Chaperome screening leads to identification of Grp94/Gp96 and FKBP4/52 as modulators of the α-synuclein-elicited immune response

We have investigated the potential role of molecular chaperones as modulators of the immune response by using alpha-synuclein (alpha Syn) as an aggregation-prone model protein. We first performed an in vitro immunoscreening with 21 preselected candidate chaperones and selected 2 from this set as displaying immunological activity with differential profiles, Grp94/Gp96 and FKBP4/52. We then immunized mice with both chaperone/alpha-synuclein combinations using monomeric or oligomeric alpha-synuclein (M alpha Syn or O alpha Syn, respectively), and we characterized the immune response generated in each case. We found that Grp94 promoted aSyn-specific T-helper (T-h) 1/T(h)17 and IgG1 antibody responses (up to a 3-fold increase) with MaSyn and O alpha Syn, respectively, coupled to a T(h)2-type general phenotype (generating 2.5-fold higher IgG1/IgG2 levels). In addition, we observed that FKBP4 favored a Th1-skewed phenotype with MaSyn but strongly supported a T(h)2-type phenotype with OaSyn (with a 3-fold higher IL-10/IFN-gamma serum levels). Importantly, results from adoptive transfer of splenocytes from immunized animals in a Parkinson's disease mousemodel indicates that these effects are robust, stable in time, and physiologically relevant. Taken together, Grp94 and FKBP4 are able to generate differential immuneresponses to a-synuclein-based immunizations, depending both on the nature of the chaperone and on the aggregation state of a-synuclein. Our work reveals that several chaperones are potential modulators of the immune response and suggests that different chaperones could be exploited to redirect the amyloid-elicited immunity both for basic studies of the immunological processes associated with neurodegeneration and for immunotherapy of pathologies associated with protein misfolding and aggregation.