Kenneth W. Walls

The ToRCH complex-perinatal infections associated with toxoplasma and rubella, cytomegol- and herpes simplex viruses

It is difficult in most cases to differentiate clinically among perinatal infections associated with Toxoplasma (To), Rubella (R), Cytomegalovirus (C) and Herpes simplex virus, type 1 or 2 (H). To evaluate this problem, sera submitted to CDC from infants (<2 yrs.) with various abnormalities were tested for all agents in the ToRCH complex, besides those requested by the physician. Antibodies to To, R and C were measured by conventional technics, and antibodies to H type 1 and 2 by microneutralization and IgM fluorescent antibody tests. Interpretation of results were complicated by such factors as prior immunization, blood transfusions and the possible acquisition of antibodies either transplacentally or from a postnatal infection. Nevertheless, serological findings suggested perinatal infection with the ToRCH agents in 61 of 192 cases (37%). The type of involvement associated with individual agents is presented in the table:

Evaluation of serologic Tests for Pneumocystis carinii antibody and antigenemia in patients with acquired immunodeficiency syndrome

Sera from 68 patients with acquired immunodeficiency syndrome and 135 controls were used to evaluate the indirect immunofluorescence and enzyme-linked immunosorbent assays for detection of antibodies to Pneumocystis carinii and a counterimmunoelectrophoresis assay for detection of circulating Pneumocystis antigen. None of these assays was helpful in the diagnosis of P. carinii pneumonia. An improved assay for antigenemia is needed to differentiate between clinical and subclinical infection.

Diagnosis of acute acquired toxoplasmosis with the enzyme-labelled antigen reversed immunoassay for immunoglobulin M antibodies.

The reversed enzyme-labelled antigen immunoassay (R-EIA), based on the capture of serum immunoglobulin M antibodies (IgM) and subsequent addition of Toxoplasma gondii soluble antigen tagged with peroxidase and substrate, was evaluated comparatively with the IgM-indirect immunofluorescence test (IgM-IIF) for the detection of anti-toxoplasma IgM antibodies in sera from individuals with diagnosed acute acquired toxoplasmosis. Additional serum groups from normal healthy individuals and sera presenting possible nonspecific reactivities were also evaluated. Complete specificity of R-EIA was shown. There was no correlation between the magnitude of R-EIA results and IgM-IIF titers, but a positive (although not linear) correlation was found between R-EIA and the IgM-IIF titers obtained after adsorption of sera with Staphylococcus aureus protein A. Direct labelling of the antigen by a simple coupling technique facilitated the assay standardization and improved its signal-to-noise ratio.

Computer-assisted multiple categorization of absorbance values in ELISA through pictorial emulation of 96-well plates☆

A simple algorithm is proposed by which multiple categorization of absorbance values from ELISA plates is performed under a microcomputer control. The printed output is a pictorial emulation of a 96-well plate with the color intensities represented for each reaction. Although the method is presented as a colorimeter computer interfaced system, a provision for manual entry of absorbance values via keyboard is also included. Simulation is based solely on the magnitude of absorbance values. Therefore, it is possible to utilize any enzyme/substrate combination within the range of filters of the colorimeter. We have tested the present system for titration of anti-malarial antibodies in human serum and for the screening of mouse hybridoma culture supernatants.