Comparison of immunofluorescence and immunoperoxidase staining for identification of rubella virus isolates

Comparative efficacy of fluorescent antibody test, immunoperoxidase test and enzyme linked immuno sorbent assay in detection of rotavirus in cell culture

Rotavirus is prevalent worldwide and has been established as a leading cause of mortality due to severe diarrhoea in neonates. Isolation of the virus is a gold standard method for confirmation of rotavirus infection in the host. Propagation of rotavirus in cell culture is a challenge as in many instances the virus does not produce detectable cytopathic effect. This study was undertaken to evaluate the efficacy of fluorescent antibody test (FAT), immunoperoxidase test (IPT) and sandwich ELISA (S-ELISA) to detect rotavirus antigen propagated in MA 104 cell line. The intensity of fluorescence and colour development for I-FAT and I-IPT was categorized and the ELISA OD values were analyzed. The overall mean of detection were 5.16 ± 0.47, 5.16 ± 0.54 and 5.66 ± 0.33 for I-FAT, I-IPT and S-ELISA, respectively. Significantly less number of samples were positive in the initial one or two passage, which increased up to 100 % from third/fourth passage onwards. The study concluded that I-FAT, I-IPT and S-ELISA were equally effective in detecting propagated rotavirus in cell line, and the former two tests are suitable for in situ demonstration of the virus while the later could be used to assay antigen in cell culture fluid.

Sensitivity and efficiency of four immunohistochemical methods as defined by staining of artificial sections

Direct (DIF) and indirect (IIF) immunofluorescence, indirect immunoperoxidase conjugate (IPC) and unlabelled antibody peroxidase antiperoxidase (PAP) staining was performed on sections of artificial substrate containing different concentrations of human immunoglobulin (Ig)A or IgG. Detection sensitivity, in terms of the lowest amount of discernible antigen, was evaluated by direct microscopy and by microphotometry. Staining efficiency (signal-to-noise ratio) was evaluated by microphotometry. Only minor differences in antigen detection sensitivity were found when IPC and PAP were compared with DIF and IIF under appropriate conditions. The sensitivity of DIF was only marginally improved by raised conjugate concentration and prolonged incubation time. Microphotometry of DIF on ethanol-fixed IgA substrate revealed that the staining intensity increased proportionally with the antigen concentration whereas on formaldehyde-fixed substrate a progressive masking of the antigen was indicated which, however, could be overcome by applying raised conjugate concentration and prolonged incubation time. Such antigenic self masking was of relatively little importance to IPC and PAP staining, probably because of the inherent amplification in these methods. An additional masking effect due to extraneous protein was revealed by DIF when ethanol-fixed sections had been soaked in bovine serum albumin and postfixed with formaldehyde; unmasking was achieved by proteolytic treatment of the sections.

Quantitation of immunoglobulin- and peptide hormone-producing cells in gastrointestinal mucosa. Comparison of direct immunofluorescence and the unlabelled antibody peroxidase--antiperoxidase method

Direct immunofluorescence (DIF) and the unlabelled antibody peroxidase--antiperoxidase (PAP) methods were compared on a quantitative basis with regard to visualization of IgA immunocytes and gastrin cells in human gastric mucosa, and secretin cells in canine duodenal mucosa. With both DIF and PAP, two serial sections from 13 biopsy specimens were evaluated for each cell type--thus keeping tissue preparation the same with both staining methods. The three cell types were well visualized regardless of method, and there was no significant difference between cell numbers recorded with the DIF or PAP. When blind duplicate counts were obtained with an interval of three weeks, comparisons of weighted differences and the Kendall's rank correlation test indicated good precision; the reproducibility of duplicate enumerations with each method was comparable to that between the two methods. It was concluded that DIF and PAP are equally applicable for studies of these three cell types under the conditions used in this investigation.

Alpha interferon administration to infants with congenital rubella

Three infants with congenital rubella syndrome were given human leukocyte (alpha) interferon at doses of 2 x 10(5) to 7 X 10(5) U/kg per day for 10 days. A transient decrease in pharyngeal virus excretion was observed with treatment. No significant side effects were associated with the administration of human leukocyte interferon to these infants.