ABSTRACT
The antibody patterns of HIV-1 IgG3, IgG and IgA and of HIV-1 p24 antigen were investigated in Thai infants born to mothers infected with HIV-1. In the 17 HIV-1 infected infants, anti-HIV antibodies were detected continuously over a period of 15-18 months and a high level of specific IgG3 subclass was observed. Anti-HIV IgA could be detected at 6 months of age whereas p24Ag was detected at 2 months. In 79 uninfected infants, maternal anti-HIV IgG gradually decreased over 9 months whilst specific IgG3 decayed rapidly during the first 6 months. Both p24Ag and anti-HIV IgA were not found in these uninfected infants. Thus, the disappearance of anti-IgG3 subclass antibodies within 6 months can predict whether infants are uninfected whereas the persistence of anti-HIV IgG and IgG3 subclass antibodies, the production of anti-HIV IgA antibody and the presence of p24Ag appear as an adjunct to the diagnosis of HIV vertical transmission. The necessary assays are relatively simple and could be performed individually.
Subject(s)
Cohort Studies , HIV Antibodies/blood , HIV Core Protein p24/blood , HIV Infections/blood , HIV Seroprevalence , HIV-1/immunology , Humans , Immunoglobulin A/blood , Immunoglobulin G/blood , Infant , Infant Welfare , Predictive Value of Tests , Sensitivity and Specificity , Thailand , Time FactorsABSTRACT
In order to develop a reliable and inexpensive serodiagnostic method to be used for anti-HIV antibody detection in Thailand, recombinant envelope (TM or gp41 subunit) protein of HIV-1 subtype E was produced from prokaryotic cell (Escherichia coli) as the source of antigen in enzyme immunoassay (TE diagnostic EIA kit). HIV-1 gp41 subunit of subtype E was successfully expressed in E. coli in the form of polyhistidine-tagged proteins, comprising of rgp41A (601 bases N-terminal half of TM or 25kDa) and rgp41B (560 bases C-terminal half of TM or 24 kDa) by using an expression vector, pBAD/His C. The amount of protein, dilution of sera, and anti-human IgG labeled HRP used in the EIA test optimized by a checker board titration of the protein and seropositive or seronegative sera, were 5.0 microg/ml, 1:300, and 1:4,000, respectively. The blinded test evaluation of TE-diagnostic EIA in 500 seropositive and 500 seronegative sera which have been simultaneously tested by two available commercial kits and compared with our TE diagnostic EIA, gave 99.6% sensitivity and specificity. The other known genetic subtypes sera such as subtype A (n=5), B (n=9), C (n=4) and D (n=5) were also positive with this EIA. The estimated manufacturer cost per test of rgp41 based anti-HIV antibody detection EIA or TE-diagnostic EIA was about 15 baht. This recombinant envelope (gp41 or TM) protein from HIV-1, which can be produced in large quantities without any hazards from growing the virus and has lower cost to produce anti-HIV antibody serological diagnostic kit, should be considered as an HIV screening test in Thailand.