Phylogenetic Analysis of Human Astrovirus Infection among Children Suffering from Gastroenteritis Referred to Aboozar Hospital, Ahvaz, Iran

ne of the most common illnesses that have its great impact on children and the elderly is acute viral gastroenteritis (1). After rotavirus human astrovirus may be the second most common cause of viral gastroenteritis in children (2, 3). Human astrovirus (HAstV) is a member of Astroviridae family which contains a single genus, Astrovirus. These viruses are nonenveloped with single stranded positive sense RNA genome (4). The genome of astrovirus is about 7 kb in size and consists of three ORF: ORF1a and ORF1b which encode non structural proteins and ORF2 which encode the precursor of capsid protein (5). All eight known human astrovirus serotypes belonging to the first identified human astrovirus species (HAstV) (6). A second species of astrovirus was found in a child with diarrhea and named AstV-MLB (7). In our best knowledge, genotypes and the strains of HAstV circulating in Iran have not been reported. In our previous study, the relative frequency of astrovirus, seasonal distribution and the patients age range in children suffering from gastroenteritis was reported (8), the aim of the study was to understand the phylogenetic distribution of human astrovirus strains in children suffering from gastroenteritis. Fecal specimens were taken from children less than five years old with gastroenteritis, referred to Ahvaz, Aboozar hospital. Diagnosis tests to determination of parasitic and microbial infection were done and negative specimens were kept at -80°C. Hundred eighty four specimens were tested for the presence of astroviral infection. Extraction of viral RNA from fecal suspensions and RT-PCR procedure was performed (8), and for clean-up and Nucleotide sequencing, ten out of 29 detected HAstV were selected to analyze the circulating strains pattern. The positive samples were sequenced using the PRISM 377 automatic DNA sequencer (Applied Biosystems, Foster City, CA). The nucleotide sequences obtained from ORF1a were aligned with HAstV sequences from GenBank database by using the CLUSTAL X program (version 1.83). Phylogenetic analysis was done by the Maximum Likelihood method in MEGA software (version 5.2.2), with Kimura-two parameter model. All HAstV sequences were submitted to the GenBank database under the following accession numbers: JX171281 to JX171290. The phylogenetic analysis revealed that most of Ahvaz human astrovirus strains reported in this study had little divergence amongst them in selected region of ORF1a. Nine of them were grouped in to HAst8 taxon in a clade O