Non-specific stimulation induced by clostridiosis vaccine in anti-rabies antibodies titers in vaccinated mice

Abstract

In previous studies an unexpected increase in anti-rabies titers in vaccinated calves and also in not vaccinated calves that were born from previously vaccinated dams was observed. This increase occurred one month after clostridiosis vaccination and persisted until the 12th month of age, suggesting that this vaccine had stimulated the specific immunity against rabies. When the experiment was performed with not vaccinated dams and calves, no increase in anti rabies antibodies titers was observed suggesting that clostridiosis vaccine was able to increase the levels of anti-rabies antibodies only in animals that were previously primed with the rabies vaccine or that were actively vaccinated. In this context, the aim of the present study was to confirm, in another animal model, the effect of clostridiosis vaccine as a non specific stimulus for anti rabies antibodies titers. Forty eight swiss mice, female, 60 days-old divided into six groups of eight animals each were used. The group A was not vaccinated, group B and C was vaccinated with anti rabies and clostridiosis vaccine, respectively, on day 0 and sacrificed at day 15; group D and E was vaccinated with anti rabies and clostridiosis vaccine, respectively, on day 0 and sacrificed at day 30 and group F was vaccinated with clostridiosis vaccine on day 0 followed by antirabies vaccine on day 15 and sacrificed on day 30. It was used a commercial cell culture anti-rabies vaccine and a polyvalent clostridiosis vaccine, both in a dose of 0.04 mL by intramuscular route. Animals were sacrificed according ethical committee guidelines and blood samples were collected. Serum samples were obtained, stored at -20^oC and anti-rabies antibodies titers were evaluated using RIFFT modified test. Animals not vaccinated or vaccinated against clostridiosis didn´t present protective levels of anti rabies antibodies. Mice vaccinated against rabies presented protective levels of antirabies antibodies titers at day 15 that increased on day 30. Titer of antirabies antibodies 15 days after antirabies vaccine was significantly higher in animals that received clostridiosis vaccine before, compared to the group only vaccinated against rabies and evaluated 15 days after vaccination. These results agree with previous reports and reinforce a non specific stimulation induced by clostridiosis vaccine. More studies are needed concerning the clostridiosis vaccine components responsible for the non specific stimulation and the interference of this in serological tests in practice.