Age influence on the immunogenicity of calves to a multivalent vaccine with modified live BRSV

Abstract

The bovine respiratory syncytial virus (BRSV) can cause severe respiratory disease in calves and it is also involved in bovine respiratory disease complex. Vaccination with modified live BRSV is one of the strategies used for the prevention of disease. However, due to the immature immune system of calves, the response of these animals to this type of vaccine in early life is not well understood. The objective of this work is to contribute to the clarification of the importance of age to the immune response of the respiratory system of calves. 12 calves will be used, included in this study shortly after birth. These will be divided into three groups of four animals each, and the control group 1 (G1), whose animals are not immunized and group 2 (G2) and 3 (G3) will consist of animals that will receive the vaccine. The experiment will be carried out in a total of five times (M1-M5), which will be held in the harvest of blood and bronchoalveolar lavage (BAL). G1 samples will be obtained in the five moments. Calves G2 will receive intranasally 1 mL of vaccine containing modified live BRSV in M1 and M2, when they are two and four weeks of age respectively, whereas the same will happen with the calves of G3, but in M3 and M4, while they are with six and eight weeks old. The samples of blood serum and BAL will serve for determining the presence of specific immunoglobulins (IgG, IgG1 and IgM) and total IgA, through the use of commercial ELISA kits. Will be held the virus neutralization test at all times collection. Of all the variables will occur if the data show that parametric distribution and present parametric distribution will initially be evaluated by F test (analysis of variance). When significant, the averages will be compared by the Tukey test. When data present non-parametric distribution, the variables will be analyzed by nonparametric tests of Mann-Whitney and Kruskal-Wallis.