Establishment Of Anti-VSG Or Anti-VAT Antibody Banks And Their Efficacy Against Trypanosoma Evansi Infection In SD Rats

A multiclonal egg yolk anti-VSG antibody bank and a rabbit serum anti-VSG antibody bank against VSG of 20 Trypanosoma evansi VATs and a rabbit serum anti-VATs antibody bank were established to test their efficacy against Trypanosoma evansi infection in SD rats. Ten clone-derived populations were isolated from each, inoculated with 107 Trypanosoma evansi stock YN, of 5 New Zealand White rabbits at 3-day intervals. Twenty VATs were determined from the 50 populations with the indirect fluorescent antibody staining technique and ABC-enzyme-linked assay and designated as BeTat 1.1. BeTat 1.2...BeTat 1.20. VSG of the 20 VATs, propagated in rats, was purified by DE-52 chromatograpHy. Through SDS-PAGE analysis, the molecular weight of the purified VSG was found to be 41.9KD. Hens or rabbits were immunized with 0.5mg VSG combined with Freund's complete adjuvant in priming and Freund's incomplete adjuvant in boosting. An egg yolk antibody bank and an antiserum antibody bank were established by combining antibodies isolated from egg yolk of 20 chickens by the PEG 6000 method or by combining 20 rabbits' antiserum. Five rabbits were used to collect 50 sera and the anti-VAT antibody bank were established by the mixture of 50 sera collected as the followings: the first ten sera collected, at 3-day intervals except the first collected on 6 day postinoculation, from one rabbit inoculated with 107 parasites; the left four 10 sera were collected at the same intervals from four rabbits inoculated with 010, 020, 030, 040 clone-derived populations respectively.Efficacy of the egg yolk antibody bank: Fifteen SD rats were assigned to 5 groups of 3 (challenged and treated with the antibody bank, challenged and treated with specific antibodies against BeTat 1.19, challenged and treated with normal yolk, challenged control, nonchallenged control). Results showed that the antibody bank could greatly reduce the number of trypanosomes in blood for one, two or three days but could not protect the rats from death. Efficacy of the rabbit serum antibody banks: Eighteen SD rats were assigned to 6 groups of 3 (challenged and treated with the anti-VSG antibody bank, challenged and treated with antibodies against BeTat 1.19, challenged and treated with normal rabbit serum, challenged and treated with the anti-VAT antibody bank, challenged control, nonchallengedcontrol). Results showed that the anti-VAT antibody bank could reduce the number of trypanosomes in blood to a undetected state for at least 8 days (because the 3rats died of operational accident), while the anti-VSG-antibody bank and BeTat 1.19 specific antibodies had no effect on the number of the parasites in blood.