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An interferon inducing porcine reproductive and respiratory syndrome virus vaccine candidate elicits protection against challenge with the heterologous virulent type 2 strain VR-2385 in pigs

Research output: Contribution to journalArticle

  • Eve Fontanella
  • Zexu Ma
  • Yanjin Zhang
  • Alessandra Castro
  • Huigang Shen
  • Patrick G Halbur
  • Tanja Opriessnig

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Original languageEnglish
Pages (from-to)125-131
Issue number1
Early online date18 Nov 2016
Publication statusPublished - 3 Jan 2017


Achieving consistent protection by vaccinating pigs against porcine reproductive and respiratory syndrome virus (PRRSV) remains difficult. Recently, an interferon inducing PRRSV vaccine candidate strain A2MC2 was demonstrated to be attenuated and induce neutralizing antibodies. The objective of this study was to determine the efficacy of passage 90 of A2MC2 (A2P90) to protect pigs against challenge with moderately virulent PRRSV strain VR-2385 (92.3% nucleic acid identity with A2MC2) and highly virulent atypical PRRSV MN184 (84.5% nucleic acid identity with A2MC2). Forty 3-week old pigs were randomly assigned to five groups including a NEG-CONTROL group (non-vaccinated, non-challenged), VAC-VR2385 (vaccinated, challenged with strain VR-2385), VR2385 (challenged with strain VR-2385), VAC-MN184 (vaccinated, challenged with strain MN184) and MN184 group (challenged with MN184 virus). Vaccination was done at 3 weeks of age followed by challenge at 8 weeks of age. No viremia was detectable in any of the vaccinated pigs, however, by the time of challenge, 15/16 vaccinated pigs had seroconverted based on ELISA and had neutralizing antibodies against a homologous strain with titers ranging from 8 to 128. Infection with VR-2385 resulted in mild-to-moderate clinical disease and lesions. For VR-2385 infected pigs, vaccination significantly lowered PRRSV viremia and nasal shedding by 9 days post challenge (dpc), significantly reduced macroscopic lung lesions, and significantly increased the average daily weight gain compared to the non-vaccinated pigs. Infection with MN184 resulted in moderate-to-severe clinical disease and lesions regardless of vaccination status; however, vaccinated pigs had significantly less nasal shedding by dpc 5 compared to non-vaccinated pigs. Under the study conditions, the A2P90 vaccine strain was attenuated without detectable shedding, improved weight gain, and offered protection to the pigs challenged with VR-2385 by reduction of virus load and macroscopic lung lesions. Further work is needed to investigate different vaccination and challenge protocols, including routes, doses, timing and strains.

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