Summary of Guidelines for Managing Histoplasmosis among People Living with HIV

A global perspective of the changing epidemiology of invasive fungal disease and real-world experience with the use of isavuconazole

Global epidemiological data show that the incidence of invasive fungal disease (IFD) has increased in recent decades, with the rising frequency of infections caused by Aspergillus and Mucorales order species. The number and variety of patients at risk of IFD has also expanded, owing in part to advances in the treatment of hematologic malignancies and other serious diseases, including hematopoietic stem cell transplantation (HCT) and other therapies causing immune suppression. Isavuconazonium sulfate (active moiety: isavuconazole) is an advanced-generation triazole antifungal approved for the treatment of invasive aspergillosis and mucormycosis that has demonstrated activity against a variety of yeasts, moulds, and dimorphic fungi. While real-world clinical experience with isavuconazole is sparse in some geographic regions, it has been shown to be effective and well tolerated in diverse patient populations, including those with multiple comorbidities who may have failed to respond to prior triazole antifungal therapy. Isavuconazole may be suitable for patients with IFD receiving concurrent QTc-prolonging therapy, as well as those on venetoclax or ruxolitinib. Data from clinical trials are not available to support the use of isavuconazole prophylactically for the prevention of IFD or for the treatment of endemic IFD, such as those caused by Histoplasma spp., but real-world evidence from case studies suggests that it has clinical utility in these settings. Isavuconazole is an option for patients at risk of IFD, particularly when the use of alternative antifungal therapies is not possible because of toxicities, pharmacokinetics, or drug interactions.

Disseminated histoplasmosis: Long journey of a febrile young man

A 19-year-old non-diabetic, non-HIV male presented with eighteen months of fever, weight loss, skin rash and lymphadenopathy. He was treated with anti-tubercular medication for more than twelve months in multiple institutions based on repeated biopsy reports of lymph nodes showing granuloma suggestive of tuberculosis. Before he was diagnosed at Bangabandhu Sheikh Mujib Medical University (BSMMU) with disseminated histoplasmosis at eighteen months of his disease, he already lost twenty kg weight, developed multiple small joint pain, back pain, and cough along with previously mentioned symptoms. Extensive investigations at BSMMU revealed biopsy material from multiple sites showed noncaseating granulomas with Periodic acid-Schiff (PAS) stain positive for budding oval yeast cells, and fungal culture revealed growth of dimorphic fungus suggestive of Histoplasma after three weeks. After treatment with intravenous liposomal amphotericin B with continuous itraconazole, the patient's fever completely subsided, his well-being improved, joint pain reduced, started to gain weight, and skin lesions started to heal. This case serves as a significant reminder that it is imperative to consider alternative diagnoses in patients who fail to show improvement with conventional antitubercular treatment.

Rapid CD4 cell count determination and Cryptococcus and Histoplasma antigen detection in people living with HIV: Implementation of a package of care strategy in a pilot study, Argentina

Objectives

Despite advancements in HIV diagnosis and treatment, advanced HIV disease (AHD) is still a significant concern worldwide, especially in countries with a high percentage of undiagnosed cases and late-stage diagnoses.

Methods

A prospective pilot study was conducted in Buenos Aires, Argentina to assess the feasibility of implementing a package for people living with HIV, integrating a point-of-care clusters of differentiation (CD4) test, followed by rapid Cryptococcus and Histoplasma antigen (Ag) detection.

Results

A total of 105 people living with HIV were enrolled, during June 2021 to October 2021. The VISITECT CD4 Advanced Disease Lateral Flow Assay (CD4-LFA) (Accubio) classified 98 (93%) patients with AHD. Compared with flow cytometry, the CD4-LFA performed with a high sensitivity (100%) but low specificity (19%) and limited accuracy (47%). In the 98 patients classified with AHD using the CD4-LFA, 16 tested positive for any of the rapid Ag used, including 12 patients positive for the Histoplasma Ag test and four positive for Cryptococcus Ag; all four patients with positive Cryptococcus Ag in sera and were diagnosed with meningitis. In the 30-day follow-up, one death was recorded.

Conclusions

The CD4-LFA correctly classified all patients with CD4 ≤200 cells/µL by flow cytometry, but a high frequency of patients misclassified with AHD was recorded. We also observed a high prevalence of opportunistic fungal infections, as previously observed in the hospital where this pilot study was conducted; however, in contrast with those previous reports, mortality was lower. The study underscores the importance of scaling up comprehensive care strategies and collaborating with governmental and non-governmental partners to enhance access to essential diagnostic tools and treatments for people living with HIV. Further research with larger sample sizes is needed to validate these findings.

Histoplasmosis in Non-HIV Infected Patients: Another Neglected Infection in French Guiana

(1) Background: Only a few studies on histoplasmosis in immunocompetent patients have been reported in French Guiana. Therefore, we conducted a detailed clinical description of hospitalized patients suffering with histoplasmosis among non-HIV patients. (2) Methods: This is a single-center, retrospective study conducted at Cayenne Hospital Center between 2008 and 2022. (3) Results: Our cohort was composed of 31 (91%) adults (>18 years of age) and 3 (9%) children, with a sex ratio, M:F, of 1:2. The median age was higher among the women than among the men (70 versus 54 years). The collection of respiratory samples constituted the majority of the performed examinations (38%). Fever (>37 °C) was found in 56% of patients. Surprisingly, the histoplasmosis was disseminated in 82% of patients with an overall case fatality rate of 14.7%. However, immunosuppressive conditions were found in 52% (16/31) of the adult patients, including lymphoid hemopathies, diabetes and immunosuppressive drugs. Conclusions: This disease, though rare and usually considered a mostly benign disease in non-HIV patients, presented a relatively high mortality rate in our cohort. Thus, histoplasmosis should be suspected, screened and investigated as a first line of defense in highly endemic areas, even in immunocompetent and non-HIV patients, especially those with fever or chronic respiratory symptoms.

Histoplasmosis Beyond Human Immunodeficiency Virus (HIV): Clinical Characteristics and Outcomes in a Non-HIV Population

Histoplasmosis is an endemic and invasive mycosis caused by Histoplasma capsulatum. We conducted a retrospective study comparing immunosuppressed patients without human immunodeficiency virus (HIV) with a historical cohort of people with HIV and histoplasmosis. We included 199 patients with proven or probable histoplasmosis, of which 25.1% were people without HIV. Diabetes mellitus, chronic kidney disease, hematologic neoplasms, rheumatologic diseases, and transplantations were more frequent among people without HIV (P < .01). Forty-four percent of immunocompromised patients without HIV died within the first 6-week period following their diagnosis. A high suspicion index for histoplasmosis should be kept in immunosuppressed patients.

Identification and production of novel potential pathogen-specific biomarkers for diagnosis of histoplasmosis

IMPORTANCE

Histoplasmosis is considered one of the most important mycoses due to the increasing number of individuals susceptible to develop severe clinical forms, particularly those with HIV/AIDS or receiving immunosuppressive biological therapies, the high mortality rates reported when antifungal treatment is not initiated in a timely manner, and the limitations of conventional diagnostic methods. In this context, there is a clear need to improve the capacity of diagnostic tools to specifically detect the fungal pathogen, regardless of the patient's clinical condition or the presence of other co-infections. The proposed novel pathogen-specific biomarkers have the potential to be used in immunodiagnostic platforms and antifungal treatment monitoring in histoplasmosis. In addition, the bioinformatics strategy used in this study could be applied to identify potential diagnostic biomarkers in other models of fungal infection of public health importance.

Closing the Gap in Proteomic Identification of Histoplasma capsulatum: A Case Report and Review of Literature

Histoplasmosis is a globally distributed systemic infection caused by the dimorphic fungus Histoplasma capsulatum (H. capsulatum). This fungus can cause a wide spectrum of clinical manifestations, and the diagnosis of progressive disseminated histoplasmosis is often a challenge for clinicians. Although microscopy and culture remain the gold standard diagnostic tests for Histoplasma identification, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) has emerged as a method of microbial identification suitable for the confirmation of dimorphic fungi. However, to our knowledge, there are no entries for H. capsulatum spectra in most commercial databases. In this review, we describe the case of disseminated histoplasmosis in a patient living with HIV admitted to our university hospital that we failed to identify by the MALDI-TOF method due to the limited reference spectrum of the instrument database. Furthermore, we highlight the utility of molecular approaches, such as conventional polymerase chain reaction (PCR) and DNA sequencing, as alternative confirmatory tests to MALDI-TOF technology for identifying H. capsulatum from positive cultures. An overview of current evidence and limitations of MALDI-TOF-based characterization of H. capsulatum is also presented.

Single High Dose of Liposomal Amphotericin B in Human Immunodeficiency Virus/AIDS-Related Disseminated Histoplasmosis: A Randomized Trial

BACKGROUND

Histoplasmosis is a major AIDS-defining illness in Latin America. Liposomal amphotericin B (L-AmB) is the drug of choice for treatment, but access is restricted due to the high drug and hospitalization costs of the conventional long regimens.

METHODS

Prospective randomized multicenter open-label trial of 1- or 2-dose induction therapy with L-AmB versus control for disseminated histoplasmosis in AIDS, followed by oral itraconazole therapy. We randomized subjects to: (i) single dose 10 mg/kg of L-AmB; (ii) 10 mg/kg of L-AmB on D1, and 5 mg/kg of L-AmB on D3; (iii) 3 mg/kg of L-AmB daily for 2 weeks (control). The primary outcome was clinical response (resolution of fever and signs/symptoms attributable to histoplasmosis) at day 14.

RESULTS

A total of 118 subjects were randomized, and median CD4+ counts, and clinical presentations were similar between arms. Infusion-related toxicity, kidney toxicity at multiple time-points, and frequency of anemia, hypokalemia, hypomagnesemia, and liver toxicity were similar. Day 14 clinical response was 84% for single-dose L-AmB, 69% 2-dose L-AmB, and 74% for control arm (P = .69). Overall survival on D14 was 89.0% (34/38) for single-dose L-AmB, 78.0% (29/37) for 2-dose L-AmB, and 92.1% (35/38) for control arm (P = .82).

CONCLUSIONS

One day induction therapy with 10 mg/kg of L-AmB in AIDS-related histoplasmosis was safe. Although clinical response may be non-inferior to standard L-AmB therapy, a confirmatory phase III clinical trial is needed. A single induction dose would markedly reduce drug-acquisition costs (>4-fold) and markedly shorten and simplify treatment, which are key points in terms of increased access.

The Current and Future States of Diagnostic Tests for Histoplasmosis with a Focus on People with HIV and Disseminated Histoplasmosis

Histoplasmosis is caused by Histoplasma capsulatum and, although endemic in large parts of the world, is often underrecognized in many locations. In addition to underrecognition, inadequate availability of diagnostic tests is a major contributor to poor outcomes in disseminated disease in people with HIV. For those with advanced HIV and disseminated disease, antibody testing is less useful. Culture and histopathology can be useful in this situation, but each has limitations, including variable sensitivity by site and, in the case of culture, the need for a biosafety level three laboratory and a long period of growth. Antigen testing has proven useful for disseminated histoplasmosis due to the excellent sensitivity of urine. Yet, turnaround is slower than ideal due to use in a limited number of centers. The development of lateral flow assays has the potential to make for true rapid point-of-care assays for histoplasmosis, but in order to meet that promise, the tests must be widely available and affordable.

Mebendazole Inhibits Histoplasma capsulatum In Vitro Growth and Decreases Mitochondrion and Cytoskeleton Protein Levels

Histoplasmosis is a frequent mycosis in people living with HIV/AIDS and other immunocompromised hosts. Histoplasmosis has high rates of mortality in these patients if treatment is unsuccessful. Itraconazole and amphotericin B are used to treat histoplasmosis; however, both antifungals have potentially severe pharmacokinetic drug interactions and toxicity. The present study determined the minimal inhibitory and fungicidal concentrations of mebendazole, a drug present in the NIH Clinical Collection, to establish whether it has fungicidal or fungistatic activity against Histoplasma capsulatum. Protein extracts from H. capsulatum yeasts, treated or not with mebendazole, were analyzed by proteomics to understand the metabolic changes driven by this benzimidazole. Mebendazole inhibited the growth of 10 H. capsulatum strains, presenting minimal inhibitory concentrations ranging from 5.0 to 0.08 µM. Proteomics revealed 30 and 18 proteins exclusively detected in untreated and mebendazole-treated H. capsulatum yeast cells, respectively. Proteins related to the tricarboxylic acid cycle, cytoskeleton, and ribosomes were highly abundant in untreated cells. Proteins related to the nitrogen, sulfur, and pyrimidine metabolisms were enriched in mebendazole-treated cells. Furthermore, mebendazole was able to inhibit the oxidative metabolism, disrupt the cytoskeleton, and decrease ribosomal proteins in H. capsulatum. These results suggest mebendazole as a drug to be repurposed for histoplasmosis treatment.

Disseminated histoplasmosis in a patient with chronic lymphoedema

A 54 year-old man with lymphopenia secondary to lymphatic filariasis was admitted with dry cough, fever and wasting syndrome. He was diagnosed with sarcoidosis and therapy with corticosteroid was initiated. The patient evolved with worsening of the symptoms. Histoplasma species was recovered in lung biopsy tissue, lung tissue culture, and bone marrow aspirate. The authors describe the first case of disseminated histoplasmosis secondary to lymphatic filariasis, followed by a literature review. 2012 Elsevier Ltd. All rights reserved.

Establishing the proportion of severe/moderately severe vs mild cases of progressive disseminated histoplasmosis in patients with HIV

Background

Progressive disseminated histoplasmosis remains a major but neglected cause of death among patients with advanced HIV. Recently, aiming to reduce avoidable deaths, the Pan American Health Organization issued the first diagnosis and treatment guidelines for HIV-associated histoplasmosis. But what proportion of progressive disseminated histoplasmosis in HIV-infected patients is severe is currently not known. Because this proportion influences treatment needs, we aimed to estimate this in a cohort of 416 patients in French Guiana.

Methods

We used the definition in the recent PAHO/WHO guidelines for severity. We used regression modelling to predict the impact of CD4 count on the proportion of severe cases. In a territory where treatment cost is not a limiting factor and where histoplasmosis is well known, we assumed that clinicians’ initial treatment reflected their perception about the severity of the case and therefore, the needs for different treatments.

Results

Using these definitions, since the beginning, there were 274 (65.9%) severe/moderately severe cases and 142 (34.1%) mild cases. In practice 186 cases were treated with deoxycholate or liposomal amphotericin B (44.7%) and 230 (55.3%) cases treated with itraconazole as first line treatment. The Kappa concordance measure between the guideline definition and the actual treatment given was 0.22. There was a 9% risk difference for death within 30 days of antifungal treatment initiation between severe/moderately severe and mild cases. Over threequarters (77%) of early deaths were attributed to severe/moderately severe cases.

Conclusions

This is the only rigorous estimate of the proportion of severe/moderately severe cases of progressive disseminated histoplasmosis in symptomatic HIV patients on the largest published cohort. These numbers may help defend budget needs for rapid diagnostic tests and liposomal amphotericin B.

Pulmonary Histoplasmosis

Histoplasmosis is one of the most frequent causes of fungal respiratory infection in endemic regions, has a broad spectrum of clinical manifestations and can present in several forms. The extent of disease is determined by the number of conidia inhaled, the immune response of the host and the integrity of the respiratory tract. From an initial and most benign form, acute pulmonary histoplasmosis (an influenza-like illness that is typically asymptomatic or mild in persons without prior immune compromise), histoplasmosis can become a lifethreatening progressive disseminated infection (PDH) that affects mainly immunocompromised patients, with high morbidity and mortality. Chronic pulmonary histoplasmosis is an uncommon manifestation of Histoplasma infection, with features similar to pulmonary tuberculosis, and if it remains undiagnosed or untreated it also can cause significant morbidity. Some rare but serious complications may also occur that are produced by an excessive immune response, such as mediastinal fibrosis, histoplasmoma and broncholithiasis. Histoplasmosis is highly endemic in regions of North, Central and South America as well as being reported in parts of Asia and Africa. The risk of histoplasmosis is greatest in patients with HIV infection, especially those with CD4⁺ counts of <200 cells/μL. We review clinical manifestations, radiological findings and treatment options according to the clinical form (induction therapy and maintenance therapy), as well as different diagnosis tools and new laboratory tests that have been recently developed and validated and are becoming widely available. These should have an impact in reducing time for diagnosis and starting therapy and in reducing morbidity and mortality, especially in patients with HIV infection, where histoplasmosis is currently estimated to be responsible for 5-15% of AIDS-related deaths.