Cytotoxic T lymphocyte responses to vaccinia virus antigens but not HIV-1 subtype E envelope protein seen in HIV-1 seronegative Thais.

The HIV-1 prime boost phase I/II vaccine trial using a recombinant canarypox vector, vCP1521, containing subtype E env (gp120), and subtype B env (gp41), gag and protease has started in Thailand. We have demonstrated that although 4 from 15 human immunodeficiency virus type 1 (HIV-1) seronegative Individuals showed cytotoxic T lymphocyte (CTL) responses to vaccinia virus antigens, none of them showed specific CTL responses to subtype E Env after in vitro stimulation. This preliminary study suggests that specific CTL responses to subtype E envelope detected in HIV-1 seronegative Individuals after vaccination should be considered as specific responses to the immunization.

Specific IgA antibody to Epstein-Barr viral capsid antigen: a better marker for screening nasopharyngeal carcinoma than EBV-DNA detection by polymerase chain reaction.

Nasopharyngeal carcinoma (NPC) is strongly associated with Epstein-Barr virus (EBV) infection. To assess whether EBV DNA detection by polymerase chain reaction (PCR) or presence of specific serum antibody to viral capsid antigen (VCA) was a better marker for screening NPC, nasopharyngeal tissues and blood samples from 58 NPC patients and 24 non-NPC patients (23 with laryngotracheal stenosis and 1 with chronic tonsillitis) were tested for the presence of EBV DNA and serum specific VCA antibodies, respectively. EBV DNA was detected in 56 (96.5%) of NPC patients and 15 (62.5%) of non-NPC controls, with predominantly EBV type A in both groups. On the other hand, specific VCA IgA antibody was detected in the majority of NPC patients: 52 (89.7%) while only 4 (16.7%) were detected in non-NPC controls. Therefore, specific VCA IgA antibody may serve as a better marker for screening NPC than EBV DNA detected by PCR.

Maternal and viral factors in vertical transmission of HIV-1 subtype E.

Vertical transmission of HIV-1 is caused by multifactorial factors. To access the relationship of viral factors involving in perinatal transmission of HIV-1 subtype E, which is the predominant type in Thailand, plasma viral load, blood CD4+ lymphocyte level, heteroduplex mobility, and V3 sequence of the HIV-1 envelope gene were studied in 32 transmitting and 25 non-transmitting mothers. We found that HIV-1 subtype E vertical transmission was strongly associated with high maternal plasma viral RNA (> 4 x 10(4) copies/ml) and high genetic diversity of envelope gene determined by heteroduplex mobility (< 0.9). The variation of nucleotide sequences in envelope gene of subtype E vertical transmission could not determine in V3 region. Hence, plasma viral load and heteroduplex mobility can be used as prediction factors in vertical transmission of HIV-1 subtype E.

The latency rate of human herpesvirus 6 (HHV6) in positive and negative human immunodeficiency virus (HIV) infection of intravenous drug users (IVDU).

The seropositive and latency rates of HHV6 among IVDU with positive and negative HIV and control group were demonstrated. By immunofluorescent antibody test, no differences in the seropositive rates were found among these three groups. All groups had seropositive rate at the average 89% and GMT antibody 1:26. This meant that most of them had previous infection with HHV6. In addition, HHV6-DNA was determined and classified into subgroups: HHV6A and HHV6B, by polymerase chain reaction. The prevalence of HHV6-DNA indicated HHV6 latency in vivo. High latency rate of HHV6 was found in all three groups (the average 54%). Moreover, HHV6B (49%) had a higher frequency than HHV6A (5%); HHV6a was found only in IVDU with or without HIV infection. The result suggested that the HHV6 latency in IVDU with positive HIV may possibly transactivate HIV. The pathogenesis of HHV6 in AIDS patients should be further investigated. However, this research finding is useful for treatment, health care, prevention and control of AIDS in case of dual infections and latency of herpesvirus infection in AIDS.

Seroprevalence of human herpesvirus 6 and 7 infections in the Thai population.

Seroprevalence of human herpesvirus 6 (HHV-6) and 7 (HHV-7) was estimated in the Thai population using indirect immunofluorescence assay to determine serum antibodies to HHV-6 and HHV-7. A total of 333 serum samples obtained from umbilical cord blood and venous blood of healthy persons at Siriraj Hospital and Krabi Hospital during 1990-1993 were investigated. Of 73 infants aged 0-1 month, 73% and 78% were found tob e positive for HHV-6 and HHV-7 antibodies, respectively. Antibody to HHV-6 was detected in age groups 2-3 months (38%), 4-5 months (14%), 6 months (44%), 7-11 months (66%), 1-2 year (84%), 3-4 years (82%), 5-9 years (83%), 10-19 years (83%), 20-29 years (80%), 30-39 years (67%), and over 40 years (58%), respectively. This positive rates of HHV-7 antibody in age groups 2-3 months, 4-5 months, 6 months, 7-11 months, 1-2 years, 3-4 years, 5-9 years, 10-19 years, 21-29 years, 30-39 years, and over 40 years were 50%, 21%, 10%, 37%, 47%, 82%, 75%, 72%, 72%, 67%, and 67%, respectively. At 6 months of age as the starting time of infections, 34% (14/41) and 9% (3/41) of infants had presumed primary infections of HHV-6 and HHV-7, respectively. In the follow-up study, 53% (20/38) of children were infected with HHV-6 prior to HHV-7 and only 5% vice versa. Eighty-four percent of children had acquired antibody to HHV-6 by 1-2 years old while 82% of children had acquired antibody to HHV-7 by 3-4 years old. These results suggest that HHV-6 and HHV-7 are prevalent viruses in the Thai population. The infections of both viruses begin at 6 months of age. However, infection of HHV-7 in most children begins later. The data also provided evidence that antigenic distinction between HHV-6 and HHV-7 existed with a limited cross-reactivity in an antibody test. The antibody responses to HHV-6 and HHV-7 occurred independently.

Serological response to respiratory syncytial virus infection in pediatric patients with a comparison to immunofluorescence and virus isolation.

The serological response to respiratory syncytial virus (RSV) in 125 pediatric patients hospitalized with acute lower respiratory infection was investigated by enzyme linked immunosorbent assay (ELISA) for specific immunoglobulin (Ig) A, IgG, and IgM and complement fixation (CF) test. By ELISA, a 4-fold rise in IgG titre in paired sera was most commonly found, followed by a rise in IgA and IgM titres. Investigation by ELISA and CF leads to the suggestion that major CF activity against RSV antigens resides in the IgG and not the IgA and IgM classes. No case with CF activity failed to be diagnosed by ELISA. The youngest infant who could develop seroconversion was one month old, nevertheless two children older than two years could not. When the three diagnostic methods were compared, ELISA serology was the most sensitive followed by indirect immunofluorescence (IIF) for antigen detection and virus isolation, respectively, ELISA could diagnose RSV infection in 45% of the study cases, whereas IIF and virus isolation only diagnosed 26% and 14%, respectively. Half of the cases was diagnosed by all of the three methods together.

Incidence of Mycoplasma pneumoniae, Chlamydia trachomatis, and viral infections in pneumonia cases under six months of age, Bangkok, Thailand.

The incidence of infections by Mycoplasma pneumoniae, Chlamydia trachomatis and respiratory viruses was investigated in 76 pneumonic patients aged under 6 months who attended Ramathibodi and Siriraj Hospitals in Bangkok during two study periods. M. pneumoniae infection was not found in any case from either hospital by serological diagnosis. By the isolation method, C. trachomatis infection was found in 7(16.7%) of 42 patients from Ramathibodi Hospital and 5(21.7%) of 23 patients from Siriraj Hospital with the average male:female ratio of 2.6:1; and 91.7% of the infected cases were under 3 months old. Laboratory diagnosis of respiratory virus infection was performed by indirect immunofluorescence (IIF), isolation, and by antibody detection. Data from Ramathibodi Hospital showed that 11 (24.4%), 4 (8.9%), 3 (6.7%) of the 45 patients were infected by respiratory syncytial virus (RSV), adenoviruses, parainfluenza virus type 3, and some other viruses, respectively; infection rates of 10 (32.3%), 4 (12.9%), 1 (3.2%) and 1 (3.2%) by those viruses respectively, were observed in the 31 patients from Siriraj Hospital.

Dot-ELISA for seroepidemiological study of exposure to Shigella flexneri.

A seroepidemiological study for determining serum antibodies to lipopolysaccharides (LPS) of Shigella flexneri using dot--ELISA was carried out in Krabi Province, Thailand, from January 1989 to December 1990. From 363 serum samples obtained from cord blood and from venous blood of the healthy persons aged from 6 months to over 50 years, 56% and 22%, respectively, were found to be positive for specific IgG and IgM antibodies to S. flexneri LPS. The IgG prevalence was initially detected at 3-4 years of age and then rose sharply with age. In contrast, IgM was detectable earlier, with much lower prevalence than that of IgG. The highest seroprevalence values were in the age groups 30-49 years for IgG and 15-19 years for IgM. The seroprevalence of S. flexneri infection was statistically higher among males, Buddhists, businessmen, and those with elementary education. S. flexneri infection was not associated with family income, home location, eating behaviour or water supply. These seroepidemiologic data demonstrated that most of the population in Krabi Province had been infected with S. flexneri.

Retroviral reverse transcriptase inhibitory activity in Thai herbs and spices: screening with Moloney murine leukemia viral enzyme.

Fifty-seven Thai herbs and spices were examined for their retroviral reverse transcriptase inhibitory activity. All herbs and spices were extracted with hot-water and methanol. Reverse transcriptase inhibitory activity of the extracts was determined by using Moloney Murine Leukemia Virus reverse transcriptase (M-MuLV-RT) reacted with 3H-dTTP and radioactivity measured with a scintillation counter. Eighty-one per cent (46/57) of hot-water extracts and 54% (31/57) of methanol extracts showed inhibitory activities. At a concentration of 125 micrograms/ml, 13% (6/46) of hot-water extracts, namely Eugenia caryophyllus Bullock et Harrison, Phyllanthus urinaria Linn., Terminalia belerica Roxb., Nelumbo nucifera Gaertn., Psidium guajava Linn. and Lawsonia inermis Linn., had a relative inhibitory ratio (IR) over 50%. They showed ratios of 100%, 91%, 75%, 74%, 61% and 60%, respectively. For methanol extracts, only 10% (3/31) had IR values over 50%. They were T. belerica, E. caryophyllus and N. nucifera which exhibited IR values of 83%, 54% and 54%, respectively.

Detection of Epstein-Barr virus DNA and HHV-6 DNA in tissue biopsies from patients with nasopharyngeal carcinoma by polymerase chain reaction.

A total of 34 tissue biopsies were collected from nasopharyngeal carcinoma (NPC) patients and 5 controls with non-NPC. Extracted DNA from tissue biopsies were analyzed for presence of specific gene sequences to EBV type A and type B, and HHV-6 by polymerase chain reaction (PCR). The different sequences of EBV type A and B were parts from the highly divergent forms of the EBV nuclear antigen 2 (EBNA 2). The PCR amplified products for EBNA 2A and EBNA 2B were 115 and 119 base pairs respectively whereas that of HHV-6 DNA was 776 base pairs. The results demonstrated that EBV DNA was detected in 32 of 34 cases (94.1%): 28 (82.3%) with type A, 2 (5.9%) with type B, and 2 (5.9%) with both types. EBV DNA of type A could be detected 1 (20%) of 5 controls. HHV-6 DNA was in 5 of 34 samples (14.7%) whereas HHV-6 DNA was not detectable in biopsy tissues from controls. The results show that in the NPC patient group, A type of EBV is predominant. Detection of HHV-6 DNA in patients group only might be resulted from reactivation of a latent infection or association with EBV-induction of NPC.

Prevalence of IgA specific antibodies to Epstein-Barr virus capsid and early antigens in nasopharyngeal carcinoma.

Ninety-one patients with nasopharyngeal carcinoma (NPC), and 164 age-matched healthy controls were tested for presence of IgA antibodies to Epstein-Barr virus capsid antigen (VCA) and early antigen (EA) in their sera by indirect ELISA using "EBViral DETECT" commercial test kit. IgA anti-VCA was found in 76 (83.5%) of NPC patients and 16 (9.8%) of the controls. Meanwhile, IgA anti-EA was found in 72 (79.1%) of NPC patients and 21 (12.8%) of the controls. In a parallel study by indirect immunofluorescence test (IIF), IgA anti-VCA was found in 77 of 91 (84.6%) NPC patients and 22 of 142 (15.5%) controls. The prevalence rates of anti-VCA as screened by ELISA and IIF were very similar suggesting that neither one of the two tests can be used alternatively depending on the purpose and facilities in each individual laboratory. IgA antibodies to VCA and EA were more prevalence in NPC patients than those in the controls, the finding which again supported the association between EBV and NPC as was suggested in many other reports.

Interaction of respiratory syncytial virus with human cord blood mononuclear cells.

This study on the interaction between respiratory syncytial virus (RSV) and human cord blood mononuclear cells shows that RSV replication can occur in neonatal macrophages. Although neonatal lymphocytes were not supportive of RSV replication, exposure to RSV resulted in significant inhibition of mitogen-induced transformation. Both adult and neonatal NK cell cytotoxicity were unaffected by exposure to RSV. These results suggest that RSV has preferential effects on human cord blood mononuclear cell subpopulations.

ELISA for seroepidemiological study of exposure to Vibrio cholerae of population in Krabi Province, Thailand.

Seroepidemiological study of Vibrio cholerae exposure was carried out in Krabi Province during January 1989 to December 1990 using indirect ELISA to determine serum antibodies to lipopolysaccharides (LPS) of V. cholerae. Among 363 serum samples obtained from cord blood and venous blood of healthy persons, aged from 6 months to over 50 years, 65% and 64% were found positive for specific IgG and IgM against LPS of V. cholerae, respectively. The seroprevalence of V. cholerae infection increased with age from that found at 6 months, being highest in the age groups of 30-49 years for IgG and 15-29 years for IgM. The seroprevalence of V. cholerae infection was higher among female Muslims and home-makers, and increased with the family income. The seroprevalence of cholera infection was also influenced by home location, methods of food storage and water supply. These data suggested that a large number of Krabi's population had V. cholerae infection.

Prevalence of cytomegalovirus antibodies in Thai blood donors.

Antibodies to cytomegalovirus (CMV) were determined in Thai blood donors using the complement fixation (CF) test and enzyme-linked immunosorbent assay (ELISA). A total of 203 voluntary blood donors, 181 males and 22 females, who came to the Blood Bank at Siriraj Hospital during February 1985, were investigated. Their ages ranged from 17 to 53 years (mean 24.3 +/- 6.9). Seventy-three out of 156 (46.8%) and 171 out of 203 (84.2%) sera were positive for CMV antibodies as detected by the CF test and ELISA respectively. The result of ELISA showed that 95.5 per cent of the female blood donors and 82.9 per cent of the males possessed CMV antibodies. No difference in the geometric mean titres of either sex was noted. The findings indicated that ELISA was more sensitive than the CF test for detecting CMV antibodies. The high percentage of CMV-seropositive blood donors indicates that CMV infection is common in this country. Therefore, it might be necessary to test blood donors for CMV antibodies when they are giving blood for use by certain patients, especially immunocompromised ones; the same observation applies with regard to organ donors before transplantation is carried out.

Susceptibility to varicella-zoster virus in Thai children and young adults.

During 1982-1983, susceptibility to varicella-zoster virus (VZV) in 224 Thai subjects at high risk for varicella infection was studied. The immune adherence hemagglutination (IAHA) and VZ skin test were carried out to determine VZV immunity in immunocompromised children and young adults. The history of varicella and herpes zoster from each subject was recorded. The mean +/- SD age in children and young adults were 7.3 +/- 2.8 and 19.6 +/- 1.2. Negative IAHA test was found in 74.2% of 62 children and 35.2% of 162 young adults. The increase in immune individuals was demonstrated with advancing age. Response to VZ skin test showed positive results in 79 of 162 (48.8%) young adults. The seronegativity was related to the negative VZ skin test (p less than 0.001, X2 test). Regardless of antibody detection or VZ skin test, 47 of 162 (29%) young adults were susceptible. According to the positive history of varicella and of herpes zoster obtained from 95 young adults, 80% had developed varicella during 1 to 10 years of age and 8.8% had positive history of herpes zoster. The findings suggest that the IAHA and VZ skin test should be used together for assessing VZ immunity. Varicella vaccination is highly recommended for susceptible persons who may develop severe illness.

Rubella outbreak in Thailand 1983-1984: a study at Siriraj Hospital.

The recent rubella epidemic in Thailand prevailed from September 1983 to August 1984 with its peak in March. Throughout the outbreak, approximately 70% of the cases diagnosed clinical rubella were laboratory proved. In the middle of the outbreak, accuracy of the clinical diagnosis was 75-87%, while it was 25-33% at the beginning and the end. Concerning the clinical findings in rubella, maculopapular rash may be generalized or localized, and lymphadenopathy occurred only in 40% of the clinical cases. Lymphadenopathy and respiratory symptoms appeared 3 times more frequent than those in the non-rubella cases. Rubella inapparent infection occurred in 5.14% of the contact cases. Acquisition of the disease after contact did not depend on the degree of close relationship between the index cases and the contact cases. Outcome of pregnancy and congenital rubella infection after the outbreak have to be further investigated.

Detection of varicella-zoster antibody by immune adherence hemagglutination test.

The immune adherence hemagglutination (IAHA) is a more sensitive and specific test for evaluation of humoral immunity to varicella-zoster virus (VZV) than a conventional complement fixation (CF) test. The equipment, reagents, procedure used in the IAHA are basically the same as those employed in the CF test. After VZ vaccination, seroconversions detected by IAHA test were significantly greater than those by CF test (P less than 0.01, chi 2 test). Moreover, the IAHA titers were higher about 4 times (G.M. 30.9 vs 8.2) and persisted longer than CF titers. Although the IAHA antigen is not a commercial product, the IAHA is sensitive and suitable assay for VZ antibody determination in routine serological laboratory.