Oorsig/Review
Wirevax: Vaccination
against Haemonchus
contortus in sheep
Dr Hanre Ferreira
Vaccination against helminths is a control
concept that is currently being successfully
applied in the control of Dictyocaulus viviparus
(lungworm) infection in cattle in some parts of
the world. Similar attempts have been made to
develop vaccines against several economically
important gastrointestinal nematodes in small
stock and cattle (Ekoja & Smith 2010; Emery &
Wagland 1991; Halliday & Smith 2011; Miller &
Horohov 2006).
The vaccine strategy that currently promises the
most success largely ignores the mechanisms
of natural immunity and attempts to direct
responses towards external antigens (somatic
antigens) on the outer surface (surface antigens)
and in excretions and secretions (excretory-
secretory antigens, ES antigens) of helminths.
Candidate-protective antigens have so far been
Circulating antibody, detected with a fluorescein conjugate,
in lambs vaccinated with the gut membrane proteins purified
from adult H.contorus binds to the microvillar surface of the
instestinal cells of adult parasites. (Knox et al 2003)
identified on the surface of oncospheres from
Taenia and Echinococcus sp, and excretions and
secretions of Fasciola hepatica, H. contortus and
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Ostertagia ostertagi (Smith & Zarlenga 2006).
In the case of blood-feeding Haemonchus sp,
the luminal surface of the intestine has been
a particularly rich source of suitable target
molecules (Smith & Zarlenga 2006).
In the most promising attempt to develop a
vaccine against H. contortus in small stock, highly
protective intestinal cell-membrane antigens,
namely H-gal-GP and H11, have been identified
and isolated at the Moredun Research Institute
(Emery & Wagland 1991; Knox & Smith 2001;
Smith 2008).
H-gal-GP and H11 in Perspective
Haemonchus galactose-containing glycoprotein
complex (H-gal-GP) binds selectively to lectins
and has a specificity for N- acetylgalactosamine.
In each experiment, immunisation with H-gal-
GP significantly reduced faecal egg counts
(FECs) and wireworm burdens in vaccinated
sheep compared to the unvaccinated controls.
Immunisation was also significantly more
effective against female than against male
worms, as shown by the abnormal sex ratio of
the populations recovered from each vaccinated
group (Smith et al. 1999).
H-gal-GP is an integral membrane complex
of proteases derived from the microvilli of H.
contortus intestinal cells. It is hypothesised
that in vaccinated sheep, H-gal-GP antibodies
ingested with the blood meal interfere with the
worms’ digestion and leads to starvation of the
parasites (Smith 2007).
H11 is an integral membrane glycoprotein
complex expressed exclusively in the intestinal
microvilli of the parasitic stages. It is a highly
effective immunogen against H. contortus
challenge and has resulted in a 90% reduction