Diversidad genética de norovirus y sapovirus en México

Abstract

Human caliciviruses (HuCV) include the genera sapovirus and norovirus, which are important cause of acute gastroenteritis worldwide in adults and children less than five years old. To date, the method most widely used for detection, classification and typing of HuCV strains is sequencing and subsequent phylogenetic analysis of RT-PCR products of RNA-dependent RNA polymerase (RdRp), VP1 and VP2 genes. Norovirus and sapovirus are classified into the family Caliciviridae in five genogroups (GGI to GGV) and genogroups are further divided into various numbers of genotypes, twenty seven for norovirus and six for sapovirus, being GGII-4 the norovirus genotype more common around the world. Thus, the objective of this study was to identify and characterized by molecular typing viral strains of human norovirus and sapovirus of the family Caliciviridae, associated to acute gastroenteritis in children during 2005-2006 in Mexico. In order to study the prevalence and genetic variability of the HuCVs and to determine norovirus genogroups, RT-PCR, sequencing, bioinformatics, and phylogenetic methods were used. The study material consisted of 407 negative stool samples to rotavirus obtained from children less than five years of age during October 2005 to December 2006 in Mexico. The results showed that infection by HuCVs is more common in children less than one year old in open population. Interestingly, in this study was demonstrated that infantile gastroenteritis due to HuCVs is not restricted to epidemic outbreaks, as it has been reported in other studies. A total of 125/407 (31%) of the analyzed samples were positive for HuCVs from which 51/125 (41%) were norovirus GGII and no sample was positive to norovirus GGI or a combination GGI and GGII. Phylogenetic analysis of nineteen sequences showed that most of the viral strains (18/19; 95%) belong to genotype GGII-4 and just one to GGII-3 (1/19; 5%). Thus, this study demonstrates that HuCVs are an important cause of infantile acute gastroenteritis in Mexico and permit a better understanding of the molecular epidemiology and pathogenesis of disease caused by HuCVs, allowing clearly to establish for the first time a more complete view of the frequency and circulation of these viral agents in our country.