Submitted to: Federation of European Microbiological Societies Microbiology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2005
Publication Date: 6/15/2005
Citation: Zuerner, R.L., Trueba, G. 2005. In vitro selected leptospira interrogans serovar pomona antigenic variants have novel is1501 transpositions. Federation of European Microbiological Societies Microbiology Letters. 248(2005):199-205.
Interpretive Summary: Leptospirosis is a disease in livestock that causes significant economic loss to the industry. Infection with Leptospira causes development of antibodies to a compound found on the surface of these bacteria. This compound, referred to as LPS, is important in diagnostic tests for leptospirosis. Additionally, antibodies to LPS may protect some animals from infection. In this study we examined how leptospira modify the LPS when treated with antibodies. The results show significant changes in the size of LPS made by the bacteria. Coinciding with these changes was a genetic alteration in the mutant strains resulting from movement of a mobile genetic element to new sites. One of these changes is likely responsible for the observed changes in LPS.
Technical Abstract: Leptospira interrogans serovars can be differentiated by unique hybridization patterns using probes to endogenous insertion sequences. These findings led to a hypothesis that transposition or recombination events involving IS elements contribute to changes in antigen expression in Leptospira. To test this hypothesis, two antigenic variants of Leptospira interrogans serovar Pomona were selected in vitro and the distribution of endogenous IS elements determined. Alterations in the size and antigenicity of lipopolysaccharide (LPS) were detected in these mutants as compared to the wild-type parental strain. Hybridization analysis using probes for IS1500 and IS1501 revealed novel transposition events associated with IS1501, but not with IS1500. One IS1501 insertion was common to both variants and was located in a gene of unknown function positioned at the beginning of LPS loci in several L. interrogans serovars. Insertional inactivation of this gene likely affected LPS synthesis. One of the variants had two unique IS1501 insertions, one in a conserved L. interrogans gene, and one occurring in a gene unique to serovar Pomona. This is the first description of antigenic variants in pathogenic Leptospira which defines structural, antigenic, and genetic changes, and first demonstration of transposition of an endogenous IS element in spirochetes.