Correlation of cell-mediated immunity against porcine reproductive and respiratory syndrome virus with protection against reproductive failure in sows during outbreaks of porcine reproductive and respiratory syndrome in commercial herds

Abstract

Evidence that a strong CMI response was correlated with protection against clinical PRRS was detected in 3 of 4 farms. However, farms and sows within farms varied considerably in their immune responsiveness and in the degree to which they were protected clinically. Increasing cell-mediated immunity within infected herds has the potential to decrease clinical reproductive disease, but only if the sources of intra- and interfarm variation in the intensity of cell-mediated immunity to PRRS virus can be identified.

Pathogenicity of three type 2 porcine reproductive and respiratory syndrome virus strains in experimentally inoculated pregnant gilts

“…This is noteworthy, as no other detailed reports on cytokine responses to PRRSV infection in pregnant sows or gilts exist. In contrast to our findings, Lowe et al (2005) found that a strong cell-mediated immune response determined by use of an IFN␥ ELISPOT was correlated with protection against reproductive failure in three of four farms during outbreaks of PRRS. However, direct comparison with the results of the present study are difficult because the Lowe et al study measured IFN␥ levels by ELISPOT in sows expressing clinical signs from chronically PRRSVinfected farms, 7 months to 5 years post introduction, in which the specific timing of infection or prior exposure status of individual animals was unknown.…”

Differential immunity in pigs with high and low responses to porcine reproductive and respiratory syndrome virus infection1,2

“…With a sow-model, Lowe et al (2005) found that genetics may affect the rate of PRRSV-induced abortions, possibly due to levels of circulating IFNG secreting cells. Our data indicate that early postinfection (4 dpi) increases in serum IFNG may be associated with resistance.…”

“…Breeds and lines of pigs responded differently to infection with PRRSV (Halbur et al, 1998;Lowe et al, 2005;Petry et al, 2005;Vincent et al, 2006), indicating genetic variation exists. However, because most nucleus swine breeding populations are maintained with very high health status, selection for resistance to many pathogens that seriously affect commercial herds using quantitative methods may not be practical.…”

Comparative Measurement of Cell-Mediated Immune Responses of Swine to the M and N Proteins of Porcine Reproductive and Respiratory Syndrome Virus

“…The T cell-mediated immune responses represented by IFN-␥ are important in the control of PRRSV infections (1,23). The study established with the PRRSV-modified live vaccines has also suggested that cell-mediated immune responses are the primary protective mechanism (47).…”

“…However, it has become evident that T cell-mediated immunity is essential for effective protection against PRRSV (25,47). The increased cellular immunity was significantly related to the reduced clinical symptoms in PRRSV-infected piglets and sows (17,23). Analysis of the T-cell responses to the structural proteins of PRRSV indicated that the M protein may perform a major role in the induction of cellular immunity in infected pigs (2).…”