This disclosure provides an isolated human cytomegalovirus (HCMV) membrane protein complex, wherein said complex comprises gH, gL and at least one more HCMV glycoprotein. In some embodiments the complex consists of gH,gL and gO. In other embodiments the complex consists of gH, gL, p UL128, p UL130 and p UL131A. The disclosure also provides processes for expressing and purifying said complexes, and subsequent uses of said complexes in immunogenic compositions and vaccines.