Detection by radioimmunoassay of antibodies in human smallpox patients and vaccinees

Abstract

A radioimmunoassay procedure was developed for determining smallpox and vaccinia antibodies in human sera. The test detected and measured both primary and secondary immune responses in persons infected with variola virus or vaccinia virus. The antibody titers obtained by complement fixation, hemagglutination inhibition, plaque reduction neutralization, and radioimmunoassay methods were compared. In sequential serum specimens, the radioimmunoassay test indicated fourfold or greater increases in all of the smallpox patients and in six of eight vaccinated persons. Both the complement fixation and the hemagglutination inhibition tests were less effective. In persons who had been vaccinated, radioimmunoassay and plaque reduction neutralization tests appeared to measure the same immune response. However, in smallpox patients the immune response was readily detected by radioimmunoassay, whereas an immune response was not detected by the plaque reduction neutralization test when vaccinia virus was the antigen in the test system. Radioimmunoassay is an operationally simple procedure which provides objective and quantitative end-point titers in serological determinations.

Outbreak of Human Monkeypox, Democratic Republic of Congo, 1996 to 1997

“…Because monkeypox is the only known indigenous orthopoxvirus of Africa that infects humans systemically, seropositive cases showing genus-specific antibodies can be reasonably interpreted as cases that had a monkeypox virus infection (20). Of 72 retrospectively identified cases tested, 54% had antibodies by plaque-reduction assay, a preferred test for verifying orthopoxvirus infections during smallpox eradication (20,21). However, this neutralization test was only 83% sensitive for the detection of vaccinia vaccine-induced antibodies and may have been negative (3) in some patients with monkeypox virus infection during this study interval.…”

“…A higher proportion of sera from retrospectively identified cases (73%) tested positive by the HAI test, which had a higher sensitivity (96%) than the neutralization test for the identification of vaccinia-induced antibodies (22). However, the HAI test may be less specific, and antibody titers detected by it decrease rapidly after infection and would be unlikely to be residual from prior vaccination in the small percentage of patients who had been vaccinated (3,21,23). Finally, 72% of sera from retrospectively identified cases tested positive in a new, nonvalidated Western blot orthopoxvirus antibody test for which sensitivity and specificity have not been determined.…”

Detection by radioimmunoassay and enzyme-linked immunosorbent assay of coronavirus antibodies in bovine serum and lacteal secretions

“…Any attempts to use these assays must take this into consideration. For this reason, these assays were first introduced for use with viruses which grow well in culture (4,5,20).…”

Filter paper solid-phase radioimmunoassay for human rotavirus surface immunoglobulins

“…Radioim-munoassay (RIA) methods may offer an improved alternative method, particularly the solid-phase RIA method, which is simple, economical, speedy, and reproducible. Microtiter plates or plastic tubes have often been used for the solid phase, coated with antisera (5, 11, 13), Echinococcus antigens (10), or cultured cells infected with vaccinia virus (19). The chief difficulty in the solid-phase method is associated with separation of the adsorbed protein during incubation and washing.…”