Updated project metadata. Human cytomegalovirus (HCMV) is a widespread virus and can establish life-long latent infection in large populations. In order to establish persistent and latent infection in healthy individuals, HCMV encodes a large array of proteins that can modulate different components and pathways of host cells. It has been reported that pUL138 encoded by UL133-UL138 polycistronic locus promotes a latent infection in primary CD34+ HPCs infected in vitro. In this study, a recombinant HCMV, namely HanUL138del, was constructed by deleting the UL138 locus of Han, a clinic HCMV strain. Then a comparative quantitative proteomic analysis of Han and HanUL138del infected MRC5 cells was performed, aiming to study the effect of pUL138 on host cell in the context of HCMV infection. Our result indicated that at the early phase of HCMV infection, innate immune response was differentially activated, while at late phase of HCMV infection, multiple host proteins were differentially expressed, between Han or HanUL138del infected cells.