Evaluation of a type 2 modified live porcine reproductive and respiratory syndrome vaccine against heterologous challenge of a lineage 3 highly virulent isolate in pigs

Fu-Hsiang Hou; Wei-Cheng Lee; Jiunn-Wang Liao; Maw-Sheng Chien; Chih-Jung Kuo; Han-Ping Chung; Min-Yuan Chia

doi:10.7717/peerj.8840

Evaluation of a type 2 modified live porcine reproductive and respiratory syndrome vaccine against heterologous challenge of a lineage 3 highly virulent isolate in pigs

PeerJ. 2020 Mar 30:8:e8840. doi: 10.7717/peerj.8840. eCollection 2020.

Authors

Fu-Hsiang Hou¹, Wei-Cheng Lee¹, Jiunn-Wang Liao¹, Maw-Sheng Chien¹, Chih-Jung Kuo², Han-Ping Chung², Min-Yuan Chia²

Affiliations

¹ Graduate Institute of Veterinary Pathobiology, National Chung Hsing University, Taichung City, Taiwan (ROC).
² Department of Veterinary Medicine, National Chung Hsing University, Taichung City, Taiwan (ROC).

Abstract

Porcine reproductive and respiratory syndrome (PRRS) is one of the most common diseases in the global swine industry. PRRSV is characterized by rapid mutation rates and extensive genetic divergences. It is divided into two genotypes, which are composed of several distinct sub-lineages. The purpose of the present study was to evaluate the cross-protective efficacy of Fostera PRRS MLV, an attenuated lineage 8 strain, against the heterologous challenge of a lineage 3 isolate. Eighteen pigs were randomly divided into mock, MLV and unvaccinated (UnV) groups. The pigs in the MLV group were administered Fostera PRRS vaccine at 3 weeks of age and both the MLV and UnV groups were inoculated with a virulent PRRSV isolate at 7 weeks. Clinically, the MLV group showed a shorter duration and a lower magnitude of respiratory distress than the UnV group. The average days of fever in the MLV group was 3.0 ± 0.5, which was significantly lower than the 6.2 ± 0.5 days of the UnV group (P < 0.001). The average daily weight gains of the mock, MLV and UnV groups were 781 ± 31, 550 ± 44 and 405 ± 26 g/day, respectively, during the post-challenge phase. The pathological examinations revealed that the severity of interstitial pneumonia in the MLV group was milder compared to the UnV group. Furthermore, PRRSV viremia titers in the MLV pigs were consistently lower (10¹-10^1.5 genomic copies) than those of the UnV pigs from 4 to 14 DPC. In conclusion, vaccination with Fostera PRRS MLV confers partial cross-protection against heterologous challenge of a virulent lineage 3 PRRSV isolate.

Keywords: Cross-protection; Heterologous; Modified live virus; Porcine reproductive and respiratory syndrome; Vaccine.

Grants and funding

This research was supported by Zoetis Taiwan Limited through contract research funds (Grant number 106-D-638) in the National Chung Hsing University (NCHU). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.