A modified HCMV pentamer complex comprising: (a) a pUL128 polypeptide that has cysteine at residue 142, numbered with respect to SEQ ID NO: 13, and a pUL130 polypeptide that has a cysteine at residue 95, numbered with respect to SEQ ID NO: 17; (b) a gL polypeptide that has a phenylalanine at residue 140, numbered with respect to SEQ ID NO: 7; (c) a gL polypeptide that has a leucine at residue 145, numbered with respect to SEQ ID NO: 7; (d) a gL polypeptide that has a cysteine at residue 150, numbered with respect to SEQ ID NO: 7, and a pUL130 polypeptide that has a cysteine at residue 64, numbered with respect to SEQ ID NO: 17; (e) a pUL128 polypeptide that has a cysteine at residue 83, numbered with respect to SEQ ID NO: 13, and a pUL130 polypeptide that has a cysteine at residue 167, numbered with respect to SEQ ID NO: 17; (f) a gL polypeptide that has a cysteine at residue 160, numbered with respect to SEQ ID NO: 7, and a pUL130 polypeptide that has a cysteine at residue 56, numbered with respect to SEQ ID NO: 17; (g) a gL polypeptide that has a cysteine at residue 166, numbered with respect to SEQ ID NO: 7, and a pUL130 polypeptide that has a cysteine at residue 62, numbered with respect to SEQ ID NO: 17; (h) a pUL128 polypeptide that has a cysteine at residue 98, numbered with respect to SEQ ID NO: 13, and a pUL130 polypeptide that has a cysteine at residue 204, numbered with respect to SEQ ID NO: 17; (i) a pUL131 polypeptide that has a phenylalanine at residue 86, numbered with respect to SEQ ID NO: 21; (j) a pUL128 polypeptide that has a cysteine at residue 48 and a cysteine at residue 107, numbered with respect to SEQ ID NO: 13; (k) a pUL128 polypeptide that has an isoleucine at residue 77, numbered with respect to SEQ ID NO: 13; (l) a pUL128 polypeptide that has an isoleucine at residue 103, numbered with respect to SEQ ID NO: 13; or (m) combinations thereof. (a) a pUL128 polypeptide that has cysteine at residue 142, numbered with respect to SEQ ID NO: 13, and a pUL130 polypeptide that has a cysteine at residue 95, numbered with respect to SEQ ID NO: 17; (b) a gL polypeptide that has a phenylalanine at residue 140, numbered with respect to SEQ ID NO: 7; (c) a gL polypeptide that has a leucine at residue 145, numbered with respect to SEQ ID NO: 7; (d) a gL polypeptide that has a cysteine at residue 150, numbered with respect to SEQ ID NO: 7, and a pUL130 polypeptide that has a cysteine at residue 64, numbered with respect to SEQ ID NO: 17; (e) a pUL128 polypeptide that has a cysteine at residue 83, numbered with respect to SEQ ID NO: 13, and a pUL130 polypeptide that has a cysteine at residue 167, numbered with respect to SEQ ID NO: 17; (f) a gL polypeptide that has a cysteine at residue 160, numbered with respect to SEQ ID NO: 7, and a pUL130 polypeptide that has a cysteine at residue 56, numbered with respect to SEQ ID NO: 17; (g) a gL polypeptide that has a cysteine at residue 166, numbered with respect to SEQ ID NO: 7, and a pUL130 polypeptide that has a cysteine at residue 62, numbered with respect to SEQ ID NO: 17; (h) a pUL128 polypeptide that has a cysteine at residue 98, numbered with respect to SEQ ID NO: 13, and a pUL130 polypeptide that has a cysteine at residue 204, numbered with respect to SEQ ID NO: 17; (i) a pUL131 polypeptide that has a phenylalanine at residue 86, numbered with respect to SEQ ID NO: 21; (j) a pUL128 polypeptide that has a cysteine at residue 48 and a cysteine at residue 107, numbered with respect to SEQ ID NO: 13; (k) a pUL128 polypeptide that has an isoleucine at residue 77, numbered with respect to SEQ ID NO: 13; (l) a pUL128 polypeptide that has an isoleucine at residue 103, numbered with respect to SEQ ID NO: 13; or (m) combinations thereof.