Immune inductor and effector sites in the upper airways of cattle and influence of site of antigen expression on induction of mucosal immunity

Many micro-organisms that cause disease in cattle enter the animal's body by invading the respiratory tract. A number of micro-organisms which invade cattle in this way are a significant threat to animal welfare and cause severe economic loss. Examples include the bacteria, Mycobacterium bovis, which causes bovine tuberculosis, and the virus that causes foot and mouth disease. Although vaccines to a number of such micro-organisms are available, many are only partially effective. This may be partly due to their failure to induce antibodies in respiratory secretions that prevent the micro-organisms from attaching to and colonising the cells lining the respiratory tract or from penetrating and replicating within these cells. There is therefore a clear need to develop more effective vaccines that induce protective immunity in the upper airways of cattle. There is increasing evidence that nasal delivery of vaccines is superior to vaccination at other sites in eliciting protection within the respiratory tract. However, safe and effective nasal vaccines have proved difficult to develop. The purpose of this project is to gain a more detailed understanding of the ways in which the upper airways of cattle respond to infection and mount a protective immune response. This will be achieved by studying in the laboratory the interactions of a live virus that expresses foreign genes and infects the bovine respiratory tract without causing disease, cultures of bovine airway cells and cells of the immune system that have been obtained from different regions of the upper airways of cattle. The findings from these laboratory studies will be compared with immune responses induced after nasal delivery of the viruses to calves. The information generated from this project will aid the design of effective nasal vaccines to protect cattle against a number of important infectious diseases such as foot and mouth disease and bovine tuberculosis. In addition, these studies may lead to the development of laboratory methods for testing new nasal vaccines, thereby reducing the number of animals used in research.

Respiratory mucosal surfaces are the main portal of entry for many pathogens of cattle, a number of which are a significant threat to animal welfare and result in severe economic loss. Examples include Mycobacterium bovis, the causative agent of bovine tuberculosis, and foot and mouth disease virus (FMDV). Pathogens that invade via the respiratory mucosa represent an enormous challenge for the development of vaccines that either prevent the pathogen from attaching to and colonising respiratory mucosa or from penetrating and replicating within respiratory epithelial cells. There is increasing evidence from studies in mice that intranasal vaccination is superior to vaccination at other sites in eliciting protection within the respiratory tract. Intranasal vaccination is, therefore, an attractive strategy for the control of infectious diseases in cattle. However, safe and effective intranasal vaccines have proved difficult to develop. Progress in the development of strategies for induction of protective immunity in the upper airways of cattle are hampered by a lack of detailed knowledge of mucosal immune inductor and effector sites, the role of different antigen-presenting cells in the nasopharynx, the type of vaccine construct most appropriate for stimulating mucosal immunity and the availability of bio-containment facilities needed for the study of some bovine pathogens (M. bovis and FMDV). This project aims to exploit recent advances in the manipulation of the genome of negative-stranded viruses, culture techniques for well-differentiated, bovine airway epithelial cells and the characterisation of bovine dendritic cells (DCs) to: (i) Identify the anatomic location and functional potential of bovine nasopharyngeal immune inductor and effector sites (ii) Identify antigen-presenting cells in bovine upper airway tissues (iii) Determine if targeting foreign antigens to different sites within polarised airway epithelial cells influences the induction of mucosal immunity The project will utilise recombinant bovine respiratory syncytial virus (rBRSV) expressing green fluorescent protein or the E2 protein of bovine virus diarrhoea virus (BVDV) as tools to determine the ability of bovine airway epithelial cells to act as antigen-presenting cells, in vitro; to investigate the effects of virus infection of airway epithelial cells on maturation of DCs; and to characterise DC subsets migrating from tissue explants of bovine nasal-associated lymphoid tissue, tonsils, and respiratory epithelium, following virus infection in vitro. The relevance of the findings obtained from these in vitro studies to the induction of mucosal immunity, in vivo, will be determined by investigating mucosal and systemic immune responses induced following intranasal vaccination of calves with rBRSVs expressing BVDV E2 protein at different sites within polarised airway epithelial cells. The information generated from this project will allow a more targeted approach to the development of intranasal vaccines that will be of broad relevance for a variety of bovine pathogens. In addition, these studies may lead to the development of laboratory methods for evaluating mucosal vaccines, thereby reducing the number of animals used in research.