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The Human Respiratory Syncytial Virus (HRSV), isolated in 1955, is the main cause of hospitalization of babies and infants with respiratory illness. Several studies have been conducted worldwide aiming the development of a safe and effective vaccine against HRSV. The G2 region of glycoprotein G is used as genotyping default. In the present study, we performed a phylogenetic analysis of G protein and a comparative study between G2 region and ectodomain of attachment glycoprotein. Fifty-three nasal swab samples from children less than 5 years old and presenting symptoms of acute respiratory illness, assisted at the University Hospital (UH) of University of Sao Paulo (USP) in 2004, were submitted to sequencing by PCR and compared with GenBank sequences. We concluded that the G2 region is adequate for HRSV genotyping. The Human respiratory syncytial virus (HRSV) is an enveloped nonsegmented negative-strand RNA virus (family Paramyxoviridae, genus Pneumovirus). HRSV is the main cause of respiratory infections leading to infant hospitalization (5,14). Acute respiratory infections (ARIs) are the commonest cause of morbidity and mortality in children worldwide, and are responsible for about 30% of deaths in developing countries (12). Outbreaks of respiratory infections caused by HRSV occur yearly and previous infection do not protect against new infections although reinfections with HRSV are usually less severe (9,10). The two major groups of HRSV are classified into group A strains with GA1-GA7 (21,22) and SAA1 (31) genotypes, and group B strains with GB1-GB4 (21) and SAB1-SAB3 (31) genotypes.Most studies concerning genetic variability and evolution of attachment G protein are based on HRSV A strains (8,24,37), and there is little information available about the genetic diversity and molecular evolution of HRSV B strains (15,27,29). The predominance of HRSV A over HRSV B viruses has been attributed to the higher variability among the HRSV A strains (21,31).According to Purcell and Fergie (23), the comparison of clinical effects and the different groups and genotypes are hampered by other factors that affect the severity of infection by HRSV, such as prematurity, age of the children, and presence of other pre-existing conditions.The present study aimed to sequence the glycoprotein G gene and compare the complete sequencing of ectodomain of gene G with the G2 region, in order to identify the existence of differences in HRSV genotyping. Such information provides correct identification of HRSV genotypes, thus contributing to the development of a secure vaccine. Despite isolated more than 50 years ago, the virus is still considered an important agent of respiratory infections and hospital internments. In this scenario, a new vaccine could create new and more efficient options for prevention and treatment of infections caused by HRSV.

Human Respiratory Syncytial Virus (HRSV) is recognized as the single most important pathogen responsible for acute viral infection of the lower respiratory tract in young children. In this study, 84 samples from children under two years of age presenting acute respiratory symptoms were obtained from September 2000 to November 2001. Analysis by immunofluorescence and reverse-transcription followed by PCR, revealed that 18% (15/84) of all the samples were positive for HRSV, in which 80% (12/15) of the cases was observed in children under six months of age and the subgroups A and B co-circulated in the studied period. These are the first data obtained for Botucatu city and seasonality is evident by the higher circulation of the virus between May and July.

Human respiratory syncytial virus (HRSV) is an important respiratory pathogens among children between zero-five years old. Host immunity and viral genetic variability are important factors that can make vaccine production difficult. In this work, differences between biological clones of HRSV were detected in clinical samples in the absence and presence of serum collected from children in the convalescent phase of the illness and from their biological mothers. Viral clones were selected by plaque assay in the absence and presence of serum and nucleotide sequences of the G2 and F2 genes of HRSV biological clones were compared. One non-synonymous mutation was found in the F gene (Ile5Asn) in one clone of an HRSV-B sample and one non-synonymous mutation was found in the G gene (Ser291Pro) in four clones of the same HRSV-B sample. Only one of these clones was obtained after treatment with the child's serum. In addition, some synonymous mutations were determined in two clones of the HRSV-A samples. In conclusion, it is possible that minor sequences could be selected by host antibodies contributing to the HRSV evolutionary process, hampering the development of an effective vaccine, since we verify the same codon alteration in absence and presence of human sera in individual clones of BR-85 sample.

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