CAMILA APARECIDA DE CARVALHO
Projetos de Pesquisa
Unidades Organizacionais
LIM/49 - Laboratório de Protozoologia, Hospital das Clínicas, Faculdade de Medicina
3 resultados
Resultados de Busca
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- Indirect Evidence of Circulating Parasite Hapten Immune Complexes in Visceral Leishmaniasis(2019) CARVALHO, Camila Aparecida de; FERRAO, Thiago Fidelis; HIRAMOTO, Roberto Mitsuyoshi; PARTATA, Anette Kelsei; ANDRADE JUNIOR, Heitor Franco deBackground: Hypergammaglobulinemia is present in visceral leishmaniasis (VL), inducing the formation of immune complexes (ICs), which interferes in conventional serology. Parasitic haptens block antibodies, making it difficult to identify and detect them. ICs could be determined indirectly by acid dissociative ELISA (DE) seroconversion in natural and experimental VL. Methods: We determined the frequency of samples that seroconverted in DE or presented a 10% increase in DE (Delta DE) in 3 types of VLs-hamster, canine, and human samples-with larger antigen determination by direct antigen capture in experimental samples. Results: The Delta DE frequency is increased in all VL models: human (34%), canine (27%), and hamster (25%) samples. Seroconversion was present in hamster (14%), dog (1%), and human (6%) samples. During experimental infection, higher frequencies (28%) of circulating antigens were observed at the 30th day, associated with higher Delta DE (47%) and seroconversion (22%), with lower frequencies in other periods. Conclusions: The frequency of Delta ED and seroconversion samples found in natural and experimental infection suggests that specific antibodies can be blocked by low molecular weight antigens that interfere qualitatively (seroconversion) or quantitatively (Delta DE) in serology. Several antigen types may be involved, as high molecular weight proteins and low molecular weight glycoconjugates. The higher frequency of those indirect demonstrations of antibody-blocking antigen or haptens that could be acid-removed in VL has implications for the development of assays for detection of circulating or antibody-bound 1- to 3-kDa antigens, which could interfere in diagnosis and also in the immune response of the host.
- Early high avidity specific IgG production in experimental hamster visceral leishmaniasis(2020) CARVALHO, Camila Aparecida de; FERRAO, Thiago Fidelis; CAVALCANTE, Fernanda Siqueira; FREITAS, Flavia Regina Novais de; MEIRELES, Luciana Regina; ANDRADE JUNIOR, Heitor Franco deVisceral leishmaniasis (VL) byLeishmania (Leishmania) infantumis epidemic in Brazil. Hypergammaglobulinemia appears early in patients with VL and is ineffective. Usually, high-affinity IgG B cells are selected during most infections, a critical step for an effective humoral response. The avidity of IgG antibodies in VL is unexplored due to the absence of temporal parameters in most patients, associated to low clinical significance. Experimental infection models overcome this fact, allowing the monitoring of the disease temporal evolution. In this study, the avidity of IgG antibodies was evaluated in experimental models, in infection in hamsters, and in immunization in rabbits. Specific IgG antibodies were detected by ELISA, using chaotropic solution to determine avidity, as reported for viral infections. The levels of IgG antibodies correlated with the progression of experimental infection in hamsters or antigenic stimulation in immunized rabbits. However, IgG avidity was high early in infected animals, even in early periods (> 80%), while in immunized rabbits, they had early antibodies of low avidity with progressive maturation, similar as other infections. These data suggest that the affinity maturation of the avidity of anti-LeishmaniaIgG antibodies promoted at an early stage, influencing the appropriate interaction between antigens and affecting the disease progression. This fact could be associated to monovalent immune complexes, as reported in human and experimental VL. This scenario may be related to an independent process of immune cell activation by the parasite but absent in antigen preparation used as immunogens.
- High levels of serum glycans monovalent IgG immune complexes detected by dissociative ELISA in experimental visceral leishmaniasis(2019) CARVALHO, Camila Aparecida de; FERRAO, Thiago Fidelis; FREITAS, Flavia Regina Novais de; ANDRADE JUNIOR, Heitor Franco deVisceral leishmaniasis (VL) is epidemic in Brazil with an increasing incidence of human cases and canine reservoirs, with host hypergammaglobulinemia. Conventional enzyme-linked immunosorbent assay (cELISA) based on several parasitic antigens is the main method for diagnosis and indication of treatment. Dissociative ELISA (dELISA) uses acidic treatment to free immunoglobulin G (IgG) from immune complexes, and its use revealed a significant positive fraction of suspected cases with negative serology. Looking for small molecules or haptens that block IgG antibodies, we purified by molecular exclusion chromatography, 1000-3000 MW molecules from promastigote soluble extract, mostly oligosaccharides comprising 6-13 sugar residues using MALDI-TOF analysis. Glycan-BSA complex (GBC) was constructed by conjugating promastigote glycans to BSA molecules, allowing their use in the solid support in cELISA or dELISA. Sera from experimentally infected hamsters showed higher levels of blocked monomeric IgG during infection, mostly against GBC, which was also present in lower concentrations in the promastigote soluble extract dELISA. Those data show that most of the specific monomeric IgG in serum are blocked by haptens composed by glycans produced by the parasite, better detected in the high dilution of sera in the dELISA assays. dELISA is a useful technique for detecting blocked monomeric antibodies that could have difficult clearance from blood, which could result in hypergammaglobulinemia.