Immunoperoxidase localization of herpes zoster virus and simian virus 40 in cell culture

Assessment of virus infectivity by the immunofluorescent and immunoperoxidase techniques

The immunofluorescent and immunoperoxidase cell-counting techniques were comparable in precision and reproducibility for the quantitative assessment of influenza virus infectivity. The dose-response function was linear with each procedure, and comparable results were obtained for estimating neutralizing antibodies in antiviral serum.

Use of immunoperoxidase for the rapid identification of human myxoviruses and paramyxoviruses in tissue culture

The immunoperoxidase method, using commercially available antisera, was compared with standard virological methods for the identification and typing of 77 isolates of human myxoviruses and paramyxoviruses. Results of typing using neutralization tests and the immunoperoxidase technique were identical for 76 of the 77 isolates. With the immunoperoxidase method there was one false negative reaction, but no false positive reactions. Cross-reactivity between influenza A (soluble) and A(2)/HK antisera with influenza A isolates was noted, but did not interfere with the interpretation of results. It is concluded that the immunoperoxidase method is ideally suited for the rapid identification and typing of common human respiratory viruses on a routine basis. It offers a number of decided advantages over both immunofluorescence and standard virological methods.

Comparison of techniques and immunoreagents used for indirect immunofluorescence and immunoperoxidase identification of enteroviruses

Peroxidase-conjugated antibodies were found to be as sensitive as those conjugated to fluorescein-isothiocyanate (FITC) for identification of selected enterovirus types by the indirect technique. Peroxidase conjugates, however, were found to give fewer nonspecific reactions. The reasons for the higher specificity of the immunoperoxidase technique appear to be related to the relative size, charge, and uniformity of the preparations. Monomers of peroxidase-conjugated globulin are larger than those of FITC conjugates, but the latter readily form aggregates. This was shown by chromatography on Sepharose 6B columns: various FITC-conjugated globulins eluted before those conjugated to peroxidase and before (125)I-labeled immunoglobulin G. The net charge of the conjugates was determined by adsorption to ion-exchange columns. FITC-labeled globulins had a negative net charge, eluting at pH 5.1 from diethylamino-ethyl-Sephadex A-50 columns. Peroxidase conjugates were not retained by either cationic or anionic exchangers at pH values ranging from 4.0 to 10.5. Further, the fluorescein/protein ratios of FITC conjugates from different commercial sources and of those prepared in the laboratory were found to be variable; higher fluorescein/protein ratios (>2:1) give a higher degree of nonspecific reactions, whereas the peroxidase/protein ratio does not appear to affect specificity. These characteristics of peroxidase conjugates make the immunoperoxidase technique easier to standardize and more reliable for enterovirus identification than the immunofluorescence technique.

Immunoperoxidase stain of measles antigen in tissue culture

A specific electron microscopy staining technique for measles antigen has been developed by using Vero cells infected with a subacute sclerosing panencephalitis (SSPE) measles virus strain and fixed in glutaraldehyde or formaldehyde. Peroxidase-labeled antibody was prepared according to the method of Avrameas (4). Sera from SSPE patients with high measles antibody titer as well as normal human sera with and without measles antibody were used. With both fixatives, specific labeling was obtained on the surface of infected cells, on the budding site, and on complete viral particles. The cell membrane staining sometimes had a patchy distribution in that the reaction was most intense on the surface projections in front of each nucleocapsid. This suggests modification of the cell membrane in association with the nucleocapsids. In contrast, no label was detected on the membranes of the cells during the latent period from penetration through maturation of the virus. In formaldehyde-fixed cultures, cytoplasmic inclusions were stained, and this label was located on the "fuzzy" material around the nucleocapsids. The smooth type of nucleocapsids, mainly seen in the nucleus, were never labeled. These findings suggest that the antigenic nature of the "fuzzy" nucleocapsids in the cytoplasm may be different from that of the "smooth" nucleocapsids. The immunoperoxidase method gives good resolution of viral antigenic sites at high magnifications under electron microscopy and may be of value in studies on the immunopathogenesis of SSPE and other chronic viral infections.

Coupling of peroxidase to poliovirus antibody: characteristics of the conjugates and their use in virus detection

Antibody to poliovirus type 1 (Po-1) was coupled to peroxidase by use of glutaraldehyde or 4, 4' -difluoro,3, 3' -dinitro diphenyl sulfone. Glutaraldehyde was found to be the superior coupling agent, yielding conjugates that had up to 2.8 x 10(4) enzyme units/ml (75% of total enzyme input). Conjugates migrated as a single band when centrifuged in sucrose density gradients, demonstrating that the purification procedure used was effective in removing both noncoupled enzyme and heterogeneous antibody components. Conjugates were specific for Po-1 and did not adsorb to cells infected with unrelated enterovirus types. Adsorption of conjugates to Po-1-infected cells was demonstrable within 6 h postinfection.