Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

A culture system for efficient stimulation of virus-specific cytotoxic T lymphocytes

Antigen presenting cells (APC) with potent immunostimulatory capacities are the critical targets when developing novel vaccines and immunotherapies against infectious diseases and cancer. Although several cell types have the potential for antigen presentation to stimulate T cells, DC are considered to be most potent in this function. In this project we have identified an alternative source of APC for antigen presentation studies with a number of advantages: the fibrocytes.

These cells represent a population of circulating leukocytes reported to be capable of presenting antigen to CD4+ T lymphocytes. We have isolated fiborcates from porcine blood and demonstrated their ability to stimulate CTL responses using a classical swine fever virus (CSFV) model. The isolated fibrocytes displayed the phenotype previously reported for mouse and human Fb, particularly in terms of the surface proteins necessary for antigen presentation - MHC class I and class II, CD80/86. These primary fibrocytes efficiently endocytosed and degraded antigen. In absence of exogenous stimuli, both endocytosis and MHC class II expression were lost when the fibrocytes were passaged and cultured. Treatment of such secondary Fb with IFN-g restored the MHC class II expression. Both the primary and secondary fibrocytes were efficient stimulators of virus-specific CD8+CTL was measured in terms of CD8+ T cell proliferation, IFN-g production and cytotoxic activity. This was noted even at low fibrocyte/T lymphocyte ratios, at which DC were less efficient.

Our results demonstrated that fibrocytes are potent accessory cells for the induction of specific antiviral immunity, particularly with respect to activating virus-specific CD8+ CTL at low Fb/T lymphocyte ratio. Consequently, fibrocytes may prove to be a potent tool for vaccine and immunotherapy research, especially considering their ease of isolation from the blood and adaptability to in vitro expansion (secondary Fb) while retaining APC functionality.

This culture system can be used for the following purposes:
1. Determination of the relative capacity of different vaccines to stimulate cytotoxic T-cell responses in vitro.
2. Identification of genes encoding for proteins, which contain T-cell epitopes.
3. Identification of the T-cell epitopes
4. High-throuput in vitro screening of vaccine candidates.

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