Rapid assay for simultaneous detection and differentiation of immunoglobulin G antibodies to human immunodeficiency virus type 1 (HIV-1) group M, HIV-1 group O, and HIV-2.

A rapid immunodiagnostic test that detects and discriminates human immunodeficiency virus (HIV) infections on the basis of viral type, HIV type 1 (HIV-1) group M, HIV-1 group O, or HIV-2, was developed. The rapid assay for the detection of HIV (HIV rapid assay) was designed as an instrument-free chromatographic immunoassay that detects immunoglobulin G (IgG) antibodies to HIV. To assess the performance of the HIV rapid assay, 470 HIV-positive plasma samples were tested by PCR and/or Western blotting to confirm the genotype of the infecting virus. These samples were infected with strains that represented a wide variety of HIV strains including HIV-1 group M (subtypes A through G), HIV-1 group O, and HIV-2 (subtypes A and B). The results showed that the HIV genotype identity established by the rapid assay reliably (469 of 470 samples) correlates with the HIV genotype identity established by PCR or Western blotting. A total of 879 plasma samples were tested for IgG to HIV by a licensed enzyme immunoassay (EIA) (470 HIV-positive samples and 409 HIV-negative samples). When they were tested by the rapid assay, 469 samples were positive and 410 were negative (99.88% agreement). Twelve seroconversion panels were tested by both the rapid assay and a licensed EIA. For nine panels identical results were obtained by the two assays. For the remaining three panels, the rapid assay was positive one bleed later in comparison to the bleed at which the EIA was positive. One hundred three urine samples, including 93 urine samples from HIV-seropositive individuals and 10 urine samples from seronegative individuals, were tested by the rapid assay. Ninety-one of the ninety-three urine samples from HIV-seropositive individuals were found to be positive by the rapid assay. There were no false-positive results (98.05% agreement). Virus in all urine samples tested were typed as HIV-1 group M. These results suggest that a rapid assay based on the detection of IgG specific for selected transmembrane HIV antigens provides a simple and reliable test that is capable of distinguishing HIV infections on the basis of viral type.

In vitro selection of a high affinity antibody to oestradiol using a phage display human antibody library.

We have isolated a monoclonal antibody binding to oestradiol with high affinity (3.7 nM), and exhibiting a better than 1000-fold selectivity in binding to other steroids. A high affinity antibody with good specificity is essential for the accurate determination of circulating oestradiol levels. To date, conventional hybridoma technology has not yielded a reagent of sufficiently high affinity and specificity for this ligand. The aim of this study was to investigate whether such a reagent was accessible through the engineering of antibodies on the surface of filamentous phage. Antibodies were isolated from a large repertoire of single chain Fv fragments (scFv) derived from non-immunised human donors, with selection and screening procedures biased to favour those binding to free oestradiol. This resulted in an antibody with nanomolar affinity for oestradiol, while affinities for related steroids are in the micromolar range. The relative lack of reactivity for steroids substituted at either end of the molecule suggests that this antibody is unique among anti-steroid monoclonal antibodies in lacking a 'blind-spot'. Our results demonstrate that phage display can provide solutions to problems that have so far proved intractable using conventional hybridoma technology.

Screening for gestational diabetes with the one-hour 50-g glucose test.

A one-year experience of screening for gestational diabetes is reported. Patients with any of seven risk factors were screened at the time of prenatal registration. Those without risk factors, and those not found to be diabetic by 24 weeks' gestation, were tested later in pregnancy. Of 4116 patients, 77% had at least one risk factor. The prevalence of diabetes in patients with risk factors was significantly greater than among those with no risk factors (P less than .001). Of 936 patients who had no risk factors, four were found to have diabetes. Multiple logistic regression analysis suggested that family history, obesity, and age over 25 years contributed significantly to the prediction of gestational diabetes. More than 10% of gestational diabetics had screening values between 135-139 mg/dL. Among patients whose early screening values were elevated and whose initial glucose tolerance tests were normal, the odds of being classified ultimately as a gestational diabetic were 7.3 times that of patients whose initial screening tests were normal. Selective screening based on risk factors including maternal age may enhance detection of diabetes early in gestation.