Fungal disease in the immunocompromised host

COVID-19-Associated Mucormycosis: A Matter of Concern Amid the SARS-CoV-2 Pandemic

Mucormycosis is an invasive fungal infection caused by fungi belonging to order Mucorales. Recently, with the increase in COVID-19 infections, mucormycosis infections have become a matter of concern globally, because of the high morbidity and mortality rates associated with them. Due to the association of mucormycosis with COVID-19 disease, it has been termed COVID-19-associated mucormycosis (CAM). In the present review, we focus on mucormycosis incidence, pathophysiology, risk factors, immune dysfunction, interactions of Mucorales with endothelial cells, and the possible role of iron in Mucorales growth. We review the limitations associated with current diagnostic procedures and the requirement for more specific, cost-effective, convenient, and sensitive assays, such as PCR-based assays and monoclonal antibody-based assays for the effective diagnosis of mucormycosis. We discuss the current treatment options involving antifungal drug therapies, adjunctive therapy, surgical treatment, and their limitations. We also review the importance of nutraceuticals-based therapy for the prevention as well as treatment of mucormycosis. Our review also highlights the need to explore the potential of novel immunotherapeutics, which include antibody-based therapy, cytokine-based therapy, and combination/synergistic antifungal therapy, as treatment options for mucormycosis. In summary, this review provides a complete overview of COVID-19-associated mucormycosis, addressing the current research gaps and future developments required in the field.

Peptide derived from anti-idiotypic single-chain antibody is a potent antifungal agent compared to its parent fungicide HM-1 killer toxin peptide

Based on anti-idiotypic network theory in light of the need for new antifungal drugs, we attempted to identify biologically active fragments from HM-1 yeast killer toxin and its anti-idiotypic antibody and to compare their potency as an antifungal agent. Thirteen overlapping peptides from HM-1 killer toxin and six peptides from its anti-idiotypic single-chain variable fragment (scFv) antibodies representing the complementarity determining regions were synthesized. The binding affinities of these peptides were investigated and measured by Dot blot and surface plasmon resonance analysis and finally their antifungal activities were investigated by inhibition of growth, colony forming unit assay. Peptide P6, containing the potential active site of HM-1 was highly capable of inhibiting the growth of Saccharomyces cerevisiae but was less effective on pathogenic fungi. However, peptide fragments derived from scFv antibody exerted remarkable inhibitory effect on the growth of pathogenic strains of Candida and Cryptococcus species in vitro. One scFv-derived decapeptide (SP6) was selected as the strongest killer peptide for its high binding affinity and antifungal abilities on both Candida and Cryptococcus species with IC(50) values from 2.33 × 10(-7) M to 36.0 × 10(-7) M. SP6 peptide activity was neutralized by laminarin, a β-1,3-glucan molecule, indicating this peptide derived from scFv anti-idiotypic antibody retains antifungal activity through interaction with cell wall β-glucan of their target fungal cells. Experimental evidence strongly suggested the possibility of development of anti-idiotypic scFv peptide-based antifungal agents which may lead to improve therapeutics for the management of varieties of fungal infections.

An improved phage-display panning method to produce an HM-1 killer toxin anti-idiotypic antibody

BACKGROUND

Phage-display panning is an integral part of biomedical research. Regular panning methods are sometimes complicated by inefficient detachment of the captured phages from the antigen-coated solid supports, which prompted us to modify. Here, we produce an efficient antigen-specific single chain fragment variable (scFv) antibody by using a target-related molecule that favored selection of recombinant antibodies.

RESULTS

To produce more selective and specific anti-idiotypic scFv-antibodies from a cDNA library, constructed from HM-1 killer toxin (HM-1)-neutralizing monoclonal antibodies (nmAb-KT), the method was modified by using an elution buffer supplemented with HM-1 that shares structural and functional similarities with the active site of the scFv antibody. Competitive binding of HM-1 to nmAb-KT allowed easy and quick dissociation of scFv-displayed phages from immobilized nmAb-KT to select specific anti-idiotypic scFv antibodies of HM-1. After modified panning, 80% clones (40/50) showed several times higher binding affinity to nmAb-KT than regular panning. The major populations (48%) of these clones (scFv K1) were genotypically same and had strong cytocidal activity against Saccharomyces and Candida species. The scFv K1 (K(d) value = 4.62 x 10(-8) M) had strong reactivity toward nmAb-KT, like HM-1 (K(d) value = 6.74 x 10(-9) M) as judged by SPR analysis.

CONCLUSION

The scFv antibodies generated after modified subtractive panning appear to have superior binding properties and cytocidal activity than regular panning. A simple modification of the elution condition in the phage-display panning protocol makes a large difference in determining success. Our method offers an attractive platform to discover potential therapeutic candidates.

In Vitro Antifungal Activities of Sulfa Drugs against Clinical Isolates of Aspergillus and Cryptococcus Species

In vitro susceptibilities of ten clinical isolates, including five strains of Cryptococcus neoformans var. grubii and five strains of Aspergillus fumigatus, were determined against nine sulfa drugs using a microdilution method. Among the five tested media, minimum inhibitory concentration (MIC) values were observed only in YNB medium: no detectable level MIC value of less than 125 microg/ml was observed in the four remaining media against Cryptococcus species. Of the nine sulfa drugs, of which sulfaphenazole showed the highest antifungal activity, the MIC values for A. fumigatus and C. neoformans var. grubii were, respectively, 64 microg/ml and 4-8 microg/ml, suggesting high susceptibility of C. neoformans to sulfa drugs.

Inhibition of fungal beta-1,3-glucan synthase and cell growth by HM-1 killer toxin single-chain anti-idiotypic antibodies

Single-chain variable-fragment (scFv) anti-idiotypic antibodies of an HM-1 killer toxin (HM-1) from the yeast Williopsis saturnus var. mrakii IFO 0895 have been produced by recombinant DNA technology from the splenic lymphocytes of mice immunized by idiotypic vaccination with a neutralizing monoclonal antibody (nMAb-KT). The fungicidal activity of scFv anti-idiotypic antibodies against the isolates of four Candida species was assessed by MIC analysis. scFv antibodies were fungicidal at concentrations of 1.56 to 12.5 microg/ml in vitro against four Candida species. The scFv antibodies exerted a strong candidacidal activity in vitro, with 50% inhibitory concentration (IC(50)) values ranging from 7.3 x 10(-8) to 16.0 x 10(-8) M, and were neutralized by adsorption with nMAb-KT. Furthermore, all scFv antibodies effectively inhibited fungal beta-1,3-glucan synthase activity in vitro, with IC(50) values ranging from 2.0 x 10(-8) to 22.7 x 10(-8) M, values which almost coincide with the values that are inhibitory to the growth of fungal cells. Binding assays showed that the scFv antibodies specifically bind to nMAb-KT, and this binding pattern was confirmed by surface plasmon resonance analysis. The binding ability was further demonstrated by the competition observed between scFv antibodies and HM-1 to bind nMAb-KT. To the best of our knowledge, this is the first study to show that an antifungal anti-idiotypic antibody, in the form of recombinant scFv, potentially inhibits beta-1,3-glucan synthase activity.

Recombinant single-chain anti-idiotypic antibody: an effective fungal beta-1,3-glucan synthase inhibitor

Recombinant single-chain fragment variable anti-idiotypic antibodies were produced to represent the internal image of HM-1 killer toxin and were used as novel and effective antifungal agents to inhibit in vitro beta-1,3-glucan synthase and cell growth. The mechanism of cytocidal activity of anti-idiotypic antibodies was investigated and was compared with the actions of aculeacin A and papulacandin B, the most common antibiotics acting as beta-1,3-glucan synthase inhibitors. The degree of inhibition of beta-1,3-glucan synthase by both antibodies and antibiotics were examined for yeasts Saccharomyces cerevisiae A451, Cryptococcus albidus NBRC 0612 and Candida albicans IFM 40215. Although the mechanism of actions of the anti-idiotypic antibodies and antibiotics seems identical, the IC(50) values for the various yeasts used in this study confirmed that anti-idiotypic antibodies could be used as more effective fungal beta-1,3-glucan synthase inhibitors than those of antibiotics.

Inhibition of beta-1,3-glucan synthase and cell growth of Cryptococcus species by recombinant single-chain anti-idiotypic antibodies

Recombinant single-chain fragment variable (scFv) anti-idiotypic antibodies were produced to represent the internal image of a HM-1 killer toxin, which is characterized by a wide spectrum of anti-fungal activity through inhibiting beta-1,3-glucan synthase (GS). We examined if scFv antibodies are active against Cryptococcus species, a human pathogen of increasing medical importance. The anti-cryptococcal activity of scFv antibodies and HM-1 were assessed by MIC analysis for C. neoformans IFM 40215 and C. albidus NBRC 0612 cells. The scFv antibodies had strong anti-cryptococcal activity in vitro with IC50 at 1.07 x 10(-7) to 2.60 x 10(-7) M for C. neoformans and C. albidus. Furthermore, the scFv antibodies potentially inhibited GS of C. neoformans with IC50 at 1.27 x 10(-7) to 2.27 x 10(-7) M. Both the anti-fungal and anti-GS activities of the scFv antibodies were markedly neutralized by the monoclonal antibody that neutralizes HM-1 killer toxin.

Epidemiological assessment of mucocutaneous infections in patients with recurrent infection syndrome

BACKGROUND

Recurrent infection syndrome (RIS) results from repeated interactions between hosts and environmental infectious agents and is considered normal (NRIS) because of its benign evolution and positive effects in the development of normal immune responses. Abnormal RIS (ARIS) is characterized by the unusually high frequency of severe infections, either as a result of anatomical or functional abnormalities or due to primary or secondary immunodeficiencies (PIDs and SIDs, respectively). Recurrent mucocutaneous infections (MCIs) can be manifestations of RIS or ARIS and could be more frequent in primary immunodeficiencies. Similarly, etiologic agents might vary from what is observed in the general population.

METHODS

We carried out a descriptive study to determine the prevalence of aerobic bacterial and fungal mucocutaneous infections in 452 patients with recurrent infections, using clinical records to establish immunological status associated with the presence and characteristics of the infections. Microbiological analyses from mucocutaneous lesions were used to confirm the etiology.

RESULTS

We found mucocutaneous infections in 50 patients for a total of 62 episodes (bacterial or fungal infections in 38 vs. 12 patients, respectively). Mucocutaneous infections were more frequent (21.8% vs. 9.1%; OR = 2.8) and recurrent (8.7% vs. 0.2%; P = 0.000) in primary immunodeficient patients. Furthermore, those with defects in phagocytic cells presented more mucocutaneous infections (56.2%) than patients with other primary immunodeficiencies (11.3%; OR = 10.1).

CONCLUSIONS

Bacterial and fungal mucocutaneous infections are more frequent and severe in primary immunodeficient patients, particularly those with defective phagocytosis. Early and adequate assessment of the nature of mucocutaneous infections in ARIS should impact the ability of physicians to treat promptly, avoid complications and reduce the costs of medical assistance.

Anti-fungal Activity of Sulfamethoxazole toward Aspergillus Species

Invasive mycosis has significantly increased in frequency among immunocompromised hosts leading to excessive morbidity and mortality. The combination of sulfamethoxazole (SMX) and trimethoprim (TMP) has been used extensively for the treatment and prophylaxis of infections by various microbes. The purpose of this study is to estimate the anti-fungal activity of SMX-TMP and examine the mechanism of activity. To investigate the antimicrobial activity of SMX-TMP in vitro, a mixture of SMX and TMP at 5:1 was serially diluted and added to potato dextrose agar medium or C-limiting agar medium. Aspergillus species were inoculated on the medium plate with SMX-TMP. The growth of A. fumigatus and A. oryzae was inhibited by addition of SMX-TMP. The anti-Aspergillus effect depended on not TMP but SMX and that was inhibited by p-aminobenzoic acid (PABA). A. niger was not sensitive against SMX-TMP in PDA medium, but sensitive in C-limiting medium. Those results showed that the activity depends on culture medium. Furthermore, addition of human serum did not influence the activity of SMX. The finding in this study suggested that SMX might be effective against Aspergillus species in clinical practice and prophylaxis treatment.

Curing onychomycosis: understanding the multitude of variables

This article provides a focused look at the need to treat onychomycosis from a podiatric perspective, new classifications of the disorder, definitive diagnostic methods, predictability of host responsiveness, and current strategies for treatment.

Tinea corporis in human immunodeficiency virus-positive patients: case report and assessment of oral therapy

Dermatophytosis in immunocompromised hosts is more varied and often more severe than in immunocompetent hosts. Early recognition and treatment with systemic therapy are important in human immunodeficiency virus (HIV)-positive patients in order to prevent severe infection. Potential drug resistance can occur due to chronic usage of systemic azole therapy in such patients, or the existence of atypical fungi. Although warnings have been made of possible drug interactions between certain antifungals and antiretroviral medications, only one combination has shown a clinically significant interaction. A case treated aggressively with oral terbinafine at the onset is presented.

BACKGROUND

Dermatophytosis in immunocompromised hosts is more varied and often more severe than in immunocompetent hosts. Early recognition and treatment with systemic therapy are important in human immunodeficiency virus (HIV)-positive patients in order to prevent severe infection.

OBJECTIVE

To analyze potential therapies for dermatophyte infections in immunocompromised patients and risk of drug resistance and interactions with antiretroviral medications.

METHODS

Literature search based on MEDLINE (1966-March 2003) and additional references obtained from cross-referencing retrieved articles. All information deemed relevant by the reviewers was included. A case study was employed to exemplify the usage of this information in patient care.

RESULTS

Although warnings have been made of possible drug interactions between certain antifungals and antiretroviral medications, only one combination has shown a clinically significant interaction.

CONCLUSIONS

When considering drug interactions and side-effects, there are no clinically significant reasons to avoid any oral antifungal for dermatophytosis in the HIV-positive patient.

Regulation of Candida albicans growth and adhesion by saliva

To examine the local regulation of oral Candida albicans growth, we examined non-stimulated and stimulated salivary flow rates (SFRs) and the C. albicans growth and adhesion inhibitory activities of saliva in 60 patients with oral candidiasis (divided into two groups: 25 patients with oral candidiasis only (group OC) and 35 patients with oral candidiasis and systemic diseases (group CS)) and 30 healthy control subjects. Both non-stimulated and stimulated SFRs in patients, especially in group CS; were decreased in comparison with those in the healthy control subjects. The levels of secretory immunoglobulin A (sIgA) in group OC and group CS and the lactoferrin level in group CS were decreased as compared with those in control individuals, although there were no differences in transferrin and total secretory component (SC) levels between the three groups. The secretion amounts (microg/min) of these proteins were statistically significantly decreased in the patients, especially in group CS. Saliva from the patients showed a lesser inhibitory effect on C. albicans growth and adhesion to HeLa cells than did saliva from the control subjects. In addition, polymorphonuclear leukocytes (PMNs) in patients' saliva generated smaller amounts of superoxide than did those in control subjects' saliva, and phagocytic and C. albicans killing activities were suppressed in the patients. These results indicate that the decreases in SFR, secretion of antimicrobial proteins in saliva, and salivary PMN activity are risk factors for oral candidiasis associated with aging and systemic diseases.

Fungal skin disorders

Fungal skin infections are becoming more common, and primary care physicians must be familiar with the diagnosis and treatment of these disorders. Dermatophyte infections including tinea pedis, corporis and cruris; pityriasis versicolor; and cutaneous candidiasis are the focus of this article. Common presentations of these disorders, the differential diagnosis, and current treatments are stressed. With the newer agents, shorter treatment courses can be used, and oral therapy for widespread, resistant, or recurrent infections is discussed.