Staphylococcus aureus is an important pathogenic bacterium that causes various infectious diseases. Extracellular vesicles (EVs) released from S. aureus contain bacterial proteins, nucleic acids, and lipids. These EVs can induce immune responses leading to similar symptoms as during staphylococcal infection condition and have the potential as vaccination agent. Here, we show that active immunization (vaccination) with S. aureus-derived EVs induce adaptive immunity of antibody and T cell responses. In addition, these EVs have the vaccine adjuvant ability to induce protective immunity such as the up-regulation of co-stimulatory molecules and the expression of T cell polarizing cytokines in antigen-presenting cells. Moreover, vaccination with S. aureus EVs conferred protection against lethality induced by airway challenge with lethal dose of S. aureus and also pneumonia induced by the administration of sub-lethal dose of S. aureus. These protective effects were also found in mice that were adoptively transferred with splenic T cells isolated from S. aureus EV-immunized mice, but not in serum transferred mice. Furthermore, this protective effect of S. aureus EVs was significantly reduced by the absence of interferon-gamma, but not by the absence of interleukin-17. Together, the study herein suggests that S. aureus EVs are a novel vaccine candidate against S. aureus infections, mainly via Th1 cellular response.

Skin barrier disruption and dermal inflammation are key phenotypes of atopic dermatitis (AD). Staphylococcus aureus secretes extracellular vesicles (EVs), which are involved in AD pathogenesis. Here, we evaluated the role of EVs-associated α-hemolysin derived from S. aureus in AD pathogenesis. α-hemolysin production from S. aureus was detected using western blot analyses. The cytotoxic activity of α-hemolysin on HaCaT keratinocytes was evaluated by measuring cell viability after treating cells with soluble and EVs-associated α-hemolysin. To determine the type of cell death, HaCaT keratinocytes were stained with annexin V and 7-AAD. The in vivo effects of α-hemolysin were evaluated by application of soluble and EV-associated α-hemolysin on the mouse skin. The present study showed that increased α-hemolysin was produced by S. aureus colonized on AD patients compared to healthy subjects. α-hemolysin production was also related to AD severity. In addition, EV-associated α-hemolysin was more cytotoxic to HaCaT keratinocytes than soluble α-hemolysin, and α-hemolysin-negative EVs did not induce keratinocyte death. EV-associated α-hemolysin induced necrosis, but soluble α-hemolysin induced apoptosis of keratinocytes. In vivo, skin barrier disruption and epidermal hyperplasia were induced by soluble and EV-associated α-hemolysin. However, AD-like dermal inflammation was only caused by EV-associated α-hemolysin. Moreover, neither skin barrier disruption nor AD-like skin inflammation was induced by α-hemolysin-negative EVs. Taken together, α-Hemolysin secreted from S. aureus, particularly the EV-associated form, induces both skin barrier disruption and AD-like skin inflammation, suggesting that EV-associated α-hemolysin is a novel diagnostic and therapeutic target for the control of AD.

PurposeRecent experimental evidence shows that extracellular vesicles (EVs) in indoor dust induce neurtrophilic pulmonary inflammation, which is a characteristic pathology in patients with severe asthma and chronic obstructive pulmonary disease (COPD). In addition, COPD is known to be an important risk factor for lung cancer, irrespective of cigarette smoking. Here, we evaluated whether sensitization to indoor dust EVs is a risk for the development of asthma, COPD, or lung cancer.MethodsSerum IgG antibodies against dust EVs were measured in 90 healthy control subjects, 294 asthmatics, 242 COPD patients, and 325 lung cancer patients. Serum anti-dust EV IgG titers were considered high if they exceeded a 95 percentile value of the control subjects. Age-, gender-, and cigarette smoke-adjusted multiple logistic regression analyses were performed to determine odds ratios (ORs) for asthma, COPD, and lung cancer patients vs the control subjects.ResultsIn total, 4.4%, 13.6%, 29.3%, and 54.9% of the control, asthma, COPD, and lung cancer groups, respectively, had high serum anti-dust EV IgG titers. Adjusted multiple logistic regression revealed that sensitization to dust EVs (high serum anti-dust EV IgG titer) was an independent risk factor for asthma (adjusted OR, 3.3; 95% confidence interval [CI], 1.1-10.0), COPD (adjusted OR, 8.0; 95% CI, 2.0-32.5) and lung cancer (adjusted OR, 38.7; 95% CI, 10.4-144.3).ConclusionsIgG sensitization to indoor dust EVs appears to be a major risk for the development of asthma, COPD, and lung cancer.