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.
OBJECTIVE
To determine whether cell-mediated immunity against porcine reproductive and respiratory syndrome (PRRS) virus is correlated with protection against reproductive failure in sows during clinical outbreaks of PRRS in commercial herds.


METHODS
Outbreak investigation in 4 swine breeding herds.


METHODS
97 sows.


METHODS
On each farm, blood samples were collected from sows with clinical signs (abortion or increased fetal death; case sows) and from clinically normal sows (control sows). The intensity of the cell-mediated immune (CMI) response was determined by use of an interferon-gamma enzyme-linked immunospot (ELISPOT) assay. Multiple logistic regression analyses and t tests were used to compare ELISPOT assay values between case and control sows. Multiple linear regression was used to investigate associations between cell-mediated immunity and the magnitude of clinical signs.


RESULTS
In 2 farms, case sows had lower ELISPOT assay values than control sows. A negative association between the intensity of the CMI response and the number of pigs born dead per litter was detected on 1 farm. In 1 farm, no association was detected between the intensity of the CMI response and protection against reproductive failure.


CONCLUSIONS
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.
Lowe
James E
JE
Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, IL 61802, USA.
Husmann
Robert
R
Firkins
Lawrence D
LD
Zuckermann
Federico A
FA
Goldberg
Tony L
TL
D000034:Abortion, Veterinary / Q000821:virology*; D000818:Animals; D004196:Disease Outbreaks / Q000662:veterinary*; D005260:Female; D005313:Fetal Death / Q000662:veterinary* / Q000821:virology; D007111:Immunity, Cellular; D016015:Logistic Models; D019318:Porcine Reproductive and Respiratory Syndrome / Q000453:epidemiology / Q000276:immunology* / Q000517:prevention & control; D019316:Porcine respiratory and reproductive syndrome virus / Q000276:immunology*; D011247:Pregnancy; D012307:Risk Factors; D013552:Swine