Dynamics of Histoplasma fungal load in people living with HIV with disseminated histoplasmosis under treatment with liposomal amphotericin B.

Abstract

Objectives: Disseminated histoplasmosis (DH) is a lethal fungal disease in patients living with HIV in endemic regions of the world. Diagnosis relies mainly on microscopy, culture, and antigen detection. Our goal was to evaluate the diagnostic and prognostic role of our RT-quantitative PCR (RT-qPCR) in blood specimens allowing to quantify the whole nucleic acids (WNA) load.

Methods: We tested RT-qPCR assays on serial blood (n = 325) of 105 DH patients at baseline (day 0 or day 1, D0/1) and during antifungal therapy (day 3, D3; day 4 or day 5, D4/5; day 7, D7; and day 14, D14) collected from a phase II trial comparing three different regimens of liposomal amphotericin B for DH treatment in HIV patients from Brazil.

Results: The RT-qPCR was positive at D0/D1 in 64.2% (63/98) of the patients, but positivity increased to 89% (47/53) in patients with proven infection. Urine antigen was positive in 94.2% (97/103) of DH patients. RT-qPCR positive at or after D7 was significantly associated with higher initial WNA load (Cq = 31 [27-34]) when compared with RT-qPCR negative at D7 (Cq = 38 [33-40]) (p 0.001). The WNA load was equivalent in all treatment arms, and an equivalent decrease in the % of RT-qPCR-positive patients was observed in the three arms. Flat of negative WNA slope (increase of WNA load) was associated with an increased relative risk of death at D7 (relative risk, 8.6; p 0.046) and W12 (relative risk, 3.3; p 0.008). This association was not observed when analysing antigen slopes (p > 0.5).

Discussion: We found in this study an association between the progression of flat Histoplasma WNA load during treatment and early death at D7 and D14. This diagnostic tool should be evaluated specifically in a prospective trial to assess its usefulness in identifying patients with poorer prognosis and adapt their treatment accordingly.