Thomas S. Harrison

Clinical Practice Guidelines for the Management of Cryptococcal Disease: 2010 Update by the Infectious Diseases Society of America

Cryptococcosis is a global invasive mycosis associated with significant morbidity and mortality. These guidelines for its management have been built on the previous Infectious Diseases Society of America guidelines from 2000 and include new sections. There is a discussion of the management of cryptococcal meningoencephalitis in 3 risk groups: (1) human immunodeficiency virus (HIV)-infected individuals, (2) organ transplant recipients, and (3) non-HIV-infected and nontransplant hosts. There are specific recommendations for other unique risk populations, such as children, pregnant women, persons in resource-limited environments, and those with Cryptococcus gattii infection. Recommendations for management also include other sites of infection, including strategies for pulmonary cryptococcosis. Emphasis has been placed on potential complications in management of cryptococcal infection, including increased intracranial pressure, immune reconstitution inflammatory syndrome (IRIS), drug resistance, and cryptococcomas. Three key management principles have been articulated: (1) induction therapy for meningoencephalitis using fungicidal regimens, such as a polyene and flucytosine, followed by suppressive regimens using fluconazole; (2) importance of early recognition and treatment of increased intracranial pressure and/or IRIS; and (3) the use of lipid formulations of amphotericin B regimens in patients with renal impairment. Cryptococcosis remains a challenging management issue, with little new drug development or recent definitive studies. However, if the diagnosis is made early, if clinicians adhere to the basic principles of these guidelines, and if the underlying disease is controlled, then cryptococcosis can be managed successfully in the vast majority of patients.

Combination antifungal therapies for HIV-associated cryptococcal meningitis: a randomised trial

BACKGROUNDnIt frequently takes more than 2 weeks for drug treatments for cryptococcal meningitis to sterilise cerebrospinal fluid (CSF). In-vitro and animal studies lend support to the use of combinations of amphotericin B, flucytosine, and fluconazole for treatment of cryptococcosis. We compared the fungicidal activity of combinations of these drugs for initial treatment of patients with cryptococcal meningitis.nnnMETHODSn64 patients with a first episode of HIV-associated cryptococcal meningitis were randomised to initial treatment with: amphotericin B (0.7 mg/kg daily); amphotericin B plus flucytosine (100 mg/kg daily); amphotericin B plus fluconazole (400 mg daily); or triple therapy with amphotericin B, flucytosine, and fluconazole. Our primary endpoint was fungicidal activity, measured by the rate of reduction in CSF cryptococcal colony-forming units (CFU) from serial quantitative CSF cultures on days 3, 7, and 14 of treatment.nnnFINDINGSnBaseline CSF CFU counts were an important prognostic factor. Clearance of cryptococci from the CSF was exponential and was significantly faster with amphotericin B plus flucytosine than with amphotericin B alone (p=0.0006), amphotericin B plus fluconazole ( p=0.02), or triple therapy (p=0.02).nnnINTERPRETATIONnAt these doses, amphotericin B plus flucytosine is the most rapidly fungicidal regimen. Quantification of CSF cultures provides a powerful new means to accurately assess the fungicidal activity of new treatment regimens for cryptococcal meningitis.

Symptomatic Relapse of HIV-Associated Cryptococcal Meningitis after Initial Fluconazole Monotherapy: The Role of Fluconazole Resistance and Immune Reconstitution

BACKGROUNDnCryptococcal meningitis (CM) in South Africa is often treated with fluconazole as initial therapy. Surveillance data suggest that the prevalence of fluconazole-resistant CM is increasing, and expanding access to antiretroviral therapy is resulting in increasing recognition of immune reconstitution inflammatory syndrome. Therefore, we conducted a study to assess the contribution of these factors to CM relapse in this context.nnnMETHODSnPatients with symptomatic relapse of CM were prospectively identified at 2 hospitals in Cape Town, South Africa, during the period of 2003-2005. Patients met the following criteria: (1) a previous laboratory-confirmed episode of CM, with resolution of symptoms after treatment; (2) reported adherence to fluconazole treatment; (3) recurrence of typical CM symptoms; (4) cerebrospinal fluid antigen test and/or culture positive for Cryptococcus neoformans; and (5) no alternative diagnosis. Data on patients human immunodeficiency virus (HIV) and CM infections and treatment were collected and analyzed.nnnRESULTSnThirty-two episodes of relapse occurred among 27 patients. Episodes were classified into 3 groups: culture-positive episodes in antiretroviral therapy-naive patients (6 episodes), culture-positive episodes in patients receiving antiretroviral therapy (15 episodes), and culture-negative episodes in patients receiving antiretroviral therapy (11 episodes). Seventy-six percent of culture-positive relapses were associated with isolates that had reduced susceptibility to fluconazole. Drug-resistant cases required prolonged intravenous therapy with amphotericin B, and despite this treatment, the mortality rate was high (54% at a median of 6 months of follow-up). Despite a long interval between initiation of antifungal therapy and initiation of antiretroviral therapy (median interval, 144 days), immune reconstitution inflammatory syndrome contributed to at least one-third of relapses.nnnCONCLUSIONSnAfter initial treatment with fluconazole, relapses of symptomatic CM are often associated with fluconazole resistance and immune reconstitution inflammatory syndrome. These data add to concern about the efficacy of fluconazole, compared with amphotericin B, for initial treatment of HIV-associated CM.

IFN-gamma at the site of infection determines rate of clearance of infection in cryptococcal meningitis.

In animal models, immunity to cryptococcal infection, as in many chronic fungal and bacterial infections, is associated with a granulomatous inflammatory response, intact cell-mediated immunity, and a Th1 pattern of cytokine release. To examine the correlates of human immunity to cryptococcal infection in vivo, we analyzed immune parameters at the site of infection over time and assessed the rate of clearance of infection by serial quantitative cerebrospinal fluid (CSF) fungal cultures in 62 patients in a trial of antifungal therapy for HIV-associated cryptococcal meningitis. CSF IL-6, IFN-γ, TNF-α, and IL-8 were significantly higher in survivors compared with nonsurvivors. There were negative correlations between log TNF-α, IFN-γ, and IL-6 levels and baseline cryptococcal CFU. Log IFN-γ, G-CSF, TNF-α, and IL-6 were correlated positively with the rate of fall in log CFU/ml CSF/day. In a linear regression model including antifungal treatment group, baseline CFU, and these cytokines, only treatment group and log IFN-γ remained independently associated with rate of clearance of infection. The results provide direct in vivo evidence for the importance of quantitative differences in IFN-γ secretion in human immune control of granulomatous infections, and increase the rationale for adjunctive IFN-γ in the treatment of refractory HIV-associated cryptococcosis.

Flucytosine and cryptococcosis: time to urgently address the worldwide accessibility of a 50-year-old antifungal

Current, widely accepted guidelines for the management of HIV-associated cryptococcal meningoencephalitis (CM) recommend amphotericin B combined with flucytosine (5-FC) for ≥2 weeks as the initial induction treatment of choice. However, access to flucytosine in Africa and Asia, where disease burden is greatest, is inadequate at present. While research into identifying effective and well-tolerated antifungal combinations that do not contain flucytosine continues, an ever-increasing body of evidence from in vitro, in vivo and clinical studies points to the benefits of flucytosine in the treatment of CM in both intravenous combinations with amphotericin B and oral combinations with high-dose fluconazole. This article provides an up-to-date review of this evidence, and the current issues and challenges regarding increasing access to this key component of combination antifungal therapy for cryptococcosis.

Low Diversity Cryptococcus neoformans Variety grubii Multilocus Sequence Types from Thailand Are Consistent with an Ancestral African Origin

The global burden of HIV-associated cryptococcal meningitis is estimated at nearly one million cases per year, causing up to a third of all AIDS-related deaths. Molecular epidemiology constitutes the main methodology for understanding the factors underpinning the emergence of this understudied, yet increasingly important, group of pathogenic fungi. Cryptococcus species are notable in the degree that virulence differs amongst lineages, and highly-virulent emerging lineages are changing patterns of human disease both temporally and spatially. Cryptococcus neoformans variety grubii (Cng, serotype A) constitutes the most ubiquitous cause of cryptococcal meningitis worldwide, however patterns of molecular diversity are understudied across some regions experiencing significant burdens of disease. We compared 183 clinical and environmental isolates of Cng from one such region, Thailand, Southeast Asia, against a global MLST database of 77 Cng isolates. Population genetic analyses showed that Thailand isolates from 11 provinces were highly homogenous, consisting of the same genetic background (globally known as VNI) and exhibiting only ten nearly identical sequence types (STs), with three (STs 44, 45 and 46) dominating our sample. This population contains significantly less diversity when compared against the global population of Cng, specifically Africa. Genetic diversity in Cng was significantly subdivided at the continental level with nearly half (47%) of the global STs unique to a genetically diverse and recombining population in Botswana. These patterns of diversity, when combined with evidence from haplotypic networks and coalescent analyses of global populations, are highly suggestive of an expansion of the Cng VNI clade out of Africa, leading to a limited number of genotypes founding the Asian populations. Divergence time testing estimates the time to the most common ancestor between the African and Asian populations to be 6,920 years ago (95% HPD 122.96 - 27,177.76). Further high-density sampling of global Cng STs is now necessary to resolve the temporal sequence underlying the global emergence of this human pathogen.

Dengue Hemorrhagic Fever with Fulminant Hepatic Failure in an Immigrant Returning to Bangladesh

An immigrant from Bangladesh living in the United Kingdom presented with a nonspecific febrile illness after visiting his homeland and subsequently developed fulminant hepatic failure accompanied by hypotension, ascites, a generalized coagulopathy, and thrombocytopenia. Serology and detection of dengue virus serotype 3 by PCR established a postmortem diagnosis of hepatic failure secondary to dengue hemorrhagic fever.

Baseline Correlation and Comparative Kinetics of Cerebrospinal Fluid Colony-Forming Unit Counts and Antigen Titers in Cryptococcal Meningitis

Cerebrospinal fluid (CSF) cryptococcal colony-forming unit counts and CSF cryptococcal antigen titers serve as alternative measures of organism load in cryptococcal meningitis. For these measures, we correlated baseline values and rates of decline during the first 2 weeks of therapy in 68 human immunodeficiency virus--seropositive patients with cryptococcal meningitis. At baseline, there was a strong correlation between CSF cryptococcal colony-forming unit counts and CSF cryptococcal antigen titers. During the first 2 weeks of therapy, CSF cryptococcal colony-forming unit counts decreased by >5 logs, and CSF cryptococcal antigen titers decreased by 1.5 dilutions. In individual patients, there was no correlation between the rate of decline in CSF cryptococcal colony-forming unit counts and that in CSF cryptococcal antigen titers.

Conditional Lethality of the Diprotic Weak Bases Chloroquine and Quinacrine against Cryptococcus neoformans

Chloroquine at 10 microM enhances the activity of macrophages against Cryptococcus neoformans but does not directly inhibit cryptococcal growth. The antifungal activity of higher chloroquine concentrations likely to be found within the acidic cryptococcal phagosome was tested. Concentrations of >/=30 microM inhibited cryptococcal growth, and there was fungal killing at concentrations of >/=100 microM. Activity was dependent on physiologic temperature and pH. Quinacrine was 50-fold more active than chloroquine, and concentrations as low as 100 nM enhanced macrophage anticryptococcal activity. Quinacrine was concentrated within a vacuolar system within the fungal cell and highly concentrated within intracellular C. neoformans. Ammonium chloride and bafilomycin A both inhibited cryptococcal growth, suggesting that the activity of chloroquine and quinacrine may in part be due to disruption of pH-dependent processes. These findings add to the known spectrum of activity of chloroquine and quinacrine. These, and related compounds, may have utility for the treatment of cryptococcosis.

Induction of Human Immunodeficiency Virus Type 1 Expression in Monocytic Cells by Cryptococcus neoformans and Candida albicans

Because candidiasis and cryptococcosis are common in human immunodeficiency virus (HIV)-infected persons, the effect of Cryptococcus neoformans and Candida albicans on HIV expression in monocytic cells was examined. Stimulation of the latently HIV-infected myelomonocytic cell line OM-10.1 with C. neoformans and C. albicans in the presence of pooled human serum caused a ratio-dependent increase in HIV production. Induction of HIV by C. neoformans was enhanced by anti-capsular antibody, while induction by both organisms was inhibited by anti-TNF-alpha antibody. In THP-1 cells transfected with HIV plasmid constructs, both organisms induced transcription from the HIV long terminal repeat that was dependent on intact NF-kappaB binding sequences. Thus, C. neoformans and C. albicans enhance HIV expression in monocytic cells through a TNF-alpha- and NF-kappaB-dependent mechanism. In HIV-infected patients, such enhancement may further impair host immunity and could accelerate the course of HIV disease.