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Laszlofy C, Fazekas G, Barath Z, Vajo Z. Evaluation of Vaccine Immunogenicity-Correlates to Real-World Protection: Influenza. Viruses 2024; 16:441. [PMID: 38543806 PMCID: PMC10975834 DOI: 10.3390/v16030441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Revised: 02/26/2024] [Accepted: 03/11/2024] [Indexed: 05/23/2024] Open
Abstract
Recent events highlighted that, despite decades of studying vaccine immunogenicity and efforts toward finding correlates of protection, evaluating real-world vaccine efficacy as well as establishing meaningful licensing criteria still represents a significant challenge. In this paper, we review all aspects of influenza vaccine immunogenicity, including animal and human challenge studies, humoral and cellular immunity parameters, and their potential correlation with real-life protection from disease.
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Affiliation(s)
- Csaba Laszlofy
- Department of Prosthodontics, Faculty of Dentistry, University of Szeged, 6720 Szeged, Hungary; (C.L.); (Z.B.)
| | | | - Zoltan Barath
- Department of Prosthodontics, Faculty of Dentistry, University of Szeged, 6720 Szeged, Hungary; (C.L.); (Z.B.)
| | - Zoltan Vajo
- Department of Family Medicine, Semmelweis University Medical School, 1085 Budapest, Hungary
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Watanabe T, Terada T, Ezaki R, Matsuzaki M, Furusawa S, Horiuchi H. Chicken Interleukin-5 is Expressed in Splenic Lymphocytes and Affects Antigen-Specific Antibody Production. J Poult Sci 2024; 61:2024002. [PMID: 38239925 PMCID: PMC10789502 DOI: 10.2141/jpsa.2024002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 12/13/2023] [Indexed: 01/22/2024] Open
Abstract
Vaccination is important for reducing disease incidence in the poultry industry. To enhance immunity and vaccine efficacy, chicken cytokines associated with antibody production must be identified. In this study, we focused on interleukin-5 (IL-5), involved in antibody production in mice, measuring its expression and effects on antibody production. Concanavalin A-stimulated splenocytes were used for RT-PCR to clone IL5 cDNAs. Recombinant IL-5 was prepared from the clone and administered to chickens with antigen via the ocular-topical route twice every alternate week. IL-5 enhanced antigen-specific IgY and inhibited antigen-specific serum IgA production in serum. Our findings suggest that IL-5 plays an important role in chicken antibody production, with possible unique functions.
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Affiliation(s)
- Tenkai Watanabe
- Laboratory of Immunobiology, Graduate School of Integrated
Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528,
Japan
| | - Takumi Terada
- Laboratory of Immunobiology, Graduate School of Integrated
Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528,
Japan
| | - Ryo Ezaki
- Laboratory of Immunobiology, Graduate School of Integrated
Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528,
Japan
| | - Mei Matsuzaki
- Laboratory of Immunobiology, Graduate School of Integrated
Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528,
Japan
| | - Syuichi Furusawa
- Laboratory of Immunobiology, Graduate School of Integrated
Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528,
Japan
| | - Hiroyuki Horiuchi
- Laboratory of Immunobiology, Graduate School of Integrated
Sciences for Life, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528,
Japan
- Genome Editing Innovation Center, Hiroshima University,
3-10-23 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-0046, Japan
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Three-Dimensional Analysis of the Nasolacrimal Duct and Nasal Cavity and Arrangement of Mucosal Tissue in Chickens. J Poult Sci 2020; 57:303-309. [PMID: 33132731 PMCID: PMC7596029 DOI: 10.2141/jpsa.0190091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The nasal mucosa plays an important role in the immune system, with nasal mucous cells secreting mucin that, along with pili, exclude foreign substances from intervening. Nasal mucosal-associated lymphoid tissue (NALT), present in the nasal lamina propria, acts as a local immune system. In birds, the Harderian gland in the orbit also plays an important role in the local immune system. In this study, we analyzed the pathway from the nasolacrimal duct to the nasal cavity in chickens and the distribution of the nasal mucous cells responsible for defense mechanisms against pathogens. To determine the three-dimensional structure of the pathway from the nasolacrimal duct to the nasal cavity, we made casts of the anatomy by injecting an acrylic resin into the area. We then prepared paraffin sections to determine the distribution of the NALT and mucous cells. The mucous gland was clearly seen in the mucosal epithelium of the nasal cavity, suggesting that the pathway along the nasal cavity develops a nonspecific immune system to deal with large foreign substances, such as bacteria, using mucins that are secreted from the mucous glands. Hence, there is not only a physical barrier but also an antibacterial activity. Unlike in other animals, morphologically, the nasolacrimal duct in chicken becomes the ventral nasal meatus and opens into the choanae in the caudal portion of the nasal cavity. NALT was prominently present in the lamina propria of the ventral nasal meatus, suggesting the presence of a specific immune system protecting against avian viruses. Thus, responses to vaccine stimulation could be developed from tissues along the pathway of the ventral nasal meatus via the nasolacrimal duct running from the punctum. These morphological studies suggest that the instillation of eye drops could be used as an efficient vaccination method for avoiding respiratory diseases.
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Alkie TN, Yitbarek A, Taha-Abdelaziz K, Astill J, Sharif S. Characterization of immunogenicity of avian influenza antigens encapsulated in PLGA nanoparticles following mucosal and subcutaneous delivery in chickens. PLoS One 2018; 13:e0206324. [PMID: 30383798 PMCID: PMC6211703 DOI: 10.1371/journal.pone.0206324] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 10/10/2018] [Indexed: 02/07/2023] Open
Abstract
Mucosal vaccine delivery systems have paramount importance for the induction of mucosal antibody responses. Two studies were conducted to evaluate immunogenicity of inactivated AIV antigens encapsulated in poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs). In the first study, seven groups of specific pathogen free (SPF) layer-type chickens were immunized subcutaneously at 7-days of age with different vaccine formulations followed by booster vaccinations two weeks later. Immune responses were profiled by measuring antibody (Ab) responses in sera and lachrymal secretions of vaccinated chickens. The results indicated that inactivated AIV and CpG ODN co-encapsulated in PLGA NPs (2x NanoAI+CpG) produced higher amounts of hemagglutination inhibiting antibodies compared to a group vaccinated with non-adjuvanted AIV encapsulated in PLGA NPs (NanoAI). The tested adjuvanted NPs-based vaccine (2x NanoAI+CpG) resulted in higher IgG responses in the sera and lachrymal secretions at weeks 3, 4 and 5 post-vaccination when immunized subcutaneously. The incorporation of CpG ODN led to an increase in Ab-mediated responses and was found useful to be included both in the prime and booster vaccinations. In the second study, the ability of chitosan and mannan coated PLGA NPs that encapsulated AIV and CpG ODN was evaluated for inducing antibody responses when delivered via nasal and ocular routes in one-week-old SPF layer-type chickens. These PLGA NPs-based and surface modified formulations induced robust AIV-specific antibody responses in sera and lachrymal secretions. Chitosan coated PLGA NPs resulted in the production of large quantities of lachrymal IgA and IgG compared to mannan coated NPs, which also induced detectable amounts of IgA in addition to the induction of IgG in lachrymal secretions. In both mucosal and subcutaneous vaccination approaches, although NPs delivery enhanced Ab-mediated immunity, one booster vaccination was required to generate significant amount of Abs. These results highlight the potential of NPs-based AIV antigens for promoting the induction of both systemic and mucosal immune responses against respiratory pathogens.
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Affiliation(s)
- Tamiru Negash Alkie
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
- Department of Biology, Wilfrid Laurier University, Waterloo, Canada
| | - Alexander Yitbarek
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Khaled Taha-Abdelaziz
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
- Pathology Department, Faculty of Veterinary Medicine, Beni-Suef University, Al Shamlah, Beni-Suef, Egypt
| | - Jake Astill
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
| | - Shayan Sharif
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada
- * E-mail:
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Prime-boost vaccination strategy against avian influenza and Newcastle disease viruses reduces shedding of the challenge viruses. Virusdisease 2018; 29:324-332. [PMID: 30159367 DOI: 10.1007/s13337-018-0463-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Accepted: 06/02/2018] [Indexed: 01/10/2023] Open
Abstract
In the present study, we carried-out assessment of efficacy of different immunization strategies using two bivalent vaccine formulations containing antigens of inactivated Newcastle disease virus (NDV-genotype VIId) and reassortant highly pathogenic avian influenza virus (H5N1-HPAIV) mixed with Montanide ISA71 and Montanide Gel02 as adjuvants. The efficacy of the prepared vaccines was evaluated by determining the cellular and humoral immune responses. In addition, protection against H5N1-AIV and NDV-genotype VIId challenge viruses post vaccination was assessed when Montanide-Gel02 based vaccine was inoculated in 10-days-old specific pathogen free chicks intraocularly once, twice or once followed by a boost with the Montanide ISA71 based vaccine. The cytokines profile analysis demonstrated that the prime-boost strategy induced the highest up-regulation in interferon-gamma (11.39-fold change) and interleukin-6 (14.12-fold change) genes expression. Also, enhanced lymphocytes proliferation was recorded beside increased antibody titers with protection levels reaching 50 and 60% against H5N1 and NDV challenge; respectively. Immunization with Montanide ISA71 inactivated vaccine induced 80% protection; however, the prime-boost combination afforded complete protection (100%) in the challenged chickens against mortality, clinical signs and virus shedding. Finally, these results highlight the significance of considering not only different vaccine platforms but also vaccination strategies to maximize protection against AIV and NDV with regards to the longevity of the vaccine-induced immune response.
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Takaki H, Sato H, Kurata R, Hikono H, Hiono T, Kida H, Matsumoto M, Saito T, Seya T. Cytokine responses to eye spray adjuvants for enhancing vaccine-induced immunity in chickens. Microbiol Immunol 2017; 60:511-5. [PMID: 27240729 DOI: 10.1111/1348-0421.12391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Revised: 05/24/2016] [Accepted: 05/26/2016] [Indexed: 11/30/2022]
Abstract
Eye spray influenza vaccines for chickens are increasingly available; however, how to enhance cellular and antibody responses to them remains undetermined. Here, eye-drops containing the immune-enhancing adjuvants Pam2CSK4 or polyI:C were assessed in chickens. Application of these TLR agonists to chicken conjunctiva resulted in up-regulation of IL-1β, but not other cytokines, including IFN and IL-6, in the spleen, lung and Harderian gland. Thus, responses to adjuvant applied to the conjunctival mucosa of chickens differ from those expected from the responses to intra-nasal adjuvants in mammals. Identifying an appropriate delivery route for adjuvants is crucial for evoking immune responses in chickens.
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Affiliation(s)
- Hiromi Takaki
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine
| | - Haruko Sato
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine
| | - Riho Kurata
- National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Hirokazu Hikono
- National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Takahiro Hiono
- Department of Disease Control, Hokkaido University Graduate School of Veterinary Medicine
| | - Hiroshi Kida
- Research Center for Zoonosis Control, Hokkaido University, Kita-ku, Sapporo
| | - Misako Matsumoto
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine
| | - Takehiko Saito
- National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Tsukasa Seya
- Department of Microbiology and Immunology, Hokkaido University Graduate School of Medicine
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Sato H, Oshiumi H, Takaki H, Hikono H, Seya T. Evolution of the DEAD box helicase family in chicken: chickens have no DHX9 ortholog. Microbiol Immunol 2015; 59:633-40. [DOI: 10.1111/1348-0421.12322] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 09/09/2015] [Accepted: 09/14/2015] [Indexed: 11/28/2022]
Affiliation(s)
- Haruko Sato
- Department of Microbiology and Immunology; Hokkaido University Graduate School of Medicine; Kita-ku Sapporo 060-8638
| | - Hiroyuki Oshiumi
- Department of Microbiology and Immunology; Hokkaido University Graduate School of Medicine; Kita-ku Sapporo 060-8638
| | - Hiromi Takaki
- Department of Microbiology and Immunology; Hokkaido University Graduate School of Medicine; Kita-ku Sapporo 060-8638
| | - Hirokazu Hikono
- National Institute of Animal Health; National Agriculture and Food Research Organization (NARO); Tsukuba 305-8642 Japan
| | - Tsukasa Seya
- Department of Microbiology and Immunology; Hokkaido University Graduate School of Medicine; Kita-ku Sapporo 060-8638
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Kim ED, Han SJ, Byun YH, Yoon SC, Choi KS, Seong BL, Seo KY. Inactivated Eyedrop Influenza Vaccine Adjuvanted with Poly(I:C) Is Safe and Effective for Inducing Protective Systemic and Mucosal Immunity. PLoS One 2015; 10:e0137608. [PMID: 26355295 PMCID: PMC4565664 DOI: 10.1371/journal.pone.0137608] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Accepted: 08/19/2015] [Indexed: 01/08/2023] Open
Abstract
The eye route has been evaluated as an efficient vaccine delivery routes. However, in order to induce sufficient antibody production with inactivated vaccine, testing of the safety and efficacy of the use of inactivated antigen plus adjuvant is needed. Here, we assessed various types of adjuvants in eyedrop as an anti-influenza serum and mucosal Ab production-enhancer in BALB/c mice. Among the adjuvants, poly (I:C) showed as much enhancement in antigen-specific serum IgG and mucosal IgA antibody production as cholera toxin (CT) after vaccinations with trivalent hemagglutinin-subunits or split H1N1 vaccine antigen in mice. Vaccination with split H1N1 eyedrop vaccine antigen plus poly(I:C) showed a similar or slightly lower efficacy in inducing antibody production than intranasal vaccination; the eyedrop vaccine-induced immunity was enough to protect mice from lethal homologous influenza A/California/04/09 (H1N1) virus challenge. Additionally, ocular inoculation with poly(I:C) plus vaccine antigen generated no signs of inflammation within 24 hours: no increases in the mRNA expression levels of inflammatory cytokines nor in the infiltration of mononuclear cells to administration sites. In contrast, CT administration induced increased expression of IL-6 cytokine mRNA and mononuclear cell infiltration in the conjunctiva within 24 hours of vaccination. Moreover, inoculated visualizing materials by eyedrop did not contaminate the surface of the olfactory bulb in mice; meanwhile, intranasally administered materials defiled the surface of the brain. On the basis of these findings, we propose that the use of eyedrop inactivated influenza vaccine plus poly(I:C) is a safe and effective mucosal vaccine strategy for inducing protective anti-influenza immunity.
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Affiliation(s)
- Eun-Do Kim
- Department of Ophthalmology, Eye and Ear Hospital, Severance Hospital, Institute of Vision Research, Yonsei University College of Medicine, Seoul, Republic of Korea; Brain Korea 21 Project for Medical Science, Yonsei University, Seoul, Republic of Korea
| | - Soo Jung Han
- Department of Ophthalmology, Eye and Ear Hospital, Severance Hospital, Institute of Vision Research, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Young-Ho Byun
- Department of Biotechnology, College of Engineering, Yonsei University, Seoul, Republic of Korea; Vaccine Translational Research Center, Yonsei University, Seoul, Republic of Korea
| | - Sang Chul Yoon
- Department of Ophthalmology, Eye and Ear Hospital, Severance Hospital, Institute of Vision Research, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Kyoung Sub Choi
- The Graduate School of Yonsei University, Seoul, Republic of Korea; Department of Ophthalmology, National Health Insurance Corporation Ilsan Hospital, Gyounggi-do, Republic of Korea
| | - Baik Lin Seong
- Department of Biotechnology, College of Engineering, Yonsei University, Seoul, Republic of Korea; Vaccine Translational Research Center, Yonsei University, Seoul, Republic of Korea
| | - Kyoung Yul Seo
- Department of Ophthalmology, Eye and Ear Hospital, Severance Hospital, Institute of Vision Research, Yonsei University College of Medicine, Seoul, Republic of Korea
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St. Paul M, Brisbin JT, Barjesteh N, Villaneueva AI, Parvizi P, Read LR, Nagy É, Sharif S. Avian Influenza Virus Vaccines Containing Toll-Like Receptors 2 and 5 Ligand Adjuvants Promote Protective Immune Responses in Chickens. Viral Immunol 2014; 27:160-6. [DOI: 10.1089/vim.2013.0129] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Michael St. Paul
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Jennifer T. Brisbin
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Neda Barjesteh
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Alexander Ian Villaneueva
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Payvand Parvizi
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Leah R. Read
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Éva Nagy
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Shayan Sharif
- Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
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Yang S, Niu S, Guo Z, Yuan Y, Xue K, Liu S, Jin H. Cross-protective immunity against influenza A/H1N1 virus challenge in mice immunized with recombinant vaccine expressing HA gene of influenza A/H5N1 virus. Virol J 2013; 10:291. [PMID: 24053449 PMCID: PMC3848947 DOI: 10.1186/1743-422x-10-291] [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: 06/20/2013] [Accepted: 09/16/2013] [Indexed: 11/30/2022] Open
Abstract
Background Influenza virus undergoes constant antigenic evolution, and therefore influenza vaccines must be reformulated each year. Time is necessary to produce a vaccine that is antigenically matched to a pandemic strain. A goal of many research works is to produce universal vaccines that can induce protective immunity to influenza A viruses of various subtypes. Despite intensive studies, the precise mechanisms of heterosubtypic immunity (HSI) remain ambiguous. Method In this study, mice were vaccinated with recombinant virus vaccine (rL H5), in which the hemagglutinin (HA) gene of influenza A/H5N1 virus was inserted into the LaSota Newcastle disease virus (NDV) vaccine strain. Following a challenge with influenza A/H1N1 virus, survival rates and lung index of mice were observed. The antibodies to influenza virus were detected using hemagglutination inhibition (HI). The lung viral loads, lung cytokine levels and the percentages of both IFN-γ+CD4+ and IFN-γ+CD8+ T cells in spleen were detected using real-time RT-PCR, ELISA and flow cytometry respectively. Results In comparison with the group of mice given phosphate-buffered saline (PBS), the mice vaccinated with rL H5 showed reductions in lung index and viral replication in the lungs after a challenge with influenza A/H1N1 virus. The antibody titer in group 3 (H1N1-H1N1) was significantly higher than that in other groups which only low levels of antibody were detected. IFN-γ levels increased in both group 1 (rL H5-H1N1) and group 2 (rL H5 + IL-2-H1N1). And the IFN-γ level of group 2 was significantly higher than that of group 1. The percentages of both IFN-γ+CD4+ and IFN-γ+CD8+ T cells in group 1 (rL H5-H1N1) and group 2 (rL H5 + IL-2-H1N1) increased significantly, as measured by flow cytometry. Conclusion After the mice were vaccinated with rL H5, cross-protective immune response was induced, which was against heterosubtypic influenza A/H1N1 virus. To some extent, cross-protective immune response can be enhanced by IL-2 as an adjuvant. Cellular immune responses may play an important role in HSI against influenza virus.
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Affiliation(s)
- Song Yang
- Department of Pathogen Biology, China Medical University, Shenyang, Liaoning, PR China.
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Protection of Chinese painted quails (Coturnix chinensis) against a highly pathogenic H5N1 avian influenza virus strain after vaccination. Arch Virol 2013; 158:2577-81. [PMID: 23771736 PMCID: PMC3830747 DOI: 10.1007/s00705-013-1754-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 04/27/2013] [Indexed: 12/02/2022]
Abstract
Chinese painted quails immunized with a single dose (6 μg HA) of inactivated H5N1 (clade 1) influenza vaccine NIBRG-14 and challenged with 100 LD50 of the heterologous A/Swan/Nagybaracska/01/06(H5N1) (clade 2.2) strain were protected, whereas unvaccinated quails died after challenge. No viral antigens or RNA were detected in cloacal swabs from immunized animals. Sera obtained post-immunization gave low titres in serological assays against the vaccine and the challenge viruses. Our results demonstrate the protective efficacy of the NIBRG-14 strain against the challenge virus and the usefulness of these small birds in protection studies of influenza vaccines.
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