Rotavirus is the leading cause of infectious diarrhoea in infants and children throughout the world (Davidson, 1996). In developed countries, rotavirus is associated with significant morbidity, while it causes a high rate of infant mortality in developing countries (Blacklow & Greenberg, 1991).

At present there is no effective treatment or vaccine against human rotavirus. Although considerable effort is being put into developing such a vaccine (Molyneaux, 1995; Midthun & Kapikian, 1996), researchers are encountering difficulty in obtaining sufficiently broad protection against the great variety of human rotavirus serotypes (Kapikian & Chanock, 1985). Passive immunization has been tried as an alternative, and clinical trials have shown that oral intake of bovine colostrum containing anti-human rotavirus antibodies is effective in preventing rotavirus infection and transmission in experimental animals, infants and children (Davidson, 1996). Since cross reactivity has been found between bovine and human rotavirus strains (Kapikian & Chanock, 1985), a product containing specific antibodies against human or bovine rotavirus strains may exert a protective effect in human babies. Such a product would be a useful temporary measure while an effective vaccine is developed. Furthermore, these products could be valuable for immunocompromised patients in preventing rotavirus infections.

However, such products would be subjected to processes such as pasteurization or ultra high temperature treatments, so it would be necessary to know the effect of heat on the biological activity of the antibodies. We have previously studied the effect of heat on the structure of bovine colostrum immunoglobulins IgG, IgA and IgM and evaluated the kinetics of heat denaturation by measuring the loss of their ability to bind to specific antibodies directed against them (Mainer et al. 1997). In the present study we have investigated the effect of different heat treatments on the biological activity of immunoglobulins from bovine colostrum by measuring the virus-neutralizing activity (VNA) of heat-treated colostrum containing anti-rotavirus immunoglobulins against a bovine strain. In addition, we have studied the distribution of the VNA between the different classes of immunoglobulins of the anti-rotavirus colostrum.