title: Detection of anti-leishmania (Leishmania) chagasi immunoglobulin G by flow cytometry for cure assessment following chemotherapeutic treatment of American visceral leishmaniasis.
abstract: The residual serological reactivity observed in patients cured of visceral leishmaniasis (VL) represents the major factor underlying the low efficiency of most anti-Leishmania serological approaches to assess posttherapeutic cure in VL. Herein, we have described a detuned flow cytometry-based methodology to detect anti-live (FC-ALPA-immunoglobulin G [IgG]) and anti-fixed (FC-AFPA-IgG) L. chagasi promastigote IgG, along the titration curve (1:2,000 to 1:128,000), as a tool to assess late (12 months after treatment [12 mAT]) and early (2 and 6 mAT) posttherapeutic cure of pediatric American visceral leishmaniasis. Reactivities were reported as the percentage of positive fluorescent parasite (PPFP), using a PPFP of 50% as a cutoff to segregate positive and negative results. Our data demonstrated that both FC-ALPA-IgG at 1:4,000 and FC-ALPA-IgG at 1:32,000 are useful for late cure assessment in VL, with 100% specificity and outstanding likelihood ratio indices. Cure assessment at 6 mAT also showed promising performance indices, identifying 81% and 71.4% of the treated patients with negative results. However, new interpretation parameters were necessary to monitor cure at 2 mAT. We then introduced the differential PPFP (DeltaPPFP) of 25% as a new cutoff for early cure assessment at specific serum dilutions to analyze IgG reactivity by FC-ALPA-IgG and FC-AFPA-IgG. Our data demonstrated that at 2 mAT, DeltaPPFP was >25% in 60% and 57.1% of treated patients, whereas at 6 mAT, a DeltaPPFP of >25% was observed in 100% and 95.2% of samples assayed by FC-ALPA-IgG and FC-AFPA-IgG, respectively. Together, our findings showed the potential of both FC-ALPA-IgG and FC-AFPA-IgG regarding their applicability to detect differential serological reactivity and further contribution to posttherapeutic cure assessment in VL.
authors.affiliation: Núcleo de Doenças Infecciosas, Universidade Federal do Espírito Santo, Av. Marechal Campos, 1648, Maruípe, Vitória ES 29040-091, Brazil. lemosem@ndi.ufes.br
authors.forename: Elenice Moreira
authors.initials: EM
authors.lastname: Lemos
authors.forename: Izabelle Teixeira
authors.initials: IT
authors.lastname: Gomes
authors.forename: Sílvio Fernando Guimarães
authors.initials: SF
authors.lastname: Carvalho
authors.forename: Roberta Dias Rodrigues
authors.initials: RD
authors.lastname: Rocha
authors.forename: Jauber Fornaciari
authors.initials: JF
authors.lastname: Pissinate
authors.forename: Olindo Assis
authors.initials: OA
authors.lastname: Martins-Filho
authors.forename: Reynaldo
authors.initials: R
authors.lastname: Dietze
mesh_terms: D000666:Amphotericin B / Q000627:therapeutic use; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000953:Antigens, Protozoan / Q000276:immunology; D000981:Antiprotozoal Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D007891:Leishmania / Q000276:immunology*; D007898:Leishmaniasis, Visceral / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy*; D008297:Male; D016896:Treatment Outcome
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D000981:Antiprotozoal Agents; D007074:Immunoglobulin G; D000666:Amphotericin B