Subscriptions and external links help drive resentful users to alternative and extremist YouTube channels.

Do online platforms facilitate the consumption of potentially harmful content? Using paired behavioral and survey data provided by participants recruited from a representative sample in 2020 (n = 1181), we show that exposure to alternative and extremist channel videos on YouTube is heavily concentrated among a small group of people with high prior levels of gender and racial resentment. These viewers often subscribe to these channels (prompting recommendations to their videos) and follow external links to them. In contrast, nonsubscribers rarely see or follow recommendations to videos from these channels. Our findings suggest that YouTube's algorithms were not sending people down "rabbit holes" during our observation window in 2020, possibly due to changes that the company made to its recommender system in 2019. However, the platform continues to play a key role in facilitating exposure to content from alternative and extremist channels among dedicated audiences.

Like-minded sources on Facebook are prevalent but not polarizing.

Many critics raise concerns about the prevalence of 'echo chambers' on social media and their potential role in increasing political polarization. However, the lack of available data and the challenges of conducting large-scale field experiments have made it difficult to assess the scope of the problem1,2. Here we present data from 2020 for the entire population of active adult Facebook users in the USA showing that content from 'like-minded' sources constitutes the majority of what people see on the platform, although political information and news represent only a small fraction of these exposures. To evaluate a potential response to concerns about the effects of echo chambers, we conducted a multi-wave field experiment on Facebook among 23,377 users for whom we reduced exposure to content from like-minded sources during the 2020 US presidential election by about one-third. We found that the intervention increased their exposure to content from cross-cutting sources and decreased exposure to uncivil language, but had no measurable effects on eight preregistered attitudinal measures such as affective polarization, ideological extremity, candidate evaluations and belief in false claims. These precisely estimated results suggest that although exposure to content from like-minded sources on social media is common, reducing its prevalence during the 2020 US presidential election did not correspondingly reduce polarization in beliefs or attitudes.

Changes in Buprenorphine and Methadone Supplies in the US During the COVID-19 Pandemic.

Importance: The opioid crisis has been exacerbated by the COVID-19 pandemic in the US, with concerns over major disruptions to medication treatment of opioid use disorder. Objective: To investigate whether the COVID-19 pandemic was associated with disruption of buprenorphine and methadone supplies in the US. Design, Setting, and Participants: This repeated cross-sectional study used ARCOS (Automated Reports and Consolidated Ordering System) data, which monitor the flow of controlled substances in the US, from January 1, 2012, through June 30, 2021. Manufacturers and point of sale or distribution at the dispensing or retail level, including hospitals, retail pharmacies, clinicians, midlevel clinicians, and teaching institutions, were included in the analysis. Exposures: COVID-19 pandemic. Main Outcomes and Measures: Quarterly supplies of buprenorphine and methadone per capita in milligrams. Results: The per capita supply of methadone dropped from 13.2 mg in the first quarter of 2020 to 10.5 mg in the second quarter of 2020, whereas the per capita supply of buprenorphine increased from 3.6 mg to 3.7 mg in the same period. The per capita supply of methadone declined 20% (-2.7 mg) in the second quarter of 2020 compared with the first quarter of 2020, and the supply had not returned to 2019 levels as of June 2021, whereas the supply of buprenorphine per person increased consistently during the same period. There were considerable state disparities in the reduction of the methadone supply during the pandemic, with many states experiencing pronounced per capita supply decreases, including reductions as great as 50% in New Hampshire and Florida. These decreases in per capita methadone supply were not compensated by proportional increases in the per capita buprenorphine supply (linear fit, 0.17 [95% CI, -0.43 to 0.76]; P = .47). Conclusions and Relevance: This cross-sectional study of buprenorphine and methadone supplies during the COVID-19 pandemic found a pronounced decline in the methadone supply but no disruption to the buprenorphine supply. Future research is needed to explain the pronounced state disparities in the methadone supply.

Effect of the ExactCare medication care management model on adherence, health care utilization, and costs.

BACKGROUND: Multimorbidity and polypharmacy are common in the United States and are associated with greater risk of disease-related complications and higher health care costs. ExactCare has implemented a high-touch approach that includes home visits, comprehensive ongoing medication reviews, patient education, medication reconciliation, medication compliance packaging, and electronic reminders and trackers. OBJECTIVE: To test whether the ExactCare program improves medication adherence and reduces health care utilization and costs. METHODS: Using a national database from a large U.S. insurer, we identified Medicare Advantage plan members in 8 states from 2007 to 2018 who had both medical and prescription drug coverage. The index year for an ExactCare patient was identified using the date of the first prescription filled by ExactCare, with the previous year being the baseline. All patients without a prescription from an ExactCare pharmacy were considered potential comparison patients. To propensity match ExactCare and comparison patients, the probability of ExactCare participation was modeled using a logistic regression based on demographics, state, year, urban status, Medicaid eligibility, low-income subsidies, comorbidities, and baseline utilization and costs. Multivariate regression analysis was conducted to generate a difference-in-differences estimate of program effect for the matched pairs as well as patient-level fixed effects, while adjusting for additional time-varying characteristics. Adherence outcomes included the proportion of days covered for oral diabetic medications, antihypertensives, and hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins). Utilization outcomes included emergency department (ED) visits, hospitalizations, and skilled nursing facility (SNF) admissions, hospitalization days, and SNF days. Cost outcomes included total cost of care, prescription drug cost, hospital inpatient cost, and SNF cost. RESULTS: ExactCare patients (N = 701) were propensity-matched to comparison patients (N = 1,395) using the nearest 1:2 match approach, with an average follow-up period of 6.6 and 5.4 years for ExactCare and comparison patients, respectively. One year of ExactCare participation was associated with statistically significant increases in adherence to statins (8.4 percentage points; P < 0.001) and antihypertensive drugs (4.9 percentage points; P < 0.001), but the increase in adherence for diabetes drugs was not statistically significant. ExactCare participation was associated with statistically significant decreases in SNF admission rates (-67 SNF stays per 1,000 member-years; P = 0.011), inpatient days (-857 days per 1,000 member-years; P = 0.022), and SNF days (-1,801 days per 1,000 member-years; P = 0.002), but not with the rates of ED visits or hospital admissions. Each year of ExactCare participation was associated with increases in prescription drug costs ($30 per-member per month [PMPM]; P = 0.006) and decreases in total costs (-$196 PMPM; P = 0.023) and medical costs (-$226 PMPM; P = 0.008), largely attributable to decreases in hospital inpatient costs (-$119 PMPM; P = 0.001) and SNF costs (-$30 PMPM; P = 0.007). CONCLUSIONS: ExactCare's medication care management model was associated with improved medication adherence and an approximately $2,400 per member per year reduction in total cost of care, representing a 5% reduction in average costs. DISCLOSURES: This study was funded by ExactCare Pharmacy under a contract with RAND that grants the study authors sole responsibility for data management, study design, data analysis, manuscript drafting, and the decision to publish. The sponsor had no role in the study design and manuscript drafting. All data analysis was conducted by the study authors. A draft manuscript was reviewed by the sponsor, but the study authors made final decisions regarding the content and study conclusions. Shetty, Chen, and Liu are employed by RAND. Rose has nothing to disclose.

Better continuity of care improves the quality of end-of-life care among elderly patients with end-stage renal disease.

Continuity of care (COC) has been emphasized in research on terminal cancer patients to increase the quality of end-of-life care; however, limited research has been conducted on end-stage renal disease patients. We applied a retrospective cohort design on 29,095 elderly patients with end-stage renal disease who died between 2005 and 2013. These patients were identified from the National Health Insurance Research Database of Taiwan. The provider Continuity of Care Index (COCI) and site COCI were calculated on the basis of outpatient visits during the 6-12 months before death. We discovered that increases in the provider COCI were significantly associated with reductions in health expenditures after adjusting for confounders, especially in inpatient and emergency departments, where the treatment intensity is high. Higher provider and site COC were also associated with lower utilization of acute care and invasive treatments in the last month before death. Provider COC had a greater effect on end-of-life care expenditures than site COC did, which indicated significant care coordination gaps within the same facility. Our findings support the recommendation of prioritizing the continuity of end-of-life care, especially provider continuity, for patients with end-stage renal disease.

Nanoparticle Uptake in a Spontaneous and Immunocompetent Woodchuck Liver Cancer Model.

There is a tremendous focus on the application of nanomaterials for the treatment of cancer. Nonprimate models are conventionally used to assess the biomedical utility of nanomaterials. However, these animals often lack an intact immunological background, and the tumors in these animals do not develop spontaneously. We introduce a preclinical woodchuck hepatitis virus-induced liver cancer model as a platform for nanoparticle (NP)-based in vivo experiments. Liver cancer development in these out-bred animals occurs as a result of persistent viral infection, mimicking human hepatitis B virus-induced HCC development. We highlight how this model addresses key gaps associated with other commonly used tumor models. We employed this model to (1) track organ biodistribution of gold NPs after intravenous administration, (2) examine their subcellular localization in the liver, (3) determine clearance kinetics, and (4) characterize the identity of hepatic macrophages that take up NPs using RNA-sequencing (RNA-seq). We found that the liver and spleen were the primary sites of NP accumulation. Subcellular analyses revealed accumulation of NPs in the lysosomes of CD14+ cells. Through RNA-seq, we uncovered that immunosuppressive macrophages within the woodchuck liver are the major cell type that take up injected NPs. The woodchuck-HCC model has the potential to be an invaluable tool to examine NP-based immune modifiers that promote host anti-tumor immunity.

Appropriate Fluoride Toothpaste Application: Improving Caregiver Compliance.

Purpose: Fluoridated toothpaste ingestion is associated with increased dental fluorosis prevalence. Current guidelines recommend a smear of fluoridated toothpaste for children younger than three years old and a pea-sized amount for children age three years or older. The purpose of this study was to evaluate two educational approaches to improve caregiver toothpaste dosing. Methods: Eighty-five caregivers of one- to six-year-olds were surveyed and applied toothpaste to a toothbrush as they normally would for their child. All caregivers then received visual aid (VA) counseling on toothpaste dosing (smear equals 0.09 g, with 0.10 mg fluoride and pea equals 0.22 g with 0.25 mg fluoride). Forty-three caregivers were randomly assigned for teach-back (TB) counseling. Each toothpaste application was weighed. Results: Caregivers (N) equals 56) not familiar with toothpaste guidelines applied more toothpaste at baseline than caregivers familiar with the guidelines (P=0.02). The TB group dispensed toothpaste amounts closer to the ideal compared with the VA group. For all caregivers, VA improved dispensing ability (P=0.008). While TB improved dispensing ability, the difference in average deviation from ideal was not statistically significant (P=0.40) between the TB and VA groups. Conclusions: Teach-back and visual aid counseling methods help caregivers dispense more appropriate toothpaste quantities. Dentists should counsel caregivers of children six years old or younger on fluoride toothpaste dosing and use VA and TB to verify dispensing skills.

Authentic Patient-Derived Hepatitis C Virus Infects and Productively Replicates in Primary CD4+ and CD8+ T Lymphocytes In Vitro.

Accumulated evidence indicates that immune cells can support the replication of hepatitis C virus (HCV) in infected patients and in culture. However, there is a scarcity of data on the degree to which individual immune cell types support HCV propagation and on characteristics of virus assembly. We investigated the ability of authentic, patient-derived HCV to infect in vitro two closely related but functionally distinct immune cell types, CD4+ and CD8+ T lymphocytes, and assessed the properties of the virus produced by these cells. The HCV replication system in intermittently mitogen-stimulated T cells was adapted to infect primary human CD4+ or CD8+ T lymphocytes. HCV replicated in both cell types although at significantly higher levels in CD4+ than in CD8+ T cells. Thus, the HCV RNA replicative (negative) strand was detected in CD4+ and CD8+ cells at estimated mean levels ± standard errors of the means of 6.7 × 102 ± 3.8 × 102 and 1.2 × 102 ± 0.8 × 102 copies/µg RNA, respectively (P < 0.0001). Intracellular HCV NS5a and/or core proteins were identified in 0.9% of CD4+ and in 1.2% of CD8+ T cells. Double staining for NS5a and T cell type-specific markers confirmed that transcriptionally competent virus replicated in both cell types. Furthermore, an HCV-specific protease inhibitor, telaprevir, inhibited infection in both CD4+ and CD8+ cells. The emergence of unique HCV variants and the release of HCV RNA-reactive particles with biophysical properties different from those of virions in plasma inocula suggested that distinct viral particles were assembled, and therefore, they may contribute to the pool of circulating virus in infected patients.IMPORTANCE Although the liver is the main site of HCV replication, infection of the immune system is an intrinsic characteristic of this virus independent of whether infection is symptomatic or clinically silent. Many fundamental aspects of HCV lymphotropism remain uncertain, including the degree to which different immune cells support infection and contribute to virus diversity. We show that authentic, patient-derived HCV productively replicates in vitro in two closely related but functionally distinct types of T lymphocytes, CD4+ and CD8+ cells. The display of viral proteins and unique variants, the production of virions with biophysical properties distinct from those in plasma serving as inocula, and inhibition of replication by an antiviral agent led us to ascertain that both T cell subtypes supported virus propagation. Infection of CD4+ and CD8+ T cells, which are central to adaptive antiviral immune responses, can directly affect HCV clearance, favor virus persistence, and decisively influence the development and progression of hepatitis C.

A systematic review of modifiable risk factors in the progression of multiple sclerosis.

BACKGROUND: The presenting symptoms and rate of progression of multiple sclerosis (MS) are very heterogeneous. The diverse clinical manifestations and the clinical course of the disease may vary with modifiable risk factors. OBJECTIVE: To systematically review modifiable risk factors and exposures associated with MS progression. METHODS: We searched six databases till March 2015, reference-mined reviews, and consulted with experts (PROSPERO 2015:CRD42015016461). Two reviewers screened and extracted data. We used random meta-analysis models and Grading of Recommendations Assessment, Development, and Evaluation (GRADE) to assess the quality of evidence. RESULTS: In total, 59 studies met inclusion criteria. Lower vitamin D levels were associated with higher Expanded Disability Status Scale (EDSS) scores ( r = -0.22; confidence interval (CI) = -0.32, -0.12; 11 studies; I2 = 66%), smokers had an increased risk of MS progression (hazard ratio (HR) = 1.55; CI = 1.10, 2.19; I2 = 72%; seven studies), and there was no association of MS progression with the use of epidural analgesics during childbirth delivery (three studies). There was insufficient evidence to draw conclusions for 11 risk factors due to conflicting results or use of different predictor and outcome measures. CONCLUSION: MS progression was consistently associated with low vitamin D levels, and smoking was associated with a more rapid decline in MS disability. Studies used a variety of methods, predictors, and outcomes making it difficult to draw conclusions. Future studies should focus on prospective assessments.

A systematic review of the effects of modifiable risk factor interventions on the progression of multiple sclerosis.

BACKGROUND: Several risk factors are associated with multiple sclerosis (MS) progression and may be amenable to intervention. OBJECTIVE: To systematically review the evidence for interventions targeting risk factors for MS progression. METHODS: We searched six databases and existing reviews till March 2015 and consulted with experts to identify randomized controlled trials (RCTs) of interventions targeting MS risk factors (PROSPERO 2015:CRD42015016461). RESULTS: In total, 37 RCTs met inclusion criteria. Expanded Disability Status Scale (EDSS) scores after exercise interventions did not differ compared with untreated controls (standardized mean differences (SMDs): 0.02; confidence interval (CI): -0.40, 0.44; I2: 0%; seven RCTs; very low quality of evidence (QoE)). Dietary interventions did not show a statistically significant effect on the relative risk (RR) of progression (RR: 0.86; CI: 0.67, 1.05; I2: 0%; four RCTs; moderate QoE) compared to placebo. EDSS scores after vitamin D supplementation were not significantly different from placebo (SMD: -0.15; CI: -0.33, 0.02; I2: 0%; five RCTs; very low QoE). CONCLUSION: We did not identify any risk factor interventions with significant effects on MS progression, but the overall QoE was limited. More adequately powered trials are needed on vitamin D supplementation, long-term exercise, and smoking cessation.

Human fibroblasts display a differential focal adhesion phenotype relative to chimpanzee.

There are a number of documented differences between humans and our closest relatives in responses to wound healing and in disease susceptibilities, suggesting a differential cellular response to certain environmental factors. In this study, we sought to look at a specific cell type, fibroblasts, to examine differences in cellular adhesion between humans and chimpanzees in visualized cells and in gene expression. We have found significant differences in the number of focal adhesions between primary human and chimpanzee fibroblasts. Additionally, we see that adhesion related gene ontology categories are some of the most differentially expressed between human and chimpanzee in normal fibroblast cells. These results suggest that human and chimpanzee fibroblasts may have somewhat different adhesive properties, which could play a role in differential disease phenotypes and responses to external factors.

Persistence of Hepatitis C Virus Traces after Spontaneous Resolution of Hepatitis C.

Hepatitis C virus (HCV) frequently causes chronic hepatitis, while spontaneous recovery from infection is infrequent. Persistence of HCV after self-limited (spontaneous) resolution of hepatitis C was rarely investigated. The current study aimed to assess incidence and robustness of HCV persistence after self-resolved hepatitis C in individuals with normal liver enzymes and undetectable virus by conventional tests. Applying high sensitivity HCV RNA detection approaches, we analyzed plasma and peripheral blood mononuclear cells (PBMC) from individuals with previous hepatitis C infection. Parallel plasma and PBMC from 24 such non-viraemic individuals followed for 0.3-14.4 (mean 6.4) years were examined. Additional samples from 9 of them were obtained 4.5-7.2 (mean 5.9) years later. RNA was extracted from 250 µl plasma and, if HCV negative, from ~5 ml after ultracentrifugation, and from ex vivo stimulated PBMC. PBMC with evidence of HCV replication from 4 individuals were treated with HCV protease inhibitor, telaprevir. HCV RNA was detected in 14/24 (58.3%) plasma and 11/23 (47.8%) PBMC obtained during the first collection. HCV RNA replicative strand was evident in 7/11 (63.6%) PBMC. Overall, 17/24 (70.8%) individuals carried HCV RNA at mean follow-up of 5.9 years. Samples collected 4.5-7.2 years later revealed HCV in 4/9 (44.4%) plasma and 5/9 (55.5%) PBMC, while 4 (80%) of these 5 PBMC demonstrated virus replicative strand. Overall, 6/9 (66.7%) individuals remained viraemic for up to 20.7 (mean 12.7) years. Telaprevir entirely eliminated HCV replication in the PBMC examined. In conclusion, our results indicate that HCV can persist long after spontaneous resolution of hepatitis C at levels undetectable by current testing. An apparently effective host immune response curtailing hepatitis appears insufficient to completely eliminate the virus. The long-term morbidity of asymptomatic HCV carriage should be examined even in individuals who achieve undetectable HCV by standard testing and their need for treatment should be assessed.

Patient-derived hepatitis C virus inhibits CD4⁺ but not CD8⁺ T lymphocyte proliferation in primary T cells.

BACKGROUND: Hepatitis C virus (HCV) can replicate in cells of the immune system and productively propagate in primary T lymphocytes in vitro. We aimed to determine whether exposure to authentic, patient-derived HCV can modify the proliferation capacity, susceptibility to apoptosis and phenotype of T cells. METHODS: Primary total T cells from a healthy donor were used as targets and plasma-derived HCV from patients with chronic hepatitis C served as inocula. T cell phenotype was determined prior to and at different time points after exposure to HCV. T cell proliferation and apoptosis were measured by flow cytometry-based assays. RESULTS: The HCV inocula that induced the highest intracellular expression of HCV also caused a greatest shift in the T cell phenotype from predominantly CD4-positive to CD8-positive. This shift was associated with inhibition of CD4+ but not CD8+ T cell proliferation and did not coincide with altered apoptotic death of either cell subset. CONCLUSIONS: The data obtained imply that exposure to native HCV can have an impact on the relative frequencies of CD4+ and CD8+ T cells by selectively suppressing CD4(+) T lymphocyte proliferation and this may occur in both the presence and the absence of measurable HCV replication in these cells. If the virus exerts a similar effect in vivo, it may contribute to the impairment of virus-specific T cell response by altering cooperation between immune cell subsets.

Persistence of hepatitis C virus during and after otherwise clinically successful treatment of chronic hepatitis C with standard pegylated interferon α-2b and ribavirin therapy.

Resolution of chronic hepatitis C is considered when serum HCV RNA becomes repeatedly undetectable and liver enzymes normalize. However, long-term persistence of HCV following therapy with pegylated interferon-α/ribavirin (PegIFN/R) was reported when more sensitive assays and testing of serial plasma, lymphoid cells (PBMC) and/or liver biopsies was applied. Our aim was to reassess plasma and PBMCs collected during and after standard PegIFN/R therapy from individuals who became HCV RNA nonreactive by clinical testing. Of particular interest was to determine if HCV genome and its replication remain detectable during ongoing treatment with PegIFN/R when evaluated by more sensitive detection approaches. Plasma acquired before (n = 11), during (n = 25) and up to 12-88 weeks post-treatment (n = 20) from 9 patients and PBMC (n = 23) from 3 of them were reanalyzed for HCV RNA with sensitivity <2 IU/mL. Clone sequencing of the HCV 5'-untranslated region from plasma and PBMCs was done in 2 patients. HCV RNA was detected in 17/25 (68%) plasma and 8/10 (80%) PBMC samples collected from 8 of 9 patients during therapy, although only 5.4% plasma samples were positive by clinical assays. Among post-treatment HCV RNA-negative plasma samples, 9 of 20 (45.3%) were HCV reactive for up to 59 weeks post-treatment. Molecularly evident replication was found in 6/12 (50%) among PBMC reactive for virus RNA positive strand collected during or after treatment. Pre-treatment point mutations persisted in plasma and/or PBMC throughout therapy and follow-up. Therefore, HCV is not completely cleared during ongoing administration of PegIFN/R otherwise capable of ceasing progression of CHC and virus commonly persists at levels not detectable by the current clinical testing. The findings suggest the need for continued evaluation even after patients achieve undetectable HCV RNA post-treatment.

Differential expression of candidate virus receptors in human T lymphocytes prone or resistant to infection with patient-derived hepatitis C virus.

Accumulated evidence implies that hepatitis C virus (HCV) infects not only the liver but also the immune system. A lymphocyte-specific CD5 molecule was recently identified as essential for infection of T cells with native, patient-derived HCV. To assess whether the proposed hepatocyte receptors may also contribute to HCV lymphotropism, expression of scavenger receptor-class B type 1 (SR-B1), claudin-1 (CLDN-1), claudin-6 (CLDN-6), occludin (OCLN), CD5 and CD81 was examined by real-time RT-PCR and the respective proteins quantified by immunoblotting in HCV-prone and resistant T cell lines, peripheral blood mononuclear cells (PBMC), primary T cells and their subsets, and compared to hepatoma Huh7.5 and HepG2 cells. SR-B1 protein was found in T and hepatoma cell lines but not in PBMC or primary T lymphocytes, CLDN-1 in HCV-resistant PM1 T cell line and hepatoma cells only, while CLDN-6 equally in the cells investigated. OCLN protein occurred in HCV-susceptible Molt4 and Jurkat T cells and its traces in primary T cells, but not in PBMC. CD5 was displayed by HCV-prone T cell lines, primary T cells and PBMC, but not by non-susceptible T and hepatoma cell lines, while CD81 in all cell types except HepG2. Knocking-down OCLN in virus-prone T cell line inhibited HCV infection, while de novo infection downregulated OCLN and CD81, and upregulated CD5 without modifying SR-B1 expression. Overall, while no association between SR-B1, CLDN-1 or CLDN-6 and the susceptibility to HCV was found, CD5 and CD81 expression coincided with virus lymphotropism and that of OCLN with permissiveness of T cell lines but unlikely primary T cells. This study narrowed the range of factors potentially utilized by HCV to infect T lymphocytes amongst those uncovered using laboratory HCV and Huh7.5 cells. Together with the demonstrated role for CD5 in HCV lymphotropism, the findings indicate that virus utilizes different molecules to enter hepatocytes and lymphocytes.

Patient-derived hepatitis C virus and JFH-1 clones differ in their ability to infect human hepatoma cells and lymphocytes.

Hepatitis C virus (HCV) is a hepatotropic virus that also infects cells of the immune system. HCV clones cultivated in human hepatoma Huh-7.5 cells have significantly advanced our understanding of HCV replication and candidate hepatocyte receptors. However, naturally occurring patient-derived HCV, in contrast to the HCV JFH-1 clone, is unable to infect Huh-7.5 cells, while it can replicate in human primary T-cells and selected T-cell lines. To better understand this incongruity, we examined the susceptibility of primary T-cells, PBMCs and T-cell lines to infection with patient-derived HCV, the classical HCV JFH-1 and a cell culture-adapted JFH1(T) known to be highly infectious to Huh-7.5 cells. We also tested whether Huh-7.5 cells are prone to virus readily infecting T-lymphocytes. The results revealed that while primary T-cells and Molt4 and Jurkat T-cell lines were susceptible to patient-derived HCV, they were resistant to infection with either JFH1(T) or JFH-1. However, the JFH1(T) clone interacted more firmly, although non-productively, with the cells than JFH-1. Further, Huh-7.5 cells robustly supported replication of JFH1(T) but not patient-derived, wild-type virus, despite using highly sensitive detection assays. In conclusion, JFH-1 and JFH1(T) clones were unable to establish productive infection in human primary T-cells, PBMCs and T-cell lines known to be prone to infection by patient-derived HCV, while Huh-7.5 cells were resistant to infection with naturally occurring virus infecting immune cells. The data showed that the ability to infect lymphocytes is a characteristic of native virus but not laboratory HCV clones.

Hepatitis C virus infection of human T lymphocytes is mediated by CD5.

Hepatitis C virus (HCV) is one of the main causes of chronic liver disease. Although infection of hepatocytes is mainly responsible for manifestations of hepatitis C, the virus also invades the immune system by a yet-to-be-identified mechanism. Using human T cell lines and primary T lymphocytes as targets and patient-derived HCV as inocula, we aimed to identify how HCV gains entry into these cells. HCV replication was determined by detection of the HCV RNA replicative (negative) strand and viral proteins, while specific antibodies, knocking down gene expression and making otherwise-resistant cells prone to HCV, were employed to identify a receptor molecule determining T lymphocyte permissiveness to HCV infection. The results revealed that T cell susceptibility to HCV requires CD5, a lymphocyte-specific glycoprotein belonging to the scavenger receptor cysteine-rich family. Blocking of T cell CD5 with antibody or silencing with specific short hairpin RNA (shRNA) decreased cell susceptibility to HCV, while increasing CD5 expression by mitogen stimulation had the opposite effect. Moreover, transfection of naturally CD5-deficient HEK-293 fibroblasts with CD5 facilitated infection of these otherwise HCV-resistant cells. In contrast to T cells, hepatocytes do not express CD5. The data revealed that CD5 is a molecule important for HCV entry into human T lymphocytes. This finding provides direct insight into the mechanism of HCV lymphotropism and defines a target for potential interventions against HCV propagating in this extrahepatic compartment.