Karl Ocius

Elife. 2025 Jul 3;14:e96414. doi: 10.7554/eLife.96414.

ABSTRACT

Human cytomegalovirus (HCMV) is a relevant pathogen, especially for individuals with impaired immunity. Harnessing potent immune antagonists, HCMV circumvents sterile immunity. Given that HCMV prevents the upregulation of human leukocyte antigen (HLA)-DP and HLA-DR, we screened a library of HCMV genes by co-expression with the HLA class II (HLA-II)-inducing transcription coordinator class II transactivator (CIITA). We identified the latency regulator pUS28 as an interaction factor and potent viral antagonist of CIITA-driven expression of CD74, HLA-DR, HLA-DM, HLA-DQ, and HLA-DP. Both wt-pUS28 and a mutant incapable of inducing G protein-coupled signaling (R129A), but not a mutant lacking the C-terminus, drastically reduced the CIITA protein abundance post-transcriptionally. While control CD4 + T cells from HCMV-seropositive individuals vigorously responded to CIITA-expressing cells decorated with HCMV antigens, pUS28 expression was sufficient to inhibit HLA-II induction and immune recognition by HCMV-specific CD4 + T cells. Our data uncover pUS28 to be employed by HCMV to evade HLA-II-mediated recognition by CD4 + T cells.

PMID:40608405 | PMC:PMC12226020 | DOI:10.7554/eLife.96414

Biophys Rep. 2025 Jun 30;11(3):172-179. doi: 10.52601/bpr.2024.240044.

ABSTRACT

The profound influence of gut microbiota on human health has been well-recognized; however, substantial gaps remain in our understanding of the highly diverse and dynamic processes of microbial growth and activities in the gut. Conventional methods, which primarily rely on DNA sequencing, provide limited insights into these aspects. This paper presents a protocol that integrates fluorescent D-amino acid (FDAA) metabolic labeling with fluorescence in situ hybridization (FISH) for imaging and quantitatively analyzing the in vivo growth of gut microbiota. By administering two FDAAs sequentially through mouse gavage, we label the peptidoglycan of gut bacteria in their native environment, allowing the labeling signals on bacterial cell walls to serve as markers of cellular proliferation and division. We have also demonstrated that the intensity of FDAA labeling directly correlates with the metabolic activity of gut bacteria. Additionally, FISH is employed to distinguish specific bacterial taxa of interest via fluorescence microscopy or flow cytometry. This integrative method greatly enhances our capacity to visualize and measure the in vivo growth and metabolic states of various gut bacteria, thereby illuminating the previously obscured "dark matter" in the gut ecosystem.

PMID:40612236 | PMC:PMC12213662 | DOI:10.52601/bpr.2024.240044

Nat Commun. 2025 Jul 1;16(1):5577. doi: 10.1038/s41467-025-60678-5.

ABSTRACT

Gut microbiota-derived peptidoglycan fragments (PGNs) are key signaling molecules that regulate multiple aspects of the host's health. Yet the exact structures of natural PGNs in hosts have not been fully elucidated. Herein, we developed an LC-HRMS/MS analytical platform for global quantification and profiling of natural PGN subtypes in host gut and sera, unexpectedly revealing the abundance of PGN-derived saccharide moieties that do not resemble canonical ligands of mammalian NOD1/2 receptors. Focusing on the disaccharide GlcNAc-MurNAc (GM), which does not activate NOD1/2 yet still exhibits immunostimulatory effects in host immune cells, we established GM as a mild TLR4 agonist, illustrating an alternate PGN sensing mechanism other than NOD signaling. Importantly, the administration of GM mitigates colonic inflammation in the DSS-induced colitis model in mice via a TLR4-dependent manner, highlighting the in vivo significance of gut microbiota-derived PGN saccharides in maintaining host intestinal homeostasis.

PMID:40593577 | PMC:PMC12219203 | DOI:10.1038/s41467-025-60678-5

Int J Mol Sci. 2025 Jun 15;26(12):5742. doi: 10.3390/ijms26125742.

ABSTRACT

Aminopeptidase N (APN), an enzyme expressed in the small intestinal mucosa, is involved in dietary protein digestion. Previous studies have shown that oral administration of fermented milk containing lactic acid bacteria (LAB) enhances mucosal APN activity in young mice. This study aimed to investigate whether LAB strains stimulate mucosal APN activity in aged mice and to evaluate its relevance to age-related changes in body composition. The underlying molecular mechanisms were also explored in vitro. Experiment 1: Aged C57BL/6J mice were fed diets supplemented with heat-killed LAB strains-Enterococcus faecalis OU-23 (EF), Leuconostoc mesenteroides OU-03 (LM), or Lactiplantibacillus plantarum SNK12 (LP). Compared to the aged Control group, the ileal APN activity was significantly higher in the LP group. LP administration also elevated serum Gla-osteocalcin levels and decreased serum CTX-1 levels. Experiment 2: IEC-6 cells were co-cultured with LP that had been treated with RNase, DNase, or lysozyme. APN activity was significantly lower in cells co-cultured with DNase- or lysozyme-treated LP compared to those co-cultured with untreated LP. A specific LAB strain may enhance mucosal APN activity in the aged intestine, potentially contributing to improved bone metabolism. This effect may be mediated by bacterial DNA and peptidoglycan.

PMID:40565206 | PMC:PMC12193318 | DOI:10.3390/ijms26125742

Bioconjug Chem. 2025 Jun 24. doi: 10.1021/acs.bioconjchem.5c00014. Online ahead of print.

ABSTRACT

Bacterial peptidoglycans (PGs) are essential targets for antibiotics and immune cells. Chemical methods to reproduce PGs semisynthetically are tedious and wasteful. In this work, we describe a new approach to form pseudo-PGs (PPGs) using the protease papain and custom-made peptides conjugated to a glycan. The kinetics of formation is monitored by rheology and ¹H NMR. Viscoelastic gels of controlled strength are formed, depending on the temperature and the number of peptide bridges between the glycan chains. We propose that the new method has a high impact on biomaterials research, since it could be used to deliver peptides, test antibiotic efficacy, or investigate human immune cell response.

PMID:40552649 | DOI:10.1021/acs.bioconjchem.5c00014