Molecular mechanisms of inhibiting glucosyltransferases for biofilm formation in Streptococcus mutans

Glucosyltransferases (Gtfs) play critical roles in the etiology and pathogenesis of Streptococcus mutans (S. mutans)- mediated dental caries including early childhood caries. Gtfs enhance the biofilm formation and promotes colonization of cariogenic bacteria by generating biofilm extracellular polysaccharides (EPSs), the key virulence property in the cariogenic process. Therefore, Gtfs have become an appealing target for effective therapeutic interventions that inhibit cariogenic biofilms. Importantly, targeting Gtfs selectively impairs the S. mutans virulence without affecting S. mutans existence or the existence of other species in the oral cavity. Over the past decade, numerous Gtfs inhibitory molecules have been identified, mainly including natural and synthetic compounds and their derivatives, antibodies, and metal ions. These therapeutic agents exert their inhibitory role in inhibiting the expression gtf genes and the activities and secretion of Gtfs enzymes with a wide range of sensitivity and effectiveness. Understanding molecular mechanisms of inhibiting Gtfs will contribute to instructing drug combination strategies, which is more effective for inhibiting Gtfs than one drug or class of drugs. This review highlights our current understanding of Gtfs activities and their potential utility, and discusses challenges and opportunities for future exploration of Gtfs as a therapeutic target.

D155Y Substitution of SARS-CoV-2 ORF3a Weakens Binding with Caveolin-1: An in silico Study

The clinical manifestation of the recent pandemic COVID-19, caused by novel SARS-CoV-2, varies from mild to severe respiratory illness. Although environmental, demographicand co-morbidity factors have an impact on the severity of the disease, the contribution of mutations in each of the viral genes towards the degree of severity needs to be elucidated for designing better therapeutic approach against COVID-19. Here, we studied the effect of two substitutions D155Y and S171L, of ORF3a protein, found in COVID-19 patients. Using computational simulations we discovered that the substitutions at 155th and 171st positions changed the amino acids involved in salt bridge formation, hydrogen-bond occupancy, interactome clusters, and the stability of the protein. Protein-protein docking using HADDOCK analysis revealed that out of the two observed substitutions, only the substitution of D155Y, weakened the binding affinity of ORF3a with caveolin-1. The increased fluctuation in the simulated ORF3a-caveolin-1 complex suggested a change in the virulence property of SARS-CoV-2.ImportanceThe binding interaction of viral ORF3a protein to host caveolin-1 is essential for entry and endomembrane trafficking of SARS-CoV-2. The D155Y substitution in SARS-CoV-2 ORF3a is located near its caveolin-binding Domain IV and thus the substitution can interfere with the binding affinity of ORF3a to host caveolin-1. Our in silico study report decreased molecular stability of D155Y mutant of ORF3a and increased fluctuation of the simulated D155Y ORF3a-caveolin-1 complex. Thus, we hypothesize that the D155Y substitution could change the virulence property of SARS-CoV-2.

Inhibition of Distinct Proline- or N-Acetylglucosamine-Induced Hyphal Formation Pathways by Proline Analogs in Candida albicans

Candida albicans undergoes a yeast-to-hyphal transition that has been recognized as a virulence property as well as a turning point leading to biofilm formation associated with candidiasis. It is known that yeast-to-hyphal transition is induced under complex environmental conditions including temperature (above 35°C), pH (greater than 6.5), CO2, N-acetylglucosamine (GlcNAc), amino acids, RPMI-1640 synthetic culture medium, and blood serum. To identify the hyphal induction factor in the RPMI-1640 medium, we examined each component of RPMI-1640 and established a simple hyphal induction condition, that is, incubation in L-proline solution at 37°C. Incubation in GlcNAc solution alone, which is not contained in RPMI-1640, without any other materials was also identified as another simple hyphal induction condition. To inhibit hyphal formation, proline and GlcNAc analogs were examined. Among the proline analogs used, L-azetidine-2-carboxylic acid (AZC) inhibited hyphal induction under both induction conditions, but L-4-thiazolidinecarboxylic acid (T4C) specifically inhibited proline-induced hyphal formation only, while α-N-methyl-L-proline (mPro) selectively inhibited GlcNAc-induced hyphal formation. Hyphal formation in fetal bovine serum was also inhibited by AZC or T4C together with mPro without affecting the proliferation of yeast form. These results indicate that these proline analogs are ideal inhibitors of yeast-to-hyphal transition in C. albicans.

Molecular conservation and Differential mutation on ORF3a gene in Indian SARS-CoV2 genomes

A global emergency due to the COVID-19 pandemic demands various studies related to genes and genomes of the SARS-CoV2. Among other important proteins, the role of accessory proteins are of immense importance in replication, regulation of infections of the coronavirus in the hosts. The largest accessory proteins in the SARS-CoV2 genome is ORF3a which modulates the host response to the virus infection and consequently it plays an important role in pathogenesis. In this study, an attempt is made to decipher the conservation of nucleotides, dimers, codons and amino acids in the ORF3a genes across thirty two genomes of Indian patients. ORF3a gene possesses single and double point mutations in Indian SARS-CoV2 genomes suggesting the change of SARS-CoV2’s virulence property in Indian patients. We find that the parental origin of the ORF3a gene over the genomes of SARS-CoV2 and Pangolin-CoV is same from the phylogenetic analysis based on conservations of nucleotides and so on. This study highlights the accumulation of mutation on ORF3a in Indian SARS-CoV2 genomes which may provide the designing therapeutic approach against SARS-CoV2.

Clinical and Demographic Characteristics Differences between M. tuberculosis and M. bovis Infection in Bronchoalveolar Lavage Pulmonary TB Patients, Indonesia

Background: Some species of the Mycobacterium tuberculosis complex (MTBC) which can cause tuberculosis, particularly M. tuberculosis and M. bovis, may have different virulence property and therefore associated with various clinical severity in tuberculosis (TB) patients. The aim of this study was to determine the differences in clinical and demographic characteristics between M. tuberculosis and M. bovis infection among Indonesian TB patients. Methods: Thirty-one new and active TB patients were confirmed to have acid fast bacilli (AFB) sputum positive and/or Xpert MTB/RIF positive for M. tuberculosis from Dr. Soewandhie Hospital, Surabaya, Indonesia. Interviews were conducted to record the clinical and demographics required. The MTBC were isolated from bronchoalveolar lavage fluid (BALF) and determined by primer-specific PCR targeting TbD1 and RD9 region gene. The degree of lung tissue damage was classified using NICE Scoring System. Results: The MTBC were detected in all patients on whom 19 and 12 isolates were classified as M. tuberculosis and M. bovis respectively. There was a different on 74.2% of productive age subjects (21-50 years) with M. tuberculosis infection (P