Photochemotherapeutic Strategy against Acanthamoeba Infections

Khan

2017

Microbial Pathogenesis

Self Cite

181

121

Microbial keratitis is a sight-threatening ocular infection caused by bacteria, fungi, and protist pathogens. Epithelial defects and injuries are key predisposing factors making the eye susceptible to corneal pathogens. Among bacterial pathogens, the most common agents responsible for keratitis include Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumonia and Serratia species. Fungal agents of corneal infections include both filamentous as well as yeast, including Fusarium, Aspergillus, Phaeohyphomycetes, Curvularia, Paecilomyces, Scedosporium and Candida species, while in protists, Acanthamoeba spp. are responsible for causing ocular disease. Clinical features include redness, pain, tearing, blur vision and inflammation but symptoms vary depending on the causative agent. The underlying molecular mechanisms associated with microbial pathogenesis include virulence factors as well as the host factors that aid in the progression of keratitis, resulting in damage to the ocular tissue. The treatment therefore should focus not only on the elimination of the culprit but also on the neutralization of virulence factors to minimize the damage, in addition to repairing the damaged tissue. A complete understanding of the pathogenesis of microbial keratitis will lead to the rational development of therapeutic interventions. This is a timely review of our current understanding of the advances made in this field in a comprehensible manner. Coupled with the recently available genome sequence information and high throughput genomics technology, and the availability of innovative approaches, this will stimulate interest in this field.

Section: Treatmentmentioning

confidence: 99%

Pathogenesis of microbial keratitis

Lakhundi

Khan

2017

Microbial Pathogenesis

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181

121

“…A keratitis isolate of A. castellanii belonging to the T4 genotype was purchased from the American Type Culture Collection (ATCC 50492). Amoebae were routinely grown in 10 ml PYG medium (0.75% [wt/vol] (13). The medium was changed 18 h before the experiment, and amoebae adherent to the flask, representing the trophozoite form, were collected by placing it on ice for 20 min with gentle agitation and used in all experiments.…”

Section: Methodsmentioning

confidence: 99%

“…In order to determine the morphology of nanoparticles, atomic force microscopic analysis was performed as described previously but with slight modifications (13). Briefly, a cover glass of 18-mm diameter was rinsed in distilled water, followed by three washes in 70% ethanol.…”

Section: Methodsmentioning

confidence: 99%

Gold Nanoparticle Conjugation Enhances the Antiacanthamoebic Effects of Chlorhexidine

Aqeel

Antimicrob Agents Chemother

Anwar

et al. 2016

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Acanthamoeba keratitis is a serious infection with blinding consequences and often associated with contact lens wear. Early diagnosis, followed by aggressive topical application of drugs, is a prerequisite in successful treatment, but even then prognosis remains poor. Several drugs have shown promise, including chlorhexidine gluconate; however, host cell toxicity at physiologically relevant concentrations remains a challenge. Nanoparticles, subcolloidal structures ranging in size from 10 to 100 nm, are effective drug carriers for enhancing drug potency. The overall aim of the present study was to determine whether conjugation with gold nanoparticles enhances the antiacanthamoebic potential of chlorhexidine. Gold-conjugated chlorhexidine nanoparticles were synthesized. Briefly, gold solution was mixed with chlorhexidine and reduced by adding sodium borohydride, resulting in an intense deep red color, indicative of colloidal gold-conjugated chlorhexidine nanoparticles. The synthesis was confirmed using UV-visible spectrophotometry that shows a plasmon resonance peak of 500 to 550 nm, indicative of gold nanoparticles. Further characterization using matrix-assisted laser desorption ionization-mass spectrometry showed a goldconjugated chlorhexidine complex at m/z 699 ranging in size from 20 to 100 nm, as determined using atomic force microscopy. To determine the amoebicidal and amoebistatic effects, amoebae were incubated with gold-conjugated chlorhexidine nanoparticles. For controls, amoebae also were incubated with gold and silver nanoparticles alone, chlorhexidine alone, neomycin-conjugated nanoparticles, and neomycin alone. The findings showed that gold-conjugated chlorhexidine nanoparticles exhibited significant amoebicidal and amoebistatic effects at 5 M. Amoebicidal effects were observed by parasite viability testing using a Trypan blue exclusion assay and flow-cytometric analysis using propidium iodide, while amoebistatic effects were observed using growth assays. In contrast, chlorhexidine alone, at a similar concentration, showed limited effects. Notably, neomycin alone or conjugated with nanoparticles did not show amoebicidal or amoebistatic effects. Pretreatment of A. castellanii with goldconjugated chlorhexidine nanoparticles reduced amoeba-mediated host cell cytotoxicity from 90% to 40% at 5 M. In contrast, chlorhexidine alone, at similar concentrations, had no protective effects for the host cells. Similarly, amoebae treated with neomycin alone or neomycin-conjugated nanoparticles showed no protective effects. Overall, these findings suggest that gold-conjugated chlorhexidine nanoparticles hold promise in the improved treatment of A. castellanii keratitis.

“…Additionally, the effects of these compounds are often amoebistatic, rather than amoebicidal (65); hence, prolonged clinical application is needed, which could result in the emergence of drugresistant strains, as seen in yeast such as Candida albicans, where azole resistance emerging through increased function of efflux mechanisms or through changes in the azole targets, e.g., C14 demethylase, or through changes in the biosynthetic steps of ergosterol synthesis has been observed. Similar mechanisms may explain variations in antimicrobial sensitivity among various isolates of Acanthamoeba (66). Overall, the ergosterol biosynthesis pathway is a potential target in the rational development of targeted therapeutic interventions against Acanthamoeba, as long as specificity is achieved to optimize the antiparasitic effects.…”

mentioning

confidence: 96%

“…Although rMBP is not applicable as a vaccine tool given the rarity of the disease, these findings have highlighted MBP as an important chemotherapeutic target. For example, recent studies showed that MBP-targeted chemotherapy can effectively eradicate amoebae in vitro and protect host cells against amoeba-mediated damage (66). Although studies are needed to prove the value of this approach in vivo, it has been suggested that mannose-conjugated porphyrin may have an application for targeted photodynamic chemotherapy against Acanthamoeba infections and should be explored for potential clinical applications in future investigations (66).…”

mentioning

confidence: 99%

The Development of Drugs against Acanthamoeba Infections

Antimicrob Agents Chemother

Aqeel

Khan

2016

Self Cite

For the past several decades, there has been little improvement in the morbidity and mortality associated with Acanthamoeba keratitis and Acanthamoeba encephalitis, respectively. The discovery of a plethora of antiacanthamoebic compounds has not yielded effective marketed chemotherapeutics. The rate of development of novel antiacanthamoebic chemotherapies of translational value and the lack of interest of the pharmaceutical industry in developing such chemotherapies have been disappointing. On the other hand, the market for contact lenses/contact lens disinfectants is a multi-billion-dollar industry and has been successful and profitable. A better understanding of drugs, their targets, and mechanisms of action will facilitate the development of more-effective chemotherapies. Here, we review the progress toward phenotypic drug discovery, emphasizing the shortcomings of useable therapies.