Evidence of anti-Hcp100 antibodies in COVID-19 critically ill patients with detectable anti-histoplasmin antibodies in a highly endemic area for histoplasmosis.

Patients with severe COVID-19 are at increased risk for invasive fungal infections, which are underestimated. Histoplasmosis reactivation in endemic areas should not be overlooked in this population. In a previous study, seroconversion to anti-histoplasmin antibodies by ELISA was detected in 6/39 (15.4%) patients with severe COVID-19. In this work, samples were further investigated to detect seroconversion to antibodies against the Histoplasma capsulatum 100-kDa antigen (Hcp100) by ELISA. Seroconversion to anti-Hcp100 antibodies was detected in 7/39 patients, of whom 6 also seroconverted anti-histoplasmin antibodies. These results reinforce previous findings that show histoplasmosis as an underdiagnosed fungal entity complicating COVID-19.