Methods for diagnosing and treating encephalitis or epilepsy

1. A method for diagnosing an encephalitis in a subject, comprising the steps of: obtaining a biological sample from said subject; and testing said biological sample to determine the presence of an antibody to a GABA B receptor, whereby the presence of said antibody in said biological sample indicates an autoimmune encephalitis, wherein said antibody binds to the B1 subunit of said GABA B receptor, wherein the step of testing comprises an immunoassay to detect said antibody by an antigen, and wherein said antigen comprises the B1 subunit of said GABA B receptor, thereby determining a cause of an encephalitis in said subject.

2. The method of claim 1 , whereby said antibody binds to the B2 subunit of said GABA B receptor.

3. The method of claim 1 , whereby said autoimmune encephalitis is a paraneoplastic autoimmune encephalitis.

4. The method of claim 1 , whereby the autoimmune encephalitis is anti-GABA B receptor encephalitis.

5. The method of claim 1 , whereby said autoimmune encephalitis is a non-paraneoplastic, autoimmune encephalitis.

6. The method of claim 1 , whereby said autoimmune encephalitis comprises a limbic encephalitis.

7. The method of claim 1 , whereby said autoimmune encephalitis is associated with pathological symptoms.

8. The method of claim 7 , whereby the symptoms are seizures; psychiatric symptoms; abnormality in cognition and behavior; a movement disorder or abnormal movements; a decreased level of consciousness; hypoventilation; amnesia or a memory deficit; or a combination thereof.

9. The method of claim 1 , whereby said autoimmune encephalitis is associated with a tumor.

10. The method of claim 9 , whereby said tumor is a small cell lung cancer or a neuroendocrine tumor of the lung or other organs.

11. The method of claim 1 , whereby the biological sample is a cerebrospinal fluid (CSF).

12. The method of claim 1 , whereby the biological sample is a serum or plasma.

13. A method for determining an increased likelihood of the presence an occult tumor associated with an autoimmune encephalitis in a subject, comprising the steps of: obtaining a biological sample from said subject; and testing said biological sample to determine the presence of an antibody to a GABA B receptor, whereby the presence of said antibody in said biological sample indicates the increased likelihood of the presence of said occult tumor in said subject and that said tumor is a cause of said autoimmune encephalitis, wherein said antibody binds to the B1 subunit of said GABA B receptor, wherein the step of testing comprises an immunoassay to detect said antibody by an antigen, and wherein said antigen comprises the B1 subunit of said GABA B receptor.

14. The method of claim 13 , whereby said autoimmune encephalitis is a paraneoplastic autoimmune encephalitis.

15. The method of claim 13 , whereby said autoimmune encephalitis comprises a limbic encephalitis.

16. The method of claim 13 , whereby said autoimmune encephalitis is associated with seizures.

17. The method of claim 13 , whereby said autoimmune encephalitis is associated with pathological symptoms.

18. The method of claim 17 , whereby said pathological symptoms are psychiatric symptoms; an abnormality in cognition and behavior: a movement disorder; a decreased level of consciousness; hypoventilation; amnesia or a memory deficit; or a combination thereof.

19. The method of claim 13 , whereby the body fluid is cerebrospinal fluid (CSF).

20. The method of claim 13 , whereby the body fluid is a serum or plasma.

21. A method for diagnosing an epilepsy in a subject, comprising the steps of: obtaining a biological sample from said subject; and testing said biological sample to determine the presence of an antibody to a GABA B receptor, whereby the presence of said antibody in said biological sample indicates an increased likelihood of the presence of a tumor in said subject and said tumor is a cause of said epilepsy, wherein said antibody binds to the B1 subunit of said GABA B receptor, wherein the step of testing comprises an immunoassay to detect said antibody by an antigen, and wherein said antigen comprises the B1 subunit of said GABA B receptor, thereby diagnosing said epilepsy in said subject.

22. The method of claim 21 , whereby the body fluid is cerebrospinal (CSF) fluid.

23. The method of claim 21 , whereby the body fluid is a serum or plasma.

24. The method of claim 21 , whereby said GABA B receptor-associated encephalitis is anti-GABA B receptor encephalitis.

25. The method of claim 21 , whereby said autoimmune encephalitis is a non-paraneoplastic, autoimmune encephalitis.

26. A method for determining an increased likelihood of the presence a tumor in a subject having an epilepsy, comprising the step of: obtaining a biological sample from said subject; and testing said biological sample to determine the presence of an antibody to a GABA B receptor, whereby the presence of said antibody in said biological sample indicates the increased likelihood of the presence of a tumor in said subject, wherein said antibody binds to the B1 subunit of said GABA B receptor, wherein the step of testing comprises an immunoassay to detect said antibody by an antigen, and wherein said antigen comprises the B1 subunit of said GABA B receptor, thereby diagnosing said tumor in said subject having said epilepsy.

27. A method for treating an autoimmune encephalitis in a subject, comprising the steps of: determining an increased likelihood of the presence a tumor associated with said autoimmune encephalitis by testing a body fluid from said subject for an antibody to a GABA B receptor, whereby the presence of said antibody in said body fluid indicates the increased likelihood of the presence of said tumor in said subject and that said tumor is a cause of said autoimmune encephalitis, wherein said antibody binds to the B1 subunit of said GABA B receptor; and treating said tumor based on the determination of the increased likelihood of the presence of said tumor.

28. The method of claim 27 , whereby said encephalitis is associated with occult tumor.

29. The method of claim 27 , whereby said tumor is a small cell lung cancer or a neuroendocrine tumor of the lung or other organs.

30. The method of claim 27 , wherein the tumor is treated within four months of the onset of a symptom associated with autoimmune encephalitis.

31. The method of claim 27 , whereby the step of treating said tumor comprises removing said tumor in combination with immunotherapy or chemotherapy.

32. The method of claim 27 , whereby said antibody binds to the B2 subunit of said GABA B receptor.

33. The method of claim 27 , whereby said autoimmune encephalitis is a GABA B receptor-associated encephalitis.

34. The method of claim 27 , whereby said autoimmune encephalitis is a paraneoplastic autoimmune encephalitis.

35. The method of claim 27 , whereby said autoimmune encephalitis comprises a limbic encephalitis.

36. The method of claim 27 , whereby said autoimmune encephalitis is associated with pathological symptoms.

37. The method of claim 36 , whereby the symptoms are seizures; psychiatric symptoms; abnormality in cognition and behavior; a movement disorder or abnormal movements; a decreased level of consciousness; hypoventilation; amnesia or a memory deficit; or a combination thereof.

38. A method of treating autoimmune encephalitis in a subject, comprising the steps of: determining an increased likelihood of the presence a tumor associated with said autoimmune encephalitis by testing a body fluid from said subject for an antibody to a GABA B receptor, whereby the presence of said antibody in said body fluid indicates the increased likelihood of the presence of said tumor in said subject and that said tumor is a cause of said autoimmune encephalitis, wherein said antibody binds to the B1 subunit of said GABA B receptor; and treating said tumor within four months of the onset of a symptom associated with autoimmune encephalitis based on the determination of the increased likelihood of the presence of said tumor.

39. The method of claim 38 , whereby said encephalitis is associated with occult tumor.

40. The method of claim 38 , whereby said antibody binds to the B2 subunit of said GABA B receptor.

41. The method of claim 38 or 40 , wherein said subunit is a monomer of a multimer.

42. The method of claim 41 , wherein said multimer is a receptor homomer.

43. The method of claim 42 , wherein said homomer is a homo-dimer that comprises two B1 subunits.

44. The method of claim 41 , wherein said multimer is a receptor heteromer.

45. The method of claim 44 , wherein said heteromer comprises a B1 subunit and a B2 subunit.

46. The method of claim 44 , wherein said heteromer comprises a B1-a subunit and a B2 subunit.

47. The method of claim 44 , wherein said heteromorphy comprises a B1-b subunit and a B2 subunit.

48. The method of claim 44 , wherein said heteromer comprises a B1-c subunit and a B2 subunit.