Isolation of antigenic variants of leptospiras from puppies and pigs experimentally infected with Leptospira interrogans serovars canicola and pomona

Chromosomal rearrangement and serovar conversion in Leptospira biflexa strains

A bacterial population change involving chromosomal rearrangement and phenotypic changes in antigens, proteins and lipopolysaccharides is described for strains of Leptospira biflexa that were previously grown in media containing homologous oligoclonal antibodies. The chromosomal rearrangement phenomenon showed that the variants differed from the parent strains, yet they were similar to phenotypically related serovars already occurring in nature. Accordingly, in vitro serovar conversion mediated by chromosomal rearrangement, due to as yet unknown genetic mechanisms, had occurred.

Decreased lipopolysaccharide content and enhanced susceptibility of leptospiras to serum leptospiricidal action and phagocytosis after treatment with diphenylamine

Growth of leptospiras in the presence of diphenylamine (DPA) caused a decrease in the content of leptospiral lipopolysaccharide (LPS). In association with this decrease of LPS, leptospiras became susceptible to anti-leptospiral action of normal rabbit serum (NRS), leptospiricidal action of antibody and complement, and killing by phagocytes. DPA-treated leptospiras were eliminated rapidly from the blood of infected mice and could not grow in the animals.

Leptospiral attachment to cultured cells

Each virulent strain of copenhageni, canicola and pomona of Leptospira interrogans attached effectively to MDCK cells and primary dog kidney cells, while the avirulent or less virulent line of the same strain and avirulent strains belonging to the same serovars and the avirulent reference strains of other serovars did not. Inhibition of the attachment of the virulent copenhageni to MDCK cells was found in the presence of the homologous immunoglobulin G Fab fragment. Strains of L. biflexa attached to the animal cells, but they differed from those of virulent L. interrogans in their capability to attach to glass.

Restriction endonuclease DNA analysis of Leptospira interrogans serovars icterohaemorrhagiae and hebdomadis

Antigenic variants of Leptospira interrogans serovars copenhageni and hebdomadis were examined by bacterial restriction endonuclease DNA analysis with EcoRI, XhoI, SalI, BstEII, and HindIII as the digesting enzymes. The antigenic variants were stable cloned strains which had been cultivated in media containing homologous immune serum. One of the strains examined has been reported elsewhere (R. Yanagawa and J. Takashima, Infect. Immun. 10:1439-1442) as having an antigenic makeup which more closely resembles serovar kremastos than the serovar hebdomadis parent. The closely antigenically related but naturally occurring serovars icterhaemorrhagiae strain RGA and copenhageni strain M20 were examined in parallel. No differences could be shown between the hebdomadis parent and any of its mutants. Serovars copenhageni and icterohaemorrhagiae produced patterns which differed in the high-molecular-weight bands only. The Shibaura parent strain did not differ from copenhageni M20, but the Shibaura M1 strain differed from the other mutants and from icterohaemorrhagiae RGA in its high-molecular-weight bands.