New antigens for the serological diagnosis of human visceral leishmaniasis identified by immunogenomic screening

• Published in: PloS one 2018-12, Vol.13 (12), p.e0209599-e0209599
• Main Authors: Carvalho, Ana Maria Ravena Severino, Mendes, Tiago Antônio de Oliveira, Coelho, Eduardo Antonio Ferraz, Duarte, Mariana Costa, Menezes-Souza, Daniel
• Format: Article
• Language: English
• Subjects: Animals; Antigens; Antigens, Protozoan - blood; Antigens, Protozoan - immunology; Biology and Life Sciences; Biopsy; Bone marrow; Brazil; Care and treatment; Chagas disease; Chagas Disease - blood; Chagas Disease - immunology; Chagas Disease - parasitology; Cross Reactions; Cross-reactivity; Diagnosis; Diagnostic systems; Diagnostic Tests, Routine; Disease control; Dog Diseases - blood; Dog Diseases - epidemiology; Dog Diseases - parasitology; Dogs; Early Diagnosis; Enzyme-Linked Immunosorbent Assay; Enzymes; Epitopes; Euthanasia; Genetic aspects; Genetic testing; Genomics; Humans; Immune system; Immunoassay; Immunogenetics - methods; Immunology; Infectious diseases; Laboratory animals; Leishmania infantum - immunology; Leishmania infantum - isolation & purification; Leishmania infantum - pathogenicity; Leishmaniasis, Visceral - blood; Leishmaniasis, Visceral - immunology; Leishmaniasis, Visceral - parasitology; Lymphatic system; Lymphocytes B; Medical diagnosis; Medical screening; Medical treatment; Medicine and Health Sciences; Methods; Parasites; Parasitic diseases; Parasitology; Peptides; Proteins; Proteomes; Public health; Reproducibility; Research and Analysis Methods; Serologic Tests; Serological tests; Spleen; Statistical analysis; Strategy; Tropical diseases; Vector-borne diseases; Visceral leishmaniasis
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0209599

Visceral leishmaniasis (VL) still represents a serious public health problem in Brazil due to the inefficiency of the control measures currently employed, that included early diagnosis and treatment of human cases, vector control, euthanasia of infected dogs and, recently approved in Brazil, treatment with Milteforam drug. Effective clinical management depend largely on early and unequivocal diagnosis, however, cross-reactivity have also been described in serological tests, especially when it refers to individuals from areas where Chagas' disease is also present. Thus, to discover new antigens to improve the current serological tests for VL diagnosis is urgently needed. Here, we performed an immunogenomic screen strategy to identify conserved linear B-cell epitopes in the predicted L. infantum proteome using the following criteria: i) proteins expressed in the stages found in the vertebrate host, amastigote stage, and secreted/excreted, to guarantee greater exposure to the immune system; ii) divergent from proteins present in other infectious disease pathogens with incidence in endemic areas for VL, as T. cruzi; iii) highly antigenic to humans with different genetic backgrounds, independently of the clinical stage of the disease; iv) stable and adaptable to quality-control tests to guarantee reproducibility; v) using statistical analysis to determine a suitable sample size to evaluate accuracy of diagnostic tests established by receiver operating characteristic strategy. We selected six predicted linear B-cell epitopes from three proteins of L. infantum parasite. The results demonstrated that a mixture of peptides (Mix IV: peptides 3+6) were able to identify VL cases and simultaneously able to discriminate infections caused by T. cruzi parasite with high accuracy (100.00%) and perfect agreement (Kappa index = 1.000) with direct methods performed by laboratories in Brazil. The results also demonstrated that peptide-6, Mix III (peptides 2+6) and I (peptides 2+3+6) are potential antigens able to used in VL diagnosis, represented by high accuracy (Ac = 99.52%, 99.52% and 98.56%, respectively). This study represents an interesting strategy for discovery new antigens applied to serologic diagnosis which will contribute to the improvement of the diagnosis of VL and, consequently, may help in the prevention, control and treatment of the disease in endemic areas of Brazil.