title: [Preservation for vaccinal strains of Leptospira at liquid nitrogen].
abstract: BACKGROUND
  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.
authors: Instituto Finlay, Centro De Investigación-Producción de Vacunas, Ciudad de La Habana, Cuba. rborrero@finlay.edu.cu
authors: Borrero
authors: B
authors: Maura Reinier
authors: Niurka
authors: N
authors: Batista Santiesteban
authors: Kirenia
authors: K
authors: Blain Torres
authors: Yolanda
authors: Y
authors: Valdés Abreu
mesh_terms: D001428:Bacterial Vaccines; D004355:Drug Stability; D007919:Leptospira / Q000276:immunology*; D009584:Nitrogen; D011309:Preservation, Biological / Q000379:methods*
chemical_list: D001428:Bacterial Vaccines; D009584:Nitrogen