Large protein as a potential target for use in rabies diagnostics

Rabies is a zoonotic viral disease that remains a serious threat to public health worldwide. The rabies lyssavirus (RABV) genome encodes five structural proteins, multifunctional and significant for pathogenicity. The large protein (L) presents well-conserved genomic regions, which may be a good alternative to generate informative datasets for development of new methods for rabies diagnosis. This paper describes the development of a technique for the identification of L protein in several RABV strains from different hosts, demonstrating that MS-based proteomics is a potential method for antigen identification and a good alternative for rabies diagnosis.

Proteomic inventory of myocardial proteins from patients with chronic Chagas' cardiomyopathy

Chronic Chagas' disease cardiomyopathy (CCC) is an often fatal outcome of Trypanosoma cruzi infection, with a poorer prognosis than other cardiomyopathies. CCC is refractory to heart failure treatments, and is the major indication of heart transplantation in Latin America. A diffuse myocarditis, plus intense myocardial hypertrophy, damage and fibrosis, in the presence of very few T. cruzi forms, are the histopathological hallmarks of CCC. To gain a better understanding of the pathophysiology of CCC, we analyzed the protein profile in the affected CCC myocardium. Homogenates from left ventricular myocardial samples of end-stage CCC hearts explanted during heart transplantation were subjected to two-dimensional electrophoresis with Coomassie blue staining; protein identification was performed by MALDI-ToF mass spectrometry and peptide mass fingerprinting. The identification of selected proteins was confirmed by immunoblotting. We demonstrated that 246 proteins matched in gels from two CCC patients. They corresponded to 112 distinct proteins. Along with structural/contractile and metabolism proteins, we also identified proteins involved in apoptosis (caspase 8, caspase 2), immune system (T cell receptor ss chain, granzyme A, HLA class I) and stress processes (heat shock proteins, superoxide dismutases, and other oxidative stress proteins). Proteins involved in cell signaling and transcriptional factors were also identified. The identification of caspases and oxidative stress proteins suggests the occurrence of active apoptosis and significant oxidative stress in CCC myocardium. These results generated an inventory of myocardial proteins in CCC that should contribute to the generation of hypothesis-driven experiments designed on the basis of the classes of proteins identified here.

Proteomic inventory of myocardial proteins from patients with chronic Chagas' cardiomyopathy

Chronic Chagas' disease cardiomyopathy (CCC) is an often fatal outcome of Trypanosoma cruzi infection, with a poorer prognosis than other cardiomyopathies. CCC is refractory to heart failure treatments, and is the major indication of heart transplantation in Latin America. A diffuse myocarditis, plus intense myocardial hypertrophy, damage and fibrosis, in the presence of very few T. cruzi forms, are the histopathological hallmarks of CCC. To gain a better understanding of the pathophysiology of CCC, we analyzed the protein profile in the affected CCC myocardium. Homogenates from left ventricular myocardial samples of end-stage CCC hearts explanted during heart transplantation were subjected to two-dimensional electrophoresis with Coomassie blue staining; protein identification was performed by MALDI-ToF mass spectrometry and peptide mass fingerprinting. The identification of selected proteins was confirmed by immunoblotting. We demonstrated that 246 proteins matched in gels from two CCC patients. They corresponded to 112 distinct proteins. Along with structural/contractile and metabolism proteins, we also identified proteins involved in apoptosis (caspase 8, caspase 2), immune system (T cell receptor ss chain, granzyme A, HLA class I) and stress processes (heat shock proteins, superoxide dismutases, and other oxidative stress proteins). Proteins involved in cell signaling and transcriptional factors were also identified. The identification of caspases and oxidative stress proteins suggests the occurrence of active apoptosis and significant oxidative stress in CCC myocardium. These results generated an inventory of myocardial proteins in CCC that should contribute to the generation of hypothesis-driven experiments designed on the basis of the classes of proteins identified here.

Cellular autoreactivity against heat shock protein 60 in renal transplant patients: peripheral and graft-infiltrating responses

Autoreactivity to heat shock protein 60 (Hsp60) has been implicated in the pathogenesis and regulation of chronic inflammation, especially in autoimmune diseases. In transplantation, there is a lack of information regarding the cytokine profile and specificity of cells that recognize self-Hsp60 as well as the kinetics of autoreactivity following transplantation. We studied the cellular reactivity of peripheral and graft-infiltrating lymphocytes against Hsp60 in renal transplant patients. Cytokine production induced by this protein in peripheral blood mononuclear cells indicated a predominance of interleukin (IL)-10 during the late post-transplantation period, mainly in response to intermediate and C-terminal peptides. Patients with chronic rejection presented reactivity to Hsp60 with a higher IL-10/interferon (IFN)-gamma ratio compared to long-term clinically stable patients. Graft-infiltrating T cell lines, cocultured with antigen-presenting cells, preferentially produced IL-10 after Hsp60 stimulation. These results suggest that, besides its proinflammatory activity, autoreactivity to Hsp60 in transplantation may also have a regulatory role.

T-Cell response to self HSP60 peptides in renal transplant recipients: a regulatory role?

T-cell responses to heat shock proteins (Hsp) have been suggested to play a role not only in inflammatory conditions, but also in various human autoimmune diseases and in the allograft response. Previous data from our group suggested that during the early posttransplantation (post-Tx) period (<6 months post-Tx), the anti-Hsp60 T-cell repertoires in renal transplant recipients were predominantly proinflammatory. In the later period, they were predominantly regulatory. In agreement with our results, diversification of the T-cell responses toward the carboxy-terminal determinants of Hsp60, related to the resolution of the inflammatory process, was shown in an experimental model of adjuvant arthritis. It has not been clarified whether this diversification is also present in transplantation. In this context, our objective was to analyze cytokine production against autologous Hsp60 peptides from different regions of the protein, using peripheral blood mononuclear cells of 9 renal transplant recipients at 2 timepoints after transplantation: early (<6 months) and late (>1 year). IFN gamma production induced by Hsp60 peptides was observed in 71% and 75% of the patients in the early and late post-Tx periods, respectively. Interleukin (IL)-10 production induced by Hsp60 peptides was observed in 28% of the patients in the early period and in 62% in the late period. Interestingly, the production of IL-10 was induced mainly by peptides of the intermediate and the C-terminal regions. This suggests a predominance of autoreactive regulatory anti-Hsp T-cell repertoire in the late post-Tx period, which predominantly recognize peptides from the intermediate and C-terminal regions of the protein.

Establishment of an expression cloning system for CD4+ T cell epitopes

We previously reported an epitope presenting vector, pCI, a derivative of a human invariant chain (Ii) expression vector, in which the class II associated invariant chain peptide (CLIP, Ii p89-101) could be substituted with antigenic peptides. In the current study, we used this vector to develop a new expression cloning system to identify CD4+ T cell epitopes. We inserted double-stranded oligo DNAs of randomized sequences into this vector and prepared an epitope-presenting library which loads randomized 13-mer peptides onto HLA class II molecules coexpressed in COS-7 cells. Utilizing this library, we isolated a cross-reactive epitope recognized by a glutamic acid decarboxylase (GAD) 65-autoreactive T cell clone established from a patient with insulin-dependent diabetes mellitus. Although the newly identified epitope (PVQLSNQWHVVGATF) was far different from the original epitope, GAD65 p116-128 (NILLQYVVKSFDR), it did have the capacity to stimulate the T cell clone comparable to that of the original GAD epitope. Our system may be applicable not only for identifying of cross-reactive epitopes for CD4+ T cells of known specificity, but also for detection of epitopes stimulatory for CD4+ T cells the epitopes of which are unknown.

Retro-inverso peptide analogues of Trypanosoma cruzi B13 protein epitopes fail to be recognized by human sera and peripheral blood mononuclear cells

Retro inverso (RI) analogues of antigenic synthetic peptides, which are made of D-amino acids with a reversed sequence, may mimic the side chain conformation of natural all-L peptides. RI analogues were cross-reactively recognized by antibodies and CD4+ T cells reactive against natural all-L synthetic peptides or native proteins in animal models. Since peptides containing D-amino acids are highly resistant to proteolytic digestion, cross-reactive RI analogues may be ideal for in vivo administration to humans as synthetic peptide vaccines or immunomodulators. B13 is an immunodominant tandemly repetitive protein from Trypanosoma cruzi, a protozoan parasite that is the causative antigen of Chagas' disease. In order to test whether RI peptides can be recognized by human antibody and T cells, we synthesized two all-L peptides containing the immunodominant B (S12) and T (S15.7) cell epitopes of B13 protein from T. cruzi and their retro (R, made of all-L amino acids with reversed sequence), inverso (I, made of all-D amino acids) and RI analogues. Recognition of peptides S12, S12-R, S12-I and S12-RI by anti-B13 antibodies in sera from T. cruzi-infected patients was tested in competitive ELISA assay with recombinant B13 protein as the solid phase antigen. Peptides S15.7 and its topological analogues were tested at the 10-50 microM range in proliferation assays on peripheral blood mononuclear cells (PBMC) from S15.7-responder individuals. The median percentage inhibition of B13 ELISA for peptide S12 was 94%, while those of the RI analogue or the other topological analogues were below 12%. While peptide S15.7 was recognized by PBMC from all subjects tested, none recognized the RI analogue of the S15.7 T cell epitope. Our results indicate that cross-reactivity with natural epitopes is not an universal property of RI analogues. This may limit the general applicability of the use of cross-reactive RI analogues as human vaccines and immunotherapeutic agents.

Trypanosoma cruzi: conformational preferences of antigenic peptides bearing the immunodominant epitope of the B13 antigen

The Trypanosoma cruzi recombinant protein B13 contains tandemly repeated domains and shows high sensitivity in the serological diagnosis of Chagas' disease. It has been shown that the immunodominant epitope of B13 is contained in the GDKPSLFGQAAAGDKPSLF-NH(2) sequence and that the hexapeptide AAAGDK seems to be the "core" of that epitope. Three peptides containing that "core" sequence, one corresponding to the entire repeat motif GDKPSLFGQAAAGDKPSLF-NH(2), pB13, and two smaller fragments, FGQAAAGDK-NH(2), S4, and QAAAGDKPS-NH(2), S5, have been tested in competitive ELISA with recombinant protein B13 in the solid phase against 40 chagasic sera from Brazilian patients. The median percentage inhibition for pB13, S4, and S5 were, respectively, 91, 86, and 68%. The possibility that the distinct antigenic activity of those peptides correlates with the existence of preferential conformational properties has been investigated by CD and NMR spectroscopy. Results indicate their propensity to adopt a helical configuration, centered in the AAAGDK sequence, and whose extent and stability directly correlates with the peptides' antigenicity. The data are discussed in the light of the existence of conformational preferences involving immunodominant epitopes in tandemly repeated antigens.