Interferon induction in rotavirus and coronavirus infections: a review of recent results

The interferon (IFN) response was studied in two different models of viral enteritis of the neonate. In rotavirus infected calves, IFN synthesis could be detected in the intestine and in the blood at the time of the diarrheic symptoms. A kinetic study on canulated calves suggested that systemic IFN is of intestinal origin. During TGEV infection (Transmissible gastroenteritis virus) of the newborn piglet, an acute disease which leads to 100% mortality, IFN was found at very high titres (1 000-20 000 u/ml) in the intestine, blood, urine and other organs. Intestinal IFN synthesis started some hours after the onset of diarrhea and was very transient, i.e. no more detectable two days p.i. Unlike the calf situation, IFN response in the serum lasted much longer suggesting an extra-intestinal origin. As a confirmation, piglets infected with cell-adapted strains had high levels of circulating IFN before the onset of intestinal IFN and of diarrhea. Virus and IFN were found in the lungs, due to a so far unrecognized tropism of TGEV for the macrophages. These findings indicate that the pathogenesis of TGEV is more complex than previously claimed.