Distribution of human leukocyte antigens-E alleles in Thailand.

The aim of this study was to investigate the distribution of human leukocyte antigens (HLA) -E alleles in Thailand. HLA-E alleles were assigned by using a polymerase chain reaction-sequence specific oligonucleotide probes (PCR-SSOP) method and direct sequencing in 200 healthy individuals. They comprised 100 Thai, 50 Chinese and 50 Thai-Chinese. From the results, three alleles of HLA-E could be detected in these populations. The E*0101 was the most common allele in Thai and Thai-Chinese with allelic frequencies of 42.5 per cent and 38 per cent, respectively. The other HLA-E allele frequencies of Thai origin were 33 per cent for E*01031 and 24.5 per cent for E*01032, respectively. Among Thai-Chinese, the allele frequencies of HLA-E were 31 per cent for E*01031 and E*01032, respectively. Whereas, the E*01031 was the predominant allele in Chinese origin with a frequency of 39 per cent, followed by E*0101 and E*01032 with 32 per cent and 29 per cent, respectively. No E*01033, E*0102 and E*0104 could be detected in all individuals. When comparing the distribution of HLA-E alleles between each of the populations (Thai vs Chinese, Thai vs Thai-Chinese and Chinese vs Thai-Chinese), no significant difference could be found among these populations. In addition, there was no significant difference of the distribution of HLA-E alleles between the study populations and other populations from Asian countries, reported previously. However, there were significant differences between the populations (Thai, Chinese and Thai-Chinese) and Danish (chi2 = 15.64, p = 0.0004; chi2 = 24.58, p = 0.0000046; chi2 = 14.69, p = 0.00065, respectively).

Serological analysis of human leukocyte antigens-A and -B antigens in Thai patients with nasopharyngeal carcinoma.

OBJECTIVE: To study the distribution of human leukocyte antigens (HLA) -A and -B antigens by standard microlymphocytotoxicity assay in Thai nasopharyngeal carcinoma (NPC) patients compared to normal controls in order to identify the alleles associated with NPC in Thailand. DESIGN: Retrospective-Analytical study. SUBJECTS: Fifty-three unrelated Thai patients with histologically confirmed NPC diagnosed at King Chulalongkorn Memorial Hospital and 70 healthy unrelated Thai individuals served as controls. METHOD: Lymphocyte separation and HLA typing were performed from freshly drawn blood by standard microlymphocytotoxicity assay. The significance of differences between the two groups was analyzed by the chi-square test. RESULTS: HLA-A2 was observed at a greater frequency in patients being found in 31/53 (58%) NPC patients compared to 27/70 (38%) controls (p = 0.02). An increase in HLA-B46 was also demonstrated. HLA-B46 was present in 16/53 (30%) NPC patients but was observed in 10/70 (14%) in controls (p = 0.03). CONCLUSIONS: This study reported two susceptible, HLA-A2 and HLA-B46 antigens, for NPC in a Thai population.

DRB1*04 subtype in Thai patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) in a Thai population is significantly associated with HLA-DR4. The frequency of DR4 was 43 per cent in RA patients and 20 per cent in the healthy controls (p = 0.00008, OR = 3.06, 95% CI = 1.71, 5.52). To analyze which DR4 alleles were associated with the disease, the authors subtyped 52 DR4-positive RA patients compared to 28 DR4-positive healthy controls by amplification with DR4-specific primers followed by direct sequencing. Six DR4 alleles (DRB1*0401, *0403, *0404, *0405, *0406, and *0410) were found in the RA patient group while 5 alleles (DRB1*0401, *0403, *0405, *0406, and *0407) were found in the control group. Both groups were predominated by DRB11*0405, but there was a significant increase in the frequency of DRB1*0405 in DR4+ RA patients compared to DR4+ healthy controls (84.6% vs 46.4%, p = 0.0008, OR = 6.35, 95% CI = 1.96, 21.08). DR4 which shared epitope alleles (DRB1*0401, *0404, *0405) were observed in 47 (90.3%) DR4+ patients and 15 (53.5%) DR4+ controls (p = 0.0005, OR = 8.15, 95% CI = 2.29, 33.2). In addition, the authors found that DRB1*0403 was significantly decreased in DR4+ RA patients compared to controls (p = 0.0065, OR = 0.07, 95% CI = 0, 0.67).

Emm types of invasive group A streptococcal isolates from Thai patients at King Chulalongkorn Memorial Hospital from 1995-1999.

Emm (M protein gene) typing was used to analyze group A streptococcal (GAS) clinical isolates in Thailand from in-patients at Chulalongkorn University Hospital (CUH) between January 1, 1995 and December 31, 1999. Forty GAS isolates were recovered from blood and other sterile sites from 40 patients presenting with different types of infections. A variety of emm sequences (24 types) have been reported in this study including the identification of 2 novel emm variants demonstrating the diverse population of invasive GAS isolates in Thailand. The common emm types include emm1 (5 isolates, 12.5%), emm22 (4 isolates, 10%), emm25 (3 isolates, 7.5%), emm61 (3 isolates, 7.5%), and STNS1033 (3 isolates, 7.5%). No particular emm types of GAS tend to be frequently associated with specific clinical presentation, complication, or anatomic site of infection. This report provides epidemiological information from Thailand where streptococcal infections and their sequelae are important public health problems. In addition, the results are useful for the development of a suitable M protein based vaccine in the future.

Outbreak of uncommon type of group A streptococcal pharyngitis among cadets at the Chulachomklao Royal Military Academy, Nakhon Nayok, Thailand.

A large outbreak of group A Streptococcus (GAS) pharyngitis occurred among 285 cadets at the Chulachomklao Royal Military Academy, Nakhon Nayok between September 22 and 27, 1996. An epidemiologic investigation was conducted to determine the source of infection. It seemed that respiratory droplets were the mechanism of spread, although foodborne transmission could not be excluded. To assess the presence of the outbreak strain in the community, conventional serotyping and molecular typing by emm sequencing were performed. The results demonstrated the advantage of molecular typing compared to serotyping and suggested that the outbreak was caused by the same strain. Interestingly, the involvement of the causative emm79 strain, which is an uncommon type of GAS disease, in a large number of patients may imply the invasive potential of this organism.

Distribution of HLA-B alleles in nasopharyngeal carcinoma patients and normal controls in Thailand.

HLA-B frequencies in 54 unrelated nasopharyngeal carcinoma (NPC) patients and 49 healthy random controls in Thailand were investigated by direct DNA sequencing. Similar to previous reports in Chinese NPC patients, HLA-B*4601 was observed at a greater frequency in patients (21/54 (40%)) compared to controls (7/49 (14%). An increase in HLA-B*51012 was also demonstrated. B*51012 was present in 6/54 (11%) NPC patients but was not observed (0%) in controls. B*44032 was associated with a decreased risk. Five out of 54 (9%) NPC patients had B*44032 compared to 14/49 (29%) in the control group.

Ex vivo analysis of T-cell responses to Epstein-Barr virus-encoded oncogene latent membrane protein 1 reveals highly conserved epitope sequences in virus isolates from diverse geographic regions.

Epstein-Barr virus (EBV)-encoded oncogene latent membrane protein (LMP) 1, which is consistently expressed in multiple EBV-associated malignancies, has been proposed as a potential target antigen for any future vaccine designed to control these malignancies. However, the high degree of genetic variation in the LMP1 sequence has been considered a major impediment for its use as a potential immunotherapeutic target for the treatment of EBV-associated malignancies. In the present study, we have employed a highly efficient strategy, based on ex vivo functional assays, to conduct an extensive sequence-wide analysis of LMP1-specific T-cell responses in a large panel of healthy virus carriers of diverse ethnic origin and nasopharyngeal carcinoma patients. By comparing the frequencies of T cells specific for overlapping peptides spanning LMP1, we mapped a number of novel HLA class I- and class II-restricted LMP1 T-cell epitopes, including an epitope with dual HLA class I restriction. More importantly, extensive sequence analysis of LMP1 revealed that the majority of the T-cell epitopes were highly conserved in EBV isolates from Caucasian, Papua New Guinean, African, and Southeast Asian populations, while unique geographically constrained genetic variation was observed within one HLA A2 supertype-restricted epitope. These findings indicate that conserved LMP1 epitopes should be considered in designing epitope-based immunotherapeutic strategies against EBV-associated malignancies in different ethnic populations.