Human cytomegalovirus (HCMV) remains latent in cells of the myeloid lineage after primary infection. The THP-1 monocytic cell line is conditionally permissive for infection and has been used primarily to study the process of HCMV reactivation when the cells are induced to differentiate. In the present report, we characterized lytic infection in THP-1 derived macrophages using two strains of HCMV, Towne and BAC-derived TR. Our findings indicate that these cells express viral genes of all three kinetic classes and produce extracellular virus, but that there is a delay in these processes relative to productively infected fibroblasts. Importantly, our studies in THP-1 derived macrophages revealed strain-specific differences in pp65 trafficking and actin dynamics. Based on these observations, our studies indicate that differentiated THP-1 cells can serve as a valuable model for lytic infection.
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