Identification of vaccine candidate antigens of Staphylococcus pseudintermedius by whole proteome characterization and serological proteomic analyses

Antimicrobial Strategies Proposed for the Treatment of S. pseudintermedius and Other Dermato-Pathogenic Staphylococcus spp. in Companion Animals: A Narrative Review

The treatment of dermato-pathogenic Staphylococcus spp., particularly Staphylococcus pseudintermedius, in companion animals presents significant challenges due to rising antimicrobial resistance. This review explores innovative strategies to combat these infections. We examined novel antimicrobials and the repurposing of existing drugs to enhance their efficacy against resistant strains. Additionally, we evaluate the potential of natural products, nanomaterials, and skin antiseptics as alternative treatments. The review also investigates the use of antimicrobial peptides and bacteriophages, highlighting their targeted action against staphylococcal pathogens. Furthermore, the role of adjuvants in antibiotic treatments, such as antimicrobial resistance breakers, is discussed, emphasizing their ability to enhance therapeutic outcomes. Our analysis underscores the importance of a multifaceted approach in developing effective antimicrobial strategies for companion animals, aiming to mitigate resistance and improve clinical management of staphylococcal skin infections.

Investigation on biofilm composition and virulence traits of S. pseudintermedius isolated from infected and colonized dogs

Staphylococcus pseudintermedius, which is part of the skin microbiome of dogs, causes a variety of opportunistic infections. These infections may become more difficult to treat due to the formation of biofilm. The capacity of S. pseudintermedius to form biofilm, as well as the associated genes, has not been elucidated. This study evaluated the production and composition of S. pseudintermedius biofilm. Samples were collected from both infected dogs and asymptomatic dogs. Isolates were identified using mass spectrometry and Multiplex-PCR. Biofilm production and composition were assessed using a quantitative microtiter plate assay. The presence of ica operon genes and sps genes was investigated using conventional PCR. The investigation of Agr type and virulence genes was conducted in silico on 24 sequenced samples. All strains could produce strong biofilms, with most of the isolates presenting a polysaccharide biofilm. 63.6% of the isolates carried the complete ica operon (ADBC). All samples showed the presence of the genes spsK, spsA, and spsL, while the distribution of other genes varied. Agr type III was the most prevalent (52.2%). All sequenced samples carried the cytotoxins hlb, luk-S, luk-F, as well as the exfoliative toxins siet and se_int. No isolate displayed other exfoliative toxins. Only LB1733 presented a set of different enterotoxins (sea, seb, sec_canine, seh, sek, sel, and seq). Our findings suggest that S. pseudintermedius is a strong producer of biofilm and carries virulence genes.

Advanced strategies for development of vaccines against human bacterial pathogens

Infectious diseases are one of the main grounds of death and disabilities in human beings globally. Lack of effective treatment and immunization for many deadly infectious diseases and emerging drug resistance in pathogens underlines the need to either develop new vaccines or sufficiently improve the effectiveness of currently available drugs and vaccines. In this review, we discuss the application of advanced tools like bioinformatics, genomics, proteomics and associated techniques for a rational vaccine design.

Profiling of local disease-sparing responses to bovine respiratory syncytial virus in intranasally vaccinated and challenged calves

Bovine and human respiratory syncytial viruses (BRSV, HRSV) are primary causes of pneumonia in calves and children respectively, with vaccination offering protection via antibody and cellular immune responses. However, with no vaccines currently licensed for human use, evaluation of local responses to BRSV vaccination may provide insights to aid the design of effective safe HRSV vaccines. Calves received intranasal single component BRSV vaccine or "3-Way" vaccine (BRSV, Bovine Herpes Virus-1 (BHV-1), Bovine Parainfluenza Virus Type-3 (BPIV-3)), and were BRSV-challenged 42 days post-vaccination. All vaccinates exhibited reduced pulmonary lesioning with elevated anti-BRSV serum IgG, and higher nasal anti-BRSV IgA in 3-Way vaccinates. Thirty-nine proteins associated with homeostatic and immune processes were altered in vaccinates, with enhanced 3-Way vaccinate group proteins associated with Th1/Th2 balance and immunoglobulin class switching. Proteins altered in the pharyngeal tonsil of animals euthanized early related to anti-inflammatory responses and lymphoid tissue remodeling. These findings indicate that multivalent vaccines distinctly modulate local immune responses, with clear correlation between the pharyngeal tonsil proteome profile and resulting immune protection and disease-sparing. This suggests that the efficacy of low-antigenic subunit vaccine components for problematic pathogens such as HRSV could be enhanced by use in combination with existing safe live vaccines. SIGNIFICANCE: This study demonstrates that vaccine valency can alter post-challenge proteome responses within the pharyngeal tonsil, a sentinel site of primary immune responses, with the magnitude of response dependent on antigen formulation. Observed differential responses can be attributed to antigenic material and viral nucleic acid from multivalent formulations providing additional T-cell epitopes and PAMPS. These findings indicate that incorporation of subunits proteins within multivalent formulations containing live virus has the potential to induce/skew a favorable immune response, utilising the natural adjuvanting effects of safe proven live vaccines.

Immunoproteomics to identify Staphylococcus aureus antigens expressed in bovine milk during mastitis

Staphylococcus aureus is an opportunistic pathogen affecting both human and animal species. An effective vaccine to prevent S. aureus bovine disease and transmission would have positive effects on animal well-being, food production, and human health. The objective of this study was to identify multiple antigens that are immunoreactive during udder colonization and disease for exploration as vaccine antigens to prevent bovine mastitis. Staphylococcus aureus produces several cell wall-anchored and surface-associated virulence factors that play key roles in the pathogenesis of mastitis. Many of these proteins are conserved between different strains of S. aureus and represent promising vaccine candidates. We used an immunoproteomics approach to identify antigenic proteins from the surface of S. aureus. The expression of cell wall and surface proteins from S. aureus was induced under low iron conditions, followed by trypsin extraction and separation by 2-dimensional electrophoresis. The separated proteins were blotted with antibodies from mastitic bovine milk and identified by liquid chromatography-mass spectrometry. Thirty-eight unique proteins were identified, of which 8 were predicted to be surface exposed and involved in S. aureus virulence. Two surface proteins, iron-regulated surface determinant protein C (IsdC) and ESAT-6 secretion system extracellular protein (EsxA), were cloned, expressed, and purified from Escherichia coli for confirmation of immune reactivity by ELISA. A PCR of 37 bovine S. aureus isolates indicated that the presence of esxA and isdC is conserved, and amino acid alignments revealed that IsdC and EsxA sequences are highly conserved. The immunoproteomics technique used in this study generated reproducible results and identified surface exposed and reactive antigens for further characterization.

Expression and function of protein A in Staphylococcus pseudintermedius

Staphylococcus pseudintermedius is an opportunistic pathogen in dogs and the most frequent cause of canine pyoderma. Protein A, a potent virulence factor in S. aureus is encoded by the spa gene. S. pseudintermedius possesses genes seemingly analogous to spa, but the expression and the characteristics of their products have not been directly determined. The purpose of this study was to test isolates from major clonal groups for the presence of spa gene orthologs, quantitate their expression levels, and to characterize protein A in S. pseudintermedius.  From the data, it was observed that S. pseudintermedius isolates express genes analogous to spa in S. aureus. Isolates representing major clonal populations in the United States and Europe, ST68 and ST71 respectively, bound significantly higher amounts of canine IgG than isolates with other genetic backgrounds, suggesting that these isolates have a higher density of protein A on their surface. Also, canine IgG bound to protein A on S. pseudintermedius via its Fc region similar to protein A from S. aureus. The mRNA profile differed based on the bacterial sequence types and correlated to the density of protein A on the bacterial surface. Protein A was also found to be secreted during the exponential growth phase. Phagocytosis experiments with S. pseudintermedius show that blocking of protein A enhanced phagocytosis in whole blood, neutrophils and in DH82 canine macrophage-like cell line. Taken together, the results demonstrate that S. pseudintermedius produces protein A that shares S. aureus protein A's ability to bind the Fc region of immunoglobulins and may serve as a potential virulence factor by evading the host immune system.

Partial Immunoblotting of 2D-Gels: A Novel Method to Identify Post-Translationally Modified Proteins Exemplified for the Myelin Acetylome

Post-translational modifications (PTMs) play a key role in regulating protein function, yet their identification is technically demanding. Here, we present a straightforward workflow to systematically identify post-translationally modified proteins based on two-dimensional gel electrophoresis. Upon colloidal Coomassie staining the proteins are partially transferred, and the investigated PTMs are immunodetected. This strategy allows tracking back the immunopositive antigens to the corresponding spots on the original gel, from which they are excised and mass spectrometrically identified. Candidate proteins are validated on the same membrane by immunodetection using a second fluorescence channel. We exemplify the power of partial immunoblotting with the identification of lysine-acetylated proteins in myelin, the oligodendroglial membrane that insulates neuronal axons. The excellent consistency of the detected fluorescence signals at all levels allows the differential comparison of PTMs across multiple conditions. Beyond PTM screening, our multi-level workflow can be readily adapted to clinical applications such as identifying auto-immune antigens or host-pathogen interactions.