Preparation And Efficacy Of The Rabbit Polyclonal Anti-leptospira Antibody Against Leptospira Infection

Leptospirosis,caused by Leptospira,is one of the most important of neglected emerging zoonotic diseases that has important impacts on public health worldwide.Polyclonal antibody(pcAb)therapy is a potential method to process a series of pathogens for which there are limited determination of treatment,such as leptospirosis.First,antisera were obtained by special immunization,and were detected by microscopic agglutination test.Then pcAb were purified using the caprylic acid ammonium sulfate precipitation method from the antisera,and detected by ELISA,which proved that the pcAb can be able to recognize 56601 and 56606 in vitro.We evaluated the efficacy of pc Ab,derived from the sera of rabbits inoculated with Leptospira,against homotype(Leptospira interrogans serovar Lai)or heterotype(Leptospira interrogans serovar Autumnalis)Leptospira infection in a lethal hamster model.Regardless of whether there was a 56601 infection or a 56606 infection,the pcAb treatment improved survival compared to the controls.The pcAb treatment significantly improved survival in a dose-dependent manner when used to treat 56601 infection in the early treatment.Therefore,a reference dose of pcAb was provided for treating human or other animal leptospirosis.And the pcAb derived from rabbits immunized with 56601 can protect hamsters against 56606 infection,a heterologous serotype leptospirosis,but not completely.This provides the possibility of studying of multi-serotype antibodies.The histopathology's of the infected kidney,liver and lung were also examined by hematoxylin and eosin staining.Using real-time quantitative PCR,we determined that most of the leptospires in the primary organs were almost completely removed by pcAb.In addition,treatments,including antibiotic,pcAb,and combination,were started immediately after occurrence of the first serious sickness mouse in any group.No significant difference in survival rate between pcAb group and antibiotic group was found,but the combination therapy group significantly improved survival rate compared to the others.We conclude that the rabbit pcAb treatment may cure both the homotype and the heterotype lethal Leptospira infections in hamster,and combination therapy improved survival compared to antibiotic group in the late treatment of homotype leptospirosis.