Serum and intestinal isotype antibody responses to Wa human rotavirus in gnotobiotic pigs are modulated by maternal antibodies

The effects of passive antibodies on protection and active immune responses to human rotavirus were studied in gnotobiotic pigs. Pigs were injected at birth with saline or sow serum of high (immunized) or low (control) antibo dy titre and subsets of pigs were fed colostrum and milk from immunized or control sows. Pigs were inoculated at 3-5 days of age and challenged at 21 days post-inoculation (p.i.) with virulent Wa human rotavirus. Pigs receivi ng immune serum with or without immune colostrum/milk were partially protec ted against diarrhoea and virus shedding after inoculation, but had signifi cantly lower IgA antibody titres in serum and small intestinal contents at 21 days p.i. and lower protection rates after challenge compared with pigs given control or no maternal antibodies. IgG antibody titres were consisten tly higher in small than in large intestinal contents. Pigs given control s erum with control colostrum/milk had lower rates of virus shedding after in oculation than those given control serum alone. In summary, high titres of circulating maternal antibodies with or without local (milk) antibodies pro vided passive protection after inoculation but suppressed active mucosal an tibody responses. These findings may have implications for the use of live, oral rotavirus vaccines in breast-fed infants.