Methodological quality of behavioural weight loss studies: a systematic review.

This systematic review assessed the methodological quality of behavioural weight loss intervention studies conducted among adults and associations between quality and statistically significant weight loss outcome, strength of intervention effectiveness and sample size. Searches for trials published between January, 2009 and December, 2014 were conducted using PUBMED, MEDLINE and PSYCINFO and identified ninety studies. Methodological quality indicators included study design, anthropometric measurement approach, sample size calculations, intent-to-treat (ITT) analysis, loss to follow-up rate, missing data strategy, sampling strategy, report of treatment receipt and report of intervention fidelity (mean = 6.3). Indicators most commonly utilized included randomized design (100%), objectively measured anthropometrics (96.7%), ITT analysis (86.7%) and reporting treatment adherence (76.7%). Most studies (62.2%) had a follow-up rate > 75% and reported a loss to follow-up analytic strategy or minimal missing data (69.9%). Describing intervention fidelity (34.4%) and sampling from a known population (41.1%) were least common. Methodological quality was not associated with reporting a statistically significant result, effect size or sample size. This review found the published literature of behavioural weight loss trials to be of high quality for specific indicators, including study design and measurement. Identified for improvement include utilization of more rigorous statistical approaches to loss to follow up and better fidelity reporting.

Randomized controlled trial of behavioral treatment for comorbid obesity and depression in women: the Be Active Trial.

OBJECTIVE: Depression is associated with increased risk for obesity and worse weight loss treatment outcomes. The purpose of the present study was to test the hypothesis that delivering evidence-based behavior therapy for depression before a lifestyle weight loss intervention improves both weight loss and depression. DESIGN: In a randomized controlled trial, obese women with major depressive disorder (N=161, mean age=45.9 (s.d.: 10.8) years) were randomized to brief behavior therapy for depression treatment followed by a lifestyle intervention (BA) or a lifestyle intervention only (LI). Follow-up occurred at 6 and 12 months. Main outcome measures included weight loss and depression symptoms. RESULTS: Intention-to-treat analyses revealed both conditions lost significant weight, but no differences between conditions in weight change at 6 months (BA=-3.0%, s.e.=-0.65%; LI=-3.7%, s.e.=0.63%; P=0.48) or 12 months (BA=-2.6%, s.e.=0.77%; LI=-3.1%, s.e.=0.74%; P=0.72). However, the BA condition evidenced significantly greater improvement in Beck Depression Inventory-II scores relative to the LI condition at both 6 months (BA mean change=-12.5, s.d.=0.85; LI mean change=-9.2, s.d.=0.80, P=0.005) and 12 months (BA mean change=-12.6, s.d.=0.97; LI mean change=-9.9, s.d.=0.93; P=0.045). Participants who experienced depression remission by 6 months (61.2%) lost greater weight (mean=-4.31%; s.e.=0.052) than those who did not (39.7%; mean=-2.47%, s.e.=0.53; P=.001). CONCLUSION: Adding behavior therapy to a lifestyle intervention results in greater depression remission but does not improve weight loss within 1 year. Improvement in depression is associated with greater weight loss.

Virus-specific mechanisms of carcinogenesis in hepatitis C virus associated liver cancer.

The development of hepatocellular carcinoma (HCC) in persons who are persistently infected with hepatitis C virus (HCV) is a growing problem worldwide. Current antiviral therapies are not effective in many patients with chronic hepatitis C, and a greater understanding of the factors leading to progression of HCC will be necessary to design novel approaches to prevention of HCV-associated HCC. The lack of a small animal model of chronic HCV infection has hampered understanding of these factors. As HCV is an RNA virus with little potential for integration of its genetic material into the host genome, the mechanisms underlying HCV promotion of cancer are likely to differ from other models of viral carcinogenesis. In patients persistently infected with HCV, chronic inflammation resulting from immune responses against infected hepatocytes is associated with progressive fibrosis and cirrhosis. Cirrhosis is an important risk factor for HCC independent of HCV infection, and a majority of HCV-associated HCC arises in the setting of cirrhosis. However, a significant minority arises in the absence of cirrhosis, indicating that cirrhosis is not a prerequisite for cancer. Other lines of evidence suggest that direct, virus-specific mechanisms may be involved. Transgenic mice expressing HCV proteins develop cancer in the absence of inflammation or immune recognition of the transgene. In vitro studies have revealed multiple interactions of HCV-encoded proteins with cell cycle regulators and tumor suppressor proteins, raising the possibility that HCV can disrupt control of cellular proliferation, or impair the cell's response to DNA damage. A combination of virus-specific, host genetic, environmental and immune-related factors are likely to determine the progression to HCC in patients who are chronically infected with HCV. Here, we summarize current knowledge of the virus-specific mechanisms that may contribute to HCV-associated HCC.

Gut microbes define liver cancer risk in mice exposed to chemical and viral transgenic hepatocarcinogens.

BACKGROUND AND AIMS: Hepatocellular carcinoma (HCC) frequently results from synergism between chemical and infectious liver carcinogens. Worldwide, the highest incidence of HCC is in regions endemic for the foodborne contaminant aflatoxin B1 (AFB1) and hepatitis B virus (HBV) infection. Recently, gut microbes have been implicated in multisystemic diseases including obesity and diabetes. Here, the hypothesis that specific intestinal bacteria promote liver cancer was tested in chemical and viral transgenic mouse models. METHODS: Helicobacter-free C3H/HeN mice were inoculated with AFB1 and/or Helicobacter hepaticus. The incidence, multiplicity and surface area of liver tumours were quantitated at 40 weeks. Molecular pathways involved in tumourigenesis were analysed by microarray, quantitative real-time PCR, liquid chromatography/mass spectrometry, ELISA, western blot and immunohistochemistry. In a separate experiment, C57BL/6 FL-N/35 mice harbouring a full-length hepatitis C virus (HCV) transgene were crossed with C3H/HeN mice and cancer rates compared between offspring with and without H hepaticus. RESULTS: Intestinal colonisation by H hepaticus was sufficient to promote aflatoxin- and HCV transgene-induced HCC. Neither bacterial translocation to the liver nor induction of hepatitis was necessary. From its preferred niche in the intestinal mucus layer, H hepaticus activated nuclear factor-kappaB (NF-kappaB)-regulated networks associated with innate and T helper 1 (Th1)-type adaptive immunity both in the lower bowel and liver. Biomarkers indicative of tumour progression included hepatocyte turnover, Wnt/beta-catenin activation and oxidative injury with decreased phagocytic clearance of damaged cells. CONCLUSIONS: Enteric microbiota define HCC risk in mice exposed to carcinogenic chemicals or hepatitis virus transgenes. These results have implications for human liver cancer risk assessment and prevention.

Role of Hepatitis C virus core protein in viral-induced mitochondrial dysfunction.

Hepatitis C virus (HCV) infection results in several changes in mitochondrial function including increased reactive oxygen species (ROS) production and greater sensitivity to oxidant, Ca(2+) and cytokine-induced cell death. Prior studies in protein over-expression systems have shown that this effect can be induced by the core protein, but other viral proteins and replication events may contribute as well. To evaluate the specific role of core protein in the context of viral replication and infection, we compared mitochondrial sensitivity in Huh7-derived HCV replicon bearing cells with or without core protein expression with that of cells infected with the JFH1 virus strain. JFH1 infection increased hydrogen peroxide production and sensitized cells to oxidant-induced loss of mitochondrial membrane potential and cell death. An identical phenomenon occurred in genome-length replicons-bearing cells but not in cells bearing the subgenomic replicons lacking core protein. Both cell death and mitochondrial depolarization were Ca(2+) dependent and could be prevented by Ca(2+) chelation. The difference in the mitochondrial response of the two replicon systems could be demonstrated even in isolated mitochondria derived from the two cell lines with the 'genome-length' mitochondria displaying greater sensitivity to Ca(2+) -induced cytochrome c release. In vitro incubation of 'subgenomic' mitochondria with core protein increased oxidant sensitivity to a level similar to that of mitochondria derived from cells bearing genome-length replicons. These results indicate that increased mitochondrial ROS production and a reduced threshold for Ca(2+) and ROS-induced permeability transition is a characteristic of HCV infection. This phenomenon is a direct consequence of core protein interactions with mitochondria and is present whenever core is expressed, either in infection, full-length replicon-bearing cells, or in over-expression systems.

New multidisciplinary prostate bone metastases clinic: first of its kind in Canada.

Prostate cancer is the most common non-skin malignancy in men. Almost all men who die from prostate cancer have hormone-refractory prostate cancer with metastasis to bone. Emerging supportive treatments-including chemotherapy, bisphosphonates, and surgery-require integration that is optimized in a multidisciplinary setting. A multidisciplinary clinic for bone metastases has been in place at Toronto-Sunnybrook Regional Cancer Centre since 1999, combining orthopedic surgery, radiation oncology, interventional radiology, and palliative medicine for all patients with bone metastases. The addition of a prostate-focused multidisciplinary clinic integrates these services for patients with advanced prostate cancer.

Cellular response to conditional expression of the hepatitis B virus precore and core proteins in cultured hepatoma (Huh-7) cells.

BACKGROUND: The expression of the hepatitis Be antigen (HBeAg) is one of several strategies used by hepatitis B virus (HBV) to ensure persistence. The HBeAg may function as a toleragen in utero and has been shown to regulate the host's immune response. AIM: The aim of this study was to examine the effect of the HBV precore and core protein on cellular gene expression in the hepatoma cell line Huh-7. STUDY DESIGN: Huh-7 cells with tight regulated expression of the HBV core or precore protein were produced using the Tet-Off tetracycline gene expression system. Changes in cellular gene expression in response to core/precore expression compared to Huh-7 cells not expressing the proteins were determined using a commercial high-density oligonucleotide array (Affymetrix Hu95A GeneChip) containing probes for 12,626 full-length human genes. RESULTS: Analysis of differential mRNA gene expression profiles at 7 days post precore and core expression revealed 45 and 5 genes, respectively, with mRNA changes greater than three-fold. The most striking feature was in Huh-7 cells expressing the precore protein in which 43/45 genes were downregulated 3-11-fold. These included genes that encoded products that regulate transcription/DNA binding proteins, cell surface receptors, cell-cycle/nucleic acid biosynthesis and intracellular signalling and trafficking. The only known gene, which was upregulated encoded a cytoskeletal protein. For the core cell line, 4/5 genes were downregulated 3-15-fold upon core induction and included genes that encoded products that affect intermediary metabolism, cell surface receptors and intracellular signalling. The one gene, which was upregulated was a cytokine gene. CONCLUSION: The results of this study show that HBV precore protein has a much greater effect on cellular gene expression in comparison to the core protein, suggesting that core and precore proteins may have diverse effects on cellular functions and equally different roles in modulating HBV pathogenesis.

A rapid immunochromatographic assay for hepatitis B virus screening.

Simple, rapid and accurate assays for hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) are helpful for clinical diagnosis and field epidemiological surveys. A commercially developed, rapid immunochromatographic test for simultaneous detection of HBsAg and HBeAg was evaluated using a total of 2463 selected samples (827 frozen sera, 1011 fresh sera, and 625 whole blood samples). Results of the rapid test were compared with standard enzyme immunoassay (EIA) methods for HBsAg and HBeAg detection. The accuracy of the rapid test was excellent and was similar for frozen sera, fresh sera and whole blood. The overall sensitivity and specificity for the detection of HBsAg were 95 and 100%, and the corresponding positive and negative predictive values were 100 and 99.7%, respectively. The sensitivity and specificity for the detection of HBeAg were slightly less than that for HBsAg, and were 80 and 98%, with positive and negative predictive values of 91 and 94%, respectively. Thus, compared with the EIA method, the rapid test was highly sensitive and accurate for the detection of HBsAg although somewhat less sensitive and specific for detection of HBeAg. Because of its speed, simplicity and flexibility, the rapid test is ideally suited for HBsAg and HBeAg screening in population-based epidemiological studies and in low risk populations, particularly in regions of the world where hepatitis B is endemic.

Hepatitis C virus core and envelope proteins do not suppress the host's ability to clear a hepatic viral infection.

Several hepatitis C virus (HCV) proteins have been shown in vitro to interact with host cellular components that are involved in immune regulation. However, there is a paucity of data supporting the relevance of these observations to the in vivo situation. To test the hypothesis that such an interaction suppresses immune responses, we studied a line of transgenic C57BL/6 mice that express the HCV core and envelope proteins in the liver. The potential effects of these proteins on the hepatic immune response were evaluated by challenging these mice with a hepatotropic adenovirus. Both transgenic and nontransgenic mice developed similar courses of infection and cleared the virus from the liver by 28 days postinfection. Both groups of mice mounted similar immunoglobulin G (IgG), IgG2a, interleukin-2, and tumor necrosis factor alpha responses against the virus. Additionally, BALB/c mice were able to clear infection with recombinant adenovirus that does or does not express the HCV core and envelope 1 proteins in the same manner. These data suggest that HCV core and envelope proteins do not inhibit the hepatic antiviral mechanisms in these murine experimental systems and thus favor a model in which HCV circumvents host responses through a mechanism that does not involve general suppression of intrahepatic immune responses.

Transportation and retention in outpatient drug abuse treatment programs.

To determine whether certain types of transportation assistance improve outpatient treatment retention beyond thresholds shown to have therapeutic benefits, we analyzed data from 1,144 clients in 22 outpatient methadone maintenance (OMM) programs and 2,031 clients in 22 outpatient drug-free (ODF) programs in the Drug Abuse Treatment Outcomes Study (DATOS), a national, 12-month, longitudinal study of drug abuse treatment programs. Directors' surveys provided information about provision of car, van, or contracted transportation services or individual vouchers/payment for public transportation. Chart-abstracted treatment retention was dichotomized at 365 days for OMM and 90 days for ODF. Separate multivariate hierarchical linear models revealed that provision of car, van, or contracted transportation services improved treatment retention beyond these thresholds for both OMM and ODF, but individual vouchers or payment for public transportation did not. Future research should validate whether car, van, or contracted transportation services improve retention and other treatment outcomes in outpatient drug abuse treatment.

Colorectal cancer screening participation: comparisons with mammography and prostate-specific antigen screening.

OBJECTIVES: The relation of personal characteristics, health and lifestyle behaviors, and cancer screening practices to current colorectal cancer (CRC) screening was assessed and compared with those factors' relation to current mammography screening in women and prostate-specific antigen (PSA) screening in men. METHODS: A cross-sectional random-digit-dialed telephone survey of 954 Massachusetts residents aged 50 and older was conducted. RESULTS: The overall prevalence of current CRC screening was 55.3%. Logistic regression results indicated that family history of CRC (odds ratio [OR] = 1.98; 95% confidence interval [CI] = 1.02, 3.86), receiving a regular medical checkup (OR = 3.07; 95% CI = 2.00, 4.71), current screening by mammography in women and PSA in men (OR = 4.40; 95% CI = 2.94, 6.58), and vitamin supplement use (OR = 1.87; 95% CI = 1.27, 2.77) were significant predictors of CRC screening. CONCLUSIONS: Health and lifestyle behaviors were related to increased current CRC, mammography, and PSA screening. Personal factors independently related to CRC screening were not consistent with those related to mammography and PSA screening. This lack of consistency may reflect different stages of adoption of each type of screening by clinicians and the public.

The influence of downstream protein-coding sequence on internal ribosome entry on hepatitis C virus and other flavivirus RNAs.

Some studies suggest that the hepatitis C virus (HCV) internal ribosome entry site (IRES) requires downstream 5' viral polyprotein-coding sequence for efficient initiation of translation, but the role of this RNA sequence in internal ribosome entry remains unresolved. We confirmed that the inclusion of viral sequence downstream of the AUG initiator codon increased IRES-dependent translation of a reporter RNA encoding secretory alkaline phosphatase, but found that efficient translation of chloramphenicol acetyl transferase (CAT) required no viral sequence downstream of the initiator codon. However, deletion of an adenosine-rich domain near the 5' end of the CAT sequence, or the insertion of a small stable hairpin structure (deltaG = -18 kcal/mol) between the HCV IRES and CAT sequences (hpCAT) substantially reduced IRES-mediated translation. Although translation could be restored to both mutants by the inclusion of 14 nt of the polyprotein-coding sequence downstream of the AUG codon, a mutational analysis of the inserted protein-coding sequence demonstrated no requirement for either a specific nucleotide or amino acid-coding sequence to restore efficient IRES-mediated translation to hpCAT. Similar results were obtained with the structurally and phylogenetically related IRES elements of classical swine fever virus and GB virus B. We conclude that there is no absolute requirement for viral protein-coding sequence with this class of IRES elements, but that there is a requirement for an absence of stable RNA structure immediately downstream of the AUG initiator codon. Stable RNA structure immediately downstream of the initiator codon inhibits internal initiation of translation but, in the case of hpCAT, did not reduce the capacity of the RNA to bind to purified 40S ribosome subunits. Thus, stable RNA structure within the 5' proximal protein-coding sequence does not alter the capacity of the IRES to form initial contacts with the 40S subunit, but appears instead to prevent the formation of subsequent interactions between the 40S subunit and viral RNA in the vicinity of the initiator codon that are essential for efficient internal ribosome entry.

Membrane-associated respiratory syncytial virus F protein expressed from a human rhinovirus type 14 vector is immunogenic.

Human rhinovirus (HRV) replicons have the potential to serve as respiratory vaccine vectors for mucosal immunization in humans. However, since many vaccine immunogens of interest are glycosylated, an important concern is whether HRV replicons are capable of expressing glycosylated proteins. The human respiratory syncytial virus (RSV) fusion (F) protein was chosen as a model glycoprotein and the HRV replicon DeltaP1FVP3 was generated by inserting the F protein-coding sequence in frame and in lieu of the 5' proximal 1489 nucleotides of the capsid-coding segment in the HRV-14 genome. When transfected into H1-HeLa cells, DeltaP1FVP3 replicated and led to the expression of the F protein. Inhibition with guanidine demonstrated that F-protein expression was dependent on DeltaP1FVP3 replication and did not result from translation of input RNA. Although most of the F protein remained as an immature, glycosylated precursor (F0), a readily detectable fraction of the protein was processed into the mature glycosylated subunit F1, an event known to occur within the Golgi apparatus. Packaged DeltaP1FVP3 replicons were generated in transfected HeLa cells by coexpression of homologous HRV capsid proteins using the vaccinia virus/T7 RNA polymerase hybrid system. Packaged replicon RNAs were capable of infecting fresh cells, leading to accumulation of the F protein as in RNA-transfected cells. Mice immunized with HeLa cell lysates containing F protein expressed from DeltaP1FVP3 produced neutralizing antibodies against RSV. These results indicate that an HRV-14 replicon can express a foreign glycosylated protein, providing further support for the potential of HRV replicons as a vaccine delivery system.

Linkage to medical services in the Drug Abuse Treatment Outcome Study.

BACKGROUND: An episode of substance abuse treatment is an opportunity to link substance-abusing patients to medical care at a time when management of medical problems might stabilize recovery and long-term health. However, little is known about the ability of organizational linkage mechanisms to facilitate the delivery of medical care to this population. OBJECTIVES: The goal of this study was to examine whether organizational linkage mechanisms facilitate medical service utilization in drug abuse treatment programs. RESEARCH DESIGN: This was a prospective secondary analysis of the Drug Abuse Treatment Outcome Study, a national longitudinal study of drug abuse treatment programs and their patients from 1991 to 1993. Hierarchical linear models evaluated the effect of on-site delivery, formal and informal referral, case management emphasis, and transportation on the log-transformed number of medical visits at the 1-month in-treatment patient interview. MEASURES: Program directors' surveys provided organizational information, including the linkage mechanism used to deliver medical care. Patients reported the number of medical visits during the first month of drug abuse treatment. RESULTS: Exclusive on-site delivery increased medical utilization during the first month of drug abuse treatment (beta estimate, 0.22; standard error [SE], 0.06; P <0.001). Transportation services also increased 1-month medical utilization (beta estimate, 0.13; SE, 0.03; P <0.001). CONCLUSIONS: Exclusive on-site delivery of medical services increased drug abuse treatment patients' utilization of medical services in the first month of treatment. Transportation assistance warrants strong policy consideration as a facilitator of medical service delivery. Future research should clarify whether program-level linkage to medical services improves the patient-level outcomes of drug abuse treatment.

Self-assembly of nucleocapsid-like particles from recombinant hepatitis C virus core protein.

Little is known about the assembly pathway and structure of hepatitis C virus (HCV) since insufficient quantities of purified virus are available for detailed biophysical and structural studies. Here, we show that bacterially expressed HCV core proteins can efficiently self-assemble in vitro into nucleocapsid-like particles. These particles have a regular, spherical morphology with a modal distribution of diameters of approximately 60 nm. Self-assembly of nucleocapsid-like particles requires structured RNA molecules. The 124 N-terminal residues of the core protein are sufficient for self-assembly into nucleocapsid-like particles. Inclusion of the carboxy-terminal domain of the core protein modifies the core assembly pathway such that the resultant particles have an irregular outline. However, these particles are similar in size and shape to those assembled from the 124 N-terminal residues of the core protein. These results provide novel opportunities to delineate protein-protein and protein-RNA interactions critical for HCV assembly, to study the molecular details of HCV assembly, and for performing high-throughput screening of assembly inhibitors.

The silent consumer: women's reports and ratings of abortion services.

BACKGROUND: Abortion is one of the most common surgical procedures performed on women in the United States, and its safety has been demonstrated. Little research has focused, however, on women's reports and ratings of the service. OBJECTIVES: This study explored the association of demographic factors, medical outcomes, and client ratings of service dimensions with global satisfaction. RESEARCH DESIGN: For this cross-sectional study, permission to access clinic medical records was obtained. Surveys were distributed after the procedure, with instructions to return by mail. SUBJECTS: Study subjects were 797 women who underwent an outpatient surgical abortion at 1 of 2 New England health centers in 1996 and 1997. MEASURES: Demographic data, pregnancy history, and information on the procedure were collected from medical records. Survey items measured reports of access, medical outcomes, and satisfaction ratings with service domains. RESULTS: Women with positive ratings of staff sensitivity and of the counseling process and information received and those who had the procedure at a younger gestational age were less likely to report that care could be better. Although very few women reported a medical complication, this was associated with agreement that care could have been better, as was reporting agreement that the wait between the preexamination visit and the procedure was too long. CONCLUSIONS: Satisfaction with abortion services is high. Education and counseling play very important roles. Survey items could routinely be used to monitor services.

Characterization of recombinant hepatitis A virus genomes containing exogenous sequences at the 2A/2B junction.

Hepatitis A virus (HAV) differs from other members of the family Picornaviridae in that the cleavage of the polyprotein at the 2A/2B junction, commonly considered to be the primary polyprotein cleavage by analogy with other picornaviruses, is mediated by 3C(pro), the only proteinase encoded by the virus. However, it has never been formally demonstrated that the 2A/2B junction is the site of primary cleavage, and the actual function of the 2A sequence, which lacks homology with sequence of other picornaviruses, remains unknown. To determine whether 2A functions in cis as a precursor with the nonstructural proteins, we constructed dicistronic HAV genomes in which a heterologous picornaviral internal ribosome entry site was inserted at the 2A/2B junction. Transfection of permissive FRhK-4 cells with these dicistronic RNAs failed to result in the rescue of infectious virus, indicating a possible cis replication function spanning the 2A/2B junction. However, infectious virus was recovered from recombinant HAV genomes containing exogenous protein-coding sequences inserted in-frame at the 2A/2B junction and flanked by consensus 3C(pro) cleavage sites. The replication of these recombinants was less efficient than that of the parent virus but was variable and not dependent upon the length of the inserted sequence. An HAV recombinant containing a 420-nt insertion encoding the bleomycin resistance protein Zeo was stable for up to five passages in cell culture. Inserted sequences were deleted from replicating viruses, but this did not result from homologous recombination at the flanking 3C(pro) cleavage sites, since the 5' and 3' segments of the inserted sequence were retained in the deletion mutants. These results indicate that the HAV polyprotein can tolerate an insertion at the 2A/2B junction and that the 2A polypeptide does not function in cis as a 2AB precursor. Recombinant HAV genomes containing foreign protein-coding sequences inserted at the 2A/2B junction are novel and potentially useful protein expression vectors.

Hepatitis A virus-specific immunoglobulin A mediates infection of hepatocytes with hepatitis A virus via the asialoglycoprotein receptor.

The mechanisms underlying the hepatotropism of hepatitis A virus (HAV) and the relapsing courses of HAV infections are unknown. In this report, we show for a mouse hepatocyte model that HAV-specific immunoglobulin A (IgA) mediates infection of hepatocytes with HAV via the asialoglycoprotein receptor, which binds and internalizes IgA molecules. Proof of HAV infection was obtained by detection of HAV minus-strand RNA, which is indicative for virus replication, and quantification of infectious virions. We demonstrate that human hepatocytes also ingest HAV-anti-HAV IgA complexes by the same mechanism, resulting in infection of the cells, by using the HepG2 cell line and primary hepatocytes. The relevance of this surrogate receptor mechanism in HAV pathogenesis lies in the fact that HAV, IgA, and antigen-IgA complexes use the same pathway within the organism, leading from the gastrointestinal tract to the liver via blood and back to the gastrointestinal tract via bile fluid. Therefore, HAV-specific IgA antibodies produced by gastrointestinal mucosa-associated lymphoid tissue may serve as carrier and targeting molecules, enabling and supporting HAV infection of IgA receptor-positive hepatocytes and, in the case of relapsing courses, allowing reinfection of the liver in the presence of otherwise neutralizing antibodies, resulting in exacerbation of liver disease.

Core protein-coding sequence, but not core protein, modulates the efficiency of cap-independent translation directed by the internal ribosome entry site of hepatitis C virus.

Among a myriad of putative functions assigned to the hepatitis C virus (HCV) core protein, several studies suggest that it may modulate internal ribosome entry site (IRES)-mediated initiation of translation. We compared the translational activity of dicistronic reporter transcripts containing the HCV IRES within the intercistronic space fused to downstream sequence encoding either 22 amino acids (aa) or 173 aa of the core protein. The inclusion of the nearly full-length core protein-coding sequence significantly suppressed translation in vitro and in transfected HepG2 cells. However, this suppression was not eliminated by frameshift mutations introduced into the core sequence, suggesting that it occurred at the RNA level and not as a result of core protein expression in cis. Similarly, the expression of core protein (aa 1 to 191) in trans from a recombinant baculovirus did not suppress IRES-directed translation from any of these transcripts in transfected Huh-7 cells. While core protein expression did decrease IRES activity in HepG2 cells (up to 79% suppression), the expression of beta-galactosidase from a control baculovirus also suppressed IRES activity (up to 56%), strongly suggesting that this suppression was nonspecific. Finally, the addition of purified recombinant core protein (aa 1 to 179) to in vitro translation reactions at concentrations up to a 10-fold molar excess over the RNA transcripts resulted in no significant reduction in IRES activity. Consistent with these results, a gel retention assay indicated no difference in the affinities of the recombinant HCV core protein and a recombinant Venezuelan equine encephalitis virus capsid protein for HCV IRES-containing RNA transcripts. We conclude that while the inclusion of core protein-coding sequence downstream of the IRES may reduce the efficiency of cap-independent translation on HCV RNA, the core protein itself has no biologically relevant activity in modulating HCV IRES activity.