1a.Objectives (from AD-416):
Objective 1- identify ligands from mycobacteria that bind WC1+ bovine T cells by expressing each of the bovine SRCR domains from CD163 family members (WC1, CD163 molecules) - ligands may be detected in antigen fractions containing secreted products or surface ligands of the bacteria.
Objective 2 - produce transfected cells expressing SRCR domains that have pathogen binding capabilities into mononuclear cells to evaluate affects on in vitro specific immune responses.
Objective 3 - evaluate cells and tissues from M. bovis infected and BCG vaccinated cattle to determine if cells expressing WC1 or CD163 molecules increase in number and responsiveness upon infection/vaccination.
1b.Approach (from AD-416):
Our labs have shown that bovine gamma delta T cells expressing the immune co-receptor WC1 (WC1+ gamma delta T cells) are activated in response to Mycobacterium and Leptospira. WC1 is part of the scavenger receptor family known as CD163 which includes CD163A, CD163b and CD163c-a in humans. The mechanism of activation of gamma delta T cells in all mammalian species including humans via the gamma delta T cell receptor (TCR) and co-receptors remains largely enigmatic. However we have previously shown that the cell surface glycoproteins belonging to the WC1 family of receptors act as activating co-receptors in conjunction with the TCR. The bovine genome contains approximately fourteen WC1 genes and we have shown that two of these WC1 gene products contribute to the bovine gamma delta T cell response to Leptospira; another two have been implicated in the bovine gamma delta T cell response to Anaplasma by others. We hypothesize that specific domains of CD163/WC1 gene products bind various bacteria and their products and once elucidated can be exploited to develop vaccines in both species (humans and cattle).
Bovine tuberculosis is caused by Mycobacterium bovis (M. bovis), a human and animal pathogen that causes a chronic infection in cattle, despite eliciting a robust and specific immune response. Gamma delta T cells are a poorly understood population of lymphocytes in cattle that contribute to the response to M. bovis infection. A significant sub-population of bovine gamma delta T cells express WC1 co-receptors. WC1 molecules are necessary for activation of bovine gamma delta T cells and likely act as pathogen recognition receptors. The objective of this grant is to characterize the gamma delta T cell response to M. bovis infection of cattle and to determine the function of WC1 molecules in this response. Studies conducted this fiscal year have focused on determining the phenotype of gamma delta T cells in the peripheral blood of cattle experimentally infected with M. bovis based upon WC1 expression (i.e., WC1.1 and WC1.2 sub-populations). Further studies are planned to characterize the phenotype of these sub-populations in lung and lymph nodes from Mycobacterium bovis-infected cattle. Deciphering the mechanisms of the gamma delta T cell response to M. bovis infection will provide insights into potential control measures for this animal and human pathogen (e.g., vaccination) and may be translatable to other pathogens (e.g., Leptospira, Brucella) affecting cattle.