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

Abstract

The sensitivity of a radioimmunoassay (RIA), an enzyme-linked immunosorbent assay (ELISA), and a serum neutralization assay (SN) for detecting antibodies to bovine coronavirus in serum and colostrum were compared. Although there proved to be a good correlation among all three assays (r = 0.915 and 0.964 for RIA with SN and ELISA, respectively), RIA and ELISA proved to be at least 10 times more sensitive than neutralization tests. By using these techniques, it was possible to detect a time-dependent decrease in antibody levels in bovine colostrum after parturition. Using ELISA, we demonstrated that 12 of 12 herds in Saskatchewan, and 109 of 110 animals tested, had antibody to bovine coronavirus. There was no elevated antibody response in serum or lacteal secretions of cows vaccinated once or twice with a commercially available modified live rota-coronavirus vaccine. In addition to being more sensitive than SN, ELISA and RIA proved to have other advantages for measuring antibody levels to bovine coronavirus and therefore warrant wider use as tools in diagnostic virology.

Lactogenic immunity following vaccination of cattle with bovine coronavirus

“…A major decline in speci®c antibody levels present in mammary secretions was observed in the ®rst few days after calving. This is consistent with previously reported research [7,17], which showed that the switch from colostrum to milk was associated with a decrease in immunoglobulin concentration. Enhanced antibody levels are maintained for 21 to 28 days post-calving, although as BCoV speci®c antibody levels decrease calves will become more susceptible to sub-clinical infection.…”

“…This can be achieved by allowing the neonate to ingest colostrum or milk containing these speci®c antibodies from its dam (lactogenic immunity). Although most adult cattle are seropositive for both rotavirus and coronavirus antibodies [7], during the transition from colostrum to milk production there is a dramatic decline in antibody titres which partially explains the high incidence of infection in calves older than 5 days. Successful rotavirus vaccines aimed at increasing both the titre and duration of speci®c antibody in both colostrum and milk have been developed [8], however, similar success has not been reported with vaccines targeted against bovine coronavirus [9±13].…”

Pathophysiology of Diarrhea in Calves

“…The epidemiology and pathophysiology of coronavirus diarrhea in calves overlaps significantly with that caused by rotavirus. Antibodies to coronavirus are ubiquitous in cattle, 146 and the virus is frequently found in both normal and diarrheic feces of calves. 147 Coronavirus typically affects calves with the first 3 weeks of life, and peak incidence occurs between days 7 and 10.…”

Enteric Viral Infections of Calves and Passive Immunity

“…All viruses in Table 3 are endemic. Most adult cattle are seropositive for antibodies to rotavirus (2,17,82) coronavirus (56), and parvovirus (70), and about 60% of cattle have neutralizing antibodies to bovine viral diarrhea virus (BVD) (39). None of the recently described viruses (Bredavirus, RVLA, calicivirus, or as~rovirus) has been passaged serially in cell culture.…”