Synergistic action of lactoferrin and its derived functional fragments as a promising therapeutic agent in combating mucormycosis

Abstract

Aim: Currently, we have limited armamentarium of antifungal agents against Mucorales. There is an urgent need to discover novel antifungal agents that are effective, safe and affordable. Materials & methods: In this study, the anti-Mucorale action of native lactoferrin (LF) and its functional fragments CLF, RR6 and LFcin against three common Mucorale species are reported. The synergistic action of LF with antifungal agents like amphotericin B, isavuconazole and posaconazole was analyzed using checkerboard technique. Results: All the three mucor species showed inhibition when treated with fragments. The checkerboard assay confirmed that native LF showed the best synergistic action against Mucorales in combination with Amphotericin B. Conclusion: These results highlight the potential therapeutic value of native LF against Mucorales.

Plain language summary

Black fungus, or ‘mucormycosis’, is a dangerous fungal infection. Normally, it affects people with a weakened immune system. It is only treatable when diagnosed early. It spreads by breathing the fungus in, eating contaminated food or direct contact with an infected wound. There are not many medicines that can treat this type of fungus, so it is important to find new ones. In this study, we tested a natural protein called lactoferrin and some of its building blocks, called peptides, to see if they could stop the fungus from growing. Lactoferrin and its peptides could stop the fungus from growing, especially when used with a medicine called amphotericin B. This means that lactoferrin could potentially be a helpful treatment for this fungal infection.

Article highlights

Topic

• Mucormycosis, a rare but serious infection, is caused by the fungi of the order Mucorales. These fungi are spore-forming common bread mold and are abundantly present in environment.

• Despite treatment, the mortality rate for mucormycosis remains higher than 50%. Therefore, it is imperative to explore other safe and effective treatment options.

• In the past scenario, it has been seen that natural antifungal innate immunity proteins and their derived peptides are extremely effective in the therapeutics of aggressive fungi.

• They display various advantages over the classic antifungal compounds as they display strong activity coupled with effective tissue diffusion, low resistance for the future emerging strains, no toxicity against the human cell and stability across a wide range of temperatures.

• Lactoferrin (LF) is an antimicrobial glycoprotein that is found in most of the mammalian exocrine secretions.

• In the present study, we have explored the anti-Mucorale action of LF, its peptides RR-6, Lfcin and CLF prepared from trypsin hydrolysis.

Results

• Lactoferrin had the lowest MIC of 16 μg/ml against R. arrhizus and R. microsporus.

• Whereas Peptide LFcin was observed to inhibit the fungal growth at a concentration of 32 μg/ml, followed by peptide RR6 with MIC value of 125 μg/ml.

• However, C-lobe of lactoferrin exhibited least activity, with MICs 500 μg/ml with 50% inhibition against all isolates.

• Lactoferrin and amphotericin B showed synergy against R. arrhizus (FIC = 0.281), R. microspores (FICI = 0.375) and additive for R. homothallicus (FICI = 0.55).

Conclusion

• Based on the fungicidal mechanism of lactoferrin and amphotericin B and the results of this study, this combination possesses synergistic potential.

Keywords: :

• amphotericin-B
• black fungus
• LF
• LFcin
• Mucor

Financial disclosure

This study was supported by the Department of Science and Technology, Ministry of Science and Technology, India, Science and Engineering Research Board (SERB-13). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Competing interests disclosure

The authors have no competing interests or relevant affiliations with any organization or entity with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Writing disclosure

No writing assistance was utilized in the production of this manuscript.

Additional information

Funding

This study was supported by the Department of Science and Technology, Ministry of Science and Technology, India, Science and Engineering Research Board (SERB-13).