Treatment of complement-associated disorders

#The present invention concerns a recently discovered macrophage specific receptor, CRIg (earlier referred to as STIgMA), and its use in the prevention and/or treatment of complement-associated disorders, including complement-associated eye conditions, such as age-related macular degeneration (AMD) and choroidal neovascularization (CNV).

#The complement system is a complex enzyme cascade made up of a series of serum glycoproteins, that normally exist in inactive, pro-enzyme form. Three main pathways, the classical and the alternative pathway, can activate complement, which merge at the level of C3, where two similar C3 convertases cleave C3 into C3a and C3b. An additional pathway, the mannose-binding lectin (MBL) pathway has also been described.

#Classical pathway components are labeled with a C and a number (e.g. C1, C3). Because of the sequence in which they were identified, the first four components are numbered C1, C4, C2, and C3. Alternative pathway components are lettered (e.g. B, P, D). Cleavage fragments are designated with a small letter following the designation of the component (e.g. C3a and C3b are fragments of C3). Inactive C3b is designated iC3b. Polypeptide chains of complement proteins are designated with a Greek letter after the component (eg, C3α and C3β are the α- and β-chains of C3). Cell membrane receptors for C3 are abbreviated CR1, CR2, CR3, and CR4.

#FIGS. 1A-1B show the nucleotide and amino acid sequences of a 321-amino acid human CRIg polypeptide (SEQ ID NOS: 1 and 2, respectively).

#FIGS. 2A-2B show the nucleotide and amino acid sequences of the 399-amino acid full-length long form of native human CRIg (huCRIg or huCRIg-long; SEQ ID NOS: 3 and 4, respectively).

#FIGS. 3A-3B show the nucleotide and amino acid sequences of the 305-amino acid short form of native human CRIg (huCRIg-short, SEQ ID NOS: 5 and 6, respectively).

#The terms “PRO362,” “JAM4,” “STIgMA,” and “CRIg” are used interchangeably, and refer to native sequence and variant CRIg polypeptides.

#A “native sequence” CRIg, is a polypeptide having the same amino acid sequence as a CRIg polypeptide derived from nature, regardless of its mode of preparation. Thus, native sequence CRIg can be isolated from nature or can be produced by recombinant and/or synthetic means. The term “native sequence CRIg”, specifically encompasses naturally-occurring truncated or secreted forms of CRIg (e.g., an extracellular domain sequence), naturally-occurring variant forms (e.g., alternatively spliced forms) and naturally-occurring allelic variants of CRIg. Native sequence CRIg polypeptides specifically include the 321 amino acids long human CRIg polypeptide of SEQ ID NO: 2 (shown in FIG. 1), with or without the N-terminal signal sequence, with or without the initiating methionine at position 1, and with or without any or all of the transmembrane domain at about amino acid positions 277 to 307 of SEQ ID NO: 2. Native sequence CRIg polypeptides further include the full-length 399 amino acids long human CRIg polypeptide of SEQ ID NO: 4 (huCRIg, or huCRIg-long, shown in FIGS. 2 and 5), with or without an N-terminal signal sequence, with or without the initiating methionine at position 1, and with or without any or all of the transmembrane domain at about amino acid positions 277 to 307 of SEQ ID NO: 4. In a still further embodiment, the native sequence CRIg polypeptide is the 305-amino acid, short form of human CRIg (huCRIg-short, SEQ ID NO: 6, shown in FIG. 3), with or without an N-terminal signal sequence, with or without the initiating methionine at position 1, and with or without any or all of the transmembrane domain at about positions 183 to 213 of SEQ ID NO: 6. In a different embodiment, the native sequence CRIg polypeptide is a 280 amino acids long, full-length murine CRIg polypeptide of SEQ ID NO: 8 (muCRIg, shown in FIGS. 4 and 5), with or without an N-terminal signal sequence, with or without the initiating methionine at position 1, and with or without any or all of the transmembrane domain at about amino acid positions 181 to 211 of SEQ ID NO: 8. CRIg polypeptides of other non-human animals, including higher primates and mammals, are specifically included within this definition.

#“CRIg variant” means an active CRIg polypeptide as defined below having at least about 80% amino acid sequence identity to a native sequence CRIg polypeptide, including, without limitation, the C-terminally truncated 321-amino acid huCRIg (SEQ ID NO: 2), the fill-length huCRIg (SEQ ID NO: 4), huCRIg-short (SEQ ID NO: 6), and muCRIg (SEQ ID NO: 8), each with or without the N-terminal initiating methionine, with or without the N-terminal signal sequence, with or without all or part of the transmembrane domain and with or without the intracellular domain. In a particular embodiment, the CRIg variant has at least about 80% amino acid sequence homology with the mature, full-length polypeptide from within the sequence of the sequence of SEQ ID NO: 2. In another embodiment, the CRIg variant has at least about 80% amino acid sequence homology with the mature, fill-length polypeptide from within the sequence of SEQ ID NO: 4. In yet another embodiment, the CRIg variant has at least about 80% amino acid sequence homology with the mature, fill-length polypeptide from within the sequence of SEQ ID NO: 6. In a still further embodiment, the CRIg variant has at least about 80% amino acid sequence homology with the mature, full-length polypeptide from within the sequence of SEQ ID NO: 8. Such CRIg polypeptide variants include, for instance, CRIg polypeptides wherein one or more amino acid residues are inserted, substituted and/or deleted, at the N— or C-terminus of the sequence of SEQ ID NO: 2, 4, 6, or 8. Other variants have one or more amino acids inserted, substituted and/or deleted within the transmembrane regions of the indicated polypeptide sequences.