Expression and purification of prostate-specific membrane antigen in the baculovirus expression system and recognition by prostate-specific membrane antigen-specific T cells.

Antigen-specific immunotherapy of cancer depends on a consistent source of well-defined protein antigen. Production of recombinant protein offers the obvious solution to this problem but few comparisons of recombinant and native proteins in cellular immune assays have been reported. We report expression of a putative immunotherapy antigen, prostate-specific membrane antigen (PSMA), in insect cells using a baculovirus vector. T cells stimulated with recombinant PSMA or native PSMA derived from the LNCaP cell line recognized both native PSMA and recombinant, baculoviral PSMA. These data indicate that PSMA produced in Sf9 cells is immunologically cross-reactive with native PSMA and therefore suitable for immunotherapy as it is recognized by both cellular and humoral immune responses.

Viral vectors for gene transfer into antigen presenting cells.

Crucial insights for vaccine development have come from examining how the immune system responds to antimicrobial vaccines, as well as to viral vectors employed for gene therapy. The effectiveness of a vaccine depends upon both the method of antigen delivery and the presentation of antigen to lymphocytes. Much focus has turned to delivering antigens to dendritic cells, to promote clinically beneficial T- and B-cell responses. Recombinant viral vectors represent a powerful vehicle to deliver genes encoding microbial- or tumor-derived antigens to generate clinically beneficial immunity. Dendritic cell-based and viral vector-based vaccines are currently being evaluated in clinical trials as a means of inducing antitumor immunity.

Interaction between the herpes simplex virus type 1 origin-binding and DNA polymerase accessory proteins.

Interactions between the herpes simplex virus type 1 (HSV-1) origin (ori)-binding protein (UL9) and two other components of the functional DNA replication complex have been observed. However, to date, no interaction between UL9 and a component of the DNA polymerase holoenzyme has been demonstrated. In this report, we demonstrate that UL9 and the DNA polymerase accessory protein (UL42) can form a stable complex in vitro as determined by coimmunoprecipitation with specific antibodies to each protein and by affinity chromatography using glutathione S-transferase (GST) fusion proteins. Complex formation does not require the presence of other viral proteins and occurs in the presence of ethidium bromide, indicating that UL9-UL42 interaction is DNA independent. Affinity beads charged with increasing concentrations of GST-42 fusion protein up to 5 microM bound increasing amounts of UL9 expressed by in vitro transcription/translation in rabbit reticulocyte lysates. Binding of N- and C-terminal portions of UL9 to GST affinity matrices revealed that the N-terminal 533 amino acids were sufficient for binding to GST-42, albeit at approximately a four- to six-fold reduced affinity compared to the full-length protein. No binding of a polypeptide containing the remainder of the UL9 C-terminal residues was observed. Thus the ori-binding protein, UL9, can physically associate with at least one member of each of the complexes (helicase/primase, DNA polymerase holoenzyme, single-stranded DNA-binding protein) required for origin-dependent DNA replication. These specific interactions provide a means by which the ordered assembly of HSV-1 DNA replication proteins at origins of replication can occur in the infected cell for initiation of viral DNA synthesis.

pH 2 instability of a mutant of mengovirus is related to its interferon sensitivity.

The is-1 mutant of mengovirus is 100 times more sensitive to interferon (IFN) than wild type, as measured by a yield reduction assay in the G3 line of mouse L cells, and is also much more readily inactivated at pH 2. Neither isolated nor encapsidated RNA is degraded under these conditions, which suggests that the pH-sensitive region resides on the virus coat. One-third of the viruses selected for resistance to low pH also showed enhanced resistance to IFN. Attempts to isolate IFN resistant strains directly from is-1 stocks were unsuccessful. These results suggest that either a capsid protein or its precursor is an active anti-IFN agent.