The secretory Onchocerca volvulus protein OvS1/Ov20 exhibits the capacity to compete with serum albumin for the host's long-chain fatty acids.

The mechanism by which filarial parasites derive fatty acids bound to the host's carrier protein is poorly understood. The capacity of a secretory protein of Onchocerca volvulus (OvS1/Ov20) to compete with serum albumin for arachidonic and other fatty acids was investigated in this study. Binding affinities of the two proteins for the long-chain fatty acids were determined using displacement assays. The fluorescent probes used included 11-((5-dimethylaminonaphthalene-1-sulfonyl)amino) undecanoic acid (DAUDA) and cis-parinaric acid. OvS1 protein bound arachidonic acid with an affinity five-fold greater than the affinity exhibited by serum albumin. Oleic acid was bound by the parasite protein with an affinity two-fold greater than the affinity shown by serum albumin. Furthermore, the affinities exhibited by OvS1 protein in binding arachidonic and linoleic acid were about two times higher than the affinity for oleic acid. The results suggest that the OvS1 protein has the capacity to compete with the main host's fatty acid carrier protein for the long-chain fatty acids, in particular arachidonic acid, the precursor for eicosanoids.