Major histocompatibility complex class I (MHC I) plays a crucial role in the development of adaptive immune response in vertebrates. MHC molecules are cell surface protein complexes loaded with short peptides and recognized by the T-cell receptors (TCR). Peptides associated with MHC are named immunopeptidome. The MHC I immunopeptidome is produced by the proteasome degradation of intracellular proteins. The knowledge of the immunopeptidome repertoire facilitates the creation of personalized antitumor or antiviral vaccines. A huge number of publications on the immunopeptidome diversity of different human and mouse biological samples—plasma, peripheral blood mononuclear cells (PBMCs), and solid tissues, including tumors—appeared in the scientific journals in the last decade. Significant immunopeptidome identification efficiency was achieved by advances in technology: the immunoprecipitation of MHC and mass spectrometry-based approaches. Researchers optimized common strategies to isolate MHC-associated peptides for individual tasks. They published many protocols with differences in the amount and type of biological sample, amount of antibodies, type and amount of insoluble support, methods of post-fractionation and purification, and approaches to LC-MS/MS identification of immunopeptidome. These parameters have a large impact on the final repertoire of isolated immunopeptidome. In this review, we summarize and compare immunopeptidome isolation techniques with an emphasis on the results obtained.

Helicobacter is a genus of spiral-shaped Gram-negative enterohepatic bacteria whose members are capable of causing bacteremia in humans. One of the poorly studied members of this genus is the bacterium Helicobacter cinaedi. This microorganism was first isolated from human fecal samples in 1984. Although it was long considered to be associated with only immunocompromised patients, more evidence in recent years has implicated H. cinaedi in causing serious pathologies in immunocompetent populations. In addition, H. cinaedi is also reported to be associated with a few chronic or severe illnesses, such as atherosclerosis, which in turn can lead to the development of other cardiovascular pathologies: one of the leading causes of mortality worldwide. Helicobacter cinaedi often goes unnoticed in standard diagnostic methods due to its slow growth under microaerobic conditions. This often leads to significant underdetection and hence undermines the role of this bacterium in the pathogenesis of various diseases and the extent of its spread in humans. In this review, we have compiled information on pathologies associated with H. cinaedi, the occurrence of the bacterium in humans and animals, and the latest developments in diagnosing the bacterium and treating associated diseases.

Introduction: Helicobacter cinaedi is a spiral-shaped Gram-negative, enterohepatic bacterium classified as a conditional pathogen (pathogenicity group 2). It is known to cause bacteremia and a variety of other diseases in humans. In particular, Helicobacter cinaedi has been shown to impair intracellular cholesterol metabolism when interacting with macrophages, leading to foam cell formation. M1-macrophages transformed into the foam cell phenotype contribute to atherosclerotic plaques, suggesting a potential link between H. cinaedi infection and atherosclerosis development.Methods: To uncover protein factors involved in H. cinaedi pathogenesis, we performed a detailed mass spectrometric analysis of the proteome of strain BAA-847. This study represents the first comprehensive analysis of the bacterium’s proteome under standard culture conditions and after infection of M1-type macrophage cells.Results: We identified 1,575 proteins in the H. cinaedi proteome, 109 of which were differentially upregulated after macrophage infection. Functional analysis revealed roles for these proteins in immune evasion, intracellular survival, and potential pathogenicity. Beyond known virulence factors (HcaA, Cdt, AhpC), we identified poorly characterized proteins with toxic or immunomodulatory functions. Notably, some upregulated proteins enable cholesterol utilization as a carbon source, while others may participate in a toxin injection mechanism disrupting host cell metabolism—potentially linked to foam cell formation.Conclusion: Our findings provide new insights into H. cinaedi pathogenicity, highlighting previously unexplored virulence mechanisms. The identified proteins could serve as targets for further research into H. cinaedi-associated diseases, including atherosclerosis.