Neisseria gonorrhoeae (Ngo) is a human obligate pathogen and is the main cause of ophthalmia neonatorum, a type of conjunctivitis in newborns of women infected with Ngo, which untreated can lead to blindness (1). One of the most important virulence factors of Ngo is the Type IV pilus, filamentous protein structures that facilitate the adhesion of the bacteria to the target tissue. In this project, we studied the importance of the Type IV pilus for Ngo adherence, infection and its outcome using cornea tissue models (2). We infected the models with MS11 Ngo derivatives: MS11 F3 (Pili+, RecA+), MS11 N159 (Pili+, RecA-, Adh+cornea) and MS11 N191 (Pili+, RecA-, Adh-cornea). We observed no significant difference in the tissue integrity between the non-infected and infected models. Measurements of the cell death by LDH method showed that the highest cytotoxicity was present after 72 h of infection in models infected with MS11 N159 Ngo. The bacterial adherence was also the highest for N159, which could be confirmed using fluorescence microscopy and SEM. Lastly, to analyze the outcome of the infection, the concentration of different important cytokines for infection was measured. IL-8 was the most secreted cytokine and was the highest in the samples infected with MS11 N159 for 72 h, suggesting a specific response that could be possibly receptor-dependent. These results show the importance of the functional Type IV pilus for the infection of the cornea tissue by Ngo, and its role not only for bacterial adherence but also on the outcome of the infection.

1. Tjia, K., van Putten, J., Pels, E., & Zanen, H. (1988). The interaction between Neisseria gonorrhoeae and the human cornea in organ culture. Ophtalmology, 341-345.
2. Lotz, C., et al. (2016). Alternative methods for the replacement of eye irritation testing. ALTEX - Alternatives to animal experimentation. 55-67.