Development of in vitro models to study bacterial interactions with lymphoid tissue-associated epithelial cells

Many bacteria are found in the noses and throats of healthy individuals, but some bacteria such as meningococci, haemophilus and moraxella can cause serious diseases ranging from localised ear, throat and lung infections to widespread blood and brain infections (septicaemia and meningitis). They can affect both the young and the old. Although some vaccines to prevent infections caused by different strains of these bacteria are available, there is still a need for vaccines to prevent infections caused by the remaining problematic bacteria such as group B meningococci, some haemophilus species and moraxella strains. To identify effective vaccine candidates, we need to identify basic mechanisms by which bacteria cause disease. Several investigators have examined how the bacteria attach to and invade human cells lining the throat (epithelial cells) by using isolated cells grown in laboratory cultures. However, increasing numbers of studies have shown that the cells that the bacteria colonise, especially around the tonsils in the throat, possess different properties to those grown under simple laboratory culture conditions. In this study, we propose to use complex culturing methods to mimic the environment that epithelial cells experience in the body. These cellular models will help us to understand better the bacterial and host components that are involved in attachment and invasion by the pathogens. Such model systems also have a wider application for studies on other pathogens. The more complete knowledge of the precise mechanisms that underlie the processes of human barrier penetration is expected to generate information that will allow us to produce better therapeutic and other intervention / prevention strategies against respiratory tract pathogens.

The specialised epithelia of the mucosa-associated lymphoid tissues (MALT) represent key and strategic sites for antigen sampling and presentation to the underlying organised lymphoid tissues. Besides their vital role in the initiation of immune responses, they constitute sites of colonisation and infection of a number of mucosal pathogens. The nasal-associated lymphoid tissue (NALT) is a collection of lymphoid structures arranged in a ring (Waldeyer s ring) round the wall of the throat, at the common gateway to the gut and the respiratory tract. This collection includes palatine, adenoidal, lingual and tubal tonsils, and forms a colonisation niche for many commensals and potential pathogens. The bacterial species include commensals such as Neisseria meningitidis that have the potential to cause serious disseminated infections as well as Haemophilus influenzae and Moraxella catarrhalis strains which are increasingly developing antibiotic resistance. Understanding bacterial mechanisms of attachment at these sites are of primary importance for developing strategies to control infection caused by them. However, no suitable in vitro models are available to assess the parameters that determine bacterial interactions with the specialised lymphoepithelial structures. The aim of this study is to develop an in vitro model of respiratory epithelial origin, based on the approach used for gut epithelial cells, in which epithelial cells are co-cultured with B lymphocytes, to generate cells differentiated in the context of a lymphoid environment. In this pilot study, we aim to assess microscopic and biochemical characteristics of cell lines so cultured. The models will facilitate future studies on microbial colonisation mechanisms as well as on vaccine delivery systems.