Enterohemorrhagic Escherichia coli (EHEC) strains are food-borne pathogens that can cause different clinical conditions. Shiga toxin 2a and/or 2c (Stx2)-producing E. coli O157:H7 is the serotype most frequently associated with severe human disease. In this work we analyzed the hypothesis that host cells participate in Stx2 production, cell damage, and inflammation during EHEC infection. With this aim, macrophage-differentiated THP-1 cells and the intestinal epithelial cell line HCT-8 were incubated with E. coli O157:H7. A time course analysis of cellular and bacterial survival, Stx2 production, stx₂ transcription, and cytokine secretion were analyzed in both human cell lines. We demonstrated that macrophages are able to internalize and kill EHEC. Simultaneously, Stx2 produced by internalized bacteria played a major role in macrophage death. In contrast, HCT-8 cells were completely resistant to EHEC infection. Besides, macrophages and HCT-8 infected cells produce IL-1β and IL-8 inflammatory cytokines, respectively. At the same time, bacterial stx₂-specific transcripts were detected only in macrophages after EHEC infection. The interplay between bacteria and host cells led to Stx production, triggering of inflammatory response and cell damage, all of which could contribute to a severe outcome after EHEC infections.

Editorial: Shiga toxin-producing Escherichia coli (STEC) infections and consequences

Background/Objectives: Vaccine immunogenicity is often suboptimal in vulnerable populations such as the elderly, infants, and individuals in low- and middle-income countries. One contributing factor may be pre-existing immunomodulatory conditions, including helminth infections. This study investigates the impact of Fasciola hepatica (F. hepatica) derived molecules on the early humoral response to the COVID-19 mRNA vaccine Comirnaty^® in a mouse model. Methods: BALB/c mice were pretreated with a F. hepatica protein extract (FH) or complete Freund’s adjuvant (CFA) prior to vaccination. Cytokine production and antibody responses were assessed at 0, 14, and 21 days post-vaccination (dpv) through serum analysis and ex vivo splenocyte stimulation with the SARS-CoV-2 receptor-binding domain (RBD) or LPS. Results: At 0 dpv, FH-treated mice showed increased serum IL-10, while CFA treatment induced IL-12. FH- but not CFA-treated splenocytes secreted IL-10 upon RBD or LPS stimulation. At 21 dpv, FH-treated mice lacked IFN-γ production but maintained IL-10 and showed elevated IL-4, consistent with a Th2-skewed profile. Although total anti-RBD IgG levels were similar between groups, FH-treated mice exhibited reduced IgG avidity and a higher IgG1/IgG2 ratio. CFA-treated mice showed delayed avidity maturation. Conclusions: Prior exposure to F. hepatica antigens can modulate the early immune response to Comirnaty^®, affecting both cellular activation and antibody quality. This altered response may reflect a reduced early protective capacity of the vaccine, which might need to be considered when designing or evaluating vaccination strategies using mRNA vaccines in helminth-endemic regions.

Bacteriophage-encoded endolysins have emerged as novel antibacterial strategies against antibiotic-resistant bacteria. We identified a bacteriophage-derived conserved sequence encoding an endolysin specific to Staphylococcus aureus. A recombinant endolysin (LysNOVA-I) was then produced, characterised and evaluated against methicillin-resistant Staphylococcus aureus (MRSA). The endolysin gene from phage ФvB_SauS-phiIPLA88 was cloned, expressed, and successfully purified using affinity chromatography. The activity of pure recombinant endolysin (rLysNOVA-I) was subsequently evaluated against growing and non-growing planktonic cells and biofilm cultures of international MRSA clones. A computational analysis was conducted to elucidate protein folding and obtain insight into the molecular mechanisms. rLysNOVA-I exhibited bactericidal activity against both exponential and stationary growth phase S. aureus cells. rLysNOVA-I also prevented biofilm formation and degradation of established S. aureus biofilms. Notably, rLysNOVA-I was active against the MRSA clone ST398, which is of veterinary and clinical relevance. Our findings highlight the clinical potential of rLysNOVA-I as a therapeutic or complementary alternative to antibiotics against multidrug-resistant S. aureus infections in human and veterinary medicine.