Immunogenic properties of the extracellular domain of Variant Surface Proteins of Giardia lamblia

RUPIL LL; SERRADELL MC; PERALTA DO; MARTINA MA; MARTINO RA; LUJAN HD

cordoba

Congreso; 52 th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; LII Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2016

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The human protozoan parasite Giardia lamblia is covered by a tight coat comprising Variant-specific Surface Proteins (VSPs). Previous results showed that oral immunization with the full repertoire of purified native VSPs, without adjuvants, elicited a protective immune response against challenges with the parasite in gerbils, dogs and cats. To further study the immunogenic properties of VSPs, the extracellular, cysteine-rich domain of three different VSPs from two different Giardia isolates (VSP1267, VSP9B10 and VSPH7) were produced in an insect cell expression system, which has the advantage of producing proteins with correct disulfide bonds, in serum free medium, in absence of pyrogen, and with high purity. To determine if these ΔVSPs are able to activate receptors of the innate immune system we used a reporter cells system. When a broad panel of human TLR genes was used for screening, it was found that ΔVSP1267 was able to signal though TLR2 and TLR4. Furthermore, subsequent studies with mouse receptors demonstrated that this activation was dose-dependent and that it was stronger in mTLR4 than in mTLR2. Similar results were obtained with ΔVSPH7 and ΔVSP9B10. In vitro, these recombinant proteins showed activation of macrophages and dendritic cells, inducing up regulation of co-stimulatory molecules. These results strongly indicate that the immunogenic properties of Giardia VSPs are related to the ability of protein domains rich in CXXC motifs to activate the innate immune system. Since these molecules have also protective activity, VSPs can be used in the formulation of oral vaccines.