IMMUNOLOGIC STUDIES OF ENTERIC CORONAVIRUS-LIKE PARTICLES(CVLP)

CVLP have been implicated in gastrointestinal illness sporadically among children and in an intensive care nursery outbreak at our hospital. Fecal examination by electron microscopy(EM) is the only means of diagnosis. We developed an enzyme-linked immunosorbent assay(ELISA) using ammonium sulfate precipitated CVLP from feces. The purified CVLP was immunogenic in rabbits. Sera containing antibodies against bovine enteric, canine, OC43, and 229E coronaviruses(CV) did not block binding of rabbit anti-CVLP to microtiter wells coated with purified CVLP. Immune EM using these antisera and nonaggregated CVLP also suggested that CVLP are antigenically distinct from other CV. False positives occurred when stools negative for CVLP by EM were tested. This nonspecific reaction was not blocked by sonicates of E.coli, Strep. fecalis, B.fragilis, or C.difficile, or by C.difficile antitoxin. Absorption of rabbit anti-CVLP serum with suckling mouse intestine did not improve specificity. More sophisticated purification of fecal CVLP is needed to improve ELISA sensitivity and specificity, and to characterize the antigen.