Molecular cloning and differential IgG responses to a histidine-rich
antigen (OvL3.C1) of Onchocerca volvulus by selected residents
of onchocerciasis endemic regions in Cameroon and Ecuador
In order to further investigate host-parasite interactions in
onchocerciasis, a major Onchocerca volvulus histidine rich
antigen termed OvL3.C1 was isolated from an O. volvulus cDNA library
using antibodies from putatively immune subjects living in
onchocerciasis endemic communities in Cameroon. Analysis of its
sequences predicted the protein to be helix-rich with a single
transmembrane region. Recombinant OvL3.C1 antigen induced from
pBAD-TOPO/Thio vector in Escherichia coli was purified as
inclusion bodies and further by a combination of Ni2+ chelate
chromatography and electro-elution. Anti-OvL3.C1 immunoglobulin G (IgG)
subclass levels were assessed by ELISA in 15 pairs and 18 pairs of
selected and cross-matched infected and putatively immune subjects from
Cameroon and Ecuador, respectively. IgG3 and IgG4 levels were shown to
be significantly higher in putatively immune (immune protected)
subjects. A higher IgG3 level in endemic normal subjects is implicated
in parasite killing and the development of the putative immune status
while IgG4 has been shown to block onchocercal pathology. OvL3.C1 is a
dominant antigen in onchocerciasis which elicits strong responses in
subjects expose to both African and South American forms of
onchocerciasis. It is therefore an important player in mechanisms of
resistance or allergy attenuation in onchocerciasis
