Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/18/2003
Publication Date: N/A
Citation: N/A Interpretive Summary:
Technical Abstract: We have completed the genome sequencing of Mycobacterium avium subspecies paratuberculosis (M. paratb), the causative agent of Johne's Disease in dairy cattle and other ruminant species. Analysis of the M. paratb genome found that its sequence contains nearly 4.5 million base pairs that are represented on a large circular chromosome with more than 4,000 predicted genes. This bacterium long been considered as one of the most important threats to the health of dairy cattle worldwide. Despite the recognition of this important disease in dairy cattle, methods for the satisfactory diagnosis, treatment and prevention of the organism are still lacking. With the availability of a genome sequence, new strategies to detect infected animals can now be explored. The development of antigen based diagnostic tests requires that species-specific antigens be identified. However, for M. paratb, no such antigens have been described. This is due, at least in part, to the high genomic similarity between M. paratb and M. avium subsp. avium (M. avium). Despite this high similarity, we have identified at least 21 predicted coding sequences that are present only in M. paratb. Nucleotide sequences representing each of these unique predicted coding regions were amplified and cloned into an E. coli expression vector. Ninety percent of expressed mycobacterial proteins were successfully purified under denaturing conditions. Purified recombinant M. paratuberculosis proteins were used in immunoblotting studies with sera from rabbits and mice immunized with whole cell preparations of M. paratb. Only five of the 21 gene products were detected by all sera tested. Immunoblot analysis with sera from naturally infected and control cattle shows that these same M. paratb proteins are recognized in the context of infection. Collectively, these studies have used a comparative genomic approach to rapidly identify novel M. paratb antigens that are not present in any other mycobacteria.