Fibrocytes stimulate immune response for swine fever
Unexpected outbreaks of classical swine fever virus are partly due to the presence of piglets birthed from infected sows with subclinical symptoms. The high incidence of pig transport between countries and the presence of the virus in populations of wild boar may also be responsible for outbreaks in countries where eradication was assumed. The devastating effects of CSF provided the catalyst to develop marker vaccines as a means of provision of early protection. Project scientists based at the Institute of Virology and Immunoprophylaxis in Switzerland worked on the ability of antigen presenting cells to stimulate production of cytotoxic T lymphocytes. Among the cells in the immune system, dendritic cells are said to have the maximum potential to present antigens to T helper cells (known as CD4+ T cells). An immune response in the form of CD8+ mature cytotoxic T cells, appropriately also called killer cells, can then be achieved. To find viable alternatives to dendritic cells for vaccine production the team analysed the immune properties of another group of cells, fibrocytes. Fibrocytes were isolated from porcine blood and tested for their ability to stimulate cytotoxic T cells using a CSF virus model. The team found that they were potent stimulators of mature cytotoxic T cells (killer cells), interferon-gamma production and cytotoxic activity, therefore destroying virally infected cells. Use of fibrocytes has several advantages over the classic dendritic cell. First, they showed their immunostimulatory potential even when there was a low fibrocyte to T lymphocyte ratio. Under these circumstances, dendritic cells show less efficiency. Fibrocytes are also easily isolated and can retain their antigen presenting ability even as cultured secondary fibroblasts (when treated with interferon-gamma). Fibrocyte culture can be further used as a tool in proteomics and genomics and for the high-throughput screening of potential marker vaccines. As such, fibrocytes may well prove to be a useful part of the armoury against this virus and the havoc it can wreak in the pig industry.