Efficacy of Antifungal Therapeutics to Clear Cerebrospinal Fluid and Tissue Invasive Cryptococcal Fungal Infection with Antemortem-to-Postmortem Autopsy-Defined Correlates of Infection

In living individuals, it is difficult to obtain especially brain tissues to determine tissue invasive fungal infections to examine the pathogenesis information and mechanisms of infection/disease to better understand the clinical presentations and efficacy of treatment to inform evidence-based clinical trials and clinical practices. The efficacy and degree of antifungal drug penetration to clear foci of invasive infection in the CSF compared to tissue infection are not known. Unlike the limited diagnostic examinations in life, autopsy offers an extra competitive advantage to sample, harvest, and examine different organ and tissue compartments and foci of invasive infections in tissues, blood, CSF, and other perivascular spaces and organs with ease among consented autopsies. This study seeks to perform comparative diagnostic cryptococcal fungal cultures, antifungal drug susceptibility testing, and pharmacometric measurement of antifungal drug levels antemortem in CSF and postmortem in autopsy harvested CSF, and fresh minced and homogenized brain-tissue to determine the efficacy of antifungal drugs used in the treatment of cryptococcal meningitis. The study is important and timely given the persistent high mortality and limited decades of antifungal compounds used in the treatment of cryptococcal meningitis. This study is important given the similarity of postmortem anatomical brain pathology damage response features observed between untreated and treated decedents of cryptococcosis.

Research Significance

This study is important given the similarity of the human brain anatomical pathological and damage-associated features in our cohort among untreated decedents at diagnosis (Figure 1) and decedents with simingly persistent infection at seven months of antifungal treatment (Figure 2) pilot data. This data and findings raise the important questions on the potential generalization of the measured degree of successful fungal treatment, fungal clearance, or antimicrobial sterility demonstrated in CSF compared to systemic disseminated tissues invasive cryptococcal infections in the brain parenchyma and in other organs (Klock et al.). Apart from the multiple foci of infection in the brain, other organs are involved, including adrenal glands, spleen, pancreas, lungs, kidneys et cetera (Klock et al.). In vitro Bulb C mice cryptococcal infection and antifungal treatment models, unlike the total fungal clearance in the kidneys and lung during the eight days of the experimental Amphotericin B, the fungal burden in the brain only reduced by approximately 50% (Thammasit et al.). The bioavailability of amphotericin B in the rabbit model of cryptococcal infection and treatment was dependent on a function of passive drug penetration through the disrupted blood-brain barrier with high concentration of the drug on literary pervious necrotic tissues (Petraitis et al.). The intact impervious blood-brain barrier limited amphotericin B drug penetration (Petraitis et al.), potentially offering enhanced opportunity for invasive infections to thrive and persist in disseminated tissues despite the use of antifungal therapy. Though alternative drug delivery systems exist, including the use of encocleated antifungals bound in nanoparticles (Boulware et al.), designed to be ingested by macrophages to deliver antifungals into the cytoplasmic infection (Staedtke et al.), the walling of macrophages in granulomatous lesions can shield fungal infection and limit the application of this antifungal drug delivery system. The immunohistochemical brain tissues examination at autopsy reveals features of brain hypertrophy with multiple foci of fungal-engulfed necrotic brain lesions in the brain parenchyma, (Wappler-Guzzetta et al.; Shimoda et al.). These observations show possible multiple fungal pathogenesis escape and tissue invasion mechanisms leading to cryptococcal infection and persistence in niches with limited access to immune response and/or limited capability of drug penetration. The limitation of the existing antigen and DNA-based diagnostic testing platforms to distinguish between active, cured, and/or dormant cryptococcal infection is a harbinger to accurate determination of antifungal drug efficacy and prognostic biomarker discovery.

Publications

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Mentors

• • David Boulware, MD/PhD, MPH, CTropMed
  • David Meya, MBChB, MMed, PhD
  • Nicol Melanie, PharmD, PhD
  • Caleb P. Skipper, MD

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