Rev Iberoam Micol. 2019;36(4):186–191 Revista Iberoamericana de Micología w w w.e l s evier.es/reviberoammicol Original article Identifying molecularly defined antigens for a Histoplasma capsulatum-specific interferon gamma release assay Marcela Rubio-Carrasquilla a,b , Rodrigo Ochoa c , Cristian Santa d , Allan J. Guimarães e , Luz Elena Cano a,f , Ernesto Moreno g,∗ a Grupo de Micología Médica y Experimental, Corporación para Investigaciones Biológicas (CIB), Medellín, Colombia b Instituto de Biología, Universidad de Antioquia, Medellín, Colombia c Programa de Estudio y Control de Enfermedades Tropicales – PECET, Universidad de Antioquia, Medellín, Colombia d Universidad Nacional de Colombia, Sede Medellín, Medellín, Colombia e Depto de Microbiologia e Parasitologia, Universidade Federal Fluminense, Niterói, RJ, Brazil f Escuela de Microbiología, Universidad de Antioquia, Medellín, Colombia g Facultad de Ciencias Básicas, Universidad de Medellín, Medellín, Colombia a r t i c l e i n f o Article history: Received 30 November 2018 Accepted 14 June 2019 Available online 19 November 2019 Keywords: Histoplasma capsulatum IGRA Molecularly defined antigens Immunogenic proteins T-cell epitopes a b s t r a c t Background: In a previous work we showed the feasibility of an interferon gamma release assay (IGRA) for detecting latent infection by Histoplasma capsulatum. While in that proof-of-concept study we used crude fungal extracts as antigens, the newest IGRAs developed for other infections are based on molecularly defined antigens, mostly on mixtures of immunogenic peptides. Aims: To identify proteins in H. capsulatum that might serve as molecularly defined antigens for an IGRA test. Methods: We surveyed the literature looking for known H. capsulatum-immunogenic proteins and assayed two of them as antigens in an IGRA test, in a study that involved 80 volunteers. Furthermore, we used several bioinformatics tools to identify specific H. capsulatum proteins and to analyze possible strategies for the design of H. capsulatum-specific immunogenic peptides. Results: Seven H. capsulatum-immunogenic proteins were retrieved from the literature. IGRA tests using either the heat shock protein 60 or the M antigen showed high sensitivities but low specificities, most likely due to the high sequence similarity with the corresponding orthologs in other pathogenic microor- ganisms. We identified around 2000 H. capsulatum-specific proteins, most of which remain unannotated. Class II T-cell epitope predictions for a small number of these proteins showed a great variability among different alleles, prompting for a “brute force” approach for peptide design. Conclusions: The H. capsulatum genome encodes a large number of distinctive proteins, which represent a valuable source of potential specific antigens for an IGRA test. Among them, the Cfp4 protein stands out as a very attractive candidate. © 2019 Asociaci ´ on Espa ˜ nola de Micolog´ ıa. Published by Elsevier Espa ˜ na, S.L.U. All rights reserved. Identificación de antígenos definidos molecularmente para un ensayo de liberación de interferón-gamma específico para Histoplasma capsulatum Palabras clave: Histoplasma capsulatum IGRA Antígenos definidos molecularmente Proteínas inmunogénicas Epítopos de células T r e s u m e n Antecedentes: En un trabajo anterior mostramos la viabilidad de un ensayo de liberación de interferón- gamma (IGRA) para detectar la infección latente por Histoplasma capsulatum. En esa prueba de concepto utilizamos extractos crudos del hongo como antígenos; sin embargo, los IGRA de última generación desarrollados para otras infecciones se basan en antígenos definidos molecularmente, principalmente en mezclas de péptidos inmunogénicos. ∗ Corresponding author. E-mail address: emoreno@udem.edu.co (E. Moreno). https://doi.org/10.1016/j.riam.2019.06.002 1130-1406/© 2019 Asociaci ´ on Espa ˜ nola de Micolog´ ıa. Published by Elsevier Espa ˜ na, S.L.U. All rights reserved.