Cellular Immune Response and Abomasum worm burden in Goats Vaccinated with HC58cDNA Vaccine against H. contortus Infection

Abstract

Vaccination with DNA vaccines derived from adult H. contortus induces significant level of protection against homologous infection in goat. To date however, mechanism of protection is not well understood, especially in goat. In this study, HC58 DNA vaccinated goats were artificially infected with 5, 000 dose of infective H. contortus L₃ (third larval stage), and cellular immune responses and abomasum worm burden examined. The results showed that peripheral CD4⁺, CD8⁺ T and B lymphocytes for nematode challenged Groups 1, 2 and 4 increased subsequent to L₃ infection compared to negative control Group 3. Likewise, the mean eosinophil and lymphocyte counts increased substantially after vaccination and L₃ challenge. On the contrary, circulating neutrophil and white blood cells reduced under similar experimental conditions in goats carrying an equal L₃ nematode burden. These findings suggested that regulation of H. contortus expulsion in goat is a complex mechanism orchestrated by CD4⁺ and CD8⁺T cells, recruitment of eosinophil and lymphocytes and inclined towards development of Th₂ responses.

Keywords: Haemonchus contortus; goat; HC58DNA vaccine; cellular immune responses.