Topical fumagillin in the treatment of microsporidial keratoconjunctivitis in AIDS

Past, present, and prospects in microsporidial keratoconjunctivitis- A review

Ocular microsporidiosis comprises two entirely different spectra of disease as keratoconjunctivitis and stromal keratitis. Microsporidial keratoconjunctivitis (MKC) has been increasingly reported in the past two decades, probably due to raised awareness, simpler diagnostic procedures, and a better understanding of the clinical presentation. It is characterized by the presence of raised, coarse, punctate, multifocal, round to oval, greyish-white corneal epithelial lesions which usually evolve into nummular scars before resolution. Conjunctivitis seen is non-purulent and of mild-moderate intensity, with mixed papillary-follicular reaction. The mode of transmission and pathogenesis is poorly understood. Despite lack of inflammatory response, uncommon associations reported were- endotheliitis, corneal edema, limbitis, uveitis, and sub-epithelial infiltrates. There has been no consensus on the management of MKC. It varies from the use of multiple antimicrobial agents to simple lubricants. The majority of the disease goes underdiagnosed or misdiagnosed and treated as adenoviral keratoconjunctivitis, with topical steroids or anti-virals empirically. Changing trends have been noticed in the pattern of infection, possibly with increasing evidence of Vittaforma corneae as causative organisms, previously reported to cause stromal keratitis. An elaborate review of the past and present literature on MKC is provided in this review article, along with gaps in knowledge, and future directions of research.

Stromal microsporidial keratitis successfully treated with medical therapy

Purpose

To report a case of severe stromal microsporidal keratitis successfully treated with oral albendazole and topical voriconazole.

Observations

A 71-year-old man presented with progressive vision loss and corneal opacification for one year. Initial visual acuity was counting fingers attributed to a dense subepithelial opacification. Confocal microscopy and subsequent corneal biopsy lead to the diagnosis of microsporidial keratitis. The patient completed a four-week course of oral albendazole and topical voriconazole which resulted in resolution of the corneal opacification and improvement in visual acuity to 20/250.

Conclusions and Importance

A four-week course of oral albendazole and topical voriconazole was an effective treatment for severe stromal microsporidial keratitis.

MetAP2 inhibition reduces food intake and body weight in a ciliopathy mouse model of obesity

The ciliopathies Bardet-Biedl syndrome and Alström syndrome are genetically inherited pleiotropic disorders with hyperphagia and obesity as primary clinical features. Methionine aminopeptidase 2 inhibitors (MetAP2i) have been shown in preclinical and clinical studies to reduce food intake, body weight, and adiposity. Here, we investigated the effects of MetAP2i administration in a mouse model of ciliopathy produced by conditional deletion of the Thm1 gene in adulthood. Thm1 conditional knockout (cko) mice showed decreased hypothalamic proopiomelanocortin expression as well as hyperphagia, obesity, metabolic disease, and hepatic steatosis. In obese Thm1-cko mice, 2-week administration of MetAP2i reduced daily food intake and reduced body weight 17.1% from baseline (vs. 5% reduction for vehicle). This was accompanied by decreased levels of blood glucose, insulin, and leptin. Further, MetAP2i reduced gonadal adipose depots and adipocyte size and improved liver morphology. This is the first report to our knowledge of MetAP2i reducing hyperphagia and body weight and ameliorating metabolic indices in a mouse model of ciliopathy. These results support further investigation of MetAP2 inhibition as a potential therapeutic strategy for ciliary-mediated forms of obesity.

Outbreak of microsporidial keratoconjunctivitis with rugby sport due to soil exposure

AIMS

To investigate a cluster of microsporidial keratoconjunctivitis in 33 eyes of 25 previously healthy paediatric and teenage individuals after a rugby match.

METHODS

An observational case series was reported. Analysis of medical record of patients with microsporidial keratoconjunctivitis, who presented within May 2012, was performed. All patients were treated by a single ophthalmologist with a standardized topical regime, including a fluoroquinolone (moxifloxacin) and an antiseptic (Brolene or Desomedine). Five eyes received corneal scrapings.

RESULTS

The mean age was 13.36 years (range 5-16). All patients have participated in a rugby match on 21-22 April 2012. The onset of symptoms ranged from 10 to 30 days post exposure. All eyes had multiple superficial coarse punctate keratitis. Four (12%) eyes presented with keratic precipitates. One (3%) eye had intraocular pressure of 27 mm Hg. Microscopic examination of corneal scrapings with modified trichrome or calcofluor white (CFW) fluorescent staining was unremarkable but subsequent PCR test was positive for the small subunit rRNA gene of Vittaforma corneae in three out of five eyes. Sequencing of the PCR product of 1150 bp showed 96-100% identity with the Indian or Singaporean strains of V. corneae. After treatment, all eyes healed without sequel.

CONCLUSIONS

The first outbreak of microsporidial keratoconjunctivitis in paediatric and teenage individuals with a rugby match is reported. A standardized topical regime, including a fluoroquinolone (moxifloxacin) and an antiseptic (Brolene or Desomedine), seems to be safe and effective, and requires validation in future treatment trials.

Treatment of microsporidial keratoconjunctivitis with repeated corneal swabbing

PURPOSE

To report the effect of repeated corneal swabbing in patients with microsporidial keratoconjunctivitis.

DESIGN

Retrospective noncomparative case series.

METHODS

Sixteen eyes of 14 healthy patients with microsporidial keratoconjunctivitis were diagnosed based on the detection of microsporidia in corneal scrapings using Gram stain, the modified Kinyoun acid-fast stain, or both. Polymerase chain reaction plus gene analysis of the microsporidian 16S ribosomal RNA had been performed in 10 patients who sought treatment between 2010 and 2011. Some of the lesions were scraped for procurement of specimens. The remaining lesions were wiped off gently by cotton swabs. Repeated swabbing was performed if infection persisted or new lesions were observed at follow-up. To prevent secondary bacterial infection, 0.3% norfloxacin or 0.25 % chloramphenicol were prescribed.

RESULTS

The mean age was 52.2 years. All patients had the characteristic disseminated, punctate, slightly elevated, white epithelial lesions. The denser white lesions could be removed easily after gentle swabbing, and most epithelium remained intact. The 10 cases with positive polymerase chain reaction results were all identified to be Vittaforma corneae. The mean number of corneal swabbing was 3.3, and the mean disease resolution time was 6.6 days. No patients had recurrence or loss of visual acuity at last follow-up.

CONCLUSIONS

Repeated swabbing effectively can eradicate corneal epithelial microsporidial lesions in approximately 1 week. It is easy to perform, less painful, and more acceptable for the patients.

Fumagillin reduces adipose tissue formation in murine models of nutritionally induced obesity

The effect of fumagillin (a methionine aminopeptidase-type 2 (Met-AP2) inhibitor, with antiangiogenic properties) was investigated in murine models of diet-induced obesity. Eleven-week-old male C57Bl/6 mice (group 1) were given fumagillin by oral gavage at a dose of 1 mg/kg/day during 4 weeks while fed a high-fat diet (HFD) (20.1 kJ/g), and control mice (group 2) received solvent and were pair-fed. At the end of the experiment, body weights in group 1 were significantly lower as compared to group 2 (P < 0.0005). The subcutaneous (SC) and gonadal (GON) fat mass was also significantly lower in group 1 (P < 0.005 and P < 0.05, respectively). Adipocytes were smaller in adipose tissues of mice in group 1, associated with higher adipocyte density. Blood vessel density normalized to adipocyte density was lower in group 1 adipose tissues. However, in mice with established obesity monitored to maintain the same body weight and fat mass as controls, short-term fumagillin administration was also associated with adipocyte hypotrophy (P = 0.01) without affecting blood vessel size or density. Thus, treatment with fumagillin impaired diet-induced obesity in mice, associated with adipocyte hypotrophy but without marked effect on adipose tissue angiogenesis.

Testing intra-hemocelic injection of antimicrobials against Encephalitozoon sp. (Microsporidia) in an insect host

Encephalitozoon spp. are the primary microsporidial pathogens of humans and domesticated animals. In this experiment, we test the efficacy of four commercial antimicrobials against an Encephalitozoon sp. in an insect host by intra-hemocelic injection. All four antimicrobials, viz., thiabendazole, quinine, albendazole, and fumagillin, significantly reduced but did not eliminate microsporidia spore counts in the grasshopper host. Among these four drugs, thiabendazole was most effective in reducing the microsporidia spore level up to 90%, followed by quinine (70%), albendazole (62%), and fumagillin (59%). No control or quinine-treated animals died, whereas 45% of albendazole animals died. Despite the high mortality induced by albendazole, this drug significantly reduced spore counts, a result not seen in previous per os trials. Among the treatment groups, grasshoppers injected with thiabendazole lost a significant mass. Our study suggests that quinine and related alkaloids should be further examined for antimicrosporidial activity.

Effect of four antimicrobials against an Encephalitozoon sp. (Microsporidia) in a grasshopper host

Encephalitozoon spp. are the primary microsporidial pathogens of humans and domesticated animals. In this experiment, we test the efficacy of 4 commercial antimicrobials against an Encephalitozoon sp. infecting a grasshopper (Romalea microptera) host. Oral treatment with fumagillin or thiabendazole significantly reduced pathogen spore counts (93% and 88% respectively), whereas spore counts of grasshoppers fed quinine produced a non-significant 53% reduction in spores, and those fed streptomycin a non-significant 29% increase in spores, compared to the control. We observed a moderate dose-response effect for thiabendazole, whereby spore count decreased as drug consumption increased. No thiabendazole-treated animals died, whereas 27% of streptomycin-treated animals died, suggesting that thiabendazole was not toxic at the doses administered. The deaths among streptomycin-treated animals may have been caused by drug toxicity, parasite burden, or both. Although fumagillin and thiabendazole significantly reduced spore counts, in no individual was the pathogen totally eliminated. Our data confirm that microsporidia are difficult to control and that fumagillin and thiabendazole are partially effective antimicrobials against this group. Our study suggests that quinine and related alkaloids should be further examined for antimicrosporidial activity, and streptomycin should be examined as a possible enhancer of microsporidiosis.

Anterior Segment and External Ocular Disorders Associated with Human Immunodeficiency Virus Disease

The eye is a common site for complications of human immunodeficiency virus (HIV) infection. Although cytomegalovirus retinitis remains the most prevalent of the blinding ocular disorders that can occur in individuals with the acquired immunodeficiency syndrome (AIDS), several important HIV-associated disorders may involve the anterior segment, ocular surface, and adnexae. Some of these entities, such as Kaposi sarcoma, were well described, but uncommon, before the HIV epidemic. Others, like microsporidial keratoconjunctivitis, have presentations that differ between affected individuals with HIV disease and those from the general population who are immunocompetent. The treatment of many of these diseases is challenging because of host immunodeficiency. Survival after the diagnosis of AIDS has increased among individuals with HIV disease because of more effective antiretroviral therapies and improved prophylaxis against, and treatment of, opportunistic infections. This longer survival may lead to an increased prevalence of anterior segment and external ocular disorders. In addition, the evaluation and management of disorders such as blepharitis and dry eye, which were previously overshadowed by more severe, blinding disorders, may demand increased attention, as the general health of this population improves. Not all individuals infected with HIV receive potent antiretroviral therapy, however, because of socioeconomic or other factors, and others will be intolerant of these drugs or experience drug failure. Ophthalmologists must, therefore, still be aware of the ocular findings that develop in the setting of severe immunosuppression. This article reviews the spectrum of HIV-associated anterior segment and external ocular disorders, with recommendations for their evaluation and management.

Therapeutic strategies for human microsporidia infections

Over the past 20 years, microsporidia have emerged as a cause of infectious diseases in AIDS patients, organ transplant recipients, children, travelers, contact lens wearers and the elderly. Enterocytozoon bieneusi and the Encephalitozoon spp., Encephalitozoon cuniculi, Encephalitozoon hellem and Encephalitozoon intestinalis, are the most frequently identified microsporidia in humans, and are associated with diarrhea and systemic disease. The microsporidia are small, single-celled, obligately intracellular parasites that have been identified in water sources, as well as in wild, domestic and food-producing farm animals, thereby raising concerns for waterborne, foodborne and zoonotic transmission. Current therapies for microsporidiosis include albendazole, a benzimidazole that inhibits microtubule assembly and is effective against several microsporidia, including the Encephalitozoon spp., although it is less effective against Encephalitozoon bieneusi. Fumagillin, an antibiotic and antiangiogenic compound produced by Aspergillus fumigatus, is more broadly effective against Encephalitozoon spp. and E. bieneusi; however, is toxic when administered systemically to mammals. Recent studies are also focusing on compounds that target the microsporidia polyamines (e.g., polyamine analogs), methionine aminopeptidase 2 (e.g., fumagillin-related compounds), chitin inhibitors (e.g., nikkomycins), topoisomerases (e.g., fluoroquinolones) and tubulin (e.g., benzimidazole-related compounds).

Bilateral microsporidial keratoconjunctivitis in an immunocompetent non-contact lens wearer

PURPOSE

To describe an immunocompetent male with bilateral microsporidial keratoconjunctivitis who responded to treatment with albendazole, propamidine, and fumagillin.

METHODS

Corneal and conjunctival epithelial scrapings from a man with bilateral keratoconjunctivitis previously treated with topical corticosteroids were evaluated by Gram stain and by fluorescence microscopy.

RESULTS

Gram stain and fluorescence microscopy of corneal epithelial scraping revealed organisms characteristic of microsporidia. Results of human immunodeficiency virus antibody testing were reported as nonreactive. Symptoms of ocular discomfort and clinical signs of keratoconjunctivitis resolved after five weeks of treatment that included systemic albendazole and topical propamidine isethionate 0.1% and fumagillin bicyclohexylammonium salt. A follow-up conjunctival scraping failed to detect any residual organisms 2 weeks after cessation of all treatment.

CONCLUSION

Microsporidial ocular infection occurred in an immunocompetent non-contact lens wearer. Microsporidial keratoconjunctivitis should be considered in any individual with atypical multifocal diffuse epithelial keratitis, regardless of immune status or recent history of contact lens wear.

Ocular manifestations of HIV infection

Ophthalmic abnormalities are common in HIV-infected patients. Serious ophthalmic diseases often result from opportunistic infections and can cause blindness in the absence of prompt diagnosis and therapy. We review recent advances in the diagnosis and management of HIV-associated ocular disease, including cytomegalovirus retinitis, the leading cause of vision loss in HIV-infected patients. The widespread use of highly active antiretroviral therapy (HAART) over the past 3 years has reduced the morbidity and mortality associated with HIV infection. HAART has dramatically altered the incidence and natural history of many opportunistic infections, and we discuss the impact of HAART on ophthalmic disease.

Cryptosporidia and microsporidia--waterborne diseases in the immunocompromised host

Cryptosporidia and microsporidia are emerging parasitic pathogens in immunocompetent and immunocompromised individuals. Cryptosporidium infects several wild and domestic animals that excrete oocysts into the environment and contaminated water represents the major source of infection for humans. Waterborne transmission of Cryptosporidium is a major risk for humans and appropriate measures have to be taken to protect immunocompetent and immunocompromised individuals to become infected. For microsporidia, the sources and ways of transmission are not well documented. Although several animal hosts have been identified recently, the relevant reservoirs of human microsporidia are still unknown. Also, the routes of spreading are unknown. Is microsporidiosis a zoonotic disease that will be transmitted through close contact with infected animals or is contaminated surface water responsible for transmission and represents a relevant reservoir? This review is designed to give information on these two emerging intestinal parasites in a format that will be useful to clinical microbiologists, physicians interested in infectious diseases, and public health personnel.

Molecular techniques for detection, species differentiation, and phylogenetic analysis of microsporidia

Microsporidia are obligate intracellular protozoan parasites that infect a broad range of vertebrates and invertebrates. These parasites are now recognized as one of the most common pathogens in human immunodeficiency virus-infected patients. For most patients with infectious diseases, microbiological isolation and identification techniques offer the most rapid and specific determination of the etiologic agent. This is not a suitable procedure for microsporidia, which are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Although the diagnosis of microsporidiosis and identification of microsporidia by light microscopy have greatly improved during the last few years, species differentiation by these techniques is usually impossible and transmission electron microscopy may be necessary. Immunfluorescent-staining techniques have been developed for species differentiation of microsporidia, but the antibodies used in these procedures are available only at research laboratories at present. During the last 10 years, the detection of infectious disease agents has begun to include the use of nucleic acid-based technologies. Diagnosis of infection caused by parasitic organisms is the last field of clinical microbiology to incorporate these techniques and molecular techniques (e.g., PCR and hybridization assays) have recently been developed for the detection, species differentiation, and phylogenetic analysis of microsporidia. In this paper we review human microsporidial infections and describe and discuss these newly developed molecular techniques.

Effects of albendazole, fumagillin, and TNP-470 on microsporidial replication in vitro

Presently, the two most commonly used drugs for treating microsporidiosis in persons with AIDS are albendazole and fumagillin. Albendazole is effective for treating disseminated infections due to Encephalitozoon spp. but is variably effective against Enterocytozoon bieneusi infections. Fumagillin is highly effective when used topically to treat ocular infections with Encephalitozoon hellem or Encephalitozoon intestinalis but is too toxic for systemic use. In this study, the fumagillin analog TNP-470 was assayed for antimicrosporidial activity in vitro. The MICs of TNP-470 at which 50% of isolates were killed (MIC50s) were 0.35 +/- 0.21 and 0.38 +/- 0.11 ng/ml for E. intestinalis and Vittaforma corneae, respectively, and were similar to the MIC50s of fumagillin for these organisms, which were 0.515 +/- 0.002 and 0.81 +/- 0.014 ng/ml, respectively. The MIC50 of albendazole for E. intestinalis was 8.0 +/- 4.23 ng/ml, significantly less (P < 0.01) than its MIC50 for V. corneae, which was 55.0 +/- 7.07 ng/ml. TNP-470 inhibited replication of E. intestinalis in RK-13 cells if it was given at the same time as infection or if treatment was initiated 7 days later. In addition, treatment of the infected cultures with TNP-470 at a dose of 10 ng/ml for 2 weeks, followed by discontinuation of the drug treatment, resulted in no significant increase in E. intestinalis shedding during the following 3 weeks in culture. Because TNP-470 acts against both E. intestinalis and V. corneae, and because TNP-470 was found by others to be less toxic in vivo, TNP-470 may be a promising new drug for the treatment of microsporidiosis.

Use of a fluorescent probe to assess the activities of candidate agents against intracellular forms of Encephalitozoon microsporidia

Microsporidia are obligate intracellular protozoan parasites. Three species of the genus Encephalitozoon are among the microsporidia that infect immunodeficient humans. These species, Encephalitozoon cuniculi, Encephalitozoon hellem, and Encephalitozoon intestinalis, all develop in a parasitophorous vacuole within a host cell. The present study describes a method that uses the fluorescent probe calcein and confocal microscopy to detect drug-induced effects in Encephalitozoon-infected green monkey kidney cells. The effects were as follows: (i) changes in parasite organization within the parasitophorous vacuole; (ii) swelling and gross morphological changes of parasite developing stages in situ; (iii) killing of developing parasite stages in situ, detected by their uptake of the fluorescent probe; and (iv) reduction in the viability of the host cell population, assessed by the loss of the probe. Verapamil and itraconazole were used to increase the vital dye loading by both uninfected and infected cells. Agents with known antimicrosporidial activity, albendazole and fumagillin, caused all three types of parasite changes at concentrations that had no detectable effect on host cell viability. The effective doses of albendazole and fumagillin that caused swelling and disorganization of parasite developing stages were 5 x 10(-7) and 10(-6) M respectively. Killing of developing stages was detected at 10-fold-higher concentrations for these agents and at 10(-5) M for metronidazole. This method can be used to screen candidate antimicrosporidial agents in infected cultured cells.