Immunobiological activity of Leishmania cysteine peptidases
A collaborative programme with Professors James Alexander, Robin Plevin,
Graham Coombs , University of Strathclyde, Glasgow and Professors Paul Garside and Jim Brewer, University of Glasgow
Aims:
- To identify the precise effect of Leishmania mexicana CPB cysteine peptidase and inhibitor of cysteine peptidase (ICP) expression on antigen presenting cell phenotype and function and T cell activation and differentiation in vivo.
- To determine how L. mexicana CPB and ICP interplay modulates macrophage signal transduction pathways and compare these effects in dendritic cells.
- To evaluate the vaccine potential of CP-deficient mutants and CPB protein.
Peptidases have been shown to play important roles in the pathogenicity of parasitic protozoa. Leishmania mexicana contains multiple, highly active cysteine peptidases (CPs), many of which are stage-regulated. By generating CP-deficient mutants through targeted gene disruption, we have identified the amastigote-specific, cathepsin-L like CP, CPB, as an important virulence factor. Importantly, we have demonstrated that reduced virulence of the CP-deficient parasites is not a direct result of a loss of fitness but is a consequence of a bias of the immune response towards a Th1 rather than Th2 phenotype, following infection. CPB skewing of the immune response could be a result of CPB inducing IL-4 production, inhibiting a Th1 response, which could be via disrupting cell signalling processes, reducing antigen processing and MHC Class II presentation, or a combination of several of these factors. We have now also identified a Leishmania gene encoding an inhibitor of cysteine peptidases (ICP) that appears to influence host-parasite interactions and modulate the immune response possibly by interaction with CPB, and perhaps other CPs, outside the parasite.
We hypothesise that the actions of leishmanial CPs and ICP collectively contribute to the chronic disease states induced by L. mexicana through modulation of the host’s immune response. Our approach to testing this hypothesis and elucidating the pathobiology of Leishmania will be to utilise the unique set of virulence factor mutants of Leishmania that we have developed (and will further develop) allied with a suite of state of the art immunological tools and techniques including real-time in vivo imaging, using intravital-multiphoton microscopy.
Millington,O.R., Myburgh,E., Mottram,J.C., and Alexander,J. (2010). Imaging of the host/parasite interplay in cutaneous leishmaniasis. Exp. Parasitol. 126, 310-317. PDF
Bryson,K., Besteiro,S., McGachy,H.A., Coombs,G.H., Mottram,J.C., and Alexander,J. (2009). Over-expression of the natural inhibitor of cysteine peptidases, ICP, in Leishmania mexicana leads to reduced virulence and a Th1 response. Infect. Immun. 77, 2971-2978. PDF
Saravia,N.G., Escorcia,B., Osorio,Y., Valderrama,L., Brooks,D., Arteaga,L., Coombs,G., Mottram,J., and Travi,B.L. (2006).Pathogenicity and protective immunogenicity of cysteine proteinase-deficient mutants of Leishmania mexicana in non-murine models. Vaccine 24, 4247-4259. PDFPoot,J., Spreeuwenberg,K., Sanderson,S.J., Schijns,V.E.C.J., Mottram,J.C., Coombs,G.H., and Vermeulen,A.N. (2006).Vaccination with a preparation based on recombinant cysteine peptidases and canine IL-12 does not protect dogs from infection with Leishmania infantum.Vaccine 24, 2460-2468. PDF
Mottram,J.C., Coombs,G.H., and Alexander,J. (2004). Cysteine peptidases as virulence factors of Leishmania. Curr. Opin. Microbiol. 7, 375-381. PDF
Cameron,P., McGachy,A., Anderson,M., Paul,A., Coombs,G.H., Mottram,J.C., Alexander,J., and Plevin,R. (2004). Inhibition of Lipopolysaccharide-induced macrophage IL-12 production by Leishmania mexicana amastigotes: the role of cysteine peptidases and the NF-kB signaling pathway. J. Immunol. 173, 3297-3304. PDF
Denise,H., McNeil,K.S., Brooks,D.R., Alexander,J., Coombs,G.H., and Mottram,J.C. (2003). The expression of multiple CPB cysteine protease genes is required for Leishmania mexicana virulence in vivo. Infect. Immun. 71, 3190-3195. PDF
Pollock,K.G., McNeil,K.S., Mottram,J.C., Lyons,R.E., Brewer,J.M., Coombs,G.H., and Alexander,J. (2003). The Leishmania mexicana cysteine protease, CPB2.8, induces potent Th2 responses. J Immunol. 170, 1746-1753. PDF
Buxbaum,L.U., Denise,H., Coombs,G.H., Alexander,J., Mottram,J.C., and Scott,P. (2003). CPB cysteine proteases of Leishmania mexicana inhibit host TH1 responses and protective immunity. J. Immunol. 171, 3711-3717. PDF