Proteome-wide antigen discovery of novel protective vaccine candidates against Staphylococcus aureus infection

The Virulent Hypothetical Proteins: The Potential Drug Target Involved in Bacterial Pathogenesis

Abstract:

Hypothetical proteins (HPs) are non-predicted sequences that are identified only by open reading frames in sequenced genomes but their protein products remain uncharacterized by any experimental means. The genome of every species consists of HPs that are involved in various cellular processes and signaling pathways. Annotation of HPs is important as they play a key role in disease mechanisms, drug designing, vaccine production, antibiotic production, and host adaptation. In the case of bacteria, 25-50% of the genome comprises of HPs, which are involved in metabolic pathways and pathogenesis. The characterization of bacterial HPs helps to identify virulent proteins that are involved in pathogenesis. This can be done using in-silico studies, which provide sequence analogs, physiochemical properties, cellular or subcellular localization, structure and function validation, and protein-protein interactions. The most diverse types of virulent proteins are exotoxins, endotoxins, and adherent virulent factors that are encoded by virulent genes present on the chromosomal DNA of the bacteria. This review evaluates virulent HPs of pathogenic bacteria, such as Staphylococcus aureus, Chlamydia trachomatis, Fusobacterium nucleatum, and Yersinia pestis. The potential of these HPs as a drug target in bacteria-caused infectious diseases along with the mode of action and treatment approaches have been discussed.

Surface Immunoproteomics Reveals Potential Biomarkers in Alicyclobacillus acidoterrestris

Alicyclobacillus acidoterrestris is a major putrefying bacterium that can cause pecuniary losses in the global juice industry. Current detection approaches are time-consuming and exhibit reduced specificity and sensitivity. In this study, an immunoproteomic approach was utilized to identify specific biomarkers from A. acidoterrestris for the development of new detection methods. Cell surface-associated proteins were extracted and separated by 2-D (two-dimensional) gel electrophoresis. Immunogenic proteins were detected by Western blot analysis using antisera against A. acidoterrestris. Twenty-two protein spots exhibiting immunogenicity were excised and eighteen of the associated spots were successfully identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS). These proteins were observed to be involved in energy and carbohydrate metabolism, transmembrane transport, response to oxidative stress, polypeptide biosynthesis, and molecule binding activity. This is the first report detailing the identification of cell surface-associated antigens of A. acidoterrestris. The identified immunogenic proteins could serve as potential targets for the development of novel detection methods.

Staphylococcus aureus Strain Newman D2C Contains Mutations in Major Regulatory Pathways That Cripple Its Pathogenesis

Staphylococcus aureus is a major human pathogen that imposes a great burden on the health care system. In the development of antistaphylococcal modalities intended to reduce the burden of staphylococcal disease, it is imperative to select appropriate models of S. aureus strains when assessing the efficacy of novel agents. Here, using whole-genome sequencing, we reveal that the commonly used strain Newman D2C from the American Type Culture Collection (ATCC) contains mutations that render the strain essentially avirulent. Importantly, Newman D2C is often inaccurately referred to as simply "Newman" in many publications, leading investigators to believe it is the well-described pathogenic strain Newman. This study reveals that Newman D2C carries a stop mutation in the open reading frame of the virulence gene regulator, agrA In addition, Newman D2C carries a single-nucleotide polymorphism (SNP) in the global virulence regulator gene saeR that results in loss of protein function. This loss of function is highlighted by complementation studies, where the saeR allele from Newman D2C is incapable of restoring functionality to an saeR-null mutant. Additional functional assessment was achieved through the use of biochemical assays for protein secretion, ex vivo intoxications of human immune cells, and in vivo infections. Altogether, our study highlights the importance of judiciously screening for genetic changes in model S. aureus strains when assessing pathogenesis or the efficacy of novel agents. Moreover, we have identified a novel SNP in the virulence regulator gene saeR that directly affects the ability of the protein product to activate S. aureus virulence pathways.IMPORTANCE Staphylococcus aureus is a human pathogen that imposes an enormous burden on health care systems worldwide. This bacterium is capable of evoking a multitude of disease states that can range from self-limiting skin infections to life-threatening bacteremia. To combat these infections, numerous investigations are under way to develop therapeutics capable of thwarting the deadly effects of the bacterium. To generate successful treatments, it is of paramount importance that investigators use suitable models for examining the efficacy of the drugs under study. Here, we demonstrate that a strain of S. aureus commonly used for drug efficacy studies is severely mutated and displays markedly reduced pathogenicity. As such, the organism is an inappropriate model for disease studies.

Microbiome precision editing: Using PEG as a selective fermentation initiator against methicillin-resistant Staphylococcus aureus

Recent creation of a Unified Microbiome Initiative (UMI) has the aim of understanding how microbes interact with each other and with us. When pathogenic Staphylococcus aureus infects the skin, the interplay between S. aureus and skin commensal bacteria occurs. Our previous data revealed that skin commensal bacteria can mediate fermentation against the growth of USA300, a community-acquired methicillin-resistant S. aureus MRSA. By using a fermentation process with solid media on a small scale, we define poly(ethylene glycol) dimethacrylate (PEG-DMA) as a selective fermentation initiator which can specifically intensify the probiotic ability of skin commensal Staphylococcus epidermidis bacteria. At least five short-chain fatty acids including acetic, butyric and propionic acids with anti-USA300 activities are produced by PEG-DMA fermentation of S. epidermidis. Furthermore, the S. epidermidis-laden PEG-DMA hydrogels effectively decolonized USA300 in skin wounds in mice. The PEG-DMA and its derivatives may become novel biomaterials to specifically tailor the human skin microbiome against invading pathogens.