[Durable remission under dual HER2 blockade with Trastuzumab and Pertuzumab in a patient with metastatic gallbladder cancer]

Gallbladder cancer represents a rare but dismal disease. The only curative option is complete surgical resection, though patients often develop recurrent disease. In patients with advanced biliary tract cancer, the combination of cisplatin and gemcitabine showed a benefit in overall survival compared to gemcitabine alone. However, there is no standardized second-line regimen after treatment failure. We report on a young patient with early recurrence of a gallbladder cancer with cutaneous and peritoneal metastases. Upon identification of an ERBB2 gene amplification within the NCT MASTER (Molecularly Aided Stratification for Tumor Eradication Research) exome sequencing program with resulting overexpression of HER2 in the tumors cells, the patient received a targeted therapy with the HER2 antibodies pertuzumab and trastuzumab in combination with nab-paclitaxel, which led to a durable remission for more than one year. This case report underlines the potential of molecularly aided personalized targeted therapy for patients with biliary tract cancer and the need for respective clinical trials.

Tumoral Immune Cell Exploitation in Colorectal Cancer Metastases Can Be Targeted Effectively by Anti-CCR5 Therapy in Cancer Patients

The immune response influences the clinical course of colorectal cancer (CRC). Analyzing the invasive margin of human CRC liver metastases, we identified a mechanism of immune cell exploitation by tumor cells. While two distinct subsets of myeloid cells induce an influx of T cells into the invasive margin via CXCL9/CXCL10, CCL5 is produced by these T cells and stimulates pro-tumoral effects via CCR5. CCR5 blockade in patient-derived functional in vitro organotypic culture models showed a macrophage repolarization with anti-tumoral effects. These anti-tumoral effects were then confirmed in a phase I trial with a CCR5 antagonist in patients with liver metastases of advanced refractory CRC. Mitigation of tumor-promoting inflammation within the tumor tissue and objective tumor responses in CRC were observed.

Patients with Advanced Pancreatic Cancer and Hyperbilirubinaemia: Review and German Expert Opinion on Treatment with nab-Paclitaxel plus Gemcitabine

In patients with advanced unresectable pancreatic cancer, the prognosis is generally poor. Within recent years, new treatment options such as the FOLFIRINOX regimen (5-fluorouracil, leucovorin, irinotecan and oxaliplatin) or the combination of nanoparticle albumin-bound (nab)-paclitaxel plus gemcitabine have shown a clinically relevant survival benefit over the standard gemcitabine in patients with good performance status. Unfortunately, patients with hyperbilirubinaemia, who constitute a substantial proportion of the pancreatic cancer patients, have been excluded from most clinical studies. Consequently, our knowledge on the appropriate medical treatment of this patient group is limited. In a meeting of German medical oncology experts, the available clinical evidence and own clinical experience regarding the management of patients with advanced pancreatic cancer and hyperbilirubinaemia was discussed. The present publication summarises the discussion outcomes with regard to appropriate management of these patients, including consensus-based recommendations for nab-paclitaxel/gemcitabine treatment, according to the best available evidence. In summary, knowledge of the underlying aetiology of hyperbilirubinaemia and the metabolisation routes of the cytotoxic drugs is crucial before initiating chemotherapy. As effective treatment options should also be made available to patients with comorbid conditions, including hyperbilirubinaemia, the experts provide advice for an initial dose reduction of chemotherapy with nab-paclitaxel/gemcitabine based on the total bilirubin level in patients with biliary obstruction or extensive liver metastasis.

Adjuvant radiotherapy and chemoradiation with gemcitabine after R1 resection in patients with pancreatic adenocarcinoma

Background

The purpose of the study was to evaluate the effect of radiation therapy and chemoradiation with gemcitabine (GEM) after R1 resection in patients with pancreatic adenocarcinoma (PAC).

Methods

We performed a retrospective analysis of 25 patients who were treated with postoperative radiotherapy (RT) or chemoradiation (CRT) after surgery with microscopically positive resection margins for primary pancreatic cancer (PAC). Median age was 60 years (range 34 to 74 years), and there were 17 male and 8 female patients. Fractionated RT was applied with a median dose of 49.6 Gy (range 36 to 54 Gy). Eight patients received additional intraoperative radiotherapy (IORT) with a median dose of 12 Gy.

Results

Median overall survival (mOS) of all treated patients was 22 months (95% confidence interval (CI) 7.9 to 36.1 months) after date of resection and 21.1 months (95% CI 7.6 to 34.6 months) after start of (C)RT. Median progression-free survival (mPFS) was 13.0 months (95% CI 0.93 to 25 months). Grading (G2 vs. G3, P = 0.005) and gender (female vs. male, P = 0.01) were significantly correlated with OS. There was a significant difference in mPFS between male and female patients (P = 0.008). A total of 11 from 25 patients experienced local tumour progression, and 19 patients were diagnosed with either locoregional or distant failure.

Conclusions

We demonstrated that GEM-based CRT can be applied in analogy to neoadjuvant protocols in the adjuvant setting for PAC patients at high risk for disease recurrence after incomplete resection. Patients undergoing additive CRT have a rather good OS and PFS compared to historical control patient groups.

Anti-angiogenic activity of VXM01, an oral T-cell vaccine against VEGF receptor 2, in patients with advanced pancreatic cancer: A randomized, placebo-controlled, phase 1 trial

VEGFR-2 is expressed on tumor vasculature and a target for anti-angiogenic intervention. VXM01 is a first in kind orally applied tumor vaccine based on live, attenuated Salmonella bacteria carrying an expression plasmid, encoding VEGFR-2. We here studied the safety, tolerability, T effector (Teff), T regulatory (Treg) and humoral responses to VEGFR2 and anti-angiogenic effects in advanced pancreatic cancer patients in a randomized, dose escalation phase I clinical trial. Results of the first 3 mo observation period are reported. Locally advanced or metastatic, pancreatic cancer patients were enrolled. In five escalating dose groups, 30 patients received VXM01 and 15 placebo on days 1, 3, 5, and 7. Treatment was well tolerated at all dose levels. No dose-limiting toxicities were observed. Salmonella excretion and salmonella-specific humoral immune responses occurred in the two highest dose groups. VEGFR2 specific Teff, but not Treg responses were overall increased in vaccinated patients. We furthermore observed a significant reduction of tumor perfusion after 38 d in vaccinated patients together with increased levels of serum biomarkers indicative of anti-angiogenic activity, VEGF-A, and collagen IV. Vaccine specific Teff responses significantly correlated with reductions of tumor perfusion and high levels of preexisting VEGFR2-specific Teff while those showing no antiangiogenic activity had low levels of preexisting VEGFR2 specific Teff, showed a transient early increase of VEGFR2-specific Treg and reduced levels of VEGFR2-specific Teff at later time points - pointing to the possibility that early anti-angiogenic activity might be based at least in part on specific reactivation of preexisting memory T cells.

Chemotherapy for advanced pancreatic adenocarcinoma in elderly patients (≥70 years of age): a retrospective cohort study at the National Center for Tumor Diseases Heidelberg

BACKGROUND

Pancreatic cancer is mainly a disease of the elderly population, but clinical trials do not reflect this age distribution. Data on treatment strategies and outcome of older patients are limited. The aim of our study was to analyze safety and outcome in elderly patients with advanced pancreatic cancer treated with palliative chemotherapy at the outpatient clinic of the National Center for Tumor Diseases (NCT) at Heidelberg University Hospital.

MATERIALS AND METHODS

We retrospectively analyzed 53 patients ≥70 years using a prospectively maintained database. Requirements were (1) histologically proven diagnosis of ductal pancreatic adenocarcinoma, (2) age ≥70 at time of diagnosis of advanced disease, and (3) measurable advanced disease.

RESULTS

The median age was 73 years. 81% of the patients received a gemcitabine-based first-line therapy. Median overall survival was 6.7 months. Survival differed significantly between patient groups with low (≤1) and high (≥2) Eastern Cooperative Oncology Group performance status (7.8 vs. 3.9 months, p = 0.002). 30.2% of the patients developed side effects resulting in dosage reductions. 39.6% of the patients received second-line treatment. Residual survival after disease progression was significantly longer for second-line treatment compared to best supportive care (151 vs. 39 days, p = 0.019).

CONCLUSIONS

Overall, our older patients did not have an inferior outcome compared to the reported trial populations that included younger patients. Thus, palliative chemotherapy should be considered independently from chronological age, but the performance status should be carefully noticed. Second-line therapy should be considered for patients in good performance status after first progression.

Granulocyte-macrophage colony-stimulating factor-armed oncolytic measles virus is an effective therapeutic cancer vaccine

Oncolytic measles viruses (MV) derived from the live attenuated vaccine strain have been engineered for increased antitumor activity, and are currently under investigation in clinical phase 1 trials. Approaches with other viral vectors have shown that insertion of immunomodulatory transgenes enhances the therapeutic potency. In this study, we engineered MV for expression of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF). For the first time, therapeutic efficacy and adaptive immune response in the context of MV oncolysis could be evaluated in the previously established immunocompetent murine colon adenocarcinoma model MC38cea. MC38cea cells express the human carcinoembryonic antigen (CEA), allowing for infection with retargeted MV. Intratumoral application of MV-GMCSF significantly delayed tumor progression and prolonged median overall survival compared with control virus-treated mice. Importantly, more than one-third of mice treated with MV-GMCSF showed complete tumor remission and rejected successive tumor reengraftment, demonstrating robust long-term protection. An enhanced cell-mediated tumor-specific immune response could be detected by lactate dehydrogenase assay and interferon-γ enzyme-linked immunospot assay. Furthermore, MV-GMCSF treatment correlated with increased abundance of tumor-infiltrating CD3(+) lymphocytes analyzed by quantitative microscopy of tumor sections. These findings underline the potential of oncolytic, GM-CSF-expressing MV as an effective therapeutic cancer vaccine actively recruiting adaptive immune responses for enhanced therapeutic impact and tumor elimination. Thus, the treatment benefit of this combined immunovirotherapy approach has direct implications for future clinical trials.

Is preoperative chemotherapy followed by surgery the appropriate treatment for signet ring cell containing adenocarcinomas of the esophagogastric junction and stomach?

BACKGROUND

Recent data suggest primary resection as the preferable approach in patients with signet ring cell gastric cancer (SRC). The aim of our retrospective exploratory study was to evaluate the influence of SRC on prognosis and response in esophagogastric adenocarcinoma treated with neoadjuvant chemotherapy.

METHODS

A total of 723 locally advanced esophagogastric adenocarcinomas (cT3/4 N any) documented in a prospective database from two academic centers were classified according to the WHO definition for SRC (more than 50 % SRC) and analyzed for their association with response and prognosis after neoadjuvant treatment.

RESULTS

A total of 235 tumors (32.5 %) contained SRC. Median survival of SRC was 26.3 compared with 46.6 months (p < 0.001) for non-SRC. SRC were significantly associated with female gender, gastric localization, advanced ypT and R1/2 categories, and lower risk of surgical complications and anastomotic leakage (each p < 0.001). Clinical (21.1 vs. 33.7 %, p = 0.001) and histopathological response (less than 10 % residual tumor: 16.3 vs. 28.9 %, p < 0.001) were significantly less frequent in SRC. Clinical response (p = 0.003) and complete histopathological response (pCR) (3.4 %) (p = 0.003) were associated with improved prognosis in SRC. Clinical response, surgical complications, ypTN categories, but not SRC were independent prognostic factors in forward Cox regression analysis in R0 resected patients. Risk of peritoneal carcinomatosis was increased (p < 0.001), while local (p = 0.015) and distant metastases (p = 0.02) were less frequent than in non-SRC.

CONCLUSIONS

Prognosis of SRC is unfavorable. Although response to neoadjuvant chemotherapy is rare in SRC, it is associated with improved outcome. Thus, chemotherapy might not generally be abandoned in SRC. A stratification based on SRC should be included in clinical trials.

Successful treatment with nab-paclitaxel and gemcitabine after FOLFIRINOX failure in a patient with metastasized pancreatic adenocarcinoma

BACKGROUND

Advanced pancreatic adenocarcinoma still remains associated with a desperate prognosis. Nevertheless, treatment options for patients with metastasized disease have improved considerably over the last few years. Recently, cytotoxic combination therapies such as the FOLFIRINOX regimen and combined nab-paclitaxel/gemcitabine have shown improved overall survival compared to gemcitabine alone. There is still no standard of care in second-line therapy for patients with disease progression.

CASE REPORT

We report the case of a 47-year-old patient who dramatically responded to second-line treatment with nab-paclitaxel and gemcitabine after primary progression to the FOLFIRINOX protocol.

CONCLUSION

Second-line treatment after FOLFIRINOX is feasible for patients with good performance status. Our case report supports preclinical findings that suggest that pancreatic cancer is a heterogeneous disease. Further studies that characterize possible subgroups and identify predictive molecular markers to guide therapy are warranted.

Prognostic impact of lymph node involvement and the extent of lymphadenectomy (LAD) in adenocarcinoma of the esophagogastric junction (AEG)

BACKGROUND

The prognostic importance of lymph node (LN) involvement for patients with adenocarcinoma of the esophagogastric junction (AEG) is well-known. In the latest edition of the UICC staging system, the number of metastatic LNs was taken into account, while the extent of lymphadenectomy (LAD) remains unaddressed. Removal of at least six LNs is recommended, but there is no defined minimum number as to classify as (y)pN0. We examined the prognostic value of the number of positive LNs, number of LNs removed, and LN ratio (LNR) in order to determine the influence of an adequate LAD on overall survival (OS).

METHODS

We analyzed data of 316 patients with AEG treated in our institution (2001-2011) regarding clinicopathological data, treatment, morbidity, mortality, and long-term prognosis. Univariate and multivariate analysis was performed using Cox regression to evaluate the prognostic impact of(y)pN category, number of LNs removed and LNR.

RESULTS

OS decreased with higher count of positive LNs (p < 0.001) and higher LNR (p < 0.001). Whether >6, >15, or >30 LNs were removed did not influence OS, neither in the entire study population nor within individual (y)pT or (y)pN categories. Multivariate analysis revealed LNR (p < 0.001) besides M category (p = 0.015) and tracheotomy during the postoperative course (p = 0.005) as independent predictors of OS.

CONCLUSION

The classification according to the number of involved LNs in the latest edition of the UICC staging system improves prognostication in patients with AEG. The importance of an adequate LAD is shown by the high prognostic relevance of the LNR rather than the absolute number of LNs removed.

Advanced-stage pancreatic cancer: therapy options

Pancreatic ductal adenocarcinoma is one of the most aggressive cancers, and surgical resection is a requirement for a potential cure. However, the majority of patients are diagnosed with advanced-stage disease, either metastatic (50%) or locally advanced cancer (30%). Although palliative chemotherapy is the standard of care for patients with metastatic disease, management of locally advanced adenocarcinoma is controversial. Several treatment options, including extended surgical resections, neoadjuvant therapy with subsequent resections, as well as palliative radiotherapy and/or chemotherapy, should be considered. However, there is little evidence available to support treatment options for locally advanced disease. As valid predictive biomarkers for stratification of therapy are not available today, future trials need to define the role of the different treatment options. This Review summarizes the current evidence and discusses available treatment options for both locally advanced and metastatic pancreatic adenocarcinoma.

Broadly neutralizing immune responses against hepatitis C virus induced by vectored measles viruses and a recombinant envelope protein booster

Hepatitis C virus (HCV) infection remains a serious public health problem worldwide. Treatments are limited, and no preventive vaccine is available. Toward developing an HCV vaccine, we engineered two recombinant measles viruses (MVs) expressing structural proteins from the prototypic HCV subtype 1a strain H77. One virus directs the synthesis of the HCV capsid (C) protein and envelope glycoproteins (E1 and E2), which fold properly and form a heterodimer. The other virus expresses the E1 and E2 glycoproteins separately, with each one fused to the cytoplasmic tail of the MV fusion protein. Although these hybrid glycoproteins were transported to the plasma membrane, they were not incorporated into MV particles. Immunization of MV-susceptible, genetically modified mice with either vector induced neutralizing antibodies to MV and HCV. A boost with soluble E2 protein enhanced titers of neutralizing antibody against the homologous HCV envelope. In animals primed with MV expressing properly folded HCV C-E1-E2, boosting also induced cross-neutralizating antibodies against two heterologous HCV strains. These results show that recombinant MVs retain the ability to induce MV-specific humoral immunity while also eliciting HCV neutralizing antibodies, and that anti-HCV immunity can be boosted with a single dose of purified E2 protein. The use of MV vectors could have advantages for pediatric HCV vaccination.

Fatal varicella in an immunocompromised adult associated with a European genotype E2 variant of varicella zoster virus

Varicella zoster virus (VZV) seronegative patients under immunosuppressive therapy are at risk for severe life-threatening varicella. A 25-year-old male patient presented with rash and hepatitis. He had been known to suffer from Crohn's disease and received immunosuppressive treatment with azathioprine. The patient showed dyspnoea, and presented with a generalized rash with vesicular lesions typical for herpesvirus infections. He was started immediately on acyclovir therapy. Varicella infection was determined in this VZV seronegative patient in rash vesicles, blood and tracheal secretions and a high VZV viral load was detected in these specimens. The causative agent was genotyped by sequencing of several genes as a variant of the European genotype E2 containing several unique single nucleotide polymorphisms. Despite all measures, there was progressive septic shock, and the patient died due to multi-organ failure. Immunocompromised adults without varicella history are at high risk to develop life-threatening complications of varicella. Antiviral therapy with acyclovir can only be successful when administered as early as possible on suspicion of varicella infection in this group of patients. The most effective method to prevent severe varicella in immunocompromised patients is active immunization prior to immunosuppressive therapy.

Lymphoma chemovirotherapy: CD20-targeted and convertase-armed measles virus can synergize with fludarabine

Combination chemotherapy regimen incorporating CD20 antibodies are commonly used in the treatment of CD20-positive non-Hodgkin's lymphoma (NHL). Fludarabine phosphate (F-araAMP), cyclophosphamide, and CD20 antibodies (Rituximab) constitute the FCR regimen for treating selected NHL, including aggressive mantle cell lymphoma (MCL). As an alternative to the CD20 antibody, we generated a CD20-targeted measles virus (MV)-based vector. This vector was also armed with the prodrug convertase purine nucleoside phosphorylase (PNP) that locally converts the active metabolite of F-araAMP to a highly diffusible substance capable of efficiently killing bystander cells. We showed in infected cells that early prodrug administration controls vector spread, whereas late administration enhances cell killing. Control of spread by early prodrug administration was also shown in an animal model: F-araAMP protected genetically modified mice susceptible to MV infection from a potentially lethal intracerebral challenge. Enhanced oncolytic potency after extensive infection was shown in a Burkitt's lymphoma xenograft model (Raji cells): After systemic vector inoculation, prodrug administration enhanced the therapeutic effect synergistically. In a MCL xenograft model (Granta 519 cells), intratumoral (i.t.) vector administration alone had high oncolytic efficacy: All mice experienced complete but temporary tumor regression, and survival was two to four times longer than that of untreated mice. Cells from MCL patients were shown to be sensitive to infection. Thus, synergy of F-araAMP with a PNP-armed and CD20-targeted MV was shown in one lymphoma therapy model after systemic vector inoculation.

An Immunocompetent Murine Model for Oncolysis with an Armed and Targeted Measles Virus

An immunocompetent model is required to test therapeutic regimens for clinical trials with the oncolytic measles virus (MV). Toward developing this model, a retargeted MV that enters murine colon adenocarcinoma cells forming tumors in syngeneic C57BL/6 mice was generated. Since MV infection tends to be less efficient in murine than in human cells, the targeted virus was also armed with the prodrug convertase, purine nucleoside phosphorylase (PNP), and named MV-PNP-antiCEA. We have shown before that in cultured cells, infection with this virus activated the prodrug, 6-methylpurine-2'-deoxyriboside (MeP-dR), causing extensive cytotoxicity. When injected intratumorally (IT), MV-PNP-antiCEA inhibited subcutaneous tumor growth marginally, but subsequent administration of the prodrug enhanced the oncolytic effect. Systemic delivery of MV-PNP-antiCEA alone had no substantial oncolytic effects, but in combination with the prodrug it was therapeutic, revealing synergistic effects between virus and prodrug. Immunosuppression with cyclophosphamide (CPA) retarded the appearance of MV neutralizing antibodies and enhanced oncolytic efficacy: survival was 100%, with 9 out of 10 animals going into complete remission. This immunocompetent murine model facilitates the testing of therapeutic regimens for clinical trials.

Tyrosine 110 in the measles virus phosphoprotein is required to block STAT1 phosphorylation

The measles virus (MV) P gene encodes three proteins: P, an essential polymerase cofactor, and C and V, which have multiple functions including immune evasion. We show here that the MV P protein also contributes to immune evasion, and that tyrosine 110 is required to block nuclear translocation of the signal transducer and activator of transcription factors (STAT) after interferon type I treatment. In particular, MV P inhibits STAT1 phosphorylation. This is shown not only by transient expression but also by reverse genetic analyses based on a new functional infectious cDNA derived from a MV vaccine vial (Moraten strain). Our study also identifies a conserved sequence around P protein tyrosine 110 as a candidate interaction site with a cellular protein.

Oncolytic efficacy and enhanced safety of measles virus activated by tumor-secreted matrix metalloproteinases

Cancer cells secrete matrix metalloproteinases (MMP) that degrade the extracellular matrix and are responsible for some hallmarks of malignant cancer. Many viruses, including a few currently used in oncolytic virotherapy clinical trials, depend on intracellular proteases to process their proteins and activate their particles. We show here for measles virus (MV) that particle activation can be made dependent of proteases secreted by cancer cells. The MV depends on the intracellular protease furin to process and activate its envelope fusion (F) protein. To make F protein activation cancer cell specific, we introduced hexameric sequences recognized by an MMP and identified the mutant proteins most effective in fusing MMP-expressing human fibrosarcoma cells (HT1080). We showed that an MMP inhibitor interferes with syncytia formation elicited by mutant F proteins and confirmed MMP-dependent cleavage by Edman degradation sequence analysis. We generated recombinant MVs expressing the modified F proteins in place of furin-activated F. These viruses spread only in cells secreting MMP. In nude mice, an MMP-activated MV retarded HT1080 xenograft growth as efficiently as the furin-activated MV vaccine strain. In MV-susceptible mice, the furin-activated virus caused lethal encephalitis upon intracerebral inoculation, whereas the MMP-activated did not. Thus, MV particle activation can be made dependent of proteases secreted by cancer cells, enhancing safety. This study opens the perspective of combining targeting at the particle activation, receptor recognition, and selective replication levels to improve the therapeutic index of MV and other viruses in ongoing clinical trials of oncolysis.

Envelope targeting: hemagglutinin attachment specificity rather than fusion protein cleavage-activation restricts Tupaia paramyxovirus tropism

To engineer a targeting envelope for gene and oncolytic vector delivery, we characterized and modified the envelope proteins of Tupaia paramyxovirus (TPMV), a relative of the morbilli- and henipaviruses that neither infects humans nor has cross-reactive relatives that infect humans. We completed the TPMV genomic sequence and noted that the predicted fusion (F) protein cleavage-activation site is not preceded by a canonical furin cleavage sequence. Coexpression of the TPMV F and hemagglutinin (H) proteins induced fusion of Tupaia baby fibroblasts but not of human cells, a finding consistent with the restricted TPMV host range. To identify the factors restricting fusion of non-Tupaia cells, we initially analyzed F protein cleavage. Even without an oligo- or monobasic protease cleavage sequence, TPMV F was cleaved in F1 and F2 subunits in human cells. Edman degradation of the F1 subunit yielded the sequence IFWGAIIA, placing the conserved phenylalanine in position 2, a novelty for paramyxoviruses but not the cause of fusion restriction. We then verified whether the lack of a TPMV H receptor limits fusion. Toward this end, we displayed a single-chain antibody (scFv) specific for the designated receptor human carcinoembryonic antigen on the TPMV H ectodomain. The H-scFv hybrid protein coexpressed with TPMV F mediated fusion of cells expressing the designated receptor, proving that the lack of a receptor limits fusion and that TPMV H can be retargeted. Targeting competence and the absence of antibodies in humans define the TPMV envelope as a module to be adapted for ferrying ribonucleocapsids of oncolytic viruses and gene delivery vectors.

Characterization of the Tupaia rhabdovirus genome reveals a long open reading frame overlapping with P and a novel gene encoding a small hydrophobic protein

Rhabdoviruses are negative-stranded RNA viruses of the order Mononegavirales and have been isolated from vertebrates, insects, and plants. Members of the genus Lyssavirus cause the invariably fatal disease rabies, and a member of the genus Vesiculovirus, Chandipura virus, has recently been associated with acute encephalitis in children. We present here the complete genome sequence and transcription map of a rhabdovirus isolated from cultivated cells of hepatocellular carcinoma tissue from a moribund tree shrew. The negative-strand genome of tupaia rhabdovirus is composed of 11,440 nucleotides and encodes six genes that are separated by one or two intergenic nucleotides. In addition to the typical rhabdovirus genes in the order N-P-M-G-L, a gene encoding a small hydrophobic putative type I transmembrane protein of approximately 11 kDa was identified between the M and G genes, and the corresponding transcript was detected in infected cells. Similar to some Vesiculoviruses and many Paramyxovirinae, the P gene has a second overlapping reading frame that can be accessed by ribosomal choice and encodes a protein of 26 kDa, predicted to be the largest C protein of these virus families. Phylogenetic analyses of the tupaia rhabdovirus N and L genes show that the virus is distantly related to the Vesiculoviruses, Ephemeroviruses, and the recently characterized Flanders virus and Oita virus and further extends the sequence territory occupied by animal rhabdoviruses.

A ferret model of canine distemper virus virulence and immunosuppression

Canine distemper virus (CDV) infects many carnivores, including ferrets and dogs, and is the member of the Morbillivirus genus most easily amenable to experimentation in a homologous small-animal system. To gain insights into the determinants of CDV pathogenesis, we isolated a strain highly virulent for ferrets by repeated passaging in these animals. Sequence comparison of the genome of this strain with that of its highly attenuated precursor revealed 19 mutations distributed almost evenly in the six genes. We then recovered a virus from a cDNA copy of the virulent CDV strain's consensus sequence by using a modified reverse genetics system based on B cells. We infected ferrets with this virus and showed that it fully retained virulence as measured by the timing of rash appearance, disease onset, and death. Body temperature, leukocyte number, lymphocyte proliferation activity, and cell-associated viremia also had similar kinetics. We then addressed the question of the relative importance of the envelope and other viral constituents for virulence. Viruses in which the envelope genes (matrix, fusion, and hemagglutinin) of the virulent strain were combined with the other genes of the attenuated strain caused severe rash and fever even if the disease onset was delayed. Viruses in which the nucleocapsid, polymerase, and phosphoprotein genes (coding also for the V and C proteins) of the virulent strain were combined with the envelope genes of the attenuated strain caused milder signs of disease. Thus, virulence-inducing mutations have accumulated throughout the genome.

TT virus as a human pathogen: significance and problems

In 1997 TTV was detected using representational difference analysis (RDA) in serum of a patient with posttransfusion hepatitis unrelated to known hepatitis viruses. The genome of TTV is a circular single-stranded DNA molecule of 3852 nt with negative polarity. TTV possibly can be grouped either into the existing family Circoviridae or into a recently established virus family "Circinoviridae". Analysis of the complete DNA nucleotide sequence of TTV identified three partially overlapping open reading frames (ORFs). Neither DNA nucleotide nor corresponding amino acid sequences of TTV do show significant homologies to known sequences. TTV DNA nucleotide sequences amplified by PCR from sera of different patients show considerable sequence variations. Although the natural route of transmission of TTV is still unknown, there is clear evidence for a transmission of TTV through blood and blood products. TTV DNA can be detected in the feces of infected individuals suggesting that it may be possible to attract TTV infection from environmental sources. Since the discovery of TTV, numerous studies have investigated the prevalence of TTV infections in different human population groups all over the world. All these studies are based on PCR detection systems, but the technical aspects of the PCR systems vary significantly between the different investigators. The results of the epidemiological studies do not show a clear picture. The discovery of TTV as a viral agent and particularly the identification of a high percentage of infected carriers in the healthy human population raises the following questions: Firstly, what is the origin and molecular relatedness of TT virus. Secondly, what is the significance of TTV as a human pathogen. And thirdly, what are the exact molecular mechanisms of viral replication. To answer these questions it will be necessary to determine the primary structure and the coding capacity of several TTV patient isolates.

Structural organization of a conserved gene cluster of Tupaia herpesvirus encoding the DNA polymerase, glycoprotein B, a probable processing and transport protein, and the major DNA binding protein

The Tupaia herpesviruses (THVs) have been isolated from malignant lymphoma tissue cultures and from degenerating lung and spleen cell cultures of tree shrews (Tupaia spp.). Recently we succeeded in the localization of the gene locus of the THV DNA polymerase (DPOL) gene within the viral genome. Based on these results the highly conserved gene cluster of herpesviruses encoding the DPOL, the glycoprotein B (gB), a probable processing and transport protein (PRTP), and the major DNA binding protein (DNBI) was characterized in the genome of THV strain 2 (THV-2) in its entirety. The complete nucleotide sequence of the gene cluster was determined and it was discovered that the THV-2 gene products are most closely related to the corresponding proteins of mammalian cytomegaloviruses. The transcriptional activity of the four genes was confirmed by amplification of a part of the corresponding mRNAs obtained from infected cell RNA by RT-PCR. The homology values and the overall structure of the gene cluster, that shows specific colinearity with the corresponding clusters of the mammalian cytomegaloviruses, is further evidence that THV-2 is a member of the subfamily Betaherpesvirinae.

Identification and characterization of the Tupaia herpesvirus DNA polymerase gene

Tupaia herpesviruses (THVs) have been isolated from malignant lymphomas and from degenerating lung or spleen cell cultures of tree shrews (Tupoia spp.), but because of a lack of genetic information the final classification of THVs is still open. In the present work the viral DNA polymerase (DPOL) gene was mapped within the genome of the different THV strains using PCR and degenerate oligonucleotide primers. Nucleotide sequences of the DPOL genes of THV strains 1 to 5 were determined and used for comparative analyses. The transcriptional activity of the THV-2 DPOL gene was confirmed by RT-PCR. It was found that the different THV strains are very closely related to each other. When compared to other herpesviruses the highest amino acid sequence identities detected were with DPOLs of the murine and human cytomegaloviruses. These results justify the conclusion that THVs are members of the subfamily Betaherpes-virinae.