Cytomegaloviruses manipulate the host
chemokine/receptor axis by altering cellular
chemokine expression and by encoding multiple
chemokines and
chemokine receptors. Similar to human cytomegalovirus (HCMV), rat cytomegalovirus (RCMV) encodes multiple
CC chemokine-analogous
proteins, including r129 (HCMV UL128 homologue) and r131 (HCMV UL130 and MCMV m129/130 homologues). Although these
proteins play a role in CMV entry, their function as
chemotactic cytokines remains unknown. In the current study, we examined the role of the RCMV
chemokine r129 in promoting cellular migration and in accelerating transplant vascular
sclerosis (TVS) in our rat heart transplant model. We determined that r129
protein is released into culture supernatants of infected cells and is expressed with late viral gene kinetics during RCMV
infection and highly expressed in heart and salivary glands during in vivo rat
infections. Using the recombinant r129
protein, we demonstrated that r129 induces migration of lymphocytes isolated from rat peripheral blood, spleen, and bone marrow and from a rat macrophage cell line. Using antibody-mediated cell sorting of rat splenocytes, we demonstrated that r129 induces migration of naïve/central memory CD4(+) T cells. Through
ligand-binding assays, we determined that r129 binds rat
CC chemokine receptors CCR3, CCR4, CCR5, and CCR7. In addition, mutational analyses identified functional domains of r129 resulting in
recombinant proteins that fail to induce migration (r129-ΔNT and -C31A) or alter the chemotactic ability of the
chemokine (r129-F43A). Two of the
mutant proteins (r129-C31A and -ΔNT) also act as dominant negatives by inhibiting migration induced by wild-type r129. Furthermore,
infection of rat heart transplant recipients with RCMV containing the r129-ΔNT mutation prevented CMV-induced acceleration of TVS. Together our findings indicate that RCMV r129 is highly chemotactic, which has important implications during RCMV
infection and reactivation and acceleration of TVS.