title: A simple immune complex dissociation ELISA for leishmaniasis: standardization of the assay in experimental models and preliminary results in canine and human samples.
abstract: Visceral leishmaniasis, caused by Leishmania (Leishmania) chagasi, is a chronic parasitic disease of humans and dogs. Confirmation of the protozoal agent in bone marrow, lymph node or spleen aspirate is diagnostic, while specific-IgG serology is used mainly for epidemiology despite the general presence of high levels of serum immunoglobulin. Anecdotal reports of false-negative serology in active disease cases are known and are ascribed to the formation of immune complexes. Because dissociation of immune complexes can be accomplished by acid treatment, we devised a simple, routine enzyme immunoassay (ELISA) for the dissociation of immune complexes in serum samples using acid treatment in wells adsorbed with Leishmania antigen (dELISA). Confirmatory acid dot-blot was also developed for antigen detection by anti-Leishmania rabbit antiserum. In experimental L. chagasi hamster models, immune complexes interfered with ELISA mostly in the 30 and 60 days postinfection, according to both dELISA and antigen dot-blot results. In larger samples from endemic areas, dELISA was positive in 10% of seronegative dog samples (7/70) and 3.5% in negative human samples (3/88), showing that dELISA could be used in the serodiagnosis of visceral leishmaniasis. Moreover, dELISA could be used as an alternative approach to screening asymptomatic visceral leishmaniasis patients, instead of invasive confirmatory testing.
authors.affiliation: Protozoology Laboratory, Instituto de Medicina Tropical de São Paulo, University of São Paulo, São Paulo, SP, Brazil.
authors.forename: Camila Aparecida
authors.initials: CA
authors.lastname: de Carvalho
authors.forename: Anette Kelsei
authors.initials: AK
authors.lastname: Partata
authors.forename: Roberto Mitsuyoshi
authors.initials: RM
authors.lastname: Hiramoto
authors.forename: Samanta Etel Treiger
authors.initials: SE
authors.lastname: Borborema
authors.forename: Luciana Regina
authors.initials: LR
authors.lastname: Meireles
authors.forename: Nanci do
authors.initials: Nd
authors.lastname: Nascimento
authors.forename: Heitor Franco
authors.initials: HF
authors.lastname: de Andrade
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000097:blood*; D000953:Antigens, Protozoan / Q000097:blood* / Q000276:immunology; D006224:Cricetinae; D004195:Disease Models, Animal; D018450:Disease Progression; D004283:Dog Diseases / Q000175:diagnosis / Q000276:immunology / Q000469:parasitology; D004285:Dogs / Q000276:immunology / Q000469:parasitology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007893:Leishmania donovani / Q000276:immunology / Q000472:pathogenicity*; D007898:Leishmaniasis, Visceral / Q000175:diagnosis / Q000662:veterinary*; D008297:Male; D008647:Mesocricetus; D059208:Parasite Load; D011817:Rabbits; D013154:Spleen / Q000469:parasitology; D013997:Time Factors
chemical_list: D000936:Antigen-Antibody Complex; D000953:Antigens, Protozoan