Evaluation of a new fourth-generation microwell enzyme-linked immunosorbent assay for detection of HIV-1 subtype B and E antibodies.

The recent fourth-generation enzyme-immunoassays have been used to increase the sensitivity for detecting HIV-1 antibodies and reduce the window period of HIV infection. The HIV antigens utilized in those assays were prepared from HIV-1 clade B which is different from HIV-1 subtypes circulating in Thailand. We evaluated 323 HIV-1 seropositives either B or E subtype to determine whether they were detected with the new combined anti-HIV and the p24 Ag assay. Under evaluation we found that this enzyme immunoassay manufactured by Organon Teknika showed the high sensitivity and specificity with a greater delta (delta) value with B than E subtypes samples (+15.29 vs +5.73).

Chlamydia pneumoniae in community-acquired pneumonia.

Chlamydia pneumoniae has been established recently as an important human respiratory pathogen. The aim of this study was to define the prevalence of C. pneumoniae in community-acquired pneumonia. We prospectively investigated adult patients who were treated as inpatients and outpatients. Acute and convalescent serum samples were obtained from each patient. Serological diagnosis of C. pneumoniae infection was determined by enzyme-linked immunosorbent assay (ELISA). Eighty paired sera were tested for C. pneumoniae-specific IgM, IgG and IgA. Twenty-one patients (26.2%) had serological results compatible with acute C. pneumoniae infection. Eighteen (85.7%) of these infected patients were C. pneumoniae-specific IgM positive, three had a seroconversion of IgA and two had a four-fold or greater increase in C. pneumoniae-specific IgG antibody titer. The most common clinical manifestations of community-acquired pneumonia due to C. pneumoniae were fever (100%), cough (100%), chest pain (47.6%) and shortness of breath (42.9%). Physical examination revealed crackle in 85.7 per cent of the cases. These findings suggest that C. pneumoniae is a common cause of community-acquired pneumonia in Thailand.

HIV-2 infection in Thailand.

Neither the seroprevalence of HIV-2 nor the sensitivity of enzyme immunoassays for the detection of antibodies to this retrovirus have been defined in Thailand. We, therefore, Investigated these enigmas using banked sera previously screened for HIV-1 by a test that did not distinguish between HIV-1 and HIV-2. All 1,013 HIV-seroreactive specimens were positive to HIV-1 on retesting, and 740 (73%) were reactive to both HIV-1 and HIV-2. The thirty-six samples that reacted with HIV-2 at a titer of > or = 1:4,096 were further tested to discriminate between HIV-1 and HIV-2 by immunoblot assays incorporating HIV-2 recombinant proteins. One specimen was untypeable, but all others were determined to be HIV-1. Seventy-three percent of sera from Thai HIV-1 infected subjects cross-reacted with HIV-2, but not a single case of HIV-2 infection could be confirmed. The finding suggests low prevalence of HIV-2 infection in Thailand and that current testing for HIV-2 antibody is not necessary in Thai population.

Application of dried blood spot specimens for serologic subtyping of human immunodeficiency virus type 1 in Thailand.

Dried blood spot (DBS) specimens were assessed as an alternative to plasma for human immunodeficiency virus type 1 (HIV-1) serotyping by V3 loop peptide enzyme immunoassay. Nested PCR capable of distinguishing HIV-1 subtypes B and E was used as the reference standard. Ninety-two percent of DBS samples were typeable as either HIV-1 subtype B or E. Serotype results with DBS and plasma were identical for 254 of 257 specimens. A simple DBS collection method provides a convenient alternative for conducting HIV-1 serotype surveillance while retaining sensitivity and specificity.