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Trypanosoma cruzi: detection of a surface antigen cross-reactive to human C-reactive protein
C M Melo Coutinho1, G H Cavalcanti, M C Bonaldo
1Depto. Ultra-estrutura e Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil 4365, Rio de Janeiro, RJ, 21045-900, Brasil. claudia@gene.dbbm.fiocruz.br
Insights
Researchers found a C-reactive protein (CRP)-like molecule on the surface of the parasite Trypanosoma cruzi. This discovery may explain previous cross-reactivity findings and offers new avenues for understanding Chagas
Area of Science:
- Immunology
- Parasitology
- Biochemistry
Background:
- C-reactive protein (CRP) is an acute phase protein with known roles in inflammation.
- Elevated CRP levels are observed during the acute phase of Chagas' disease, caused by Trypanosoma cruzi.
- The precise role of CRP in T. cruzi infections and previous observations of antibody cross-reactivity remain unclear.
Purpose of the Study:
- To investigate the cross-reactivity between anti-human CRP antibodies and Trypanosoma cruzi.
- To identify potential CRP-like molecules expressed by T. cruzi.
- To explore the functional implications of this interaction in the context of Chagas' disease.
Main Methods:
- Indirect immunofluorescence, immunoenzymatic assays, flow cytometry, and Western blot were used to detect antibody binding.
- Dose-dependency, saturation, and competitive inhibition assays assessed antibody binding specificity.
- Western blot analysis identified the molecular weight of the recognized antigen.
- Functional assays evaluated the effect of anti-CRP antibodies on parasite invasion.
Main Results:
- Multiple polyclonal and monoclonal anti-human CRP antibodies demonstrated specific, saturable binding to the surface of T. cruzi.
- Western blot analysis revealed a T. cruzi surface protein antigenically related to CRP, with a molecular weight below 23 kDa.
- Divalent cation chelators affected the recognition of the parasite antigen by anti-CRP antibodies.
- A polyclonal anti-human CRP antibody inhibited the invasion of heart muscle cells by T. cruzi.
Conclusions:
- A molecule antigenically similar to human C-reactive protein (CRP) is expressed on the surface of Trypanosoma cruzi.
- This CRP-like molecule may be responsible for the observed cross-reactivity with anti-CRP antibodies.
- The findings suggest a potential role for this molecule in the host-parasite interaction during Chagas' disease.
Abstract:
C-reactive protein (CRP) is an acute phase protein secreted by liver hepatocytes, and is also found on the surface of lymphocytes and as a membrane-associated protein expressed on rat liver macrophages and human monocytes. C-reactive protein levels increase in the sera of children infected with Trypanosoma cruzi, during the acute phase of Chagas' disease, but its role in the course of this infection is unknown. Experiments designed to detect the binding of CRP to circulating forms of T. cruzi failed to observe it because anti-human CRP antibodies bind to the parasite. The present work intended to further clarify this novel question related to the anti-CRP cross-reactivity with the parasite. Indirect immunofluorescence, immunoenzymatic, flow cytometry, and Western blot assays showed that three different polyclonal anti-human CRP antibody preparations bind to T. cruzi surface. This binding is dose-dependent, saturable, and is inhibited when anti-CRP antibodies from different species were allowed to compete, indicating the specificity of the reactivity. The antibodies recognized a protein band below 23 kDa in Western blot analysis of parasite extracts. The divalent cation chelators EDTA and EGTA impaired the antigen recognition by the antibodies. The binding to parasite surface was also observed with some available monoclonal antibodies raised against human CRP. A polyclonal anti-human CRP presented an inhibitory effect on invasion of heart muscle cells by T. cruzi. Our results indicate that a molecule antigenically related to CRP, a possible CRP-like molecule, is expressed on the surface of T. cruzi.