Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2009
Publication Date: 11/18/2009
Citation: Kitikoon, P., Vincent, A.L., Jones, K.R., Nilubol, D., Yu, S., Janke, B.H., Thacker, B.J., Thacker, E.L. 2009. Vaccine Efficacy and Immune Response to Swine Influenza Virus Challenge in Pigs Infected with Porcine Reproductive and Respiratory Syndrome Virus at the Time of SIV-Vaccination. Veterinary Microbiology. 139(3-4):235-244. Interpretive Summary: Swine influenza virus (SIV) is an important respiratory pathogen in the swine industry. The industry currently relies heavily on vaccination to control SIV. Another important swine pathogen, porcine reproductive and respiratory syndrome virus (PRRSV), often infects pigs at the same time that influenza vaccine might be administered. PRRSV is known to modulate the immune system and has been shown to reduce the efficacy of other vaccines. This study evaluated whether PRRSV infection at the time of SIV vaccination alters the ability of the SIV vaccine to provide protection from live influenza virus challenge. Pigs infected with PRRSV during vaccination showed increased levels of pneumonia compared to pigs vaccinated in the absence of PRRSV and challenged with only SIV. The presence of PRRSV at the time of vaccination also increased clinical disease and levels of SIV nasal shedding during the acute phase of infection. No changes in systemic or local antibody response to SIV vaccination or challenge were observed. These findings demonstrate that PRRSV infection has an impact on SIV vaccine efficacy and timing of vaccination around PRRSV infection is important for respiratory disease control in growing pigs.
Technical Abstract: The objective of this study was to assess the effect of concurrent infection with porcine reproductive and respiratory syndrome virus (PRRSV) on the efficacy of an inactivated swine influenza virus (SIV) vaccine. Eight groups of pigs were used in the study. One group was infected with a virulent PRRSV isolate between the two SIV vaccines or at the time of SIV challenge. Control groups included SIV vaccination without PRRSV and pigs infected with SIV and/or PRRSV. Pigs infected with PRRSV during vaccination showed increased levels of macroscopic and microscopic lesions compared to pigs vaccinated against and challenged with only SIV. The presence of PRRSV decreased SIV vaccine efficacy as measured by increased clinical disease and levels of SIV shedding at the acute phase of infection. No alterations in systemic and local antibody response to either SIV vaccination or challenge were observed. These findings demonstrate the impact that PRRSV infection has on SIV vaccine efficacy is important for disease control.