Pretreatment of Test Sera with Three Kinds of IgG-Adsorbents Did Not Improve Sensitivity in the Indirect ELISA to Detect Anti-Dengue IgM Antibodies

Sera from clinical dengue cases in Malaysia were examined to detect IgG- as well as IgM-class anti-dengue antibodies by the indirect ELISA with or without treatment by 3 kinds of IgG-adsorbents. Relative adsorption factor (AF) as determined by the decreased ELISA-OD ratio was 0.42-0.58 for IgG and 0.33-0.39 for IgM, respectively. After IgG-adsorbents treatment, however, the number of anti-dengue IgM-positive serum specimen decreased from 11-20% of the untreated control. The result indicated that pretreatment of test sera with IgG-adsorbents did not improve or even reduced the sensitivity to detect anti-dengue IgM antibodies in the test sera

Comparative Assay on Anti-dengue IgM Antibodies by the Indirect ELISA and IgM-capture ELISA

Anti-dengue IgM antibodies were measured by the indirect ELISA and IgM-capture ELISA using type 2 and 3 dengue antigens on dengue patients\u27 sera. The assay results depended more strongly on the assay method than the serotype of dengue antigen used in the test. The results indicated that amounts of antibodies directed against virion and nonstructural viral antigen were not uniform in individual test serum

Comparative Assay on Dengue IgM-ELISA Using Reagents From 2 Sources

In order to distribute dengue IgM-capture ELISA to the peripheral laboratories, supply of key reagents should be established by local production. In this study, comparative IgM-capture ELISA was carried out on a total of 237 sera using key reagents from 2 sources. The current set consisted of suckling mouse brain (SMB)-derived dengue type 2 (D2) antigen and a D2 monoclonal antibody (MAb) supplied from the United States. While an alternative set was supplied by one of the authors, consisting of tissue culture-derived dengue antigen (TCA) and MAb established in USM. When the IgM-ELISA results were compared with those by the hemagglutination-inhibition (HI) test as a gold standard, the sensitivity was 50.0% by the current set and 75.0% by the alternative set of reagents, respectively. While the specificity was 95.2% by the current set and 90.3% by the alternative set of reagents. The results showed that the alternative set of reagents can effectively be used in dengue IgM-ELISA and is significantly more sensitive than the current set of reagents (Chi SQR=12.26, PP>0.1) at 10% risk

Comparison of Two Different Methods for the Purification of Polymerase Chain Reaction (PCR) Products Used in Direct Sequencing, in an Applied Biosystems 373A DNA Sequencing System

This study was carried out to compare the efficiency of two different purification methods used for removing excess primers and short oligonucleotides from PCR products. Our aim was to sequence PCR product directly. The two different purification methods were micro filter spin unit system (Millipore) and Quick Spin Column (Boehringer Mannheim Biochemica). The results indicated that the purification method using microfilter spin unit system was better and yielded better suquencing pattern compared to quick Spin Column

Use of the Reverse Transcriptase Polymerase Chain Reaction for Diagnosis on Dengue Virus Infection Compared to IgM-ELISA

Applicability of the reverse transcriptase polymerase chain reaction (RT-PCR) was evaluated as a routine rapid diagnostic test for dengue virus infection. A total of 160 acute phase sera from patients with clinical diagnosis of dengue fever was examined both by the RT-PCR and IgM-ELISA. Of these, 9 (6%) were positive for both RT-PCR and IgM-ELISA, 61 were positive for IgM-ELISA only and 31 (19%) for RT-PCR only. Both techniques gave negative results in the remaining 59 (37%) specimens. The diagnostic efficiency of IgM-ELISA was statistically better than the RT-PCR even when the specimens were collected on the 3rd or 5th days of the disease. Considering the operational cost in the tests, the acute serum specimens should first be tested by the IgM-ELISA, followed by the RT-PCR on the negative specimens in order to increase the diagnostic efficiency with reasonable cost

Genotypes of Japanese Encephalitis Virus Isolated in Three States in Malaysia

Two hundred forty nucleotides from the pre-membrane gene region of 12 Japanese encephalitis virus (JEV) strains isolated from three different regions of Malaysia from 1993 to 1994 were sequenced and compared with each other and with the JEV strains from different geographic areas in Asia. These 12 Malaysian isolates were classified into two genotypes. The four JEV strains isolated from Sarawak in 1994 and the four JEV strains isolated from Sepang, Selangor in 1993 were classified into one genotype that included earlier isolated strains from Malaysia (JE-827 from Sarawak in 1968 and WTP/70/22 from Kuala Lumpur in 1970). The four JEV strains from Ipoh, Perak in 1994 were classified into another genotype that included JEV strains isolated from northern Thailand and Cambodia. In an earlier report, 10 JEV strains from Sabak Bernam, Selangor in 1992 were classified into the largest genotype that included strains isolated in temperate regions such as Japan, China, and Taiwan. The data indicate that at least three genotypes of JEV have been circulating in Malaysia