Early high avidity specific IgG production in experimental hamster visceral leishmaniasis
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IMMUNOLOGY AND HOST-PARASITE INTERACTIONS - SHORT COMMUNICATION
Early high avidity specific IgG production in experimental hamster visceral leishmaniasis Camila Aparecida de Carvalho 1,2 & Thiago Fidelis Ferrão 1 & Fernanda Siqueira Cavalcante 1 & Flavia Regina Novais de Freitas 1 & Luciana Regina Meireles 1 & Heitor Franco de Andrade Júnior 1 Received: 14 May 2020 / Accepted: 9 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Visceral leishmaniasis (VL) by Leishmania (Leishmania) infantum is 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-Leishmania IgG 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. Keywords Leishmania . Experimental infection . IgG . Avidity
Introduction Visceral leishmaniasis (VL) is a neglected parasitic disease endemic among populations of underdeveloped tropical countries. Females of infected sandflies transmit promastigote forms through the bite at the time of blood meal to mammalian hosts (Maroli et al. 2013). Several factors contribute to the territorial expansion of VL, such as increased dog exposure to endemic areas through displacement between regions, as a
Section Editor: Nawal Hijjawi * Camila Aparecida de Carvalho [email protected] 1
Instituto de Medicina Tropical-Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
2
Protozoology Laboratory, Instituto de Medicina Tropical de São Paulo, Avenida Doutor Enéas de Carvalho Aguiar 470, São Paulo, SP 05403-000, Brazil
result of the intrinsic relationship established between man and pets (de Carvalho et al. 2017). VL can present a
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