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The MM5 trial aimed at demonstrating a progression-free survival (PFS) difference in continued vs. response-adapted (in case of complete response, CR) lenalidomide (LEN) maintenance therapy (MT) in newly diagnosed, transplant-eligible multiple myeloma (MM). Patients were equally randomized to receive induction therapy with PAd (bortezomib/doxorubicin/dexamethasone) or VCD (bortezomib/cyclophosphamide/dexamethasone), high-dose melphalan and autologous blood stem cell transplantation, and LEN consolidation, followed by either LEN MT for a fixed duration of 2 years (LEN-2Y) or until achievement of CR (LEN-CR, intention-to-treat population n = 502): arms A1:PAd + LEN-2Y (n = 125), B1:PAd + LEN-CR (n = 126), A2:VCD + LEN-2Y (n = 126), B2:VCD + LEN-CR (n = 125). In the LEN-CR group (B1 + B2), n = 88/17.5% patients did not start or discontinued LEN MT due to CR. There was no PFS (p = 0.60, primary endpoint) nor overall survival (OS) (p = 0.15) difference between the four study arms. On pooled LEN MT strategies, OS (hazard ratio, hazard ratio [HR] = 1.42, p = 0.03) but not PFS (HR = 1.15, p = 0.20) was shorter in LEN-CR (B1 + B2) vs. LEN-2Y (A1 + A2) groups. PFS was shortened on landmark analyses from the start of LEN MT in patients being in CR in the LEN-CR group (LEN-CR vs. LEN-2Y, HR = 1.84, p = 0.02). OS from first progression was shortened in the LEN-CR vs. LEN-2Y group (HR = 1.60, p = 0.01). LEN MT should be applied beyond CR for at least 2 years.

The previously characterized monoclonal antibodies (MAbs) A1, A69, B1, and A20 are directed against assembled or nonassembled adeno-associated virus type 2 (AAV-2) capsid proteins (A. Wistuba, A. Kern, S. Weger, D. Grimm, and J. A. Kleinschmidt, J. Virol. 71:1341–1352, 1997). Here we describe the linear epitopes of A1, A69, and B1 which reside in VP1, VP2, and VP3, respectively, using gene fragment phage display library, peptide scan, and peptide competition experiments. In addition, MAbs A20, C24-B, C37-B, and D3 directed against conformational epitopes on AAV-2 capsids were characterized. Epitope sequences on the capsid surface were identified by enzyme-linked immunoabsorbent assay using AAV-2 mutants and AAV serotypes, peptide scan, and peptide competition experiments. A20 neutralizes infection following receptor attachment by binding an epitope formed during AAV-2 capsid assembly. The newly isolated antibodies C24-B and C37-B inhibit AAV-2 binding to cells, probably by recognizing a loop region involved in binding of AAV-2 to the cellular receptor. In contrast, binding of D3 to a loop near the predicted threefold spike does not neutralize AAV-2 infection. The identified antigenic regions on the AAV-2 capsid surface are discussed with respect to their possible roles in different steps of the viral life cycle.

We present a comparative study on epitope mapping of four monoclonal antibodies directed against four different antigens using alternative phage display techniques and peptide scanning: mAb215 reacts with the largest subunit of RNA polymerase II, mAbBp53-11 with the tumor suppressor protein p53, mAbGDO5 with the Hantaan virus glycoprotein G2 and mAbL13F3 with the Hantaan virus nucleocapsid protein. Epitopes were determined (i) by gene-fragment phage display libraries, constructed by DNaseI digested random gene fragments cloned into the 5' terminus of the pIII-gene of fd phage and (ii) by random peptide phage libraries displaying 6mer and 15mer peptides at the N-terminus of the pIII protein. Using the gene-fragment phage display libraries a single round of affinity selection resulted in the determination of the corresponding epitopes for all monoclonal antibodies tested. In contrast, biopanning of 6mer and 15mer random peptide libraries was only successful for two of the antibodies (mAbBp53-11 and mAbGDO5) after three or four rounds of selection. For the anti-p53 antibody we recovered the epitope from both the 6mer and 15mer library, for mAbGDO5 only the 6mer library displayed the epitope sequence. However, screening of the random peptide libraries with mAb215 and mAbL13F3 failed to yield immunopositive clones. Fine mapping of the epitopes by peptide scan revealed that the minimal epitopes recognized by mAbBp53-11 and mAbGDO5 consist of four and five amino acids, respectively, whereas mAb215 requires a minimal epitope of 11 amino acids for antigen recognition. In contrast, mAbL13F3 did not react with any of the synthesized 15mer peptides. The limits of the different methods of epitope mapping tested in this study are compared and the advantages of the gene-fragment phage display system are discussed.

In recent years, immobilized peptides synthesized on activated cellulose membranes (SPOT synthesis, Frank 1992) have become an important tool in the study of protein-protein interactions and numerous other aspects of molecular recognition (reviewed in Reineke et al. 2001). A broad range of applications has already been described and the rising interest in proteomics is bound to rely on the enormous potential of the (automated) method. When adapted to high-throughput screening, SPOTs, i.e. peptide arrays, will become an invaluable tool in pharmacogenomics and drug discovery.

After microinjection of antibodies against RNA polymerase I into the nuclei of cultured rat kangaroo (PtK2) and rat (RVF-SMC) cells alterations in nucleolar structure and composition were observed. These were detected by electron microscopy and double-label immunofluorescence microscopy using antibodies to proteins representative of the three major components of the nucleolus. The microinjected antibodies produced a progressive loss of the material of the dense fibrillar component (DFC) from the nucleoli which, at 4 h after injection, were transformed into bodies with purely granular component (GC) structure with attached fibrillar centers (FCs). Concomitantly, numerous extranucleolar aggregates appeared in the nucleoplasm which morphologically resembled fragments of the DFC and contained a protein (fibrillarin) diagnostic for this nucleolar structure. These observations indicate that the topological distribution of the material constituting the DFC can be experimentally influenced in interphase cells, apparently by modulating the transcriptional activity of the rRNA genes. These effects are different from nucleolar lesions induced by inhibitory drugs such as actinomycin D-dependent "nucleolar segregation". The structural alterations induced by antibodies to RNA polymerase I resemble, however, the initial events of nucleolar disintegration during mitotic prophase.