Making an Early Diagnosis of Talaromycosis Using a Novel Antigen Test

This study aims to determine the diagnostic and prognostic values and the clinical impact of Talaromyces marneffei antigenemia (TmAg) in patients with advanced HIV disease using a novel enzyme immunoassay (EIA) detecting Tm-specific cell wall mannoprotein Mp1p. The data generated will be used to inform the design of future diagnostic clinical trials to test the utility of screening and providing pre-emptive antifungal therapy to prevent disease and reduce HIV mortality in Southeast Asia.

The primary objective is to screen for TmAg and determine its diagnostic and prognostic performance in symptomatic and asymptomatic HIV-infected patients with a CD4 count ≤100 cells/mm3.

We will test the following hypotheses:

• In symptomatic hospitalized patient Cohort 1, the sensitivity of the Mp1p EIA will be higher than conventional culture method while simultaneously specificity is higher than 95% for diagnosing culture-confirmed talaromycosis over a six-month follow up period
• In asymptomatic outpatient Cohort 2, there will be at least 30% difference in risk of talaromycosis development in TmAg-positive patients compared to TmAg-negative patients over a twelve-month follow up period
• TmAg concentration predicts development of talaromycosis

Secondary Objectives include:

• To assess the impact of presence of TmAg on clinical outcomes, including development of culture-confirmed talaromycosis, incidence of state III and IV AIDS events, subsequent hospitalizations, and death over six- to twelve-month follow up periods
• To compare the diagnostic values of the Mp1p EIA when performed in plasma, sera, and urine samples and when performed in these matrices in combination

We will test the following hypotheses:

• To model the health economic benefits of screening and pre-emptive treatment for pre-clinical infection
• To assess impact on clinic outcomes of screening all patients for cryptococcosis and histoplasmosis
• To collect additional blood samples and store left-over samples for future research to validate infectious disease diagnostics and research to understand genetic susceptibility to infectious diseases relevant to HIV population

Participants in the study, will be asked questions about their medical and travel history. Participants will have blood and urine collected for the Mp1p EIA test to look for early talaromycosis infection and for other tests to look for common HIV-associated infections including tuberculosis, cryptococcosis, and histoplasmosis. They will be examined by a study doctor at least once weekly if they are in the hospital and will be followed in clinic monthly for between 6 and 12 months.

Inclusion criteria

• HIV-1 infection (at least 2 of 3 HIV antibody tests are positive), AND
• HIV-infected age ≥18 years, AND
• CD4 count ≤100 cells/mm3 within the past 3 months, AND
• Antiretroviral therapy (ART) naïve OR recent ART ≤3 months OR suspected or confirmed treatment failure on ART ≥12 months (defined as poor treatment adherence, treatment interruption, or having a confirmed HIV RNA ≥1,000 copies)
• Cohort 1: suspected to have an active infection
• Cohort 2: not suspected to have or being evaluated for an active infection

Exclusion criteria

• Unlikely to attend regular clinic visits
• History of recent talaromycosis or histoplasmosis infection currently on antifungal therapy