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Seven commercial immunochromatographic assays intended for the detection of group A rotavirus antigens in human stool samples were evaluated. These assays showed similar levels of diagnostic accuracy and were suitable for the detection of rotavirus in patients with acute gastroenteritis but missed some asymptomatic rotavirus shedding identified by real-time reverse transcription-PCR.

Norovirus (NoV) is one of the main causative agents of acute gastroenteritis worldwide. In temperate climates, outbreaks peak during the winter season. The mechanism by which climatic factors influence the occurrence of NoV outbreaks is unknown. We hypothesized that humidity is linked to NoV seasonality. Human NoV is not cultivatable, so we used cultivatable murine norovirus (MNV) as a surrogate to study its persistence when exposed to various levels of relative humidity (RH) from low (10% RH) to saturated (100% RH) conditions at 9 and 25°C. In addition, we conducted similar experiments with virus-like particles (VLPs) from the predominant GII-4 norovirus and studied changes in binding patterns to A, B, and O group carbohydrates that might reflect capsid alterations. The responses of MNV and VLP to humidity were somewhat similar, with 10 and 100% RH exhibiting a strong conserving effect for both models, whereas 50% RH was detrimental for MNV infectivity and VLP binding capacity. The data analysis suggested that absolute humidity (AH) rather than RH is the critical factor for keeping NoV infectious, with an AH below 0.007 kg water/kg air being favorable to NoV survival. Retrospective surveys of the meteorological data in Paris for the last 14 years showed that AH average values have almost always been below 0.007 kg water/kg air during the winter (i.e., 0.0046 ± 0.0014 kg water/kg air), and this finding supports the fact that low AH provides an ideal condition for NoV persistence and transmission during cold months.

Aichi virus has been described as a novel causative agent of gastroenteritis in humans. In this study, we report the seroprevalence distribution of Aichi virus in Tunisia. A panel of 1,000 sera was screened by applying an enzyme-linked immunosorbent assay for immunoglobulin G specific for Aichi virus. A considerable prevalence (92%) of antibody to Aichi virus was found across all age groups. The specific anti-Aichi virus antibodies increased with age, from a high rate (68.8%) in children under 10 years old to about 100% in persons more than 60 years old. We found a statistically significant increase in levels of antibody to Aichi virus according to the age of patients. Immunoglobulin M antibodies were detected among five children. A high frequency of Aichi virus monoinfections in hospitalized children with severe gastroenteritis was previously observed in Tunisia. Aichi virus causes diarrhea with dehydration, fever, and vomiting. This work is the first to establish a correlation between the high seroprevalence of specific Aichi virus antibodies, clinical presentation, and a high frequency of isolation of Aichi virus by genomic characterization in stools of children suffering from gastroenteritis. Our data show the importance and emerging character of Aichi virus in the viral etiology of pediatric gastroenteritis.

Aichi virus has been associated with acute gastroenteritis in adults and children. Stool samples were collected from 788 Tunisian children suffering from diarrhea. Aichi virus was found in 4.1% of the cases. The high proportion of monoinfections and the high frequency of hospitalizations support the role of Aichi virus in pediatric gastroenteritis.

The circulation of enteric viruses among the population of Cairo, Egypt, between March 2006 and February 2007 was studied. At least one virus was detected in 50% of fecal samples, 57.4% of which were positive for rotavirus, 26% for norovirus, 10.4% for adenovirus, and 1.7% for astrovirus. Over 10% of infections were mixed infections. Rotavirus typing showed that G1P[8] and G2P[4] were predominant but that the unusual G12P[4] and G12P[6] reassortants were also present. Among the noroviruses, half belonged to the predominant GGII.4 cluster. The phylogenetic analysis of the capsid gene suggested that GGII.4 strains from Cairo were similar to those circulating elsewhere. It also showed the emergence of new GGII.4 variants that were not associated with any previously known GGII.4 isolate. Further studies are required to assess the disease burden of enteric viruses in Egypt and the impact of atypical strains.

Human metapneumovirus (hMPV) is associated with respiratory tract infections among children and adults. Because hMPV induces significant morbidity and mortality in the elderly, a model of hMPV infection in aged BALB/c mice was established. Young (8 weeks old) and aged (18 months old) mice were intranasally inoculated with hMPV. The infected mice showed respiratory dysfunction, as measured by plethysmography, a marked loss in weight (up to 24%), and severe histopathological abnormalities including bronchiolitis obliterans organizing pneumonia. However, clinical severity was far higher in the aged mice, and none of the young infected mice died. Although virus replication in the lung was greater in the older mice, clearance of virus was not delayed compared to young mice. Production of virus-specific antibody as well as neutralizing antibody was lower. Gamma interferon and monocyte chemotactic protein-1 levels in bronchoalveolar lavage fluid were significantly lower in older mice, whereas interleukin-6 and interleukin-4 levels were significantly higher. We observed by flow cytometry a significant increase in the CD4 + T lymphocytes ( P < 0.05) of the aged mice and no difference in CD8 + T-cell recruitment to the respiratory tract between the two groups. The present study investigated the effects of aging on the immunopathogenesis of hMPV infection and suggests that CD4 + T lymphocytes, the cytokine response, or a defect in humoral response may be associated with the increased disease severity observed in the aged mice.

Human noroviruses (NoVs) cause epidemic and endemic acute gastroenteritis in children and adults. To study the prevalence and genetic diversity of NoV in children in Tunisia, a total of 788 fecal samples were collected during a 4-year period in the region of Monastir, from children 12 years of age or younger, hospitalized or presenting in dispensaries with symptoms of acute gastroenteritis. NoV was detected by reverse transcription-PCR and confirmed by sequence analysis. This is the first report that describes the molecular epidemiology of NoV in Tunisian children: NoVs were characterized as the causative agent in 128 (16.2%) of the samples. Fourteen samples contained a mixture of two NoVs, and 33 samples were coinfected with additional enteric viruses. Eight distinct NoV genotypes were detected (GGI.2, GGI.4, GGII.1, GGII.4, GGII.8, GGII.14, GGIIb/GGII.2, and GGIIb/GGII.3). GGII.4 was the most prevalent genotype, accounting for 83 (64.8%) cases. Interestingly the GGII.4 variant Hunter, described as spreading all over the world in 2004, was found in Tunisia as early as January 2003. The delay of 1 year between the isolation in Tunisia and the worldwide emergence is somewhat surprising, considering the importance of the contacts between North Africa and Europe particularly. Nevertheless, this illustrates the idea that sporadic gastroenteritis cases may be a reservoir for emerging epidemic NoV strains.

Virus-like particles of Dijon171/96 virus, a genogroup II norovirus, were expressed in a baculovirus system and were used for a seroepidemiological study of 1,078 age-stratified human sera collected in Dijon, France. The results showed a seroprevalence of 74.1%. Furthermore, we showed that murine antibodies generated against recombinant Dijon171/96 virus, and human antibodies recognized discontinuous epitopes on the particles.

As a first step to gain insight into the structure of the rotavirus virion at atomic resolution, we report here the expression, purification, and crystallization of recombinant rotavirus protein VP6. This protein has the property of polymerizing in the form of tubular structures in solution which have hindered crystallization thus far. Using a combination of electron microscopy and small-angle X-ray scattering, we found that addition of Ca 2+ at concentrations higher than 100 mM results in depolymerization of the tubes, leading to an essentially monodisperse solution of trimeric VP6 even at high protein concentrations (higher than 10 mg/ml), thereby enabling us to search for crystallization conditions. We have thus obtained crystals of VP6 which diffract to better than 2.4 Å resolution and belong to the cubic space group P4 1 32 with a cell dimension a of 160 Å. The crystals contain a trimer of VP6 lying along the diagonal of the cubic unit cell, resulting in one VP6 monomer per asymmetric unit and a solvent content of roughly 70%.

Noroviruses are important etiologic agents of acute gastroenteritis and show great genetic diversity. To characterize more fully previously detected strains that could not be assigned unequivocally to one particular genotype based on the RNA polymerase, we have sequenced a region in the capsid gene and, in some cases, in the junction between open reading frame 1 (ORF1) and ORF2. The results allowed us to identify several recombinant noroviruses: GGIIb viruses were detected for the first time in France in August 2000 and then spread through France and to Europe during the following winter. Here we present the characterization of three other probable GII recombinants which showed different phylogenetic positions depending on their ORF1 and ORF2 sequences. Analysis of the region located between ORF1 and ORF2 by a nucleotide identity window search showed a sudden shift in similarities. Moreover, recombination breakpoints were identified upstream and downstream of the beginning of ORF2 by using a statistical test, thus confirming the involvement of this region in recombination. Unlike GGIIb, the three recombinants described here do not seem to have diffused widely in the community: one was found in a waterborne outbreak, and the other two were found in sporadic cases. Recombination is important for the evolution of RNA viruses and has already been described for noroviruses. Our results suggest that recombination is not a rare phenomenon among noroviruses, but not all these presumed recombinants that formed during RNA replication are able to spread widely.

This work describes the design and initial evaluation of a commercial test allowing the detection of noroviruses and sapoviruses by reverse transcription-PCR (RT-PCR) in a single tube followed by microplate hybridization, as well as the detection of PCR inhibitors. The test was shown to be broadly reactive (except for Melksham-like strains), sensitive, and specific and thus should be useful for calicivirus detection in clinical practice.