Impact of a modified-live porcine reproductive and respiratory syndrome virus vaccine intervention on a population of pigs infected with a heterologous isolate

• Published in: Vaccine 2007-05, Vol.25 (22), p.4382-4391
• Main Authors: Cano, Jean Paul, Dee, Scott A, Murtaugh, Michael P, Pijoan, Carlos
• Format: Article
• Language: English
• Subjects: Allergy and Immunology; Animals; Antibodies, Viral - blood; Applied microbiology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Genetic diversity; Heterologous infection; Hogs; Infections; Mass vaccination; Microbiology; Miscellaneous; MLV vaccine; Mortality; Population; Porcine Reproductive and Respiratory Syndrome - immunology; Porcine Reproductive and Respiratory Syndrome - physiopathology; Porcine Reproductive and Respiratory Syndrome - prevention & control; Porcine Reproductive and Respiratory Syndrome - virology; Porcine respiratory and reproductive syndrome virus; Porcine respiratory and reproductive syndrome virus - classification; Porcine respiratory and reproductive syndrome virus - immunology; Porcine respiratory and reproductive syndrome virus - isolation & purification; Porcine respiratory and reproductive syndrome virus - pathogenicity; PRRSV; RNA, Viral - blood; Swine; Vaccination - veterinary; Vaccines; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects); Viral infections; Viral Load; Viral Vaccines - administration & dosage; Viral Vaccines - genetics; Viral Vaccines - immunology; Viremia - immunology; Viremia - prevention & control; Viremia - virology; Virology; Virulence
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2007.03.031

Abstract The objectives of this study were to evaluate the effects of a therapeutic vaccine intervention with a modified-live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine on the dynamics of a heterologous viral infection in a population of pigs, and to determine the clinical and virological response of previously exposed and vaccinated pigs against a second virulent heterologous challenge. A population of 320 pigs were infected with a field isolate, PRRSV MN-30100, alone or followed by Ingelvac® PRRS MLV vaccine administered one to three times at 30 days intervals beginning 1 week after infection. Vaccine intervention reduced the duration of viral shedding, but did not reduce the viral load in tissues or the proportion of persistently infected pigs. A different and highly virulent field isolate, MN-184, was then given as a heterologous viral challenge at 97 days after first exposure. Previously infected and vaccinated pigs showed a significant reduction in clinical signs and enhanced weight gain after the highly virulent challenge with PRRSV MN-184, but infection with and shedding of the challenge isolate were not prevented.