Components of intracellular pathogens are reduced, upon infection, to small peptides by the proteasome, and transported into the lumen of the endoplasmic reticulum (ER), to associate to molecules of the major histocompatibility complex (MHC); the aggregate leaves then the ER and is conducted, via Golgi, to the surface of the cell, where it can be recognized by receptors in cytotoxic T-lymphocytes (CTLs) and in natural killer (NK) cells. While the interaction with CTL receptors stimulates the cytotoxic activity, the lytic function of NK cells is inhibited by human leukocyte antigen class I (HLA-E) binding to inhibitory receptors belonging to C-type lectin like protein families expressed in the membrane of NK cells. Down-regulation of MHC-I molecules is a viral strategy for survival in the host. The open reading frame EP153R of African swine fever virus (ASFV) encodes a nonessential protein that has been involved in the control of the apoptotic process induced in ASFV-infected cells (1). The comparasion of this sequence with the bibliographic data confirmed the existence of a region homologue to C-type lectins in the viral protein. Protein pEP153R presents an intracellular amino extreme, a hydrophobic segment probably inserted in the plasma membrane and an extracelular region that contains the C-type lectin domain. The presence of a double lysine motif near the amino terminal (cytoplasmic) region configure an ER retrieval signal in the viral protein which might facilitate its interaction with nascent MHC-I molecules. The existence of cristalographic models of several C-type lectin molecules like CD69, CD94, Ly49A (2) allow us to model the 3D structure of the ASFV lectin in parallel with those decribed for the inhibitory NK cell receptors, and the possible interaction between pEP153R and MHC-I molecules.

Trabajo presentado en el 7th International Congress of Veterinary Virology, celebrado en Lisboa (Portugal) del 24 al 27 de septiembre de 2006.