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Microb Pathog. 2018 Nov;124:38-46. doi: 10.1016/j.micpath.2018.08.015. Epub 2018 Aug 14.

Gamma-irradiation-killed Streptococcus pneumoniae potently induces the expression of IL-6 and IL-8 in human bronchial epithelial cells.

Author information

1
Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul, 08826, Republic of Korea.
2
Research Division for Biotechnology, Korea Atomic Energy Research Institute, Jeongeup, 56212, Republic of Korea.
3
Department of Agricultural Biotechnology and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, 08826, Republic of Korea.
4
Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul, 08826, Republic of Korea. Electronic address: shhan-mi@snu.ac.kr.

Abstract

Streptococcus pneumoniae is a major respiratory pathogen that can cause pneumonia, meningitis, and otitis media. Although capsular polysaccharide-based vaccines are commercially available, there is a need for broad-spectrum, serotype-independent, and cost-effective vaccines. Recently, an intranasal vaccine formulated with gamma-irradiated nonencapsulated S. pneumoniae whole cells has been developed and its immunogenicity is under investigation. Since innate immunity influences the subsequent adaptive immunity, in the present study, we investigated the immunostimulatory activity of gamma-irradiated S. pneumoniae (r-SP) in the human bronchial epithelial cell-line, BEAS-2B, by comparing with heat-inactivated S. pneumoniae (h-SP) and formalin-inactivated S. pneumoniae (f-SP). r-SP potently induced interleukin (IL)-6 and IL-8 at both mRNA and protein levels in a dose- and time-dependent manner, whereas h-SP and f-SP poorly induced them. Of note, the mRNA levels of IL-6 and IL-8 were approximately two-fold higher when cells were stimulated with 3 × 107 CFU/ml of r-SP for 3 h, while the protein levels of IL-6 and IL-8 were approximately five-fold higher after stimulation with 3 × 107 CFU/ml of r-SP for 24 h. Furthermore, r-SP exhibited potent activation of Toll-like receptor 2 compared with h-SP or f-SP. The expression of IL-6 and IL-8 induced by r-SP was mediated through the activation of mitogen-activated protein kinases. Remarkably, when r-SP was further treated with heat or formalin, there was a decrease in the aforementioned activities. Taken together, we suggest that r-SP stimulates the human respiratory epithelial cells to produce the cytokines IL-6 and IL-8, which might influence the induction of adaptive immune responses.

KEYWORDS:

BEAS-2B; Gamma-irradiation; Innate immunity; Streptococcus pneumoniae; Vaccine

PMID:
30114464
DOI:
10.1016/j.micpath.2018.08.015
[Indexed for MEDLINE]

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