Here, one hundred patients (50 smokers and 50 non-smokers) clinically diagnosed with COVID-19 were studied. Yet, bioinformatics was used to predict epitopes on Tobacco mosaic virus coat protein (TMV-CP) to produce antibodies towards SARS-CoV-2. Death was three times higher in non-smokers than in smokers. However, biochemical parameters did not separate the groups. Bioinformatics analysis predicted the presence of B-cell epitopes in TMV-CP, suggesting the production of antibodies anti-TMV-CP in smoker patients. Smokers may develop severe forms of COVID-19, but survival was superior in the evaluated group than in non-smokers. Anti-TMV-CP antibodies, potentially present in smokers, might act as a pro-immune agent against SARS-CoV-2 at earlier stages of infection. These data are helpful for future studies assessing COVID-19 in smokers.

Cryptococcus neoformans is a multidrug-resistant human pathogenic yeast responsible for infections in immunocompromised patients. Here, Itraconazole (ITR), a commercial antifungal drug with low effectiveness against C. neoformans, was combined with different synthetic peptides Mo-CBP3-PepII, RcAlb-PepII, RcAlb-PepIII, PepGAT, and PepKAA. The mechanisms of action responsible for the synergistic effect were evaluated for the best combinations by Fluorescence Microscopy (FM). The synthetic peptides enhanced the activity of ITR by 10-fold against C. neoformans. Our results demonstrated that the combinations could induce pore formation in the membrane and overaccumulation of ROS on C. neoformans cells. Our findings indicate that our peptides successfully potentialize the activity of ITR by reducing it by 10-fold to reach antifungal activity against C. neoformans. Therefore, synthetic peptides are potential molecules to act as co-adjuvant agents in treating Cryptococcal infections.

Cryptococcus neoformans threaten the health, causing cryptococcal meningitis and pneumonia, especially in immunosuppressed patients, which can be fatal. Recently, our research group evaluated and studied the mechanisms of action of four synthetic peptides (SP) against C. neoformans. Here, in silico and in vitro analyses help deepen understanding of peptides' mechanisms of action. The interaction of the peptides with a membrane receptor was analyzed by docking analysis, in addition to ROS overproduction and the modulation of redox metabolism, inhibition of ergosterol biosynthesis, and release of cytochrome c. Out of four, three peptides interacted with membrane receptor PHO36 altering its structure and function and leading to a higher accumulation of O₂- and H2O2. C. neoformans cells treated with SP presented a reduction in the activity of antioxidant enzymes, corroborating ROS accumulation. However, in the presence of the antioxidant ascorbic acid, some peptides could not induce this oxidative stress and have the activity against C. neoformans affected. Curiously, two of these SPs still maintained the activity against C. neoformans and even induced the membrane pore formation as revealed by propidium iodide uptake assay, revealing their mechanism of action is ROS-independent. Additionally, SPs inhibited the biosynthesis of ergosterol, which corroborates the pore formation on the membrane of C. neoformans cells, inhibited the lactate dehydrogenase activity affecting the cell metabolism, and induced the release of Cyt c from the mitochondria inducing death by apoptosis in the cryptococcal cells. Our findings strongly suggest that SPs act by multiple mechanisms, making it difficult for C. neoformans to acquire resistance highlighting the potential of SPs as alternative molecules in treating infections caused by C. neoformans.

Klebsiella pneumoniae is a multidrug-resistant opportunistic human pathogen related to various infections. As such, synthetic peptides have emerged as potential alternative molecules. Mo-CBP3-PepI has presented great activity against K. pneumoniae by presenting an MIC50 at a very low concentration (31.25 µg mL-1). Here, fluorescence microscopy and proteomic analysis revealed the alteration in cell membrane permeability, ROS overproduction, and protein profile of K. pneumoniae cells treated with Mo-CBP3-PepI. Mo-CBP3-PepI led to ROS overaccumulation and membrane pore formation in K. pneumoniae cells. Furthermore, the proteomic analysis highlighted changes in essential metabolic pathways. For example, after treatment of K. pneumoniae cells with Mo-CBP3-PepI, it was seen a reduction in the abundance of protein related to DNA and protein metabolism, cytoskeleton and cell wall organization, redox metabolism, regulation factors, ribosomal proteins, and resistance to antibiotics. These reductions lead to the inhibition of DNA repair, inhibition of cell wall turnover, protein turnover, and ROS accumulation leading to cell death. Our findings indicated that Mo-CBP3-PepI might have mechanisms of action against K. pneumoniae cells, mitigating the development of resistance and thus being a potent molecule to be employed in producing new drugs against K. pneumoniae infections.

Angiotensin-converting enzyme 2 (ACE2) and the transmembrane serine protease 2 (TMPRSS2) are recognized as entry proteins of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and recently their Single Nucleotide Polymorphisms (SNP) have been studied in different populations to elucidate the impact on disease. The aim of this study was to evaluate the genetic SNP of ACE2 (rs35803318) and TMPRSS2 (rs2070788) genes in COVID-19 patients from Northeast Brazil compared with global populations, as well as the expression quantitative trait locus (eQTL). For ACE2 (rs35803318), we found 92.6% CC, 3.4% CT, and 4.0% TT genotype carriers in SARS-CoV-2-positive patients. Surprisingly, only the genotype frequencies of ACE2 SNP were not in Hardy-Weinberg equilibrium. For TMPRSS2 rs2070788, we found 22.3% GG, 50.7% AG, and 27% AA genotype carriers in SARS-CoV-2-positive patients. The expression quantitative trait loci (eQTLs) revealed that rs35803318 was associated with an altered PIR gene expression, and rs2070788 was found eQTLs association only with lung tissue. No significant association was identified between the genotype distribution of SNPs and the 'patient's outcome. In conclusion, our results suggest that ACE2 and TMPRSS2 may not be protective factors for global populations, including the Brazilian population, since the presence of SNPs does not affect the 'patient's outcome as described by other studies.