Viral protein K5 modulates T cell costimulation

Herpesviruses use elaborate strategies to establish themselves in their host including evading, destroying or redirecting immune cells. In June 15 Journal of Clinical Investigation, Coscoy and Ganem describe how viral proteins from human herpesvirus associated with Kaposi's sarcoma impair B cells ability to induce the protective response of cytotoxic T lymphocytes.

Coscoy and Ganem examined the ability of two viral genes K3 and K5 to influence the disposition of host surface proteins implicated in immune recognition and activation. They found that K5, but not K3, expression in B cells dramatically reduces ICAM-1 and B7-2 surface expression causing them to be internalized rapidly and routed to the lysosome. This downregulation is functionally significant, because K5-transfected B cells show substantial impairment in their ability to induce T cell activation (J Clin Invest 2001, 107:1599-1606).

K5 is thus the first example of a viral modulator of immunological synapse formation...