Neisseria gonorrhoeae Coordinately Uses Pili and Opa To Activate HEC-1-B Cell Microvilli, Which Causes Engulfment of the Gonococci

Abstract

This study was undertaken to examine concomitant roles of pili and colony opacity-associated proteins (Opa) in promoting Neisseria gonorrhoeae adherence to and invasion of human endometrial HEC-1-B cells. Adherence of N. gonorrhoeae to cultured HEC-1-B cells was saturable, even though organisms adhered to <50% of the cells. During 4 to 6 h of incubation, adherent mono- and diplococci formed microcolonies on the surfaces of the cells. Microvilli of the HEC-1-B cells adhered by their distal ends to individual cocci within the microcolonies. When the microcolonies grew from isogenic pilus-negative (P−) Opa−, P− Opa+, or P+ Opa−gonococci, microvilli did not elongate, and the colonies were not engulfed. In contrast, the microvilli markedly elongated during exposure to P+ Opa+ gonococci. The microvilli adhered to the organisms along their full lengths and appeared to actively participate in the engulfment of the microcolonies. Internalized microcolonies, with P+ Opa+gonococci, contained dividing cocci and appeared to be surrounded by cell membrane but were not clearly within vacuoles. In contrast, degenerate individual organisms were within vacuoles. Low doses of chloramphenicol, which inhibits protein synthesis by both prokaryotes and eukaryotes, prevented the microvillar response to and internalization of the P+ Opa+ gonococci; higher doses caused internalization without microvillus activation. Cycloheximide and anisomycin, which inhibit only eukaryotic protein synthesis, caused dose-dependent enhancement of uptake. Cytochalasins reduced engulfment; colchicine had no effect. These results show that gonococci must express both pili and Opa to be engulfed efficiently by HEC-1-B cells.

CEACAM is not necessary for Neisseria gonorrhoeae to adhere to and invade female genital epithelial cells

“…We have used HEC-1-B cells to study how gonococci invade cervical cells (Griffiss et al, 1999). Invasion of HEC-1-B cells by MS11 MK organisms requires that the bacteria be piliated and express both Opa and paraglobosyl LOS (Griffiss et al, 1999;Wang et al, 1996).…”

“…We have used HEC-1-B cells to study how gonococci invade cervical cells (Griffiss et al, 1999). Invasion of HEC-1-B cells by MS11 MK organisms requires that the bacteria be piliated and express both Opa and paraglobosyl LOS (Griffiss et al, 1999;Wang et al, 1996). In the current study, we investigated whether Opa proteins were engaging CEACAM molecules on the surface of HEC-1-B cells during invasion but found no evidence of CEACAM expression by these cells.…”

“…Several cell lines were chosen to represent the different sites that gonococci readily infect. These included four primary cultures, two of fallopian tube epithelial cells and two of cervical epithelial cells, four different fallopian tube tissue samples and three malignant cell lines that have been used widely for studies of gonococcal invasion in vitro (Williams et al, 1998;Griffiss et al, 1999;Jarvis et al, 1999). We demonstrate that CEACAM is not expressed by all cell lines of female genital origin that are susceptible to gonococcal invasion.…”

“…Gonoccal invasion of HEC-1-B cells in the presence of serum proceeds only when gonococci express both pili and Opa (Griffiss et al, 1999). As ME180 cells differ from HEC-1-B cells in that they express CEACAMs, we examined how pili and Opa expression affected gonococcal invasion of ME180 cells.…”

“…We previously have used HEC-1-B cells to study gonococcal invasion of female genital epithelial cells (Griffiss et al, 1999). Gonococcal invasion of HEC-1-B cells is a complicated process that involves cooperation between the bacteria and the host cells, but Opa expression alone is not sufficient to direct internalization by the eukaryotic cells (Griffiss et al, 1999). This would seem to suggest that the Opa:CEACAM model does not explain invasion of this cell line.…”