Viremia and nasal and rectal shedding of rotavirus in gnotobiotic pigs inoculated with Wa human rotavirus

Abstract

Respiratory symptoms with rotavirus shedding in nasopharyngeal secretions have been reported in children with and without gastrointestinal symptoms (Zheng et al., 1991, J. Med. Virol. 34:29-37). To investigate if attenuated and virulent human rotavirus (HRV) strains cause upper respiratory tract infections or viremia in gnotobiotic pigs, we inoculated them with attenuated or virulent HRV intranasally, intravenously, or orally or via feeding tube (gavage) and assayed virus shedding. After oral or intranasal inoculation with attenuated HRV, the pigs remained asymptomatic, but 79 to 95% shed virus nasally and 5 to 17% shed virus rectally. After inoculation by gavage, no pigs shed virus nasally or rectally, but all pigs seroconverted with antibodies to HRV. No viremia was detected through postinoculation day 10. Controls inoculated intranasally with nonreplicating rotavirus-like particles or mock inoculated did not shed virus. In contrast, 100% of pigs inoculated with virulent HRV (oral, intranasal, or gavage) developed diarrhea, shed virus nasally and rectally, and had viremia. The infectivity of sera from the viremic virulent HRV-inoculated pigs was confirmed by inoculating gnotobiotic pigs orally with pooled HRV-positive serum. Serum-inoculated pigs developed diarrhea and fecal and nasal virus shedding and seroconverted with serum and intestinal HRV antibodies. Pigs inoculated intravenously with serum or intestinal contents from the viremic virulent HRV-inoculated pigs developed diarrhea, virus shedding, and viremia, similar to the orally inoculated pigs. This study provides new evidence that virulent HRV causes transient viremia and upper respiratory tract infection in addition to gastrointestinal infection in gnotobiotic pigs, confirming previous reports of rotavirus antigenemia (Blutt et al., Lancet 362:1445-1449, 2003). Our data also suggest that intestinal infection might be initiated from the basolateral side of the epithelial cells via viremia. Additionally, virus shedding patterns indicate a different pathogenesis for attenuated versus virulent HRV.

FIG. 1.

Detection of nasal and rectal shedding in gnotobiotic pigs by ELISA after inoculation with attenuated (Att) and virulent (Vir) HRV. The dashed lines represent the cutoff value of the test (ELISA = 0.08). All control values were below the cutoff value and are not shown. Symbols: ♦, nasal samples; □, rectal samples. PID, postinoculation day; PO, oral; IN, intranasal.

FIG. 2.

Detection of nasal and rectal shedding by CCIF assay in gnotobiotic pigs after inoculation with attenuated (Att) and virulent (Vir) HRV. The dashed line represents the cutoff value for the test (CCIF = 250 FFU/ml). A value of 100 FFU/ml was arbitrarily assigned to samples below the detection level of the test to be represented in the figure. All control values were below the cutoff value and are not shown. Symbols: ♦, nasal samples; □, rectal samples. PID, postinoculation day; PO, oral; IN, intranasal.

FIG. 3.

Detection of antigenemia in gnotobiotic pigs by ELISA after inoculation with HRV. The dashed line represents the cutoff value (ELISA = 0.08). All control values were below the cutoff value and are not shown. Symbols: ⧫, virulent HRV, oral; ▵, virulent HRV, gavage; □, virulent HRV, intranasal.