Immune response to other agents of calves persistently infected with bovine virus diarrhoea virus (BVDV).

The ability of calves persistently infected (PI) with bovine virus diarrhoea virus BVDV to respond immunologically to defined antigens other than BVDV was studied. Five clinically healthy PI calves were studied together with 5 non-PI calves serving as controls. The humoral immune response was tested by measuring the serum antitoxin titre following immunization against tetanus. The cellular immune response was tested by the ability to develop a positive reaction in a cutaneous tuberculin test performed 1 month after immunization against Johne's disease (paratuberculosis). Finally, a skin-sensitizing agent, dinitrochlorobenzene (DNCB), was employed to study whether PI calves would react by hypersensitization following skin exposure to DNCB for 7 consecutive days followed by application of DNCB to a new skin area remote from the area that had first been exposed. The response of PI calves to the various types of antigenic stimuli applied was not significantly different from that of the control calves. Thus, PI calves developed a potent antitoxin response after tetanus immunization, they showed a positive reaction to tuberculin skin test after immunization against paratuberculosis, and were skin sensitized with DNCB.