Study of homology of mce and invA genes among different serovars of Leptospira interrogans and their in vivo expression

Abstract

Leptospirosis is a worldwide zoonotic disease. Pathogenesis of leptospirosis is not well understood. Identification of virulence factors of pathogenic Leptospira and their roles in pathogenesis is crucial. Based on available whole-genome sequences of Leptospira, two presumptive virulence genes which are homologous to the invasionA (invA) gene of Rickettsia prowazekii and the mammalian cell entry (mce) gene of Mycobacterium tuberculosis, have been identified. The function of these genes may involve in the attachment and invasion of eukaryotic cells. We proposed that these gene homologues should be conserved in pathogenic serovars of Leptospira. Thus, our objective of the study is to determine the presence and the conservation of each gene in various serovars of pathogenic Leptospira. Ten different pathogenic serovars and one non-pathogenic serovar (serovar Patoc) leptospires were used in this study. Polymerase chain reaction using primers designed to bind to the conserved regions of each gene were performed. The amplified PCR products of the invA gene homologue were abtained in seven pathogenic serovars whereas eight pathogenic serovars contained the homologue of mce gene. Neither gene homologue was amplified in the non-pathogenic serovar. The nucleotide sequences of the invA gene homologue of seven serovars were greater than 99% identity. The mce gene homologues of eight serovars were approximately 90 to 100% nucleotide identity resultin in more than 98% amino acid identity. Therefore, the gene homologues of invA and mce are found to be conserved in most pathogenic serovars of Leptospira with high-degree similarity at nucleotide and amino acid levels. These two homologues were absent in non-pathogenic serovar. However, convalescent sera of patients with leptospirosis could not detect recombinant proteins of InvA and Mce. In vivo expression of these genes requires further investigations.