Liver fibrosis progression is related to CD4 cell depletion in patients coinfected with hepatitis C virus and human immunodeficiency virus

A total of 204 patients with liver biopsy-proven hepatitis C virus (HCV) infection, 84 with and 120 without human immunodeficiency virus (HIV) coinfection, were studied, to evaluate variables possibly associated with the stage of liver fibrosis. All patients were injection drugs users, with a mean age of 32 years and an estimated duration of HCV infection of 12 years. Twenty-four patients (11%) had many fibrous septa with (5%) or without (6%) cirrhosis, 56 (27%) had few fibrous septa, and 124 (60%) had no fibrous septa. In all patients, an association was found between CD4 cell counts <500 cells/mm(3)and the presence of many fibrous septa (odds ratio, 3.2; P=.037), independent of HIV infection and other factors. These results suggest that HIV infection-induced CD4 depletion is independently associated with the severity of liver fibrosis in chronic HCV infection.

Hepatitis C virus lacking the hypervariable region 1 of the second envelope protein is infectious and causes acute resolving or persistent infection in chimpanzees

Persistent infection with hepatitis C virus (HCV) is among the leading causes of chronic liver disease. Previous studies suggested that genetic variation in hypervariable region 1 (HVR1) of the second envelope protein, possibly in response to host immune pressure, influences the outcome of HCV infection. In the present study, a chimpanzee transfected intrahepatically with RNA transcripts of an infectious HCV clone (pCV-H77C) from which HVR1 was deleted became infected; the DeltaHVR1 virus was subsequently transmitted to a second chimpanzee. Infection with DeltaHVR1 virus resulted in persistent infection in the former chimpanzee and in acute resolving infection in the latter chimpanzee. Both chimpanzees developed hepatitis. The DeltaHVR1 virus initially replicated to low titers, but virus titer increased significantly after mutations appeared in the viral genome. Thus, wild-type HCV without HVR1 was apparently attenuated, suggesting a functional role of HVR1. However, our data indicate that HVR1 is not essential for the viability of HCV, the resolution of infection, or the progression to chronicity.

Prospective evaluation of infection with hepatitis G virus in relation to hepatocellular carcinoma in Shanghai, China

The health consequences of hepatitis G virus (HGV) infection in humans remain to be determined. Inconsistent results of HGV and the risk of hepatocellular carcinoma (HCC) have been found in retrospective case-control studies. No prospective studies have addressed this issue. A prospective study including 18,244 men in Shanghai, China, was conducted to assess the role of HGV infection in HCC development. Serum HGV RNA and hepatitis B surface antigen (HBsAg) were assessed in 127 HCC case patients and 660 matched control subjects drawn from the cohort. Four patients with HCC (3.1%) and 21 control subjects (3.2%) were positive for serum HGV RNA. The presence of HGV RNA in prediagnostic serum was not associated with the risk of HCC (odds ratio, 1.0; 95% confidence interval, 0.3-2.9). No association between HGV RNA positivity and HCC risk was observed in either HBsAg-positive carriers or noncarriers. It is concluded that HGV infection plays no role in HCC development in this high-risk population.

Vaccination of chimpanzees with plasmid DNA encoding the hepatitis C virus (HCV) envelope E2 protein modified the infection after challenge with homologous monoclonal HCV

Hepatitis C virus (HCV) is an important cause of chronic liver disease worldwide. Development of vaccines to prevent HCV infection, or at least prevent progression to chronicity, is a major goal. In mice and rhesus macaques, a DNA vaccine encoding cell-surface HCV-envelope 2 (E2) glycoprotein stimulated stronger immune responses than a vaccine encoding intracellular E2. Therefore, we used DNA encoding surface-expressed E2 to immunize chimpanzees 2768 and 3001. Chimpanzee 3001 developed anti-E2 after the second immunization and antibodies to hypervariable region 1 (HVR1) after the third immunization. Although chimpanzee 2768 had only low levels of anti-E2 after the third immunization, an anamnestic response occurred after HCV challenge. CTL responses to E2 were not detected before challenge, but a strong response was detected after HCV challenge in chimpanzee 2768. An E2-specific CD4+ response was detected in chimpanzee 2768 before challenge and in both chimpanzees postchallenge. Three weeks after the last immunization, animals were challenged with 100 50% chimpanzee-infectious doses (CID(50)) of homologous monoclonal HCV. As a control, a naive chimpanzee was inoculated with 3 CID(50) of the challenge virus. The vaccine did not generate sterilizing immunity because both vaccinated chimpanzees were infected. However, both vaccinated chimpanzees resolved the infection early whereas the control animal became chronically infected. Compared with the control animal, hepatitis appeared earlier in the course of the infection in both vaccinated chimpanzees. Therefore, DNA vaccine encoding cell surface-expressed E2 did not elicit sterilizing immunity in chimpanzees against challenge with a monoclonal homologous virus, but did appear to modify the infection and might have prevented progression to chronicity.

Epidemiology of hepatocellular carcinoma

Although rare in Canada and the United States, hepatocellular carcinoma (HCC) ranks as the eighth most common cancer in the world. High-risk regions are East and Southeast Asia, and sub-Saharan Africa. Independent of race and geography, rates in men are at least two to three times those in women; this sex ratio is more pronounced in high-risk regions. Rates of HCC in the United States have increased by 70% over the past two decades. Registry data in Canada and Western Europe show similar trends. In contrast, the incidence of HCC in Singapore and Shanghai, China, both high-risk regions, has declined steadily over the past two decades. Among white and black Americans, there is an inverse relationship between social class status and HCC incidence. Chronic infection by the hepatitis B virus (HBV) is by far the most important risk factor for HCC in humans. It is estimated that 80% of HCC worldwide is etiologically associated with HBV. In the United States, although the infection rate in the general population is low, HBV is estimated to account for one in four cases of HCC among non-Asians. Chronic infection by the hepatitis C virus is another important risk factor for HCC in the United States; however, this virus is believed to play a relatively minor role in the development of HCC in Africa and Asia. Dietary aflatoxin exposure is an important codeterminant of HCC risk in Africa and parts of Asia. In Canada and the United States, excessive alcohol intake, cigarette smoking and oral contraceptive use in women also are risk factors for HCC.

NK cells cause liver injury and facilitate the induction of T cell-mediated immunity to a viral liver infection

NK cells are a relatively rare cell population in peripheral lymphoid organs but are abundant in the liver, raising questions as to their function in immune responses to infections of this organ. To investigate this, cell-mediated immunity to viral liver infection induced by a type 5, replication-defective, adenovirus was examined. It is shown that NK cells in the absence of T cells cause hepatocyte apoptosis in virus-infected livers associated with an increase in liver enzymes in the serum. Concomitantly, NK cells induce production of IFN-gamma, inhibitable by their elimination before infection. NK cells are shown to be necessary for optimal priming of virus-specific T cells, assessed by delayed-type hypersensitivity response and CTL activity, consistent with their ability to secrete IFN-gamma. The conclusion is drawn that NK cells mediate two important functions in the liver: they induce cell death in the infected organ and concomitantly stimulate the induction of T cell-mediated immunity by release of IFN-gamma.

Fas- and tumor necrosis factor receptor 1-dependent but not perforin-dependent pathways cause injury in livers infected with an adenovirus construct in mice

Intravenous injection of type 5 adenovirus, deleted in the E1 and E3 regions, is shown to result in expression of viral antigens in the liver, initiating lymphocyte infiltration and liver injury. Following this infection, induction of Fas ligand (FasL), tumor necrosis factor alpha (TNF-alpha), and perforin mRNA are all demonstrable in the liver, pointing to a role of respective pathways in liver injury. Making use of mice in which the genes coding for Fas, FasL, TNF receptors (TNFRs), and perforin are inactivated, as well as recombinant proteins that inhibit Fas- and TNF-alpha-mediated apoptosis, it is shown that a functional perforin-mediated mechanism is not obligatory for cellular infiltration and progression of liver injury. In contrast functional Fas- and TNF-alpha-mediated mechanisms were found to be essential for liver injury to occur. Results are presented demonstrating that signaling through TNFR1, but not TNFR2, is involved in TNF-alpha-mediated liver damage. The conclusion is drawn that although perforin mRNA is induced in the virus-infected liver, Fas- and TNF-alpha-mediated mechanisms constitute the principal pathways by which the cell-mediated immune system causes acute liver injury.

Functional inferences from reconstructed evolutionary biology involving rectified databases--an evolutionarily grounded approach to functional genomics

If bioinformatics tools are constructed to reproduce the natural, evolutionary history of the biosphere, they offer powerful approaches to some of the most difficult tasks in genomics, including the organization and retrieval of sequence data, the updating of massive genomic databases, the detection of database error, the assignment of introns, the prediction of protein conformation from protein sequences, the detection of distant homologs, the assignment of function to open reading frames, the identification of biochemical pathways from genomic data, and the construction of a comprehensive model correlating the history of biomolecules with the history of planet Earth.

Chronic infection with hepatitis G virus in relation to hepatocellular carcinoma among non-Asians in Los Angeles County, California

BACKGROUND

The recently identified hepatitis G virus (HGV) is a hepatotropic RNA virus belonging to the Flaviviridae family. The virus causes chronic viremia, and exposure to blood products is a recognized route of transmission in humans. To the authors' knowledge there is scant information regarding the hepatocarcinogenic potential of HGV. The current study examined the association between HGV infection and the risk of hepatocellular carcinoma.

METHODS

A population-based, case-control study involving 144 non-Asian patients with hepatocellular carcinoma who were ages 18-74 years at diagnosis and 252 community controls of similar age, gender, and race was conducted in Los Angeles, California. Study subjects were assessed for serologic markers of infections with the hepatitis B virus (hepatitis B surface antigen, antibody to the hepatitis B core antigen, and antibody to the hepatitis B surface antigen), hepatitis C virus (HCV) (anti-HCV and HCV RNA), and HGV (HGV RNA).

RESULTS

Twelve of the 144 hepatocellular carcinoma patients (8.3%) and 5 of the 252 control subjects (2.0%) were positive for serum HGV RNA. The presence of HGV RNA in the serum was associated with a statistically significant 5.4-fold risk of hepatocellular carcinoma (95% confidence limit, 1.8, 16.6). The excess risk for hepatocellular carcinoma among HGV-infected individuals was independent of the effects of hepatitis B and hepatitis C infections.

CONCLUSIONS

Chronic infection with HGV may play a role in the development of hepatocellular carcinoma. If the observed statistical association is a causal one, then infection with HGV may account for approximately 8% of hepatocellular carcinoma cases occurring in non-Asians in Los Angeles, California.

Chronic infection with hepatitis G virus in relation to hepatocellular carcinoma among non-Asians in Los Angeles County, California

BACKGROUND

The recently identified hepatitis G virus (HGV) is a hepatotropic RNA virus belonging to the Flaviviridae family. The virus causes chronic viremia, and exposure to blood products is a recognized route of transmission in humans. To the authors' knowledge there is scant information regarding the hepatocarcinogenic potential of HGV. The current study examined the association between HGV infection and the risk of hepatocellular carcinoma.

METHODS

A population-based, case-control study involving 144 non-Asian patients with hepatocellular carcinoma who were ages 18-74 years at diagnosis and 252 community controls of similar age, gender, and race was conducted in Los Angeles, California. Study subjects were assessed for serologic markers of infections with the hepatitis B virus (hepatitis B surface antigen, antibody to the hepatitis B core antigen, and antibody to the hepatitis B surface antigen), hepatitis C virus (HCV) (anti-HCV and HCV RNA), and HGV (HGV RNA).

RESULTS

Twelve of the 144 hepatocellular carcinoma patients (8.3%) and 5 of the 252 control subjects (2.0%) were positive for serum HGV RNA. The presence of HGV RNA in the serum was associated with a statistically significant 5.4-fold risk of hepatocellular carcinoma (95% confidence limit, 1.8, 16.6). The excess risk for hepatocellular carcinoma among HGV-infected individuals was independent of the effects of hepatitis B and hepatitis C infections.

CONCLUSIONS

Chronic infection with HGV may play a role in the development of hepatocellular carcinoma. If the observed statistical association is a causal one, then infection with HGV may account for approximately 8% of hepatocellular carcinoma cases occurring in non-Asians in Los Angeles, California.

Estimating the total number of protein folds

Many seemingly unrelated protein families share common folds. Theoretical models based on structure designability have suggested that a few folds should be very common while many others have low probability. In agreement with the predictions of these models, we show that the distribution of observed protein families over different folds can be modeled with a highly-stretched exponential. Our results suggest that there are approximately 4,000 possible folds, some so unlikely that only approximately 2,000 folds existing among naturally-occurring proteins. Due to the large number of extremely rare folds, constructing a comprehensive database of all existent folds would be difficult. Constructing a database of the most-likely folds representing the vast majority of protein families would be considerably easier.

Effects of iron loading on pathogenicity in hepatitis C virus-infected chimpanzees

Elevated iron levels have been associated with raised serum alanine transaminase (ALT) levels in hepatitis C virus (HCV)-infected humans. However, it is not clear if HCV infection causes increased iron accumulation by the liver or if the severity of HCV infection is actually worsened by higher iron levels in the host. To better understand the relationship between iron and persistent HCV infections, we examined the effect of excess dietary iron on disease severity in HCV-infected chimpanzees. Iron was supplemented in the diets of four HCV-infected and two uninfected chimpanzees for 29 weeks to achieve iron loading. Iron loading was confirmed by increases in serum iron levels, percentages of transferrin saturation, ferritin levels, elevations in hepatic iron concentration (HIC), and by histological examination. The majority of HCV-infected chimpanzees had higher iron levels before iron feeding than the uninfected animals. Although various degrees of iron loading occurred in all chimpanzees, HCV-infected animals exhibited increased loading in comparison with uninfected animals. The effects of iron loading on HCV disease expression was determined by comparing disease parameters during an extended baseline period before iron loading with the period during iron loading and immediately following iron loading. Iron loading did not influence the viral load, but did exacerbate liver injury in HCV-infected chimpanzees, as evidenced by elevated ALT and histological changes. Because all chimpanzees on high iron diets experienced iron loading, but pathological effects were only observed in HCV-infected chimpanzees, HCV infection appears to increase the susceptibility of the liver to injury following iron loading. These results confirm and extend previous observations made in human populations and serve to further validate the chimpanzee model of chronic hepatitis C.

Patients co-infected with human immunodeficiency virus and hepatitis C virus demonstrate higher levels of hepatic HCV RNA

Serum and liver hepatitis C virus (HCV) RNA levels in patients with hepatitis C have previously been quantified using different techniques. In this work, we used an automated, multicycle, polymerase chain reaction (PCR)-based technique to quantify HCV RNA in 1-2 mm of frozen liver tissue, and in serum, from 70 patients with antibodies to HCV (anti-HCV), with and without human immunodeficiency virus (HIV) co-infection. Stored liver tissue and sera collected at the time of liver biopsy were used for measurement of HCV RNA. Forty-eight HCV patients and 22 HIV/HCV co-infected patients were studied. Co-infected patients had significantly higher median serum and liver HCV RNA (6.7 log copies ml-1 serum and 2.90 log copies microg-1 liver nucleic acids) than patients with HCV alone (6.2 log copies ml-1 serum and 2.19 log copies microg-1 liver nucleic acids). There was only a weak correlation between serum and liver HCV RNA (r = 0.43). There was no correlation between liver and serum HCV RNA and host factors such as duration of disease, CD4 counts, alanine aminotransferase levels or histological score. There was no correlation with HCV genotype. Co-infected patients were more likely to harbour HCV genotype 1 (85%) when compared to patients with HCV alone (58%). An identical genotype was found in liver and serum in 89% of those tested; in 11%, a mixed genotype was present in serum. Patients with HCV genotypes 1 and non-1 had similar histological scores. Hence, an automated PCR-based technique is useful for measuring both liver and serum HCV RNA. Serum HCV genotypes closely paralleled those found in liver tissue. HIV co-infection was associated with higher serum, as well as intrahepatic, HCV RNA levels, by mechanisms not directly related to CD4 counts. The lack of correlation between liver HCV RNA and histology suggests that HCV is not directly cytopathic.

Experimental transmission of hepatitis C virus-associated fulminant hepatitis to a chimpanzee

Hepatitis C virus (HCV) was transmitted from a patient with fulminant hepatitis C to a chimpanzee. The patient had developed two episodes of fulminant hepatitis C, each occurring after a separate liver transplantation. Serial serum and liver samples from the patient and the chimpanzee were analyzed for HCV replication, genotype, quasispecies heterogeneity, and antibodies. In the patient, the levels of HCV replication in serum and liver correlated with the degree of hepatocellular necrosis and the clinical expression of fulminant hepatitis. The same HCV strain, genotype 1a, was recovered from both episodes of fulminant hepatitis. An unusually severe acute hepatitis was also observed in the chimpanzee. The viruses recovered from the patient and the chimpanzee were almost identical and displayed relatively little quasispecies heterogeneity. Thus, the same HCV strain induced two episodes of fulminant hepatitis in a single patient and severe hepatitis in a chimpanzee, suggesting that the pathogenicity or virulence of a specific HCV strain may be important in the pathogenesis of fulminant hepatitis C.

Lack of association between hepatitis C infection and development of AIDS-related lymphoma

Hepatitis C virus (HCV) has been associated with various lymphoproliferative disorders, and a high prevalence (9%-32%) of chronic HCV infection has been demonstrated among patients with lymphoma. Dual coinfection by HIV and HCV has been demonstrated in approximately 40% of certain populations of HIV-infected individuals. Because of this high prevalence of coinfection by HIV and HCV, the known relations between HCV and lymphoproliferative disorders, and the association of HIV and B cell lymphoma, the potential association between chronic HCV and the development of AIDS-related lymphoma was examined. The prevalence of HCV infection in HIV-infected patients with lymphoma was compared with that in patients with AIDS, diagnosed on the basis of an illness other than lymphoma. Risk factors for HCV infection, overall, were also evaluated. Evidence of HCV infection was ascertained by assessing anti-HCV antibodies, and HCV RNA in serum. The study consisted of 99 homosexual/bisexual men with AIDS-related lymphoma, and 43 other AIDS patients. HCV infection was detected in 11 of 99 (11.1 %) men with lymphoma, and in 5 of 43 (11.6%) other AIDS patients. Further, in patients with AIDS-related lymphoma, no relation was found between HCV infection and lymphoma histology or site. History of use of injected illicit drugs was associated with a significantly elevated risk of HCV infection in the combined group of lymphoma and other AIDS patients. The current study demonstrates no relation between dual infection by HIV and HCV and subsequent increased risk of lymphoma.

Genetic and experimental evidence for cross-species infection by swine hepatitis E virus

Prior to the recent discovery of the swine hepatitis E virus (swine HEV) in pigs from the midwestern United States, HEV was not considered endemic to this country. Since swine HEV is antigenically and genetically related to human strains of HEV, it was important to characterize this new virus further. The infectivity titer of a pool of swine HEV in pigs was determined in order to prepare a standardized reagent and to evaluate the dose response in pigs. Although the sequence of swine HEV varied extensively from those of most human strains of HEV, it was very closely related to the two strains of human HEV (US-1 and US-2) isolated in the United States. The U.S. strains which were recently recovered from two patients with clinical hepatitis E in the United States shared >/=97% amino acid identity with swine HEV in open reading frames 1 and 2. Phylogenetic analyses of different regions of the genome revealed that swine HEV and the U.S. strains grouped together and formed a distinct branch. These results suggested that swine HEV may infect humans. When we inoculated rhesus monkeys and a chimpanzee, experimental surrogates of humans, with swine HEV, the primates became infected. Furthermore, in a reciprocal experiment, specific-pathogen-free pigs were experimentally infected with the US-2 strain of human HEV that is genetically similar to swine HEV. These results provided experimental evidence for cross-species infection by the swine virus. Thus, humans appear to be at risk of infection with swine HEV or closely related viruses.

Experimental infection of chimpanzees with hepatitis C virus of genotype 5a: genetic analysis of the virus and generation of a standardized challenge pool

Six major genotypes (genotypes 1-6) of hepatitis C virus (HCV) have been identified. These genetic variants are being transmitted to chimpanzees, the only recognized animal model for the study of HCV. Genotype 5a (strain SA13), a variant found primarily in South Africa, has been transmitted to chimpanzees for the first time. Experimental infection of 2 chimpanzees was characterized by early appearance of viremia and peak virus titers of 10(5)-10(6) genome equivalents/mL. The HCV infection was resolved by week 15 after inoculation in 1 chimpanzee and persisted in the other. Both chimpanzees became anti-HCV-positive by week 14 after inoculation. Both chimpanzees developed viral hepatitis. The infectivity titer of a genotype 5a challenge pool prepared from the first passage of HCV in a chimpanzee was approximately 10(4) infectious doses/mL. Finally, sequence analysis of strain SA13 confirmed that genotype 5a is genetically distinct from other genotypes of HCV.

Utilization of chimeras between human (HM-175) and simian (AGM-27) strains of hepatitis A virus to study the molecular basis of virulence

Chimeras between human (HM-175) and simian (AGM-27) strains of hepatitis A virus (HAV) were constructed to evaluate the effect of the 2C gene of AGM-27 on HAV replication in cell culture and virulence in tamarins (Saguinus mystax) and chimpanzees (Pan troglodytes). Kinetic studies and radioimmunofocus assays demonstrated that replacement of the 2C gene of HAV/7, a cell culture-adapted strain of HM-175, with that of AGM-27 drastically reduced the ability of the virus to replicate in cultured cells. Intragenic chimeras containing AGM-27 sequences in either the 5' or 3' half of the 2C gene replicated in cell culture at an intermediate level. Whereas HAV/7 is attenuated for tamarins, a chimera containing the simian virus 2C gene in the HAV/7 background was virulent in tamarins, demonstrating that the simian virus 2C gene alone can confer the phenotype of virulence to an otherwise attenuated virus. Clusters of AGM-27-specific residues near both ends of the 2C protein were required for virulence since a chimera containing AGM-27 sequences in the carboxy-terminal half of 2C was partially attenuated for tamarins while one containing AGM-27 sequences only in the amino-terminal half of 2C was even more attenuated. Chimeras containing either the entire or only the 3' half of the simian virus 2C gene in the HAV/7 background were attenuated for chimpanzees.

Prevalence of hepatitis G virus RNA in the sera of patients with HIV infection

OBJECTIVE

The routes of transmission of the hepatitis G virus (HGV) are similar to those responsible for infection with HIV. We sought to evaluate the prevalence of HGV RNA in the sera of HIV-infected patients.

METHODS

The sera of 157 HIV-infected patients were assayed by reverse transcriptase-polymerase chain reaction (RT-PCR) using established primers for HGV. Patients were divided into group 1 (positive circulating hepatitis B surface antigen [HBsAg]), group 2 (positive anti-hepatitis C virus [HCV] antibody) and group 3 (without markers for HBV or HCV).

RESULTS

The overall prevalence of HGV RNA was 22%; prevalence was higher in group 1 (49%) than in groups 2 (16%) or 3 (7%). Patients with positive HGV RNA had laboratory values similar to HGV RNA-negative patients except for higher CD4 counts. Patients with an estimated risk duration of < or = 14 years were more likely to be HGV RNA-positive than patients at risk for >15 years. HGV RNA was found as frequently in patients with a homosexual lifestyle as in injection drug users (IDU). Multivariable analysis showed that the presence of HBsAg was the strongest factor associated with the presence of HGV RNA in serum.

CONCLUSIONS

Patients with HIV and HBV coinfection are significantly more likely to be HGV RNA-positive. Patients with a risk factor duration for >15 years were less likely to be HGV RNA-positive, pointing to a decrease in HGV RNA prevalence over time. This study supports the notion that homosexual lifestyle, in addition to injection drug usage and blood product transfusion, is a risk factor for HGV infection.

On the thermodynamic hypothesis of protein folding

The validity of the thermodynamic hypothesis of protein folding was explored by simulating the evolution of protein sequences. Simple models of lattice proteins were allowed to evolve by random point mutations subject to the constraint that they fold into a predetermined native structure with a Monte Carlo folding algorithm. We employed a simple analytical approach to compute the probability of violation of the thermodynamic hypothesis as a function of the size of the protein, the fraction of the total number of possible conformations which are kinetically accessible, and the roughness of the free-energy landscape. It was found that even if the folding is under kinetic control, the sequence will evolve so that the native state is most often the state of minimum free energy.

Experimental infection of chimpanzees with hepatitis G virus and genetic analysis of the virus

Hepatitis G virus (HGV) was transmitted to 2 chimpanzees by inoculation with human plasma containing approximately 10(8) genome equivalents (GE) of HGV. The infection was characterized by the late appearance (weeks 10 and 11 after inoculation [pi]) of viremia that persisted throughout the 120-week follow-up. Serum HGV titer increased steadily until it plateaued at 10(6)-10(7) GE/mL. However, despite this relatively high titer, neither of the chimpanzees developed hepatitis. The sequence of the viral genome, recovered from each chimpanzee at week 77 pi, differed from that of the inoculum by 5 nt (2 aa) and 27 nt (2 aa). Two more chimpanzees were inoculated with a first-passage plasma pool. The chimpanzee inoculated with approximately 10(6.7) GE of HGV had viremia at week 1 pi. However, the viral titer increased with the same kinetics as observed in the first passage. The second chimpanzee inoculated with approximately 10(4.7) GE of HGV had late appearance (week 7 pi) of viremia.

Update on chronic hepatitis: changing views on nomenclature and outcome

As old terminologies begin to fail, the author says that the world of hepatopathology is ready to reassess the classification of chronic hepatitis. This chapter reviews the current status of diagnostic features and terminologies for chronic B, C, and D hepatitis and discusses recent recommendations for future directions in nomenclature.

Recombinant vaccine against hepatitis E: dose response and protection against heterologous challenge

Thirty-two rhesus monkeys were used to evaluate the dose response of a recombinant HEV vaccine, and the efficacy of the vaccine based on the ORF2 protein of the Pakistani strain for pre- and post-exposure vaccination against intravenous challenge with homologous or heterologous virus was examined. Post-exposure vaccination did not protect animals against hepatitis. Although primates vaccinated twice with 50-microgram, 10-microgram, 2-microgram, or 0.4-microgram doses of the recombinant 55 kDa ORF-2 protein were infected, they were protected from hepatitis when they were challenged with very high doses of the homologous strain of HEV. Primates vaccinated twice with a 50 micrograms dose of the recombinant protein were protected from hepatitis after heterologous challenge with the Mexican strain, the strain of HEV most genetically distant from the Pakistani strain.

Evolution of model proteins on a foldability landscape

We model the evolution of simple lattice proteins as a random walk in a fitness landscape, where the fitness represents the ability of the protein to fold. At higher selective pressure, the evolutionary trajectories are confined to neutral networks where the native structure is conserved and the dynamics are non self-averaging and nonexponential. The optimizability of the corresponding native structure has a strong effect on the size of these neutral networks and thus on the nature of the evolutionary process.

The foldability landscape of model proteins

Molecular evolution may be considered as a walk in a multidimensional fitness landscape, where the fitness at each point is associated with features such as the function, stability, and survivability of these molecules. We present a simple model for the evolution of protein sequences on a landscape with a precisely defined fitness function. We use simple lattice models to represent protein structures, with the ability of a protein sequence to fold into the structure with lowest energy, quantified as the foldability, representing the fitness of the sequence. The foldability of the sequence is characterized based on the spin glass model of protein folding. We consider evolution as a walk in this foldability landscape and study the nature of the landscape and the resulting dynamics. Selective pressure is explicitly included in this model in the form of a minimum foldability requirement. We find that different native structures are not evenly distributed in interaction space, with similar structures and structures with similar optimal foldabilities clustered together. Evolving proteins marginally fulfill the selective criteria of foldability. As the selective pressure is increased, evolutionary trajectories become increasingly confined to "neutral networks," where the sequence and the interactions can be significantly changed while a constant structure is maintained.

Utility of a discriminant score for diagnosing advanced fibrosis or cirrhosis in patients with chronic hepatitis C virus infection

OBJECTIVE

The aim of the study was to assess the utility of a modified three-parameter cirrhosis discriminant score (CDS) for diagnosing advanced fibrosis or cirrhosis in patients with evidence of chronic hepatitis C.

METHODS

We examined liver tissue from 79 patients. Patients with a histological fibrosis score of 0-2 made up group A, and patients with a score of 3 or 4 (advanced fibrosis or cirrhosis) group B.

RESULTS

The modified CDS (possible total score 0-11) was derived from three laboratory parameters: platelets, ALT/AST ratio, and PT. The total score was significantly lower in group A (4.3 +/- 2.0) than in group B (7.9 +/- 1.4) (p < 0.0001). There was a positive correlation between the CDS and histological fibrosis score (r = 0.64,p < 0.0001). With 8 or above as the cutoff value, the CDS had a sensitivity of 46% and a specificity of 98% for the diagnosis of histological fibrosis scores of 3 or 4.

CONCLUSIONS

We conclude that a three-parameter CDS is useful for identifying patients with hepatitis C and a high likelihood of cirrhosis. Patients with a CDS < or =7 still require histological examination to identify advanced fibrosis or cirrhosis.

Presence of antibodies to the hepatitis B surface antigen is associated with an excess risk for hepatocellular carcinoma among non-Asians in Los Angeles County, California

Hepatocellular carcinoma (HCC) exhibits a more than 50-fold variation in incidence worldwide. High-risk regions include East Asia and sub-Saharan Africa, while non-Asians in the United States constitute a low-risk population. We assessed 111 cases of histologically confirmed HCC and 128 community control subjects among non-Asians of Los Angeles County for the presence in serum of hepatitis B surface antigen (HBsAg), antibodies to HBsAg (anti-HBs), antibodies to the hepatitis B core antigen (anti-HBc), HBV DNA, and antibodies to the hepatitis C virus (anti-HCV). Anti-HCV positivity was significantly associated with a 12.6-fold increase in HCC risk (95% confidence limits = 4.7, 33.6). As expected, the presence of serum HBsAg and the presence of anti-HBc in the absence of anti-HBs were both positively associated with the risk of HCC. But most interestingly, among our study subjects, the presence of anti-HBs in the absence of HBsAg and HBV DNA (indicative of a resolved infection) was significantly related to a 4.7-fold increased risk for HCC (95% confidence limits = 2.2, 9.4). Overall, any serological evidence of prior HBV exposure was associated with a 9.4-fold elevation in HCC risk (95% confidence limits = 4.7, 18.7). The data also demonstrate a synergistic effect of HBV and HCV infections on the risk of HCC. We estimate that about 55% of HCC cases occurring in non-Asians of Los Angeles can be attributed to infection by the hepatitis B and/or C viruses.

Progress toward the development of a genetically engineered attenuated hepatitis A virus vaccine

Mutations which positively affect growth of hepatitis A virus in cell culture may negatively affect growth in vivo. Therefore, development of an attenuated vaccine for hepatitis A may require a careful balancing of mutations to produce a virus that will grow efficiently in cells suitable for vaccine production and still maintain a satisfactory level of attenuation in vivo. Since such a balance could be achieved most directly by genetic engineering, we are analyzing mutations that accumulated during serial passage of the HM-175 strain of hepatitis A virus in MRC-5 cell cultures in order to determine the relative importance of the mutations for growth in MRC-5 cells and for attenuation in susceptible primates. Chimeric viral genomes of the HM-175 strain were constructed from cDNA clones derived from a virulent virus and from two attenuated viruses adapted to growth in African green monkey kidney (AGMK) and MRC-5 cells, respectively. Viruses encoded by these chimeric genomes were recovered by in vitro or in vivo transfection and assessed for their ability to grow in cultured MRC-5 cells or to cause hepatitis in primates (tamarins). The only MRC-5-specific mutations that substantially increased the efficiency of growth in MRC-5 cells were a group of four mutations in the 5' noncoding (NC) region. These 5' NC mutations and a separate group of 5' NC mutations that accumulated during earlier passages of the HM-175 virus in primary AGMK cells appeared, independently and additively, to result in decreased biochemical evidence of hepatitis in tamarins. However, neither group of 5' NC mutations had a demonstrable effect on the extent of virus excretion or liver pathology in these animals.

Effects of tumor necrosis factor-alpha and interleukin-6 on fluid-phase permeability and ammonia diffusion in CNS-derived endothelial cells

BACKGROUND

Proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) play an important role in the blood-brain barrier breakdown present in several neurological diseases including multiple sclerosis and AIDS. However, the specific effects of these cytokines on central nervous system-derived endothelial cells (CNS-EC) is not fully understood. In this study the effects of TNF-alpha and IL-6 were tested on different permeability mechanisms of CNS-EC.

METHODS

Central nervous system endothelial cells were isolated from human brain and retina and cultured in vitro in a transwell system. Fluid-phase endocytosis and transcytosis, absorptive-mediated endocytosis, and ammonia diffusion were measured with specific methods. Endothelial cells were studied with electron microscopy for the ultrastructural effects of cytokine stimulation.

RESULTS

Fluid-phase endocytosis and transcytosis were significantly increased by TNF-alpha and IL-6. This effect was dose dependent and reversible. The ammonia diffusion rate was also significantly increased by TNF-alpha. Absorptive-mediated endocytosis was not enhanced by TNF-alpha. Ultrastructural analysis of cytokine-treated CNS-EC confirmed the alterations in permeability showing an increase in endocytotic activity and a decrease in tight junctions.

CONCLUSIONS

The proinflammatory cytokines IL-6 and TNF-alpha induce specific changes in the morphology and permeability of CNS-EC. These alterations can be important in many diseases characterized by increased cytokine production.

Low prevalence of hepatitis C infection in hepatocellular carcinoma (HCC) cases and population controls in Guangxi, a hyperendemic region for HCC in the People's Republic of China

Southern Guangxi, China has one of the highest incidences of hepatocellular carcinoma (HCC) in the world. Serum samples collected from subjects of an earlier case-control study (39 cases, 41 controls) and from a random sampling of a residential male cohort (n = 100) were tested for antibodies for the hepatitis C virus (anti-HCV) using ELISA version 2.0 with confirmation by RIBA version 2.0. Only one of 141 (0.7%, upper 95% confidence limit, 3.2%) control subjects and none of 39 (upper 95% confidence limit, 6.07%) HCC cases tested positive for anti-HCV. Our results indicate that hepatitis C infection is not an important environmental determinant of HCC risk in this hyperendemic region.

Clinical significance of hepatitis C viral RNA status and its correlation to antibodies to structural HCV antigens in anti-HCV reactive patients with normal liver tests

Extensive serological testing and HCV RNA determination by RT-PCR was performed in serum, PBMCs, and liver tissue in thirteen anti-HCV reactive patients with persistently normal liver tests. Absolute concordance in the status of HCV RNA between serum, PBMCs, and liver was noted. Five patients were HCV RNA positive but only three had mild histological changes. Eight patients were HCV RNA negative in all three sites and had virtually normal liver histology. Patterns of reactivity in RIBA 2.0 strip immunoblot assay did not differentiate viremic from nonviremic patients. ELISA testing using multiple individual HCV recombinant antigens from the structural and non-structural regions of HCV demonstrated mean antibody titers to the structural antigens, in particular HCV E2 antibodies, to be significantly lower in HCV RNA negative patients. The status of HCV RNA in the serum appears to infer the status of HCV RNA in the liver and PBMCs in patients with persistently normal liver tests. Patients with persistently normal liver tests and undetectable HCV RNA have probably spontaneously cleared HCV infection.

Why are some proteins structures so common?

Many biological proteins are observed to fold into one of a limited number of structural motifs. By considering the requirements imposed on proteins by their need to fold rapidly, and the ease with which such requirements can be fulfilled as a function of the native structure, we can explain why certain structures are repeatedly observed among proteins with negligible sequence similarity. This work has implications for the understanding of protein sequence structure relationships as well as protein evolution.

A simian strain of hepatitis A virus, AGM-27, functions as an attenuated vaccine for chimpanzees

The AGM-27 strain OF hepatitis A virus (HAV) was originally isolated from an African green monkey with hepatitis and appears to represent a true simian strain. The virus caused acute hepatitis after intravenous inoculation into African green monkeys, rhesus monkeys, and marmosets. Cynomolgus monkeys inoculated with the virus did not develop hepatitis, probably because of prior exposure to HAV. Chimpanzees inoculated with a high dose of the virus did not develop signs of hepatitis, although the virus replicated and the animals seroconverted. Marmosets and chimpanzees convalescent from infection with the AGM-27 strain of HAV were rechallenged with the virulent HM-175 strain of human HAV. They were partially or totally protected from disease.

A cohort study of serum testosterone and hepatocellular carcinoma in Shanghai, China

A nested case-control study of HCC based on a cohort of 18,244 middle-aged men in Shanghai, China, who had been followed for an average of 5.3 years, was conducted. Our hypothesis dealt with the possible role of testosterone in the etiology of HCC, which shows a minimum of a 2- to 3-fold male excess in all populations world-wide. Seventy-six incident cases of HCC and 410 control subjects drawn from the cohort and individually matched to the cases by age (within 1 year), time of blood sample collection (within 1 month) and neighborhood of residence were assessed for serum HBsAg, anti-HBc, anti-HBs, anti-HCV and testosterone. Among controls, serum testosterone levels were similar between those who had no markers of HBV infection, those who were positive for anti-HBs only and those who were positive for anti-HBc but negative for HBsAg. However, the geometric mean level of testosterone in HBsAg-positive controls was 21% higher relative to HBsAg-negative controls and the difference was statistically significant (2-sided p = 0.0006). Relative to controls, HCC cases had a significantly higher mean level of testosterone at the time of recruitment (570 vs. 485 ng/dl, 2-sided p = 0.0005), but the difference was explicable on the basis of a higher proportion of HBsAg-positive individuals among cases than controls (p = 0.42 after adjustment for HBsAg status).

A hepatitis A virus deletion mutant which lacks the first pyrimidine-rich tract of the 5' nontranslated RNA remains virulent in primates after direct intrahepatic nucleic acid transfection

Cell culture-adapted variants of hepatitis A virus (HAV) in which the first pyrimidine-rich tract (pY1; nucleotides 99 to 138) of the 5' nontranslated region has been deleted (delta 96-137 or delta 96-139) replicate as well as parental virus in cultured cells (D.R. Shaffer, E.A. Brown, and S.M. Lemon, J. Virol. 68:5568-5578, 1994). To determine whether viruses with such large deletion mutations are able to replicate and to produce acute hepatitis in primates, we reconstructed the delta 96-137 deletion in the genetic background of a virulent virus which differs from the wild type by only one mutation in the 2B-coding region (HM175/8Y). Full-length synthetic delta 96-137/8Y RNA was injected into the livers of two HAV-seronegative marmosets (Saguinus mystax). Both animals developed serum liver enzyme elevations and inflammatory changes in serial liver biopsies within 3 to 4 weeks of inoculation which were comparable in magnitude to those observed previously following intrahepatic inoculation of marmosets with HM175/8Y RNA. Sequencing of RNA from virus shed in feces demonstrated the presence of the delta 96-137 deletion. These results indicate that the pY1 sequence of HAV is not required for efficient viral replication in hepatocytes in situ or for production of acute hepatic injury following intrahepatic RNA transfection in primates.

Optimal local propensities for model proteins

Lattice models of proteins were used to examine the role of local propensities in stabilizing the native state of a protein, using techniques drawn from spin-glass theory to characterize the free-energy landscapes. In the strong evolutionary limit, optimal conditions for folding are achieved when the contributions from local interactions to the stability of the native state is small. Further increasing the local interactions rapidly decreases the foldability.

Replication of hepatitis delta virus RNA in mice after intramuscular injection of plasmid DNA

To establish a readily manipulable small-animal system for the study of human hepatitis delta virus (HDV) replication in vivo, plasmid DNAs containing head-to-tail cDNA dimers of HDV were inoculated intramuscularly into mice. Genomic-sense HDV RNA was detected in the injected muscle within 1 week and increased to substantial levels by week 7 postinjection. The intramuscular accumulation of HDV RNA was determined to be the direct result of viral RNA replication by three lines of evidence: (i) injected tissues also accumulated antigenomic-sense HDV RNA, (ii) plasmid DNA that synthesized primary transcripts of antigenomic sense also led to the accumulation of genomic-sense HDV RNA, and (iii) injection of a cDNA dimer defective in antigenomic RNA cleavage failed to produce detectable HDV RNA in muscle. Immunohistochemical analysis of injected muscle demonstrated the presence and nuclear localization of hepatitis delta antigen in myocytes. Finally, sera from DNA-injected mice contained antibodies specific for delta antigen, indicating the induction of an immunological response to the intracellularly expressed antigen. These findings demonstrated the ability of HDV RNA to replicate in skeletal muscle and provide a useful system for the study of HDV replication, delta antigen processing, and its presentation to the immune system in vivo. Furthermore, this system offers an efficiently replicating RNA as a potential vehicle for in vivo gene transfer.

Transgenic mice support replication of hepatitis delta virus RNA in multiple tissues, particularly in skeletal muscle

Hepatitis delta virus (HDV) is hepatotropic and frequently causes fulminant hepatitis in both human and nonhuman primate hosts. To understand the molecular basis of HDV tissue tropism and the mechanism of pathogenesis, transgenic mice in which replication-competent HDV dimeric RNA is expressed under the control of either liver-specific or universal transcriptional promoters were developed. The expressed RNA replicated efficiently in the liver and several tissues of nonhepatic origin. Surprisingly, maximal replication of HDV RNA occurred in skeletal muscle and was almost 100-fold greater than in the liver. These findings suggest that the hepatotropism of HDV is most likely a receptor-mediated restriction and that muscle-specific factors may facilitate HDV RNA replication. No evidence of cytopathology was apparent in most of the tissues examined, including the liver, supporting the contention that hepatocellular disease is not mediated by direct cytopathological effects associated with HDV RNA replication and gene expression. However, mild muscle atrophy in some of the transgenic mice was noted. Delta antigen was detected in the nuclei of myocytes. Only the small form, not the large form, of delta antigen was detected, suggesting that the RNA editing event which causes the conversion of delta antigen did not occur in transgenic mice. Furthermore, the 0.8-kb antigenomic RNA species, which is postulated to be the mRNA for delta antigen, was not detected in mice. The preferential replication of HDV RNA in skeletal muscle suggests that HDV RNA replication can be facilitated by certain muscle-specific factors.

Differential toxicity of the protein phosphatase inhibitors microcystin and calyculin A

Microcystin (Mcyst) and calyculin A (CalA) in vitro inhibit protein phosphatases (PP)1 and 2A activity (IC50 0.1-2.0 nM). This study was aimed at determining the contribution of PP inhibition to Mcyst hepatotoxicity by comparing the effect of these two chemically different inhibitors in perfused rat livers. Both compounds (60 micrograms Mcyst and 6 micrograms CalA/150 ml perfusate) caused cessation of bile flow and inhibition of PP activity after 20 min of perfusion to 8% and 37% of control activity for Mcyst and CalA treatments, respectively. Histopathological findings included loss of cord sinusoidal pattern and of normal liver architecture. There also was hepatocyte swelling, pyknotic changes and necrosis. Mcyst caused a modest increase in perfusion pressure of 1.2 cm of water, whereas CalA caused a 3-fold increase. The most likely explanation for this hemodynamic effect is direct action of CalA on the vascular endothelium and/or sinusoidal and perisinusoidal cells. This possibility was explored with hepatocytes and sinusoidal endothelial cells. PP activity of both cell types was inhibited by 10 to 100 nM CalA followed later by cell lysis, whereas Mcyst (500 nM-2 microM) had no effect on sinusoidal endothelial cells, but inhibited PP activity and caused later lysis in hepatocytes (Mcyst 20-160 nM). Mcyst hepatotoxicity is therefore a direct consequence of PP inhibition in hepatocytes, the loss of sinusoidal integrity following from the primary toxic insult to the hepatocyte. Inhibition of PP activity of the cells of the presinusoidal vasculature and/or nonparenchymal cells results in hepatic hypertension.

Efficacy of an inactivated hepatitis A vaccine in pre- and postexposure conditions in marmosets

A two-part challenge study was done in marmoset monkeys to confirm the efficacy of an inactivated hepatitis A vaccine. In part 1 (preexposure), 7 marmosets received a single low dose of vaccine (360 ELISA units [EL.U.]) and were challenged orally with wild type hepatitis A virus (HAV) either 1 or 6 months later. In part 2 (postexposure), 8 marmosets were challenged orally with HAV and then half each were inoculated with a single dose of 360 or 1440 EL.U. of vaccine 2 days later. The suboptimal immune response elicited by the low vaccine dose in the preexposure group was sufficient to induce complete protection against oral challenge with heterologous HAV in all marmosets that had responded serologically. In the postexposure group, the 360-EL.U. dose of vaccine resulted in partial protection against hepatitis A disease, whereas the 1440-EL.U. dose of vaccine elicited complete protection against disease and virus excretion.

Successful passive and active immunization of cynomolgus monkeys against hepatitis E

Virtually full protection against hepatitis E and partial or complete protection against infection with hepatitis E virus (HEV) were achieved in passively or actively immunized cynomolgus monkeys. Hepatitis, viremia, and shedding of the virus in feces were detected in all nonimmunized animals that were challenged with HEV. HEV titers detected by reverse transcriptase PCR were higher in feces than in serum of nonimmunized animals. Anti-HEV antibody titers at the time of challenge ranged between 1:40 and 1:200 in animals passively immunized with convalescent plasma from a cynomolgus monkey previously infected with HEV and between 1:100 and 1:10,000 in animals actively immunized with a recombinant 55-kDa open reading frame 2 protein. The estimated 50% protective titer of passively acquired anti-HEV antibodies was 1:40. Although only one of four passively immunized animals showed histopathologic evidence of hepatitis, all four were infected after challenge; however, the titers of HEV in serum and feces were lower in the passively immunized animals than in the nonimmunized group. The actively immunized animals developed neither hepatitis nor viremia when challenged with HEV and virus was either not detected or was present in low titer in feces. The protective response was a function of the ELISA anti-HEV antibody titer at the time of challenge and the immunization schedule.

The effect of HIV disease on serum markers of hepatitis delta infection in intravenous drug abusers

The prevalence of serum markers of delta hepatitis was determined prospectively in 82 intravenous drug abusers at various stages of human immunodeficiency virus (HIV) disease. Seventeen were HIV negative, 30 were HIV positive without acquired immunodeficiency syndrome (AIDS) and 35 had been diagnosed as having AIDS. Antihepatitis D virus (HDV) in serum was measured by a commercially available enzyme-linked immunosorbent assay (ELISA) and also by solid phase capture radioimmunoassays (RIAs) for immunoglobulin G (IgG) and immunoglobulin M (IgM) anti-HDV. HDV antigen and hepatitis B virus (HBV) DNA were also measured. Hepatitis B surface antigen (HBsAg) and anti-HBs were determined by using a commercially available RIA. Anti-HDV (RIA) was only detected in serum that contained HBsAg. These anti-HDV (RIA) positive samples also tested positive with the commercial anti-HDV electroimmunoassay. In addition, the commercial anti-HDV ELISA detected anti-HDV in some serum samples that were negative for HBsAg; these anti HDV-positive HBsAg-negative samples were frequently lipemic or contained rheumatoid factor. The prevalence of HBsAg and anti-HBs did not differ significantly with the stage of HIV disease. HBsAg was detected in 3 of 13 (23%) HIV-negative, 5 of 29 (17%) HIV-positive, and 4 of 18 (22%) patients with AIDS. IgG and IgM anti-HDV (RIA) was positive in 2 of 3 HIV-negative and 4 of 5 HIV-positive pre-AIDS HBsAg-positive subjects. However, none of 4 AIDS patients had anti-HDV. The difference between AIDS and non-AIDS patients was statistically significant (Fisher's exact test, p = 0.03). HDV antigen was detected in serum from one AIDS patient.(ABSTRACT TRUNCATED AT 250 WORDS)