Detection and assay of avian tumor virus group-specific antigen and antibody by the paired radioiodine-labeled antibody technique

Humoral immune responses of cats to mammalian type-C virus p30s

Natural and experimental cat sera were tested in radioimmune precipitation assays vs purified p30s from FeLV, RD114 and MuLV. Antibodies with specificity for FeLV p30 comparable to hyperimmune sera from heterologous species but of low titer were found in a high percentage of normal cats from households with a high incidence of FeLV and neoplasia. Sera from cats with neoplasms were generally negative. Cats immunized with FeLV gave low-level immune response, also of the same general specificity as heterologous hyperimmune sera. Cat sera do not normally show antibody to RD114 p30 although two immunized weanling cats produced low titered but highly specific p30 antibody. Thus, for both classes of feline type-C virus p30s, there is an evident capability of the cat to mount an immune response to natural or experimental exposure to the respective proteins. The magnitude of the response is between 100 and 1,000 fold below that seen in heterologous species. In contrast, cats immunized with MuLV p30 gave immune responses comparable to those seen in guinea-pigs, rabbits and goats. Several very old cats with carcinoma had antibody which preferentially precipitated MuVL p30. A competition assay using one such serum and labelled MuVL p30 was inhibited by FeVL, RD114, and MuLV p30s. This indicates that the assay is "interspecies" in nature. Among the possible explanations of this reaction category is that it represents antibody to the p30 of an as yet undefined class of feline type-C virus.

Solid phase radioimmunoassay for identification of Herpesvirus hominis types 1 and 2 from clinical materials

A solid phase radioimmunoassay (RIA) was developed for typing Herpesvirus hominis (HVH) strains isolated from clinical materials, and it also proved to be applicable to the direct detection and typing of HVH antigen in human and animal brain tissue. The procedure utilized virus-infected human fetal diploid cells or brain tissue smears in the bottom of 1-dram glass vials, antigen was detected through the use of intermediate HVH antisera produced in rabbits or hamsters and cross-absorbed with the HVH heterotype, and (125)I-labeled anti-species (rabbit or hamster) globulins produced in goats were used for detection of immune complexes. The cross-absorbed HVH antisera could be used at high dilutions in the RIA test, and they reacted with marked type-specificity in the RIA system. Specificity of the test was also improved by determining and using optimal concentrations of intermediate sera and of (125)I-labeled anti-species globulins. Results of typing HVH isolates by the RIA procedure agreed in all instances with those obtained by direct fluorescent antibody staining with cross-absorbed conjugates. The RIA procedure was effective and more sensitive than direct fluorescent antibody for demonstrating and typing HVH antigen directly in smears of infected human brain tissue.

Avian oncornavirus group-specific antigen: detection and quantification by radioimmunoassay

A double-antibody competitive-inhibition radioimmunoassay for avian group-specific antigen is described. A viral protein preparation, consisting primarily of gs-1, was labeled with radioiodine. Hamster and rabbit antisera were reacted with the labeled antigen, and the resultant antibody-antigen complexes were precipitated with the appropriate antiglobulin. Standard curves based on the inhibition of binding of labeled antigen to antibody after preincubation with unlabeled antigen were prepared. These showed the lower limit of sensitivity to be 2 to 10 ng of unlabeled protein when labeled antigen of 2,000 to 5,000 counts per min per ng of specific activity was used in the assay. Extracts of avian oncornavirus-infected cells, likewise, were able to inhibit binding of labeled antigen. This technique will be very useful for the quantification of small amounts of oncornavirus group-specific protein.