Murine cathelicidin: as a host defensive response against Leishmania major infection

Therapeutic potential of antimicrobial peptides against pathogenic protozoa

Protozoal infections cause significant morbidity and mortality in humans and animals. The use of several antiprotozoal drugs is associated with serious adverse effects and resistance development, and drugs that are more effective are urgently needed. Microorganisms, mammalian cells and fluids, insects, and reptiles are sources of antimicrobial peptides (AMPs) that act against pathogenic microorganisms; these AMPs have been widely studied as a promising alternative therapeutic option to conventional antibiotics, aiming to treat infections caused by multidrug-resistant pathogens. One advantage of AMP molecules is their adaptability, as they can be easily fine-tuned for broad-spectrum or targeted activity by changing the amino acid residues in their sequence. Consequently, these variations in structural and physicochemical properties can alter the antimicrobial activities of AMPs and decrease resistance development. This article presents an overview of peptide activities against amebiasis, giardiasis, trichomoniasis, Chagas disease, leishmaniasis, malaria, and toxoplasmosis. AMPs and their analogs demonstrate great potential as therapeutics, with potent and selective activity, when compared with commercially available drugs, and hold the potential to act as new scaffolds for the development of novel anti-protozoal drugs.

Evaluation of the Efficacy of Amphotericin B and Terbinafine Microemulsions and Their Combination on Cutaneous Leishmaniasis and Comparison with the Conventional Drug Form in BALB/c Mice

Intracellular parasitic protozoa of Leishmania sp. causes leishmaniasis. The restricted access of the drugs to affected cells in the treatment of intracellular infections such as leishmaniasis is frequently hampered. Furthermore, most of today's drugs have limited uses due to some containing toxic compounds, and drug resistance is on the rise. In the present investigation, Amphotericin B (AmB) and Terbinafine (Tbf) were loaded in microemulsion (ME) in combination and alone, and the in vivo efficacy was considered in BALB/c mice infected with Leishmania major (L. major). The wound size at the base of the mouse tail was measured, and real-time PCR was performed to quantify the parasite load after the infection challenge. The study demonstrated that the ME-AmB and ME-Tbf formulations are safe and effective compounds for the treatment of cutaneous leishmaniasis by enhancing the effectiveness of AmB and Tbf in reducing the parasite burden.

Advancement in leishmaniasis diagnosis and therapeutics: An update

Leishmaniasis is regarded as a neglected tropical disease by World Health Organization (WHO) and is ranked next to malaria as the deadliest protozoan disease. The primary causative agents of the disease comprise of diverse leishmanial species sharing clinical features ranging from skin abrasions to lethal infection in the visceral organs. As several Leishmania species are involved in infection, the role of accurate diagnosis becomes pivotal in adding new dimensions to anti-leishmanial therapy. Diagnostic methods must be fast, reliable, easy to perform, highly sensitive, and specific to differentiate among similar parasitic diseases. Herein, we present the conventional and recent approaches impended for the disease diagnosis and their sensitivity, specificity, and clinical application in parasite detection. Furthermore, we have also elaborated various new methods to cure leishmaniasis, which include host-directed therapies, drug repurposing, nanotechnology, and combinational therapy. This review addresses novel techniques and innovations in leishmaniasis, which can aid in unraveling new strategies to fight against the deadly infection.

Determination of parasitic burden in the brain tissue of infected mice in acute toxoplasmosis after treatment by fluconazole combined with sulfadiazine and pyrimethamine

BACKGROUND/AIMS

One of the opportunistic pathogens which cause serious problems in the human immune system is Toxoplasma gondii, with toxoplasma encephalitis (TE) seen in patients affected by it. The treatment of these patients is limited, and if not treated on time, death will be possible.

METHODS

In this study, the effects of the treatment with different doses of fluconazole (FLZ) in combination with the current treatment of acute toxoplasmosis on reducing the mortality rate and the parasitic load in the murine model in vivo were studied. The mice were treated with different doses of fluconazole alone, sulfadiazine, and pyrimethamine plus fluconazole. A day after the end of the treatment and 1 day before death, the mice's brains were collected, and after DNA extraction and molecular tests, the parasite burden was detected.

RESULTS

This study showed that a 10-day treatment with 20 mg/kg of fluconazole combined with sulfadiazine and pyrimethamine 1.40 mg/kg per day affected acute toxoplasmosis and reduced the parasitic load significantly in brain tissues and also increased the survival rate of all mice in this group until the last day of the study, in contrast to other treatment groups. These results also indicate the positive effects of combined therapy on Toxoplasma gondii and the prevention of relapse.

CONCLUSIONS

Reducing the parasitic burden and increasing the survival rate were more effective against acute toxoplasmosis in the combined treatment of different doses of fluconazole with current treatments than current treatments without fluconazole. In other words, combination therapy with fluconazole plus pyrimethamine reduced the parasitic burden in the brain significantly, so it could be a replacement therapy in patients with intolerance sulfadiazine.

Mechanistic Insights into the Leishmanicidal and Bactericidal Activities of Batroxicidin, a Cathelicidin-Related Peptide from a South American Viper (Bothrops atrox)

Snake venoms are important sources of bioactive molecules, including those with antiparasitic activity. Cathelicidins form a class of such molecules, which are produced by a variety of organisms. Batroxicidin (BatxC) is a cathelicidin found in the venom of the common lancehead (Bothrops atrox). In the present work, BatxC and two synthetic analogues, BatxC(C-2.15Phe) and BatxC(C-2.14Phe)des-Phe1, were assessed for their microbicidal activity. All three peptides showed a broad-spectrum activity on Gram-positive and -negative bacteria, as well as promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. Circular dichroism (CD) and nuclear magnetic resonance (NMR) data indicated that the three peptides changed their structure upon interaction with membranes. Biomimetic membrane model studies demonstrated that the peptides exert a permeabilization effect in prokaryotic membranes, leading to cell morphology distortion, which was confirmed by atomic force microscopy (AFM). The molecules considered in this work exhibited bactericidal and leishmanicidal activity at low concentrations, with the AFM data suggesting membrane pore formation as their mechanism of action. These peptides stand as valuable prototype drugs to be further investigated and eventually used to treat bacterial and protozoal infections.

Immunological role of keratinocytes in leishmaniasis

Following inoculation of Leishmania, a protozoan parasite, into the skin of a mammal, the epidermal keratinocytes recognize the parasite and influence the local immune response that can give rise to different outcomes of leishmaniasis. The early keratinocyte-derived cytokines and keratinocytes-T cells interactions shape the anti-leishmanial immune responses that contribute to the resistance or susceptibility to leishmaniasis. The keratinocyte-derived cytokines can directly potentiate the leishmanicidal activity of monocytes and macrophages. As keratinocytes express MHC-II and enhance the expression of costimulatory molecules, these cells act as antigen-presenting cells (APCs) in cutaneous leishmaniasis (CL). Depending on the epidermal microenvironment, the keratinocytes induce various types of effector CD4⁺ T cells. Keratinocyte apoptosis and necrosis have been also implicated in ulceration in CL. Further, keratinocytes contribute to the healing of Leishmania-related cutaneous wounds. However, keratinocyte-derived IL-10 may play a key role in the development of post-kala-azar dermal leishmaniasis (PKDL). In this review, a comprehensive discussion regarding the multiple roles played by keratinocytes during leishmaniasis was provided, while highlighting novel insights concerning the immunological and pathological roles of these cells.

Nano amphotericin B: a good anti-leishmanial drug with effect on cathelicidin gene expression

Protozoan parasites, such as Leishmania major (L. major), remained as a global health problem of the current century. Leishmania major is a major cause of cutaneous leishmaniasis (CL) in developed and developing countries. Traditionally, amphotericin B is prescribed as an alternative drug, while first-line drugs failed. Some active proteins of the innate immune system such as cathelicidins try to inhibit infection Via several proposed mechanisms. Here this research aimed to not only determine the anti-leishmanial activity of nano amphotericin B but also to evaluate which anti-leishmanial drug can induce the cathelicidin gene expression. Both promastigote and amastigote stages of L. major were exposed to various concentrations of nano amphotericin B, amphotericin B and finally compared to glucan time as standard drug for CL treatment. For the gene expression of cathelicidin, macrophages were exposed to the same concentration of anti-leishmanial drugs. The findings demonstrated that nano amphotericin B was more effective at all concentrations than amphotericin B. Additionally, among tested anti-leishmanial drugs, nano amphotericin B has more potency to induce the cathelicidin gene expression in macrophages cells. The findings revealed that nano amphotericin B has potential as an effective anti-leishmanial drug against CL caused by L. major parasites.