Rational design of bifunctional chimeric peptides that combine antimicrobial and titanium binding activity.

Bacterial biofilm formation remains a serious problem for clinical materials and often leads to implant failure. To counteract bacterial adhesion, which initiates biofilm formation, the development of antibiotic surface coating strategies is of high demand and warrants further investigations. In this study, we have created bifunctional chimeric peptides by fusing the recently developed antimicrobial peptide MGD2 (GLRKRLRKFFNKIKF) with different titanium-binding sequences. The novel peptides were investigated regarding their antibacterial potential against a set of different bacterial strains including drug-resistant Staphylococcus aureus. All peptides showed high antimicrobial activities both when in solution and when immobilized on titanium surfaces. Owing to the ease of synthesis and handling, the herein described peptides might be a true alternative to prevent bacterial biofilm formation.

Triazole-Bridged Peptides with Enhanced Antimicrobial Activity and Potency against Pathogenic Bacteria.

There are still no linear antimicrobial peptides (AMPs) available as a treatment option against bacterial infections. This is caused by several drawbacks that come with AMPs such as limited proteolytic stability and low selectivity against human cells. In this work, we screened a small library of rationally designed new peptides based on the cell-penetrating peptide sC18* toward their antimicrobial activity. We identified several effective novel AMPs and chose one out of this group to further increase its potency. Therefore, we introduced a triazole bridge at different positions to provide a preformed helical structure, assuming that this modification would improve (i) proteolytic stability and (ii) membrane activity. Indeed, placing the triazole bridge within the hydrophilic part of the linear analogue highly increased membrane activity as well as stability against enzymatic digestion. The new peptides, 8A and 8B, demonstrated high activity against several bacterial species tested including pathogenic N. gonorrhoeae and methicillin-resistant S. aureus. Since they exhibited significantly good tolerability against human fibroblast and blood cells, these novel peptides offer true alternatives for future clinical applications and are worth studying in more detail.

Modified CLEC3A-Derived Antimicrobial Peptides Lead to Enhanced Antimicrobial Activity against Drug-Resistant Bacteria.

Antimicrobial peptides (AMPs) represent a promising alternative to conventional antibiotics. Sequence changes can significantly improve the therapeutic properties of antimicrobial peptides. In our study, we apply different sequence modifications to enhance the performance of the CLEC3A-derived AMPs HT-16 and HT-47. We truncated their sequences, inserting a triple-glycine linker, adding an N-terminal tryptophan residue, and generating a D-amino acid variant, resulting in the generation of seven new peptides. We investigated their antimicrobial activity against gram-positive and gram-negative bacteria, their cytotoxicity to murine cells, and the biostability of the modified peptides in serum. We identified a novel antimicrobial peptide, WRK-30, with enhanced antimicrobial potency against S. aureus and MRSA. Additionally, WRK-30 was less cytotoxic to eukaryotic cells, allowing its application in higher concentrations in an in vivo setting. In conclusion, we identified a novel CLEC3A-derived antimicrobial peptide WRK-30 with significantly improved therapeutic properties and the potential to widen the repertoire of conventional antibiotics.

The ratio of serum LL-37 levels to blood leucocyte count correlates with COVID-19 severity.

Beneficial effects of vitamin D on COVID-19 progression have been discussed in several studies. Vitamin D stimulates the expression of the antimicrobial peptide LL-37, and evidence shows that LL-37 can antagonize SARS-CoV-2. Therefore, we investigated the association between LL-37 and vitamin D serum levels and the severity of COVID-19. To this end, 78 COVID-19 patients were divided into 5 groups according to disease severity. We determined serum levels of LL-37, vitamin D, and routine laboratory parameters. We demonstrated a correlation of CRP, IL-6, PCT, leukocyte count, and LDH with the severity of COVID-19. Our study did not demonstrate a direct relationship between serum levels of LL-37 and vitamin D and the severity of COVID-19. LL-37 is produced by granulocytes and released at the site of inflammation. Therefore, the analysis of LL-37 in broncho-alvelolar lavage rather than in patient serum seems critical. However, since LL-37 is produced by granulocytes, we determined serum LL-37 levels as a function of leukocyte count. The LL-37/leukocyte count ratio correlates highly significantly inversely proportional with COVID-19 severity. Our results indicate that the LL-37/leukocyte count ratio could be used to assess the risk of COVID-19 progression as early as hospital admission.

Analysis of IgM, IgA, and IgG isotype antibodies Directed against SARS-CoV-2 spike glycoprotein and ORF8 in the course of COVID-19.

Immunoassays are a standard diagnostic tool that assesses immunity in severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infection. However, immunoassays do not provide information about contaminating antigens or cross-reactions and might exhibit inaccurately high sensitivity and low specificity. We aimed to gain insight into the serological immune response of SARS-CoV-2 patients by immunoblot analysis. We analyzed serum immunoglobulins IgM, -A, and -G directed against SARS-CoV-2 proteins by immunoblot analysis from 12 infected patients. We determined IgG isotype antibodies by commercially available ELISA and assessed the clinical parameters of inflammation status and kidney and liver injury. Unexpectedly, we found no correlation between the presence of antibodies and the future course of the disease. However, attention should be paid to the parameters CRP, IL-6, and LDH. We found evidence of antibody cross-reactivity, which questions the reliability of results for serum samples that tested negative for anti-SARS-CoV-2 antibodies when assessed by immunoassays. Nevertheless, for the detection of IgG anti-SARS-CoV-2 antibodies, our data suggest that the use of the spike glycoprotein in immunoassays should be sufficient to identify positive patients. Using a combination of the spike glycoprotein and the open reading frame 8 protein could prove to be the best way of detecting anti-SARS-CoV-2 IgM antibodies.