PAb1614, a monoclonal antibody reactive with the tumor antigens of SV40, JC, BK, and polyoma virus, and other JC virus tumor antigen cross-reactive antibodies of the PAb1601-1636 panel

Progressive multifocal leukoencephalopathy in a patient without apparent immunosuppression

Progressive multifocal leukoencephalopathy (PML) is a viral demyelinating disease due to the reactivation of the JC virus (JCV), which usually occurs in the context of immunosuppression in HIV infection, malignancy, or in patients on disease modifying therapy for autoimmune diseases, such as multiple sclerosis (MS) and Crohn's disease. Notably, there is growing recognition that PML can occur in patients with transient immune dysfunction. Here, we present a case of a 55-year-old man without history of immunosuppression or evidence of ICL who was diagnosed with PML on brain biopsy. We will discuss the potential etiologies of mild and transient immunosuppression that can lead to PML with non-apparent immunosuppression.

Hamster polyomavirus-encoded proteins: gene cloning, heterologous expression and immunoreactivity

The hamster polyomavirus (HaPV) is associated with spontaneously appearing skin epithelioma of the Syrian hamster Z3 strain. Virus particles prepared from the skin epithelioma cause lymphoma and leukemia when injected into newborn hamsters from a distinct Syrian hamster colony (HaP); in contrast to the skin epithelioma the hemopoietic tumors are virus free but accumulate viral DNA. To study the humoral immune response of HaPV-infected Z3 hamsters we produced recombinant HaPV proteins in Escherichia coli as beta-galactosidase-, TrpE- and dihydrofolate reductase-fusion proteins or as non-fused proteins. Recombinant plasmids carried segments of all putative early and late HaPV proteins. The recombinant proteins were detected in stained SDS polyacrylamide gels and in Western blots using monoclonal anti-TrpE and anti-beta-galactosidase antibodies and sera of HaPV-infected hamsters. Sera from HaPV-infected Z3 hamsters and crude lysates of all clones were applied to Western blots to characterize the humoral immune response in the animals. HaPV-specific antibodies were found to be directed against early protein segments translated from the first common exon and from the second unique exon of LT and MT, resp., as well as against the late proteins VP1 and VP2/3. The almost complete VP2 was recognized by all sera whereas VP1 was detected only by a half of the sera. Our data suggest the presence of at least 2 immunodominant regions in VP2, one in the C-terminal VP1 and at least 4 in early proteins.

Monospecific polyclonal anti-anti-idiotypic antibodies to the carboxyterminal undecapeptide of the SV40 large tumour antigen

The murine monoclonal antibody PAb1605 defines an epitope, peptide Lys(698)-Thr(708) (KT), on the carboxyterminus of the tumour(T)antigen of SV40-transformed cells. In vivo and in vitro experiments had shown that this sequence represents an epitope for both humoral and cellular immune responses. When injected into rabbits PAb1605 induces anti-idiotypic antibodies (Ab-2). Ab-2 beta (internal image type) was purified by adsorption chromatography and characterized by the ability of KT to compete with the binding of ab-2 with ab-1. Murine anti-anti-idiotypic antibodies (ab-3) were obtained by immunization of mice with ab-2 beta. Both ab-1 and ab-3 JgG showed affinities to immunoprecipitated SV40 T antigen by immunoblot analysis and to nuclear SV40 T antigen by the immunofluorescence assay. The binding of ab-3 to SV40 T antigen was completely inhibited by competition with KT. We conclude that the polyclonal ab-3 is of the ab-3 subtype and specific for only one epitope which is represented by KT and defined by ab-1. The results demonstrate that the specificity for a defined peptide epitope of an antibody was conserved even after two consecutive steps of anti-idiotypic-antibody formation in two host species. Since this postulate of network theory could be verified for a sequence of a tumour-associated antigen which represents a B- and T cell epitope, this model is of great interest for further tumour immunological studies.