Human cytomegalovirus gB polypeptide

A human cytomegalovirus (HCMV) immunogenic composition comprising:

• RNA formulated in a lipid nanoparticle,
• wherein the RNA encodes an amino acid sequence for a glycoprotein B (gB) protein comprising at least two amino acid mutations, and wherein said at least two amino acid mutations comprise:
• a) at least one engineered disulfide mutation selected from the group consisting of:
• D217C and Y589C, and M371C and W506C, numbered according to SEQ ID NO:1;
• and
• b) at least one additional mutation selected from the group consisting of:
• i) substitution of YIH at positions 155-157 with GHR;
• ii) substitution of W at position 240 with A;
• iii) substitution of C at position 246 with S;
• iv) substitution of P at position 655 with S;
• v) substitution of F at position 678 with S;
• vi) substitution of L at position 680 with T;
• vii) substitution of R at position 685 with A;
• viii) substitution of MIALDI (SEQ ID NO:
• 275) at positions 648-653 with GSGKDG (SEQ ID NO:
• 276);
• ix) substitution of R at position 693 with V;
• x) substitution of I at positions 767 and 768 with C;
• xi) substitution of D at position 703 and P at position 704 with C;
• and
• xii) substitution of Y at position 696 and V at position 697 with C,
• wherein the positions are numbered according to SEQ ID NO:
• 1.