The Immunostimulatory Capacity of Nontypeable Lipooligosaccharide.

BACKGROUND

We have recently found that lipooligosaccharide (LOS) isolated from encapsulated strains of () has strong adjuvant, but diminished pro-inflammatory ability as compared to lipopolysaccharide (LPS). In this study, we aimed to determine the immunostimulatory capacity of nontypeable/ non-encapsulated (NTHi) LOS by comparing the effect of killed bacteria with LOS isolated from the same strain.

METHODS

Following stimulation of human monocytic THP-1 cells with killed NTHi strain 375, or with the corresponding amount of LOS, we studied the protein and gene expression of immunostimulatory and antigen-presenting molecules, cytokines, and innate immune receptors.

RESULTS

Stimulation with LOS resulted in lower expression of adhesion (CD54, CD58) as well as costimulatory molecules (CD40, CD86), but in higher expression of antigen-presenting molecules (HLA-DR and HLA-ABC) compared to killed NTHi, whereas killed bacteria induced higher release of both TNF-α and IL-10. The results indicate that while LOS of NTHi has decreased capacity to induce pro-inflammatory responses compared to LPS or killed NTHi, this LOS has the potential to facilitate antigen presentation.

CONCLUSIONS

Considering the important role of NTHi as a respiratory pathogen, and its currently increasing significance in the etiology of invasive infections, LOS deserves further attention as a vaccine antigen, which also has potent adjuvant properties.