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Infect. Immun., 12 1996, 5066-5074, Vol 64, No. 12
JP Dalton, S McGonigle, TP Rolph and SJ Andrews
Two cathepsin L proteinases, cathepsin L1 and cathepsin L2, secreted by
liver flukes may be involved in tissue penetration, nutrition, and
protection from immune attack. To ascertain the immunoprophylactic
potential of these proteinases, and of another molecule, liver fluke
hemoglobin (Hb), we performed vaccine trials in cattle. In the first
vaccine trial various doses of cathepsin L1 were tested. The mean
protection level obtained was 53.7%. In a second vaccine trial cathepsin L1
and Hb elicited 42.5 and 43.8% protection levels, respectively, while a
combination of the two molecules induced a significantly higher level of
protection (51.9%). Cathepsin L2 was not examined alone; however,
vaccination of cattle with a combination of cathepsin L2 and Hb elicited
the highest level of protection (72.4%). The animals that received
cathepsin L1-Hb or cathepsin L2-Hb showed reduced liver damage as assessed
by serum glutamic dehydrogenase and gamma-glutamyl transferase levels.
Furthermore, a reduced viability was observed for fluke eggs recovered from
all vaccine groups. This anti- embryonation effect of vaccination was
particularly evident in the group that received cathepsin L2-Hb where
>98% of the eggs recovered did not embryonate to miracidia. Although all
vaccine preparations induced high antibody titers which were boosted
following the challenge infection, there was no correlation between
antibody titers and protection. The results of these trials demonstrate
that cathepsin Ls and Hb could form the basis of a molecular vaccine that
would not only reduce parasite burden but would also prevent transmission
of liver fluke disease.
Copyright © 1996, American Society for Microbiology
Induction of protective immunity in cattle against infection with Fasciola hepatica by vaccination with cathepsin L proteinases and with hemoglobin
School of Biological Sciences, Dublin City University, Republic of Ireland. johnD@ccmail.dcu.ie
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