Trypanosoma rangeli has a characteristic life cycle in its vector, Rhodnius prolixus, invading the hemolymph and then the salivary glands. Parasite transmission by blood-sucking arthropods relies on their ability to feed on blood. Transmission is then resumed by direct injection of saliva containing parasites or through deposition of contamined feces close to the wound. Salivary gland invasion by protozoan parasites is then a required step for their transmission during feeding. Furthermore saliva imposes several molecular changes on parasite. These changes are induced by salivary gland components on the molecular plasticity of the parasite itself. The ultimate effect of such changes is the acquisition and or improvement of the parasite ability to invade and colonize host cells. Thus saliva-exposed parasites are several times more infective than non-exposed ones. In our lab we are interested in mapping changes imposed by saliva on intracellular signaling pathways. We are currently using Rhodnius prolixus/Trypanosoma rangeli model. Incubation of parasite with extracts of  R. prolixus salivary glands induced changes on its protein phosphorylation profile. In vitro phosphorylation assays showed a major doublet of 55 kDa phosphoproteins where such changes are maximal.  Phosphorylation of these proteins is altered by only 1 hour exposition to saliva followed by endogenous phosphorylation with ³²P-ATP. However,. 12 additional different phosphoproteins were detected by western blotting with anti-phosphoserine antibodies in either control or saliva-treated parasites. A discrete suppression of phosphorylation was observed for most of them. Furthermore in vitro phosphorylation coupled to pharmacological screening with protein kinase inhibitors showed an increase on the phosphorylation of the 55 kDa doublets. This effect was remarkable when the following protein kinases were blocked: casein kinase II, Ca ²⁺-calmodulin kinase and the MEK/ERK pathway. Altogether these results show for the first time that vector saliva is able to modify parasite’s intracellular signaling pathways. The identity of phosphoproteins and the role of their modifications on invasion of host cells we be next investigated with the aid of phosphoproteome tools.