding in humans. Nevertheless, the amount of NA is not standardized in current seasonal vaccines, and the exact breadth of NA-based protection is unknown. Greater insight into the cross-protective potential of influenza virus NA as a vaccine antigen may pave the way for the development of influenza vaccines of greater breadth and efficacy.
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Sandbulte MR, Spickler AR, Zaabel PK, Roth JA. Optimal Use of Vaccines for Control of Influenza A Virus in Swine. Vaccines (Basel) 2015; 3:22-73. [PMID: 26344946 PMCID: PMC4494241 DOI: 10.3390/vaccines3010022] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 01/09/2015] [Accepted: 01/19/2015] [Indexed: 12/29/2022] Open
Abstract
Influenza A virus in swine (IAV-S) is one of the most important infectious disease agents of swine in North America. In addition to the economic burden of IAV-S to the swine industry, the zoonotic potential of IAV-S sometimes leads to serious public health concerns. Adjuvanted, inactivated vaccines have been licensed in the United States for over 20 years, and there is also widespread usage of autogenous/custom IAV-S vaccines. Vaccination induces neutralizing antibodies and protection against infection with very similar strains. However, IAV-S strains are so diverse and prone to mutation that these vaccines often have disappointing efficacy in the field. This scientific review was developed to help veterinarians and others to identify the best available IAV-S vaccine for a particular infected herd. We describe key principles of IAV-S structure and replication, protective immunity, currently available vaccines, and vaccine technologies that show promise for the future. We discuss strategies to optimize the use of available IAV-S vaccines, based on information gathered from modern diagnostics and surveillance programs. Improvements in IAV-S immunization strategies, in both the short term and long term, will benefit swine health and productivity and potentially reduce risks to public health.
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Affiliation(s)
- Matthew R Sandbulte
- Center for Food Security and Public Health, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
| | - Anna R Spickler
- Center for Food Security and Public Health, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
| | - Pamela K Zaabel
- Center for Food Security and Public Health, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
| | - James A Roth
- Center for Food Security and Public Health, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
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Wohlbold TJ, Krammer F. In the shadow of hemagglutinin: a growing interest in influenza viral neuraminidase and its role as a vaccine antigen. Viruses 2014; 6:2465-94. [PMID: 24960271 PMCID: PMC4074938 DOI: 10.3390/v6062465] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 06/06/2014] [Accepted: 06/13/2014] [Indexed: 01/03/2023] Open
Abstract
Despite the availability of vaccine prophylaxis and antiviral therapeutics, the influenza virus continues to have a significant, annual impact on the morbidity and mortality of human beings, highlighting the continued need for research in the field. Current vaccine strategies predominantly focus on raising a humoral response against hemagglutinin (HA)—the more abundant, immunodominant glycoprotein on the surface of the influenza virus. In fact, anti-HA antibodies are often neutralizing, and are used routinely to assess vaccine immunogenicity. Neuraminidase (NA), the other major glycoprotein on the surface of the influenza virus, has historically served as the target for antiviral drug therapy and is much less studied in the context of humoral immunity. Yet, the quest to discern the exact importance of NA-based protection is decades old. Also, while antibodies against the NA glycoprotein fail to prevent infection of the influenza virus, anti-NA immunity has been shown to lessen the severity of disease, decrease viral lung titers in animal models, and reduce viral shedding. Growing evidence is intimating the possible gains of including the NA antigen in vaccine design, such as expanded strain coverage and increased overall immunogenicity of the vaccine. After giving a tour of general influenza virology, this review aims to discuss the influenza A virus neuraminidase while focusing on both the historical and present literature on the use of NA as a possible vaccine antigen.
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Affiliation(s)
- Teddy John Wohlbold
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1124, New York, NY 10029, USA.
| | - Florian Krammer
- Department of Microbiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1124, New York, NY 10029, USA.
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Crisci E, Mussá T, Fraile L, Montoya M. Review: Influenza virus in pigs. Mol Immunol 2013; 55:200-11. [DOI: 10.1016/j.molimm.2013.02.008] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 02/23/2013] [Accepted: 02/25/2013] [Indexed: 12/19/2022]
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Nokireki T, Laine T, London L, Ikonen N, Huovilainen A. The first detection of influenza in the Finnish pig population: a retrospective study. Acta Vet Scand 2013; 55:69. [PMID: 24047612 PMCID: PMC3850993 DOI: 10.1186/1751-0147-55-69] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 09/10/2013] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND Swine influenza is an infectious acute respiratory disease of pigs caused by influenza A virus. We investigated the time of entry of swine influenza into the Finnish pig population. We also describe the molecular detection of two types of influenza A (H1N1) viruses in porcine samples submitted in 2009 and 2010.This retrospective study was based on three categories of samples: blood samples collected for disease monitoring from pigs at major slaughterhouses from 2007 to 2009; blood samples from pigs in farms with a special health status taken in 2008 and 2009; and diagnostic blood samples from pigs in farms with clinical signs of respiratory disease in 2008 and 2009. The blood samples were tested for influenza A antibodies with an antibody ELISA. Positive samples were further analyzed for H1N1, H3N2, and H1N2 antibodies with a hemagglutination inhibition test. Diagnostic samples for virus detection were subjected to influenza A M-gene-specific real-time RT-PCR and to pandemic influenza A H1N1-specific real-time RT-PCR. Positive samples were further analyzed with RT-PCRs designed for this purpose, and the PCR products were sequenced and sequences analyzed phylogenetically. RESULTS In the blood samples from pigs in special health class farms producing replacement animals and in diagnostic blood samples, the first serologically positive samples originated from the period July-August 2008. In samples collected for disease monitoring, < 0.1%, 0% and 16% were positive for antibodies against influenza A H1N1 in the HI test in 2007, 2008, and 2009, respectively. Swine influenza A virus of avian-like H1N1 was first detected in diagnostic samples in February 2009. In 2009 and 2010, the avian-like H1N1 virus was detected on 12 and two farms, respectively. The pandemic H1N1 virus (A(H1N1)pdm09) was detected on one pig farm in 2009 and on two farms in 2010. CONCLUSIONS Based on our study, swine influenza of avian-like H1N1 virus was introduced into the Finnish pig population in 2008 and A(H1N1)pdm09 virus in 2009. The source of avian-like H1N1 infection could not be determined. Cases of pandemic H1N1 in pigs coincided with the period when the A(H1N1)pdm09 virus was spread in humans in Finland.
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Dukhovlinov I, Al-Shekhadat R, Fedorova E, Stepanova L, Potapchuk M, Repko I, Rusova O, Orlov A, Tsybalova L, Kiselev O. Study of immunogenicity of recombinant proteins based on hemagglutinin and neuraminidase conservative epitopes of influenza A virus. Med Sci Monit Basic Res 2013; 19:221-7. [PMID: 23969554 PMCID: PMC3762522 DOI: 10.12659/msmbr.884002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Background Recombinant hemagglutinin (rHA) and neurominidase (rNA) developed in our investigation are amino acid sequence consensus variants of H1N1 2009 subtype influenza virus strain, also including immunogenic epitopes typical for other influenza virus subtypes (H3N1 and H5N1). Substitutions were made: typical for Russian virus isolates (in HA – S220T, NA – D248N) and in active centers of molecules – R118L, R293L, R368L; C92S, C417S to increase recombinant proteins stability in E. coli. The aim of the present work was to study immunogenicity of the obtained rHA and rNA. Material/Methods Fragments aa 83–469 of NA and aa 61–287 of HA were chosen because they include the main B-cell epitopes and are the minimal structures for correct folding of target proteins. The designed nucleotide sequences were synthesized and purified and the expression of rNA and rNA were analyzed. For immunization and virus challenge we used influenza viruses A/California/04/2009 (H1N1), A/PR/8/34 (H1N1), A/Perth/16/2009 (H3N2), A/Chicken/Kurgan/05/2005 R.G. (H5N1), and B/Florida/04/2006. Specific IgG levels were determined by ELISA in 96-well ELISA plates. Significant differences of survival in mouse groups were analyzed by Mantel-Cox (log-rank) and Gehan-Breslow-Wilcoxon tests. Results The obtained results demonstrate the high immunogenicity and ability of indicated proteins mixture to provide similar cross-protection against influenza viruses of the H1N1 subtype. Conclusions The data obtained suggest efficient pluripotent vaccine creation based on HA and NA conservative regions.
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Exposure to a low pathogenic A/H7N2 virus in chickens protects against highly pathogenic A/H7N1 virus but not against subsequent infection with A/H5N1. PLoS One 2013; 8:e58692. [PMID: 23469288 PMCID: PMC3587606 DOI: 10.1371/journal.pone.0058692] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 02/05/2013] [Indexed: 11/22/2022] Open
Abstract
Recent evidences have demonstrated that the presence of low pathogenic avian influenza viruses (LPAIV) may play an important role in host ecology and transmission of avian influenza viruses (AIV). While some authors have clearly demonstrated that LPAIV can mutate to render highly pathogenic avian influenza viruses (HPAIV), others have shown that their presence could provide the host with enough immunological memory to resist re-infections with HPAIV. In order to experimentally study the role of pre-existing host immunity, chickens previously infected with H7N2 LPAIV were subsequently challenged with H7N1 HPAIV. Pre-infection of chickens with H7N2 LAPIV conferred protection against the lethal challenge with H7N1 HPAIV, dramatically reducing the viral shedding, the clinical signs and the pathological outcome. Correlating with the protection afforded, sera from chickens primed with H7N2 LPAIV reacted with the H7-AIV subtype in hemagglutination inhibition assay and specifically with the N2-neuraminidase antigen. Conversely, subsequent exposure to H5N1 HPAIV resulted in a two days-delay on the onset of disease but all chickens died by 7 days post-challenge. Lack of protection correlated with the absence of H5-hemagglutining inhibitory antibodies prior to H5N1 HPAIV challenge. Our data suggest that in naturally occurring outbreaks of HPAIV, birds with pre-existing immunity to LPAIV could survive lethal infections with HA-homologous HPAIV but not subsequent re-infections with HA-heterologous HPAIV. These results could be useful to better understand the dynamics of AIV in chickens and might help in future vaccine formulations.
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Schotsaert M, Saelens X, Leroux-Roels G. Influenza vaccines: T-cell responses deserve more attention. Expert Rev Vaccines 2013; 11:949-62. [PMID: 23002976 DOI: 10.1586/erv.12.71] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Currently licensed influenza vaccines rely predominantly on the induction of strain-matched hemagglutination inhibition antibody responses. These vaccines have a proven record of safety and efficacy in preventing influenza-induced illness and complications. However, they do not confer protection to all vaccinated individuals, and the protection they afford is short-lived, particularly in older adults. Hemagglutination inhibition titers induced by these vaccines are considered correlates of protection, but recent data demonstrate that this is not always the case. It is clear that better insight is needed into the immune responses that correlate with protection against human influenza. Influenza vaccines that can induce cross-reactive cellular immune responses (CD4(+) and/or CD8(+) T-cell responses) might correct some of the shortcomings of currently used influenza vaccines. In the future, the use of infection-permissive and disease-modifying vaccines that allow for the induction of cross-reactive T-cell responses may become a valuable complement to the administration of trivalent inactivated influenza vaccines.
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Neuraminidase-inhibiting antibody is a correlate of cross-protection against lethal H5N1 influenza virus in ferrets immunized with seasonal influenza vaccine. J Virol 2013; 87:3053-61. [PMID: 23283953 DOI: 10.1128/jvi.02434-12] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In preparing for the threat of a pandemic of avian H5N1 influenza virus, we need to consider the significant delay (4 to 6 months) necessary to produce a strain-matched vaccine. As some degree of cross-reactivity between seasonal influenza vaccines and H5N1 virus has been reported, this was further explored in the ferret model to determine the targets of protective immunity. Ferrets were vaccinated with two intramuscular inoculations of trivalent inactivated split influenza vaccine or subcomponent vaccines, with and without adjuvant, and later challenged with a lethal dose of A/Vietnam/1203/2004 (H5N1) influenza virus. We confirmed that vaccination with seasonal influenza vaccine afforded partial protection against lethal H5N1 challenge and showed that use of either AlPO(4) or Iscomatrix adjuvant with the vaccine resulted in complete protection against disease and death. The protection was due exclusively to the H1N1 vaccine component, and although the hemagglutinin contributed to protection, the dominant protective response was targeted toward the neuraminidase (NA) and correlated with sialic acid cleavage-inhibiting antibody titers. Purified heterologous NA formulated with Iscomatrix adjuvant was also protective. These results suggest that adjuvanted seasonal trivalent vaccine could be used as an interim measure to decrease morbidity and mortality from H5N1 prior to the availability of a specific vaccine. The data also highlight that an inducer of cross-protective immunity is the NA, a protein whose levels are not normally monitored in vaccines and whose capacity to induce immunity in recipients is not normally assessed.
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Prior infection of chickens with H1N1 or H1N2 avian influenza elicits partial heterologous protection against highly pathogenic H5N1. PLoS One 2012; 7:e51933. [PMID: 23240067 PMCID: PMC3519904 DOI: 10.1371/journal.pone.0051933] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 11/13/2012] [Indexed: 02/03/2023] Open
Abstract
There is a critical need to have vaccines that can protect against emerging pandemic influenza viruses. Commonly used influenza vaccines are killed whole virus that protect against homologous and not heterologous virus. Using chickens we have explored the possibility of using live low pathogenic avian influenza (LPAI) A/goose/AB/223/2005 H1N1 or A/WBS/MB/325/2006 H1N2 to induce immunity against heterologous highly pathogenic avian influenza (HPAI) A/chicken/Vietnam/14/2005 H5N1. H1N1 and H1N2 replicated in chickens but did not cause clinical disease. Following infection, chickens developed nucleoprotein and H1 specific antibodies, and reduced H5N1 plaque size in vitro in the absence of H5 neutralizing antibodies at 21 days post infection (DPI). In addition, heterologous cell mediated immunity (CMI) was demonstrated by antigen-specific proliferation and IFN-γ secretion in PBMCs re-stimulated with H5N1 antigen. Following H5N1 challenge of both pre-infected and naïve controls chickens housed together, all naïve chickens developed acute disease and died while H1N1 or H1N2 pre-infected chickens had reduced clinical disease and 70–80% survived. H1N1 or H1N2 pre-infected chickens were also challenged with H5N1 and naïve chickens placed in the same room one day later. All pre-infected birds were protected from H5N1 challenge but shed infectious virus to naïve contact chickens. However, disease onset, severity and mortality was reduced and delayed in the naïve contacts compared to directly inoculated naïve controls. These results indicate that prior infection with LPAI virus can generate heterologous protection against HPAI H5N1 in the absence of specific H5 antibody.
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21
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Protection of guinea pigs by vaccination with a recombinant swinepox virus co-expressing HA1 genes of swine H1N1 and H3N2 influenza viruses. Arch Virol 2012; 158:629-37. [DOI: 10.1007/s00705-012-1539-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 10/04/2012] [Indexed: 11/27/2022]
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Patel A, Kobinger GP. Evaluation of mismatched immunity against influenza viruses. Future Virol 2012. [DOI: 10.2217/fvl.12.105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Prior immunity against influenza A viruses generates sterilizing immunity against matched (homologous) viruses and varying levels of protection against mismatched (heterologous) viruses of the same or different subtypes. Natural immunity carries the risk of high morbidity and mortality, therefore immunization offers the best preventative measure. Antibody responses against the viral hemagglutinin protein correlate with protection in humans and evidence increasingly supports a role for robust cellular immune responses. By exploiting mismatched immunity, current conventional and experimental vaccine candidates can improve the generation of cross-protective immune responses against heterologous viruses. Experimental vaccines such as virus-like particles, DNA vectors, viral vectors and broadly neutralizing antibodies are able to expand cross-protection through mismatched B- and T-cell responses. However, the generation of mismatched immune responses can also have the opposite effect and impair protective immunity. This review discusses mismatched immunity in the context of natural infection and immunization. Additionally, we discuss strategies to exploit mismatched immunity in order to improve current conventional and experimental influenza A virus vaccines.
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Affiliation(s)
- Ami Patel
- San Raffaele-Telethon Institute of Gene Therapy (hSR-TIGET), Milan, Italy Division of Gene Therapy & Regenerative Medicine, via Olgettina 58, Milan, Italy, 20132
| | - Gary P Kobinger
- Department of Medical Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
- Department of Immunology, University of Manitoba, Winnipeg, Manitoba, Canada
- Special Pathogens Programme, National Microbiology Laboratory, Public Health Agency of Canada, Canadian Science Centre for Human & Animal Health, 1015 Arlington Street, Winnipeg, Manitoba, Canada, R3E 3R2
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Nfon C, Berhane Y, Pasick J, Kobinger G, Kobasa D, Babiuk S. Prior infection of chickens with H1N1 avian influenza virus elicits heterologous protection against highly pathogenic H5N2. Vaccine 2012; 30:7187-92. [DOI: 10.1016/j.vaccine.2012.10.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 08/28/2012] [Accepted: 10/05/2012] [Indexed: 11/26/2022]
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Baz M, Papenburg J, Hamelin ME, Ouakki M, Skowronski DM, De Serres G, Boivin G. Seroconversion to seasonal influenza viruses after A(H1N1)pdm09 virus infection, Quebec, Canada. Emerg Infect Dis 2012; 18:1132-4. [PMID: 22710312 PMCID: PMC3376798 DOI: 10.3201/eid1807.111680] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We looked for cross-reactive antibodies in 122 persons with paired serum samples collected during the 2009 pandemic of influenza virus A(H1N1)pdm09. Eight (12%) of 67 persons with A(H1N1)pdm09 infection confirmed by reverse transcription PCR and/or serology also seroconverted to the seasonal A/Brisbane/59/2007 (H1N1) virus, compared with 1 (2%) of 55 A(H1N1)pdm09-negative persons (p<0.05).
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Affiliation(s)
- Mariana Baz
- Centre Hospitalier Universitaire de Quebec, Quebec City, Quebec, Canada
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De Vleeschauwer AR, Baras B, Kyriakis CS, Jacob V, Planty C, Giannini SL, Mossman S, Van Reeth K. Efficacy of an AS03A-adjuvanted split H5N1 influenza vaccine against an antigenically distinct low pathogenic H5N1 virus in pigs. Vaccine 2012; 30:5557-63. [DOI: 10.1016/j.vaccine.2012.06.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 05/27/2012] [Accepted: 06/10/2012] [Indexed: 01/23/2023]
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Xu J, Huang D, Liu S, Lin H, Zhu H, Liu B, Lu C. Immune responses and protection efficacy of a recombinant swinepox virus expressing HA1 against swine H3N2 influenza virus in mice and pigs. Virus Res 2012; 167:188-95. [PMID: 22584406 DOI: 10.1016/j.virusres.2012.04.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Revised: 03/28/2012] [Accepted: 04/27/2012] [Indexed: 10/28/2022]
Abstract
Swine influenza virus (SIV) is not only an important respiratory pathogen in pigs but also a potent threat to human health. Even though immunization with recombinant vaccinia poxviruses expressing protective antigens as a vaccination strategy has been widely used for many infectious diseases, development of recombinant swinepox virus (rSPV) vector for this purpose has been less successful. Here, we report the construction of a recombinant swinepox virus (rSPV) expressing hemagglutinin (HA1) of H3N2 SIV (rSPV-H3). Immune responses and protection efficacy of the vaccination vector were assessed in both mouse and pig models. Prime and boost inoculations of rSPV-H3 yielded neutralization antibody against SIV and elicited potent H3N2 SIV-specific INF-γ response from T-lymphocytes. Complete protection of pigs against H3N2 SIV challenge was achieved. No pigs showed severe systemic and local reactions and no SIV was found shed from the pigs vaccinated with rSPV-H3 after challenge. The data suggest that the SPV-based recombinant vector expressing HA1 of H3N2 SIV might serve as a promising SIV vaccine for protection against SIV infection.
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Affiliation(s)
- Jiarong Xu
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
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Cold-adapted pandemic 2009 H1N1 influenza virus live vaccine elicits cross-reactive immune responses against seasonal and H5 influenza A viruses. J Virol 2012; 86:5953-8. [PMID: 22438541 DOI: 10.1128/jvi.07149-11] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The rapid transmission of the pandemic 2009 H1N1 influenza virus (pH1N1) among humans has raised the concern of a potential emergence of reassortment between pH1N1 and highly pathogenic influenza strains, especially the avian H5N1 influenza virus. Here, we report that the cold-adapted pH1N1 live attenuated vaccine (CApH1N1) elicits cross-reactive immunity to seasonal and H5 influenza A viruses in the mouse model. Immunization with CApH1N1 induced both systemic and mucosal antibodies with broad reactivity to seasonal and H5 strains, including HAPI H5N1 and the avian H5N2 virus, providing complete protection against heterologous and heterosubtypic lethal challenges. Our results not only accentuate the merit of using live attenuated influenza virus vaccines in view of cross-reactivity but also represent the potential of CApH1N1 live vaccine for mitigating the clinical severity of infections that arise from reassortments between pH1N1 and highly pathogenic H5 subtype viruses.
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Immune responses and protective efficacy of a recombinant swinepox virus expressing HA1 against swine H1N1 influenza virus in mice and pigs. Vaccine 2012; 30:3119-25. [PMID: 22391400 DOI: 10.1016/j.vaccine.2012.02.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/27/2012] [Accepted: 02/10/2012] [Indexed: 11/22/2022]
Abstract
Swine influenza virus (SIV) is not only an important respiratory pathogen in pigs but also a potent threat to human health. Although immunization with recombinant poxviruses expressing protective antigens as vaccines has been widely used for against many infectious diseases, development of recombinant swinepox virus (rSPV) vector for the purpose has been less successful. Here, we report the construction of a recombinant swinepox virus (rSPV-HA1) expressing hemagglutinin (HA1) of H1N1 SIV. Immune responses and protection efficacy of the vaccination vector were evaluated in both the mouse model and the natural host: pig. Prime and boost inoculations of rSPV-HA1 yielded high levels of neutralization antibody against SIV and elicited potent H1N1 SIV-specific IFN-γ response from T-lymphocytes. Complete protection of pigs against H1N1 SIV challenge was observed. No pigs showed evident systemic and local reactions to the vaccine and no SIV shedding was detected from pigs vaccinated with rSPV-HA1 after challenge. Our data demonstrated that the recombinant swinepox virus encoding HA1 of SIV H1N1 may serve as a promising SIV vaccine for protection against SIV infection.
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Swine influenza virus vaccines: to change or not to change-that's the question. Curr Top Microbiol Immunol 2012; 370:173-200. [PMID: 22976350 DOI: 10.1007/82_2012_266] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Commercial vaccines currently available against swine influenza virus (SIV) are inactivated, adjuvanted, whole virus vaccines, based on H1N1 and/or H3N2 and/or H1N2 SIVs. In keeping with the antigenic and genetic differences between SIVs circulating in Europe and the US, the vaccines for each region are produced locally and contain different strains. Even within a continent, there is no standardization of vaccine strains, and the antigen mass and adjuvants can also differ between different commercial products. Recombinant protein vaccines against SIV, vector, and DNA vaccines, and vaccines attenuated by reverse genetics have been tested in experimental studies, but they have not yet reached the market. In this review, we aim to present a critical analysis of the performance of commercial inactivated and novel generation SIV vaccines in experimental vaccination challenge studies in pigs. We pay special attention to the differences between commercial SIV vaccines and vaccination attitudes in Europe and in North America, to the issue of vaccine strain selection and changes, and to the potential advantages of novel generation vaccines over the traditional killed SIV vaccines.
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Kappes MA, Sandbulte MR, Platt R, Wang C, Lager KM, Henningson JN, Lorusso A, Vincent AL, Loving CL, Roth JA, Kehrli ME. Vaccination with NS1-truncated H3N2 swine influenza virus primes T cells and confers cross-protection against an H1N1 heterosubtypic challenge in pigs. Vaccine 2011; 30:280-8. [PMID: 22067263 DOI: 10.1016/j.vaccine.2011.10.098] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 10/21/2011] [Accepted: 10/30/2011] [Indexed: 10/15/2022]
Abstract
The diversity of contemporary swine influenza virus (SIV) strains impedes effective immunization of swine herds. Mucosally delivered, attenuated virus vaccines are one approach with potential to provide broad cross-protection. Reverse genetics-derived H3N2 SIV virus with truncated NS1 (NS1Δ126 TX98) is attenuated and immunogenic when delivered intranasally in young pigs. We analyzed T-cell priming and cross-protective efficacy in weanling piglets after intranasal inoculation with NS1Δ126 TX98 versus wild type TX98. In vivo replication of the truncation mutant was minimal compared to the wild type virus. T-cell responses were greater in magnitude in pigs infected with the wild type virus in in vitro restimulation assays. According to the expression of activation marker CD25, peripheral T cell recall responses in NS1Δ126 TX98 infected pigs were minimal. However, intracellular IFN-γ data indicate that the attenuated virus induced virus-specific CD4(+)CD8(-), CD4(+)CD8(+), CD4(-)CD8(+), and γδ T cells within 28 days. The IFN-γ response appeared to contract, as responses were reduced at later time points prior to challenge. CD4(+)CD8(+) cells isolated 5 days after heterosubtypic H1N1 challenge (day 70 overall) showed an elevated CD25 response to virus restimulation. Pigs previously infected with wild type TX98 were protected from replication of the H1N1 challenge virus. Vaccination with NS1Δ126 TX98 was associated with significantly lower levels of Th1-associated cytokines in infected lungs but provided partial cross-protection against the H1N1 challenge. These results demonstrate that NS1Δ SIV vaccines can elicit cell-mediated cross-protection against antigenically divergent strains.
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Affiliation(s)
- Matthew A Kappes
- Virus and Prion Diseases Research Unit, National Animal Disease Center, USDA-ARS, 1920 Dayton Ave, PO Box 70, Ames, IA 50010, USA
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Kreijtz JHCM, Fouchier RAM, Rimmelzwaan GF. Immune responses to influenza virus infection. Virus Res 2011; 162:19-30. [PMID: 21963677 DOI: 10.1016/j.virusres.2011.09.022] [Citation(s) in RCA: 227] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 09/15/2011] [Accepted: 09/15/2011] [Indexed: 10/17/2022]
Abstract
Influenza viruses cause annual outbreaks of respiratory tract infection with attack rates of 5-10%. This means that humans are infected repeatedly with intervals of, on average, 10-20 years. Upon each infection subjects develop innate and adaptive immune responses which aim at clearing the infection. Strain-specific antibody responses are induced, which exert selective pressure on circulating influenza viruses and which drive antigenic drift of seasonal influenza viruses, especially in the hemagglutinin molecule. This antigenic drift necessitates updating of seasonal influenza vaccines regularly in order to match the circulating strains. Upon infection also virus-specific T cell responses are induced, including CD4+ T helper cells and CD8+ cytotoxic T cells. These cells are mainly directed to conserved proteins and therefore display cross-reactivity with a variety of influenza A viruses of different subtypes. T cell mediated immunity therefore may contribute to so-called heterosubtypic immunity and may afford protection against antigenically distinct, potentially pandemic influenza viruses. At present, novel viral targets are identified that may help to develop broad-protective vaccines. Here we review the various arms of the immune response to influenza virus infections and their viral targets and discuss the possibility of developing universal vaccines. The development of such novel vaccines would imply that also new immune correlates of protection need to be established in order to facilitate assessment of vaccine efficacy.
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Affiliation(s)
- J H C M Kreijtz
- Department of Virology, Erasmus MC, Rotterdam, The Netherlands
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Mahnke YD, Saqr A, Hazenfeld S, Brady RC, Roederer M, Subbramanian RA. Age-related changes in durability and function of vaccine-elicited influenza-specific CD4(+) T-cell responses. Vaccine 2011; 29:8606-14. [PMID: 21939709 DOI: 10.1016/j.vaccine.2011.09.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 08/15/2011] [Accepted: 09/07/2011] [Indexed: 12/22/2022]
Abstract
The major antigenic component of licensed influenza vaccines, hemagglutinin (HA), elicits predominantly type-specific antibody responses, thus necessitating frequent antigenic updates to the annual vaccine. However, accumulating evidence suggests that influenza vaccines can also induce significant cross-reactive T-cell responses to highly divergent, heterosubtypic HA antigens not included in the vaccine. Influenza vaccines are less effective among the elderly and studies that characterize cross-reactive T-cell immunity in this vulnerable population are much needed. Here, we systematically compare the ex vivo frequency, cytokine profile and phenotype of vaccine-elicited HA-specific T-cell responses among a cohort of young (18-49 years old) and elderly (≥70 years old) vaccinees, as well as the maturation and activation phenotype of total CD4(+) and CD8(+) T-cells. IFN-γ production after in vitro expansion and HA-specific Ab titers were also determined. We find that vaccine-elicited ex vivo frequencies of CD4(+) T-cells elicited by vaccination reactive to any given homo- or heterosubtypic Ag were comparable across the two age groups. While, no differences were observed between age groups in the phenotype of Ag-specific or total CD4(+) T-cells, PBMC from young adults were superior at producing IFN-γ after short-term Ag-specific culture. Significantly, while vaccine-elicited T-cell responses were durable among the younger vaccinees, they were short-lived among the elderly. These results have important ramifications for our understanding of vaccine-induced changes in the magnitude and functionality of HA-specific CD4(+) T-cells, as well as age-related alterations in response kinetics.
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Affiliation(s)
- Yolanda D Mahnke
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
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Abstract
Novel pandemic influenza viruses enter the human population with some regularity and can cause disease that is severe and widespread. The emergence of novel viruses, historically, has often been coupled with the disappearance of existing seasonal virus strains. Here, we propose that the elimination of seasonal strains during virus pandemics is a process mediated, at the population level, by humoral immunity. Specifically, we suggest that infection with a novel virus strain, in people previously exposed to influenza viruses, can elicit a memory B cell response against conserved hemagglutinin stalk epitopes and/or neuraminidase epitopes. The anti-stalk and/or anti-neuraminidase antibodies then act to diminish the clinical severity of disease caused by novel influenza viruses and to eliminate seasonal virus strains.
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Gerloff NA, Kremer JR, Charpentier E, Sausy A, Olinger CM, Weicherding P, Schuh J, Van Reeth K, Muller CP. Swine Influenza Virus Antibodies in Humans, Western Europe, 2009. Emerg Infect Dis 2011; 17:403-11. [DOI: 10.3201/eid1703.100851] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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De Vleeschauwer AR, Van Poucke SG, Karasin AI, Olsen CW, Van Reeth K. Cross-protection between antigenically distinct H1N1 swine influenza viruses from Europe and North America. Influenza Other Respir Viruses 2010; 5:115-22. [PMID: 21306575 PMCID: PMC4942007 DOI: 10.1111/j.1750-2659.2010.00164.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND An avian-like H1N1 swine influenza virus (SIV) is enzootic in swine populations of Western Europe. The virus is antigenically distinct from H1N1 SIVs in North America that have a classical swine virus-lineage H1 hemagglutinin, as does the pandemic (H1N1) 2009 virus. However, the significance of this antigenic difference for cross-protection among pigs remains unknown. OBJECTIVES We examined protection against infection with a North American triple reassortant H1N1 SIV [A/swine/Iowa/H04YS2/04 (sw/IA/04)] in pigs infected with a European avian-like SIV [A/swine/Belgium/1/98 (sw/B/98)] 4 weeks earlier. We also examined the genetic relationships and serologic cross-reactivity between both SIVs and with a pandemic (H1N1) 2009 virus [A/California/04/09 (Calif/09)]. RESULTS After intranasal inoculation with sw/IA/04, all previously uninfected control pigs showed nasal virus excretion, high virus titers in the entire respiratory tract at 4 days post-challenge (DPCh) and macroscopic lung lesions. Most pigs previously infected with sw/B/98 tested negative for sw/IA/04 in nasal swabs and respiratory tissues, and none had lung lesions. At challenge, these pigs had low levels of cross-reactive virus neutralizing and neuraminidase inhibiting (NI) antibodies to sw/IA/04, but no hemagglutination-inhibiting antibodies. They showed similar antibody profiles when tested against Calif/09, but NI antibody titers were higher against Calif/09 than sw/IA/04, reflecting the higher genetic homology of the sw/B/98 neuraminidase with Calif/09. CONCLUSIONS Our data indicate that immunity induced by infection with European avian-like H1N1 SIV affords protection for pigs against North American H1N1 SIVs with a classical H1, and they suggest cross-protection against the pandemic (H1N1) 2009 virus.
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De Vleeschauwer A, Van Reeth K. Prior infection of pigs with swine influenza viruses is a barrier to infection with avian influenza viruses. Vet Microbiol 2010; 146:340-5. [PMID: 20627621 DOI: 10.1016/j.vetmic.2010.05.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 04/29/2010] [Accepted: 05/05/2010] [Indexed: 10/19/2022]
Abstract
Although pigs are susceptible to avian influenza viruses (AIV) of different subtypes, the incidence of AIV infections in the field appears to be low. Swine H1N1, H3N2 and H1N2 influenza viruses (SIV) are enzootic worldwide and most pigs have antibodies to 1 or more SIV subtypes. This study aimed to examine whether infection-immunity to H1N1 or H3N2 SIV may (1) protect pigs against subsequent infections with AIV of various haemagglutinin and/or neuraminidase subtypes and/or (2) interfere with the serological diagnosis of AIV infection by haemagglutination inhibition (HI) or virus neutralization (VN) tests. Pigs were inoculated intranasally with an H1N1 or H3N2 SIV or left uninoculated. Four or 6 weeks later all pigs were challenged intranasally with 1 of 3 AIV subtypes (H4N6, H5N2 or H7N1). Fifteen out of 17 challenge control pigs shed the respective AIV for 4-6 days post-inoculation and 16 developed HI and VN antibodies. In contrast, 28 of the 29 SIV-immune pigs did not have detectable AIV shedding. Only 12 SIV-immune pigs developed HI antibodies to the AIV used for challenge and 14 had VN antibodies. Antibody titres to the AIV were low in both control and SIV-immune pigs. Our data show that prior infection of pigs with SIV is a barrier to infection with AIV of unrelated subtypes. Serological screening in regions where SIV is enzootic is only useful when the AIV strain for which the pigs need to be tested is known.
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Affiliation(s)
- Annebel De Vleeschauwer
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium
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Brookes SM, Núñez A, Choudhury B, Matrosovich M, Essen SC, Clifford D, Slomka MJ, Kuntz-Simon G, Garcon F, Nash B, Hanna A, Heegaard PMH, Quéguiner S, Chiapponi C, Bublot M, Garcia JM, Gardner R, Foni E, Loeffen W, Larsen L, Van Reeth K, Banks J, Irvine RM, Brown IH. Replication, pathogenesis and transmission of pandemic (H1N1) 2009 virus in non-immune pigs. PLoS One 2010; 5:e9068. [PMID: 20140096 PMCID: PMC2816721 DOI: 10.1371/journal.pone.0009068] [Citation(s) in RCA: 132] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 12/21/2009] [Indexed: 11/19/2022] Open
Abstract
The declaration of the human influenza A pandemic (H1N1) 2009 (H1N1/09) raised important questions, including origin and host range [1], [2]. Two of the three pandemics in the last century resulted in the spread of virus to pigs (H1N1, 1918; H3N2, 1968) with subsequent independent establishment and evolution within swine worldwide [3]. A key public and veterinary health consideration in the context of the evolving pandemic is whether the H1N1/09 virus could become established in pig populations [4]. We performed an infection and transmission study in pigs with A/California/07/09. In combination, clinical, pathological, modified influenza A matrix gene real time RT-PCR and viral genomic analyses have shown that infection results in the induction of clinical signs, viral pathogenesis restricted to the respiratory tract, infection dynamics consistent with endemic strains of influenza A in pigs, virus transmissibility between pigs and virus-host adaptation events. Our results demonstrate that extant H1N1/09 is fully capable of becoming established in global pig populations. We also show the roles of viral receptor specificity in both transmission and tissue tropism. Remarkably, following direct inoculation of pigs with virus quasispecies differing by amino acid substitutions in the haemagglutinin receptor-binding site, only virus with aspartic acid at position 225 (225D) was detected in nasal secretions of contact infected pigs. In contrast, in lower respiratory tract samples from directly inoculated pigs, with clearly demonstrable pulmonary pathology, there was apparent selection of a virus variant with glycine (225G). These findings provide potential clues to the existence and biological significance of viral receptor-binding variants with 225D and 225G during the 1918 pandemic [5].
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MESH Headings
- Animals
- Antigens, Viral/analysis
- Antigens, Viral/immunology
- Base Sequence
- Chick Embryo
- Disease Outbreaks
- Hemagglutinins, Viral/chemistry
- Hemagglutinins, Viral/genetics
- Humans
- Immunohistochemistry
- Influenza A Virus, H1N1 Subtype/genetics
- Influenza A Virus, H1N1 Subtype/immunology
- Influenza A Virus, H1N1 Subtype/pathogenicity
- Influenza, Human/epidemiology
- Influenza, Human/virology
- Mutation
- Orthomyxoviridae Infections/pathology
- Orthomyxoviridae Infections/transmission
- Orthomyxoviridae Infections/veterinary
- Respiratory System/metabolism
- Respiratory System/pathology
- Respiratory System/virology
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Analysis, DNA
- Swine
- Swine Diseases/pathology
- Swine Diseases/virology
- Viral Matrix Proteins/genetics
- Virus Replication
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Affiliation(s)
- Sharon M. Brookes
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Alejandro Núñez
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Bhudipa Choudhury
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
- OFFLU, World Organisation for Animal Health, Paris, France
| | | | - Stephen C. Essen
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Derek Clifford
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Marek J. Slomka
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Gaëlle Kuntz-Simon
- Agence Française de Sécurité Sanitaire des Aliments, LERAPP, Unité Virologie Immunologie Porcines, Zoopôle Les Croix, Ploufragan, France
| | - Fanny Garcon
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Bethany Nash
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Amanda Hanna
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Peter M. H. Heegaard
- National Veterinary Institute, Technical University of Denmark, København, Denmark
| | - Stéphane Quéguiner
- Agence Française de Sécurité Sanitaire des Aliments, LERAPP, Unité Virologie Immunologie Porcines, Zoopôle Les Croix, Ploufragan, France
| | - Chiara Chiapponi
- Istituto Zooprofilattico Sperimentale Lombardia ed Emilia Romagna, Sezione di Parma, Parma, Italy
| | | | | | - Rebecca Gardner
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Emanuela Foni
- Istituto Zooprofilattico Sperimentale Lombardia ed Emilia Romagna, Sezione di Parma, Parma, Italy
| | - Willie Loeffen
- Central Veterinary Institute of Wageningen UR, Lelystad, The Netherlands
| | - Lars Larsen
- National Veterinary Institute, Technical University of Denmark, København, Denmark
| | | | - Jill Banks
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Richard M. Irvine
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
| | - Ian H. Brown
- Veterinary Laboratories Agency-Weybridge, EU/OIE/FAO Reference Laboratory for Avian Influenza and Newcastle Disease, Addlestone, Surrey, United Kingdom
- * E-mail:
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De Vleeschauwer A, Atanasova K, Van Borm S, van den Berg T, Rasmussen TB, Uttenthal Å, Van Reeth K. Comparative pathogenesis of an avian H5N2 and a swine H1N1 influenza virus in pigs. PLoS One 2009; 4:e6662. [PMID: 19684857 PMCID: PMC2722722 DOI: 10.1371/journal.pone.0006662] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Accepted: 07/15/2009] [Indexed: 12/21/2022] Open
Abstract
Pigs are considered intermediate hosts for the transmission of avian influenza viruses (AIVs) to humans but the basic organ pathogenesis of AIVs in pigs has been barely studied. We have used 42 four-week-old influenza naive pigs and two different inoculation routes (intranasal and intratracheal) to compare the pathogenesis of a low pathogenic (LP) H5N2 AIV with that of an H1N1 swine influenza virus. The respiratory tract and selected extra-respiratory tissues were examined for virus replication by titration, immunofluorescence and RT-PCR throughout the course of infection. Both viruses caused a productive infection of the entire respiratory tract and epithelial cells in the lungs were the major target. Compared to the swine virus, the AIV produced lower virus titers and fewer antigen positive cells at all levels of the respiratory tract. The respiratory part of the nasal mucosa in particular showed only rare AIV positive cells and this was associated with reduced nasal shedding of the avian compared to the swine virus. The titers and distribution of the AIV varied extremely between individual pigs and were strongly affected by the route of inoculation. Gross lung lesions and clinical signs were milder with the avian than with the swine virus, corresponding with lower viral loads in the lungs. The brainstem was the single extra-respiratory tissue found positive for virus and viral RNA with both viruses. Our data do not reject the theory of the pig as an intermediate host for AIVs, but they suggest that AIVs need to undergo genetic changes to establish full replication potential in pigs. From a biomedical perspective, experimental LP H5 AIV infection of pigs may be useful to examine heterologous protection provided by H5 vaccines or other immunization strategies, as well as for further studies on the molecular pathogenesis and neurotropism of AIVs in mammals.
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Affiliation(s)
| | - Kalina Atanasova
- Laboratory of Virology, Faculty of Veterinary Medicine Ghent University, Merelbeke, Belgium
| | - Steven Van Borm
- Avian Virology & Immunology, Veterinary & Agrochemical Research Centre, Brussels, Belgium
| | - Thierry van den Berg
- Avian Virology & Immunology, Veterinary & Agrochemical Research Centre, Brussels, Belgium
| | | | - Åse Uttenthal
- National Veterinary Institute, Technical University of Denmark, Kalvehave, Denmark
| | - Kristien Van Reeth
- Laboratory of Virology, Faculty of Veterinary Medicine Ghent University, Merelbeke, Belgium
- * E-mail:
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