Host immune response evasion strategies in Ornithodoros erraticus and O-moubata and their relationship to the development of an antiargasid vaccine

We analysed in mice why the salivary gland extract (SGE-2) from Ornithodoros erraticus and O. moubata induce a protective response with Freund's adjuvants (FAs) in swine while the saliva, in natural conditions, does not. Such protection has been ascribed to the fact that administration of SGE-2 plus FAs permits the recognition of certain salivary components that under natural conditions are not immunogenic. The present findings confirm this hypothesis since in mice, which are unable to recognize the above components, the SGE-2-FAs do not induce any protection. We rule out the possibility that the cause of this could lie in the absence of prostaglandin E-2 in the SGE-2 (vs saliva) since it is not present in either fluid. Neither could it be due to a change in antibody isotype since those induced by parasites bites and by the SGE-2-FAs are the same (IgG2a>IgG1>IgG2b; not IgG3, IgM, IgE). No IgG2a were seen when the SGE-2 were administered alone or with alum or ricin. It is therefore suggested that first responses would be Th1 and the second ones Th2, although no IgE is seen in the latter responses either. The parasites do not require complement to feed; by contrast, they block its activation and skin cellular infiltrates, such as those elicited by IL-8, MCP-1 and C5a, do not affect them, regardless of the presence or not of antitick antibodies.