Development of peptide-based lineage-specific serology for chronic Chagas disease: geographical and clinical distribution of epitope recognition.
BACKGROUND
Chagas disease, caused by infection with the protozoan Trypanosoma cruzi, remains a serious public health issue in Latin America. Genetically diverse, the species is sub-divided into six lineages, known as TcI-TcVI, which have disparate geographical and ecological distributions. TcII, TcV, and TcVI are associated with severe human disease in the Southern Cone countries, whereas TcI is associated with cardiomyopathy north of the Amazon. T. cruzi persists as a chronic infection, with cardiac and/or gastrointestinal symptoms developing years or decades after initial infection. Identifying an individual's history of T. cruzi lineage infection directly by genotyping of the parasite is complicated by the low parasitaemia and sequestration in the host tissues.


RESULTS
We have applied here serology against lineage-specific epitopes of the T. cruzi surface antigen TSSA, as an indirect approach to allow identification of infecting lineage. Chagasic sera from chronic patients from a range of endemic countries were tested by ELISA against synthetic peptides representing lineage-specific TSSA epitopes bound to avidin-coated ELISA plates via a biotin labelled polyethylene glycol-glycine spacer to increase rotation and ensure each amino acid side chain could freely interact with their antibodies. 79/113 (70%) of samples from Brazil, Bolivia, and Argentina recognised the TSSA epitope common to lineages TcII/TcV/TcVI. Comparison with clinical information showed that a higher proportion of Brazilian TSSApep-II/V/VI responders had ECG abnormalities than non-responders (38% vs 17%; p<0.0001). Among northern chagasic sera 4/20 (20%) from Ecuador reacted with this peptide; 1/12 Venezuelan and 1/34 Colombian samples reacted with TSSApep-IV. In addition, a proposed TcI-specific epitope, described elsewhere, was demonstrated here to be highly conserved across lineages and therefore not applicable to lineage-specific serology.


CONCLUSIONS
These results demonstrate the considerable potential for synthetic peptide serology to investigate the infection history of individuals, geographical and clinical associations of T. cruzi lineages.
Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Tapan
T
Bhattacharyya
Departamento de Medicina, Universidad del Norte, Barranquilla, Colombia.
Andrew K
AK
Falconar
Laboratorio de Chagas, Hospital das Clinicas, Universidade Federal de Goiás, Goiânia, Goias, Brazil.
Alejandro O
AO
Luquetti
Centro de Investigación en Enfermedades Infecciosas, Escuela de Biología, Pontificia Universidad Católica del Ecuador, Quito, Ecuador.
Jaime A
JA
Costales
Centro de Investigación en Enfermedades Infecciosas, Escuela de Biología, Pontificia Universidad Católica del Ecuador, Quito, Ecuador; Tropical Disease Institute, Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America.
Mario J
MJ
Grijalva
Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Michael D
MD
Lewis
Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Louisa A
LA
Messenger
Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Trang T
TT
Tran
Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Bogotá, Colombia.
Juan-David
JD
Ramirez
Centro de Investigaciones en Microbiología y Parasitología Tropical, Universidad de los Andes, Bogotá, Colombia.
Felipe
F
Guhl
Universidad Central de Venezuela Instituto de Medicina Tropical, Caracas, Venezuela.
Hernan J
HJ
Carrasco
Unidad de Epidemiología Molecular, Instituto de Patología Experimental, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Salta, Salta, Argentina.
Patricio
P
Diosque
Facultad de Medicina, Universidad Mayor de San Simón, Cochabamba, Bolivia.
Lineth
L
Garcia
Aptum Biologics Ltd, Southampton, United Kingdom.
Sergey V
SV
Litvinov
Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Michael A
MA
Miles
D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D000953:Antigens, Protozoan / Q000737:chemistry / Q000276:immunology*; D014355:Chagas Disease / Q000276:immunology* / Q000469:parasitology*; D019295:Computational Biology; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000276:immunology*; D012703:Serotyping / Q000379:methods; D013020:South America; D014224:Triatoma / Q000469:parasitology; D014349:Trypanosoma cruzi / Q000145:classification* / Q000276:immunology; D014643:Variant Surface Glycoproteins, Trypanosoma / Q000737:chemistry / Q000276:immunology
D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000939:Epitopes; D010455:Peptides; D014643:Variant Surface Glycoproteins, Trypanosoma; C573505:trypomastigote small surface antigen, Trypanosoma cruzi