Vaccinia-based oncolytic immunotherapy Pexastimogene Devacirepvec in patients with advanced hepatocellular carcinoma after sorafenib failure: a randomized multicenter Phase IIb trial (TRAVERSE)

Pexastimogene devacirepvec (Pexa-Vec) is a vaccinia virus-based oncolytic immunotherapy designed to preferentially replicate in and destroy tumor cells while stimulating anti-tumor immunity by expressing GM-CSF. An earlier randomized Phase IIa trial in predominantly sorafenib-naïve hepatocellular carcinoma (HCC) demonstrated an overall survival (OS) benefit. This randomized, open-label Phase IIb trial investigated whether Pexa-Vec plus Best Supportive Care (BSC) improved OS over BSC alone in HCC patients who failed sorafenib therapy (TRAVERSE).

129 patients were randomly assigned 2:1 to Pexa-Vec plus BSC vs. BSC alone. Pexa-Vec was given as a single intravenous (IV) infusion followed by up to 5 IT injections. The primary endpoint was OS. Secondary endpoints included overall response rate (RR), time to progression (TTP) and safety.

A high drop-out rate in the control arm (63%) confounded assessment of response-based endpoints. Median OS (ITT) for Pexa-Vec plus BSC vs. BSC alone was 4.2 and 4.4 months, respectively (HR, 1.19, 95% CI: 0.78–1.80; p = .428). There was no difference between the two treatment arms in RR or TTP. Pexa-Vec was generally well-tolerated. The most frequent Grade 3 included pyrexia (8%) and hypotension (8%). Induction of immune responses to vaccinia antigens and HCC associated antigens were observed.

Despite a tolerable safety profile and induction of T cell responses, Pexa-Vec did not improve OS as second-line therapy after sorafenib failure. The true potential of oncolytic viruses may lie in the treatment of patients with earlier disease stages which should be addressed in future studies.

ClinicalTrials.gov: NCT01387555

Clinical Course of acute-on-chronic liver failure syndrome and effects on prognosis

Acute-on-chronic liver failure (ACLF) is characterized by acute decompensation (AD) of cirrhosis, organ failure(s), and high 28-day mortality. We investigated whether assessments of patients at specific time points predicted their need for liver transplantation (LT) or the potential futility of their care. We assessed clinical courses of 388 patients who had ACLF at enrollment, from February through September 2011, or during early (28-day) follow-up of the prospective multicenter European Chronic Liver Failure (CLIF) ACLF in Cirrhosis study. We assessed ACLF grades at different time points to define disease resolution, improvement, worsening, or steady or fluctuating course. ACLF resolved or improved in 49.2%, had a steady or fluctuating course in 30.4%, and worsened in 20.4%. The 28-day transplant-free mortality was low-to-moderate (6%-18%) in patients with nonsevere early course (final no ACLF or ACLF-1) and high-to-very high (42%-92%) in those with severe early course (final ACLF-2 or -3) independently of initial grades. Independent predictors of course severity were CLIF Consortium ACLF score (CLIF-C ACLFs) and presence of liver failure (total bilirubin ≥12 mg/dL) at ACLF diagnosis. Eighty-one percent had their final ACLF grade at 1 week, resulting in accurate prediction of short- (28-day) and mid-term (90-day) mortality by ACLF grade at 3-7 days. Among patients that underwent early LT, 75% survived for at least 1 year. Among patients with ≥4 organ failures, or CLIF-C ACLFs >64 at days 3-7 days, and did not undergo LT, mortality was 100% by 28 days.

CONCLUSIONS

Assessment of ACLF patients at 3-7 days of the syndrome provides a tool to define the emergency of LT and a rational basis for intensive care discontinuation owing to futility.

[Diagnosis of and therapy for hepatocellular carcinoma]

The interdisciplinary guidelines at the S3 level on the diagnosis of and therapy for hepatocellular carcinoma (HCC) constitute an evidence- and consensus-based instrument that is aimed at improving the diagnosis of and therapy for HCC since these are very challenging tasks. The purpose of the guidelines is to offer the patient (with suspected or confirmed HCC) adequate, scientifically based and up-to-date procedures in diagnosis, therapy and rehabilitation. This holds not only for locally limited or focally advanced disease but also for the existence of recurrences or distant metastases. Besides making a contribution to an appropriate health-care service, the guidelines should also provide the foundation for an individually adapted, high-quality therapy. The explanatory background texts should also enable non-specialist but responsible colleagues to give sound advice to their patients concerning specialist procedures, side effects and results. In the medium and long-term this should reduce the morbidity and mortality of patients with HCC and improve their quality of life.

Hepatic stem and progenitor cells in liver diseases and hepatocarcinogenesis

Because of its physiological role and its central function in metabolism and homeostasis, the liver is exposed to an environment rich in toxins. In addition, the liver has to cope with various infectious pathogens, in particular hepatotropic viruses. Therefore, the liver needs efficient and highly regulated regeneration mechanisms. Under normal circumstances the liver shows a low rate of hepatocyte renewal but in the event of liver injury, for example, acute liver damage or drug intoxications, hepatocytes display a remarkable capacity to divide and to restore the liver parenchyma. Because of their enormous capability to regenerate the liver, which is unique among differentiated cells in human organs, hepatocytes function as stem cells. However, if the proliferation of hepatocytes is impaired, as in liver cirrhosis, a progenitor cell population is activated and serves as reserve compartment for liver restoration. Hepatic progenitor cells are bipotential and are located in the canals of Hering, the most peripheral branches of the biliary system. According to the current paradigm, hepatic progenitor cells drive liver regeneration in end-stage liver diseases, where hepatocytes become senescent and may therefore be a target cell population for carcinogenesis. In this review, we revisit landmark studies, summarize the current nomenclature, and discuss recent data elucidating the characteristics and the functional role of hepatic stem and progenitor cells in liver diseases and hepatocarcinogenesis.

Cationic lipid polymerization as a novel approach for constructing new DNA delivery agents

In vivo gene delivery mediated by cationic lipids is often compromised by aggregation due to complexation with proteins in the blood. To improve the stability of cationic lipid-DNA complexes, the present study aimed to develop a novel approach in which a poly(cationic lipid) (PCL) is utilized to form stable cationic polyplexes for gene transfection. Hydrogenation of the acrylamide analogue of betaAE-DMRI, the polymerizable precursor of PCL, provided a monomeric lipid derivative (MHL) which was used for direct comparison of corresponding lipoplex stability, toxicity, and transfection activity. Various formulations of cationic liposomes, such as MHL, MHL-cholesterol (Chol), PCL, PCL-Chol, DOTAP-Chol, and commercially available lipofectamine were generated and examined in this study. The new poly(cationic lipid) did not display any significant toxicity to rat hepatocytes or Hep G2 cells as indicated by an LDH leakage assay. Furthermore, PCL was significantly less toxic than MHL, DOTAP-Chol or lipofectamine. Suspensions of PCL were resistant to aggregation even after 24 h of exposure to solutions containing 50 and 100% fetal bovine serum (FBS). In contrast, suspensions of lipofectamine extensively aggregated after 24 h of exposure to 50% FBS. To examine the influence of lipid polymerization on gene transfer activity, liposome-mediated transfections of a luciferase vector (pGL3) were performed in Hep G2 and Alexander cell lines. The luciferase activity of the PCL formulations in Hep G2 cells were similar to those of the MHL, DOTAP-Chol and lipofectamine formulations, demonstrating that lipid polymerization does not compromise transfection activity. In comparison to the monomeric precursor MHL and to the industry transfection standards DOTAP and lipofectamine, the novel poly(cationic lipid) exhibited the lowest cytotoxicity, was the most resistant to serum-induced aggregation and had comparable transfection activity when coformulated with cholesterol. This novel polymerization approach for the development of stable and active polyplexes may prove a valuable alternative for in vivo gene delivery.

Porcine reproductive and respiratory syndrome virus (PRRSV): kinetics of infection in lymphatic organs and lung

Pigs were infected by the oronasal route with European isolates of the porcine reproductive and respiratory syndrome virus (PRRSV; I10 and Cobbelsdorf). The kinetics of infection in lymphatic organs and the lung were analysed by immunofluorescence detection of virus antigen, re-isolation of the virus and reverse transcription--polymerase chain reaction (RT-PCR) for PRRSV-specific RNA. The kinetics of PRRSV infection proceeded in three phases, irrespective of the varying infestation of lymphatic organs within the first days post-infection (p.i.). First, an early acute infection of lymphatic organs developed within the first week and was characterized by a high number of antigen-positive macrophages. Second, a delayed acute infection of the lung was observed, which was most pronounced during the second and third week p.i. when a high number of infected alveolar macrophages was observed. The acute infection of lymphatic organs had resolved at this time. Infected cells in the lung were predominantly located in pneumonic lesions. Third, a persistent infection was demonstrated by RT-PCR and immunohistology when the experiments were terminated at day 49 p.i. The virus persisted in lymphatic organs, especially in the tonsils, and in the lung. At this stage, indications for a re-occurrence of acute infection were observed in restricted areas of the lung.

Coronavirus infection and demyelination. Development of inflammatory lesions in Lewis rats

Coronavirus infections of rodents can cause diseases of the central nervous system characterised by inflammatory demyelination. The lesions mimick in many aspects the pathology of multiple sclerosis in humans and of other neurological diseases. As an animal model for demyelination, we studied the MHV-JHM induced encephalomyelitis of Lewis rats. The pathomorphological analysis revealed patterns of lesions which developed in stages. Infected oligodendrocytes were first destroyed by necrosis. Later stages were characterized by demyelinated plaques. In the center of plaques, no virus antigen was found and oligodendrocytes were mainly destroyed by apoptosis. At the edge of plaques, virus antigen was expressed in parallel to infiltrations consisting of lymphocytes and macrophages. The prevailing mechanisms leading to demyelination may change individually and during defined stages of the disease. The transcriptional expression of chemoattractants and other mediators of inflammation was studied by semiquantitative RT-PCR. Virus induced inflammatory demyelination was accompanied by high expression of a relatively novel cytokine, the endothelial monocyte activating polypeptide II (EMAP II). By immunocytochemistry, EMAP II was detected in parenchymal microglia located both within the lesions and in unaffected areas. Furthermore, the level of transcriptional expression of the regulatory calcium binding S100 proteins MRP8, MRP14 and CP10 was associated with inflammatory demyelination and expression of IFN gamma, IL-2, TNF alpha, and iNOS.

Arterivirus PRRSV. Experimental studies on the pathogenesis of respiratory disease

Pigs were infected with the porcine respiratory and reproductive syndrome virus (PRRSV) by the oronasal route. We studied the development of histological lesions, sites of virus infection and of inflammatory infiltrates by quantitative evaluation of reactive cells. The animals developed a multifocal interstitial pneumonia. Clinical signs of pneumonia were observed from day 7 to 21. In the first stage, an acute alveolitis was found, which was characterised by a hyperplasia of type II pneumocytes within the septa and an accumulation of macrophages in the alveolar spaces. Within 2-4 days p.i., virus infected cells were prominent in lymphatic organs, but their number declined rapidly during the following days. In the following period, the number of virus antigen positive cells increased in the lung. An interesting discrepancy existed between the relatively small number of virus specific cells and the degree of intensive pneumonia. As a first step to analyse mechanisms leading to the induction of pneumonia, we studied transcriptional expression of cytokines and other immunomodulatory molecules by semiquantitative RT-PCR.

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.

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.

Patterns of oligodendrocyte pathology in coronavirus-induced subacute demyelinating encephalomyelitis in the Lewis rat

Intracerebral infection of rats with JHM coronavirus induces a chronic inflammatory demyelinating disease, which in many respects mimicks the pathology of multiple sclerosis. We investigated the patterns of demyelination and oligodendrocyte pathology in this model. In early stages of the disease infection of oligodendrocytes was associated with a downregulation of expression of mRNA for proteolipid protein in the absence of myelin destruction. When demyelinating lesions were formed infected oligodendrocytes were destroyed by necrosis, whereas oligodendrocytes that did not contain detectable virus antigen or RNA were in part dying by apoptosis. At this stage of the disease remyelination of the lesions was pronounced. At later stages after infection virus antigen was nearly completely cleared from the lesions. In spite of the lack of detectable virus, ongoing demyelination and unspecific tissue destruction occurred, and oligodendrocytes were mainly destroyed by apoptosis. These late lesions revealed only minimal central remyelination, but they were frequently repaired by Schwann cells. Our studies suggest that the mechanisms of myelin destruction in this model of virus-induced demyelination are complex and that the patterns of tissue damage may change during the course of the disease.

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.

Location of antibody epitopes within the mouse hepatitis virus nucleocapsid protein

Thirteen monoclonal antibodies (Mab) specific for the nucleocapsid (N) protein of mouse hepatitis virus were mapped using a panel of carboxy-terminal N protein truncations expressed by recombinant vaccinia viruses. All of the Mab recognized both native protein and full-length N protein expressed in this vector by both Western blot and enzyme-linked immunoabsorbent assays (ELISA), indicating that they recognized linear epitopes. The results obtained by both Western blot and ELISA for binding to the truncated N proteins coincide for seven of the Mab tested. The linear epitopes recognized localize to four domains dispersed between amino acids 171 and 196, 231 and 277, and 374 and 455. The epitopes for six Mab were localized to domains comprising 29 amino acids or less as determined by ELISA. Seven Mab showed different reactivity patterns in Western blot versus ELISA, suggesting binding may be influenced by local conformation. Therefore, the fine specificity of these Mab could not be determined with certainty. These data represent the first determination of antibody binding domains within the mouse hepatitis virus N protein which forms the viral helical nucleocapsids and appears to perform a number of regulatory functions during virus replication.

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).

Coronavirus induced encephalomyelitis: an immunodominant CD4(+)-T cell site on the nucleocapsid protein contributes to protection

In this communication we present clear evidence, that the N-protein of MHV-JHM contains immunodominant CD4+ T-cell sites. These sites were recognized by the immune system of virus infected Lewis rats. In previous investigations we have shown, that CD4+ T-cell lines with specificity for defined viral proteins can be selected from diseased Lewis rats and mediate protection, if transferred to otherwise lethally infected animals. To define regions of the N-protein, which are immunodominant for the T-cell response, we employed bacterially expressed N-protein and truncated subfragments of N as an antigen. We demonstrate, that T-cells from MHV-JHM infected, diseased Lewis rats recognized with high prevalence the carboxyterminal subfragment C4-N (95 aa) and to some extent the adjacent C3-N protein. The same results were obtained with T-cells derived from rats immunized with bacterially expressed N-protein or from animals vaccinated by a stable N-protein expressing vaccinia recombinant. Finally, transfer of CD4+ line T-cells to MHV-JHM infected rats specific for C4-N mediated protection against acute disease.

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.

An immunodominant CD4+ T cell site on the nucleocapsid protein of murine coronavirus contributes to protection against encephalomyelitis

The murine coronavirus neurotropic strain JHM (MHV-JHM) nucleocapsid (N) protein induces a strong T-helper cell response in Lewis rats. It has been shown previously that N-specific CD4+ T cells can confer protection against acute disease upon transfer to otherwise lethally infected rats. To define the major antigenic regions that elicit this T cell response, truncated fragments of N protein were expressed from a bacterial expression vector and employed as T cell antigens. Lymphocytes from either MHV-JHM-infected or immunized rats were stimulated in culture with virus antigen, grown and tested for their specificity to the N protein fragments. The carboxy-terminally located C4-N fragment (95 amino acids) induced the most pronounced proliferative response irrespective of whether the lymphocyte culture was derived from immunized or MHV-JHM-infected rats. We established T cell lines specific for the truncated N protein fragments and tested their potential to mediate protection by transfer experiments. Only the T cell line C4-N and the T cell line specific for the full-length N protein were protective. By contrast, all truncated N protein fragments elicited a humoral immune response and contained antigenic sites recognized by antibodies from diseased rats.

Identification of an immunodominant linear neutralization domain on the S2 portion of the murine coronavirus spike glycoprotein and evidence that it forms part of complex tridimensional structure

Numerous studies have demonstrated that the spike glycoprotein of coronaviruses bears major determinants of pathogenesis. To elucidate the antigenic structure of the protein, a panel of monoclonal antibodies was studied by competitive ELISA, and their reactivities were assayed against fragments of the murine coronavirus murine hepatitis virus strain A59 S gene expressed in prokaryotic vectors. An immunodominant linear domain was localized within the predicted stalk, S2, of the peplomer. It is recognized by several neutralizing antibodies. Other domains were also identified near the proteolytic cleavage site, in the predicted globular head, S1, and in another part of the stalk. Furthermore, competition results suggest that the immunodominant functional domain forms part of a complex three-dimensional structure. Surprisingly, some antibodies which have no antiviral biological activities were shown to bind the immunodominant neutralization domain.

Coronavirus induced primary demyelination: indications for the involvement of a humoral immune response

Coronavirus MHV-JHM infection of rodents can result in demyelinating encephalomyelitis. We analysed histological changes induced by coronavirus MHV-JHM infection in Lewis rats. Besides an acute disease (AE), chronic panencephalitis (CPE) and subacute demyelinating encephalomyelitis (SDE) were induced. These disease types were differentiated by the incubation period, the localization of lesions, the type of tissue damage and distribution of virus antigen. In AE and CPE, virus antigen was detected in neurons, astrocytes and oligodendrocytes, whereas in SDE neurons lacked virus antigen. Viral nucleocapsid protein (N) was present in the cytoplasm and the spike protein (S) was displayed on the surface of infected neural cells. However, expression of S protein relative to N protein was severely impaired in SDE lesions. Quantitative analysis of infiltrating inflammatory cells revealed that the number of macrophages and T cells were similar in lesions of AE, CPE and SDE. In contrast to that, SDE lesions contained a significantly higher number of IgG + B cells and plasma cells. In addition active demyelinating SDE lesions displayed an enhanced IgG content and deposits of complement C9. These results indicate that virus induced primary demyelination could be a consequence of antibody mediated cytotoxicity. Furthermore, a reduction in the number of cells producing spike protein in the chronic forms of the disease indicates down-regulation of this protein, possibly mediated by anti-S antibodies.

Nucleocapsid or spike protein-specific CD4+ T lymphocytes protect against coronavirus-induced encephalomyelitis in the absence of CD8+ T cells

To investigate the antiviral CD4+ T cell response in coronavirus MHV-JHM-induced encephalomyelitis, spleen and thymic lymphocytes from diseased rats were stimulated in culture with virus Ag, expanded and tested for their specificity to viral proteins and nucleocapsid (N) and spike (S) proteins that had been expressed in bacteria. A strong T cell response specific for N was measurable during acute disease, whereas S-specific T cells were only detectable in rats with a later onset of disease. CD4+ T cell lines with specificity for virus and either N or S protein were established and their influence on the course of a mouse hepatitis virus-JHM infection was investigated. All lines were of the CD4+ phenotype. Both N and S protein-specific CD4+ T cells conferred protection to infected Lewis rats and reduced the amount of infectious virus in the central nervous system. After transfer of CD4+ T cells and challenge with virus, an increase in the antiviral IgM response occurred, but neutralizing antibodies were not detectable during the period of virus clearance. Previous CD8+ cell depletion did not abrogate protection mediated by CD4+ T cell line transfer.

The T-cell-receptor repertoire in the synovial fluid of a patient with rheumatoid arthritis is polyclonal

We have analyzed the T-cell-receptor repertoire expressed in the synovial fluid of a patient with rheumatoid arthritis by using an inverse polymerase chain reaction. Total RNA was isolated from Ficoll-purified mononuclear cells and converted into circularized double-stranded cDNA. Specific amplification of alpha- and beta-chain variable regions (V alpha and V beta) was achieved with inverted alpha- and beta-chain constant region (C alpha and C beta) primer pairs, and the amplification products were cloned into phage vectors. A total of 78 alpha and 76 beta clones were sequenced, and 67 and 72 productively rearranged alpha and beta genes were identified, respectively. Thirty-one V alpha, 33 alpha-chain joining region (J alpha), 29 V beta, and 12 beta-chain joining region (J beta) gene segments were found in the productively rearranged clones, indicating that the T-cell repertoire expressed in the synovial fluid of this RA patient is highly heterogenous and polyclonal. Comparison of peripheral blood and synovial fluid repertoires showed that the most abundant V beta sequences, V beta 2.1 and V beta 3.1, were enriched in the inflamed joint by a factor of 2 to 3. It is possible that T cells expressing these V beta gene segments, which recognize bacterial superantigens, play a role in the disease.

Nucleocapsid or spike protein-specific CD4+ T lymphocytes protect against coronavirus-induced encephalomyelitis in the absence of CD8+ T cells

To investigate the antiviral CD4+ T cell response in coronavirus MHV-JHM-induced encephalomyelitis, spleen and thymic lymphocytes from diseased rats were stimulated in culture with virus Ag, expanded and tested for their specificity to viral proteins and nucleocapsid (N) and spike (S) proteins that had been expressed in bacteria. A strong T cell response specific for N was measurable during acute disease, whereas S-specific T cells were only detectable in rats with a later onset of disease. CD4+ T cell lines with specificity for virus and either N or S protein were established and their influence on the course of a mouse hepatitis virus-JHM infection was investigated. All lines were of the CD4+ phenotype. Both N and S protein-specific CD4+ T cells conferred protection to infected Lewis rats and reduced the amount of infectious virus in the central nervous system. After transfer of CD4+ T cells and challenge with virus, an increase in the antiviral IgM response occurred, but neutralizing antibodies were not detectable during the period of virus clearance. Previous CD8+ cell depletion did not abrogate protection mediated by CD4+ T cell line transfer.

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.

Astrocytes as antigen presenting cells for primary and secondary T cell responses: effect of astrocyte infection by murine hepatitis virus

CD4+ T cell lines specific for murine hepatitis virus (MHV) - JHM or myelin basic protein (MBP) proliferated when cultured together with MHC class I and II positive syngeneic rat astrocytes and either inactivated virus or MBP as antigen. The magnitude of the T cell proliferative response was comparable to that seen when thymocytes were used as a source of antigen presenting cells (APC). In contrast, MHC class I and II positive astrocytes were unable to significantly stimulate the proliferation of highly purified populations of naive CD4+ and CD8+ T cells in an allogeneic mixed lymphocyte reaction (MLR). Both T cell populations proliferated when mixed with allogeneic lymph node cells. Infection of the astrocytes with a variant of MHV-JHM (PI-AS22D) did not alter this cells incapacity to stimulate the naive CD4+ and CD8+ T cells to proliferate.

Growth pattern of various JHM coronavirus isolates in primary rat glial cell cultures correlates with differing neurotropism in vivo

The JHM strain of murine hepatitis coronavirus is neurotropic in rats, causing either fatal acute encephalomyelitis or subacute demyelinating encephalomyelitis. We have examined the growth properties of three JHM virus isolates in primary rat glial cultures and found a correlation with their ability to cause disease. Wild type JHM virus has the propensity to cause lytic infections in glial cultures, and a temperature-sensitive mutant designated JHM-ts43 invariably produces persistent infections with reduced cytopathic effects (CPE) as compared to the wild type. Moreover, a non-neurotropic isolate, designated JHM-Pi virus, produces either non-productive persistent infections at low multiplicity of infection (m.o.i.) or productive persistent infections at high m.o.i., with, however, no CPE. The phenotypic expression of persistence is glial cell-dependent, since all three viruses produce similarly lytic infections when grown on various susceptible cell lines. The genetic basis of JHM virus persistence can be explained at the level of direct virus-glial cell interactions.

Detection of human immunodeficiency virus and other retroviruses in cell culture supernatants by a reverse transcriptase microassay

A micromethod for the detection of human immunodeficiency virus (HIV) and other retroviruses in cell culture supernatants is described which applies a DEAE ion exchanger for recovery of polynucleotides synthesized in vitro by the retroviral reverse transcriptase. Cell culture, sample preparation, and test performance including the washing step are adapted to microtitre plates. Compared to the standard method this technique produced less non-specific reactions, resulting in a more than 3-fold higher sensitivity, a higher reproducibility due to lower intrarun variations and allowed an increase in the daily sample accomplishment per person 3- to 4-fold at lower costs per sample.

The peplomer protein E2 of coronavirus JHM as a determinant of neurovirulence: definition of critical epitopes by variant analysis

We selected murine coronavirus JHM variants specifically changed in defined antigenic sites of the peplomer protein E2. Variants were isolated from the supernatants of monoclonal antibody hybridoma cell cultures which continued to secrete neutralizing antibodies after being infected with JHM. Comparative antigenic analysis and biological tests were performed in order to refine an operational epitope map and to characterize functional domains important for pathogenicity. The reaction patterns (neutralization, inhibition of cell fusion, immunofluorescence and binding in ELISA) between the variant viruses and the panel of monoclonal antibodies were very similar. Four groups of variants were characterized each of which revealed distinct changes affecting one defined antigenic site. These observations indicated that at least four independently mutable antigenic sites were associated with domains involved in cell fusion, neutralization and pathogenicity (E2-Aa, -Ab, -Ba and -Bb). JHM variants with alterations in the E2-Aa, -Ab or -Bb sites were similar to wild-type virus. These variants caused acute hepatitis and encephalomyelitis in mice. In contrast, JHM variants with changes in site E2-Ba had a strong propensity to induce chronic disease accompanied by demyelination persisting for several months.

Comparative analysis of coronavirus JHM-induced demyelinating encephalomyelitis in Lewis and Brown Norway rats

Lewis and Brown Norway rats were infected at different ages with the neurotropic murine coronavirus strain, JHM and the resultant central nervous system diseases were studied. Suckling rats of both strains came down with a fatal, acute encephalomyelitis. Weanling Lewis rats developed a subacute demyelinating encephalomyelitis which neuropathologically revealed changes of an immunopathologic reaction. In contrast, Brown Norway rats developed a clinically silent subacute demyelinating encephalomyelitis with a persistent JHM virus infection which was less severe and quite different from the subacute demyelinating encephalomyelitis in Lewis rats with respect to size, distribution, and localization of the demyelinating plaques as well as the type of infiltrating cells. In addition, infected Lewis rats showed a pronounced lymphocyte proliferation to myelin basic protein and JHM virus whereas lymphocytes from infected Brown Norway rats did not react to these two antigens. These observations demonstrate the pathogenetic importance of host factors in the development of virus-induced demyelination.

Analysis of the intrathecal humoral immune response in Brown Norway (BN) rats, infected with the murine coronavirus JHM

Serum and CSF specimens from clinically healthy Brown Norway (BN) rats inoculated intracerebrally with corona virus JHM were analysed with respect to the state of the blood-brain barrier (BBB) and the intrathecal synthesis and isoelectric distribution of immunoglobulins (Ig). Increased CSF/serum ratios for Ig in the context of an intact BBB were never seen in the absence of intrathecal synthesis of virus-specific antibodies. Affinity-mediated immunoblot analysis revealed a broad pattern of virus-specific antibodies with embedded clusters of restricted heterogeneity, but no signs of oligoclonal Ig production carrying non-viral specificity. From these data it was concluded that BN rats do control the intracerebral spread of JHM virus effectively by a strong local virus-specific antibody response, thereby preventing a clinically apparent disease.

Characterization of JHMV variants isolated from rat brain and cultured neural cells after wild type JHMV infection

After intracerebral inoculation of wild type (wt) JHMV into 4 to 5 week-old Lewis rats, only variants with larger mRNA3 were selectively propagated and no wt JHMV was reisolated from the brain. Detailed analysis of a cloned virus from infected rat brain, c1-2, showed that the virus had larger mRNAs 2, 2a and 3 as compared with those of wt JHMV, while there was no such difference for other mRNAs. The E2 glycoprotein of a variant virus was also shown to be larger as compared with that of wt JHMV. Such selective replication of variants were also observed in neural cell culture after infection with wt JHMV. However, these variants isolated from the brain of infected rat (c1-2) and from infected neural cells (CNS virus) differed from each other in the amounts of mRNAs 2 and 2a as well as 65 K protein. All of these data suggest that the viruses with larger E2 glycoprotein have the growth advantage in rat brain cells, which could be responsible for acute encephalitis of rats after infection with wt JHMV.

Coronavirus JHM induced demyelinating disease: specific domains on the E2-protein are associated with neurovirulence

Infections of rodents by murine coronaviruses can lead to chronic diseases of the central nervous system. These infections are interesting systems to study mechanisms which could be relevant for the pathogenesis of certain human diseases. One major factor influencing the outcome of infection is related to the virus. To understand the virological basis for neurovirulence we compared JHM-virus isolates with different biological properties. JHM-Wt causes only acute disease, JHM-Ts43 a demyelinating encephalomyelitis and a virus shedded from persistently infected cells (JHM-Pi) is not virulent at all. The spread of these viruses in glial cell cultures reflects their different neurovirulence for animals. The peplomer E2 of these viruses reveals structural and antigenic differences. We characterised the epitopes of E2 with a panel of monoclonal antibodies. Four epitopes are associated with regions important for neutralisation, cell fusion and attachment. More than five epitopes are not related to such functions. Epitopes differ in their location and accessibility on the E2 protein subunits between JHM-Wt, JHM-Ts43 and JHM-Pi. To identify epitopes in regions important for pathogenesis, we performed animal studies with variants selected by monoclonal antibodies. Variants changed in a defined epitope (E2-Ba) induce in Balb/c mice a chronic disease. Variants changed in only one of the other three neutralisation epitopes induce acute disease. These results support and extend the observation that the peplomer protein E2 is a major determinant for virulence and antigenic variability of coronaviruses 1,4,5,6,8,10,17,19,22,23. Increasing evidence had been obtained that certain structural features of this protein are important for the cell tropism of the virus. Furthermore, this protein influences strongly the type and specificity of immune responses against viral and host antigens. The highly advanced knowledge on structure and replication of coronaviruses will be of great value to analyze further mechanisms leading to inflammatory demyelinating diseases associated with a persistent virus infection.

Analysis of murine hepatitis virus (JHM strain) tropism toward Lewis rat glial cells in vitro. Type I astrocytes and brain macrophages (microglia) as primary glial cell targets

The murine hepatitis virus, JHM strain, causes a relapsing subacute demyelinating encephalomyelitis in Lewis rats after intracranial infection. The disease process involves both virus persistence within glial cells and the induction of autoimmunological attack of myelin, however, the relative importance of these features involved in chronic relapsing demyelination remains to be determined. In this report, we analyze the tropism of JHM virus to various neural cell types present within primary Lewis rat central nervous system cultures. Infection of primary cultures with JHM virus revealed that type I astrocytes and brain macrophages are the initial target cells of infection and that the myelin-forming oligodendrocytes are comparatively resistant, becoming infected only rarely through virus mediated cell fusion with previously infected cells. In addition, infection of cultures after removal of oligodendrocytes by various means had no effect on the tropism of JHM virus for the cultures. Cytopathic effects of JHM virus proceed rapidly by cell fusion within the astrocyte-macrophage monolayer, leaving the oligodendrocyte population largely unaffected. Therefore, the highly selective infection of type I astrocytes and macrophages appears to form the basis of JHM virus neurotropism in Lewis rats. These results indicate that JHM virus infection of astrocytes and brain macrophages may be more important in inducing chronic relapsing demyelinating processes than direct infection of the myelin-forming oligodendrocytes. Other possible pathways leading to chronic demyelination in rats involving type I astrocytes and brain macrophages are discussed.

Murine coronavirus-induced encephalomyelitis in rats: analysis of immunoglobulins and virus-specific antibodies in serum and cerebrospinal fluid

The humoral intrathecal immune response in coronavirus-induced demyelinating encephalomyelitis in rats associated with an autoimmune reaction to brain antigen, was analysed. The CSF of these animals revealed immune reactions which were directed against coronavirus and other, unknown, antigens. In general, no direct correlation between the disease, the state of the blood-brain barrier (BBB), intrathecal synthesis of Ig and the presence of virus-specific antibodies was detectable, suggesting that the humoral, in contrast to the cellular, immune response does not play a significant pathogenetic role in this CNS disease.

The effects of processing inhibitors of N-linked oligosaccharides on the intracellular migration of glycoprotein E2 of mouse hepatitis virus and the maturation of coronavirus particles

We have studied the effects of tunicamycin and inhibitors of the processing of N-linked glycans including N-methyl-1-deoxynojirimycin, castanospermine, mannodeoxynojirimycin, and swainsonine on the transport of glycoprotein E2 and the intracellular maturation of the coronavirus mouse hepatitis virus A59. Indirect immunofluorescence staining with monoclonal antibodies revealed that glycoprotein E2 exhibits different antigenic properties depending on the presence and on the structure of the N-linked oligosaccharides and that efficient transport of glycoprotein E2 to the plasma membrane requires the removal of glucose residues. In the presence of tunicamycin in the nonglycosylated E2 apoprotein was synthesized in normal amounts and readily acylated throughout the infectious cycle. This E2-species could not be detected on the surface of mouse hepatitis virus A59-infected cells with indirect immunofluorescence staining or lactoperoxidase labeling. N-Methyl-1-deoxynojirimycin and castanospermine, both of which selectively inhibited the processing glucosidases, caused a drop in virion formation by two log steps and a drastic delay in the surface expression of glycoprotein E2. The E2 species synthesized under such conditions was acylated but accumulated intracellularly in a compartment distinct from the Golgi. Concomitantly, synthesis of the matrix glycoprotein E1 of mouse hepatitis virus A59 was drastically impaired. Mannodeoxynojirimycin and swainsonine, which block later stages of the processing pathway, had less or no effect on the transport of glycoprotein E2 and the formation of virus particles.

Apolipoproteins AI, AII and HDL phospholipids but not APO-B are risk indicators for occlusive cerebrovascular disease

A variety of lipids, lipoprotein (Lp) lipids and APO-Lp were measured in 72 patients of both sexes suffering from cerebrovascular arteriopathy and compared with a control group matched for age and sex. The best discriminators by univariate analysis were serum concentrations of APO-AI, followed by APO-AII, high density lipoprotein phospholipids and HDL cholesterol (HDL-C). Low density lipoprotein cholesterol and serum APO-B values were lower in the patients than in the controls. With APO-AI only, patients and controls could be classified with 88-91% certainty. By combination of some of the variables which were selected by a stepwise discriminant analysis, several models were calculated resulting in 93-97% segregation of patients from controls. By multivariate analysis, APO-AI, APO-AII, HDL-C, and triglycerides in combination with the blood pressure or the body weight index were independent variables (in a mathematical sense). By comparing the present data with published results of previous studies it is concluded that cerebral atherosclerosis differs from other forms of atherosclerosis by several major risk indicators.

The effects of processing inhibitors of N-linked oligosaccharides on the intracellular migration of glycoprotein E2 of mouse hepatitis virus and the maturation of coronavirus particles

We have studied the effects of tunicamycin and inhibitors of the processing of N-linked glycans including N-methyl-1-deoxynojirimycin, castanospermine, mannodeoxynojirimycin, and swainsonine on the transport of glycoprotein E2 and the intracellular maturation of the coronavirus mouse hepatitis virus A59. Indirect immunofluorescence staining with monoclonal antibodies revealed that glycoprotein E2 exhibits different antigenic properties depending on the presence and on the structure of the N-linked oligosaccharides and that efficient transport of glycoprotein E2 to the plasma membrane requires the removal of glucose residues. In the presence of tunicamycin in the nonglycosylated E2 apoprotein was synthesized in normal amounts and readily acylated throughout the infectious cycle. This E2-species could not be detected on the surface of mouse hepatitis virus A59-infected cells with indirect immunofluorescence staining or lactoperoxidase labeling. N-Methyl-1-deoxynojirimycin and castanospermine, both of which selectively inhibited the processing glucosidases, caused a drop in virion formation by two log steps and a drastic delay in the surface expression of glycoprotein E2. The E2 species synthesized under such conditions was acylated but accumulated intracellularly in a compartment distinct from the Golgi. Concomitantly, synthesis of the matrix glycoprotein E1 of mouse hepatitis virus A59 was drastically impaired. Mannodeoxynojirimycin and swainsonine, which block later stages of the processing pathway, had less or no effect on the transport of glycoprotein E2 and the formation of virus particles.

Hybridoma antibodies to the murine coronavirus JHM: characterization of epitopes on the peplomer protein (E2)

A panel of hybridoma antibodies that react with the surface peplomer glycoprotein (E2) of the murine coronavirus JHM were produced to characterize major antigenic domains associated with functions related to virulence. Three groups of hybridoma antibodies were differentiated by immunoprecipitation of lysates from JHM-infected cells. One group precipitated the virion structural proteins gp170 and gp98 together with the intracellular form of E2, gp150. A second group reacted with gp98 and gp150, and a third group precipitated gp150 only. Competition assays with biotinylated hybridoma antibodies allowed the definition of at least six different epitope groups. Only those antibodies which immunoprecipitated both gp170 and gp98 neutralized infectivity, inhibited cell fusion and protected infected rats against acute disease. Another class of antibodies binding to gp170 and gp98 also neutralized JHM virus, but did not inhibit fusion and did not protect against disease. Antibodies that immunoprecipitated gp150 and gp98 revealed only weak neutralization and did not inhibit cell fusion or protect animals. Four epitopes were defined by antibodies that immunoprecipitated gp150, but revealed no biological activity. These data indicate that the site responsible for cell fusion is associated with an epitope group carried by gp170 and gp98. Neutralizing antibodies bind to this and another epitope. Furthermore, protection of JHM-infected rats against acute disease requires both inhibition of cell fusion and neutralization of virus.

Relapsing subacute demyelinating encephalomyelitis in rats during the course of coronavirus JHM infection

Temperature-sensitive mutants of the murine coronavirus JHM induced a subacute demyelinating encephalomyelitis (SDE) in young rats. Neurological symptoms were associated with marked lesions of primary demyelination in the white matter of the central nervous system (CNS), and developing after an incubation time of several weeks to months. Many rats survived this infection and recovered completely from this CNS disease. Among 43 survivors of SDE, 9 rats developed a relapse 27-153 days after onset of the first attack. Neuropathological examination of these animals revealed areas of fresh demyelination together with old remyelinated lesions. Viral antigens were detectable in the neighbourhood of fresh lesions and in some cases infectious virus was re-isolated from rats revealing low antibody titers to JHM virus. These results demonstrate that mutants of JHM virus can induce a relapsing demyelinating disease process, associated with a persistent infection, which possesses some similarities to chronic experimental allergic encephalomyelitis.