MASP-2, a complement-fixing enzyme, and uses for it

1. A method for treating patients deficient in activity of Mannan-binding lectin Associated Serine Protease-2 (MASP-2) which renders an individual susceptible to one or more infections or incapable of neutralizing an established infection, said method comprising administering to the patient a polypeptide comprising an amino acid sequence at least 95% identical to the sequence defined by position 16 to position 686 of SEQ ID:2, wherein said polypeptide has at least one of the following activities:

i) cleavage of C4 and activation of the complement in an in vitro assay for MBLectin complement pathway function; and/or

ii) mannan-binding lectin (MBL) associating activity.

2. The method according to claim 1 , wherein the polypeptide comprises a sequence which, when aligned with the sequence defined by position 16 to position 686 of SEQ ID:2, is identical to the sequence defined by position 16 to position 686 of SEQ ID:2 at each of the positions 28, 32, 33, 36, 39, 44, 52, 54, 59, 61, 67, 69, 72, 74, 75, 77, 90, 91, 101, 117, 120, 122–124, 129, 130, 132, 134, 136, 138, 141, 142, 152, 154, 156, 158, 161, 162, 165–167, 171, 173, 180, 184, 185, 190, 194, 198, 202, 205, 206, 211, 213, 215, 218, 220, 231, 232, 241, 244, 256, 259, 260, 264, 269, 271, 278, 281, 284, 289, 290, 293, 300, 301, 318, 322, 328, 331, 344, 348, 352, 354, 361, 365, 366, 369, 375, 392, 394, 396, 401, 403, 408, 410, 412, 416, 418, 428, 430, 432–435, 444, 445, 448, 451, 457, 458, 470, 472, 477, 480–483, 529, 532, 534, 535, 538, 550–554, 571, 572, 574, 585, 591, 598, 616, 618–620, 627, 629, 631–635, 638–640, 660, 666, 667, 669, 678 and 679 of SEQ ID NO:2.

3. The method according to claim 1 , wherein the differences between the sequence of the polypeptide and the sequence defined by position 16 to position 686 of SEQ ID:2 are limited to conservative amino acid substitutions selected from the group of substitution sets consisting of

Gly/Ala,

Val/ lle/Leu,

Asp/Glu,

Asn/Gln,

Ser/Thr,

Lys/Arg, and

Phe/Tyr.

4. The method according to claim 1 , wherein said polypeptide has the activities of cleavage of C4 and activation of the complement in an in vitro assay for MBLectin complement pathway function, and mannan-binding lectin (MBL) associating activity.

5. The method according to claim 1 wherein said MASP-2 deficiency is determined by conducting one or more assays selected from the group consisting of

i) an assay of in vitro activation of complement factor 4 (C4) in the presence of MASP-free mannan binding lectin with MBL/MASP-depleted serum, and

ii) an in vitro assay of complement system activation by whole serum in the presence of 2.0M NaCl.

6. The method according to claim 1 wherein said administration is conducted by intravenous infusion of a composition comprising MASP-2.