The present invention provides antibodies, or fragments thereof, for isolating and/or identifying epitopes of an endogenous retrovirus, preferably of a melanoma associated endogenous retrovirus, and hybridoma cells producing said antibodies. The antibodies are useful especially for the treatment and diagnosis of cancer. Further, the present application covers diagnostic kits for the detection of cancer cells, especially of melanoma cells and methods for cancer diagnosis using said antibodies.
