[Viral safety of biological medicinal products]. / Virussicherheit von biologischen Arzneimitteln.

Viral safety of blood donations, plasma products, viral vaccines and gene therapy medicinal products, biotechnical-derived products and tissue and cell therapy products is a particular challenge. These products are manufactured using a variety of human or animal-derived starting materials and reagents; therefore, extensive testing of donors and of cell banks established for production is required. Furthermore, the viral safety of reagents, such as bovine sera, porcine trypsin and human transferrin or albumin needs to be considered. Whenever possible, manufacturing steps for inactivation or removal of viruses should be introduced; however, sometimes it is not possible to introduce such steps for tissues or cell-based medicinal products as the activity and viability of cells will be compromised. It might be possible to implement steps for inactivation or removal of potential contaminating enveloped viruses only for production of small and stable non-enveloped viral gene vectors.

[Important aspects of virus safety of advanced therapy medicinal products]. / Wichtige Aspekte der Virussicherheit bei Neuartigen Therapien.

Virus safety of advanced therapy medicinal products is a particular challenge. These products may consist of whole cells and the manufacture of these is performed using various human or animal-derived starting materials and reagents. Therefore, extensive testing of donors and of established cell banks is required. Furthermore, the virus safety of reagents such as bovine sera, porcine trypsin, and growth factors needs to be considered. Whenever possible, manufacturing steps for inactivation or removal of viruses should be introduced. However, it is not possible to introduce such steps for cell-based medicinal products as the activity and viability of cells will be compromised. Only in the production of small and stable non-enveloped viral gene vectors is it conceivable to implement steps to selectively inactivate or remove potential contaminating enveloped viruses.

The normal cell cycle activation program is exploited during the infection of quiescent B lymphocytes by Epstein-Barr virus.

B lymphocytes in the peripheral circulation are maintained in a non-proliferative state. Antigen recognition stimulates limited proliferation, whereas infection with Epstein-Barr virus (EBV) results in continual proliferation and the outgrowth of immortal cell lines. Because it is not clear at which point in cell cycle the peripheral B lymphocytes are arrested, we characterized the expression of several cell cycle-associated genes in quiescent and stimulated cells. We show that the expression of four cell genes, cdc-2, cyclin E, CD23, and cyclin D2, are up-regulated approximately 100-fold as a result of EBV-mediated immortalization. Because these genes play a positive role in cell proliferation, we suggest that this regulatory switch contributes to controlling entry into the cell cycle. Transient stimulation of quiescent B lymphocytes with either a cocktail of anti-CD40, anti-IgM, and IL4, or EBV results in the rapid expression of the same four genes, suggesting that, after infection, EBV exploits the normal program of B-lymphocyte cell cycle activation.

Thalidomide--the need for a new clinical evaluation of an old drug.

Thalidomide shows activity in refractory chronic graft-versus-host disease. Best responses were seen in mucocutaneous disease. The studies vary in inclusion criteria (e.g. pretreatment), time of onset of GVHD and dose given. The optimal schedule of thalidomide treatment is not defined. The role of thalidomide must be assessed in large controlled trials for treatment and prophylaxis of GvHD. Due to the variable absorption rate there is a need for an intravenous formulation of thalidomide, and in addition the search for more active and possibly less teratogenic derivatives must be intensified.

Epstein-Barr virus genes and cancer cells.

Human B lymphocytes infected with Epstein-Barr virus (EBV) express 11 viral genes, of which six are essential for efficient transformation. The protein products of these genes appear to cause cell growth by modifying cell signal transduction pathways. For example, EBNA-2 mimics the Notch 1 pathway and LMP-1 interacts with the signalling from CD40/CD40-L, which promotes growth in normal B cells. In the human cancers linked to EBV, most of the viral transforming genes are not expressed. It is likely that growth of these cells is controlled by a combination of the EBV genes whose expression continues with altered cell proto-oncogenes and tumour suppressor genes, but other explanations of the role of EBV in cancer cells are also possible. The presence of the virus in the tumour cells of EBV-associated cancers constitutes a potentially useful tumour specific marker that might be used to direct therapy to the tumour cells.

Coronavirus infection and demyelination. Sequence conservation of the S-gene during persistent infection of Lewis-rats.

Coronaviruses display a large phenotypic variability, which may be an important factor for diversification and selection. Previous studies have demonstrated that the S-protein is an essential determinant of virulence and pathogenicity. Therefore we studied the S-gene as an indicator molecule for selection processes employing two different MHV-JHM variants. First, Lewis-rats were infected with MHV-JHM-Pi, a variant that causes demyelinating disease after several weeks p.i. It was not possible to isolate infectious MHV-JHM-Pi from such rats, although viral proteins were expressed. The S-gene was rescued directly from brain tissue employing RT-PCR technology. The amplicons were sequenced in bulk or at the level of single clones. We detected no evidence for an increase of S-gene mutants during the length of time. Only few mutations were found at the clonal level. The changes were distributed throughout the analysed S-gene fragments without a predilection in their location. The frequency of mutation remained low within a range of 0.03 to 0.5 mutations per thousand nucleotides. As a second approach, we sequenced the S-genes of viruses isolated from brain tissue infected with MHV-JHM-ts43. Infection of adult Lewis rats with that mutant resulted several weeks to months p.i. in demyelinating encephalomyelitis. The S-gene of this virus contains an insertion of 423 bp in the S1 region, which is identical to a polymorphic region described for MHV-4. In contrast to JHM-Pi, infectious MHV-JHM-ts43 was readily to isolate from brain tissue. The S-gene sequences of virus isolated 45-106 days p.i. from diseased rats were identical with that of the input virus. These results show, that during a persistent infection of Lewis-rats the S-gene was highly conserved.

Recombinant vaccinia viruses which express MHV-JHM proteins: protective immune response and the influence of vaccination on coronavirus-induced encephalomyelitis.

Vaccinia-virus (VV) recombinants encoding either the nucleocapsid (N) or the spike (S) protein of MHV-JHM were constructed to study the role of the immune response against defined coronavirus antigens. For the S-protein, a fusogenic (Sfus+) or non fusogenic variant (Sfus-) of the gene was inserted into the VV genome. A strong protection against acute encephalomyelitis (AE) was mediated in Lewis rats which were immunized by VV-Sfus+ and challenged with an otherwise lethal dose of MHV-JHM before the induction of S-specific IgG antibodies. By contrast, a VV recombinant encoding a variant non fusogenic S-protein or the N-protein was not capable conferring protection. In addition, we demonstrated that MHV-JHM S-specific IgG antibodies elicited before MHV-JHM challenge modulated the disease process, changing it from an acute disease to subacute demyelinating encephalomyelitis (SDE).

Induction of protective immunity against coronavirus-induced encephalomyelitis: evidence for an important role of CD8+ T cells in vivo.

Coronavirus MHV-JHM infections of rats provide useful models to study the pathogenesis of virus-induced central nervous system disease. To analyze the role of the immune response against defined MHV-JHM antigens, we tested the protective efficacy of vaccinia virus (VV) recombinants expressing either the nucleocapsid (N) or the spike (S) protein. A strong protection was mediated in animals by immunization with recombinant VV encoding a wild-type S protein (VV-Swildtype), whereas VV recombinant expressing a mutant S354CR protein (VV-S354CR) had no protective effect. Recombinant VV encoding N protein (VV-N) induces a humoral and a CD4+ T cell response, but did not prevent acute disease regardless of the immunization protocol. In these experiments, challenge with an otherwise lethal dose of MHV-JHM was performed prior to the induction of virus-neutralizing antibodies and studies with the anti-CD8+ monoclonal antibody. MRC OX8 showed that elimination of the CD8+ subset of T cells abrogates the protective effect. This result indicates that CD8+ T cells primed by recombinant VV expressing wild-type S protein are a primary mechanism of immunological defense against MHV-JHM infection in rats.

Localization of antigenic sites on the surface glycoprotein of mouse hepatitis virus.

A panel of murine hepatitis virus (MHV) surface (S) glycoprotein-specific monoclonal antibodies (MAbs), which recognize either continuous or discontinuous epitopes, were tested in competitive binding assays. The results indicate that the binding site of MAb 30B amino acids 395 to 406 in the amino-terminal S1 subunit, is involved in the discontinuous epitope designated antigenic site A. This site is a major determinant for the induction of neutralizing antibodies. These data define, for the first time, the location of a functionally important domain on the MHV S protein.

Coronavirus-induced encephalomyelitis: balance between protection and immune pathology depends on the immunization schedule with spike protein S.

The neurotropic mouse hepatitis virus MHV-JHM induces central nervous system (CNS) demyelination in Lewis rats that pathologically resembles CNS lesions in multiple sclerosis. The mechanisms of MHV-JHM-induced demyelination remain unclear and several studies have implicated the role of the immune response in this process. We have shown previously that protective immunity against MHV-JHM-induced encephalomyelitis was induced by immunization with a vaccinia virus (VV) recombinant expressing MHV-JHM S-protein (VV-S). Here, we present evidence that the time of MHV-JHM challenge after immunization with VV-S plays a critical role in protective immunity. The induction of virus-neutralizing S-protein-specific antibodies prior to the MHV-JHM challenge modulates the disease process and a subacute encephalomyelitis based on a persistent virus infection developed. Typical pathological alterations were lesions of inflammatory demyelination. In addition, the results indicate that after seroconversion, CD8+ T cells were no longer essential for virus elimination in contrast to their role in protection during acute encephalomyelitis.

No evidence for quasispecies populations during persistence of the coronavirus mouse hepatitis virus JHM: sequence conservation within the surface glycoprotein gene S in Lewis rats.

The surface glycoprotein S (spike) of coronaviruses is believed to be an important determinant of virulence and displays extensive genetic polymorphism in cell culture isolates. This led us to consider whether the observed heterogeneity is reflected by a quasispecies distribution of mutated RNA molecules within the infected organ. Coronavirus infection of rodents is a useful model system for investigating the pathogenesis of virus-induced central nervous system (CNS) disease. Here, we investigated whether genetic changes in the S gene occurred during virus persistence in vivo. We analysed the variability of S gene sequences directly from the brain tissue of Lewis rats infected with the coronavirus mouse hepatitis virus (MHV) variant JHM-Pi using RT-PCR amplification methods. The S gene sequence displayed a remarkable genetic stability in vivo. No evidence for a quasispecies distribution was found by sequence analysis of amplified S gene fragments derived from the CNS of Lewis rats. Furthermore, the S gene also remained conserved under the selection pressure of a neutralizing antibody. Only a few mutations predicted to result in amino acid changes were detected in single clones. The changes were not represented in the consensus sequence. These results indicate that to retain functional proteins under the constraints of a persistent infection in vivo, conservation of sequence can be more important than heterogeneity.

Variant chromatin structure of the oriP region of Epstein-Barr virus and regulation of EBER1 expression by upstream sequences and oriP.

Most of the Epstein-Barr virus genome in latently infected cells is in a standard nucleosomal structure, but the region encompassing oriP and the Epstein-Barr virus-encoded small RNA (EBER) genes shows a distinctive pattern when digested with micrococcal nuclease. This pattern corresponds to a previously mapped nuclear matrix attachment region. Although the EBER genes are adjacent to oriP, there is only a two- to fourfold effect of oriP on EBER expression. However, sequences containing a consensus ATF site upstream of EBER1 are important for EBER1 expression.