Genome sequence and identification of candidate vaccine antigens from the animal pathogen Dichelobacter nodosus.

Dichelobacter nodosus causes ovine footrot, a disease that leads to severe economic losses in the wool and meat industries. We sequenced its 1.4-Mb genome, the smallest known genome of an anaerobe. It differs markedly from small genomes of intracellular bacteria, retaining greater biosynthetic capabilities and lacking any evidence of extensive ongoing genome reduction. Comparative genomic microarray studies and bioinformatic analysis suggested that, despite its small size, almost 20% of the genome is derived from lateral gene transfer. Most of these regions seem to be associated with virulence. Metabolic reconstruction indicated unsuspected capabilities, including carbohydrate utilization, electron transfer and several aerobic pathways. Global transcriptional profiling and bioinformatic analysis enabled the prediction of virulence factors and cell surface proteins. Screening of these proteins against ovine antisera identified eight immunogenic proteins that are candidate antigens for a cross-protective vaccine.

Identification of novel immunogens in Pasteurella multocida.

UNLABELLED: P. multocida is a Gram-negative pathogen responsible for causing diseases in animals of economic significance to livestock industries throughout the world. Current vaccines include bacterins, which provide only limited protection against homologous serotypes. Therefore there is a need for more effective vaccines to control diseases caused by P. multocida. As a step towards developing vaccines against fowl cholera, a genomics based approach was applied for the identification of novel immunogens. RESULTS: Bioinformatics analysis of the P. multocida genome predicted 129 proteins as secreted, located in the outer membrane, or lipoproteins. 105 of the genes encoding these proteins were cloned and recombinant protein expressed in Escherichia coli. Polyclonal serum from P. multocida-infected chickens reacted with a subset of these proteins. CONCLUSION: These data show the range of bacterial immunogens recognized by the chicken immune system, including 6 novel immunoreactive proteins.