FUNCTIONAL-CHARACTERIZATION OF THE C-C CHEMOKINE-LIKE MOLECULES ENCODED BY MOLLUSCUM CONTAGIOSUM VIRUS TYPE-1 AND TYPE-2

Many viruses have evolved mechanisms for evading the host immune syste m by synthesizing proteins that interfere with the normal immune respo nse, The poxviruses are among the most accomplished at deceiving their hosts' immune systems, The nucleotide sequence of the genome of the h uman cutaneous poxvirus, molluscum contagiosum virus (MCV) type 1, was recently reported to contain a region that resembles a human chemokin e, We have cloned and expressed the chemokine-like genes from MCV type 1 and the closely related MCV type 2 to determine a potential role fo r these proteins in the viral life cycle, In monocyte chemotaxis assay s, the viral proteins have no chemotactic activity but both viral prot eins block the chemotactic response to the human chemokine, macrophage inflammatory protein (MIP)-1 alpha. Like MIP-1 alpha, both viral prot eins also inhibit the growth of human hematopoietic progenitor cells, but the viral proteins are more potent in this activity than the human chemokine, These viral chemokines antagonize the chemotactic activity of human chemokines and have an inhibitory effect on human hematopoie tic progenitor cells, We hypothesize that the inhibition of chemotaxis is an immune evasion function of these proteins during molluscum cont agiosum virus infection. The significance of hematopoietic progenitor cell inhibition in viral pathogenesis is uncertain.