Contribution of passive immunity to porcine respiratory coronavirus to protection against transmissible gastroenteritis virus challenge exposure in suckling pigs.
OBJECTIVE
To determine the ability of porcine respiratory coronavirus (PRCV) infections to induce passive immunity in suckling pigs to transmissible gastroenteritis virus (TGEV) challenge exposure. DESIGN AND ANIMALS: 4 TGEV seronegative sows and their litters (group A) served as controls, whereas 2 other groups (B and C) of sows (also TGEV seronegative) were oronasally inoculated with live PRCV during 1 or 2 subsequent pregnancies, respectively.


METHODS
Effectiveness of passive immunity provided to pigs via colostrum and milk was assessed after TGEV challenge exposure, and TGEV antibody responses in colostrum and milk were analyzed.


RESULTS
Mortality in the 3 groups of young pigs correlated with severity of clinical signs of TGEV infection and was highest in control litters (86% in group-A pigs) and lowest in litters of sows inoculated with PRCV in 2 subsequent pregnancies (14% in group-C pigs). Virus-neutralization and IgA and IgG TGEV antibody titers of milk collected from sows at challenge exposure had significant positive correlation with litter survival. Significantly higher numbers of TGEV-specific IgA and IgG antibody-secreting cells were found in group-A pigs than in group-C pigs, suggesting that high titer of maternal antibodies (induced in group-C sows multiply exposed to PRCV) may interfere with active antibody responses.


CONCLUSIONS
Results suggest that, in PRCV-infected pig herds, multiple exposures of pregnant sows are associated with higher IgA and IgG antibody titers to TGEV in milk, and these titers contribute to protection against TGEV infection.
Sestak
K
K
Ohio Agricultural Research and Development Center, Department of Veterinary Preventive Medicine, College of Veterinary Medicine, Ohio State University, Wooster 44691, USA.
Lanza
I
I
Park
S K
SK
Weilnau
P A
PA
Saif
L J
LJ
D000818:Animals; D000833:Animals, Suckling / Q000276:immunology*; D000914:Antibodies, Viral / Q000032:analysis / Q000276:immunology; D000956:Antigens, Viral / Q000032:analysis / Q000276:immunology; D003126:Colostrum / Q000276:immunology; D017934:Coronavirus / Q000276:immunology*; D018352:Coronavirus Infections / Q000276:immunology / Q000662:veterinary; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D005761:Gastroenteritis, Transmissible, of Swine / Q000276:immunology / Q000517:prevention & control*; D007112:Immunity, Maternally-Acquired; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008892:Milk / Q000276:immunology; D011247:Pregnancy; D013552:Swine / Q000276:immunology*; D013553:Swine Diseases / Q000276:immunology; D005760:Transmissible gastroenteritis virus / Q000276:immunology
D000914:Antibodies, Viral; D000956:Antigens, Viral; D007070:Immunoglobulin A; D007074:Immunoglobulin G