Detection of antibody against fungal glucosylceramide in immunocompromised patients: a potential new diagnostic approach for cryptococcosis

Application and evaluation of nucleic acid sequence-based amplification, PCR and cryptococcal antigen test for diagnosis of cryptococcosis

Background

Cryptococcosis is a major opportunistic invasive mycosis in immunocompromised patients, but it is also increasingly seen in immunocompetent patients. In the early stages of cryptococcosis, limitations of the detection method may hinder the diagnosis. A molecular diagnostic technique based on nucleic acid sequence-based amplification (NASBA) method was developed to fulfil the need for efficient diagnosis of cryptococcosis.

Methods

We compared the diagnostic performance of NASBA, PCR and cryptococcal antigen (CrAg) test (colloidal gold method) in clinical samples from 25 cryptococcosis patients (including 8 cryptococcal meningoencephalitis and 17 pulmonary cryptococcosis) who were categorized as proven cases (n = 10) and probable cases (n = 15) according to the revised EORTC/MSG definitions. 10 patients with non-Cryptococcus infection and 30 healthy individuals were categorized as control group.

Results

The lowest detection limit of NASBA was 10 CFU/mL, and RNA of non-target bacteria or fungi was not amplified. The sensitivity of NASBA, PCR and colloidal gold method was 92.00% (95% CI 72.50–98.60%), 64.00% (95% CI 42.62–81.29%), 100.00% (95% CI 83.42–100.00%), and the specificity was 95.00% (95% CI 81.79–99.13%), 80.00% (95% CI 63.86–90.39%) and 82.50% (95% CI 66.64–92.11%) respectively. The highest specificity (97.50%), accuracy (95.38%) and k value (0.90) were achieved when both NASBA and colloidal gold results were positive.

Conclusions

NASBA is a new alternative detection method for cryptococcosis which is both accurate and rapid without expensive equipment and specialised personnel. It may be used as a tool for confirming current infection as well as monitoring the effectiveness of antifungal treatment. The use of NASBA to detect Cryptococcus RNA in blood samples is of great significance for the diagnosis of pulmonary cryptococcosis. The combination of NASBA and colloidal gold can improve the diagnostic accuracy of cryptococcosis.

Sphingolipids: Regulators of azole drug resistance and fungal pathogenicity

In recent years, the role of sphingolipids in pathogenic fungi, in terms of pathogenicity and resistance to azole drugs, has been a rapidly growing field. This review describes evidence about the roles of sphingolipids in azole resistance and fungal virulence. Sphingolipids can serve as signaling molecules that contribute to azole resistance through modulation of the expression of drug efflux pumps. They also contribute to azole resistance by participating in various microbial pathways such as the unfolded protein response (UPR), pH-responsive Rim pathway, and pleiotropic drug resistance (PDR) pathway. In addition, sphingolipid signaling and eisosomes also coordinately regulate sphingolipid biosynthesis in response to azole-induced membrane stress. Sphingolipids are important for fungal virulence, playing roles during growth in hosts under stressful conditions, maintenance of cell wall integrity, biofilm formation, and production of various virulence factors. Finally, we discuss the possibility of exploiting fungal sphingolipids for the development of new therapeutic strategies to treat infections caused by pathogenic fungi.

Immunization Strategies for the Control of Histoplasmosis

Histoplasmosis is an infection caused by the dimorphic fungus Histoplasma capsulatum. Histoplasmosis is typically self-limited and presents asymptomatically in most people. Nevertheless, histoplasmosis can cause severe pulmonary disease and death. Histoplasmosis is increasingly found worldwide; however, it is best documented in the endemic region of the Mississippi river valley system in the Eastern part of the United States (US). Epidemiological studies from the US detailing the morbidity, mortality, and cost associated with histoplasmosis underscore the need to develop a vaccine.

PURPOSE OF REVIEW

This review will detail some of the major developments in potential vaccines against histoplasmosis, with particular emphasis on those that could be used to immunize immunocompromised hosts. Additionally, this review will highlight some non-traditional vaccine-like ideas for the prevention of diverse mycoses.

RECENT FINDINGS

Historically, immunization strategies against histoplasmosis have largely focused on identifying immunogenic proteins that confer protection in animal models. More recently, novel active, therapeutic, and immunomodulatory strategies have been explored as potential alternatives for those with various immune-deficiencies.

SUMMARY

The studies summarized in this review demonstrate that more research is needed to clarify the immunobiology, clinical role and efficacy of each candidate vaccine in the ever-expanding potential armamentarium against histoplasmosis.

Validation and clinical application of a molecular method for the identification of Cryptococcus neoformans/Cryptococcus gattii complex DNA in human clinical specimens

The diagnosis of cryptococcosis is usually performed based on cultures of tissue or body fluids and isolation of the fungus, but this method may require several days. Direct microscopic examination, although rapid, is relatively insensitive. Biochemical and immunodiagnostic rapid tests are also used. However, all of these methods have limitations that may hinder final diagnosis. The increasing incidence of fungal infections has focused attention on tools for rapid and accurate diagnosis using molecular biological techniques. Currently, PCR-based methods, particularly nested, multiplex and real-time PCR, provide both high sensitivity and specificity.

In the present study, we evaluated a nested PCR targeting the gene encoding the ITS-1 and ITS-2 regions of rDNA in samples from a cohort of patients diagnosed with cryptococcosis. The results showed that in our hands, this Cryptococcus nested PCR assay has 100% specificity and 100% sensitivity and was able to detect until 2 femtograms of Cryptococcus DNA.