Molecular characterization of VP4 and NSP4 genes from rotavirus strains infecting neonates and young children in Belém, Brazil

Genotyping and Molecular Characterization of VP6 and NSP4 Genes of Unusual Rotavirus Group A Isolated from Children with Acute Gastroenteritis

Group A rotavirus (RVA), which causes acute gastroenteritis (AGE) in children worldwide, is categorized mainly based on VP7 (genotype G) and VP4 (genotype P) genes. Genotypes that circulate at <1% are considered unusual. Important genes also include VP6 (genotype I) and NSP4 (genotype E). VP6 establishes the group and affects immunogenicity, while NSP4, as an enterotoxin, is responsible for the clinical symptoms. The aim of this study was to genotype the VP6 and NSP4 genes and molecularly characterize the NSP4 and VP6 genes of unusual RVA. Unusual RVA strains extracted from fecal samples of children ≤16 years with AGE were genotyped in VP6 and NSP4 genes with Sanger sequencing. In a 15-year period (2007-2021), 54.8% (34/62) of unusual RVA were successfully I and E genotyped. Three different I and E genotypes were identified; I2 (73.5%, 25/34) and E2 (35.3%, 12/34) were the most common. E3 genotype was detected from 2017 onwards. The uncommon combination of I2-E3 was found in 26.5% (9/34) of the strains and G3-P[9]-I2-E3 remained the most frequent G-P-I-E combination (20.6%, 7/34). Children infected with RVA E2 strains had a statistically higher frequency of dehydration (50%) than those infected with RVA E3 strains (p = 0.019). Multiple substitutions were detected in NSP4, but their functional effect remains unknown. The result indicates the genetic diversity of RVA strains. Continuous surveillance of the RVA based on the whole genome will provide better knowledge of its evolution.

Detection of a novel species A, DS-1-like, G4P[6] rotavirus strain from a Brazilian child with gastroenteritis

Rotaviruses belonging to species A (RVA) remain among the most common causes of severe gastroenteritis in children aged <5 years, leading to substantial morbidity and mortality worldwide. Genome reassortment events between two human strains or human and animal strains represent one of the mechanisms which appear to generate the broad genetic variability of circulating. According to a nucleotide, sequence-based classification system, RVA strains are currently classified into three genotype constellations including Wa-like (genogroup I), DS-1-like (genogroup II), and AU-like (genogroup III). The present study reports the detection of an unusual RVA G4P[6] strain (coded as strain HSE005), which might have originated from a natural reassortment event between human and animal RVA strains. Molecular characterization of this isolate showed that it belonged to genogroup II, genotype G4P[6]. In addition, two genes (VP3 and NSP4) of this strain denoted evidence of reassortment events involving strains of distinct zoonotic evolutionary origins. Therefore, we propose that a new G4P[6] strain was identified, highlighting a possible first zoonotic transmission including a reassortment event that involved the VP3 gene.

The Impact of Human Genetic Polymorphisms on Rotavirus Susceptibility, Epidemiology, and Vaccine Take

Innate resistance to viral infections can be attributed to mutations in genes involved in the immune response, or to the receptor/ligand. A remarkable example of the latter is the recently described Mendelian trait resistance to clinically important and globally predominating genotypes of rotavirus, the most common agent of severe dehydrating gastroenteritis in children worldwide. This resistance appears to be rotavirus genotype-dependent and is mainly mediated by histo-blood group antigens (HBGAs), which function as a receptor or attachment factors on gut epithelial surfaces. HBGA synthesis is mediated by fucosyltransferases and glycosyltransferases under the genetic control of the FUT2 (secretor), FUT3 (Lewis), and ABO (H) genes on chromosome 19. Significant genotypic and phenotypic diversity of HBGA expression exists between different human populations. This genetic diversity has an effect on genotype-specific susceptibility, molecular epidemiology, and vaccine take. Here, we will discuss studies on genetic susceptibility to rotavirus infection and place them in the context of population susceptibility, rotavirus epidemiology, vaccine take, and public health impact.

Rotavirus A in wild and domestic animals from areas with environmental degradation in the Brazilian Amazon

Acute gastroenteritis is one of the main causes of mortality in humans and young animals. Domestic and mainly wild animals such as bats, small rodents and birds are highly diversified animals in relation to their habitats and ecological niches and are widely distributed geographically in environments of forest fragmentation in some areas of the Amazon, being considered important sources for viruses that affect humans and other animals. Due to the anthropical activities, these animals changed their natural habitat and adapted to urbanized environments, thus representing risks to human and animal health. Although the knowledge of the global diversity of enteric viruses is scarce, there are reports demonstrating the detection of rotavirus in domestic animals and animals of productive systems, such as bovines and pigs. The present study investigated the prevalence of Rotavirus A in 648 fecal samples of different animal species from the northeastern mesoregion of the state of Pará, Brazil, which is characterized as an urbanized area with forest fragments. The fecal specimens were collected from October 2014 to April 2016 and subjected to a Qualitative Real-Time Polymerase Chain Reaction (RT-qPCR), using the NSP3 gene as a target. It was observed that 27.5% (178/648) of the samples presented positive results for RVA, with 178 samples distributed in birds (23.6%), canines (21.35%), chiropterans (17.98%), bovines (14.6%), horses (8.43%), small rodents (6.74%), pigs (3.93%) and felines (3.37%), demonstrating the circulation of RVA in domestic animals and suggesting that such proximity could cause transmissions between different species and the occurrence of rearrangements in the genome of RVA as already described in the literature, associated to the traces of environmental degradation in the studied areas.

Detection of a novel equine-like G3 rotavirus associated with acute gastroenteritis in Brazil

Genotype G3P[8] of rotavirus A (RVA) is detected worldwide, usually associated with Wa-like constellation and exhibiting a long RNA migration pattern. More recently, a novel inter-genogroup, G3P[8] reassortant variant with a short electropherotype, has emerged in Asia, Oceania and Europe, denoting an overall potential of unusual rotavirus strains. During a RVA surveillance in Brazil, G3P[8] strains were found displaying a short electropherotype pattern, which had not been detected before in this region. This study aims to characterize the complete genome of 10 G3P[8] strains detected in the northern region of Brazil. All G3P[8] samples were subjected to partial sequencing, and the whole-genome phylogenetic analysis demonstrated that all strains possessed I2-R2-C2-M2-A2-N1-T2-E2-H2 genotype background, representing reassortants with an equine-like G3 VP7 and amino acid changes in VP4 and VP7 antigenic regions as compared to vaccine strains. Phylogenetic analysis demonstrated high nucleotide identity in almost all RNA segments of G3P[8] DS-1 samples detected in Asia, Oceania and Europe as well as G3P[4] strains in Japan. This study reports a novel, equine-like G3P[8] strain circulating in Brazil and isolated from children hospitalized for severe gastroenteritis, and highlights the complex dynamics of RVA molecular epidemiology. Our findings point to a novel RVA strain emerging in this region, and studies should be done to detect whether this may represent a challenge to current vaccine strategies.

Whole genomic analysis of human G12P[6] and G12P[8] rotavirus strains that have emerged in Kenya: identification of porcine-like NSP4 genes

G12 rotaviruses are globally emerging rotavirus strains causing severe childhood diarrhea. However, the whole genomes of only a few G12 strains have been fully sequenced and analyzed, of which only one G12P[4] and one G12P[6] are from Africa. In this study, we sequenced and characterized the complete genomes of three G12 strains (RVA/Human-tc/KEN/KDH633/2010/G12P[6], RVA/Human-tc/KEN/KDH651/2010/G12P[8], and RVA/Human-tc/KEN/KDH684/2010/G12P[6]) identified in three stool specimens from children with acute diarrhea in Kenya, Africa. On whole genomic analysis, all three Kenyan G12 strains were found to have a Wa-like genetic backbone: G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1 (strains KDH633 and KDH684) and G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 (strain KDH651). Phylogenetic analysis showed that most genes of the three strains examined in this study were genetically related to globally circulating human G1, G9, and G12 strains. Of note is that the NSP4 genes of strains KDH633 and KDH684 appeared to be of porcine origin, suggesting the occurrence of reassortment between human and porcine strains. Furthermore, strains KDH633 and KDH684 were very closely related to each other in all the 11 gene segments, indicating derivation of the two strains from a common origin. On the other hand, strain KDH651 consistently formed distinct clusters of 10 of the 11 gene segments (VP1-2, VP4, VP6-7, and NSP1-5), indicating a distinct origin of strain KDH651 from that of strains KDH633 and KDH684. To our knowledge, this is the first report on whole genome-based characterization of G12 strains that have emerged in Kenya. Our observations will provide important insights into the evolutionary dynamics of emerging G12 rotaviruses in Africa.

Sequence and structural analyses of NSP4 proteins from human group A rotavirus strains detected in Tunisia

BACKGROUND

The NSP4 protein of group A rotavirus (RVA) has been recognized as a viral enterotoxin and plays important roles in viral pathogenesis and morphogenesis. Domains involved in structural and functional interactions have been proposed mainly based on the simian SA11 strain.

METHODS

NSP4 has been classified into 15 different genotypes (E1-E15), and the aim of this study was to analyze the sequences of 46 RVA strains in order to determine the aminoacid (aa) differences between E1 and E2 genotypes. Another aspect was to characterize the structural and physicochemical properties of these strains.

RESULTS

Comparison of deduced aa sequences of the NSP4 protein showed that divergences between NSP4 genotypes E1 and E2 were mostly observed in the VP4-binding, the interspecies variable domain (ISVD) and the double-layered particle (DLP) binding domains. Interestingly, uncommon variations in residues 131 and 138, which are known to be important aa in pathogenesis, were found in one unusual animal derived strain belonging to the E2 genotype. Concerning the structural aspect, no significant differences were noted.

CONCLUSION

The presence of punctual aa variations in the NSP4 genotypes may indicate that NSP4 mutates mainly via accumulation of point mutations.

G8P[6] rotaviruses isolated from Amerindian children in Mato Grosso do Sul, Brazil, during 2009: close relationship of the G and P genes with those of bovine and bat strains

During the 2009 national group A rotavirus (RVA) surveillance, five unusual strains of the human G8P[6] genotype were detected in Brazilian indian children with acute gastroenteritis. The aim of this study was to carry out sequence analysis of the two outer capsid proteins (VP4 and VP7) and the inner capsid protein (VP6) of the G8P[6] strains detected in order to provide further information on the genetic relationship between human and animal RVA. A total of 68 stool samples, collected in Mato Grosso do Sul during 2009, were tested for RVA using ELISA, following by reverse transcriptase-PCR and sequencing. RVA infection was detected in 7.3% of samples (5/68). The IAL-RN376 G8 sequence shares a clade with bovine and human strains, displaying highest nucleotide identity to African human strains DRC86 and DRC88, followed by African bovine strain NGRBg8. IAL-RN376 and IAL-RN377 P[6] sequences showed highest identity to human strain R330 from Ireland, and a close genetic relationship to African fruit bat RVA strain KE4852/07. Strains IAL-RN376 and IAL-RN377 display genogroup I VP6 specificity and the I2 genotype, and share high nucleotide identities with human strains B1711, 272-BF and 06-242, and moderate identities with bovine (RUBV81, 86 and KJ9-1) and porcine (HP140) strains. This study suggested that a reassortment between bovine and bat RVA strains could have occurred in animal host(s) preceding the transmission to humans. In the indigenous population, zoonotic transmission is probably fairly frequent as the inhabitants live in close contact with animals under conditions of poor hygiene.

Phylogenetic analysis of probable non-human genes of group A rotaviruses isolated from children with acute gastroenteritis in Belém, Brazil

Rotaviruses (RVs) are the main cause of acute viral gastroenteritis in both humans and young animals of various species such as calves, horses, pigs, dogs, cats, and birds. The genetic diversity of RVs is related to a variety of evolutionary mechanisms, including point mutation, and genome reassortment. The objective of this study was to characterize molecularly genes that encode structural and nonstructural proteins in unusual RV strains. The clinical specimens selected for this study were obtained from children and newborn with RV gastroenteritis, who participated in research projects on viral gastroenteritis conducted at the Evandro Chagas Institute. Structural (VP1-VP4, VP6, and VP7) and nonstructural (NSP1-NSP6) genes were amplified from stool samples by the polymerase chain reaction and subsequently sequenced. Eight unusual RV strains isolated from children and newborn with gastroenteritis were studied. Reassortment between genes of animal origin were observed in 5/8 (62.5%) strains analyzed. These results demonstrate that, although rare, interspecies (animal-human) transmission of RVs occurs in nature, as observed in the present study in strains NB150, HSP034, HSP180, HST327, and RV10109. This study is the first to be conducted in the Amazon region and supports previous data showing a close relationship between genes of human and animal origin, representing a challenge to the large-scale introduction of RV vaccines in national immunization programs.

Phylogenetic analysis of G1P[6] group A rotavirus strains detected in Northeast Brazilian children fully vaccinated with Rotarix™

In 2009 the World Health Organization recommended the use of group A rotavirus (RVA) vaccines in all national immunization programs (NIPs) in order to control severe RVA gastroenteritis disease. In Brazil, Rotarix™ was introduced in the NIP in March 2006, and a significant reduction in mortality rates among children ≤ 5 years old was observed, especially in the Northern and Northeastern Brazil. In the current study the 11 gene segments of six Brazilian G1P[6] RVA strains, isolated in 2009 and 2010 from vaccinated children, were analyzed in order to investigate if the genetic composition of these strains might help to elucidate why they were able to cause acute gastroenteritis in vaccinated children. All six Brazilian RVA strains revealed a complete Wa-like genotype constellation: G1-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1. Phylogenetic analysis showed that all six strains were nearly identical and showed a close genetic relationship with contemporary typical human Wa-like RVA strains. These results suggests that the fact that these strains were able to cause acute gastroenteritis in vaccinated children is likely not due to the genetic background of the strains, but rather to other factors such as host relating factors, co-infecting pathogens or vaccine efficacy. P[6] RVA strains are detected rather occasionally in humans in most regions of the world, except for South Asia and Sub-Saharan Africa. However, recently two studies conducted in Brazil showed the circulation of G12P[6] and G2P[6]. This is the first report on the detection and complete genome analyses of G1P[6] RVA strains in Brazil. Surveillance studies will be crucial to further investigate the prevalence of this genotype in the Brazilian population, and the efficacy of current licensed vaccines, which do not contain the P[6] genotype.

Molecular characterization of the NSP4 gene of human group A rotavirus strains circulating in Tunisia from 2006 to 2008

Non-structural protein 4 (NSP4), encoded by group A rotavirus (RVA) genome segment 10, is a multifunctional protein and the first recognized virus-encoded enterotoxin. Recently, a new classification system for RVAs was proposed and a total of 14 NSP4 genotypes (E1-E14) are currently described. The most common NSP4 genotypes in humans are Wa-like E1 and DS-1-like E2. This report represents the first investigation on the genetic diversity of RVA NSP4 genes in Tunisia from 2006 to 2008. In the present study, the NSP4-encoding genes of human RVA strains with different G/P-genotype combinations were analyzed. NSP4 genes of 261 RVA-positive fecal samples were analyzed using a semi-nested reverse transcriptase-polymerase chain reaction and in addition the NSP4 gene of 46 representative RVA strains were sequenced. Phylogenetic analysis of the Tunisian NSP4 nucleotide sequences revealed the presence of two NSP4 genotypes. Genotype E1 was found to be associated with G1P[8], G3P[6], G3P[8], G4P[6] and G4P[8], whereas genotype E2 was associated with G2P[4], G2P[6] and G6P[9] samples. These results support the hypothesis that P[8] carrying RVA strains usually possess the E1 genotype, whereas P[4] carrying RVA strains usually possess the E2 genotype. P[6] carrying strains were found with both E1 and E2. The unusual G6P[9] strains possessed a E2 genotype with a possible animal origin. These results underline the need for further investigations to assess the validity of NSP4 as a suitable target for epidemiologic surveillance of RVA infections and vaccine development.

Detection and characterization of human rotavirus in hospitalized patients in the cities of Ponta Grossa, Londrina and Assai - PR, Brazil

Acute diarrheal disease is still one of the major public health problems worldwide. Rotaviruses (RV) are the most important viral etiologic agents and children under five years of age are the target population.

OBJECTIVE

To investigate the rate of RV infection in hospitalized patients due to acute diarrhea in the cities of Ponta Grossa, Londrina and Assai - Paraná.

METHODS

Latex agglutination (LA); immunochromatography (ICG); polyacrylamide gel electrophoresis (PAGE) and negative staining electron microscopy (ME) tests were used to detect the virus. For the genotyping, RT-PCR and RT-PCR-ELISA were used, respectively, for NSP4 and VP4/VP7.

RESULT

Out of 124 samples there were 69 positive stool samples for RV, for at least one of the used tests, 67 of them being RV group A (RV-A). Overall, most of the RV positive stool samples came from children under thirteen years of age. However, 12 positive cases occurred in patients aged 13 years or above, including an 81-year old patient.

CONCLUSION

The data showed similar electropherotypes and genotypes G, P and NSP4 of the inland wild circulating strains of RV.

Genetic heterogeneity of wild-type G4P[6] porcine rotavirus strains detected in a diarrhea outbreak in a regularly vaccinated pig herd

Group A rotavirus (RV-A) with short electropherotype was identified by ss-PAGE in a neonatal diarrhea outbreak at a Brazilian pig farm where the sows were regularly vaccinated with a commercial vaccine containing OSU (G5P[7]) and Gottfried (G4P[6]) porcine RV-A (PoRV-A) strains. The ss-PAGE positive stool samples (n=20) were characterized as P[6] genotype by multiplex-nested-RT-PCR assay. The nucleotide analysis of the VP4 gene (VP8*) state that the viruses clustered in P[6] lineages that are also shared by RV-A strains identified in human hosts. Nucleotide analysis of the VP7 gene identified different lineages in G4 including a new lineage tentatively designated IX. The immunological pressure induced by commercial vaccine with a rotavirus containing a G4P[6] genotype of porcine origin (Gottfried strain) might have allowed the selection of PoRV-A strains with characteristics found in RV-A strains isolated of human hosts, such as P[6]-Ie and If, and promoted the selection or emergence of RV-A strains with a new lineage of the G4 genotype. The characterization of PoRV-A strains with unusual genotypes described in this study highlight the importance of surveys on the relationship between human and animal rotavirus strains.

Multiple-gene characterization of rotavirus strains: evidence of genetic linkage among the VP7-, VP4-, VP6-, and NSP4-encoding genes

A total of 162 rotavirus strains detected between 1996 and 2006 among individuals with diarrhea in Rio de Janeiro, Brazil, were analyzed by multiple-gene genotyping. Characterization of strains was done by RT-PCR assay for amplification and typing of the VP7-, VP4-, VP6-, and NSP4-encoding genes. Overall, 139 (85.8%) strains belonged to the common group A rotavirus combinations: 67 (41.4%) belonged to genotype G1-P[8]-I1-E1; 18 (11.1%) were G2-P[4]-I2-E2; 11 (6.8%) were G3-P[8]-I1-E1; 12 (7.4%) were G4-P[8]-I1-E1; and 31 (19.1%) were G9-P[8]-I1-E1. Two samples presented mixed genotypes (G1 + G3-P[8]-I1-E1 and G1 + G9-P[9]-I1-E1) and rare combinations, such as G2-P[6]-I2-E2 and G9-P[6]-I2-E2, were detected in six (3.7%) strains. The results suggest a linkage among all four genes. Genotypes G1/G3/G4/G5/G9-P[8] were correlated strongly to I1-E1 genotypes and G2-P[4]/P[6] were correlated to I2-E2 genotypes. Unusual combinations of genes, such as G3-P[9]-I2-E2, G9-P[9]-I1-E2, and G3-P[9]-I3-E3, were observed in 15 (9.3%) strains. The characterization of multiple genes allows a more complete analysis of the rotavirus isolates and provides evidence of natural reassortment of strains.

Complete genome sequence analysis of candidate human rotavirus vaccine strains RV3 and 116E

Rotaviruses (RVs) cause severe gastroenteritis in infants and young children; yet, several strains have been isolated from newborns showing no signs of clinical illness. Two of these neonatal strains, RV3 (G3P[6]) and 116E (G9P[11]), are currently being developed as live-attenuated vaccines. In this study, we sequenced the eleven-segmented double-stranded RNA genomes of cell culture-adapted RV3 and 116E and compared their genes and protein products to those of other RVs. Using amino acid alignments and structural predictions, we identified residues of RV3 or 116E that may contribute to attenuation or influence vaccine efficacy. We also discovered residues of the VP4 attachment protein that correlate with the capacity of some P[6] strains, including RV3, to infect newborns versus older infants. The results of this study enhance our understanding of the molecular determinants of RV3 and 116E attenuation and are expected to aid in the ongoing development of these vaccine candidates.

Identification of two sublineages of genotype G2 rotavirus among diarrheic children in Parauapebas, Southern Pará State, Brazil

On a world scale, group A human rotaviruses are the most common cause of severe acute gastroenteritis during infancy and childhood, including five (G1, G2, G3, G4, and G9) epidemiologically important genotypes. Among these, G2 denotes a different genogroup which appears to have a cyclic pattern of occurrence and yet little information is available about its genetic variability. The aim of this report was to characterize the emergence of G2 genotype in Paraupebas, Southern Pará State, Brazil, some of which detected after introduction of rotavirus vaccine. A total of 241 fecal specimens from young children with acute gastroenteritis were collected from the "Yutaka Takeda Hospital," a Municipality Hospital, and at the Parauapebas' Health Unit, Pará, from January to September 2006 and during March to November 2008. All samples were tested for rotavirus using immunochromatography, polyacrylamide gel electrophoresis (PAGE), and RT-PCR, yielding an overall positivity of 12.45% (30/241). Rotavirus G2P[4] was identified in 27 of 30 samples (90%), followed by G1P[8] (2/30, 6.67%) and G9P[8] (1/30, 3.33%). Phylogenetic analysis was performed in 15 of the G2 strains, all of which grouped into lineage II. Four of these strains clustered into sublineage II-a (year 2006) and 11 into one possible new sublineage named II-c (year 2008, except SAL-1920-C). The recent re-emergence of G2 genotype associated with lineage II in Brazil warrants the continuous monitoring of circulating rotavirus strains following the nationwide universal use of rotavirus vaccine.

Molecular characterization of a rare, human-porcine reassortant rotavirus strain, G11P[6], from Ecuador

The Pan-American Health Organization established a rotavirus pre-vaccination disease burden and strain surveillance network in Latin America and the Caribbean in 2004. During strain surveillance in Ecuador in 2005-2006, a rare rotavirus genotype, G11P[6], was detected among common strains. Sequencing and phylogenetic analysis of this strain identified a novel lineage of the G11 VP7 gene, most closely related to A253 (91.8% nt identity), a porcine rotavirus strain identified in Venezuela. Most genes of this strain clustered with porcine, human-porcine or bovine-porcine reassortant strains; only VP6 and perhaps NSP2 genes were more closely related to cognate genes of human rotaviruses. Thus, this strain was likely generated by gene reassortment between porcine and human parental strains. Our study provides further evidence that animal rotaviruses play an important role in genetic and antigenic diversity of rotaviruses pathogenic for humans.

Evidence for zoonotic transmission of group C rotaviruses among children in Belém, Brazil

The prevalence and potential zoonotic transmission of group C rotavirus (RVC) were examined by testing fecal samples collected from children during a longitudinal study that was carried out in the outskirts of Belém, Brazil, from December 1982 to March 1986. The study involved a group of 30 children who were followed from birth to 3 years. Of the 77 samples tested from 29 children, 5 (6.5%) were positive for human and 3 (4%) for porcine RVC by using nested PCR assay with primers specific for VP6 gene of human or porcine RVC and by Southern hybridization using a probe specific for VP6 gene of both human and porcine RVC. In addition, a total of 59 fecal specimens from the 30th child were tested, 1 (1.7%) and 14 (23.7%) were positive for human and porcine RVC, respectively. Partial nucleotide sequences of VP6 gene demonstrated that the six human strains detected in Brazil were homologous with other human RVC, and 14 of the 17 porcine RVC strains examined showed a complete homology among themselves but differed slightly from the porcine Cowden strain, suggesting that a single porcine RVC strain was circulating in Belém. This study is the first to provide evidence for transmission of RVC from swine to human. They also indicate that both human and porcine RVC were endemic in Belém.

Molecular epidemiology of astrovirus type 1 in Belém, Brazil, as an agent of infantile gastroenteritis, over a period of 18 years (1982–2000): Identification of two possible new lineages

Human astroviruses (HAstV) are worldwide recognized as important viral enteropathogens during childhood. This study aims to determine the incidence, genetic diversity and intertype variability of HAstV-1 in children less than 5 years of age enrolled in several studies conducted in Belém/Pará, and São Luís/Maranhão, Brazil, from December 1982 to May 2000. Using EIA and RT-PCR, an overall positivity of 6.1% (155/2.534) was achieved, of these, 140 were positive by RT-PCR. The analysis of a 348bp ORF2 fragment revealed that HAstV-1 was the predominant genotype (85/140, 60.7%) throughout the 18 years of study. Phylogenetic analysis was performed for 81 of these strains, and 76 (93.8%) were genetically classified as HAstV-1a. The remainder of strains (n=5) were assigned to possible new lineages, 1e and 1f. Four of these five strains were detected in 1983 and 1984, and the lineage 1a circulated during 10 consecutive years (1990/2000). Genome sequence variation was found among the HAstV-1 strains involving all lineages, but only five nucleotide changes translated into aminoacid changes over this period, suggesting that HAstV-1 was very stable. The data obtained in this study should be useful for further studies at molecular level, including improvement of disease surveillance based on molecular diagnostic tools, and vaccine development.