Critical factors in an enzyme immunoassay (ELISA) for antibodies to mouse thymic virus (MTLV).

Mouse thymic virus (MTLV; murid herpesvirus 3) is a naturally occurring herpesvirus of mice. Critical variables in an enzyme immunoassay (ELISA) for antibodies to mouse thymic virus (MTLV) were assessed. High protein binding plates proved unsuitable. For storing coated plates, the most consistent results were obtained when coated plates were washed and stored with coating buffer (phosphate buffered saline, PBS) at -70 degrees C. Storage of antigen at -20 degrees C was unsatisfactory, although coated plates could be stored at -20 degrees C for at least 1-2 weeks. In performing the ELISA, vigorous washing and blocking were critical. However, substituting isotonic (0.9%) saline for PBS in washing solutions gave reliable results at considerable cost savings. For blocking, and as sample diluent, a modification of 'BLOTTO' (5% nonfat dry milk and 0.2% Tween 20) was most satisfactory.

[Characteristics of the biological and antigenic properties of reference strains of the influenza B virus at various periods of isolation]. / Kharakteristika biologicheskikh i antigennykh svoistv étalonnykh shtammov virusa grippa B razlichnykh periodov vydeleniia.

The results of a comparative analysis of biological and antigenic properties of reference influenza B virus strains, B/Lee/40, B/Singapore/222/79, and B/USSR/100/83, are presented. The most marked changes were found in the antigenic properties of hemagglutinin and neuraminidase. Hemagglutinins of the strains under study were found to have both common antigens and qualitatively different strain-specific determinants. The degree of intensity of immunity to the challenge B/Singapore/222/79 Pm+ virus corresponded to the intensity of antigenic relationship in the strains under study.

A study of candidate rabies vaccines for a national reference preparation for the evaluation of antigenic potency.

An unconcentrated and a concentrated lot of rabies vaccine prepared in Syrian hamster kidney cell culture from the Vnukovo-32 strain have been examined for their suitability as national reference preparations for rabies vaccine. The antigenic potencies of the preparations were assessed by the NIH test using both fixed and street strains of rabies virus and by the method of antibody induction. The candidate vaccines were calibrated in comparative assays with the WHO 3rd International Reference Preparation of Rabies Vaccine (IRP3). The correlation between the level of virus-neutralizing antibody and the resistance of mice to intracerebral challenge with a fixed rabies virus strain was studied. The candidate vaccines were also examined by the thermal degradation test. It was found that both vaccines had appropriate antigenic potency and thermostability to be used as a national reference preparation of rabies vaccine.

A gel filtration method to test the efficiency of virucidal disinfectants.

We have described a gel filtration technique for assay of the virucidal potency of disinfectants. It allows a complete separation of disinfectant from the virus after contact, thus preventing chemical cytotoxicity. Very low residual infectious activity can be measured. There is no need for a high viral titer antigen.

Optimization of parameters for detecting antibodies against infectious bronchitis virus using an enzyme-linked immunosorbent assay: temporal response to vaccination and challenge with live virus.

Critical parameters affecting sensitivity and specificity of an enzyme-linked immunosorbent assay (ELISA) for avian infectious bronchitis virus (IBV) were evaluated and optimized. The use of purified IBV as antigen at 50 ng protein/well and high-ionic-strength serum dilution buffer has resulted in a test with minimal nonspecific binding of chicken immunoglobulins and very high sensitivity. Optimum conditions for serum dilution, conjugate dilution, and substrate incubation were determined for minimizing background and nonspecific reactions. The use of this test in a controlled challenge study with chickens vaccinated with live IBV demonstrated its effectiveness in monitoring circulating antibody levels to infectious bronchitis. The IBV ELISA, which is rapid, inexpensive, highly sensitive, and capable of handling very large numbers of samples, should provide the poultry industry with a reliable means for IBV flock monitoring.

Purification, concentration and evaluation of rabies virus antigen.

A number of concentration and purification procedures for rabies virus antigen have been developed during the last decades but only ultrafiltration and density gradient centrifugation have been found suitable for large scale production. The antibody binding test developed by Arko, Wiktor and Sikes was modified and was found useful for evaluation of inactivated antigen-concentrates. This test was used as an 'in process' control. Three examples of practical experience are reported and discussed.

Enzyme-linked immunosorbent assay for the detection of antibodies to infectious bronchitis virus.

An enzyme-linked immunosorbent assay (ELISA) for antibodies to avian infectious bronchitis (IB) virus is described. The immune response of chickens following vaccination with IB virus was monitored using this test, and the titers were compared with those obtained by serum neutralization. The ELISA appears to be suitable for IB serology.

Quantification, characterisation and safety testing of foot-and-mouth disease virus antigens eluted from alhydrogel vaccines.

Different methods for the elution and the concentration of FMDV-antigen from formaldehyde-inactivated alhydrogel vaccines were compared. With locally produced vaccines the best results were obtained if the antigen was eluted with potassium phosphate buffer and the concentration was performed by ultrafiltration. Final recoveries of 50% of the 140-S antigen could be obtained. For innocuity control 1-3 mg of 140-S antigen was eluted from 21 vaccine. SDS-polyacrylamide gel electrophoresis and iso-electric focusing patterns of eluted antigen will be discussed.

Detection and quantification of type C viral proteins in tissues and sera with an enzyme immunoassay.

The detection and quantification of retroviral proteins in cells, tumors, and sera by an enzyme immunoassay technique (enzyme-linked immunosorbent assay [ELISA]) is described. The ELISA technique has been applied to three viral systems: murine leukemia virus, baboon endogenous virus, and simian sarcoma virus. By detecting 0.1 nf of retroviral antigen, the sensitivity of the ELISA is comparable to that of the competition radioimmunoassay technique.

Inactivated-concentrated virus antigen for indirect complement fixation test of foot-and-mouth disease.

To the culture fluids of BHK-21 cells infected with each of types O, A, and Asia 1 of foot-and-mouth disease virus was added acetylethyleneimine to 0.05% (v/v). The mixtures were incubated at 37 degrees C for 24 hours. To them were then added polyethylene glycol 6000 to 10% (w/v), and the mixtures concentrated to one-tenth of the initial volume. The resulting inactivated-concentrated virus antigens showed a complement fixation (CF) titer ranging from 12 to 24. The recovery rate of CF activity was 40 approximately 60%. This activity of each antigen was maintained at 4 degrees C or -70 degrees C for 6 months at least. Experimentally infected cattle were examined for the development of antibody by the aid of the indirect complement fixation (ICF) test with those antigens. As a result, ICF antibody began to be detected 3 approximately 5 days after inoculation. Its titer reached a maximum 10 approximately 14 days after inoculation and decreased gradually thereafter. It was detected even 232 days after inoculation. There was a tendency for the development of ICF antibody to be parallel with that of neutralizing antibody. It was suggested that ICF antibody might be type-specific. In conclusion, the antigens prepared had such high activity that they could be used for the determination of antibody by ICF. In addition, they were of great practical value because of their sufficient keeping quality and safety.