title: Anti-fixed Leishmania chagasi promastigotes IgG antibodies detected by flow cytometry (FC-AFPA-IgG) as a tool for serodiagnosis and for post-therapeutic cure assessment in American visceral leishmaniasis.
abstract: Visceral leishmaniasis (VL) is a systemic infection, caused by an intracellular protozoan parasite belonging to the Leishmania donovani complex. The diagnosis of VL is complex because most clinical features are shared with other commonly occurring febrile hepatosplenic diseases that can be endemic along with VL. A number of serological devices are available but still require improvement mainly due to residual post-therapeutic serology and the cross-reactivity with other Trypanosomatidae protozooses. This study intended to describe and evaluate the performance of an indirect immunofluorescence assay referred as flow cytometry anti-fixed Leishmania chagasi promastigote IgG antibodies (FC-AFPA-IgG) for serodiagnosis of VL and assessment of post-therapeutic cure. The sera reactivity is reported as the percentage of positive fluorescent parasite (PPFP) along the titration curve. The analysis of sera titration curve indicated the sera dilution 1/32,000 and the PPFP=25% as the cut-off to segregate positive and negative results. Using these parameters, the FC-AFPA-IgG displayed outstanding sensitivity and specificity for diagnosis and post-therapeutic cure assessment purposes. The inter-test reproducibility of FC-AFPA-IgG was also verified, considering two independent Analysts and validated the results obtained by FC-AFPA-IgG. Moreover, the comparison between FC-AFPA-IgG and the conventional serologic test (ELISA) showed that besides the statistically analogous results with strong positive correlation the FC-AFPA-IgG displayed higher performance indexes. Further analysis demonstrated that while cross-reactivity was observed in 8% of samples tested by ELISA, no cross-reactivity was detected by FC-AFPA-IgG. Together, the findings presented in this study showed the potential of FC-AFPA-IgG in both diagnosis and post-therapeutic cure assessment of VL.
authors.affiliation: Centro de Pesquisas René Rachou, Laboratório de Biomarcadores de Diagnóstico e Monitoração, Fundação Oswaldo Cruz, Avenida Augusto de Lima 1715, 30190-002, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Lúcia Maria
authors.initials: LM
authors.lastname: Garcia
authors.forename: Jordana Grazziela Alves
authors.initials: JG
authors.lastname: Coelho-Dos-Reis
authors.forename: Vanessa
authors.initials: V
authors.lastname: Peruhype-Magalhães
authors.forename: Andréa
authors.initials: A
authors.lastname: Teixeira-Carvalho
authors.forename: Roberta Dias Rodrigues
authors.initials: RD
authors.lastname: Rocha
authors.forename: Márcio Sobreira Silva
authors.initials: MS
authors.lastname: Araújo
authors.forename: Izabelle Teixeira
authors.initials: IT
authors.lastname: Gomes
authors.forename: Sílvio Fernando Guimarães
authors.initials: SF
authors.lastname: Carvalho
authors.forename: Reynaldo
authors.initials: R
authors.lastname: Dietze
authors.forename: Elenice Moreira
authors.initials: EM
authors.lastname: Lemos
authors.forename: Mariléia Chaves
authors.initials: MC
authors.lastname: Andrade
authors.forename: Olindo Assis
authors.initials: OA
authors.lastname: Martins-Filho
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood* / Q000276:immunology; D003429:Cross Reactions / Q000276:immunology; D005434:Flow Cytometry / Q000379:methods*; D019084:Fluorescent Antibody Technique, Indirect / Q000379:methods; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D007891:Leishmania; D007898:Leishmaniasis, Visceral / Q000097:blood* / Q000175:diagnosis / Q000276:immunology / Q000628:therapy; D012680:Sensitivity and Specificity; D012698:Serologic Tests / Q000379:methods
chemical_list: D000913:Antibodies, Protozoan; D007074:Immunoglobulin G