Modified HIV peptides, antigens, compositions, immunoassay kit and a method of detecting antibodies induced by HIV

An isolated peptide from HIV-1 Gag p24 protein, which comprises at least one amino acid sequence which contains modifications compared with the native sequence and is selected from the group consisting of:

• Xaa1 Xaa2 Xaa3 Xaa4 Xaa5 Xaa6 Xaa7 Gly Xaa9 Leu Val Xaa12 Xaa13 Xaa14 Tyr Xaa16 Xaa17 Xaa18 Xaa19 Xaa20 Xaa21 Xaa22 Xaa23 Ala Xaa25 Xaa26 Xaa27 Xaa28 (SEQ ID NO:
• 4), wherein
• Xaa1 is Pro, Tyr or Phe,
• Xaa2 is Ile, Val or Leu,
• Xaa3 is Ile, Leu, Val, Ala or Met,
• Xaa4 is Gln, Ser, Thr or Val,
• Xaa5 is Asn, Asp or Thr,
• Xaa6 is Ile, Ala, Leu or Met,
• Xaa7 is Gln, Glu, Lys or Gly,
• Xaa9 is Gln or Ile,
• Xaa12 is none,
• Xaa13 is none,
• Xaa14 is none,
• Xaa16 is Ala, Ser, Asn, Val or Pro,
• Xaa17 is Ile, Leu, Met or Val,
• Xaa18 is Ser or Thr,
• Xaa19 is Pro or Ala,
• Xaa20 is Arg or Lys,
• Xaa21 is Thr or Ser,
• Xaa22 is Leu or Ser,
• Xaa23 is Asn, Phe or Val,
• Xaa25 is Trp, Tyr, Gly or none,
• Xaa26 is Val, Leu, Gly or none,
• Xaa27 is Lys, Arg, Gly or none,
• Xaa28 is Val, Ala, Cys, Gly or none;
• Xaa1 Ala Xaa3 Xaa4 Xaa5 Ala Xaa7 Xaa8 Xaa9 Leu Leu Xaa12 Xaa13 Xaa14 Xaa15 Xaa16 Xaa17 Xaa18 Xaa19 His Gln Xaa22 Ala Xaa24 Xaa25 (SEQ ID NO:
• 9), wherein
• Xaa1 is Tyr, Trp, Phe or Gly,
• Xaa3 is Thr, Ala, Val, Ile or Leu,
• Xaa4 is Pro or Ser,
• Xaa5 is Gln, His, Gly, Thr, Ser or Tyr,
• Xaa7 is Leu, Ile or Val,
• Xaa8 is Asn or Tyr,
• Xaa9 is Thr, Met, Leu or Ala,
• Xaa12 is Ser, Thr or Asn,
• Xaa13 is Thr, Ile, Val or Ala,
• Xaa14 is Val or Ile,
• Xaa15 is none,
• Xaa16 is none,
• Xaa17 is none,
• Xaa18 is Gly or none,
• Xaa19 is Gly or none,
• Xaa22 is Ala or Gly,
• Xaa24 is Met, Leu, Cys or none,
• Xaa25 is Gln, Glu, His, Gly or none;
• Xaa1 Xaa2 Ala Leu Ala Gly Xaa7 Xaa8 Xaa9 Leu Xaa11 Xaa12 Xaa13 Xaa14 Xaa15 Xaa16 Xaa17 Xaa18 Xaa19 Xaa20 Xaa21 (SEQ ID NO:
• 15), wherein
• Xaa1 is Trp or Tyr,
• Xaa2 is Ser or Ala,
• Xaa7 is Thr, Ala or Ser,
• Xaa8 is Ser or Thr,
• Xaa9 is Ser or Thr,
• Xaa11 is Leu, Pro, Val or Gln,
• Xaa12 is Gin, Ala or His,
• Xaa13 is Glu or Gly,
• Xaa14 is Gin or His,
• Xaa15 is Ile, Leu, Val or Met,
• Xaa16 is Gly, Ala, Gln, Thr, Asn, Arg, His or Ile,
• Xaa17 is Trp or Tyr,
• Xaa18 is Thr, Met, Leu or Ile,
• Xaa19 is Thr or Ser,
• Xaa20 is Cys, Gly or none,
• Xaa21 is Gly or none
• wherein the terminal ends of the sequences may be free carboxyl- or amino groups, amides, acyls, acetyls or salts thereof,
• two or more of the Cys residues may form part of an interchain disulphide binding, a —S—(CH2)p—S— or a —(CH2)p—-bridge wherein p=1-8 optionally intervened by one or more hetero atoms such as O, N and S and/or the said peptide sequences are immobilized to a solid support.