[Preservation for vaccinal strains of Leptospira at liquid nitrogen].

INTRODUCTION

Leptospira interrogans strains of Cuban vaccine vax-SPIRAL are preserved in Fletcher's semi-solid medium, which guarantees the preservation of the cell viability for a few months.

OBJECTIVE

to evaluate the cryopreservation at liquid nitrogen of 6 different cryoprotectors as a long-term preservation method for Leptospira interrogans strains used as antigens in vaccine vax-SPIRAL against leptospirosis.

METHODS

viability was systematically evaluated according to the cell yield of the recently thawed strains in EMJH medium. Virulence stability was estimated in hamsters and antigenicity was evaluated by microscopic agglutination test using reference antisera from vaccinal serogroups.

RESULTS

the use of 2.5% and 5% dimethyl sulfoxide, and 2.5% glycerol allowed quick recovery of the three strains without virulence or antigenicity depletion after 19 months of cryopreservation.

CONCLUSIONS

the results showed the feasibility of the cryopreservation at liquid nitrogen using suitable cryoprotectant as a preservation method for vaccinal strains of Leptospira.