In vitro analysis of the invasive properties of Campylobacter jejuni.

Abstract

A HEp-2 cell culture model was used to investigate the invasive properties of Campylobacter species. Two of twenty-five Campylobacter isolates did not invade HEp-2 cells, and one of these isolates did not adhere to the epithelial cells. Penetration of HEp-2 epithelial cells by C. jejuni was significantly (P < 0.05) inhibited with C. jejuni lysates and a MAb (1B4) in competitive inhibition studies. Immunogold electron microscopic studies revealed that the 1B4 MAb bound to the flagella and cell surface of low passage (invasive) C. jejuni M 96, whereas only the flagella of high passage (non-invasive) C. jejuni were labelled. Western blot analysis revealed that the 1B4 MAb identified an epitope on antigens ranging in size from 66 to 44 kDa in invasive and non-invasive organisms. Antigens were also recognized in lysates prepared only from invasive strains from 42 to 38 kDa. Sodium meta-periodate chemical treatment of C. jejuni lysates significantly (P < 0.05) affected its inhibitory capacity. Additionally, proteinase K and sodium meta-periodate treatment of lysates changed the mobility of antigens recognized by the 1B4 MAb. This suggests that the antigens required for epithelial cell penetration by C. jejuni may be glycoprotein in nature and that the functional binding site is dependent upon an intact carbohydrate moiety. Co-infection of HEp-2 epithelial cells with coxsackievirus B3, echovirus 7, polio virus (LSc type 1), porcine enterovirus and Campylobacter isolates was performed to determine if a synergistic effect could be obtained. The invasiveness of C. jejuni was significantly increased for HEp-2 cells pre-infected with echovirus 7, coxsackievirus B3, and UV-inactivated (non-infectious) coxsackievirus B3 particles. Polio and porcine enterovirus had no effect on C. jejuni adherence and invasiveness. C. hyointestinalis and C. mucosalis, two non-invasive isolates, did not invade virus-infected HEp-2 cells. The increase of invasiveness of C. jejuni appears to be the result of specific interactions between the virus and the HEp-2 cell membrane. The data suggest that the invasiveness of Campylobacter is dependent upon the inherent properties of the organism. Virus-induced cell alterations can potentiate the invasiveness of virulent Campylobacter but are not sufficient to allow internalization by non-invasive bacteria.