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Title: Expansion of the in vitro assay for Leptospira potency testing to other Serovars: Case study with Leptospira hardjo

item Alt, David
item Wilson-Welder, Jennifer

Submitted to: Biologicals
Publication Type: Other
Publication Acceptance Date: 6/17/2013
Publication Date: 9/1/2013
Publication URL:
Citation: Alt, D.P., Wilson-Welder, J.H. 2013. Expansion of the in vitro assay for Leptospira potency testing to other serovars: Case study with Leptospira hardjo. Biologicals. 41(5):323-324.

Interpretive Summary: Evaluation of leptospiral vaccines for potency against Leptospira interrogans serovars Pomona, Icterohaemorrhagiae, Canicola and Grippotyphosa is accomplished using the hamster potency test method described in 9 CFR 113.101-104. The application of this method to evaluation of bacterins developed for immunization against Leptospira interrogans serovar Hardjo or Leptospira borgpetersenii serovar Hardjo is complicated by several issues. Research on vaccine efficacy employing cattle and study of the immune response seen using effective whole-cell bacterins has revealed problems in relating these studies to either hamster-based or other potency testing methods. Future work on serovar Hardjo vaccines using recombinant proteins will require preliminary testing using models in animals other than cattle. These models may also prove applicable to evaluation of potency for protein-based vaccines. Both an acute lethal infection model and a chronic infection model have been developed using two different strains of serovar Hardjo and will be described.

Technical Abstract: The Code for Federal Regulations (9 CFR 113:101-104) specifies how vaccine potency is evaluated in a hamster model for evaluation of leptospiral vaccines against pomona, icterohaemorrhagiae, canicola, and grippotyphosa serotypes of Leptospira interrogans. There are several issues which complicate the use of this in vivo potency test for evaluation of bacterin vaccines in protecting against Leptospira borgetersenii serovar Hardjo or Leptospira interrogans serovar Hardjo. Research data has revealed problems with relating results of hamster potency tests or other potency testing methods to prediction of vaccine efficacy when evaluating whole cell bacterins for protection in cattle. Future development of serovar Hardjo vaccines containing recombinant proteins will require preliminary testing in animal models other than cattle that mimic natural infection. To address the need for new models which mimic natural infection, both acute-lethal and chronic infection models were developed in hamsters using two different strains of serovar Hardjo.