TRANSFERRIN INCREASES ADHERENCE OF IRON-DEPRIVED NEISSERIA-GONORRHOEAE TO HUMAN ENDOMETRIAL CELLS

OBJECTIVE: Our purpose was to study the effects of iron deprivation wi th and without human transferrin supplementation on the adherence and invasion of Neisseria gonorrhoeae to human endometrial cells. STUDY DE SIGN: N. gonorrhoeae grown with or without iron was placed in media al one or media containing 2.5 mg/ml saturated human transferrin or unsat urated transferrin. N. gonorrhoeae was inoculated onto polarized human endometrial carcinoma cell (HEC I-B) monolayers, and at various inter vals monolayers were washed and incubated with media containing gentam icin or media alone. Colony-forming units per milliliter of N. gonorrh oeae associated with HEC 1-B cells were then determined. N. gonorrhoea e strains tested included both a transferrin receptor-positive (wild-t ype) and a transferrin receptor-negative mutant. Differences in percen t of original inoculum remaining at varying time points were analyzed by the Mann-Whitney U test. Transmission electron microscopy using a p rimary endometrial cell line was used to verify findings. RESULTS: Iro n-negative N. gonorrhoeae exhibited less adherence than did iron-posit ive N. gonorrhoeae. No difference in HEC 1-B adherence was seen when e ither saturated transferrin or unsaturated transferrin was added to th e iron-positive N. gonorrhoeae. With iron-negative N. gonorrhoeae addi tion of either saturated transferrin or unsaturated transferrin signif icantly increased N. gonorrhoeae adherence although unsaturated transf errin did not permit growth of iron-negative N. gonorrhoeae in tissue culture media alone. Transmission electron microscopy confirmed increa sed adherence of iron-negative N. gonorrhoeae supplemented with unsatu rated transferrin. An iron-negative N. gonorrhoeae mutant lacking the transferrin receptor exhibited no adherence regardless of addition of saturated transferrin or unsaturated transferrin. Invasion could not b e quantitated reliably because of persistence of gentamicin effect. CO NCLUSION: Iron and transferrin increased attachment of N. gonorrhoeae to human endometrial cells.