|Opriessing, T - COLLEGE OF VET MED, IA|
|Madson, D - COLLEGE OF VET MED, IA|
|Prickett, J - COLLEGE OF VET MED, IA|
|Elsener, J - FORT DODGE ANIMAL HLTH|
|Halbur, P - COLLEGE OF VET MED, IA|
Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 6, 2008
Publication Date: March 13, 2008
Citation: Opriessnig T, Madson DM, Prickett JR, Kuhar D, Lunney JK, Elsener J, Halbur PG. 2008. Effect of porcine circovirus type 2 (PCV2) vaccination on porcine reproductive and respiratory syndrome virus (PRRSV) and PCV2 coinfection. Vet. Microbiol. 131: 103-14. Interpretive Summary: Recently porcine circovirus type 2 (PCV2) associated diseases (PCVAD) have emerged as a major problem causing significant morbidity and mortality in North America pigs. The most common manifestations of PCVAD observed were severe systemic and respiratory disease. These cases typically were associated with combined infections of porcine reproductive and respiratory syndrome virus (PRRSV) present along with PCV2. Previous work has proven that PRRSV infections enhance disease in pigs experimentally coinfected with PCV2 and PRRSV. Effective control of PCVAD often depends on minimizing the effect of PCV2, PRRSV, or both. Commercial PCV2 vaccines recently became available in North America and appear to be effective in reducing losses attributed to PCVAD. Since most herds where PCV2 vaccines are being used are also infected with PRRSV it is important to accumulate information on the efficacy of PCV2 vaccines in pigs co-infected with PCV2 and PRRSV. The objectives of this study were (1) to determine if PCV2 vaccination is effective in reducing disease and lesions associated with PRRSV and PCV2 coinfection and (2) to determine if there is a difference between intradermal (ID) and intramuscular (IM) route of PCV2 vaccination. As expected, PCV2 vaccination could not eliminate the entire detrimental effect of PRRSV in coinfected pigs. There were no significant differences in the parameters measured between the two vaccination strategies indicating that both were similarly effective in reducing the effect of PCV2 in vaccinated pigs. Under the conditions of this study, PCV2 vaccination was effective in inducing a neutralizing antibody response and significantly reducing PCV2-associated lesions and PCV2 viremia in pigs coinfected with PCV2 and PRRSV. In this study, PCV2-vaccination induced a strong IgM, IgG and neutralizing antibody response in vaccinated pigs resulting in decreased amount and incidence of PCV2-DNA in sera and tissues in pigs co-infected with PCV2 and PRRSV 28 days after vaccination when compared to non-vaccinated pigs. Limited changes were found in serum cytokine levels post-challenge; however, there was no correlation of serum cytokine levels with protection against PCV2 challenge.
Technical Abstract: The objectives of this study were (1) to determine if PCV2 vaccination is effective in reducing disease and lesions associated with PRRSV and PCV2 coinfection and (2) to determine if there is a difference between intradermal (ID) and intramuscular (IM) route of PCV2 vaccination. Seventy-four, 21 day-old pigs were randomly allocated one of six groups. On day 0, pigs were vaccinated with 2 ml Suvaxyn® PCV2 One Dose (Fort Dodge Animal Health, Inc.) intramuscularly, VAC-M-COINF, or intradermal, VAC-D-COINF. On day 28, PRRSV-only, COINF, VAC-M-COINF, and VAC-D-COINF groups were inoculated intranasally with PRRSV. Similarly, PCV2-only, COINF, VAC-M-COINF, and VAC-D-COINF groups were inoculated intranasally and intramuscularly with PCV2. All pigs in all groups were necropsied on day 42. Parameters that were measured included average daily gain, rectal temperatures, PCV2 and PRRSV viremia, anti-PCV2 (IgG, IgM, and neutralizing antibodies) and anti-IgG-PRRSV antibodies, amount of PCV2 DNA and PRRSV RNA in tissues, amount of selected cytokines in serum, presence and severity of microscopic lesions in lungs and lymphoid tissues, and presence and amount of PCV2 antigen in tissues. All vaccinated pigs seroconverted to PCV2 between 14 and 28 days post vaccination as determined by significantly (P < 0.05) increased IgM, IgG, and neutralizing antibodies compared to non-vaccinated groups. After challenge, all groups inoculated with PRRSV had significantly (P < 0.001) reduced average daily gain compared to CONTROLS and PCV2-only. COINF pigs had significantly (P < 0.05) more severe lung lesions compared to VAC-M-COINF. COINF pigs had significantly (P < 0.05) higher amounts of PCV2 DNA in serum and significantly (P < 0.05) increased amount of PCV2 in lymphoid tissues compared to both vaccinated groups. IFNa levels in serum were significantly (P < 0.05) lower in CONTROLS and VAC-D-COINF groups compared to COINF pigs. In summary, under the conditions of this study, PCV2 vaccination was effective in inducing a neutralizing antibody response and significantly reducing PCV2-associated lesions and PCV2 viremia in pigs coinfected with PCV2 and PRRSV.