The hepatitis C virus (HCV)-Trimera mouse: a model for evaluation of agents against HCV

The lack of small-animal models that are suitable for evaluation of agents used to treat infection with hepatitis C virus (HCV) severely hinders the assessment of potential new therapies for the disease. This study created such a model, termed the "HCV-Trimera" model. The HCV-Trimera model was developed by using lethally irradiated mice, reconstituted with SCID mouse bone marrow cells, in which human liver fragments infected ex vivo with HCV had been transplanted. Viremia (positive-strand HCV RNA levels) in HCV-Trimera mice peaked at approximately day 18 after liver transplantation, and an infection rate of 85% was reached. Viral replication in liver grafts was evidenced by the presence of specific negative-strand HCV RNA. The usefulness of this model for evaluation of anti-HCV agents was demonstrated by the ability of a small molecule (an HCV internal ribosomal entry site inhibitor) and an anti-HCV human monoclonal antibody (HCV AB(XTL)68) to reduce virus loads in HCV-Trimera mice in a dose-dependent manner.

Hepatitis c virus infection in employees of a large university hospital in Israel

OBJECTIVE

To assess whether hospital work constitutes a risk factor for hepatitis C virus (HCV) infection among employees of a large hospital in Israel.

DESIGN

Seroprevalence survey.

SETTING

A 1,006-bed, tertiary-care university hospital in Jerusalem.

PARTICIPANTS

All 5,444 employees (18-65 years old) were eligible; 4,287 (79%) participated in the survey.

METHODS

Sera were tested for antibodies to HCV (anti-HCV) using a third-generation enzyme immunoassay. A third-generation strip immunoblot assay was used for confirmation. Participants were interviewed regarding their occupational history, and they completed a self-administered questionnaire covering history of non-occupational exposure to blood and country of birth. Other demographic information was obtained from the personnel department. Rates and odds ratios (ORs) were calculated, and multivariate logistic-regression analyses were performed to adjust for potential confounding variables.

RESULTS

Anti-HCV was found in 0.9% of employees (37/4,287; 95% confidence interval, 0.6-1.1), ranging from 0.1% among those born in Israel to 5.7% among those born in Central Asia. After age, gender, social status, country of birth, and history of blood transfusion were controlled for in a logistic regression, occupational exposure to blood > or = 10 years was significantly associated with the presence of antibodies (OR, 2.6; P=.01). Presence of anti-HCV also was associated with country of birth (range: Israel OR, 1; West OR, 3.8 [P=.1]; Central Asia OR, 48.6 [P<.0001]) and history of blood transfusion (OR, 2.7; P=.01). No significant associations were found between anti-HCV and age, gender, social status, history of tattoo, acupuncture, current occupation, department, exposure to blood in current occupation, adherence to safety precautions, or history of percutaneous injury. The association with length of exposure was stronger (OR, 3.6; P=.01) when the same logistic regression was run excluding the outlier ethnic group of Central Asia.

CONCLUSIONS

Hospital work does not seem to constitute a major risk factor for HCV infection in Israel today. A higher prevalence of anti-HCV among employees with longer versus shorter lengths of occupational exposure may be due to a cumulative effect of exposure over the years. Infection control efforts in recent years may have contributed to this association.

Imaging transgene expression in live animals

Monitoring the expression of therapeutic genes in targeted tissues in disease models is important to assessing the effectiveness of systems of gene therapy delivery. We applied a new light-detection cooled charged-coupled device (CCCD) camera for continuous in vivo assessment of commonly used gene therapy delivery systems (such as ex vivo manipulated cells, viral vectors, and naked DNA), without the need to kill animals. We examined a variety of criteria related to real-time monitoring of luciferase (luc) gene expression in tissues including bone, muscle, salivary glands, dermis, liver, peritoneum, testis, teeth, prostate, and bladder in living mice and rats. These criteria included determination of the efficiency of infection/transfection of various viral and nonviral delivery systems, promoter specificity, and visualization of luciferase activity, and of the ability of luciferin to reach various organs. The exposure time for detection of luc activity by the CCCD camera is relatively short (approximately 2 minutes) compared with the intensified CCD camera photon-counting method (approximately 15 minutes). Here we transduce a variety of vectors (such as viruses, transfected cells, and naked DNA) by various delivery methods, including electroporation, systemic injection of viruses, and tail-vein, high-velocity-high-volume administration of DNA plasmids. The location, intensity, and duration of luc expression in different organs were determined. The distribution of luciferin is most probably not a barrier for the detection of in vivo luciferase activity. We showed that the CCCD photon detection system is a simple, reproducible, and applicable method that enables the continuous monitoring of a gene delivery system in living animals.

Hyper-IL-6 gene therapy reverses fulminant hepatic failure

Fulminant hepatic failure is a catastrophic condition caused by massive hepatocellular apoptosis and necrosis. Inhibition of hepatocyte apoptosis and the enhancement of the endogenous potential for liver regeneration could potentially form an effective basis for treatment of this condition. In response to injury in the liver, IL-6 mediates the acute-phase response and induces both cytoprotective and mitogenic functions. Hyper-IL-6 is a superagonistic designer cytokine consisting of human IL-6 linked by a flexible peptide chain to the secreted form of the IL-6 receptor. In a mouse model of acute liver failure induced by d-galactosamine administration, a single low dose of a hyper-IL-6-encoding adenoviral vector, in contrast to an adeno-IL-6 vector, maintained liver function, prevented the progression of liver necrosis, and induced liver regeneration, leading to dramatically enhanced survival. Thus, hyper-IL-6 gene therapy may be useful for the treatment of fulminant hepatic failure, which is often fatal even following treatment by transplantation.

Lack of known hepatitis virus in hepatitis-associated aplastic anemia and outcome after bone marrow transplantation

Viral infection has been shown to induce aplastic anemia, unidentified types of hepatitis being the most common cause for aplastic anemia-associated viral hepatitis. The survival rate for this group of patients after bone marrow transplantation with stem cells from an HLA-matched sibling is not well known. The aim of this study was to determine the prevalence of hepatitis G virus (HGV) and transfusion transmitted virus (TTV) infection in non-A, non-B, non-C hepatitis associated-aplastic anemia (HAAA) patients, and to define the role of bone marrow transplantation (BMT) as a therapeutic modality for this disease. Sixty-eight patients (43 males and 25 females) with aplastic anemia, underwent allogeneic BMT at the Hadassah University Hospital between 1981 and 1997. Onset of hepatitis was defined as jaundice and elevated alanine aminotransaminase (ALT) levels. Onset of aplastic anemia was defined as the first date on which varying degrees of pancytopenia occurred: hemoglobin level below 10 g/dl, WBC below 2 x 10(9)/l and low platelet count 10 x 10(10)/l. Serial serum samples from HAAA patients were assayed for virological and/or serological markers of hepatitis A, B, C, D, E, G viruses, TTV and parvovirus B19. Seventeen of the 68 patients with aplastic anemia (25%) suffered from hepatitis, 12 males and five females, ages 5 to 36 years. The mean interval between onset of hepatitis and first indication of aplastic anemia was 62 days (range 14-225 days). The development of aplastic anemia was unrelated to age, sex or severity of hepatitis. Ten of the 17 patients (59%) achieved complete ALT recovery prior to the diagnosis of aplastic anemia. Serum samples were available for 15 patients; none had evidence of acute or active hepatitis A, B, C, D, E, G and TTV virus infection at the time of diagnosis. Parvovirus B19 DNA sequences were not detectable in 10 of 12 tested cases; two positive results were detected in serum samples obtained after blood transfusion, making the analysis of these positive results difficult. All 17 patients underwent BMT. The mean post-BMT follow-up period was 38 months (range 1 day-123 months), five patients (30%) died 1 to 160 days post BMT, and 12 (70%) are alive 31 to 123 months after BMT. Relapsing hepatitis was not observed in any of the patients. In conclusion, HAAA is a disease of the young and the etiologic agent associated with HAAA remains unknown. HGV, TTV and parvovirus B19 sequences were not detected in any of the HAAA cases. The survival rate after BMT with stem cells from an HLA-matched sibling is similar to that for patients with non-hepatitis-associated aplastic anemia.

Liver regeneration induced by a designer human IL-6/sIL-6R fusion protein reverses severe hepatocellular injury

The cytokine IL-6 plays a significant role in liver regeneration in conjunction with additional growth factors (HGF, TNF-alpha, and TGF-alpha). Many IL-6 effects depend on a naturally occurring soluble IL-6 receptor (sIL-6R). Here, the chimeric protein hyper-IL-6, constructed from the human IL-6 protein fused to a truncated form of its receptor, was found to have superagonistic IL-6 properties, and as such, enhanced liver cell regeneration. Hyper-IL-6 reversed the state of hepatotoxicity and enhanced the survival rates of rats suffering from fulminant hepatic failure after D-galactosamine administration. The hyper-IL-6 protein has a significant potential for use in the treatment of severe human liver diseases.

Preclinical evaluation of two human anti-hepatitis B virus (HBV) monoclonal antibodies in the HBV-trimera mouse model and in HBV chronic carrier chimpanzees

Two human monoclonal antibodies (mAbs) against hepatitis B surface antigen (HBsAg) generated in the Trimera mouse system are described. Both mAbs 17.1.41 and 19.79.5 are of the IgG1 isotype and have high affinity constants for HBsAg binding in the range of 10(-10) mol/L. Monoclonal antibody 17.1.41 recognizes a conformational epitope on the a determinant of HBsAg whereas mAb 19.79.5 recognizes a linear one. The 2 mAbs bind to a panel of hepatitis B virus (HBV) subtypes with distinct patterns. The neutralizing activity of these antibodies was tested in 2 different animal model systems. Administration of each mAb to HBV-Trimera mice, a system that provides a mouse model for human hepatitis B infection, reduced the viral load and the percentage of HBV-DNA-positive mice in a dose-dependent manner. These 2 mAbs were more effective than a polyclonal antibody preparation (Hepatect; Biotest Pharma, Dreieich, Germany) in both inhibition of HBV liver infection and reduction of viral load. A single administration of a mixture of these mAbs into HBV chronic carrier chimpanzees resulted in immediate reduction in HBsAg levels followed by recurrence to initial levels within few days. Thus, these mAbs may be potential candidates for preventive therapy or in combination with other antiviral agents against HBV. Further studies in humans are needed to assess these mAbs in various clinical indications.

Pancreatitis following hepatitis A vaccination

We describe a 23-year-old male patient who presented with epigastric abdominal pain, 8 days following vaccination with inactivated hepatitis A virus (Haverix(R)). Clinical and laboratory data confirmed the diagnosis of pancreatitis. Repeat polymerase chain reaction (PCR) for hepatitis A replication was negative. A comprehensive evaluation ruled out other etiologies for pancreatitis. IgM Hepatitis A antibodies did not develop even after 3 months. Pancreatitis following Hepatitis A is a well-known complication of the viremia, but the exact mechanism is controversial. We suggest that the pancreatitis may have been a cellular immunlogical reaction to one of the antigens of hepatitis A virus vaccine, or it might have been caused by the release of mediators of anaphylaxis such as histamine and leucotriens, induced by HAV antigens, resulting in pancreatitis without development of humoral immunization.

Human interleukin-6 facilitates hepatitis B virus infection in vitro and in vivo

BACKGROUND AND AIM

Research on hepatitis B virus (HBV) infection in vivo has been limited due to the absence of a suitable animal model. We have developed a human-mouse radiation chimera in which normal mice, preconditioned by lethal total body irradiation and radioprotected with SCID mouse bone marrow cells, are permissive for engraftment of human hematopoietic cells and solid tissues. This resulting human-mouse model, which comprises three genetically disparate sources of tissue, is therefore termed Trimera. This study was aimed at assessing the effect of human IL-6 on HBV infection in vivo in Trimera mice.

METHODS

Trimera mice were transplanted with human liver tissue fragments or with HepG2-derived cell lines, which had been previously infected ex vivo with HBV in the presence or absence of human interleukin-6 (hIL-6) and in the presence of anti-IL-6-neutralizing antibodies.

RESULTS

HBV sequences appeared in the sera of animals in which the liver tissue was incubated with both HBV and hIL-6 prior to transplantation. A similar result was obtained when a human hepatoblastoma cell line (HepG2), expressing the hIL-6 receptor, was infected ex vivo with HBV in the presence of hIL-6 prior to their injection into spleens of Trimera mice. However, when liver fragments were infected ex vivo and simultaneously treated with neutralizing antibodies against hIL-6 or were incubated with HBV prior to transplantation without hIL-6, the rate of mice positive for HBV DNA in their sera was lower. Human mononuclear cells are also permissive for HBV infection in vitro: in the presence of hIL-6 the infection of these cells is enhanced; and this infection is suppressed by the chimeric protein named Hyper-IL-6, generated by the fusion of hIL-6 to the soluble hIL-6 receptor (sIL-6Ralpha, gp80).

CONCLUSION

hIL-6 facilitates HBV infection in vitro and in vivo.

High susceptibility to bacterial infection, but no liver dysfunction, in mice compromised for hepatocyte NF-kappaB activation

Based on the essential involvement of NF-kappaB in immune and inflammatory responses and its apoptosis-rescue function in normal and malignant cells, inhibitors of this transcription factor are potential therapeutics for the treatment of a wide range of diseases, from bronchial asthma to cancer. Yet, given the essential function of NF-kappaB in the embryonic liver, it is important to determine its necessity in the liver beyond embryogenesis. NF-kappaB is normally retained in the cytoplasm by its inhibitor IkappaB, which is eliminated upon cell stimulation through phosphorylation-dependent ubiquitin degradation. Here, we directed a degradation-resistant IkappaBalpha transgene to mouse hepatocytes in an inducible manner and showed substantial tissue specificity using various means, including a new method for live-animal imaging. Transgene expression resulted in obstruction of NF-kappaB activation, yet produced no signs of liver dysfunction, even when implemented over 15 months. However, the transgene-expressing mice were very vulnerable both to a severe immune challenge and to a systemic bacterial infection. Despite having intact immunocytes and inflammatory cells, these mice were unable to clear Listeria monocytogenes from the liver and succumbed to sepsis. These findings indicate the essential function of the hepatocyte through NF-kappaB activation in certain systemic infections, possibly by coordinating innate immunity in the liver.

Transient transmission of hepatitis C virus from mothers to newborns

A study was performed in Israel to determine the rate of mother-to-infant HCV transmission in newborns at risk. A group of 22 HCV-infected mothers and their 23 newborns were followed up from early after birth by testing their serum for the presence of HCV antibodies and HCV-RNA. Antibody against HCV was detected in the blood of all newborns immediately after birth, but dropped to low or undetectable levels by 7 months of age. HCV-RNA was detected 2 days after birth in the blood of five infants (22%) but fell to undetectable levels by 6 months. HCV-HVR1 sequence analysis performed in one mother-infant pair on the second day after birth revealed two nucleotide changes. Two months later the same sequence was detected again in the HVR1, suggesting a very low replication rate. Thus, the study showed that vertically transmitted HCV was eliminated in all newborn infants by 6 months after delivery, with concomitant disappearance of HCV antibodies. The mechanism of HCV elimination in newborns at risk remains to be elucidated.

Reduced hepatitis B virus surface antigen-specific Th1 helper cell frequency of chronic HBV carriers is associated with a failure to produce antigen-specific antibodies in the trimera mouse

In chronic hepatitis B virus (HBV) infection weak antiviral immune responses are associated with viral persistence. We studied possible immune deficits underlying the lack of serum antibodies of such patients against the HBV surface antigen (HBsAg) in a novel human/mouse chimeric model. A hepatitis B surface antigen (HBs) vaccination of Balb/c mice engrafted with peripheral blood mononuclear cells (PBMC) of naturally HBV-immunized donors induced high frequencies of human HBsAg-specific B and T helper 1 (Th1) cells. These responses were associated with high serum anti-HBs antibody levels of the subclasses immunoglobulin G1 (IgG1) and IgG2 that are driven by interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). In contrast, PBMC of chronic HBV carriers transplanted into the chimera failed to produce anti-HBs antibodies after vaccination with HBsAg and exhibited a deficit of antigen-specific Th1 cells. A possible influence of HBsAg or viremia was excluded by the lack of viral replication in such chimera. The observed T-cell defect was specific for HBsAg, as the B- and T-cell responses to tetanus toxoid (TT) were fully retained. Thus, our study shows that viral persistence in chronic HBV carriers is associated with an HBsAg-specific Th1 cell defect, which likely is responsible for the insufficient neutralizing anti-HBs-antibody response and is not reversed by HBs vaccination. Alternative approaches to induce HBs-specific Th1 cell responses might represent a future therapeutic option.

Hepatitis E virus infection in travelers

Hepatitis E virus (HEV) is a major cause of clinical hepatitis in regions of endemicity, affecting primarily young adults and travelers to these areas. We present 5 cases of acute HEV infection in travelers and review 143 cases of HEV infection found by a literature search that were contracted in areas of endemicity. Fulminant hepatitis occurred in 2.7% of the reported cases; 2 of these were fatal. The destination of most of the travelers with acute HEV infection was the Indian subcontinent. The overall risk of contracting HEV infection for travelers appears to be lower than the risk for hepatitis A virus infection. Pregnant women and individuals with underlying liver disease may be a risk for severe infection.

Saccharomyces cerevisiae cells harboring the gene encoding sarcotoxin IA secrete a peptide that is toxic to plant pathogenic bacteria

Sarcotoxin IA is a cecropin-type antibacterial protein produced by the flesh fly, Sarcophaga peregrina. Similar to other bactericidal small proteins produced by insects, sarcotoxin IA is released into the hemolymph of larvae and nymphs upon mechanical injury or bacterial infection. The gene (sarco) that encodes this toxin was introduced into Saccharomyces cerevisiae yeast cells and was expressed under a constitutive yeast promoter. The transformed yeast cells were grown in a liquid medium, and a peptide with a similar molecular size to that of the mature sarcotoxin IA was detected in the medium by Western blot analysis. The secreted sarcotoxin-like peptide (SLP) had a potent cytotoxic effect against several bacteria, including plant pathogenic bacteria, similar to the toxic effects of the authentic sarcotoxin IA. Erwinia carotovora was more susceptible to the toxic medium than Pseudomonas solanacearum and Pseudomonas syringae pv. lachrymans. Thus, yeast may be used in the production of such proteins for employment against various bacterial pathogens.

Antigen-specific B and T cells in human/mouse radiation chimera following immunization in vivo

Adoptive transfer of human peripheral blood mononuclear cells (PBMC) into mice with severe combined immunodeficiency (SCID) or into lethally irradiated BALB/c mice radioprotected with SCID bone marrow, leads to marked engraftment of human T and B cells. In such chimeras, human serum antibody responses can be stimulated readily by vaccination with recall antigens, but the detection of antigen-specific functional T or B cells has been extremely difficult. In the present study, we were able to detect by Elispot analysis high frequencies of immunoglobulin G (IgG)-secreting B cells and mitogen-responsive interferon-gamma (IFN-gamma) or interleukin-4 (IL-4)-secreting T cells in peritoneum and spleen of human/BALB/c chimeric mice during the first 3 weeks after PBMC transfer. Moreover, specific memory responses were elicited by vaccination with tetanus toxoid (TT) or hepatitis B virus (HBV) surface (HBs) antigen of chimeric mice transplanted with PBMC derived from TT- or HBV-immune donors. Substantially higher TT-specific B-cell frequencies were found during the first 3 weeks after vaccination in mice challenged with the specific antigen compared to the levels found in control animals. High numbers of TT-specific IFN-gamma-secreting T cells persisted in the peritoneum of vaccinated, but not of unvaccinated, animals during the entire observation period, but only low numbers of specific IL-4-secreting T cells were found in vaccinated mice. Similar results were achieved following vaccination with HBs antigen of chimeric mice, transplanted with PBMC of HBV immunized donors. Thus, TT or HBsAg-specific antibody responses in our model correlate closely with the existence of specific IFN-gamma-secreting T helper 1/0 cells. Furthermore, these results show that adoptive transfer of human PBMC into lethally irradiated mice provides an efficient approach to generate specific B-cell fusion partners for the production of human monoclonal antibodies and specific T-cell lines for adoptive cell therapy of malignant or infectious diseases.

The hepatitis B virus-trimera mouse: a model for human HBV infection and evaluation of anti-HBV therapeutic agents

Previous studies have demonstrated the feasibility of implantation of human blood cells or tissues in lethally irradiated mice or rats, radioprotected with SCID mouse bone marrow cells: The Trimera system. In the present study, we describe the development of a mouse Trimera model for human hepatitis B virus (HBV) infection. In this model, viremia is induced by transplantation of ex vivo HBV-infected human liver fragments. Engraftment of the human liver fragments, evaluated by hematoxylin-eosin staining and human serum albumin mRNA expression, was observed in 85% of the transplanted animals 1 month postimplantation. Viremia levels were determined in these mice by measuring serum HBV DNA using polymerase chain reaction (PCR), followed by dot-blot hybridization. HBV DNA is first detected 8 days after liver transplantation. Viremia attains a peak between days 18 and 25 when HBV infection is observed in 85% of the transplanted animals. The HBV-Trimera model was used to evaluate the therapeutic effects of human polyclonal anti-HBs antibodies (Hepatect) and of two reverse-transcriptase inhibitors, lamivudine (3TC) and beta-L-5-fluoro-2',3'-dideoxycytidine (beta-L-5FddC). Treatment of HBV-Trimera mice with these drugs effectively reduced both the percentage of infected animals and the viral load in their sera. Treatment cessation resulted in rebound of viral load, indicating HBV replication upon drug withdrawal. These results show that the HBV-Trimera model represents a novel experimental tool for simulating human HBV infection and evaluating potential anti-HBV therapeutic agents.

Human monoclonal antibodies specific to hepatitis B virus generated in a human/mouse radiation chimera: the Trimera system

An approach to develop fully human monoclonal antibodies in a human/mouse radiation chimera, the Trimera system, is described. In this system, functional human lymphocytes are engrafted in normal strains of mice which are rendered immuno-incompetent by lethal total body irradiation followed by radioprotection with severe combined immunodeficient (SCID) mouse bone marrow. Following transplantation, human lymphocytes colonize murine lymphatic organs and secrete human immunoglobulins. We have established this system as a tool to develop fully human monoclonal antibodies, and applied it for the generation of monoclonal antibodies specific for hepatitis B virus surface antigen. A strong memory response to hepatitis B surface antigen was elicited in Trimera engrafted with lymphocytes from human donors positive for antibodies to hepatitis B surface antigen. The human specific antibody fraction in the Trimera was 10(2)-10(3)-fold higher as compared with that found in the donors. Spleens were harvested from Trimera mice showing high specific-antibody titres and cells were fused to a human-mouse heteromyeloma fusion partner. Several stable hybridoma clones were isolated and characterized. These hybridomas produce high-affinity, IgG, anti-hepatitis B surface antigen antibodies demonstrating the potential of the Trimera system for generating fully human monoclonal antibodies. The biological function and the neutralizing activity of these antibodies are currently being tested.

Suppression of human hepatoma in mice through adoptive transfer of immunity to the hepatitis B surface antigen

BACKGROUND/AIMS

Adoptive transfer of immunity against hepatitis B surface antigen (HBsAg) has previously been shown to occur in mice and humans through transplantation of bone marrow cells from donors immunized against HBsAg (anti-HBs) to non-immune recipients. In the present study we evaluated the effect of adoptive transfer of immunity to HBsAg on the growth of HbsAg-secreting hepatocellular carcinoma (HCC) xenografts in athymic mice.

METHODS

Immunocompetent mice were immunized with recombinant HBsAg. Bone marrow cells from anti-HBs+ mice were injected intravenously to irradiated athymic Balb/c mice which had been previously transplanted subcutaneously with Hep3B human hepatoma cells. Treatment groups included mice receiving bone marrow transplantation from HBV-immunized (anti-HBs positive) and non-immunized (anti-HBs negative) donors.

RESULTS

At 9 weeks post bone marrow transplantation, tumor volume and serum alpha-fetoprotein levels in athymic mice receiving HBV-immune bone marrow cells were 11.5 mm3 and 363 ng/ml, respectively, as compared to 1579 mm3 and 19,000 ng/ml, in recipients of non-immune bone marrow transplantation (p<0.005). T-cell depletion of antiHBs+ immune bone marrow prior to transplantation decreased the anti-tumor effect but did not abolish it. A mild nonspecific, bone marrow-derived, graft versus tumor effect was observed in mice transplanted with human hepatoma cells that do not express HBsAg.

CONCLUSIONS

Adoptive transfer of immunity to HBV facilitates suppression of experimental human HCC expressing HBsAg. This effect is the result of a combination of specific anti-viral surface antigen effect and a nonspecific graft versus tumor effect.

Comparison of methods for extraction of nucleic acid from hemolytic serum for PCR amplification of hepatitis B virus DNA sequences

The sensitivity of PCR for the amplification of target nucleic acid sequences in clinical diagnostics may often be reduced due to the presence of inhibitory factors. Hemolytic serum contains a number of PCR inhibitors, one of which is hemin. In this study we have found that conventional methods of DNA extraction were not sufficient for the removal of PCR-inhibitory compounds in hemolytic serum. We have therefore compared the efficiency of several commercial and noncommercial methods of nucleic acid purification from hemolytic serum samples prior to PCR amplification. Separation with the QIAamp HCV kit, dialysis with Millipore filters, and bovine serum albumin absorption were all found to be suitable extraction methods for eliminating inhibitors from hemolytic serum for PCR amplification. Using these methods we were able to detect very low levels of hepatitis B virus DNA in hemolytic serum.

Pregnancy associated with colon carcinoma overexpressing p53

The development of colon carcinoma during pregnancy is a rare event. However, when colon carcinoma develops during pregnancy it is considered a lethal coincidence due to rapid progression. We report two rare cases of colon adenocarcinoma diagnosed during gestation. Both tumors displayed increased nuclear immunostaining for p53. The increased expression of p53 in tumor cells could indicate that the p53 gene is either mutated or stabilized or alternatively overexpressed as a responses to DNA damage. It is hypothesized that the development of colon carcinoma during pregnancy can be attributed to alterations of the p53 tumor suppressor gene or gene product on one hand and a maternal immune-tolerant state on the other.

Tissue-Specific Expression of the Tobacco Mosaic Virus Movement Protein in Transgenic Potato Plants Alters Plasmodesmal Function and Carbohydrate Partitioning

Transgenic potato (Solanum tuberosum) plants expressing the movement protein (MP) of tobacco mosaic virus (TMV) under the control of the promoters from the class I patatin gene (B33) or the nuclear photosynthesis gene (ST-LS1) were employed to further explore the mode by which this viral protein interacts with cellular metabolism to change carbohydrate allocation. Dye-coupling experiments established that expression of the TMV-MP alters plasmodesmal function in both potato leaves and tubers when expressed in the respective tissues. However, whereas the size-exclusion limit of mesophyll plasmodesmata was increased to a value greater than 9.4 kD, this size limit was smaller for plasmodesmata interconnecting tuber parenchyma cells. Starch and sugars accumulated in potato leaves to significantly lower levels in plants expressing the TMV-MP under the ST-LS1 promoter, and rate of sucrose efflux from petioles of the latter was higher compared to controls. It is interesting that this effect was expressed only in mature plants after tuber initiation. No effect on carbohydrate levels was found in plants expressing this protein under the B33 promoter. These results are discussed in terms of the mode by which the TMV-MP exerts its influence over carbon metabolism and photoassimilate translocation, and the possible role of plasmodesmal function in controlling these processes.

Sanctuary of hepatitis B virus in bone-marrow cells of patients undergoing liver transplantation

Hepatitis B virus (HBV) reinfection after liver transplantation is a major problem. HBV is mainly a hepatotrophic virus but replicates in many extrahepatic tissues. We present here two cases of infected patients who underwent liver transplantation. Both underwent bone marrow (BM) and liver biopsies after transplantation. Biopsy specimens were stained for hepatitis B surface antigen (HB-sAg), and bone marrow aspirates and were separated for all subsets of cells. In both cases, HBV DNA analysis detected DNA in all BM fractions after transplantation, but HBV recurrence was found only in one case. We suggest that graft reinfection after liver transplantation may be caused by active replication of HBV in extrahepatic tissues and that BM cells are probably one of the major sanctuaries. The use of immunoprophylaxis based on BM-HBV studies is discussed.

Esophageal malignancy after liver transplantation in a patient with Barrett's esophagus

Patients undergoing liver transplantation are predisposed to develop extrahepatic malignancies. It is also known that patients with predisposed conditions, such as Barrett's esophagus, have higher rates of esophageal carcinoma. We present here a patient who underwent liver transplantation, had Barrett's esophagus, and developed esophageal malignancy a short time after transplantation. Liver transplantation may be associated with acceleration of the precancerous condition and the development of malignancies.

Case series: hyponatremia associated with moderate exercise

Exercise-induced hyponatremia is commonly believed to be associated only with extraordinary physical efforts, or particularly strenuous exercise. Hyponatremia complicating moderate exercise has not been described previously. The authors describe the characteristics of seven patients with life-threatening hyponatremia associated with mild to moderate exercise. All patients suffered from nausea, vomiting, agitation, and confusion, appearing during or after moderate physical activity. Grand mal convulsions occurred in five of the patients. In laboratory results, hyponatremia was as low as 115 mEq/L, with a relatively high sodium concentration in the urine. High serum creatine kinase activity levels were found in most of the patients. All patients were discharged in good condition, without neurologic sequela. The authors conclude that hyponatremia is a possible complication of moderate exercise, and not only of endurance sports, and that exercise-induced hyponatremia can produce severe neurologic manifestations. The mechanism of the hyponatremia is unclear, but may be due to a hemodynamically inappropriate stimulus for antidiuretic hormone secretion.

Human/mouse radiation chimera are capable of mounting a human primary humoral response

Lubin et al recently described a new approach that enables the generation of human/mouse chimera by adoptive transfer of human peripheral blood mononuclear cells (PBMC) into lethally irradiated normal strains of mice, radioprotected with bone marrow (BM) from donors with severe combined immune deficiency (SCID). In the present study, we demonstrate in such human/mouse chimera a marked humoral response to recall antigen, such as tetanus toxoid (TT) or hepatitis B surface antigen (HBsAg), as well as a significant primary response to keyhole limpet hemocyanin (KLH). Maximal anti-KLH response in human/Balb chimera was attained 2 to 4 weeks after the immunization and declined thereafter. One week after transplantation, the predominant anti-KLH subtype was IgM, while after 2 weeks, the dominance had shifted to IgG. Similar primary antibody response was also demonstrated against the human immunodeficiency virus (HIV) Nef protein. Comparison between human/Balb and human/SCID chimera showed a major difference in their ability to mount a primary response against KLH. In Balb/c recipients, more than half of the mice exhibited marked IgM titers against KLH, while there was hardly any anti-KLH IgM response in the SCID recipients. From the earliest time point onwards, when anti-KLH antibodies were found in the latter chimera, they were predominantly of the IgG type. We have previously shown that in human/Balb chimera, unlike in SCID recipients, dissemination of transplanted PBMC into the spleen and other internal organs occurs within 24 hours. Therefore, it is likely that the early seeding in the appropriate microenvironment of the lymphoid tissues, is crucial for the maintenance of virgin human B cells.

Hepatitis C virus viremia in SCID-->BNX mouse chimera

Chimpanzees are currently the only nonhuman animal model for reproducible propagation of hepatitis C virus (HCV). A chimeric mouse model was used for the induction of hepatitis C viremia, using BNX (beige/nude/X-linked immunodeficient) mice preconditioned by total body irradiation and reconstituted with SCID mouse bone marrow cells. HCV-infected liver fragments from patients with HCV RNA-positive sera were transplanted under the kidney capsule of the chimeric mice. HCV-specific RNA sequences were detected by reverse transcriptase nested polymerase chain reaction (RT-PCR) in serum of approximately 50% of grafted animals. In addition, normal liver specimens were incubated with HCV serum and transplanted into chimeric mice, leading to viremia in approximately 25% of animals. Sequential histologic evaluation of the liver implants, from day 2 to week 14 after transplantation, revealed loss of lobular architecture within the implants. However, viremia persisted for 10-50 days after transplantation. These results offer a new HCV model.

p53 expression in patients with cirrhosis with and without hepatocellular carcinoma

BACKGROUND

Mutated p53 acts as a dominant oncogene, whereas the wild type (wt) p53 gene product suppresses cell growth. Abnormalities in the p53 gene are reported in more than 50% of malignant tumors. Recently, an allelic loss of chromosome 17p, where the p53 gene is located, was found to be more frequent in hepatocellular carcinoma (HCC) cell lines and human tumors. In addition, in half of the cases of HCC from endemic areas for hepatitis B virus and aflatoxin, a hot spot point mutation at codon 249 was detected, as previously reported. Missense mutations in p53, mdm-2 complex formation, and other unknown mechanisms may lead to stabilization of the gene product, thus rendering it detectable by immunohistochemistry.

METHODS

To assess the relationship between p53 status at a premalignant stage and in HCC, the authors studied the immunohistologic expression of p53 in HCC and in the adjacent nontumorous resected liver tissue, using monoclonal antibody to wt and mutated p53.

RESULTS

Twelve of the 14 patients with liver tumors had HCC. Of the 12 patients with HCC and underlying cirrhosis, 8 (67%) had increased p53 expression in HCC cells. Eight of the 12 patients with p53-positive HCC cells had p53 overexpression in the nontumorous hepatocytes within regenerative nodules adjacent to HCC tissue. Three of 21 cirrhotic livers without a detectable tumor had increased p53 expression in the regenerative nodules. None of the 12 patients with chronic active hepatitis without cirrhosis or the 13 with a normal liver histology had increased p53 expression.

CONCLUSION

p53 overexpression in some cirrhotic livers and in nontumorous livers of patients with HCC may indicate a normal p53 gene response to cellular stress or, alternatively, to an abnormally or mutated p53 gene, and could occur before the development of HCC.

p53 expression in patients with cirrhosis with and without hepatocellular carcinoma

BACKGROUND

Mutated p53 acts as a dominant oncogene, whereas the wild type (wt) p53 gene product suppresses cell growth. Abnormalities in the p53 gene are reported in more than 50% of malignant tumors. Recently, an allelic loss of chromosome 17p, where the p53 gene is located, was found to be more frequent in hepatocellular carcinoma (HCC) cell lines and human tumors. In addition, in half of the cases of HCC from endemic areas for hepatitis B virus and aflatoxin, a hot spot point mutation at codon 249 was detected, as previously reported. Missense mutations in p53, mdm-2 complex formation, and other unknown mechanisms may lead to stabilization of the gene product, thus rendering it detectable by immunohistochemistry.

METHODS

To assess the relationship between p53 status at a premalignant stage and in HCC, the authors studied the immunohistologic expression of p53 in HCC and in the adjacent nontumorous resected liver tissue, using monoclonal antibody to wt and mutated p53.

RESULTS

Twelve of the 14 patients with liver tumors had HCC. Of the 12 patients with HCC and underlying cirrhosis, 8 (67%) had increased p53 expression in HCC cells. Eight of the 12 patients with p53-positive HCC cells had p53 overexpression in the nontumorous hepatocytes within regenerative nodules adjacent to HCC tissue. Three of 21 cirrhotic livers without a detectable tumor had increased p53 expression in the regenerative nodules. None of the 12 patients with chronic active hepatitis without cirrhosis or the 13 with a normal liver histology had increased p53 expression.

CONCLUSION

p53 overexpression in some cirrhotic livers and in nontumorous livers of patients with HCC may indicate a normal p53 gene response to cellular stress or, alternatively, to an abnormally or mutated p53 gene, and could occur before the development of HCC.

Hepatitis B virus infection associated with hematopoietic tumors

Hepatitis B virus (HBV) infection and replication have been linked to the development of hepatocellular carcinoma. Bone marrow-derived cells, as well as mesenchymal and epithelial cells, were recently shown to support HBV replication. We hypothesize that the mechanism that links HBV infection and liver tumors might also promote tumor development in tissues permissive for HBV replication. Between 1980 and 1993 we retrospectively identified 22 patients who were hepatitis B surface antigen (HBsAg) carriers and had extra-hepatic malignancies. These patients had 25 tumors, of which 22 were bone marrow derived. HBsAg was detected by immunohistochemistry in bone marrow cells of leukemia patient and of 3 of 10 lymphoma patients. In addition, in 4 of 10 patients with lymphoma, including 2 patients in which HBsAg stained bone marrow cells, HBsAg was also detected in the endothelial cells of blood vessels of the tumor tissue. These results suggest that the identification of an HBV gene product in endothelial cells might point to a role of HBV infection in the development of certain hematopoietic tumors, possibly through activation of cytokines or growth factors, which may eventually lead to bone marrow cell proliferation.

The tomato gene for the chloroplastic Cu,Zn superoxide dismutase: regulation of expression imposed in transgenic tobacco plants by a short promoter

The chloroplastic Cu,Zn superoxide dismutase (SOD) has an important role in the defense against damage by oxygen radicals in the chloroplasts. Here, for the first time, we report on the isolation of a genomic DNA clone from tomato that contains all the coding sequence for the chloroplastic Cu,Zn SOD as well as a 442 bp DNA fragment upstream of the translational initiation site. The latter upstream sequence has a putative TATA box and a 285 bp promoter region, 5' of the apparent transcriptional initiation and a 157 bp leader region. The coding sequence is composed of 8 exons that are interspaced by 7 introns; we termed this gene SODCp;Le:1. The 442 bp fragment was cloned into a pBI101 vector, upstream of the uidA (GUS) gene, via transcriptional fusion. Agrobacterium-mediated transformation resulted in transgenic tobacco plants. The progeny (after self-pollination) of 14 transformed plants, which expressed GUS above a threshold of 1 nmol/min per mg protein, were found to fall into two distinct groups. In the seedlings of 10 lines (group A) GUS expression was enhanced by exposure to light. In 4 lines of this group maintenance for 3 days in the dark eliminated GUS activity. The seedlings of group B expressed GUS regardless of the light/dark regime. In plants of group A, GUS expression was also developmentally regulated: high GUS activity in young leaves, low activity in mature leaves and no activity in the roots. The results suggest that this short chloroplastic Cu,Zn SOD promoter contains motifs for developmental (spatial) regulation as well as motifs responsive to light (or to oxygen radicals resulting from light-driven photosynthesis).

Prior hepatitis A virus infection enhances acute hepatitis E virus infection

The epidemiology and clinical manifestations of hepatitis E virus (HEV) and hepatitis A virus (HAV) are similar. However, two distinct diseases develop after exposure to each one of the viruses, which are apparently unrelated clinically. It is interesting to note that all reported epidemics and single cases of acute HEV infection indicate previous exposure to HAV. This fact leads us to hypothesize that acute HEV infection is dependent on past infection by hepatitis A virus, and that the sequential infections could not solely be explained on independent outbreaks. This hypothesis, where past HAV infection serves to support acute HEV infection, may have current practical implications, and could improve our understanding of the virology and pathophysiology of the disease.

Retinoblastoma and p53 tumor suppressor genes in human hepatoma cell lines

We analyzed the status of retinoblastoma and p53 genes in 10 human hepatoma cell lines. Polyclonal anti-peptide antibodies generated against peptides homologous to COOH-terminal and leucine-zipper domains of the retinoblastoma protein allowed us to identify two cell lines (Hep 3B and FOCUS) with abnormal expression. The same cell lines have both lacked p53 expression. In contrast to the retinoblastoma gene, the expression of the p53 gene was abnormal in six additional cell lines. Indeed, only the Hep G2 hepatoblastoma cell line (and its derivative Hep G2/2215) appeared to have normal p53 and retinoblastoma gene expression. Our studies indicate that p53 abnormalities are common but retinoblastoma gene aberrations are rare in human hepatoma cell lines.