Background. Group A rotaviruses (RVA) are the major cause of acute gastroenteritis in children worldwide. The nucleotide differences within the capsid protein VP7 and the spike protein VP4 permit to classify RVA strains into 27 G- and 37 P-genotypes. Although several G/P combinations have been reported, the five genotypes G1P[8], G2P[4], G3P[8], G4P[8], and G9P[8] cause most of human infections occurring worldwide. When in 2006 two RVA vaccines were licensed (Rotarix by GSK and Rotateq by Merck & Co) the Italian network for the rotavirus surveillance (RotaNet-Italia) implemented its activity to detect the possible emerging strains and genotype shifts that may occur after vaccine introduction. Objectives. This study, conducted by ISS in collaboration with the regional centre of Umbria, was aimed to investigate the circulation of different RVA describing temporal variations in the predominant viral types, and to detect the emergence of uncommon RVA of possible animal or exotic origin. Methods. From October 2006 to July 2013, 535 rotavirus positive stool samples were collected from patients with acute diarrhoea in 7 hospitals of Umbria. After viral RNA extraction, samples were genotyped for VP7 (G-type) and VP4 (P-type) genes and the aminoacid sequence was assessed, in accordance with the EuroRotaNet methods and algorithm. Results. Significant variation in the frequency of different rotavirus genotypes was observed between different years. A high percentage (80%) of virus detected belonged to common genotypes G1-G4, and G9, associated with either P[8] or P[4]. Overall, the most common rotavirus genotype detected was G1P[8] (50%), followed by G4P[8] (13%), G9P[8] (9%), G2P[4] (6%) and G3P[8] (2%) of all strains. In 12% of cases, unusual or novel strains, such as G10P[8], G6P[9] and G12P[8], were also detected, suggesting either gene reassortment events between rotaviruses of different origin or importation of strains from other countries. Mixed infections with two or more RVA strains were observed in 8% of samples. The percentage of unusual strains was found to be high, because of an outbreak caused by the G12P[8] strain occurred in Umbria during the 2012-13 season. The genetic analysis has shown a high conservation of the major antigenic sites of the VP4 and VP7 proteins between the different G12P[8] circulated in Umbria. The aminoacid sequences were found to be less conserved when compared to the vaccine strains. Conclusions. Data from seven-season surveillance conducted in Umbria confirm the genetic diversity of rotaviruses, and the possibility of circulation of unusual strains which may cause sudden outbreaks. Rotavirus surveillance is valuable to confirm appropriateness of vaccines and to control possible emergence of novel strains.
Molecular analysis of Group of Rotaviruses detected in subjects with severe acute gastroenteritis in Umbria from 2006 to 2012
CAMILLONI, Barbara;BASILEO, Michela;
2014
Abstract
Background. Group A rotaviruses (RVA) are the major cause of acute gastroenteritis in children worldwide. The nucleotide differences within the capsid protein VP7 and the spike protein VP4 permit to classify RVA strains into 27 G- and 37 P-genotypes. Although several G/P combinations have been reported, the five genotypes G1P[8], G2P[4], G3P[8], G4P[8], and G9P[8] cause most of human infections occurring worldwide. When in 2006 two RVA vaccines were licensed (Rotarix by GSK and Rotateq by Merck & Co) the Italian network for the rotavirus surveillance (RotaNet-Italia) implemented its activity to detect the possible emerging strains and genotype shifts that may occur after vaccine introduction. Objectives. This study, conducted by ISS in collaboration with the regional centre of Umbria, was aimed to investigate the circulation of different RVA describing temporal variations in the predominant viral types, and to detect the emergence of uncommon RVA of possible animal or exotic origin. Methods. From October 2006 to July 2013, 535 rotavirus positive stool samples were collected from patients with acute diarrhoea in 7 hospitals of Umbria. After viral RNA extraction, samples were genotyped for VP7 (G-type) and VP4 (P-type) genes and the aminoacid sequence was assessed, in accordance with the EuroRotaNet methods and algorithm. Results. Significant variation in the frequency of different rotavirus genotypes was observed between different years. A high percentage (80%) of virus detected belonged to common genotypes G1-G4, and G9, associated with either P[8] or P[4]. Overall, the most common rotavirus genotype detected was G1P[8] (50%), followed by G4P[8] (13%), G9P[8] (9%), G2P[4] (6%) and G3P[8] (2%) of all strains. In 12% of cases, unusual or novel strains, such as G10P[8], G6P[9] and G12P[8], were also detected, suggesting either gene reassortment events between rotaviruses of different origin or importation of strains from other countries. Mixed infections with two or more RVA strains were observed in 8% of samples. The percentage of unusual strains was found to be high, because of an outbreak caused by the G12P[8] strain occurred in Umbria during the 2012-13 season. The genetic analysis has shown a high conservation of the major antigenic sites of the VP4 and VP7 proteins between the different G12P[8] circulated in Umbria. The aminoacid sequences were found to be less conserved when compared to the vaccine strains. Conclusions. Data from seven-season surveillance conducted in Umbria confirm the genetic diversity of rotaviruses, and the possibility of circulation of unusual strains which may cause sudden outbreaks. Rotavirus surveillance is valuable to confirm appropriateness of vaccines and to control possible emergence of novel strains.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
