Management of Snakebite and Research Management of Snakebite ...

Management of Snakebite and Research
92
Russell’s Viper (Daboia russelii siamensis) Toxoid:
Variation in Biological Properties of the Toxoid
and Influence of Immunization Schedule on
Antibody Response
Aye-Aye-Myint 1 , Tun-Pe 1 , Nu-Nu-Aung 1 and Maung-Chit 2
1 Venom Research Laboratory, Department of Medical Research, Yangon
2 Yangon Zoological Garden
Abstract
Biological properties of formal-treated Russell’s viper (Daboia russelii siamensis) toxoid
stored at +4 0 C were monitored by the WHO recommended methods at 2, 3, 4, 6,
10 and 12 month following preparation. Formal toxoiding of the venom resulted in
reduction of 15-fold in lethal, 4-fold in coagulant, 22-fold in defibrinogenating,
6-fold in haemorrhagic and 10-fold in necrotic activities. A 44-fold reduction in
capillary permeability increasing activity of the toxoid was observed from four months
onwards. Further two-fold reduction in heamorrhagic and necrotic activities of the
toxoid was observed from six months onwards. Decrease in number of precipitin
bands and protein bands in SDS-PAGE electrophoresis was observed when the toxoid
aged. Such variation in biological properties of stored toxoid will influence the quality
of antibody produced and hence the protective immunity of the immunized subjects.
The influence of immunization schedule of Russell’s viper toxoid on antibody
response in immunized rabbits and monkeys were studied. Rabbits were immunized
subcutaneously with the toxoid at 0, 4 and 8 wks and subsequent boosting was
carried out at 6 wks intervals from 24 to 56 wks and up to 40 wks in monkeys.
Antibody levels peaked at 6-8 wks after the third injection and fell to low level at 24
wks after the first injection. Subsequent boosting at 6 wks intervals from 24 wks
onwards resulted in increase in antibody level reaching peak at 12 wks after the first
booster injection and sustained at its peak throughout the course of immunization.
Antibody response observed in the monkeys was similar to the rabbits, however a
lower level of antibody was observed. Feasibility and cost- effectiveness of boosting
at 6 wks intervals in prophylactic active immunization of farmers at risk with Russell’s
viper toxoid needs to be studied
INTRODUCTION
Monitoring of biological properties of toxoid on storage was not included in the earlier
studies on formal-treated Russell’s viper toxoid (Khan et al., 1980, Aung-Khin et al., 1980).