Antibodies against HPA-1a
The present invention provides an isolated antibody that specifically binds to HPA-1a. Also provided is a nucleic acid molecule that encodes the antibody, and compositions comprising the antibody. Also provided is a method of producing the antibody and methods and uses which employ the antibody. Also provided are therapeutic uses of the antibody, for example in the treatment or prophylaxis of fetal and neonatal alloimmune thrombocytopenia (FNAIT).
1. An isolated antibody that specifically binds to HPA-1a and that comprises at least one heavy chain variable region that comprises three CDRs and at least one light chain variable region that comprises three CDRs, wherein said light chain variable region comprises:
(a) a variable light (VL) CDR1 that has the amino acid sequence of SEQ ID NO:8;
(b) a VL CDR2 that has the amino acid sequence of SEQ ID NO:9; and
(c) a VL CDR3 that has the amino acid sequence of SEQ ID NO: 10;
and wherein said heavy chain variable region comprises:
(d) a variable heavy (VH) CDR1 that has the amino acid sequence of SEQ ID NO:5;
(e) a VH CDR2 that has the amino acid sequence of SEQ ID NO:6; and
(f) a VH CDR3 that has the amino acid sequence of SEQ ID NO:7.
2. The antibody according to claim 1 , wherein said light chain variable region has the amino acid sequence of SEQ ID NO:4, or a sequence having at least 80% sequence identity thereto and/or wherein said heavy chain variable region has the amino acid sequence of SEQ ID NO:3, or a sequence having at least 80% sequence identity thereto.
3. The antibody according to claim 1 , wherein said light chain variable region has the amino acid sequence of SEQ ID NO:4 and said heavy chain variable region has the amino acid sequence of SEQ ID NO:3.
4. The antibody according to claim 1 , wherein said antibody is a full length IgG antibody.
5. The antibody according to claim 4 , wherein said antibody
(i) has a heavy chain that comprises the amino acid sequence of SEQ ID NO:21 or a sequence having at least 80% sequence identity thereto and/or a light chain that comprises the amino acid sequence of SEQ ID NO:22 or a sequence having at least 80% sequence identity thereto, or
(ii) has a heavy chain that comprises the amino acid sequence of SEQ ID NO:25 or a sequence having at least 80% sequence identity thereto and/or a light chain that comprises the amino acid sequence of SEQ ID NO:26 or a sequence having at least 80% sequence identity thereto.
6. The antibody according to claim 4 , wherein said antibody
(i) has a heavy chain that comprises the amino acid sequence of SEQ ID NO:21 and a light chain that comprises the amino acid sequence of SEQ ID NO:22, or
(ii) has a heavy chain that comprises the amino acid sequence of SEQ ID NO:25 and a light chain that comprises the amino acid sequence of SEQ ID NO:26.
7. The antibody according to claim 1 , wherein said antibody is capable of binding to αVβ3 integrin containing the HPA-1a antigen.
8. The antibody according to claim 1 , wherein said antibody remains at least 35% bound to a purified and immobilised αVβ3 integrin from HPA-1a positive individuals at the end of the dissociation period in a Surface Plasmon Resonance assay.
9. The antibody according to claim 1 , wherein said antibody binds to HPA-1a on intact platelets.
10. The antibody according to claim 1 , wherein said antibody is capable of binding to purified aIIbβ3 platelet integrin from HPA-1a positive individuals.
11. The antibody according to claim 1 , wherein said antibody is capable of inducing phagocytosis of HPA-1a positive platelets.
12. The antibody according to claim 1 , wherein said antibody does not inhibit aggregation of HPA-1bb platelets.
13. The antibody according to claim 1 , wherein said antibody has an abolished effector function.
14. A method of producing an antibody according to claim 1 , comprising the steps of
(i) culturing a host cell comprising one or more nucleic acid molecules comprising a nucleotide sequence that encodes an antibody according to claim 1 or one or more recombinant expression vectors comprising one or more of said nucleic acid molecules under conditions suitable for the expression of the encoded antibody; and
(ii) isolating or obtaining the antibody or protein from the host cell or from the growth medium/supernatant.
15. A method for analysing for the presence or absence of HPA-1a in a sample that has been obtained from a subject, said method comprising the steps of
(a) contacting said sample with an antibody according to claim 1 which binds specifically to HPA-1a; and
(b) analysing for the presence or absence of anti-HPA-1a antibody-HPA-1a (antigen) complexes.
16. A method of quantifying anti-HPA-1a antibodies in a sample in which method an antibody according to claim 1 is used as a reference standard.
17. The antibody according to claim 1 , wherein said antibody is not fucosylated.