We previously characterized the pathogenesis of two host-specific bovine enteric caliciviruses (BEC), the GIII.2 norovirus (NoV) strain CV186-OH and the phylogenetically unassigned NB strain, in gnotobiotic (Gn) calves. In this study we evaluated the Gn calf as an alternative animal model to study the pathogenesis and host immune responses to the human norovirus (HuNoV) strain GII.4-HS66. The HuNoV HS66 strain caused diarrhea (five/five calves) and intestinal lesions (one/two calves tested) in the proximal small intestine (duodenum and jejunum) of Gn calves, with lesions similar to, but less severe than, those described for the Newbury agent 2 (NA-2) and NB BEC.

To understand the role of cytokines during rotavirus infection, we assessed the kinetics of tumor necrosis factor alpha (TNF-␣) and interleukin-6 (IL-6) (proinflammatory) ,

We evaluated virus-specific B and T cell responses induced by the attenuated Wa (P1A[8]G1) human rotavirus (AttHRV) oral 2-dose vaccine with or without Lactobacillus acidophilus (LA) colonization in neonatal gnotobiotic (Gn) pigs. The AttHRV vaccinated and LA-fed pigs had a significantly higher magnitude of HRV-specific IFN-gamma producing CD8+ T cell responses in ileum and spleen, IgA and IgG antibody-secreting cell responses in ileum, and serum IgM, IgA and IgG antibody and virus neutralizing antibody titers compared to the AttHRV vaccinated pigs without LA colonization. These findings suggest that L. acidophilus has significant immunopotentiating effects and may be used as a safe oral adjuvant for rotavirus vaccines in neonates.

We examined rotavirus-specific IFN-γ producing CD4+, CD8+ and CD4+CD8+ T cell responses in gnotobiotic pigs infected with a virulent human rotavirus (VirHRV) or vaccinated with an attenuated (Att) HRV vaccine (AttHRV3x or AttHRV2x) or an AttHRV oral priming and 2/6-virus-like particle (VLP) intranasal boosting (AttHRV-2/6VLP) regimen. In VirHRV infected pigs, HRV-specific IFN-γ producing T cells reside primarily in ileum. AttHRV-2/6VLP induced similar frequencies of intestinal IFN-γ producing T cells as the VirHRV, whereas AttHRV3x or 2x vaccines were less effective. Protection rates against rotavirus diarrhea upon VirHRV challenge significantly correlated (r = 0.97-1.0, p < 0.005) with frequencies of intestinal IFN-γ producing T cells, suggesting their role in protective immunity.

Group A rotaviruses are the most common cause of dehydrating diarrhea in infants and young children worldwide, with more than 2 million hospitalizations yearly and approximately 440,000 deaths. It is estimated that 82% of rotavirus deaths occur in children in the poorest countries (23). Rotavirus transmission occurs mainly by the fecal-oral route, although respiratory transmission has been suggested to occur (7).Rotavirus infection was thought to be limited to the gastrointestinal tract. However, respiratory symptoms and rotavirus shedding in nasopharyngeal secretions have been reported in children with and without gastrointestinal symptoms (19,26,42). Rotavirus antigen was detected in the lung of 1 of 13 experimentally infected 3-week-old conventional pigs at postinoculation day 2 (30) and in liver and kidney specimens from immunodeficient children (9). Rotavirus RNA has also been detected in cerebrospinal fluid and blood of children with central nervous system disease (20,34). Recently, Blutt and colleagues (2) detected rotavirus antigenemia in the serum of children, mice, rabbits, and calves. They further demonstrated that serum from infected mice induced rectal rotavirus antigen shedding after oral inoculation of rotavirus-negative adult mice with the serum. Previously, another enteric virus, the porcine enteric calicivirus (PEC), has also been associated with transient viremia (infectious virus in serum) after oral inoculation of gnotobiotic pigs (11).We choose gnotobiotic pigs because they constitute an animal model of HRV-induced disease. Their gastrointestinal tract physiology and their development of mucosal immunity resemble that of humans. These similarities with HRV infections of infants allow us to establish correlations which could be applied for rotavirus vaccine development (14,25) The question addressed in our study was whether an attenuated human rotavirus and virulent HRV causes upper respiratory tract infections or viremia in naïve neonatal gnotobiotic pigs after various routes of inoculation. In this study we evaluated nasal and rectal virus shedding and viremia after oral, intranasal, feeding tube (gavage), and intravenous inoculation of neonatal gnotobiotic pigs with the Wa strain of attenuated HRV or virulent HRV. The presence of infectious virus in serum of gnotobiotic pigs after oral inoculation with Wa HRV was also investigated by oral and intravenous reinoculation of gnotobiotic pigs with a pool of the HRV-positive sera. MATERIALS AND METHODSVirus. The attenuated cell culture-adapted Wa strain HRV (P1A [8]G1), derived from the 27th HRV passage in African Green monkey kidney cells (MA104) and the virulent Wa HRV from pooled intestinal contents of gnotobiotic pigs were used for inoculation of the gnotobiotic pigs at doses of 5 ϫ 10 7