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Amadori M, Listorti V, Razzuoli E. Reappraisal of PRRS Immune Control Strategies: The Way Forward. Pathogens 2021; 10:pathogens10091073. [PMID: 34578106 PMCID: PMC8469074 DOI: 10.3390/pathogens10091073] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/06/2021] [Accepted: 08/14/2021] [Indexed: 11/16/2022] Open
Abstract
The control of porcine reproductive and respiratory syndrome (PRRS) is still a major issue worldwide in the pig farming sector. Despite extensive research efforts and the practical experience gained so far, the syndrome still severely affects farmed pigs worldwide and challenges established beliefs in veterinary virology and immunology. The clinical and economic repercussions of PRRS are based on concomitant, additive features of the virus pathogenicity, host susceptibility, and the influence of environmental, microbial, and non-microbial stressors. This makes a case for integrated, multi-disciplinary research efforts, in which the three types of contributing factors are critically evaluated toward the development of successful disease control strategies. These efforts could be significantly eased by the definition of reliable markers of disease risk and virus pathogenicity. As for the host's susceptibility to PRRSV infection and disease onset, the roles of both the innate and adaptive immune responses are still ill-defined. In particular, the overt discrepancy between passive and active immunity and the uncertain role of adaptive immunity vis-à-vis established PRRSV infection should prompt the scientific community to develop novel research schemes, in which apparently divergent and contradictory findings could be reconciled and eventually brought into a satisfactory conceptual framework.
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Affiliation(s)
- Massimo Amadori
- Italian Network of Veterinary Immunology, 25125 Brescia, Italy
- Correspondence:
| | - Valeria Listorti
- Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, 16129 Genoa, Italy; (V.L.); (E.R.)
| | - Elisabetta Razzuoli
- Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d’Aosta, 16129 Genoa, Italy; (V.L.); (E.R.)
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Ferlazzo G, Ruggeri J, Boniotti MB, Guarneri F, Barbieri I, Tonni M, Bertasio C, Alborali GL, Amadori M. In vitro Cytokine Responses to Virulent PRRS Virus Strains. Front Vet Sci 2020; 7:335. [PMID: 32760741 PMCID: PMC7373743 DOI: 10.3389/fvets.2020.00335] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 05/13/2020] [Indexed: 12/16/2022] Open
Abstract
Porcine reproductive and respiratory syndrome (PRRS) affects farmed swine causing heavy direct and indirect losses. The infections sustained by PRRS viruses (PRRSV-1 and PRRSV-2) may give rise to severe clinical cases. This highlights the issue of PRRSV pathogenicity and relevant markers thereof. Since PRRSV strains can be discriminated in terms of immunotypes, we aimed to detect possible correlates of virulence in vitro based on the profile of innate immune responses induced by strains of diverse virulence. To this purpose, 10 field PRRSV isolates were investigated in assays of innate immune response to detect possible features associated with virulence. Tumor necrosis factor-α, interleukin (IL)-1beta, IL-8, IL-10, and caspase-1 were measured in cultures of PRRSV-treated peripheral blood mononuclear cells of PRRS-naive pigs, unable to support PRRSV replication. Two reference PRRSV strains (highly pathogenic and attenuated, respectively), were included in the screening. The PRRSV strains isolated from field cases were shown to vary widely in terms of inflammatory cytokine responses in vitro, which were substantially lacking with some strains including the reference, highly pathogenic one. In particular, neither the field PRRSV isolates nor the reference highly pathogenic strain gave rise to an IL-1beta response, which was consistently induced by the attenuated strain, only. This pattern of response was reversed in an inflammatory environment, in which the attenuated strain reduced the ongoing IL-1beta response. Results indicate that some pathogenic PRRSV strains can prevent a primary inflammatory response of PBMCs, associated with reduced permissiveness of mature macrophages for PRRSV replication in later phases.
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Affiliation(s)
- Gianluca Ferlazzo
- Laboratory of Animal Welfare, Clinical Chemistry and Veterinary Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Jessica Ruggeri
- Laboratory of Animal Welfare, Clinical Chemistry and Veterinary Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Maria Beatrice Boniotti
- Genomics Department, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Flavia Guarneri
- Laboratory of Animal Welfare, Clinical Chemistry and Veterinary Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Ilaria Barbieri
- Genomics Department, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Matteo Tonni
- Diagnostic Laboratory, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Cristina Bertasio
- Genomics Department, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Giovanni Loris Alborali
- Diagnostic Laboratory, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
| | - Massimo Amadori
- Laboratory of Animal Welfare, Clinical Chemistry and Veterinary Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Brescia, Italy
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Díaz I, Genís-Jorquera B, Martín-Valls GE, Mateu E. Using commercial ELISAs to assess humoral response in sows repeatedly vaccinated with modified live porcine reproductive and respiratory syndrome virus. Vet Rec 2019; 186:123. [PMID: 31575761 DOI: 10.1136/vr.105432] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 08/13/2019] [Accepted: 08/25/2019] [Indexed: 11/04/2022]
Abstract
BACKGROUND Sows in breeding herds are often mass vaccinated against porcine reproductive and respiratory syndrome (PRRS) every few months using modified live vaccines (MLV). Field veterinarians repeatedly report that multiple vaccinated sows test negative in ELISA. Obviously, this creates uncertainty when assessing the compliance of vaccination and the status of sows. METHODS In the present study, four commercial ELISAs were used to assess the serological PRRS status in gilts and sows of three farms that were PRRS MLV vaccinated every four months. Animals were tested before vaccination (BV) and postvaccination (PV). Total and neutralising antibodies and cell-mediated responses were also measured in animals that yielded negative results in all ELISAs. RESULTS The proportion of seronegative animals BV varied depending on the farm and the ELISA used. When samples were analysed using only one ELISA, a substantial number of negative results obtained BV remained as negative afterwards. Five animals were negative BV and PV with all the examined ELISAs. Those animals also yielded negative results in all the other immunological assays. CONCLUSION Our findings suggest that the use of ELISA for monitoring multiple PRRS MLV vaccinated sows is very limited due to the variability of the humoral responses and the moderate agreement between tests.
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Affiliation(s)
- Ivan Díaz
- IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Bellaterra, Spain
| | | | - Gerard E Martín-Valls
- Departament de Sanitat i Anatomia Animals, Facultat Veterinària, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Enric Mateu
- IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Bellaterra, Spain.,Departament de Sanitat i Anatomia Animals, Facultat Veterinària, Universitat Autònoma de Barcelona, Bellaterra, Spain
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Comparative evaluation of immune responses of swine in PRRS-stable and unstable herds. Vet Immunol Immunopathol 2018; 200:32-39. [PMID: 29776610 DOI: 10.1016/j.vetimm.2018.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 04/11/2018] [Accepted: 04/15/2018] [Indexed: 11/24/2022]
Abstract
Porcine Reproductive and Respiratory Syndrome (PRRS) is an elusive model of host/virus relationship in which disease is determined by virus pathogenicity, pig breed susceptibility and phenotype, microbial infectious pressure and environmental conditions. Successful disease control in PRRS-endemic Countries corresponds to "stability", i.e. a condition with no clinical signs of PRRS in the breeding-herd population and no viremia in weaning-age pigs. The aim of this work was to compare the profile and time-course of humoral and cell-mediated immunity in stable and unstable herds, respectively. In particular, we investigated PRRS virus (PRRSV) in serum and group oral fluid samples by Real-time RT-PCR, PRRSV-specific IgA and IgG in oral fluids, serum IgG antibody and the cell-mediated response (PRRSV-specific release of interferon-gamma) in whole blood samples. These parameters were measured in order to identify possible discrepancies in the development and kinetics of the immune response against PRRSV. PRRS-free gilts got regularly infected after entering PRRS-stable and unstable farms. In an open cycle, unstable pig farm PRRSV infection could be demonstrated in all groups of pigs, including suckling piglets. Four main results should be highlighted: A) the precocity of the Ab response in group oral fluids was generally similar to that recorded in sera; B) circulation of PRRSV was consistently detected in all age groups in the unstable herds, as opposed to the stable ones; C) an early, balanced, IgA and IgG response in oral fluids was only observed in the stable herds; D) an early IFN-gamma response after PRRSV infection was often observed in stable herds, as opposed to the unstable ones. These were characterized by IFN-gamma responses in piglets, likely due to transfer of maternal immunity. Most important, the mucosal IgA response was associated with cessation of virus excretion in oral fluid samples of PRRS-unstable herds. The above findings indicate that a peculiar profile of immune response to PRRSV can be found in PRRS-stable herds. Therefore, the outlined immune parameters can represent a useful readout system to evaluate successful adaptation to PRRSV based on acclimatization of breeding animals and management of pig flow.
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Eck M, Durán MG, Ricklin ME, Locher S, Sarraseca J, Rodríguez MJ, McCullough KC, Summerfield A, Zimmer G, Ruggli N. Virus replicon particles expressing porcine reproductive and respiratory syndrome virus proteins elicit immune priming but do not confer protection from viremia in pigs. Vet Res 2016; 47:33. [PMID: 26895704 PMCID: PMC4761149 DOI: 10.1186/s13567-016-0318-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 01/29/2016] [Indexed: 01/17/2023] Open
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of one of the most devastating and economically significant viral disease of pigs worldwide. The vaccines currently available on the market elicit only limited protection. Recombinant vesicular stomatitis virus (VSV) replicon particles (VRP) have been used successfully to induce protection against influenza A virus (IAV) in chickens and bluetongue virus in sheep. In this study, VSV VRP expressing the PRRSV envelope proteins GP5, M, GP4, GP3, GP2 and the nucleocapsid protein N, individually or in combination, were generated and evaluated as a potential vector vaccine against PRRSV infection. High level expression of the recombinant PRRSV proteins was demonstrated in cell culture. However, none of the PRRSV antigens expressed from VRP, with the exception of the N protein, did induce any detectable antibody response in pigs before challenge infection with PRRSV. After challenge however, the antibody responses against GP5, GP4 and GP3 appeared in average 2 weeks earlier than in pigs vaccinated with the empty control VRP. No reduction of viremia was observed in the vaccinated group compared with the control group. When pigs were co-vaccinated with VRP expressing IAV antigens and VRP expressing PRRSV glycoproteins, only antibody responses to the IAV antigens were detectable. These data show that the VSV replicon vector can induce immune responses to heterologous proteins in pigs, but that the PRRSV envelope proteins expressed from VSV VRP are poorly immunogenic. Nevertheless, they prime the immune system for significantly earlier B-cell responses following PRRSV challenge infection.
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Affiliation(s)
- Melanie Eck
- Institute of Virology and Immunology IVI, Sensemattstrasse 293, 3147, Mittelhäusern, Switzerland. .,Graduate School for Cellular and Biomedical Sciences, University of Bern, 3012, Bern, Switzerland.
| | - Margarita García Durán
- Inmunología y Genética aplicada, S.A. (INGENASA), Calle de Los Hermanos García Noblejas 39, 28037, Madrid, Spain.
| | - Meret E Ricklin
- Institute of Virology and Immunology IVI, Sensemattstrasse 293, 3147, Mittelhäusern, Switzerland.
| | - Samira Locher
- Institute of Virology and Immunology IVI, Sensemattstrasse 293, 3147, Mittelhäusern, Switzerland.
| | - Javier Sarraseca
- Inmunología y Genética aplicada, S.A. (INGENASA), Calle de Los Hermanos García Noblejas 39, 28037, Madrid, Spain.
| | - María José Rodríguez
- Inmunología y Genética aplicada, S.A. (INGENASA), Calle de Los Hermanos García Noblejas 39, 28037, Madrid, Spain.
| | - Kenneth C McCullough
- Institute of Virology and Immunology IVI, Sensemattstrasse 293, 3147, Mittelhäusern, Switzerland.
| | - Artur Summerfield
- Institute of Virology and Immunology IVI, Sensemattstrasse 293, 3147, Mittelhäusern, Switzerland. .,Department of Infectious Disease and Pathobiology, Vetsuisse Faculty, University of Bern, Länggassstrasse 122, 3001, Bern, Switzerland.
| | - Gert Zimmer
- Institute of Virology and Immunology IVI, Sensemattstrasse 293, 3147, Mittelhäusern, Switzerland.
| | - Nicolas Ruggli
- Institute of Virology and Immunology IVI, Sensemattstrasse 293, 3147, Mittelhäusern, Switzerland.
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Mokhtar H, Pedrera M, Frossard JP, Biffar L, Hammer SE, Kvisgaard LK, Larsen LE, Stewart GR, Somavarapu S, Steinbach F, Graham SP. The Non-structural Protein 5 and Matrix Protein Are Antigenic Targets of T Cell Immunity to Genotype 1 Porcine Reproductive and Respiratory Syndrome Viruses. Front Immunol 2016; 7:40. [PMID: 26909080 PMCID: PMC4755262 DOI: 10.3389/fimmu.2016.00040] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 01/26/2016] [Indexed: 01/01/2023] Open
Abstract
The porcine reproductive and respiratory syndrome virus (PRRSV) is the cause of one of the most economically important diseases affecting swine worldwide. Efforts to develop a next-generation vaccine have largely focused on envelope glycoproteins to target virus-neutralizing antibody responses. However, these approaches have failed to demonstrate the necessary efficacy to progress toward market. T cells are crucial to the control of many viruses through cytolysis and cytokine secretion. Since control of PRRSV infection is not dependent on the development of neutralizing antibodies, it has been proposed that T cell-mediated immunity plays a key role. Therefore, we hypothesized that conserved T cell antigens represent prime candidates for the development a novel PRRS vaccine. Antigens were identified by screening a proteome-wide synthetic peptide library with T cells from cohorts of pigs rendered immune by experimental infections with a closely related (subtype 1) or divergent (subtype 3) PRRSV-1 strain. Dominant T cell IFN-γ responses were directed against the non-structural protein 5 (NSP5), and to a lesser extent, the matrix (M) protein. The majority of NSP5-specific CD8 T cells and M-specific CD4 T cells expressed a putative effector memory phenotype and were polyfunctional as assessed by coexpression of TNF-α and mobilization of the cytotoxic degranulation marker CD107a. Both antigens were generally well conserved among strains of both PRRSV genotypes. Thus, M and NSP5 represent attractive vaccine candidate T cell antigens, which should be evaluated further in the context of PRRSV vaccine development.
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Affiliation(s)
- Helen Mokhtar
- Virology Department, Animal and Plant Health Agency, Addlestone, UK; Department of Microbial and Cellular Sciences, University of Surrey, Guildford, UK
| | - Miriam Pedrera
- Virology Department, Animal and Plant Health Agency , Addlestone , UK
| | | | - Lucia Biffar
- Virology Department, Animal and Plant Health Agency , Addlestone , UK
| | - Sabine E Hammer
- Department of Pathobiology, Institute of Immunology, University of Veterinary Medicine Vienna , Vienna , Austria
| | - Lise K Kvisgaard
- National Veterinary Institute, Technical University of Denmark , Frederiksberg , Denmark
| | - Lars E Larsen
- National Veterinary Institute, Technical University of Denmark , Frederiksberg , Denmark
| | - Graham R Stewart
- Department of Microbial and Cellular Sciences, University of Surrey , Guildford , UK
| | | | - Falko Steinbach
- Virology Department, Animal and Plant Health Agency , Addlestone , UK
| | - Simon P Graham
- Virology Department, Animal and Plant Health Agency , Addlestone , UK
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Trus I, Frydas IS, Reddy VRAP, Bonckaert C, Li Y, Kvisgaard LK, Larsen LE, Nauwynck HJ. Immunity raised by recent European subtype 1 PRRSV strains allows better replication of East European subtype 3 PRRSV strain Lena than that raised by an older strain. Vet Res 2016; 47:15. [PMID: 26742636 PMCID: PMC4705580 DOI: 10.1186/s13567-015-0292-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 12/10/2015] [Indexed: 11/20/2022] Open
Abstract
Stable spatial distribution of porcine reproductive and respiratory syndrome (PRRSV)-1 subtypes in Europe is accompanied by a strong population immunity induced by local PRRSV strains. In the present study, it was examined if the immunity induced by three West European subtype 1 PRRSV strains (2007 isolate 07V063 and 2013 isolates 13V091 and 13V117) offers protection against the highly virulent East European subtype 3 PRRSV strain Lena. The number of fever days was greater (p < 0.05) in the control group (7.6 ± 1.7 days) compared to the immune groups (07V063-immune: 4.0 ± 1.2 days, 13V091-immune: 4.6 ± 1.1 days, 13V117-immune: 4.0 ± 2.9 days). In all groups, protection was characterized by reduction (p < 0.05) of AUC values of nasal shedding (control: 14.6, 07V063-immune: 3.4, 13V091-immune: 8.9, 13V117-immune: 8.0) and viremia (control: 28.1, 07V063-immune: 5.4, 13V091-immune: 9.0, 13V117-immune: 8.3). Reduction of respiratory disease, nasal shedding (mean AUC and mean peak values) and viremia (mean AUC and mean peak values) was more pronounced in 07V063-immune (p < 0.05) than in 13V091-immune and 13V117-immune animals. Inoculation with subtype 1 PRRSV strains caused priming of the Lena-specific virus neutralization antibody response. Upon challenge with Lena, we observed a very strong serological booster effect for neutralizing antibodies against strains used for the first inoculation. Our results indicate that inoculation with subtype 1 PRRSV strains can partially protect against antigenically divergent subtype 3 strains. The lower protection level elicited by recently isolated subtype 1 PRRSV strains may impair the outcome of the spatial expansion of subtype 3 strains from East Europe to West Europe.
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Affiliation(s)
- Ivan Trus
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Ilias S Frydas
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Vishwanatha R A P Reddy
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Caroline Bonckaert
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Yewei Li
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Lise K Kvisgaard
- National Veterinary Institute, Technical University of Denmark, Frederiksberg C, Denmark.
| | - Lars E Larsen
- National Veterinary Institute, Technical University of Denmark, Frederiksberg C, Denmark.
| | - Hans J Nauwynck
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
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Renukaradhya GJ, Meng XJ, Calvert JG, Roof M, Lager KM. Inactivated and subunit vaccines against porcine reproductive and respiratory syndrome: Current status and future direction. Vaccine 2015; 33:3065-72. [PMID: 25980425 DOI: 10.1016/j.vaccine.2015.04.102] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 04/18/2015] [Accepted: 04/30/2015] [Indexed: 02/07/2023]
Abstract
Within a few years of its emergence in the late 1980s, the PRRS virus had spread globally to become the foremost infectious disease concern for the pork industry. Since 1994, modified live-attenuated vaccines against porcine reproductive and respiratory syndrome virus (PRRSV-MLV) have been widely used, but have failed to provide complete protection against emerging and heterologous field strains of the virus. Moreover, like many other MLVs, PRRSV-MLVs have safety concerns including vertical and horizontal transmission of the vaccine virus and several documented incidences of reversion to virulence. Thus, the development of efficacious inactivated vaccines is warranted for the control and eradication of PRRS. Since the early 1990s, researchers have been attempting to develop inactivated PRRSV vaccines, but most of the candidates have failed to elicit protective immunity even against homologous virus challenge. Recent research findings relating to both inactivated and subunit candidate PRRSV vaccines have shown promise, but they need to be pursued further to improve their heterologous efficacy and cost-effectiveness before considering commercialization. In this comprehensive review, we provide information on attempts to develop PRRSV inactivated and subunit vaccines. These includes various virus inactivation strategies, adjuvants, nanoparticle-based vaccine delivery systems, DNA vaccines, and recombinant subunit vaccines produced using baculovirus, plant, and replication-deficient viruses as vector vaccines. Finally, future directions for the development of innovative non-infectious PRRSV vaccines are suggested. Undoubtedly there remains a need for novel PRRSV vaccine strategies targeted to deliver cross-protective, non-infectious vaccines for the control and eradication of PRRS.
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Affiliation(s)
- Gourapura J Renukaradhya
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH, United States.
| | - Xiang-Jin Meng
- Department of Biomedical Sciences and Pathobiology, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
| | | | - Michael Roof
- Boehringer Ingelheim Vetmedica, Inc., Ames, IA, United States
| | - Kelly M Lager
- Virology Swine Research Unit, National Animal Disease Center, U.S. Department of Agriculture, Ames, IA, United States.
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Amadori M, Razzuoli E. Immune Control of PRRS: Lessons to be Learned and Possible Ways Forward. Front Vet Sci 2014; 1:2. [PMID: 26664910 PMCID: PMC4668844 DOI: 10.3389/fvets.2014.00002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 05/19/2014] [Indexed: 12/29/2022] Open
Abstract
Porcine reproductive and respiratory syndrome (PRRS) is an elusive model of host/virus relationship in which disease is determined by virus pathogenicity, pig breed susceptibility and phenotype, microbial infectious pressure, and environmental conditions. The disease can be controlled by farm management programs, which can be supported by vaccination or conditioning of animals to circulating PRRS virus (PRRSV) strains. Yet, PRRS still represents a cause of heavy losses for the pig industry worldwide. Immunological control strategies are often compounded by poor and late development of adaptive immunity in both vaccinated and infected animals. Also, there is evidence that results of field trials can be worse than those of experimental studies in isolation facilities. Neutralizing antibody (NA) was shown to prevent PRRSV infection. Instead, the role of NA and adaptive immunity on the whole in virus clearance after established PRRSV infections is still contentious. Pigs eventually eliminate PRRSV infection, which may be correlated with an “educated,” innate immune response, which may also develop following vaccination. In addition to vaccination, an immunomodulation strategy for PRRS can be reasonably advocated in pig “problem” farms, where a substantial control of disease prevalence and disease-related losses is badly needed. This is not at odds with vaccination, which should be preferably restricted to PRRSV-free animals bound for PRRSV-infected farm units. Oral, low-dose, interferon-α treatments proved effective on farm for the control of respiratory and reproductive disease outbreaks, whereas the results were less clear in isolation facilities. Having in mind the crucial interaction between PRRSV and bacterial lipopolysaccharides for occurrence of respiratory disease, the strong control actions of low-dose type I interferons on the inflammatory response observed in vitro and in vivo probably underlie the rapid clinical responses observed in field trials.
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Affiliation(s)
- Massimo Amadori
- Laboratory of Cellular Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna , Brescia , Italy
| | - Elisabetta Razzuoli
- Laboratory of Cellular Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna , Brescia , Italy
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Tang D, Liu J, Li C, Zhang H, Ma P, Luo X, Zeng Z, Hong N, Liu X, Wang B, Wang F, Gan Z, Hao F. Positive effects of porcine IL-2 and IL-4 on virus-specific immune responses induced by the porcine reproductive and respiratory syndrome virus (PRRSV) ORF5 DNA vaccine in swine. J Vet Sci 2013; 15:99-109. [PMID: 24136204 PMCID: PMC3973771 DOI: 10.4142/jvs.2014.15.1.99] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 07/09/2013] [Indexed: 01/24/2023] Open
Abstract
The purpose of this study was to investigate the effects of porcine interleukin (IL)-2 and IL-4 genes on enhancing the immunogenicity of a porcine reproductive and respiratory syndrome virus ORF5 DNA vaccine in piglets. Eukaryotic expression plasmids pcDNA-ORF5, pcDNA-IL-2, and pcDNA-IL-4 were constructed and then expressed in Marc-145 cells. The effects of these genes were detected using an indirect immunofluorescent assay and reverse transcription polymerase chain reaction (RT-PCR). Characteristic fluorescence was observed at different times after pcDNA-ORF5 was expressed in the Marc-145 cells, and PCR products corresponding to ORF5, IL-2, and IL-4 genes were detected at 48 h. Based on these data, healthy piglets were injected intramuscularly with different combinations of the purified plasmids: pcDNA-ORF5 alone, pcDNA-ORF5 + pcDNA-IL-2, pcDNA-ORF5 + pcDNA-IL-4, and pcDNA-ORF5 + pcDNAIL-4 + pcDNA-IL-2. The ensuing humoral immune responses, percentages of CD4+ and CD8+ T lymphocytes, proliferation indices, and interferon-γ expression were analyzed. Results revealed that the piglets co-immunized with pcDNA-ORF5 + pcDNA-IL-4 + pcDNA-IL-2 plasmids developed significantly higher antibody titers and neutralizing antibody levels, had significantly increased levels of specific T lymphocyte proliferation, elevated percentages of CD4+ and CD8+ T lymphocytes, and significantly higher IFN-γ production than the other inoculated pigs (p < 0.05).
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Affiliation(s)
- Deyuan Tang
- Department of Animal Science, Guizhou University, Guiyang 550025,
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