Inhibition of macrophage inflammatory protein-1α production by Epstein-Barr virus

Infection with Epstein-Barr virus (EBV) exerts substantially immunomodulating activities in vitro and in vivo. In this context, EBV-induced chemokine production and the influence of EBV on this highly redundant system of inflammatory proteins have hardly been investigated. This study analyzed the production of interleukin-8, RANTES, monocyte chemotactic protein-1, and macrophage inflammatory protein-1α (MIP-1α) on EBV infection of peripheral blood mononuclear cells from immune EBV-seropositive (EBV⁺) and noninfected EBV-seronegative (EBV^-) individuals. EBV failed to induce the production of MIP-1α in EBV⁺ as well as EBV^- individuals, whereas the other chemokines studied were readily expressed. Moreover, EBV completely down-regulated lipopolysaccharide (LPS)- and phytohemagglutinin-induced MIP-1α production up to 4 hours after induction. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of EBV- and LPS-stimulated cultures revealed that EBV inhibited MIP-1α production on the transcriptional level. This effect was abolished by addition of antiglycoprotein (gp)350/220, a monoclonal antibody against EBV's major envelope glycoprotein, which mediates binding of the virus to the EBV receptor, CD21. However, recombinant gp350/220 protein alone did not inhibit the LPS-induced MIP-1α production, indicating that infection of the target cell is indispensable for this effect. In summary, we demonstrate a new immunomodulating activity of EBV on the chemokine system that probably helps the virus to evade the host's immune system favoring lifelong infection.