Response to JE vaccine among HIV-infected children, Bangkok, Thailand.

Since 1990, Japanese encephalitis (JE) vaccine has been part of EPI in northern Thailand, where there is a high prevalence of JE and HIV infection. To evaluate the immunogenicity and safety of JE vaccine among HIV-infected children, we conducted a retrospective study of HIV-infected and uninfected children who received 2 doses of JE vaccine at 12 months of age. Pre- and post-immunization plasma specimens were tested by plaque reduction neutralization for antibody levels to JE and dengue(1-4) viruses; titers of > or =10 were considered positive.

Possible occurrence of a genetic bottleneck in dengue serotype 2 viruses between the 1980 and 1987 epidemic seasons in Bangkok, Thailand.

Cocirculation of two genetic subtypes of dengue serotype 2 viruses was first observed in the 1980 epidemic season in Thailand. To further delineate the evolutionary history and the contribution of these subtypes to subsequent epidemics, we determined the envelope glycoprotein gene sequence of 20 dengue serotype 2 viruses isolated from infected patients during 1987 and compared them with those derived from earlier years. Subtype IIIa strains represented the majority (18 of 19) of dengue type 2 viruses derived from Bangkok metropolitan area, whereas all three strains from a province in the northeastern region belonged to subtype IIIb, indicating uneven local distribution of dengue subtypes within the same year.

Cost benefit analysis of Japanese encephalitis vaccination program in Thailand.

Using decision analysis, we estimated benefits, risks, and costs of implementing the Japanese encephalitis (JE) vaccination program in children aged 18 months and 6 years in Thailand. The costs for inclusion of JE vaccine into the routine immunization program at 18 months and 6 years are $2.16 and $3.

A field study on Nakayama and Beijing strains of Japanese encephalitis vaccines.

A field study to compare the immune response of children aged 1-6 years to Nakayama and Beijing strains JE vaccines was carried out in Mae Hong Son Province, northwest Thailand, where there was low incidence of JEV infection. The first and second dose of each vaccine was given 1-2 weeks apart and the third dose was 1 year after the second dose. Seroconversion rate was similarly high, about 94% in both groups of vaccinees.

Storage stability of dengue IgM and IgG antibodies in whole blood and serum dried on filter paper strips detected by ELISA.

Blood specimens from 133 patients clinically diagnosed as dengue virus infection by physicians in Nakhon Phanom Hospital, Thailand, were examined to detect anti-dengue IgM and IgG antibodies by antibody capture ELISA. The blood specimens were divided into 3 types of storage; (1) frozen serum aliquots, (2) whole blood dried on filter paper strips, and (3) sera dried on filter paper strips. These specimens were stored for the periods of 1, 3, 4, and 5 months, at -20 degrees C in the case of frozen serum aliquots, or at room temperature in the case of specimens dried on filter paper strips, before examined in paralleled by the ELISA.

Comparative nucleotide and deduced amino acid sequence of the envelope glycoprotein gene among three dengue virus type 2 strains isolated from patients with different disease severities in Maha Sarakham, northeast Thailand.

The nucleotide (nt) sequence of the envelope glycoprotein (E) gene of dengue virus type 2 was determined by the primer-extension dideoxy chain-termination method for 3 dengue virus type 2 (D2) strains which had been isolated from patients with dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS), in Maha Sarakham, Northeast Thailand, in 1986-1987. Their nt sequences were essentially the same except for a single silent nt replacement in each DHF and DSS strain compared with DF strain. Therefore, these 3 strains possessed identical deduced amino acid (AA) sequences in their E protein.

Failure of high-dose methylprednisolone in established dengue shock syndrome: a placebo-controlled, double-blind study.

Objective: Steroids are widely used in Thailand and other dengue-endemic countries to treat severe dengue shock syndrome. This study was designed to determine whether a single high dose of methylprednisolone will reduce mortality in children with dengue shock syndrome who did not respond to simple fluid and plasma replacement therapy.

Methods: A prospective, randomized, double-blind, controlled trial was conducted in two hospitals in Khon Kaen Thailand during June to September in 1987 and 1988.

Mapping of functional epitopes of Japanese encephalitis virus using monoclonal antibodies.

Epitopes involved in the important functions, hemagglutination (HA) and neutralization (NT), were mapped on Japanese encephalitis (JE) virus proteins by using monoclonal antibodies (MAbs). Fourteen MAbs raised against Nakayama-Yoken strain of JE virus characterized by hemagglutination inhibition (HI) and plaque reduction neutralization test (PRNT) were used to map the epitopes on the JE proteins by Western blot analysis in which non-reducing conditions were used for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). With these MAbs, at least 8 functional epitopes were demonstrated comprising (i) epitopes recognized by 5 MAbs which gave strong HI but weak NT activities and were mapped on the envelope (E) 53 kDa protein; (ii) epitopes recognized by 2 MAbs which showed weak HI but strong NT activities and were mapped also on the E protein; (iii) epitopes recognized by 2 MAbs which possessed weak HI but no NT activities and were mapped on the E protein; (iv) an epitope recognized by 1 MAb which gave weak NT and no HI activities and was mapped on the nonstructural protein 5 (NS5); (v) an epitope recognized by 1 MAb which showed activities similar to (i) but was mapped on both E and NS5; (vi) an epitope recognized by 1 MAb which had high activities to both HI and NT and was mapped on E and NS5; (vii and viii) epitopes recognized by 1 MAb which also gave low HI but high NT, and strong HI as well as strong NT activities respectively, but their location could not be demonstrated by SDS-PAGE under non-reducing condition.

Epidemic of fever of unknown origin in rural Thailand, caused by influenza A (H1N1) and dengue fever.

In the late summer (rainy season) of 1987, a sharp outbreak of fever of unknown origin (FUO) in rural southern Thailand was investigated by a field epidemiology team. In a random survey of households, 40 percent of the children and 20 percent of adults were reported to have had febrile illnesses within the last month. There was at least one death, possibly from Reye's syndrome.

Risk factors in dengue shock syndrome: a prospective epidemiologic study in Rayong, Thailand. I. The 1980 outbreak.

In January 1980, the municipal area of Rayong, Thailand, and contiguous suburban villages were chosen for a long-term study on dengue epidemiology. From 3,185 children randomly sampled in schools and households, the population prevalence of neutralizing antibody to the four dengue serotypes was estimated. To estimate the incidence of infection with each dengue virus serotype (dengue seroconversions), first grade children were re-bled in January 1981 (cohort study).

Original antigenic sin in dengue.

Sequential blood samples were obtained from eight Thai children before, during and 3-5 months after hospitalization for dengue shock syndrome. All patients experienced a secondary-type antibody response as evidenced by hemagglutination-inhibition antibody responses in acute and convalescent sera. Dengue 2 viruses were recovered from two patients.

Serological and virological studies on patients with dengue hemorrhagic fever (DHF) in Chanthaburi province, Thailand. II. Serological characteristics of viruses isolated from DHF patients using a clone of Singh's Aedes albopictus cells.

Four strains of dengue (DEN) virus were isolated using C6/36 cells, a clone of Singh's Aedes albopictus cells, from acute phase sera of DHF patients in Thailand in 1978. The isolates grown and passaged in C6/36 cells were not neutralized appreciably by standard rabbit antisera against each of the 4 types of DEN virus, but their serotypes could be identified by complement fixation (CF) tests. After the 4th or 10th passage in suckling mouse brain (SMB), however, three of the four strains showed type-specific reactions in neutralization (N) tests against the standard antisera.

Seroepidemiologic study of arbovirus infections in the north-east and south of Thailand.

Blood specimens were collected from villagers in Khon-Kaen province, in the north-eastern region, and in Songkhla province, in the southern region of Thailand in the pre- and post-epidemic seasons of hemorrhagic fever. The hemagglutination inhibition antibody titers of the specimens were measured against dengue virus type 2, type 4, Japanese encephalitis virus and chikungunya virus. In general, Khon-Kaen villagers showed higher levels of HI antibodies against these arboviruses than Songkhla villagers and in both areas the antibody level against chikungunya virus, a group A arbovirus, was usually much lower than those against group B arboviruses.