Efficacy of vaccination with porcine reproductive and respiratory syndrome virus following challenges with field isolates in Japan

• Published in: Journal of Veterinary Medical Science Vol. 70; no. 10; pp. 1017 - 1025
• Main Authors: Okuda, Y.(National Federation of Agricultural Cooperative Associations, Sakura, Chiba (Japan). Inst. of Animal Health), Kuroda,M, Ono, M, Chikata, S, Shibata, I
• Format: Journal Article
• Language: English
• Published: Japan JAPANESE SOCIETY OF VETERINARY SCIENCE 01.10.2008; Japan Science and Technology Agency
• Subjects: Animals; Antibodies, Viral - blood; Antigenic Variation; Body Temperature; Body Weight; Bronchoalveolar Lavage Fluid - virology; CERDO; Enzyme-Linked Immunosorbent Assay - veterinary; EVALUACION; EVALUATION; JAPAN; JAPON; LELYSTAD VIRUS; Leukocyte Count - veterinary; Lung - virology; PORCIN; Porcine Reproductive and Respiratory Syndrome - blood; Porcine Reproductive and Respiratory Syndrome - immunology; Porcine Reproductive and Respiratory Syndrome - prevention & control; Porcine Reproductive and Respiratory Syndrome - virology; porcine reproductive and respiratory syndrome virus; Porcine respiratory and reproductive syndrome virus; Porcine respiratory and reproductive syndrome virus - genetics; Porcine respiratory and reproductive syndrome virus - immunology; PRRS; SDRP; Specific Pathogen-Free Organisms; SRRP; SWINE; VACCIN; Vaccination - veterinary; vaccine efficacy; VACCINES; VACUNA; Viral Vaccines - immunology; Viral Vaccines - therapeutic use; VIRUS DE LELYSTAD
• ISSN: 0916-7250; 1347-7439
• DOI: 10.1292/jvms.70.1017

The objective of this study was to evaluate the influences of genetic and antigenic variations in field isolates of porcine reproductive and respiratory syndrome virus (PRRSV) on vaccine efficacy. Four-week-old pigs were vaccinated with a commercial modified live virus vaccine. Four weeks after vaccination, pigs in both the vaccinated group and the non-vaccinated group were challenged intra-nasally with 10E7 TCIDsub(50) of PRRSV wt-11 (Experiment 1) or PRRSV wt-7 (Experiment 2). Based on genome sequencing of ORF5 and cross neutralization test results, PRRSV wt-11 is similar to the vaccine strain, whereas wi-7 is distinct from the vaccine strain. In the vaccinated challenged groups, clinical signs were less severe, the mean rate of weight gain was greater, and gross lung lesions were less severe when compared with the non-vaccinated challenged groups in both experiments. In Experiment 1, the virus was isolated from serum at 3 days post-challenge, and the mean virus titers in broncho-alveolar lavage fluids (BALF) and tissues were lower in pigs in the vaccinated challenged groups compared with those in the non-vaccinated challenged group. In Experiment 2, virus isolation from serum, BALF and tissues showed no significant differences between the groups. These results suggest that commercial PRRSV vaccine could be effective in reducing clinical disease following a challenge with field isolates of PRRSV. However, with regards to virological protection, the efficacy of the vaccine may be affected by the nature of the PRRSV isolates.