An isolated human cytomegalovirus (HCMV) membrane protein complex that comprises gH, gL and at least one more HCMV glycoprotein is provided. In some embodiments the complex consists of gH, gL and gO. In other embodiments the complex consists of gH, gL, pUL128, pUL130 and pUL131A. Processes for expressing and purifying such complexes, and subsequent uses of such complexes in immunogenic compositions and vaccines, are also provided.