Study On Anti-Cryptococcus Effect Of Chloroquine

BACKGROUNDS: The encapsulated yeast Cryptococcus neoformans hasemerged as a major cause of life-threatening meningoencephalitis inimmunocompromised patients, especially those with human immunodeficiency virusinfection. Unfortunately, at present, only a limited number of antifungal agents areavailable to treat these infections, and their efficacy is variable. Furthermore,resistance to some of these agents is now emerging. Clearly, new antifungal drugs areurgently required. While new drugs will take a long time to be used clinically, knowndrugs will be a good choice if it was confirmed to be effective to cryptococcalinfection.Chloroquine was developed in the late 1930s from quinacrine, and was widely usedin the treatment of malaria. Chloroquine is concentrated within the acidic foodvacuole of the malarial parasite, where they are thought to inhibit hematinpolymerization. Very high concentrations of antimalarials have been found to inhibitthe growth of the yeast Saccharomyces cerevisiae. It has been proved that chloroquine,at a concentration, markedly enhances the antimicrobial activity of humanmononuclear phagocytes against C. neoformans. However, to our knowledge, nodirect antifungal activity has previously been reported for these or other relatedantimalarial compounds against any of the pathogenic fungi at pharmacologicallyrelevant concentrations.OBJECTIVES: 1. To investigate whether chloroquine, could inhibit or kill C.neoformans directly and increase the role of important antifungal drugs in treatment of cryptocccosis in vitro. Its role was also analyzed between noncapsuled andcapsuled isolates. 2. In vivo study was done to investigate the role of chloroquine andsynergistic role of chloroquineplus fluconazole against C. neoformans infecton inmice cryptococcosis model, which was immunocompromised or immunocompetent.MATERIALS AND METHODS: 1.C. neoformans cells were incubatedwith different concentrations of chloroquine for various periods. Cell suspensionswith and without chloroquine were incubated for various periods and then plated onSabouraud dextrose agar plates to determine the number of CFU (one colony=1 CFU).For combination effect, Cell suspensions with chloroquine and antifungal drugs andsingle antifungal drug was incubated in 96 well plate and the MIC of fluconazole(Roerig-Pfizer) was determined by the broth macrodilution method, according to theguidelines of the National Committee for Clinical Laboratory Standards (NCCLS),document M27-A. 2. C. neoformans cells were washed with normal saline at lowspeed centrifugation and diluted to the appropriate concentration in saline prior to use.The prophylactic and therapeutic role of chloroquine in the elimination of systemicinfection of C. neoformans in mice was evaluated. Each mouse was infected with C.neoformans. After 24 h of infection, each mouse was treated with a dose ofchloroquine for three consecutive days. Before 24 h of infection with C. neoformans,each mouse was pretreated with chloroquine and PS-liposomal chloroquine via anintraperitoneal route.RESULTS: 1. Chloroquine could inhibit or even kill C. neoformans in vitro athigh concentration, and capsule may reduce this effect. 2. Chloroquine may increase the antifungal effect of Amphoterecin B, Fluconazole and 5-Flucytosine in vitro. 3. Athigh concentration, Chloroquine could prevent cryptococcal infection to some extentin immunocompetent mice but not in immunocompromised mice. 4. Chloroquinecould treat cryptococcal infection both in immunocompetent and inimmunocompromised mice. 5. Chloroquine has good combination effect withfluconazole intreatent of mice cryptococcosis.CONCLUTIONS: Chloroquine should be a good choice for treatment ofcryprococcosis in human and be another alternatives for combination therapy. Theappropriate dosage and its mechanism still need to be explored.