Protease inhibitors to treat hepatitis C in the Swiss HIV Cohort Study: high efficacy but low treatment uptake

OBJECTIVES Direct-acting antiviral agents (DAAs) have become the standard of care for the treatment of chronic hepatitis C virus (HCV) infection. We aimed to assess treatment uptake and efficacy in routine clinical settings among HIV/HCV coinfected patients after the introduction of the first generation DAAs. METHODS Data on all Swiss HIV Cohort Study (SHCS) participants starting HCV protease inhibitor (PI) treatment between September 2011 and August 2013 were collected prospectively. The uptake and efficacy of HCV therapy were compared with those in the time period before the availability of PIs. RESULTS Upon approval of PI treatment in Switzerland in September 2011, 516 SHCS participants had chronic HCV genotype 1 infection. Of these, 57 (11%) started HCV treatment during the following 2 years with either telaprevir, faldaprevir or boceprevir. Twenty-seven (47%) patients were treatment-naïve, nine (16%) were patients with relapse and 21 (37%) were partial or null responders. Twenty-nine (57%) had advanced fibrosis and 15 (29%) had cirrhosis. End-of-treatment virological response was 84% in treatment-naïve patients, 88% in patients with relapse and 62% in previous nonresponders. Sustained virological response was 78%, 86% and 40% in treatment-naïve patients, patients with relapse and nonresponders, respectively. Treatment uptake was similar before (3.8 per 100 patient-years) and after (6.1 per 100 patient-years) the introduction of PIs, while treatment efficacy increased considerably after the introduction of PIs. CONCLUSIONS The introduction of PI-based HCV treatment in HIV/HCV-coinfected patients improved virological response rates, while treatment uptake remained low. Therefore, the introduction of PIs into the clinical routine was beneficial at the individual level, but had only a modest effect on the burden of HCV infection at the population level.

Hepatitis B viral load in dried blood spots: A validation study in Zambia

Background: Access to hepatitis B viral load (VL) testing is poor in sub-Saharan Africa (SSA) due toeconomic and logistical reasons.Objectives: To demonstrate the feasibility of testing dried blood spots (DBS) for hepatitis B virus (HBV)VL in a laboratory in Lusaka, Zambia, and to compare HBV VLs between DBS and plasma samples.Study design: Paired plasma and DBS samples from HIV-HBV co-infected Zambian adults were analyzedfor HBV VL using the COBAS AmpliPrep/COBAS TaqMan HBV test (Version 2.0) and for HBV genotypeby direct sequencing. We used Bland-Altman analysis to compare VLs between sample types and bygenotype. Logistic regression analysis was conducted to assess the probability of an undetectable DBSresult by plasma VL.Results: Among 68 participants, median age was 34 years, 61.8% were men, and median plasma HBV VLwas 3.98 log IU/ml (interquartile range, 2.04–5.95). Among sequenced viruses, 28 were genotype A1 and27 were genotype E. Bland–Altman plots suggested strong agreement between DBS and plasma VLs. DBSVLs were on average 1.59 log IU/ml lower than plasma with 95% limits of agreement of −2.40 to −0.83 logIU/ml. At a plasma VL ≥2,000 IU/ml, the probability of an undetectable DBS result was 1.8% (95% CI:0.5–6.6). At plasma VL ≥20,000 IU/ml this probability reduced to 0.2% (95% CI: 0.03–1.7).

Active intravenous drug use during chronic hepatitis C therapy does not reduce sustained virological response rates in adherent patients

Reluctance has been expressed about treating chronic hepatitis C in active intravenous (IV) drug users (IDUs), and this is found in both international guidelines and routine clinical practice. However, the medical literature provides no evidence for an unequivocal treatment deferral of this risk group. We retrospectively analyzed the direct effect of IV drug use on treatment outcome in 500 chronic hepatitis C patients enrolled in the Swiss Hepatitis C Cohort Study. Patients were eligible for the study if they had their serum hepatitis C virus (HCV) RNA tested 6 months after the end of treatment and at least one visit during the antiviral therapy, documenting the drug use status. Five hundred patients fulfilled the inclusion criteria (199 were IDU and 301 controls). A minimum exposure to 80% of the scheduled cumulative dose of antivirals was reached in 66.0% of IDU and 60.5% of controls (P = NS). The overall sustained virological response (SVR) rate was 63.6%. Active IDU reached a SVR of 69.3%, statistically not significantly different from controls (59.8%). A multivariate analysis for treatment success showed no significant negative influence of active IV drug use. In conclusion, our study shows no relevant direct influence of IV drugs on the efficacy of anti-HCV therapy among adherent patients.

Update chronische Hepatitis B und C

Der natürliche Verlauf einer HepatitisB-Virus(HBV)-Infektion ist komplex und wird einerseits durch das Alter zum Zeitpunkt der Infektion, anderseits durch Komorbiditäten bzw. Koinfektionen und zum Teil noch nicht identifizierte Faktoren bestimmt. Das HBV wird nie komplett eliminiert. Das Erreichen des inaktiven Trägerstatus ist aber ein realistisches Therapieziel. Zur Therapie stehen Nukleosid/NukleotidAnaloga sowie pegyliertes Interferonalpha zur Verfügung. Screening von bestimmten Patientengruppen und eine generelle Impfung sind wichtige prophylaktische Massnahmen. Die chronische Hepatitis-C-Virus(HCV) -Infektion führt in circa einem Drittel der Fälle zur Leberzirrhose. Eine Therapie ist generell ab Fibrosestadium Metavir 2 indiziert. Neue DAA (directly acting antivirals) erlauben kurzfristige, hochpotente und nebenwirkungsarme Therapieschemata.

Absence of Hepatitis Delta Infection in a Large Rural HIV Cohort in Tanzania

OBJECTIVES The epidemiological and clinical determinants of hepatitis delta virus (HDV) infection in sub-Saharan Africa are ill-defined. We determined the prevalence of HDV infection in HIV/hepatitis B virus (HBV)-co-infected individuals in rural Tanzania. DESIGN AND METHODS We screened all hepatitis B virus (HBV)-infected adults under active follow-up in the Kilombero and Ulanga Antiretroviral Cohort (KIULARCO) for anti-HDV antibodies. In positive samples, we performed a second serological test and nucleic acid amplification. Demographic and clinical characteristics at initiation of antiretroviral therapy (ART) were compared between anti-HDV-negative and positive patients. RESULTS Among 222 HIV/HBV-coinfected patients on ART, 219 (98.6%) had a stored serum sample available and were included. Median age was 37 years, 55% were female, 46% had WHO stage III/IV HIV disease and median CD4 count was 179 cells/μL. The prevalence of anti-HDV positivity was 5.0% (95% confidence interval 2.8%-8.9%). There was no significant predictor of anti-HDV positivity. HDV could not be amplified in any of the anti-HDV-positive patients and the second serological test was negative in all of them. CONCLUSIONS We found no confirmed case of HDV infection among over 200 HIV/HBV-co-infected patients in Tanzania. As false-positive serology results are common, screening results should be confirmed with a second test.

Hepatitis B Infection, Viral Load and Resistance in HIV-Infected Patients in Mozambique and Zambia.

BACKGROUND Few data on the virological determinants of hepatitis B virus (HBV) infection are available from southern Africa. METHODS We enrolled consecutive HIV-infected adult patients initiating antiretroviral therapy (ART) at two urban clinics in Zambia and four rural clinics in Northern Mozambique between May 2013 and August 2014. HBsAg screening was performed using the Determine® rapid test. Quantitative real-time PCR and HBV sequencing were performed in HBsAg-positive patients. Risk factors for HBV infection were evaluated using Chi-square and Mann-Whitney tests and associations between baseline characteristics and high level HBV replication explored in multivariable logistic regression. RESULTS Seventy-eight of 1,032 participants in Mozambique (7.6%, 95% confidence interval [CI]: 6.1-9.3) and 90 of 797 in Zambia (11.3%, 95% CI: 9.3-13.4) were HBsAg-positive. HBsAg-positive individuals were less likely to be female compared to HBsAg-negative ones (52.3% vs. 66.1%, p<0.001). Among 156 (92.9%) HBsAg-positive patients with an available measurement, median HBV viral load was 13,645 IU/mL (interquartile range: 192-8,617,488 IU/mL) and 77 (49.4%) had high values (>20,000 UI/mL). HBsAg-positive individuals had higher levels of ALT and AST compared to HBsAg-negative ones (both p<0.001). In multivariable analyses, male sex (adjusted odds ratio: 2.59, 95% CI: 1.22-5.53) and CD4 cell count below 200/μl (2.58, 1.20-5.54) were associated with high HBV DNA. HBV genotypes A1 (58.8%) and E (38.2%) were most prevalent. Four patients had probable resistance to lamivudine and/or entecavir. CONCLUSION One half of HBsAg-positive patients demonstrated high HBV viremia, supporting the early initiation of tenofovir-containing ART in HIV/HBV-coinfected adults.

Hepatitis C in HIV-infected individuals: a systematic review and meta-analysis of estimated prevalence in Africa.

INTRODUCTION Although hepatitis C virus (HCV) screening is recommended for all HIV-infected patients initiating antiretroviral therapy, data on epidemiologic characteristics of HCV infection in resource-limited settings are scarce. METHODS We searched PubMed and EMBASE for studies assessing the prevalence of HCV infection among HIV-infected individuals in Africa and extracted data on laboratory methods used. Prevalence estimates from individual studies were combined for each country using random-effects meta-analysis. The importance of study design, population and setting as well as type of test (anti-HCV antibody tests and polymerase chain reactions) was examined with meta-regression. RESULTS Three randomized controlled trials, 28 cohort studies and 121 cross-sectional analyses with 108,180 HIV-infected individuals from 35 countries were included. The majority of data came from outpatient populations (55%), followed by blood donors (15%) and pregnant women (14%). Based on estimates from 159 study populations, anti-HCV positivity prevalence ranged between 3.3% (95% confidence interval (CI) 1.8-4.7) in Southern Africa and 42.3% (95% CI 4.1-80.5) in North Africa. Study design, type of setting and age distribution did not influence this prevalence significantly. The prevalence of replicating HCV infection, estimated from data of 29 cohorts, was 2.0% (95% CI 1.5-2.6). Ten studies from nine countries reported the HCV genotype of 74 samples, 53% were genotype 1, 24% genotype 2, 14% genotype 4 and 9% genotypes 3, 5 or 6. CONCLUSIONS The prevalence of anti-HCV antibodies is high in HIV-infected patients in Africa, but replicating HCV infection is rare and varies widely across countries.

Hepatitis B vaccination of high risk pregnant women: A clinical trial at Parkland Memorial Hospital

Hepatitis B infection is a major public health problem of global proportions. It is estimated that 2 billion people worldwide are infected by the Hepatitis B virus (HBV) at some point, and 350 million are chronic carriers. The Centers for Disease Control and Prevention (CDC) report an incidence in the United States of 140,000–320,000 infections each year (asymptomatic and symptomatic), and estimate 1–1.25 million people are chronically infected. Hepatitis B and its chronic complications (cirrhosis of the liver, liver failure, hepatocellular carcinoma) responsible for 4,000–5,000 deaths in America each year. ^ One quarter of those who become chronic carriers develop progressive liver disease, and chronic HBV infection is thought to be responsible for 60 million cases of cirrhosis worldwide, surpassing alcohol as a cause of liver disease. Since there are few treatment options for the person chronically infected with Hepatitis B, and what is available is expensive, prevention is clearly best strategy for combating this disease. ^ Since the approval of the Hepatitis B vaccine in 1981, national and international vaccination campaigns have been undertaken for the prevention of Hepatitis B. Despite encouraging results, however, studies indicate that prevalence rates of Hepatitis B infection have not been significantly reduced in certain high risk populations because vaccination campaigns targeting those groups do not exist and opportunities for vaccination by individual physicians in clinical settings are often missed. Many of the high-risk individuals who go unvaccinated are women of childbearing age, and a significant proportion of these women become infected with the Hepatitis B virus (HBV) during pregnancy. Though these women are often seen annually or for prenatal care (because of the close spacing of their children and their high rate of fertility), the Hepatitis B vaccine series is seldom recommended by their health care provider. In 1993, ACOG issued a statement recommending Hepatitis B vaccination of pregnant women who were defined as high-risk by diagnosis of a sexually transmitted disease. ^ Hepatitis B vaccine has been extensively studied in the non-pregnant population. The overall efficacy of the vaccine in infants, children and adults is greater than 90%. In the small clinical trials to date, the vaccine seemed to be effective in those pregnant women receiving 3 doses; however, by using the usual 0, 1 and 6 month regimen, most pregnant women were unable to complete a full series during pregnancy. There is data now available supporting the use of an "accelerated" dosing schedule at 0, 1 and 4 months. This has not been evaluated in pregnant women. A clinical trial proving the efficacy of the 0, 1, 4 schedule and its feasibility in this population would add significantly to the body of research in this area, and would have implications for public health policy. Such a trial was undertaken in the Parkland Memorial Hospital Obstetrical Infectious Diseases clinic. In this study, the vaccine was very well tolerated with no major adverse events reported, 90% of fully vaccinated patients achieved immunity, and only Body Mass Index (BMI) was found to be a significant factor affecting efficacy. This thesis will report the results of the trial and compare it to previous trials, and will discuss barriers to implementation, lessons learned and implications for future trials. ^

Hepatitis B and C infections in U.S. incarcerated populations: Prevalence and related mortality

Published reports have consistently indicated high prevalence of serologic markers for hepatitis B (HBV) and hepatitis C (HCV) infection in U.S. incarcerated populations. Quantifying the current and projected burden of HBV and HCV infection and hepatitis-related sequelae in correctional healthcare systems with even modest precision remains elusive, however, because the prevalence and sequelae of HBV and HCV in U.S. incarcerated populations are not well-studied. This dissertation contributes to the assessment of the burden of HBV and HCV infections in U.S. incarcerated populations by addressing some of the deficiencies and gaps in previous research. ^ Objectives of the three dissertation studies were: (1) To investigate selected study-level factors as potential sources of heterogeneity in published HBV seroprevalence estimates in U.S. adult incarcerated populations (1975-2005), using meta-regression techniques; (2) To quantify the potential influence of suboptimal sensitivity of screening tests for antibodies to hepatitis C virus (anti-HCV) on previously reported anti-HCV prevalence estimates in U.S. incarcerated populations (1990-2005), by comparing these estimates to error-adjusted anti-HCV prevalence estimates in these populations; (3) To estimate death rates due to HBV, HCV, chronic liver disease (CLD/cirrhosis), and liver cancer from 1984 through 2003 in male prisoners in custody of the Texas Department of Criminal Justice (TDCJ) and to quantify the proportion of CLD/cirrhosis and liver cancer prisoner deaths attributable to HBV and/or HCV. ^ Results were as follows. Although meta-regression analyses were limited by the small body of literature, mean population age and serum collection year appeared to be sources of heterogeneity, respectively, in prevalence estimates of antibodies to HBV antigen (HBsAg+) and any positive HBV marker. Other population characteristics and study methods could not be ruled out as sources of heterogeneity. Anti-HCV prevalence is likely somewhat higher in male and female U.S. incarcerated populations than previously estimated in studies using anti-HCV screening tests alone without the benefit of repeat or additional testing. Death rates due to HBV, HCV, CLD/cirrhosis, and liver cancer from 1984 through 2003 in TDCJ male prisoners exceeded state and national rates. HCV rates appeared to be increasing and disproportionately affecting Hispanics. HCV was implicated in nearly one-third of liver cancer deaths. ^

Sex, drugs, and STIs: Syphilis infection and hepatitis B vaccine compliance among illicit drug users in Houston

Although the association between syphilis infection status and compliance with the hepatitis B virus vaccine has been the focus of investigation, there is a lack of data regarding the association between syphilis infection and HBV vaccine compliance. The author investigated the association between the exposure of syphilis infection and the outcome of HBV vaccine completion, defined as degree of constancy and accuracy with which a patient follows a prescribed regimen. A cohort design was employed using interview and serological data from the Drugs, AIDS, STDs, Hepatitis (DASH) Research Project; analysis was restricted to HIV and HBV seronegative (at baseline), illicit drug users residing in Harris County. Syphilis negative and syphilis positive infection status was determined from the serological data while covariates and outcome information were determined from the DASH Project Questionnaire; enrolled subjects (n=1160) were selected from the data. Association between exposure and outcome was assessed with logistic regression adjusted for data-based confounders. ^ A prevalence of 7% and 71% was found for syphilis and HBV vaccine compliance, respectively. When measuring the actual association between syphilis infection status and HBV vaccine compliance, an odds ratio of 1.49 (95% CI: 0.86, 2.72) was obtained. There was a non-significant association between these two variables. 78% of the study population was syphilis positive and completed the vaccine series compared to 70% of the population that was syphilis negative and received all three doses. This finding confirms that there is a difference between syphilis positive and negative drug users with respect to HBV vaccine compliance. The fact that differences were found in these drug users with respect to vaccine schedule supports the idea that sub-group differences may exist and thus merits further investigation. If these differences are confirmed, it is recommended that STI interventions identify community characteristics of their samples and target populations based on practices specific to that community. ^

2005 ACIP recommendations effect on newborn hepatitis B vaccination rates and the factors affecting the successful implementation of the recommendations in the US

Background. Hepatitis B virus infection is one of major causes of acute and chronic hepatitis, cirrhosis of the liver, and primary hepatocellular carcinoma. Hepatitis B and its long term consequences are major health problems in the United States. Hepatitis B virus can be vertically transmitted from mother to infant during birth. Hepatitis B vaccination at birth is the most effective measure to prevent the newborn from HBV infection and its consequences, and is part of any robust perinatal hepatitis B prevention program following ACIP recommendations. Universal vaccination of the new born will prevent HBV infection during early childhood and, assuming that children receive the three dosages of the vaccine, it will also prevent adolescent and adult infections. Hepatitis B vaccination is now recommended as part of a comprehensive strategy to eliminate HBV transmission in the United States. ^ Objective. (1)To assess if the hepatitis B vaccination rates of newborn babies have improved after the 2005 ACIP recommendations. (2) To identify factors that affects the implementation of ACIP recommendation for hepatitis B vaccination in newborn babies. These factors will encourage ongoing improvement by identifying successful efforts and pinpointing areas that fall short and need attention. Additional focus areas may be identified to accelerate progress in eliminating perinatal HBV transmission.^ Methods. This review includes information from all pertinent articles, reviews, National immunization survey (NIS) surveys, reports, peer reviewed literature and web sources that were published after 1991.The key words to be used for selecting the articles are: "Perinatal Hepatitis B Prevention program", "Universal Hepatitis B vaccination of newborn babies", "ACIP Recommendations." The data gathered will be supplemented with an analysis of vaccination rates using the National Immunization Survey (NIS) birth dose coverage data.^ Results. The data collected in the NIS of 2009 reveals that the national coverage for birth dose of HepB increased to 60.8% from 50.1% in 2006. The largest increase observed for the birth dose in the past 5 years is from 2008 which increased from 55.3 % to 60.8% in 2009. By state, coverage ranged from 22.8% in Vermont to 80.7% in Michigan. %. Overall, in 2009 the estimated vaccination rates are in higher ranges for most states compared to the estimated vaccination rates in 2006. States vary widely in hepatitis B vaccination rates and in their compliance with the 2005 ACIP recommendation. There are many factors at various stages that might affect the successful implementation of the new ACIP recommendation as revealed in literature review. ^ Conclusions. HBV perinatal transmission can be eliminated, but it requires identifying the gaps and measures taken to increase the current vaccination coverage, ensuring timely administration of post exposure immunoprophylaxis and continued evaluations of the impact of immunization recommendations.^

Prevalence and determinants of hepatitis B co-infection among a United States Veterans Administration cohort with hepatitis C

Background and aim. Hepatitis B virus (HBV) and hepatitis C virus (HCV) co-infection is associated with increased risk of cirrhosis, decompensation, hepatocellular carcinoma, and death. Yet, there is sparse epidemiologic data on co-infection in the United States. Therefore, the aim of this study was to determine the prevalence and determinants of HBV co-infection in a large United States population of HCV patients. ^ Methods. The National Veterans Affairs HCV Clinical Case Registry was used to identify patients tested for HCV during 1997–2005. HCV exposure was defined as two positive HCV tests (antibody, RNA or genotype) or one positive test combined with an ICD-9 code for HCV. HCV infection was defined as only a positive HCV RNA or genotype. HBV exposure was defined as a positive test for hepatitis B core antibodies, hepatitis B surface antigen, HBV DNA, hepatitis Be antigen, or hepatitis Be antibody. HBV infection was defined as only a positive test for hepatitis B surface antigen, HBV DNA, or hepatitis Be antigen within one year before or after the HCV index date. The prevalence of exposure to HBV in patients with HCV exposure and the prevalence of HBV infection in patients with HCV infection were determined. Multivariable logistic regression was used to identify demographic and clinical determinants of co-infection. ^ Results. Among 168,239 patients with HCV exposure, 58,415 patients had HBV exposure for a prevalence of 34.7% (95% CI 34.5–35.0). Among 102,971 patients with HCV infection, 1,431 patients had HBV co-infection for a prevalence of 1.4% (95% CI 1.3–1.5). The independent determinants for an increased risk of HBV co-infection were male sex, positive HIV status, a history of hemophilia, sickle cell anemia or thalassemia, history of blood transfusion, cocaine and other drug use. Age >50 years and Hispanic ethnicity were associated with a decreased risk of HBV co-infection. ^ Conclusions. This is the largest cohort study in the United States on the prevalence of HBV co-infection. Among veterans with HCV, exposure to HBV is common (∼35%), but HBV co-infection is relatively low (1.4%). There is an increased risk of co-infection with younger age, male sex, HIV, and drug use, with decreased risk in Hispanics.^

Immune response to hepatitis B vaccination in drug using populations: A systematic review and meta-regression analysis

Hepatitis B virus (HBV) is a significant cause of liver diseases and related complications worldwide. Both injecting and non-injecting drug users are at increased risk of contracting HBV infection. Scientific evidence suggests that drug users have subnormal response to HBV vaccination and the seroprotection rates are lower than that in the general population; potentially due to vaccine factors, host factors, or both. The purpose of this systematic review is to examine the rates of seroprotection following HBV vaccination in drug using populations and to conduct a meta-analysis to identify the factors associated with varying seroprotection rates. Seroprotection is defined as developing an anti-HBs antibody level of ≥ 10 mIU/ml after receiving the HBV vaccine. Original research articles were searched using online databases and reference lists of shortlisted articles. HBV vaccine intervention studies reporting seroprotection rates in drug users and published in English language during or after 1989 were eligible. Out of 235 citations reviewed, 11 studies were included in this review. The reported seroprotection rates ranged from 54.5 – 97.1%. Combination vaccine (HAV and HBV) (Risk ratio 12.91, 95% CI 2.98-55.86, p = 0.003), measurement of anti-HBs with microparticle immunoassay (Risk ratio 3.46, 95% CI 1.11-10.81, p = 0.035) and anti-HBs antibody measurement at 2 months after the last HBV vaccine dose (RR 4.11, 95% CI 1.55-10.89, p = 0.009) were significantly associated with higher seroprotection rates. Although statistically nonsignificant, the variables mean age>30 years, higher prevalence of anti-HBc antibody and anti-HIV antibody in the sample population, and current drug use (not in drug rehabilitation treatment) were strongly associated with decreased seroprotection rates. Proportion of injecting drug users, vaccine dose and accelerated vaccine schedule were not predictors of heterogeneity across studies. Studies examined in this review were significantly heterogeneous (Q = 180.850, p = 0.000) and factors identified should be considered when comparing immune response across studies. The combination vaccine showed promising results; however, its effectiveness compared to standard HBV vaccine needs to be examined systematically. Immune response in DUs can possibly be improved by the use of bivalent vaccines, booster doses, and improving vaccine completion rates through integrated public programs and incentives.^

Role of B cells in antigen presentation of the hepatitis B core

The hepatitis B virus (HBV) nucleocapsid or core antigen (HBcAg) is extremely immunogenic during infection and after immunization. For example, during many chronic infections, HBcAg is the only antigen capable of eliciting an immune response, and nanogram amounts of HBcAg elicit antibody production in mice. Recent structural analysis has revealed a number of characteristics that may help explain this potent immunogenicity. Our analysis of how the HBcAg is presented to the immune system revealed that the HBcAg binds to specific membrane Ig (mIg) antigen receptors on a high frequency of resting, murine B cells sufficiently to induce B7.1 and B7.2 costimulatory molecules. This enables HBcAg-specific B cells from unprimed mice to take up, process, and present HBcAg to naive Th cells in vivo and to T cell hybridomas in vitro approximately 105 times more efficiently than classical macrophage or dendritic antigen-presenting cells (APC). These results reveal a structure–function relation for the HBcAg, confirm that B cells can function as primary APC, explain the enhanced immunogenicity of HBcAg, and may have relevance for the induction and/or maintenance of chronic HBV infection.

Rescue of a segmented negative-strand RNA virus entirely from cloned complementary DNAs

We provide the first report, to our knowledge, of a helper-independent system for rescuing a segmented, negative-strand RNA genome virus entirely from cloned cDNAs. Plasmids were constructed containing full-length cDNA copies of the three Bunyamwera bunyavirus RNA genome segments flanked by bacteriophage T7 promoter and hepatitis delta virus ribozyme sequences. When cells expressing both bacteriophage T7 RNA polymerase and recombinant Bunyamwera bunyavirus proteins were transfected with these plasmids, full-length antigenome RNAs were transcribed intracellularly, and these in turn were replicated and packaged into infectious bunyavirus particles. The resulting progeny virus contained specific genetic tags characteristic of the parental cDNA clones. Reassortant viruses containing two genome segments of Bunyamwera bunyavirus and one segment of Maguari bunyavirus were also produced following transfection of appropriate plasmids. This accomplishment will allow the full application of recombinant DNA technology to manipulate the bunyavirus genome.