Evaluation for leptospirosis vaccine. Relation between in vitro growh inibition test and potency test in hamsters / Avaliação de vacinas antileptospirose. Relação entre o teste de inibição de crescimento de leptospiras in vitro e o teste de desafio em hamsters

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

It was investigated the existence in hamsters of correlation between the standard potency test of bacterins antileptospires and the in vitro leptospires growth inhibition test. The assays were performed, in male hamsters, separately according to the commercial (A and B) animal antileptospirosis bacterin used. The quality of the bacterins and the level of neutralizing antibodies were compared, respectively obtained in the challenge test and the in vitro leptospires growth inhibition test (ICL). The potency test with challenge, performed with serovars Pomona and Canicola, was modified from the protocol of The United States Agriculture Department. The immunization schedule employed two 0,25 mL of bacterins, pure and with dilutions, by subcutaneous route with 15-day interval. The challenge was performed after 15 days from the second dose with 0,2 mL of alive cultures from serovars Canicola (bacterins A and B) or Pomona (only bacterin A), the deaths by leptospirosis were registered and on the 21st observation day the survivors were sacrificed and the condition of renal carrier was investigated by culture of renal tissue for leptospires isolation in Fletcher medium. The animals destined to the in vitro leptospire growth inhibition test were sacrificed on the same day the potency assay with challenge was performed on the other group of hamsters. The blood samples were collected aseptically by intracardiac puncture. Once the sterility of each serum was verified the pools were formed with equal amounts of serum per animal and subgroup (n=5). The bacterins potency tests, for both strains, resulted in a higher DL50 for the dilution 10-9 of the challenge inoculum control, the animals were challenged with the dilution 10-6. The number of surviving animals to the challenge and the protection against renal infection varied according to the bacterin used and its concentration. The results of the potency tests with challenge using the bacterins antileptospirosis A and B were within the required standards, being therefore approved according to the international evaluation criteria. The dilution 1:800, for both bacterins tested, which is recommended by international criteria was not capable of protecting against the condition of leptospires renal carrier. Hamsters immunized with the bacterins showed neutralizing antibodies in higher titers in comparison to agglutinating antibodies. The comparison of the performance of the tested bacterins with the sorovars Canicola and/or Pomona, according to its concentration, by the proportions of surviving animals to the challenge assay and the average of the neutralizing antibodies titers, established a neutralizing antibodies titer equal or higher than 1,0log10 corresponding with the bacterins level of approval in the potency assay.

ASSUNTO(S)

hamsters leptospirose animal hamsters in vitro growh inibition test and potency test vacinas animal leptospirosis vaccines teste de inibição de crescimento in vitro teste de potência

ACESSO AO ARTIGO

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