Increased litter survival rates, reduced clinical illness and better lactogenic immunity against TGEV in gilts that were primed as neonates with porcine respiratory coronavirus (PRCV).

Establishing immunological memory in female piglets at a young age with PRCV was effective in inducing a secondary immune response to a limiting dose of virulent TGEV given orally 13-18 days prior to farrowing. Subsequently, because of passive antibody transfer, the offspring of these primed gilts were more efficient in surviving a lethal TGEV challenge. An average survival rate of 89% occurred in 6 litters of piglets from primed gilts that were boosted with 2.8 x 10(6) plaque forming units (PFU) of TGEV whereas 76% of the piglets survived in three litters that suckled primed gilts boosted with 3.0 x 10(5)PFU of TGEV. Non-primed gilts given identical pre-farrowing doses of TGEV had litter survival rates of 63 and 55%, respectively. Moreover, both groups of litters from primed gilts suffered less clinical illness (as measured by the extent of weight loss post-challenge) than control litters. Priming of the piglets as neonates and boosting the pregnant gilts produced an anamnestic systemic immune response and correspondingly higher milk titers in the primed gilts compared to control animals. Thus, priming piglets with PRCV was beneficial in providing resistance to TGEV and could be incorporated into a vaccine strategy that yields better protection against TGEV.