NoV Vaccines Research Articles

Characterization of Norovirus‐Associated Traveler's Diarrhea

Traveler's diarrhea is the most common medical complaint of international visitors to developing regions. Previous findings suggested that noroviruses (NoVs) are an underappreciated cause of traveler's diarrhea. METHODS. In the present study, we sought to define the presence of NoVs in 320 acute diarrheic stool samples collected from 299 US students who traveled to Guadalajara, Cuernavaca, or Puerto Vallarta, Mexico, during the period from 2007 through 2008. Conventional and quantitative real-time polymerase chain reaction assays were used to detect and determine NoV loads in stool samples. NoV strains were characterized by purification of viral RNA followed by sequencing of the viral capsid protein 1 gene. Sequences were compared using multiple sequence alignment, and phylogenetic trees were generated to evaluate the evolutionary relatedness of the viral strains associated with cases of traveler's diarrhea. NoV RNA was detected in 30 (9.4%) of 320 samples. Twelve strains belonged to genogroup I, and 18 strains belonged to genogroup II. NoV prevalence was higher in the winter season than in the summer season (23% vs 7%, respectively; P = .001). The cDNA viral loads of genogroup I viruses were found to be 500-fold higher than those of genogroup II strains. Phylogenetic analysis revealed a diverse population of NoV strains over different locations and years. NoV strains are important causes of traveler's diarrhea in Mexico, especially during the wintertime, and US students in Mexico may represent a suitable group for future NoV vaccine efficacy trials.

Predictors of human norovirus infection and immunity (133.52)

Abstract Noroviruses (NoV) are the main cause of epidemic gastroenteritis worldwide. We have previously shown that both an individual's secretor status (genetic) and induction of Norwalk virus-specific salivary IgA (immune) are important predictors of infection with Norwalk virus (NV). We still do not understand the factors that mediate the immune response, and infection, to Norwalk virus. To address this need, we have extended our analysis of immunological, genetic, and demographic parameters of 109 volunteers challenged with various doses of Norwalk virus through univariate and multivariate regression analyses. We found that gender, ethnicity, levels of pre-challenge NV-specific serum IgG or levels of pre-challenge NV-specific salivary IgA were not significant predictors of infection or development of a NV-specific antibody response. The presence but not magnitude of pre-challenge serum NV-specific IgG and secretor positive status were significantly associated with infection. Dose of inoculum received and age of the individual may also be predictors of infection and development of an NV-specific antibody response. We observed significant collinearity between the age of the volunteer and the presence of pre-challenge serum NV-specific IgG. Lastly, we found a strong association between levels of salivary and serum NV-specific antibody levels, after adjusting for covariates. Taken together, these data will be used to better understand the immune response to NV infection and design effective NoV vaccines to protect at risk populations including children, food handlers, and the elderly.