Antibody responses in spiral colon, ileum, and jejunum of bovine coronavirus-infected neonatal calves

The use of bovine serum protein as an oral support therapy following coronavirus challenge in calves

The objective of this experiment was to investigate the therapeutic efficacy of a supplemental bovine serum protein blend fed to calves challenged with virulent coronavirus. Twelve Holstein bull calves (approximately 3 wk of age) were allocated by initial body weight to Control (n = 5) and treated (n = 7) groups. On d 0, all calves were orally challenged with 1 x 10(7) plaque-forming units of virulent coronavirus isolate. Infection was allowed to progress for 24 h before treatment was started. On d 1, treated calves began receiving 160 g of dry bovine serum powder (16 g IgG) mixed into milk replacer powder (67 g) at both an a.m. and p.m. feeding. Control calves received only milk replacer powder (227 g) at both feedings. Response to coronavirus challenge and dietary treatment was monitored prior to a.m. and p.m. feeding by the collection of multiple clinical measures. Fecal consistency was decreased by coronavirus challenge but was not affected by dietary treatment. Mean daily rectal temperature and heart rate were not affected by dietary treatment. Average packed cell volume was higher in treated calves than in control (35.0 and 27.0%). Coronavirus challenge resulted in an immediate increase in respiration rate, decreasing by d 7. Control calves tended to have a greater average respiration rate compared with treated (28.7 vs. 26.8 breaths/min). Treated calves had a higher average feed intake than control (0.57 vs. 0.44 kg/d). These data suggest that bovine-serum supplemented milk replacer may decrease the severity of disease in young calves exposed to coronavirus.

The effect of immunosuppression on protective immunity of turkey poults against infection with turkey coronavirus

The objective of the present study was to evaluate the protective effect of humoral and cellular immunities on turkeys infected with turkey coronavirus (TCV). Two trials were conducted with two separate hatches of turkey poults. Turkey's were experimentally immunosuppressed with cyclosporin A (CsA) or cyclophosphamide (CY) and infected with TCV. Prior to infection, treatment with CsA selectively suppressed T cell activity as revealed by 2-3 fold decreased (p < 0.1) lymphocyte proliferation responses to a T cell mitogen, concanavalin A (Con A). Treatment with CY mainly induced B cell deficiency as indicated by significant reductions (p < 0.05) in antibody responses to sheep erythrocytes 7 days after injection. Body weight gain of turkeys treated with CY was significantly lower (p < 0.05) than that of untreated turkeys at 9 days post-infection (PI). Turkeys treated with CY had 1-2 fold higher immunofluorescent antibody assay (IFA) scores for TCV antigens (p < 0.05) in the intestine than untreated turkeys at 9 or 14 days PI. These results suggested that humoral immunity against TCV infection may be important in turkeys.

Infectious bovine rhinotracheitis, parainfluenza-3, and respiratory coronavirus

A number of viruses have been proven to be primary respiratory pathogens of cattle. Viruses may play an important role in making cattle susceptible to secondary respiratory bacterial pathogens. Epidemiology, pathogenesis, laboratory diagnosis, and important properties in infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI-3), and bovine respiratory coronavirus (BRCV) are described in this article.

Cellular immune status of coronavirus-infected neonatal calves

A preliminary study was conducted to determine the cellular immune status of neonatal, colostrum-deprived calves following inoculation with either attenuated or virulent bovine coronavirus (BCV). Uninfected calves served as controls. To determine the intestinal and systemic cellular immune status, we performed MHC-restricted cytotoxic lymphocyte (CTL) assay on mesenteric lymphocytes, enumerated T cell subsets in peripheral blood lymphocytes, and examined histopathological alterations in mesenteric lymph nodes and gut-associated lymphoid tissue. Target cells for the CTL assay were autologous testicular cells and effector cells were mesenteric lymphocytes from calves infected with BCV. No appreciable specific lysis was observed in any group of calves indicating the absence of demonstrable CTL responses. The TC/TS population was severely depressed in the calf inoculated with the virulent virus but not in those inoculated with either the attenuated virus or placebo. The mesenteric lymph nodes and Peyer's patches of calves inoculated with the virulent virus showed severe depletion of lymphocytes. These calves developed intestinal antibody responses in the acute phase of infection (1 week after infection) but were immunosuppressed in the later stage of infection.

Excretion and persistence of bovine coronavirus in neonatal calves

Following oral inoculation, the excretion of a virulent or an attenuated strain of bovine coronavirus in calf feces and their persistence in spiral colon, ileum, and jejunum were studied using hemagglutination and direct fluorescent antibody tests, respectively. The virus was excreted in feces for only 3 days at high titers and then intermittently at low titers. However, viral antigen was detected in crypt or Peyer's patches for at least 3 weeks after infection in 1 of 3 calves given virulent virus and 1 of 2 calves given attenuated virus.