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Year : 1999
Tome : 150
Volume : 11
Pages : 885-890
Title : Bactericidal Assay and Passive Protection Studies of Leptospira interrogans
Authors : F. S. F. ALVES, R. B.LEFEBVRE and W. PROBERT
Summary : A previous investigation conducted in our laboratory resulted in the isolation of three putative outer surface proteins of 32, 40, and 45 kDa, which were expressed and conserved among six prevalent Leptospira interrogans serovars. In this study, polyclonal antibodies were raised against whole cell and outer surface proteins isolated as detergent phase proteins (DPP) and gel-purified proteins. These antibodies were subsequently used in an in vitro bactericidal assay and in passive immunization studies using cyclophosphamide-treated Balb/c mice. Bactericidal activity against the six serovars was found when anti-pomona whole cell sertun and anti-pomona DPP serum were tested. Monospecifîc antisera to the 32 and 40 kDa antigens had bactericidal activity on avirulent and virulent pomona serovar, but the tirer was lower than that of either DPP or whole cell antiserum. Cyclophosphamide­treated Balb/c mice injected with antibodies, generated against DPP or whole cell pomona, were protected against challenge with 109 cells of serovar pomona strain Pomona. Gel purifîed monospecifîc antisera to the 32 and 40 kDa proteins protected only 67 % of the mice. The efficiency of passive protection, with those antibodies was demonstrated by prevention of multiplication and spread of Leptospira to the kidneys. Protection in cyclophosphamide-treated Balb/c mice was well correlated with bactericidal activity of antiserum in vitro.
Keywords : leptospirosis, bactericidal assay, passive protection, antibody, antigens
Correspondence : F. S. F. ALVES
Adress : EMBRAPA/National Goat Research Center - Caixa Postal D- 10, CEP 62.011- 970, Sobral, CE, Brazil

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