Natthawan Chaimongkol

Genetic diversity and novel combinations of G4P[19] and G9P[19] porcine rotavirus strains in Thailand

Several epidemiological studies reported the detection of rotavirus strains bearing unusual combinations of genetic background of human and porcine rotaviruses. This observation supports the hypothesis of interspecies transmission of rotaviruses in humans and pigs. The aims of this study were to investigate the genotypes and molecular characteristics of rotaviruses in piglets with diarrhea in several farms from two provinces in Thailand. A total of 207 fecal specimens collected from diarrheic piglets were screened for the presence of groups A, B, and C rotaviruses. Group A rotaviruses were detected in 41 out of 207 (19.8%) fecal specimens tested. A wide variety of G-P combination rotavirus strains were detected in this study. The G4P[6] was identified as the most prevalent genotype (39.0%), followed by G4P[23] (12.2%), G3P[23] (7.3%), G4P[19] (7.3%), G3P[6] (4.9%), G3P[13] (4.9%), G3P[19] (4.9%), G9P[13] (4.9%), G9P[19] (4.9%), G5P[6], and G5P[13] each of 2.4%. Furthermore, G5 and G9 in combinations with P-nontypeable strains were also found at each consisting of 2.4% (n=1) of the collection. It was interesting to note that among diversified porcine rotavirus strains, novel combinations of G4P[19] and G9P[19] strains were detected for the first time in this study. Nucleotide sequences of VP4 and VP7 of these strains were closely related to human rotaviruses reported previously. The data implies that these porcine rotaviruses were probably generated in nature from the reassortment between the viruses of human and porcine origin. This study provides valuable epidemiological information and molecular characteristics of porcine rotaviruses circulating in piglets with diarrhea in northern Thailand.

Circulating of human bocavirus 1, 2, 3, and 4 in pediatric patients with acute gastroenteritis in Thailand

Human bocavirus (HBoV) is a newly identified human parvovirus that associated with respiratory and gastrointestinal diseases. Epidemiological surveillance of HBoV was conducted on fecal specimens collected from hospitalized children with diarrhea in Chiang Mai, Thailand in 2011. Among a total of 222 fecal specimens tested, 17 (7.7%) were positive for HBoV by PCR. Of the 17 HBoV positive samples, double- or triple-infections together with other enteric viruses were found in 10 (58.8%) pediatric patients, while monoinfection with HBoV alone was detected in seven (41.2%) cases. Mixed infection among HBoV with norovirus GII was frequently observed in this population. The partial VP1 nucleotide sequences of all 17 HBoV strains demonstrated that all four species of HBoV were found in the specimens tested. Eleven strains were HBoV1. Other three strains showed the sequence identity with HBoV2, which were most closely related to the HBoV2A. In addition, other two HBoV strains showed the highest level of nucleotide sequence identity with the HBoV3. It was surprisingly to observe that one Thai HBoV strain showed a unique characteristic similar to the HBoV4, a rare species of HBoV found in acute gastroenteritis patients. In summary, this study presents the genetic background information of HBoV circulated in acute gastroenteritis children in Chiang Mai, Thailand and it was clearly demonstrated that HBoVs circulated in this area were genetically diverse as all four species of HBoVs (HBoV1-4) were detected in the fecal specimens collected from pediatric patients admitted to the hospitals in this area.

Detection and molecular characterization of cosavirus in adults with diarrhea, Thailand

Human cosavirus (HCoSV) is a newly discovered virus in Picornaviridae family. At present it is not clear whether HCoSV is associated with diseases, including gastroenteritis in humans, as epidemiological data is limited. Epidemiological surveillance of HCoSV was conducted on 150 fecal specimens collected from children and 150 samples from adults with diarrhea in Thailand by RT-PCR screening. HCoSV was found in a single adult specimen and not in any of the fecal specimens from children. This represents the first report of HCoSV infection in patients with diarrhea in Thailand. Extensive epidemiological surveillance of novel viruses associated with diarrhea in other populations may provide a better understanding of the distribution, genetic diversity, and association of the viral agents associated with acute gastroenteritis in humans.

Diversity of human astrovirus genotypes circulating in children with acute gastroenteritis in Thailand during 2000-2011.

Human astrovirus (HAstV) is one of the causative agents of acute gastroenteritis in children worldwide. The objective of this study was to elucidate the molecular epidemiology and genotypic diversity of HAstV circulating in pediatric patients admitted to hospital with diarrhea in Thailand during the year 2000–2011, except for 2004, 2006, and 2009. A total of 1,022 fecal specimens were tested for HAstV by reverse transcription polymerase chain reaction (RT‐PCR). HAstV was detected at 1.4% (14 of 1,022). All HAstV strains detected in this study were characterized further by nucleotide sequencing and phylogenetic analysis. Analysis of 348 bp partial capsid nucleotide sequences revealed that HAstV strains detected were HAstV‐1 (1a, 1b, and 1d) (8 strains), HAstV‐2 (2c) (3 strains), HAstV‐3 (1 strain), and HAstV‐5 (2 strains). HAstV‐1, the most predominant genotype was detected initially in 2002 and circulated continuously up to 2011. HAstV‐2 was detected in year 2001, and 2007 and grouped into a 2c lineage. HAstV‐3 was found only in 2000 and HAstV‐5 was found in the year 2001. The findings indicate that a wide variety of HAstV strains continue to circulate in children admitted to hospital with acute gastroenteritis in Thailand over a decade. The data provide an epidemiological overview of HAstV infection and HAstV genotype distribution in Thailand. J. Med. Virol. 84:1751–1756, 2012.

Genotypic linkages of gene segments of rotaviruses circulating in pediatric patients with acute gastroenteritis in Thailand

Rotavirus is a major cause of morbidity and mortality of infants and young children with diarrhea throughout the world. In Thailand, extensive studies of rotavirus infections have been reported continually and rotavirus diarrhea remains a common illness. To monitor the epidemiological situation of rotavirus in Chiang Mai, Thailand, surveillance of rotavirus circulating in pediatric patients was conducted. A total of 160 fecal specimens collected from children hospitalized with diarrhea were tested for rotaviruses groups A, B, and C by RT-PCR and their genotypes were identified by multiplex PCR and nucleotide sequencing. Group A rotavirus was detected at 29.4% but none of group B and C was found in this study. Molecular characterizations of G- and P-genotypes revealed three different G-P combinations, G1P[8] was the most predominant genotype with the prevalence of 72.3% followed by G2P[4] at 19.2%, and G3P[8] at 8.5%. Phylogenetic analyses of VP7 and VP4 genes of the representative strains detected in the present study, G1, G2, G3, and P[4] and P[8], respectively, revealed that G1 belonged to G1-Ic and G1-II, G2 belonged to G2-II, and G3 belonged to G3-III-S4 lineages while P[4] and P[8] were identified as P[4]-V and P[8]-III lineages. Analyses of VP6, NSP4, and NSP5 genes demonstrated that these representative strains belonged to genotypes I1 and I2, E1 and E2, and H1 and H2, respectively. Analyzing the association of G- and P-genotypes with I, E, H genotypes revealed unique patterns of genotypic linkage. The G1P[8] and G3P[8] were intimately linked with I1, E1, H1 genotypes and displayed the genetic features of G1-P[8]-I1-E1-H1 and G3-P[8]-I1-E1-H1, respectively, while G2P[4] was closely linked to I2, E2, H2 genotypes and showed the genetic pattern of G2-P[4]-I2-E2-H2. This study provides epidemiological information and insight into the genetic background of rotaviruses circulating in pediatric patients in Chiang Mai, Thailand.

Evaluation of an immunochromatography method for rapid detection of noroviruses in clinical specimens in Thailand.

Norovirus (NoV) is a causative agent of gastroenteritis in children and adults worldwide. Although reverse transcription‐polymerase chain reaction (RT‐PCR) has been accepted as the standard method for diagnosis of NoV infection, it requires well‐trained personnel and sophisticated equipments. Performance of a commercial immunochromatography (IC) test for rapid detection of NoV was evaluated with fecal specimens collected from children admitted to a hospital with acute gastroenteritis during 2005–2007 in Chiang Mai, Thailand. A total of 463 fecal specimens were tested for the presence of NoV by a commercial immunochromatography kit (IP‐NoV) and by RT‐PCR. Sensitivity, specificity, and agreement of immunochromatography as compared to RT‐PCR were 74.2%, 99.5%, and 96.1%, respectively. Based on the NoV genotypes determined by phylogenetic analysis, immunochromatography detected NoV GII/3, GII/4, GII/6, GII/13, GII/15, and GII/16 genotypes. The findings indicate that the immunochromatography kit could be used for a direct detection of NoV GII in clinical specimens and covering a wide range of NoV genotypes circulating in Thailand. J. Med. Virol. 82:2106–2109, 2010.

Molecular characterization of norovirus variants and genetic diversity of noroviruses and sapoviruses in Thailand

Norovirus (NoV) and Sapovirus (SaV) have been reported as a common cause of acute gastroenteritis worldwide. For a decade, surveillances of NoV and SaV have been conducted continually in Thailand. To monitor the epidemiological situation and to determine the genetic variation of NoV and SaV in Chiang Mai, Thailand, 567 samples collected from pediatric patients hospitalized with acute gastroenteritis were examined during 2007, and 2010–2011 by semi‐nested RT‐PCR and nucleotide sequencing methods. NoV was detected at 15.9%. Phylogenetic analysis revealed multiple NoV genotypes, GI/14 (1.1%), GII/1 (1.1%), GII/2 (1.1%), GII/3 (4.4%), GII/4 (65.6%), GII/6 (10.0%), GII/7 (2.2%), GII/12 (4.4%), GII/13 (3.3%), GII/16 (5.7%), and unclassified genotype (1.1%), circulating in this area. Among these, NoV GII/4 was the most prevalent genotype with a predominance of GII/4 2009 over other variants, 1996, 2006a, and 2006b. For SaV, the prevalence was 1.2% which was much lower than those of NoV and only SaV GI/1 was detected. This study highlights the epidemiology of NoV and SaV and genetic diversity of viruses circulating in pediatric patients hospitalized with acute gastroenteritis in Chiang Mai, Thailand. J. Med. Virol. 86:1210–1218, 2014.

A novel multiplex RT-PCR for identification of VP6 subgroups of human and porcine rotaviruses

VP6 protein antigens allow classification of rotaviruses into at least four subgroups, depending on the presence or absence of SG-specific epitopes: SG I, SG II, SG (I+II), and SG non-(I+II). However, MAbs against epitopes on the VP6 protein of human and porcine rotaviruses, sometimes, do not recognize SG-specific epitopes or recognize irrelevant-SG epitopes and therefore result in the incorrect assignment of subgroups. In order to solve this problem, a novel multiplex RT-PCR was developed as an alternative tool to identify VP6 genogroups using newly designed primers which are specific for genogroup I or II. The sensitivity and specificity of the newly developed multiplex RT-PCR method was evaluated by testing with human and porcine rotaviruses of known SG I, SG II, SG (I+II), and SG non-(I+II) strains in comparison with monoplex RT-PCR and VP6 sequence analysis. The results show that the genogroups of both human and porcine rotaviruses as determined by the new multiplex RT-PCR method were in 100% agreement with those determined by monoplex RT-PCR and VP6 sequence analysis. The method was shown to be specific, sensitive, less-time consuming, and successful in genogrouping clinical isolates of rotaviruses circulating in children and piglets with acute diarrhea.

Evolutionary consequences of G9 rotaviruses circulating in Thailand

Infection with group A rotaviruses is the main cause of acute gastroenteritis in infants and young children worldwide. Rotavirus G9 is recognized as the fifth most predominant G genotype that spreads throughout the world. In this study, we describe the changing distribution of rotavirus G9 genotype in Chiang Mai, Thailand, from 1989 to 2005. Molecular genetic evolutionary analysis of the G9 rotavirus VP7 gene was performed. The G9 rotavirus in Thailand was first detected in Chiang Mai in 1989 with a low prevalence of 1.98%, but in 2000 and 2001 it had become the most predominant genotype, reaching prevalence of 75% and 92.2%, respectively. Then, the prevalence of G9 reached a peak of 100% in 2002 and decreased abruptly over the next 3 years, i.e. 16.7% in 2003, 32.1% in 2004, and 4.7% in 2005. Our phylogenetic analysis demonstrates that all the G9 rotaviruses circulating in Thailand belonged to lineage III, and clustered closely together based on the year of virus isolation. One amino acid change from Thr to Ile was observed in antigenic region C at position 208 between the G9 strains isolated in 1989 and the strains of 1997-2005. These findings provide the overall picture and genomic data of G9 rotaviruses circulating in Chiang Mai, Thailand.