Thanunrat Thongmee

Assessing Antigenic Drift of Seasonal Influenza A(H3N2) and A(H1N1)pdm09 Viruses

Under selective pressure from the host immune system, antigenic epitopes of influenza virus hemagglutinin (HA) have continually evolved to escape antibody recognition, termed antigenic drift. We analyzed the genomes of influenza A(H3N2) and A(H1N1)pdm09 virus strains circulating in Thailand between 2010 and 2014 and assessed how well the yearly vaccine strains recommended for the southern hemisphere matched them. We amplified and sequenced the HA gene of 120 A(H3N2) and 81 A(H1N1)pdm09 influenza virus samples obtained from respiratory specimens and calculated the perfect-match vaccine efficacy using the p epitope model, which quantitated the antigenic drift in the dominant epitope of HA. Phylogenetic analysis of the A(H3N2) HA1 genes classified most strains into genetic clades 1, 3A, 3B, and 3C. The A(H3N2) strains from the 2013 and 2014 seasons showed very low to moderate vaccine efficacy and demonstrated antigenic drift from epitopes C and A to epitope B. Meanwhile, most A(H1N1)pdm09 strains from the 2012–2014 seasons belonged to genetic clades 6A, 6B, and 6C and displayed the dominant epitope mutations at epitopes B and E. Finally, the vaccine efficacy for A(H1N1)pdm09 (79.6–93.4%) was generally higher than that of A(H3N2). These findings further confirmed the accelerating antigenic drift of the circulating influenza A(H3N2) in recent years.

Complete genotype constellation of human rotavirus group A circulating in Thailand, 2008-2011.

This study has identified diverse and re-assorted group A rotavirus (RVA) strains by sequence and phylogenetic analysis of the 11 genomic segments. The 22 cases investigated in this study were collected from children with diarrhea between 2008 and 2011. The RVA genomic constellations identified in this study were identified as G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 22.7% (5/22); G2-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2 27.3% (6/22); G3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 18.2% (4/22); G3-P[9]-I3-R3-C3-M3-A3-N3-T3-E3-H6 4.6% (1/22); G9-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 9.1% (2/22); G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1 4.6% (1/22) and G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 13.6% (3/22). Two RVA strains, possessing a complete AU-1-like genomic backbone, showed re-assortment for genes 3 and 11, revealing possible zoonotic re-assortment events between human and canine strains. In addition, one of the analyzed strains revealed a G12 specificity for VP7 in combination with a porcine-like P[6] VP4 and a complete Wa-like constellation. Continuous surveillance of rotavirus strains and their evolution may be useful for understanding the emergence of novel strains through interspecies genome re-assortment between human and animal viruses.

Hepatitis E virus genotype 3f sequences from pigs in Thailand, 2011-2012.

Phylogenetic analysis of partial ORF1 and ORF2 genes of Hepatitis E virus (HEV) strains from pigs in Thailand during 2011–2012 was performed. The result indicated that the current Thai strains belonged to the genotype 3 subgroup 3f, which were similar to the previous HEVs circulating in humans in Thailand.

Seroprevalence of antibodies to dengue and chikungunya viruses in Thailand

The abundance of Aedes mosquito species enabled widespread transmission of mosquito-borne chikungunya virus (CHIKV) and dengue virus (DENV) in Southeast Asia. Periodic seroprevalence surveys are therefore necessary to assess the viral burden in the population and the effectiveness of public health interventions. Since the current seroprevalence for CHIKV and DENV in Thailand are unknown, we evaluated evidence of past infection among Thais. Eight-hundred and thirty-five serum samples obtained from individuals living in central and southern Thailand were assessed for anti-CHIKV and anti-DENV IgG antibodies using commercial enzyme-linked immunosorbent assays. Overall, 26.8% (224/835) of individuals were seropositive for CHIKV, the majority of whom were also DENV-seropositive (91.1%, 204/224). Approximately half of all adults in their fifth decade of life had attained CHIKV seropositivity. Children under 15 years of age in southern Thailand were significantly more likely to be CHIKV-seropositive compared to those residing in central Thailand. In contrast, 79.2% (661/835) of Thais were DENV-seropositive, 30.9% (204/661) of whom also had antibodies to CHIKV. CHIKV/DENV dual seropositivity among Thais was 24.4% (204/835). The age-standardized seroprevalence for DENV was three times that of CHIKV (80.5% vs. 27.2%). Relatively high CHIKV seroprevalence among adults living in central Thailand revealed an under-recognized CHIKV burden in the region, while the low-to-moderate transmission intensity of DENV (seroprevalence <50% at 9 years) is expected to reduce the impact of DENV vaccination in Thailand. This most recent seroprevalence data provide serological baselines for two of the most common mosquito-borne viruses in this region.

Seroprevalence of Antibodies to Pertussis Toxin among Different Age Groups in Thailand after 37 Years of Universal Whole-Cell Pertussis Vaccination

Despite the high coverage of prophylactic vaccine against Bordetella pertussis infection in many countries for more than three decades, pertussis remains a common vaccine-preventable disease. Infections have been detected more commonly in countries using acellular pertussis vaccine in their Expanded Program of Immunization. Thailand implemented a routine infant immunization program with whole-cell pertussis vaccine in 1977, and since 1992, the national vaccine policy has offered a five-dose whole-cell pertussis vaccine for children given at the ages of 2, 4, 6, 18, and 48 months. This study aimed to investigate the seroprevalence of antibodies to pertussis toxin among healthy people across all ages to determine the level of whole-cell vaccine-induced immunity in the population, and to identify which age group should be targeted for a booster dose. The lowest seronegative rate and highest geometric mean concentrations were found in the 0–10 years age group, corresponding to their recent pertussis vaccination. The proportion of people with undetectable IgG level was prominent, starting after 11 years of age onwards. Now that a reduced-dose pertussis vaccine with fewer adverse effects is available, a booster dose during adolescence should be considered in order to reduce the incidence of pertussis disease. Further studies exploring how long the reduced-dose pertussis vaccine can provide protective immunity against pertussis disease when administered to adults and adolescents should also be performed.

Swine is a possible source of hepatitis E virus infection by comparative study of hepatitis A and E seroprevalence in Thailand.

Hepatitis A virus (HAV) and hepatitis E virus (HEV) infection in developing countries are associated with contaminated food or water. Although Thailand is non-endemic for HEV, sporadic infections may occur from zoonotic transmission. Individuals between 7 months to 69 years (mean age = 32.8) from predominantly Islamic Narathiwat (n = 305) and swine farm-dense Lop Buri (n = 416) provinces were screened for anti-HEV and anti-HAV antibodies by commercial enzyme-linked immunosorbent assay and automated chemiluminescent microparticle immunoassay, respectively. Seroprevalence and relative antibody titers were analyzed according to age groups. HAV IgG antibody positive rates in Lop Buri and Narathiwat residents were 39.9% and 58%, respectively (p < 0.001). Greater than 90% of individuals >50 years old in both provinces possessed anti-HAV IgG. In contrast, seroprevalence for anti-HEV IgG was much higher in Lop Buri (37.3%) than in Narathiwat (8.9%) (p < 0.001). Highest anti-HEV IgG prevalence was found among 21-30 year-olds (50%) in Lop Buri and 41-50 year-olds (14.1%) in Narathiwat. In summary, fewer individuals possessed anti-HEV IgG in Narathiwat where most residents abstained from pork and fewer swine farms are present. Therefore, an increased anti-HEV IgG seroprevalence was associated with the density of swine farm and possibly pork consumption. Adults were more likely than children to have antibodies to both HEV and HAV.

Complete genome analysis of a rare human G3P[9] rotavirus posing as an AU-1 like strain

BackgroundWe performed phylogenetic and sequence analysis by Basic Local Alignment Search Tool (BLAST) of a complete Human Rotavirus (HRV) genome isolated from a hospitalized child with acute gastroenteritis in Thailand.FindingsThe results indicated an uncommon strain characterized by multiple re-assortments in the VP3, VP4, VP6, NSP1, NSP4 and NSP5 genes. The uncommon strain is genotype G3-P[9]-I3-R3-C3-M3-A3-N3-T3-E3-H6, which displays aspects of the AU-1, FRV-1 and corresponds to the feline/canine prototype G3P[9] strain.ConclusionsThe results suggested that nearly all the eleven gene segments of G3P[9] RVA strain CU365 might have originated from feline/canine RVAs (Rotavirus A).

The important role of early diagnosis and preventive management during a large-scale outbreak of hepatitis A in Thailand

Abstract Introduction: Acute hepatitis A is a worldwide public health problem especially in developing countries. Recently, a large, community-wide outbreak of hepatitis A occurred in the northeast part of Thailand. Methods: Demographic and clinical data as well as blood samples were collected and analyzed from patients with acute hepatitis who attended the Buengkan Provincial Hospital from June to September 2012. About 1619 patients with clinical symptoms of hepatitis A visited the hospital during the outbreak which manifested in three waves. Blood samples were collected from 205 patients. Results: One hundred and seventy eight patients had hepatitis A confirmed by the presence of anti-hepatitis A virus (HAV) IgM and/or HAV-RNA. The sensitivities for anti-HAV IgM and HAV-RNA were 95·5% (170/178) and 61·8% (110/178), respectively. When HAV-RNA was combined with anti-HAV IgM test, this increased the diagnostic yield by 7·2% (8/111) in the early phase of the acute infection (less than 5 days). Investigation of the molecular structure of the detected viruses indicated that all of the infections were caused by HAV genotype IA. There were no fatalities from this outbreak. Rapid detection, health education, sanitation campaigns, and vaccination offered on a voluntary basis have steadily reduced the number of infected patients and stopped the outbreak. Conclusion: Occasionally a large-scale outbreak of HAV genotype IA can occur. A combination of HAV-RNA and anti-HAV IgM tests can increase the diagnostic yield during the early phase of the acute infection. Early diagnosis and preventive management campaigns can slow down and stop the outbreak.

Seroprevalence of Anti-EBV IgG among Various Age Groups from Khon Kaen Province, Thailand

Epstein-Barr virus (EBV) is an extremely common herpesvirus that may cause asymptomatic infection or various diseases, including infectious mononucleosis, certain lymphoproliferative diseases and several types of neoplasms. Vaccine development is an important strategy to reduce the burden of EBV-associated diseases and the timing of vaccinations should be before primary infection occurs. In the past, more than 90% of Thai children were infected with EBV in early childhood. Now, due to the improved healthcare system in Thailand, we aim to determine current prevalence of EBV infection among people in different age groups. A total of 538 sera were collected from residents of Khon Kaen province in northeastern Thailand for detecting anti-EBV IgG. Sera of infants under 2-years-old were also tested for anti-EBV IgM and EBV-DNA. The prevalence of anti-EBV IgG was 47.1% (95% CI: 23.3-70.8) in infants aged 0-6 months, 34.9% (95% CI: 23.1-46.7) in those aged 6-24 months, 87.9% (95% CI: 79.5-96.3) in children aged 3-5 years and then maintained at above 95% through adulthood. These seropositivity rates among Thai children remain similar to those found in a previous study conducted 20 years ago. Thai children are still exposed to EBV from an early age. Therefore, a prophylactic vaccine should be given within the first two years of life.

Evolution of the neuraminidase gene of seasonal influenza A and B viruses in Thailand between 2010 and 2015.

The neuraminidase inhibitors (NAIs) oseltamivir and zanamivir are commonly used for the treatment and control of influenza A and B virus infection. However, the emergence of new influenza virus strains with reduced susceptibility to NAIs may appear with the use of these antivirals or even naturally. We therefore screened the neuraminidase (NA) sequences of seasonal influenza virus A(H1N1), A(H1N1)pdm09, A(H3N2), and influenza B virus strains identified in Thailand for the presence of substitutions previously reported to reduce susceptibility to NAIs. We initially examined oseltamivir resistance (characterized by the H275Y mutation in the NA gene) in 485 A(H1N1)pdm09 strains circulating in Thailand and found that 0.82% (4/485) had this substitution. To further evaluate the evolution of the NA gene, we also randomly selected 98 A(H1N1)pdm09, 158 A(H3N2), and 69 influenza B virus strains for NA gene amplification and sequencing, which revealed various amino acid mutations in the active site of the NA protein previously shown to be associated with reduced susceptibility to NAIs. Phylogenetic analysis of the influenza virus strains from this study and elsewhere around the world, together with the estimations of nucleotide substitution rates and selection pressure, and the predictions of B-cell epitopes and N-linked glycosylation sites all provided evidence for the ongoing evolution of NA. The overall rates of NA evolution for influenza A viruses were higher than for influenza B virus at the nucleotide level, although influenza B virus possessed more genealogical diversity than that of influenza A viruses. The continual surveillance of the antigenic changes associated with the NA protein will not only contribute to the influenza virus database but may also provide a better understanding of selection pressure exerted by antiviral use.