Serology has been a fundamental tool to prevent post-transfusional infection with human immunodeficiency virus (HIV) and for epidemiological surveys, the first step to attempt control of the pandemia. Enzyme immunoassay is in widespread use. Nevertheless, simpler methods are needed in many countries, where laboratory facilities and trained personnel are limited, and HIV prevalence is high. The evaluation of a simple and noninstrumented HIV antibody test is presented here. The test employs synthetic antigens of HIV-1 and HIV-2 attached to the teeth of a polystyrene comb, which fit into the wells of standard microtiter plates where samples are diluted. Captured antibodies are developed with colloidal gold-labeled Protein A. Three seroconversion panels plus 662 samples were tested, including HIV-1 and HIV-2-infected individuals, normal blood donors, and a noninfected baby born to a seroreactive mother. When compared with enzyme-linked immunosorbent assay (ELISA) and Western blot, the dipstick showed 100% sensitivity and 98.7% specificity. The simplicity of result evaluations and excellent reagent stability make the dipstick suitable for small blood banks and for epidemiological surveys.
The use of monoclonal antibodies in the development of a third generation microtitration plate enzyme immunoassay for the detection of hepatitis B virus (HBV) is described. These antibodies were tested either alone or in combination with polyclonal antibodies raised in rabbit. Horseradish peroxidase was employed in the conjugates and 3,3',5,5'-tetramethylbenzidine was used as the enzyme substrate. Effect of type and concentration of antibodies used in the coating solution and in preparing conjugates as well as reaction time are discussed. The designed test employs a 100-microliters sample, with an overall incubation time of 3.5 hr. Serum or plasma (EDTA or citrate as anticoagulant) can be used. The sensitivity limit of the test was 0.4 ng/ml for subtype ad and 0.5 ng/ml for subtype ay. When used as screening test, 99.6% specificity was obtained; predictive value was 97.5% for a positive result and 99.8% for a negative result. According to the performance of the test, it seems to be suitable for diagnosis in routine laboratory and screening in blood banks.
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