Multidrug-resistant bacterial infections after liver transplantation: Prevalence, impact, and risk factors.

BACKGROUND & AIMS: Infections by multidrug-resistant bacteria (MDRB) are an increasing healthcare problem worldwide. This study analyzes the incidence, burden, and risk factors associated with MDRB infections after liver transplant(ation) (LT). METHODS: This retrospective, multicenter cohort study included adult patients who underwent LT between January 2017 and January 2020. Risk factors related to pre-LT disease, surgical procedure, and postoperative stay were analyzed. Multivariate logistic regression analysis was performed to identify independent predictors of MDRB infections within the first 90 days after LT. RESULTS: We included 1,045 LT procedures (960 patients) performed at nine centers across Spain. The mean age of our cohort was 56.8 ± 9.3 years; 75.4% (n = 782) were male. Alcohol-related liver disease was the most prevalent underlying etiology (43.2.%, n = 451). Bacterial infections occurred in 432 patients (41.3%) who presented with a total of 679 episodes of infection (respiratory infections, 19.3%; urinary tract infections, 18.5%; bacteremia, 13.2% and cholangitis 11%, among others). MDRB were isolated in 227 LT cases (21.7%) (348 episodes). Enterococcus faecium (22.1%), Escherichia coli (18.4%), and Pseudomonas aeruginosa (15.2%) were the most frequently isolated microorganisms. In multivariate analysis, previous intensive care unit admission (0-3 months before LT), previous MDRB infections (0-3 months before LT), and an increasing number of packed red blood cell units transfused during surgery were identified as independent predictors of MDRB infections. Mortality at 30, 90, 180, and 365 days was significantly higher in patients with MDRB isolates. CONCLUSION: MDRB infections are highly prevalent after LT and have a significant impact on prognosis. Enterococcus faecium is the most frequently isolated multi-resistant microorganism. New pharmacological and surveillance strategies aimed at preventing MDRB infections after LT should be considered for patients with risk factors. IMPACT AND IMPLICATIONS: Multidrug-resistant bacterial infections have a deep impact on morbidity and mortality after liver transplantation. Strategies aimed at improving prophylaxis, early identification, and empirical treatment are paramount. Our study unveiled the prevalence and main risk factors associated with these infections, and demonstrated that gram-positive bacteria, particularly Enterococcus faecium, are frequent in this clinical scenario. These findings provide valuable insights for the development of prophylactic and empirical antibiotic treatment protocols after liver transplantation.

Long-term outcomes (beyond 5 years) of liver transplant recipients-A transatlantic multicenter study.

The long-term (>5 y) outcomes following liver transplantation (LT) have not been extensively reported. The aim was to evaluate outcomes of LT recipients who have survived the first 5 years. A multicenter retrospective analysis of prospectively collected data from 3 high volume LT centers (Dallas-USA, Birmingham-UK, and Barcelona-Spain) was undertaken. All adult patients, who underwent LT since the inception of the program to December 31, 2010, and survived at least 5 years since their LT were included. Patient survival was the primary outcome. A total of 3682 patients who survived at least 5 years following LT (long-term survivors) were included. Overall, median age at LT was 52 years (IQR 44-58); 53.1% were males; and 84.6% were Caucasians. A total of 49.4% (n=1820) died during a follow-up period of 36,828 person-years (mean follow-up 10 y). A total of 80.2% (n=1460) of all deaths were premature deaths. Age-standardized all-cause mortality as compared to general population was 3 times higher for males and 5 times higher for females. On adjusted analysis, besides older recipients and older donors, predictors of long-term mortality were malignancy, cardiovascular disease, and dialysis. Implementation of strategies such as noninvasive cancer screening, minimizing immunosuppression, and intensive primary/secondary cardiovascular prevention could further improve survival.

The role of HBIG in real life for patients undergoing liver transplantation due to HDV-related cirrhosis.

Recommended post-liver transplant (LT) prophylaxis in patients with hepatitis delta includes a nucleos(t)ide analogue (NA) and anti-hepatitis B immunoglobulin (HBIG) indefinitely. We analysed the use of HBIG in real-life clinical practice and its impact on HBV/HDV recurrence in 174 HDV-related LT patients from 10 Spanish liver transplant centres (1988-2018). Median post-LT follow-up was 7.8 (2.3-15.1) years and patient survival at 5 years was 90%. Most patients (97%) received HBIG in the immediate post-LT, but only 42% were on HBIG at the last control. Among those discontinuing HBIG, the median time on treatment was 18 (7-52) months. Post-LT HBsAg+ was detected in 16 (9%) patients and HBV-DNA in 12 (7%). Despite HBsAg positivity, HDV recurrence was reported only in three patients (1.7%), all of whom were not receiving NA and had discontinued HBIG. Our data suggest that a finite HBIG prophylaxis in HDV-LT is feasible, especially if high-barrier NAs are used.

Frailty and sarcopenia in patients with acute-on-chronic liver failure: Assessment and risk in the liver transplant setting.

Frailty and sarcopenia are well-recognized factors related to worse outcomes in patients with cirrhosis, including liver transplant (LT) candidates. Implications of pre-LT functional and muscle deterioration also affect post-LT outcomes. Patients with cirrhosis and acute-on-chronic liver failure (ACLF) have a lower survival rate, both before and after LT. There is a need to better identify those patients with ACLF who would benefit from LT. This review aims to present the available data about frailty and sarcopenia in patients with ACLF in the LT setting. An exhaustive review of the published literature was conducted. Data regarding frailty and sarcopenia in LT candidates with ACLF are scarce and heterogeneous. Studies evaluating frailty and sarcopenia in critically ill patients outside the liver literature are also presented in this review to enrich the knowledge of this field in expansion. Frailty and sarcopenia seem to contribute to worse outcomes in LT candidates with ACLF, both before and after LT. Sarcopenia evaluation may be the most prudent approach for those very sick patients. Skeletal muscle index assessed by computed tomography is recommended to evaluate sarcopenia. The role of muscle ultrasound and bioelectrical impedance analysis is to be determined. Frailty and sarcopenia are crucial factors to consider on a case-by-case basis in LT candidates with ACLF to improve patient outcomes.

First consensus document of waiting list prioritization for liver transplantation by the Spanish Society of Liver Transplantation (SETH).

Spain is worldwide leader in deceased donation rates per million habitants and count on a strong network of twenty-five liver transplant institutions. Although the access to liver transplantation is higher than in other countries, approximately 10% of patients qualifying for liver transplantation in Spain will die in the waiting list or would be excluded due to clinical deterioration. A robust waiting list prioritization system is paramount to grant the sickest patients with the first positions in the waiting list for an earlier access to transplant. In addition, the allocation policy may not create or perpetuate inequities, particularly in a public and universal healthcare system. Hitherto, Spain lacks a unique national allocation system for elective liver transplantation. Most institutions establish their own rules for liver allocation and only two autonomous regions, namely Andalucía and Cataluña, share part of their waiting list within their territory to provide regional priority to patients requiring more urgent transplantation. This heterogeneity is further aggravated by the recently described sex-based disparities for accessing liver transplantation in Spain, and by the expansion of liver transplant indications, mainly for oncological indications, in absence of clear guidance on the optimal prioritization policy. The present document contains the recommendations from the first consensus of waiting list prioritization for liver transplantation issued by the Spanish Society of Liver Transplantation (SETH). The document was supported by all liver transplant institutions in Spain and by the Organización Nacional de Trasplantes (ONT). Its implementation will allow to homogenize practices and to improve equity and outcomes among patients with end-stage liver disease.

What is the optimal antimicrobial prophylaxis to prevent postoperative infectious complications after liver transplantation? A systematic review of the literature and expert panel recommendations.

BACKGROUND: Antimicrobial prophylaxis is well-accepted in the liver transplant (LT) setting. Nevertheless, optimal regimens to prevent bacterial, viral, and fungal infections are not defined. OBJECTIVES: To identify the optimal antimicrobial prophylaxis to prevent post-LT bacterial, fungal, and cytomegalovirus (CMV) infections, to improve short-term outcomes, and to provide international expert panel recommendations. DATA SOURCES: Ovid MEDLINE, Embase, Scopus, Google Scholar, and Cochrane Central. METHODS: Systematic review following PRISMA guidelines and recommendations using the GRADE approach derived from an international expert panel. PROSPERO ID: CRD42021244976. RESULTS: Of 1853 studies screened, 34 were included for this review. Bacterial, CMV, and fungal antimicrobial prophylaxis were evaluated separately. Pneumocystis jiroveccii pneumonia (PJP) antimicrobial prophylaxis was analyzed separately from other fungal infections. Overall, eight randomized controlled trials, 21 comparative studies, and five observational noncomparative studies were included. CONCLUSIONS: Antimicrobial prophylaxis is recommended to prevent bacterial, CMV, and fungal infection to improve outcomes after LT. Universal antibiotic prophylaxis is recommended to prevent postoperative bacterial infections. The choice of antibiotics should be individualized and length of therapy should not exceed 24 hours (Quality of Evidence; Low | Grade of Recommendation; Strong). Both universal prophylaxis and preemptive therapy are strongly recommended for CMV prevention following LT. The choice of one or the other strategy will depend on individual program resources and experiences, as well as donor and recipient serostatus. (Quality of Evidence; Low | Grade of Recommendation; Strong). Antifungal prophylaxis is strongly recommended for LT recipients at high risk of developing invasive fungal infections. The drug of choice remains controversial. (Quality of Evidence; High | Grade of Recommendation; Strong). PJP prophylaxis is strongly recommended. Length of prophylaxis remains controversial. (Quality of Evidence; Very Low | Grade of Recommendation; Strong).

Incidence and risk factors for early readmission after hospitalization for SARS-CoV-2 infection: results from a retrospective cohort study.

PURPOSE: We aim to assess risk factors related to early readmission in previous hospitalized patients with COVID-19. METHODS: We analyzed a retrospective cohort of patients with laboratory-confirmed COVID-19 admitted to Vall d'Hebron University Hospital, Barcelona, Spain. Early readmission was defined as the need for hospitalization within a period of 60 days after discharge. A descriptive analysis of the readmission was performed, including hospitalization outcome. We also performed a multivariate logistic regression to define risk factors for readmission RESULTS: A total of 629 patients were followed up during 60 days with a readmission cumulative incidence of 5.4% (34 out of 629) and an incidence rate of 0.034 person-years. Main reasons for readmission were respiratory worsening (13, 38.2%), decompensation of previous disease (12, 35.3%) or infectious complications (6, 17.6%). Median time to readmission was 12 days (interquartile range 7-33 days). Prior diagnosis of heart failure (OR 4.09; 95% CI 1.35-12.46; p = 0.013), length of stay during index admission greater than 13 days (OR 2.72; 95% CI 1.21-6.12; p = 0.015), treatment with corticosteroids (OR 2.39; 95% CI 1.01-5.70; p = 0.049) and developing pulmonary thromboembolism (OR 11.59; 95% CI 2.89-46.48; p = 0.001) were the risk factors statistically associated with early readmission. CONCLUSION: Readmission cumulative incidence was 5.4%. Those patients with prior diagnosis of heart failure, length of stay greater than 13 days, treated with corticosteroids or who developed pulmonary thromboembolism might benefit from close monitoring after being discharged.

Spontaneous portosystemic shunt embolization in liver transplant recipients with recurrent hepatic encephalopathy.

INTRODUCTION AND OBJECTIVES: Spontaneous portosystemic shunts (SPSS) are a common cause of recurrent hepatic encephalopathy (HE). Shunt occlusion is an effective and safe procedure when performed in patients with cirrhosis and preserved liver function. We aimed to describe our experience with SPSS embolization after liver transplantation (LT). PATIENTS: We identified five patients who underwent SPSS embolization after LT. Clinical, biochemical and technical procedure data were collected. RESULTS: At presentation, all patients had developed graft cirrhosis and HE after LT. Median Model for End-stage Liver Disease (MELD) at embolization was 9 (range 7-12), median Child-Pugh was 8 (range 7-9). Splenorenal and mesocaval shunt were the most frequent types of SPSS found. Three patients have been completely free of HE. Of the two patients who had HE recurrence after embolization, one patient had two episodes of HE which was controlled well with medications. The other patient required three embolizations because of recurrent HE. Median follow-up was 4.4 years (range 1.0-5.0) and MELD score at last follow up was 13 (range 10-18) and median Child-Pugh score B, 7 points (range 5-12). CONCLUSIONS: SPSS can be considered as a cause of HE after LT. SPSS embolization is feasible and safe in LT recipients.

Nonviral liver disease is the leading indication for liver transplant in the United States in persons living with human immunodeficiency virus.

We evaluated whether indications for liver transplantation (LT) have changed among people with/without human immunodeficiency virus (HIV) infection and compared LT outcomes and trends by HIV serostatus. LT recipients (2008-2018) from the United Network for Organ Sharing and Organ Procurement and Transplantation Network (UNOS/OPTN) were identifed. Among 62 195 LT recipients, 352 (0.6%) were HIV-infected. The proportion of HIV-infected patients increased over time (P trend = .001), as did the number of transplant centers performing LT for HIV-infected recipients; average annual percentage change of 9.2% (p < .001). Nonviral causes became the leading indication in 2015 for HIV-uninfected and in 2018 for HIV-infected (P trend < .001). Three-year cumulative patient survival rates were 77.5%, for HIV-infected and 84.6%, for HIV-uninfected (p = .15). Over time, graft and patient survival rates improved for both HIV-infected and uninfected (p < .001). Among HCV-infected LT recipients, 3-year patient survival rates were 72.5% for HIV-infected and 81.8% for HIV-uninfected (p = .02). However, in a subanalysis restricted to 2014-2018, differences in graft and patient survival by HIV serostatus were no longer observed (3-year patient survival rates were 81.2% for HIV-infected and 86.4% for HIV-uninfected, p = .34). In conclusion, in the United States, nonviral liver disease is now the leading indication for LT in HIV-infected patients, and posttransplant outcomes have improved over time.

A notable proportion of liver transplant candidates with alcohol-related cirrhosis can be delisted because of clinical improvement.

BACKGROUND & AIMS: To what extent patients with alcohol-related decompensated cirrhosis can improve until recovery from decompensation remains unclear. We aimed to investigate the probability of recovery and delisting due to improvement in patients with alcohol-related decompensated cirrhosis on the waiting list (WL) for liver transplantation (LT). METHODS: We conducted a registry-based, multicenter, retrospective study including all patients admitted to the LT WL in Catalonia (Spain) with the indication of alcohol-, HCV-, cholestasis- or non-alcoholic steatohepatitis-related decompensated cirrhosis between January 2007 and December 2018. Competing-risk analysis was used to investigate variables associated with delisting due to improvement in patients with alcohol-related decompensated cirrhosis. Criteria for delisting after improvement were not predefined. Outcomes of patients after delisting were also studied. RESULTS: One-thousand and one patients were included, 420 (37%) with alcohol-related decompensated cirrhosis. Thirty-six (8.6%) patients with alcohol-related decompensated cirrhosis were delisted after improvement at a median time of 29 months after WL admission. Lower model for end-stage liver disease (MELD) score, higher platelets and either female sex or lower height were independently associated with delisting due to improvement, while time of abstinence did not reach statistical significance in multivariate analysis (p = 0.055). Five years after delisting, the cumulative probability of remaining free from liver-related death or LT was 76%, similar to patients with HCV-related decompensated cirrhosis delisted after improvement. CONCLUSIONS: A significant proportion of LT candidates with alcohol-related cirrhosis can be delisted due to improvement, which is predicted by low MELD score and higher platelet count at WL admission. Women also have a higher probability of being delisted after improvement, partially due to reduced early access to LT for height discrepancies. Early identification of patients with potential for improvement may avoid unnecessary transplants. LAY SUMMARY: Patients with alcohol-related cirrhosis can improve until being delisted in approximately 9% of cases. Low model for end-stage liver disease score and high platelet levels at admission predict delisting after improvement, and women have higher probabilities of being delisted due to improvement. Long-term outcomes after delisting are generally favorable.

Low seroprevalence of SARS-CoV-2 antibodies in a liver transplant cohort.

Solid organ transplant recipients might be at greater risk for acquisition and mortality because of SARS-CoV-2. There are no data regarding SARS-CoV-2 seroprevalence among liver transplant (LT) recipients, and whether it is different from that of the general population or other immunosuppressed groups. We evaluated the prevalence of IgG SARS-CoV-2 antibodies among LT recipients to estimate the frequency of asymptomatic SARS-CoV-2 infection using serological assays in our outpatient clinic. We conducted a cross-sectional analysis from 10 May to 26 October 2020 of all adult (>18 years) LT recipients that underwent a routine laboratory test for the outpatient clinic follow-up at the Hospital Universitari Vall d'Hebron (Barcelona) in which we included serological testing for SARS-CoV-2. Nine out of 294 LT recipients (3.1%) tested positive for anti-SARS-CoV-2 IgG antibodies. Five of them (55.5%) had suffered clinically symptomatic SARS-CoV-2 infection confirmed by RT-PCR, four (44.4%) had presented compatible symptoms but without microbiological confirmation and only one patient (1/9, 11.1%) tested positive without any previous symptom. SARS-CoV-2 seroprevalence among LT recipients in an area highly affected by the pandemic is lower than in the general population in the same area. These results render the possibility of asymptomatic infection in LT recipients very unlikely.

Outcomes of antiviral treatment in hepatitis C virus liver transplant patients off immunosuppression in the direct acting antivirals era: A case series.

BACKGROUND: Clearance of hepatitis C virus (HCV) under antiviral therapy, including direct-acting antivirals (DAAs), has been associated with higher risk of rejection. Whether patients who are not on immunosuppression (IS) during DAA therapy are at higher risk of rejection is unknown. METHODS: Four transplant recipients who were off IS and treated with DAA therapy were identified. RESULTS: All patients were genotype 1 infection and treated for 12 weeks with sofosbuvir/ledipasvir/ribavirin. At the time of DAA therapy, patients were off IS for a median of 9.5 years. Time from liver transplant (LT) to treatment was 12.9 years. Median baseline ALT was 70 IU/L, at follow-up week 12 was 18 IU/L. No signs of rejection were observed during DAA therapy or follow-up after the end of therapy. All 4 patients obtained sustained virological response. CONCLUSION: Direct-acting antivirals therapy in HCV patients off IS post-LT can be successfully undertaken without the need to restart IS.

Use of a hepatitis C virus (HCV) RNA-positive donor in a treated HCV RNA-negative liver transplant recipient.

The shortage of livers has led most transplant centers to use extended criteria donors. Hepatitis C virus (HCV) RNA-positive donor organs are typically not given to patients who have cleared HCV. A 64-year-old male with chronic hepatitis C, genotype 1b was listed for LT with hepatocellular carcinoma. While on the waiting list, the patient was treated with sofosbuvir, ledipasvir, and ribavirin and achieved an HCV RNA <15 IU/mL by week 10. At week 18 of a planned 24-week treatment course, the patient underwent deceased-donor LT and received an organ from an anti-HCV-positive donor. Treatment was stopped at LT. At week 3 post LT, HCV RNA was detectable and revealed a genotype 3 HCV infection, compatible with transplantation of an organ with established infection. With retreatment with sofosbuvir, daclatasvir, and ribavirin for 12 weeks, the patient achieved a sustained virologic response. This report highlights how antiviral therapies can be used to optimize the outcomes of HCV-infected transplant patients.

Sofosbuvir and daclatasvir in mono- and HIV-coinfected patients with recurrent hepatitis C after liver transplant.

 Background and aims. Pegylated interferon (Peg-INF) and ribavirin (RBV) based therapy is suboptimal and poorly tolerated. We evaluated the safety, tolerability and efficacy of a 24-week course of sofosbuvir plus daclatasvir without ribavirin for the treatment of hepatitis C virus (HCV) recurrence after liver transplantation (LT) in both HCV-monoinfected and human immunodeficiency virus (HIV)-HCV coinfected patients. MATERIAL AND METHODS: We retrospectively evaluated 22 consecutive adult LT recipients (16 monoinfected and 6 coinfected with HIV) who received a 24-week course of sofosbuvir plus daclatasvir treatment under an international compassionate access program. RESULTS: Most patients were male (86%), with a median age of 58 years (r:58-81y). Median time from LT to treatment onset was 70 months (r: 20-116 m). HCV genotype 1b was the most frequent (45%), 55% had not responded to previous treatment with Peg-INF and RBV and 14% to regiments including first generation protease inhibitors. Fifty-six percent of the patients had histologically proven cirrhosis and 6 had ascites at baseline. All patients completed the 24-week treatment course without significant side effects except for one episode of severe bradicardya, with only minor adjustments in immunosuppressive treatment in some cases. Viral suppression was very rapid with undetectable HCV-RNA in all patients at 12 weeks. All 22 patients achieved a sustained virological response 12 weeks after treatment completion. CONCLUSION: The combination of sofosbuvir plus daclatasvir without ribavirin is a safe and effective treatment of HCV recurrence after LT in both monoinfected and HIV-coinfected patients, including those with decompensated cirrhosis.

Key donor factors associated with graft loss among liver transplant recipients with human immunodeficiency virus.

BACKGROUND: Human immunodeficiency virus (HIV)-infected liver transplant (LT) recipients have higher risk of graft loss than HIV-uninfected recipients. As the original donor risk index excluded HIV-positive patients, donor factors associated with graft loss in HIV-positive recipients are unknown. METHODS: Identifying all HIV-positive patients in the Scientific Registry of Transplant Recipients, supplemented by all HIV-infected patients in the solid organ transplantation in HIV: Multi-Site Study (HIV-TR), we evaluated donor factors associated with graft loss among HIV-positive recipients transplanted between March 2002 and August 2012. RESULTS: A total of 249 HIV-positive LT recipients were followed for median 2.4 (interquartile range [IQR]: 0.8-4.9) years. In univariate analysis, donor diabetes (HR=2.09; P=.002) and donor hypertension (HR=1.43; P=.048) were significantly associated with graft loss, and African-American (AA) recipient:non-AA donor race mismatch (HR=1.60; P=.07), other cause of donor death compared to trauma (HR=2.02; P=.09), and donor age 30 years or older (HR=1.53; P=.05) were of borderline significance. In multivariate analysis, donor diabetes (HR=2.12; 95% CI: 1.33-3.38; P=.002) was the only significant predictor of graft loss. CONCLUSION: In HIV-positive LT recipients, risk of graft loss is strongly influenced by donor diabetes. This information may be useful to transplant physicians seeking to optimize overall graft survival in their HIV-positive LT recipients.

Advances in therapy for HIV/hepatitis C virus-coinfected patients in the liver transplant setting.

Complications of cirrhosis due to hepatitis C virus (HCV) are increasing, and liver transplantation (LT) is the most effective treatment for those with liver decompensation or small hepatocellular carcinoma. However, for patients with human immunodeficiency virus (HIV) coinfection, barriers to LT exist. This is related to the poorer survival rates post-LT (55% at 5 years) and, up until this year, the limited options for treating those coinfected LT recipients with progressive recurrent HCV disease, the commonest reason for reduced survival. The newly approved antiviral therapies sofosbuvir and simeprevir, with significantly improved efficacy and markedly better safety and tolerability in HIV and transplant patients, offer the opportunity to transform the outcomes of HIV/HCV-coinfected patients with liver complications. Additional new therapies, anticipated within the year, are expected to further simplify the management of coinfected patients in the transplant setting.

Doubtful Role of IL28B Polymorphism in Occult Hepatitis B Infection.

AIMS: To investigate the influence of IL28B polymorphism in occult hepatitis B infection (OBI) and whether IL28B genetic variants are associated with hepatitis B virus (HBV)-specific T-cell responses. PATIENTS AND METHODS: The rs12979860 IL28B genotype was determined in 34 OBI blood donors, 22 spontaneous HBV resolvers, 36 inactive HBV carriers and 25 seronegative donors. T-cell responses to HBV recombinant proteins were assessed by interferon-γ enzyme-linked immunospot assay. RESULTS: The frequency of the IL28B CC genotype among OBI patients was similar to that of inactive carriers [41 vs. 39%, respectively, p = 0.961; odds ratio (OR) = 1.10; 95% confidence interval (CI) = 0.42-2.86; p = 0.845]. The IL28B CC genotype was found more frequently in spontaneous resolvers, although the differences were not significant (45 vs. 39%, spontaneous resolvers and inactive carriers, respectively; p = 0.828; OR = 1.31; 95% CI = 0.45-3.83; p = 0.622). HBV-specific T-cell responses were detected in OBIs, and significantly stronger T-cell responses towards hepatitis B envelope antigen were observed in those with the IL28B CC genotype. In spontaneous resolvers and inactive carriers, IL28B CC did not correlate with the magnitude of T-cell responses. CONCLUSIONS: In OBI donors, IL28B CC correlates with the intensity of HBV-specific T-cell responses. In this study, IL28B CC is not statistically associated with OBI or with HBV clearance, but a larger number of cases is needed before completely ruling out its role in HBV infection.