Neuromyelitis optica autoantibodies as a marker for neoplasia

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This invention relates generally to neurological disorders, and more particularly, to an autoantibody marker for neuromyelitis optica (NMO) and its correlation with neoplasia.

Neuromyelitis optica (NMO) is a neurological disorder also known as Devic's syndrome in Western countries and as opticopinal multiple sclerosis in Asia. NMO has been regarded as a severe variant of multiple sclerosis (MS), and the antigen was recently identified as aquaporin-4.

This disclosure describes a correlation between the presence of neurological symptoms and neoplasia. In some, but not all, cases, the neurological symptoms have been associated with NMO, an autoimmune disease. The NMO antigen was recently described in U.S. Pat. No. 7,101,679 (incorporated herein by reference) as aquaporin-4. Based on the present disclosure, individuals that exhibit or have exhibited neurological symptoms can be screened for a neoplasia.

Neurological symptoms include, but are not limited to, vision impairment and/or tingling, numbness, weakness, limb spasms, loss of bladder and/or bowel control, or other neurological symptoms of unknown origin. Neoplasias include, but are not limited to, breast cancer, bladder cancer, lymphoma, thyroid cancer, thymic cancer, pancreatic cancer, cervical cancer, brain cancer (e.g., glioblastoma), lung cancer or adenocarcinoma, thymoma, prostate cancer, colorectal cancer, renal cancer, adrenal cancer, liver cancer, neurofibromatosis 1, and leukemia. A neoplasm can be a solid neoplasm (e.g. sarcoma or carcinoma) or a cancerous growth affecting the hematopoietic system (e.g., lymphoma or leukemia). Methods of detecting neoplasia or screening an individual for neoplasia are well known in the art and include, for example, blood or sera tests (e.g., immunoassays), MRI and/or CAT scans, and/or tissue biopsies.

If so desired, the presence or absence of an aquaporin-4 autoantibody (i.e., a NMO-specific autoantibody) can be determined prior to or after screening the individual for neoplasia. The methods of the invention are based on an association between the presence of abnormal neurological symptoms in an individual, oftentimes manifested in NMO (i.e., NMO-specific autoantibodies), and the presence of neoplasia. The present invention provides for methods of detecting neoplasia in an individual exhibiting neurological symptoms.

If so desired, the methods and compositions disclosed in U.S. Pat. No. 7,101,679 can be used to detect the aquaporin-4 autoantibody in an individual. Briefly, an aquaporin-4 polypeptide or an antigenic fragment thereof can be used to detect the presence or absence of the aquaporin-4 autoantibody in a biological sample using any of a number of immunological techniques. Aquaporin-4 polypeptides, antigenic fragments thereof, and methods of detecting an aquaporin-4 autoantibody are disclosed in U.S. Pat. No. 7,101,679. A representative antigenic fragment can include, for example, the extracellular domain of a membrane-bound protein.

Depending on the nature of the biological sample, immunological techniques include either or both immunoassays (e.g., enzyme-linked immunosorbent assays (ELISA), Western blot, and radioimmunoassay) and immunocytochemical staining techniques. Both types of immunological techniques are used routinely in the art and can be used to detect the presence of aquaporin-4-specific autoantibodies in a biological sample. A “biological sample,” as used herein, is generally a sample from an individual. Non-limiting examples of biological samples include blood, serum, plasma, or cerebrospinal fluid. Additionally, solid tissues, for example, spinal cord or brain biopsies may be used.

The term “aquaporin-4” refers to a member of the aquaporin family. The aquaporin family has 10 known members. Aquaporin-4 is expressed in the astrocytic foot process membrane contacting capillaries in the central nervous system, and also in the basolateral membrane of renal distal collecting tubules. Examples of a nucleotide sequence encoding a human aquaporin-4 polypeptide are shown in GenBank Accession Nos. U63622 and U63623. The predicted amino acid sequences of representative human aquaporin-4 polypeptides are shown in GenBank Accession Nos. AAG17964, AAB26957, AAB26958, and I39178. Nucleic acid and amino acid sequences encoding aquaporin-4 from other organisms (e.g., Mus musculus, Bos Taurus, Rattus norvegicus, and Ovis aries) can be found by searching the GenBank database (at ncbi.nlm.nih.gov on the World Wide Web) using “aquaporin-4” as the search word.

Aquaporin-4 antigenic polypeptides can be obtained using standard methods (for example, from cells (e.g., transfected host cells) expressing a nucleic acid or synthetically-generated) and can be purified, defined as a polypeptide that constitutes the major component in a mixture of components, e.g., 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more, by weight, using routine protein purification methods, including affinity chromatography or immunosorbant affinity column. Aquaporin-4 antigenic polypeptides and methods of making and identifying such antigenic polypeptides are described fully in U.S. Pat. No. 7,101,679.

As used herein, nucleic acid refers to RNA or DNA. With respect to nucleic acids, “isolated” refers to (i) a nucleic acid sequence encoding part or all of the human aquaporin-4 polypeptide, but free of coding sequences that normally flank one or both sides of the nucleic acid sequences encoding aquaporin-4 in the human genome; or (ii) a nucleic acid incorporated into a vector or into the genomic DNA of an organism such that the resulting molecule is not identical to any naturally-occurring vector or genomic DNA.

Fragments of the human aquaporin-4 nucleic acid and polypeptide also are provided. As used herein, fragments refer to nucleic acids or polypeptides corresponding to less than the entire aquaporin-4 sequence. Such fragments may, for example, encode an aquaporin-4 antigenic polypeptide fragment, or have utility as hybridization probes or amplification primers. FIG. 2 shows the relative position of various restriction enzyme sites within a human aquaporin-4 nucleic acid sequence that, by way of example, define positions, which, in various combinations, can be used to generate useful nucleic acid fragments. Given the nucleotide sequence of a human aquaporin-4 polypeptide, virtually any nucleic acid fragment can be generated by known means (e.g., restriction enzyme digestion, the polymerase chain reaction) and, if so desired, expressed to produce the corresponding polypeptide fragment. Alternatively, the human aquaporin-4 polypeptide can be cleaved (e.g., proteolytically) to directly generate polypeptide fragments.