Paramunität und Paramunisierung

[Application of paramunity inducers in small animal practice]

Paramunity inducers have been used to treat small animals for decades. Paramunity inducers are based on attenuated and inactivated poxviruses (avipox virus and parapox virus). Their applications include both therapeutic and prophylactic use in various diseases. Despite their wide and variable use, only a very small number of placebo-controlled studies has been published. Positive effects in preventing kitten mortality and in treating feline stomatitis have been reported, however, no statistically significant effect of their therapeutic use in canine parvovirus infection, feline leukemia infection virus infection or canine papillomavirus infection could be demonstrated. For these infectious diseases, paramunity inducers do not appear to be effective.

Role of a distinct population of bovine gamma delta T cells in the immune response to viral agents

A distinct population of bovine gamma delta T cells was isolated from peripheral blood mononuclear cells of foot-and-mouth disease (FMD)-vaccinated cattle; these lymphocytes were shown to exert a natural killer-like activity against cells infected by different viruses. The antiviral activity was dependent upon cognate recognition of target cells and could operate by both cytostatic and cytotoxic mechanisms. Among these, secretion of a serine esterase was shown after binding to target cells. This population of bovine gamma delta T cells is recognized by murine monoclonal antibodies 1E7, 5D4, and 6F9, raised in our laboratory. To define an in vivo antiviral role, four heifers were infected with a strain of bovid herpesvirus 1 by the intranasal/intravaginal routes and contact exposure. The prevalence of 1E7+/5D4+ cells among peripheral blood lymphocytes increased dramatically in the first days after infection; the same held true for in-contact cattle, albeit with a different time kinetics. In another experiment, colonization of mucosae was demonstrated by immunoperoxidase staining on tongue and palate sections of healthy cattle. The infiltration of gamma delta T cells altogether in the palate mucosa was much more accentuated in foot-and-mouth disease-vaccinated, as compared to nonvaccinated, control calves.

Comparative evaluation of specific vaccines and immuno-modulators in disease control of beef cattle

Two field trials were undertaken to evaluate specific vaccines and Biological Response Modifiers (B.R.M.) with regard to disease control of beef cattle. Clinical data and laboratory results strongly suggested a genetically determined resistance to transportation stress of some cattle breeds, with possible important consequences on the occurrence of multi-factor diseases. Plenty of calves showed detectable levels of serum interferon and a remarkable activation of at least some lymphocyte populations in the first days after arrival. In general, B.R.M.-treated cattle could better react against environmental pathogens, as evidenced by both clinical and laboratory findings. Several data emerged that even the efficacy of specific vaccines could be largely accounted for by a positive modulation of non-specific immunity; this latter feature can be mainly referred to adjuvants and/or some bacterial antigens.

Characterization of some parameters of non-specific immunity in beef cattle (II)

Serum protein, immunoglobulins, complement, lysozyme, serum bactericidal activity and blast transformation of peripheral blood lymphocytes were tested in beef cattle in different herds and age groups. These parameters were evaluated in their time-kinetics, in comparison with age-matched groups of dairy cattle. Like dairy calves, beef calves up to 4 months of age were shown to have low levels of serum bactericidal activity and haemolytic complement; besides, a worse profile was detected in serum protein and gamma 2 globulin levels. Al(OH)3 and oil-adjuvanted vaccines had a favourable influence on immunoglobulin and lysozyme synthesis. An acute stressing event like transportation was shown to decrease mitogen-driven lymphocyte stimulation for at least 10 days after arrival.

Efficacy of an immunomodulating drug in immunodeficient and immunocompetent mice

Bacillus subtilis culture filtrate (BSKR) was examined for its immunomodulating ability in the immunodeficient beige mouse and the immunocompetent Han:NMRI mouse strain. Following various application schemes the mice were challenged either subcutaneously with Escherichia coli or intranasally with Streptococcus pneumoniae. The mortality rates and the median of survival time were determined. Following subcutaneous application of BSKR Han:NMRI mice challenged with E. coli showed a decrease in mortality regardless of the application scheme. Using the beige mouse a protective effect was observed only after single applications of relatively low doses. Using Sc. pneumoniae as the challenge organism, a subcutaneous application of BSKR caused a decrease in mortality only if it was given on the day prior to infection. In both infection models the intranasal application of BSKR and/or of saline proved to be beneficial by either significantly decreasing the mortality or considerably increasing the survival time of beige and Han:NMRI mice.