Liver transplantation in HBs antigen (HBsAg) carriers. Prevention of hepatitis B virus (HBV) recurrence by passive immunization

Preclinical animal models to evaluate therapeutic antiviral antibodies

Despite the availability of effective preventative vaccines and potent small-molecule antiviral drugs, effective non-toxic prophylactic and therapeutic measures are still lacking for many viruses. The use of monoclonal and polyclonal antibodies in an antiviral context could fill this gap and provide effective virus-specific medical interventions. In order to develop these therapeutic antibodies, preclinical animal models are of utmost importance. Due to the variability in viral pathogenesis, immunity and overall characteristics, the most representative animal model for human viral infection differs between virus species. Therefore, throughout the years researchers sought to find the ideal preclinical animal model for each virus. The most used animal models in preclinical research include rodents (mice, ferrets, …) and non-human primates (macaques, chimpanzee, ….). Currently, antibodies are tested for antiviral efficacy against a variety of viruses including different hepatitis viruses, human immunodeficiency virus (HIV), influenza viruses, respiratory syncytial virus (RSV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and rabies virus. This review provides an overview of the current knowledge about the preclinical animal models that are used for the evaluation of therapeutic antibodies for the abovementioned viruses.

Entecavir Combined With Short-term Hepatitis B Immunoglobulin in Preventing Hepatitis B Virus Recurrence in Liver Transplant Recipients

BACKGROUND

The combination of nucleoside analogs and long-term hepatitis B immunoglobulin (HBIG) is considered to be the standard regimen for preventing hepatitis B virus (HBV) recurrence after liver transplant (LT). However, long-term use of HBIG causes many adverse effects. The aim of this study was to evaluate the effect of nucleoside analogs entecavir combined with short-term HBIG in preventing HBV recurrence after LT.

METHODS

This retrospective study assessed the effect a combination of entecavir and short-term HBIG in prophylaxis of HBV recurrence among 56 LT recipients who had undergone the procedure because of HBV-associated liver disease at our center between December 2017 and December 2021. All patients received entecavir treatment combined with HBIG for the prevention of hepatitis B recurrence, and HBIG treatment was withdrawn within 1 month. The patients were followed up to determine levels of hepatitis B surface antigen, antibody to hepatitis B surface antigen (HBsAb), and HBV-DNA and the recurrence rate of HBV.

RESULTS

Only 1 patient appeared positive for hepatitis B surface antigen at 2 months post-LT. The overall HBV recurrence rate was 1.8%. The HBsAb titers of all patients gradually decreased over time, with a median of 376.6 IU/L at 1 month post-LT and a median of 13.47 IU/L at 12 months post-LT. During the follow-up period, the HBsAb titer of the preoperative HBV-DNA-positive patients remained at a lower level than that of HBV-DNA-negative patients.

CONCLUSIONS

Entecavir combined with short-term HBIG can exert a good effect for the prevention of HBV reinfection post-LT.

Antiviral prophylaxis against hepatitis B recurrence after liver transplantation: Current concepts

The advance in treatment against hepatitis B virus (HBV) infection with the development of nucleos(t)ide analogues (NAs) with high genetic barrier to resistance, including entecavir and tenofovir, has improved clinical outcomes of patients transplanted for HBV infection, by preventing HBV recurrence after liver transplantation (LT) effectively. Currently, after LT, the combination of hepatitis B immunoglobulin (HBIG) and a high-barrier NA is considered as the standard of care for prophylaxis against HBV recurrence. However, because of the high cost of intravenous high-dose HBIG, other routes of HBIG administration, such as intramuscular or subcutaneous, have come to the foreground. In addition, several transplant centres tend to use a NA as monoprophylaxis, following a short post-LT period of HBIG and NA combination. Lately, studies using HBIG-free prophylactic regimens with entecavir or tenofovir have shown promising outcomes in preventing HBV recurrence, mostly regarding patients with undetectable HBV DNA at the time of LT. Although vaccination against HBV has been an attractive prophylactic approach, its efficacy has been controversial. Moreover, further studies are needed regarding long-term outcomes of complete withdrawal anti-HBV prophylaxis. For patients transplanted for HBV/HDV co-infection, combined regimen should be administered for a longer period post-LT. Finally, the use of grafts from hepatitis B core antibody-positive donors is safe for HBV-negative recipients, with the administration of lifelong antiviral prophylaxis.

Recent Progress on Neutralizing Antibodies against Hepatitis B Virus and its Implications

BACKGROUND

Hepatitis B virus (HBV) infection remains a global health problem. As "cure" for chronic hepatitis B is of current priority, hepatitis B immunoglobulin (HBIG) has been utilized for several decades to provide post-exposure prophylaxis. In recent years, a number of monoclonal antibodies (mAbs) targeting HBV have been developed and demonstrated with high affinity, specificity, and neutralizing potency.

OBJECTIVE

HBV neutralizing antibodies may play a potentially significant role in the search for an HBV cure. In this review, we will summarize the recent progress in developing HBV-neutralizing antibodies, describing their characteristics and potential clinical applications.

RESULTS AND CONCLUSION

HBV neutralizing antibodies could be a promising alternative in the prevention and treatment of HBV infection. More importantly, global collaboration and coordinated approaches are thus needed to facilitate the development of novel therapies for HBV infection.

Antiviral Therapy for AECHB and Severe Hepatitis B (Liver Failure)

This chapter describes the principles of antiviral therapy, treatment strategies, medications and recommendations for AECHB, HBV-ACLF, HBV-related liver cirrhosis, HBV-related HCC, and liver transplantation.

Severe exacerbation of chronic hepatitis B is closely related to continuous HBV replication. Therefore, inhibiting HBV replication to reduce viral load may block disease progression and improve the quality of life of these patients. ETV or TDF has been recommend first-line drug for the treatment of AECHB.

A hyperactive immune response due to continuous HBV replication is the main mechanism for development of severe hepatitis B. In addition to comprehensive treatment, early administration of potent nucleoside analogs can rapidly reduce HBV DNA concentration, relieve immune injury induced by HBV, and reduce liver inflammation and patient mortality. Antiviral agents have become important in the treatment of severe exacerbation of chronic hepatitis B.

Long-term antiviral treatment with nucleoside analogs can delay or reverse the progress of liver cirrhosis. Virologic response, viral resistance and adverse drug reactions should be closely monitored during treatment. The treatment should be optimized for maximum effect based on each patient’s responses.

Effective antiviral therapy can suppress HBV replication and reduce the incidence of HBV-related HCC. Patients with HBV-related HCC should receive individualized and optimal multidisciplinary comprehensive treatment. Anti-viral drugs with high efficacy, low resistance and low adverse drug reactions should be selected to improve the patient’s quality of life and prolong survival time.

Methods to prevent HBV reinfection after liver transplantation include passive immunization (HBIG), antiviral treatment (nucleoside analogs) and active immunization (hepatitis B vaccine).

Clinical trials involving sequential combination therapy with NUC and Peg-IFN have shown statistically significant decline in HBsAg levels on treatment and high rates of sustained post-treatment serologic response. Combination therapy with novel DAA and immunotherapeutic approach may hold promise to overcome both cccDNA persistence and immune escape, representing a critical step towards HBV cure.

Effect of Dosage and Type of Hepatitis B Immunoglobulin on Hepatitis Antibody Levels in Liver Transplant Recipients

BACKGROUND

The current study aimed to evaluate the effect of dosage and type (intramuscular [IM] vs intravenous [IV]) of hepatitis B immunoglobulin (HBIG) on hepatitis antibody level in liver transplant recipients.

METHODS

Between September 2000 and August 2016, patients who underwent orthotropic liver transplantation for chronic liver failure or hepatocellular carcinoma secondary to chronic hepatitis B virus (HBV) were retrospectively reviewed from a prospectively maintained database. The analyses of risk factors for postoperative short- and long-term anti-hepatitis B surface antibody levels (as classified level I: 0 to 100 U; II: 100 to 500 U; III: 500 to 1000 U; IV: >1000 U) were performed based on demographic characteristics, hepatitis B envelope antigen, hepatitis B core antibody, HBV DNA, delta antigen, HBIG administration dosage during unhepatic phase (5000 or 10,000 I/U; IM or IV), and type of administration in post-transplant period. Patients who were followed for less than 12 months were excluded from long-term analysis.

RESULTS

The mean follow-up of 58 orthotropic liver transplant patients was 72 (±45) months. No adverse events were observed during both IM and IV type of administration. Compared with IM type, IV administration was associated with a significantly higher HBV antibody level in the short term (for IM and IV: level I: 24% vs 6%; II: 49% vs 18%; III: 12% vs 35%; IV: 15% vs 41%, respectively, P = .007). In the long term, IV administration of hepatitis B immunoglobulin (HBIG) was reported as the sole factor causing higher antibody level (P = .002). Longer follow-up was associated with decreased levels of anti-hepatitis B surface antibody.

CONCLUSION

IV HBIG administration in preoperative anhepatic phase and postoperative prophylaxis is associated with higher antibody level both the short and long term without any adverse event.

Prophylaxis Among Hepatitis B Core Antibody-positive Deceased-donor Liver Transplant Recipients: Hepatitis B Immunoglobulin Plus Oral Antiviral Agents Versus Antiviral Agents Alone: A Single-center Experience

OBJECTIVES

Hepatitis B core antibody immunoglobulin G seropositivity is evidence of past exposure to hepatitis B virus. Donor or recipient hepatitis B core antibody positivity may pose a risk of reactivation, especially early after liver transplant. Although most centers advocate using antiviral agents plus hepatitis B immunoglobulin, some have recently relied on antivirals only as prophylaxis after liver transplant. Here, we retrospectively investigated patient survival in hepatitis B core antibody-positive recipients, comparing those treated with antivirals plus hepatitis B immunoglobulin versus antivirals alone.

MATERIALS AND METHODS

After Internal Review Board approval, we reviewed medical records of deceased-donor liver transplant recipients between 1995 and 2013. Demographic characteristics, transplant indication, hepatitis B core antibody status, time to death, and type of posttransplant prophylaxis were recorded. We also recorded whether donors showed hepatitis B core antibody positivity. Patients who died within 30 days of liver transplant were excluded.

RESULTS

There were 148 hepatitis B core antibody-positive recipients. Prophylaxis was given to 75 recipients after transplant: 8 (5%) received hepatitis B immunoglobulin, 22 (15%) received antivirals, and 45 (30%) received the combination. There were 34 deaths: 3 (38%) in hepatitis B immunoglobulin only, 3 (14%) in antiviral only, 8 (18%) in the combination, and 20 (27%) in no prophylaxis groups. One- and 5-year survival rates were similar for binary comparisons among prophylaxis groups (P > .05).

CONCLUSIONS

Preliminary results support the current practice of using hepatitis B immunoglobulin plus antivirals for prophylaxis after liver transplant. The similar survival benefit with the combination versus antiviral agents alone suggests equal effectivity for prophylaxis posttransplant. However, a clear benefit of antivirals was not evident in our analysis. Future larger prospective studies are warranted to identify potential benefits of using antivirals alone as prophylaxis after liver transplant and to further clarify their role as the sole prophylactic regimen.

Rational Basis for Optimizing Short and Long-term Hepatitis B Virus Prophylaxis Post Liver Transplantation: Role of Hepatitis B Immune Globulin

Antiviral therapy using newer nucleos(t)ide analogues with lower resistance rates, such as entecavir or tenofovir, suppress hepatitis B virus (HBV) replication, improve liver function in patients with compensated or decompensated cirrhosis, and delay or obviate the need for liver transplantation in some patients. After liver transplantation, the combination of long-term antiviral and low-dose hepatitis B Immune globulin (HBIG) can effectively prevent HBV recurrence in greater than 90% of transplant recipients. Some forms of HBV prophylaxis need to be continued indefinitely after transplantation but, in patients with a low-risk of HBV recurrence (i.e., HBV DNA levels undetectable before transplantation), it is possible to discontinue HBIG and maintain only long-term nucleos(t)ide analogue(s) therapy. A more cautious approach is necessary for those patients with high pretransplant HBV DNA levels, those with limited antiviral options if HBV recurrence occurs (i.e., HIV or hepatitis D virus coinfection, preexisting drug resistance), those with a high risk of hepatocellular carcinoma recurrence, and those at risk of noncompliance with antiviral therapy. In this group, HBIG-free prophylaxis cannot be recommended.

The combination of long-term antiviral and low-dose Hepatitis B Immune globulin (HBIG) can effectively prevent HBV recurrence in > 90% of liver transplant recipients. In patients with low HBV DNA levels, nucleos(t)ide analogue(s) treatment without HBIG is possible.

Antiviral Combination Therapy With Low-Dose Hepatitis B Immunoglobulin for the Prevention of Hepatitis B Virus Recurrence in Liver Transplant Recipients: A Single-Center Experience

OBJECTIVES

This study presents the overall long-term hepatitis B virus (HBV) recurrence rate with possible associated factors after hepatitis B immunoglobulin (HBIG) was given in combination with 4 different antiviral (lamivudine, adefovir, entecavir, and tenofovir) drugs.

PATIENTS AND METHODS

Between September 2000 and October 2013, the medical records of 42 adult patients who underwent liver transplantation at the Cukurova University Medical Hospital for chronic liver failure or hepatocellular carcinoma (HCC) secondary to chronic HBV were reviewed retrospectively. The analyses of risk factors for recurrence were performed based on the efficacy of hepatitis B envelope antigen (HBeAg), hepatitis B core antibody (anti-HBc), HBV DNA, preoperative prophylaxis, and the presence of HCC. Posttransplantation HBV recurrence was defined as persistence of hepatitis B surface antigen (HBsAg) positivity after orthotopic liver transplantation, or the reappearance of HBsAg and HBV DNA after initial HBsAg undetectability despite prophylaxis.

RESULTS

The mean follow-up of 28 patients having HBIG and lamivudine prophylaxis was 73.25 ± 37.5 months with a recurrence rate of 3.5%. The mean follow-up of 2 patients having HBIG and adefovir prophylaxis was 90 ± 46.6 months with a 50% recurrence rate. The mean follow-up of each 6 patients who received prophylaxis with entecavir and tenofovir groups were 27.5 ± 16.1 and 16.17 ± 5.3 respectively, with no posttransplantation recurrence for both groups. On univariate analysis, preoperative factors such as anti-HBc, HBV DNA, preoperative prophylaxis, and the presence of HCC did not show any correlation with recurrence. However, HBeAg showed statistical significance for recurrence.

CONCLUSIONS

Low-dose HBIG in combination with antiviral agents (lamivudine, entecavir, and tenofovir) is efficacious in preventing recurrence of HBV in posttransplantation patients.

Hepatitis viruses and liver transplantation: evolving trends in antiviral management

Viral hepatitis is both a leading indication for liver transplant (LT) and an important cause of posttransplant graft loss and mortality. Treatment and prevention of hepatitis B virus in LT recipients, with the observed corresponding improvement in post-LT outcomes, is among the great success stories in transplantation. By comparison, treatment of hepatitis C virus with safe and effective regimens is only just becoming a reality. Chronic hepatitis E virus infection in LT recipients represents a newly described phenomenon that can also lead to graft loss; early diagnosis and treatment may be key in the management of these patients.

Anti-HBs response to hepatitis B immunoglobulin prophylaxis in liver transplant recipients

BACKGROUND

Hepatitis B virus (HBV) recurrence after a liver transplant (LT) is a global issue. Several strategies have been adopted to prevent this recurrence. Most strategies recommend a combination of hepatitis B immunoglobulin (HBIG) and or nucleos(t)ide analogue.

AIM OF THE STUDY

The aim of the study is to determine the anti-HBs response to HBIG among Indian patients who had undetectable pre-transplant HBV DNA.

METHODS

Seven adult HBV-related LT recipients of Indian origin with low pre-transplant HBV titres who had a liver transplant between August 2009 and June 2012 were included in the study. The protocol followed for post-liver transplant HBIG dose was titrated to achieve an anti-HBs titre of at least 100 IU/L. All recipients were on entecavir. Anti-HBs titre, and HBsAg status was checked at regular intervals. A retrospective analysis of the anti-HBs response to a loading and maintenance dose of HBIG was done.

RESULTS

Seven adult HBV-related LT recipients on post-transplant prophylaxis with HBIG and nucleoside analogue (entecavir) fulfilled the criteria for the study. The median anti-HBs response to the anhepatic and loading dose of HBIG was high at 555 IU/L. In two, the response was less than 100 IU/L. The median dose of HBIG reduced at end of 1 month to 800 IU, and the median titre was 223 IU/L. For the next 11 months, the median requirement of HBIG was 3,000 and 4,000 IU, and the titre was low at 53.8 and 60.9 IU/L at end of 6 and 12 months, respectively.

CONCLUSIONS

The anti-HBs response to HBIG was variable, and titres even below 100 IU/L did not result in HBV recurrence when HBIG was given in combination with entecavir.

Treatment of patients with HBV-related decompensated cirrhosis and liver transplanted patients

Antiviral therapy using newer nucleos(t)ide analogs with lower resistance rates could suppress hepatitis B virus (HBV) replication, improve liver function in patients with compensated or decompensated cirrhosis, delay or obviate liver transplantation in some patients, and reduce the risk of HBV recurrence. Some form of HBV prophylaxis needs to be continued indefinitely posttransplant. However, in patients with a low-risk of HBV recurrence it is possible to discontinue hepatitis B immunoglobulins and maintain long-term nucleos(t)ide analog therapy. Currently, treatment of posttransplantation hepatitis B is a less important clinical problem than it was historically because effective antiviral therapies exist to rescue patients who failed initial prophylaxis.

Prophylaxis of hepatitis B infection in solid organ transplant recipients

Rates of transmission of hepatitis B virus (HBV) infection from organ donors with HBV markers to recipients along with reactivation of HBV during immunosuppression following transplantation have fallen significantly with the advent of hepatitis B immune globulin (HBIg) and effective antiviral therapy. Although the availability of potent antiviral agents and HBIg has highly impacted the survival rate of HBV-infected patients after transplantation, the high cost associated with this practice represents a major financial burden. The availability of potent antivirals with high genetic barrier to resistance and minimal side effects have made it possible to recommend an HBIg-free prophylactic regimen in selected patients with low viral burden prior to transplant. Significant developments over the last two decades in the understanding and treatment of HBV infection necessitate a re-appraisal of the guidelines for prophylaxis of HBV infection in solid organ transplant recipients.

Tenofovir-emtricitabine therapy for the prevention of hepatitis B recurrence in four patients after liver transplantation

In patients infected with chronic hepatitis B virus (HBV) that goes untreated, therapeutic options are limited once the disease decompensates, and orthotopic liver transplantation is often the only treatment available to save the patient's life. After liver transplantation, combined therapy with hepatitis B immune globulin (HBIG) and a nucleos(t)ide analog is the standard of practice for the prevention of HBV recurrence. Historically, nucleos(t)ide analogs such as lamivudine and adefovir have been used with low-dose HBIG for the prevention of HBV recurrence after liver transplantation. However, these analogs are ineffective when used alone due the emergence of resistance mutations. Newer nucleos(t)ide analogs such as tenofovir disoproxil fumarate have demonstrated higher resistance thresholds and effective viral suppression when paired with low-dose HBIG. In this case series, we evaluated the safety and efficacy of switching four patients from low-dose HBIG plus nucleos(t)ide analog therapy for the prevention of HBV recurrence to a combination tenofovir-emtricitabine regimen. At the end of follow-up, all patients remained hepatitis B surface antigen negative and had HBV DNA levels of less than 10 IU/ml. Additionally, no tenofovir-associated nephrotoxicity was observed among the four patients. Tenofovir-emtricitabine monotherapy in lieu of HBIG plus nucleos(t)ide analog therapy demonstrated prevention of HBV recurrence without tenofovir-associated nephrotoxicity after 9 months of follow-up in all four patients and up to 15 months in one patient.

The long-term efficacy of nucleos(t)ide analog plus a year of low-dose HBIG to prevent HBV recurrence post-liver transplantation

Hepatitis B immunoglobulin (HBIG), given in combination with nucleos(t)ide therapy, has reduced the rate of recurrent hepatitis B virus (HBV) following liver transplantation (LT), although the most effective protocol is unknown. We have retrospectively evaluated the use of long-term nucleos(t)ide analog in combination with one yr of low-dose HBIG. One hundred and fifty-two adults with HBV-related liver disease underwent LT in our center from January 1999 to August 2009; of these, 132 patients who received one yr of HBIG combined with long-term nucleos(t)ide analogs (largely on lamivudine [LAM] alone, n = 97) afterward were included for the purposes of this study. Median follow-up post-transplantation was 1752 d. Patient survival was 93.9%, 86.9% and 84.1% at 1, 5, and 10 yr, respectively; none of the 17 deceased patients had recurrent HBV. HBV recurrence was observed in nine patients (all received LAM+HBIG), yielding recurrence rates of 2.3%, 5.1%, and 8.6% at 1, 3, and 5/10 yr, respectively. All recurrences were successfully managed, usually with additional antiviral treatment. In conclusion, this study, with its long-term follow-up, demonstrates that short course of low-dose HBIG (without anti-HBs monitoring) combined with the use of long-term nucleos(t)ide analog is effective and less cumbersome than many protocols in current use.

Which patients respond best to hepatitis B vaccination after a hepatitis B virus-related liver transplantation?

BACKGROUND

A combination of hepatitis B immunoglobulin and nucleos(t)ide analogues is the current standard of care for controlling hepatitis B recurrence after orthotopic liver transplantation (OLT). However, frequent immunoglobulin treatment is expensive and inconvenient. This study investigated the efficacy of hepatitis B virus (HBV) vaccination in preventing the recurrence of hepatitis B after living donor OLT.

METHODS

Twenty-seven patients who had undergone living donor OLT participated in the study; five had acute HBV infected liver failure (ALF-OLT) and 22 had HBV related liver cirrhosis (LC-OLT). Hepatitis B surface antigen (HBsAg)-containing vaccine was administered to them for at least 1 year after transplantation and continued once monthly for up to 36 months post-OLT. Patients who had anti-HBs antibody titers above 100 mIU/mL for a minimum of 6 months without immunoglobulin administration were defined as good responders; the others were defined as poor responders. Interferon-γ enzyme-linked immunospot assays against HBs and HBc antigens were used to assay cellular immune responses.

RESULTS

All five of the ALF-OLT patients had good responses after a median of four (range 2.5-5) vaccinations. Nine of the 22 LC-OLT patients had good responses after a median of 19 (range 11.5-30) vaccinations. Among the LC-OLT group, those with livers donated by relatively higher-aged, marital and high-titer anti-HBs antibody donors were good responders. LC-OLT patients classed as good responders showed interferon-γ responses comparable to those of the ALF-OLT patients.

CONCLUSIONS

The ALF-OLT and LC-OLT patients who received livers from relatively higher-aged, marital, high-titer anti-HBs antibody donors were the best candidates for HBV vaccine administration. Boosting donors before transplantation may facilitate later vaccine response of the recipients.

Serum hepatitis B virus DNA before liver transplantation correlates with HBV reinfection rate even under successful low-dose hepatitis B immunoglobulin prophylaxis

Purpose

The combination of hepatitis B immunoglobulin (HBIg) and nucleos(t)ide analogues has been accepted as the best treatment to control hepatitis B recurrence after orthotopic liver transplantation (OLT). However, the optimal dose of HBIg remains unclear. We have previously reported that high-dose HBIg in the early period followed by low-dose HBIg with nucleos(t)ide analogues offers reliable and cost-effective control of hepatitis B recurrence. The aim of this study was to investigate intrahepatic hepatitis B virus (HBV) reinfection status with our clinically successful protocol.

Methods

We quantified levels of intrahepatic HBV covalently closed circular (ccc) deoxyribonucleic acid (DNA) and serum hepatitis B core-related antigen (HBcrAg), a new serological marker that can estimate intrahepatic cccDNA levels. Nucleos(t)ide analogues were administered in all cases.

Results

No patients showed recurrence of hepatitis B surface antigen (HBsAg) or HBV-DNA. However, HBV, cccDNA, and HBcrAg were positive in 57% and 48% of patients after OLT, respectively. Pre-OLT serum HBV-DNA and HBcrAg levels correlated linearly with post-OLT cccDNA levels (r = 0.534, P < 0.05, and r = 0.634, P < 0.05, respectively). High serum HBV-DNA and HBcrAg levels, particularly with >3 log₁₀ copies/mL and >4 log₁₀ IU/mL, respectively, at the time of OLT, were associated with high levels of post-OLT cccDNA. Even with our successful protocol, nearly half of patients showed HBV reinfection.

Conclusions

Patients with high serum HBV-DNA and HBcrAg levels before OLT (particularly >3 log₁₀ copies/mL and >4 log₁₀ IU/mL, respectively) should be followed with care for HBV recurrence.

Hyperimmune products in the prevention and therapy of infectious disease: a report of a hyperimmune products expert advisory panel

This paper reviews a meeting at which basic pathophysiology of infections, mechanisms of action of hyperimmune products and pharmacokinetic and pharmacodynamic parameters, as well as currently available hyperimmunes and their potential new targets and uses, were discussed. A hyperimmune product was defined as either a monoclonal antibody or a polyclonal preparation enriched with antibody directed against one or more particular targets. A number of issues were emphasised, including: resistant bacterial pathogens, such as Staphylococcus aureus and Streptococcus pyogenes; the role of hyperimmune intravenous globulins in the prevention of sepsis in low birthweight infants; hepatitis B virus infection associated with liver transplantation; combination therapy; the potential role of hyperimmunes in the prevention and treatment of hepatitis C virus; and the use of immunoglobulins for the prophylaxis of Epstein-Barr virus-related lymphoproliferative disease. Routes of administration were also discussed. It was concluded that the development of hyperimmunes faces numerous obstacles. It was agreed that the use of hyperimmunes in clinical trials must be standardised; clinical trials must be large enough to have sufficient power to demonstrate efficacy with clear-cut end-points, and means need to be developed, in conjunction with regulatory agencies, for the feasible evaluation of combination products. However, progress in all these aspects will provide a wide range of hyperimmunes for future use.

Hepatitis B immunoglobulin in preventing reinfection following liver transplantation

Before the availability of hepatitis B immunoglobulin (HBIG) in hepatitis B-positive transplant recipients, the acute mortality was very high, in many centers up to 50% within 60 days post-transplant. The overall reinfection rate was approximately 60% within the initial 6 months, increasing to 80-90% within the initial 12 months and, in many cases, leading to allograft loss and death or retransplantation. These recurrent infections were often more severe and more rapidly progressing than the initial infection, probably due to high-dose immunosuppressive regimens. The poor prognosis before introduction of HBIG made hepatitis B liver disease an absolute contraindication for liver transplantation, leaving these patients with very limited treatment options. This changed in the late 1980s with the introduction of HBIG, which reduced the incidence of hepatitis B in the transplanted liver to approximately 15-50%, with concomitant improvement in graft and overall survival. The prognosis was further improved by a combination of long-term HBIG and antiviral therapy, in particular lamivudine, which reduced the reinfection rate, in most cases to between 0 and 5%. Owing to the cost and relative inconvenience of HBIG, some transplant centers have experimented with early discontinuation of HBIG and replacement with antiviral monotherapy. A number of studies, however, have found significantly higher recurrence rates associated with lamivudine monotherapy (40-50%) compared with combination therapy and, hence, lamivudine monotherapy is not recommended.

A novel approach of prophylaxis to HBV recurrence after liver transplantation

Liver transplantation (LT) in patients with hepatitis B virus (HBV) infection is associated with a high rate of graft loss and poor survival, unless re-infection can be prevented. Human hepatitis B immune globulin (HBIG) and nucleoside analogues (NA) have long been utilized to prevent re-infection. Previously, we generated a human monoclonal antibody (mAb), HB that recognizes the surface antigen of hepatitis B virus (HBV). We have constructed a secreted version of HB and cloned its genes into recombinant adeno-associated virus (AAV). We compared the efficiency of AAV vector after a single injection via intramuscular or intravenous routes without additional intervention. Then, we evaluated the activity of antibody HB in tree shrews treated with rAAV-HB and in vitro experiments. So, intramuscular injection of rAAV-HB was a suitable method for the immunoprophylaxis of HBV infection. This human antibody will be useful for the immunoprophylaxis of HBV infection.

Liver transplantation for hepatitis B: what is the best hepatitis B immune globulin/antiviral regimen?

1. Prophylaxis using the combination of lamivudine and high-dose intravenous hepatitis B immunoglobulin (approximately 10,000 IU monthly) reduces the long-term risk of recurrence of hepatitis B in hepatitis B surface antigen-positive transplant recipients to 5% to 10%. However, this therapy is expensive and inconvenient for patients. 2. Recent studies have shown that similar results can be obtained, at far less cost, with much lower doses of intramuscular hepatitis B immune globulin (400-800 IU monthly) in combination with pretransplant and posttransplant lamivudine therapy. 3. The development of lamivudine resistance pre-transplant can lead to hepatic decompensation and increases the risk of posttransplant recurrence in patients receiving hepatitis B immune globulin/lamivudine prophylaxis. Newer nucleos(t)ide analogues with lower resistance rates such as entecavir, adefovir, and tenofovir should therefore replace lamivudine in hepatitis B prophylaxis. 4. Combination therapy with these newer agents and low-dose intramuscular hepatitis B immune globulin is likely to be the most cost effective hepatitis B immune globulin-containing regimen for the prevention of hepatitis B recurrence post-transplant. 5. Some form of hepatitis B virus prophylaxis needs be continued indefinitely post-transplant. However, the use of antivirals with very low rates of drug resistance will make it possible to stop hepatitis B immune globulin therapy in many patients currently receiving hepatitis B immune globulin/nucleos(t)ide combination therapy.

Antibody to hepatitis B surface antigen trough levels and half-lives do not differ after intravenous and intramuscular hepatitis B immunoglobulin administration after liver transplantation

Hepatitis B immunoglobulin (HBIG) administration remains an essential component of standard reinfection prophylaxis after liver transplantation for hepatitis B virus-related liver disease. Previous studies have suggested that intramuscular (IM) HBIG administration compared to intravenous (IV) HBIG administration may be cost-effective and dose-saving. To compare antibody against hepatitis B surface antigen (anti-HBs) kinetics after IV HBIG administration versus IM HBIG administration, 24 patients received 2000 IU of HBIG every 6 weeks over a study period of 48 weeks in a crossover design. HBIG was started intravenously in 12 patients (group A) and intramuscularly in 12 patients (group B). After 4 doses, at week 24 HBIG administration was switched from IM to IV and vice versa. Anti-HBs kinetics of 22 patients were evaluated. Mean anti-HBs levels measured 2, 4, and 6 weeks after each HBIG administration did not differ significantly (480 +/- 166, 319 +/- 126, and 221 +/- 106 IU/L after IV administration versus 457 +/- 166, 310 +/- 147, and 218 +/- 112 IU/L after IM administration). Half-lives of anti-HBs decline (IV, 25.5 +/- 6.0 days, versus IM, 24.7 +/- 6.2 days) and area under the curve values from week 2 to 6 (IV, 9.4 +/- 3.6 IU*day/mL, versus IM, 9.0 +/- 3.9 IU*day/mL) also showed no significant difference. Variation of anti-HBs levels after IV HBIG administration versus IM HBIG administration was neither significantly different within patients (intraindividual variance) nor between patients (interindividual variance). However, intraindividual variance was lower than interindividual variance after IV (P < 0.05) and IM (P < 0.05) HBIG administration at every time point (2, 4, and 6 weeks). In conclusion, IV HBIG administration and IM HBIG administration are equally effective with respect to the crucial pharmacokinetic parameters. That is, IM HBIG is not dose-saving; however, it may be cost-effective if the price per unit is lower. Individualized dosing intervals should be further evaluated as a cost-effective alternative to fixed dosing schemes.

Prophylaxsis against recurrance of hepatitis B virus after liver transplantation: a retrospective analysis spanning 20 years

Liver transplantation (LT) in patients with hepatitis B virus (HBV) infection is associated with a high rate of graft loss and poor survival, unless re-infection can be prevented. Human hepatitis B immune globulin (HBIG) has long been utilized to prevent re-infection. More recently, an anti-viral agent has been utilized along with HBIG. However, the regimens utilized have varied considerably among LT programmes and the optimal regimen has never been defined. We conducted a retrospective analysis of 41 patients who underwent LT for HBV at our centre since 1985 and received either HBIG with or without an anti-viral agent. The mean age of these patients was 46 years; 81% were male and 88% white. The mean and maximal follow-up were 5.9 and 15 years respectively. Eight out of 15 E-antigen-positive patients who received HBIG alone developed recurrence after a mean of 17 months. In contrast, none of 10 E-Ag-negative patients who received HBIG alone and none of the 10 E-antigen-positive patients who received both HBIG and either lamivudine or adefovir developed recurrence. As long as the anti-HB surface remained detectable, no absolute minimum serum level appeared to lead to recurrent HBV. We concluded that recurrence of HBV following LT can be prevented in E-antigen-positive patients with a combination of HBIG and an anti-viral agent. In contrast, recurrence can be prevented in E-antigen-negative patients with HBIG alone. Maintaining a serum anti-HB surface level above a minimum arbitrary titre of 200 pg/mL did not appear to be necessary for effective HBIG prophylaxis.

Combination therapy in liver transplant recipients with hepatitis B virus without hepatitis B immune globulin

INTRODUCTION

Conventional therapy to prevent HBV recurrence in liver transplant (LTx) recipients consists of Hepatitis B Immune Globulin (HBIg). The aim of this review is to investigate the safety and efficacy of converting HBIg and LAM therapy to ADV and LAM therapy.

METHODS

A retrospective review involving all liver transplant patients with HBV maintained on HBIg and LAM therapy. Results collected included: gender, age, HBV serological and DNA status (COBAS AmpliScreen PCR-based testing). Serologic testing was done every three months. Patients were followed for drug reactions, therapy compliance, and immune suppression compliance. A cost benefit analysis was done for drug comparisons using United States currency values.

RESULTS

Patient demographics included: Male (n=6), Female (n=4), mean age 44 years (range 33 to 65). The mean length of follow up since therapy conversion (from HBIg and LMV to ADV and LMV) was 21 months (range 16 to 25 months). Serological status at time of conversion revealed that DNA status remained negative in all patients, HBsAg negative in 10/10, HB eAg (+) (5/10) and HBeAb (+)(5/10). None of the patients experienced an increase in transaminases while on dual ADV and LAM therapy. All patients were maintained on immune suppression monotherapy (tacrolimus) at 7-9 ng/mL. All patients reported compliance with the dual therapy and that they experienced no drug related side effects. Mean yearly costs for ADV and LAM was 7,235.00 United States dollars (range 6,550.00 to 8,225.00); while mean monthly costs for HBIg and LAM; 9225.00 (range 7205.00 to 12005.00).

CONCLUSION

The above results demonstrate beneficial effects of ADV and LAM in place of the current standard of HBIg and LAM therapy. Safety and short term results show nucleoside therapy is adequate at preventing HBV viral recurrence. Lastly, the economic benefit for ADV and LAM vastly outweighed the HBIg and LAM group.

Prevention of hepatitis B virus recurrence after liver transplantation

Liver transplantation for hepatitis B virus (HBV)-related liver disease has changed from a contraindication to outcomes comparable with non-HBV-related liver transplantations during the last two decades. Mainly the implementation of immunoprophylaxis with hepatitis B immunoglobulin (HBIG) and the use of nucleoside analogs such as lamivudine and adefovir account for this dramatic change. The standard of care in most centers today consists of lamivudine treatment in replicating hepatitis B pre-orthotopic liver transplantation (OLT) and a combination regimen of lamivudine and HBIG post-OLT. With adefovir, a potent antiviral drug became available in recent years that allows for the treatment of patients with lamivudine-resistant tyrosine-methionine-aspartate-aspartate (YMDD)-mutant HBV. In the transplantation setting, first studies indicate that a triple prophylactic therapy consisting of lamivudine, adefovir, and HBIG will become the standard of care for YMDD-mutant-related hepatitis B. With new drugs emerging for the treatment of chronic HBV, there is optimism for new options also in the transplant setting.

[The prophylaxis against post-liver-transplant hepatitis B re-infection]

OBJECTIVE

To review the prophylaxis against post-liver transplantation hepatitis B reinfection with anti-hepatitis B immunoglobulin and nucleoside analogues.

METHOD

A bibliographic search was carried out using Pubmed, entering the following key words: hepatitis B and liver transplantation and (hepatitis B hyperimmune globulin and lamivudine and adefovir dipivoxil) up to June 2006. The initial search was filtered using the terms clinical trial, randomized clinical trial and review. The data contained in selected studies were reviewed.

RESULTS

A total of 53 works were found. Prophylaxis with anti-HB immunoglobulin and lamivudine is the best strategy for avoiding recurrence of the hepatitis B virus in patients undergoing hepatic transplants; achieving very low reinfection rates (0-10%) with follow up periods of between 1-5 years. There is a great degree of variability (dose, duration and method of HBIg administration) in the prophylactic protocols reviewed. The use of low doses of anti-HB immunoglobulin (administered intravenously followed by intramuscular administration, or administered intramuscularly from the anhepatic stage), and lamivudine in patients who receive transplants with a low risk of recurrence, shows prophylactic efficacy comparable to the use of high doses of anti-HB immunoglobulin. Furthermore, it implies a considerable reduction in costs.

CONCLUSIONS

The availability of suitably designed clinical trials is required to design a more cost-effective protocol and reduce variability.

Short-term high-dose followed by long-term low-dose hepatitis B immunoglobulin and lamivudine therapy prevented recurrent hepatitis B after liver transplantation

Hepatitis B immunoglobulin (HBIg) and lamivudine combination has been accepted as the best way to control hepatitis B recurrence after liver transplantation. However, the optimal dose of HBIg and the target titer of hepatitis B surface antibody (HBsAb) remain unclear. We report our satisfactory experience with high-dose HBIg in the early period followed by low-dose HBIg with lamivudine. Subjects comprised five patients with fulminant hepatitis (FH) and 18 patients with liver cirrhosis (LC) who underwent liver transplantation. HBIg at a dosage of 200 IU/kg per day was administered for one week postoperatively. Thereafter, HBIg was administered only for HBsAb titer <100 IU/L. After six months, HBIg was withdrawn in FH and administered in LC only for HBsAb titer <10 IU/L. Lamivudine was administered to two FH and all LC cases. Although two patients with LC showed transient hepatitis B surface antigen (HBsAg) recurrence, all patients remained HBsAg-negative at the final follow-up date. This method allows reliable and cost-effective control of hepatitis B recurrence.

Failure of hepatitis B vaccination with conventional HBsAg vaccine in patients with continuous HBIG prophylaxis after liver transplantation

Hepatitis B vaccination after liver transplantation for hepatitis B-related liver disease has been investigated as an alternative strategy to reinfection prophylaxis with hepatitis B immunoglobulin (HBIG) with conflicting results. In most studies, HBIG treatment was discontinued before vaccination. An outstanding good response was achieved with vaccination under continuous HBIG administration using hepatitis B surface antigen (HBsAg)-based vaccine containing special adjuvants. Both, adjuvants and continuous HBIG administration have been discussed as crucial factors for good response. Twenty-four patients were vaccinated with conventional double dose recombinant vaccine containing 40 microg HBsAg up to 12 times at weeks 0, 2, 4 (cycle 1), 12, 14, 16 (cycle 2), 24, 26, 28 (cycle 3), and 36, 38, 40 (cycle 4). All patients received 2,000 IU HBIG every 6 weeks (4 times intravenously and 4 times intramuscularly). A significant response was defined as reconfirmed increase of anti-HBs-antigen (anti-HBs) unexplained by HBIG administration or lack of anti-HBs decrease below 100 IU/L after discontinuation of HBIG treatment after week 48. Only 2 of 24 patients (8.3%) responded significantly. Anti-HBs started to increase after the seventh vaccination (cycle 3, during intramuscular HBIG administration) in 1 patient and after 12th vaccination (cycle 4, during intravenous HBIG administration) in the other. Maximum anti-HBs levels were >1,000 IU/L in both patients and decreased significantly slower as compared to passive prophylaxis during follow-up. In conclusion, the conventional HBsAg vaccine failed to induce a significant humoral immune response in most patients despite continued HBIG treatment. Further studies should address the question, of whether the use of potent adjuvant systems results in higher response rates.

Hepatitis C immune globulin (human) for the prevention of viral recurrence after liver transplantation

Immunoglobulin therapy has been used extensively in the treatment of infectious diseases. Hepatitis B immunoglobulin (HBIg) reduces the onset of infection in post-percutaneous exposure to Hepatitis B virus (HBV) and in infants of hepatitis B surface antigen (HBsAg)-positive mothers; it also significantly reduces the risk of recurrent HBV infection in liver transplant recipients, thus increasing the survival rate of this population. Prior to 1990, when plasma donors were not screened for the hepatitis C virus (HCV) antibody, the prevalence of HCV viremia after a liver transplant was found to be lower in those patients receiving HBIg containing anti-HCV antibodies. Phase I trials with chimpanzees demonstrated the ability of hepatitis C immune globulin (human) to decrease hepatic inflammation and to neutralize the HCV antibody, but this effect was not sustained over time. Phase I/II human studies have currently been unable to replicate the animal studies, but further trials are planned.

Prevention of de novo HBV infection by the presence of anti-HBs in transplanted patients receiving core antibody-positive livers

AIM: To analyze whether the presence of anti-HBs in liver transplant recipients is effective in preventing HBV infection.

METHODS: Twenty-three patients receiving anti-HBc positive liver were studied. Nine recipients were anti-HBc positive as a result of previous HBV infection. Of them, one also received HBV vaccine during the pre-liver transplantation period. Fourteen recipients were anti-HBs positive due to HBV vaccine administered during the pre-transplant period. Liver biopsy was obtained in 10/14 anti-HBc negative/anti-HBs positive recipients and in 4/9 anti-HBc positive recipients.

RESULTS: After a mean follow-up period of 46 months, 1 recipient with protective serum anti-HBs levels developed de novo HBV infection as a consequence of immune escape HBV mutants. Among the 14 vaccinated anti-HBc negative/anti-HBs positive recipients, 1/10 patients with available liver biopsy (10%) had liver HBV-DNA at 13 mo post-liver transplantation without serum viral markers and did not develop de novo HBV infection. The vaccinated anti-HBc positive recipient without HBV vaccine response was HBV-DNA positive in serum and liver, viral DNA was continuously negative in the following tests, so a spontaneous seroconversion was diagnosed.

CONCLUSION: The presence of anti-HBs as a result of HBV vaccine or past HBV infection seems to be effective at protecting patients receiving livers from anti-HBc positive donors. However, the emergence of immune escape HBV mutants, which can evade the anti-HBs protection, should be considered as a risk of HBV infection.

Prevention and treatment of recurrent Hepatitis B after liver transplantation: the current role of nucleoside and nucleotide analogues

The Hepatitis B virus (HBV) is a DNA virus that can cause both acute and chronic liver disease in humans. Approximately 350–400 million people are affected worldwide and up to one million deaths occur annually from cirrhosis and hepatocellular carcinoma. When cirrhosis and liver failure develop, the definitive treatment of choice remains orthotopic liver transplantation (OLT). In the past, an unacceptable HBV recurrence rate with a high rate of graft loss was noted. The use of Hepatitis B immunoglobulin (HBIG) has resulted in improved patient and graft survival rates. The addition of the nucleoside analog Lamivudine (LAM) to HBIG has improved these survival curves to an even greater degree. Prolonged use of LAM will almost invariably lead to the development of viral mutations resistant to the drug. There are now several other nucleoside and nucleotide analogs (Adefovir, Entecavir, Tenofovir, and Truvada) available for the clinician to utilize against these resistant strains. It should be possible to prevent recurrence in most, if not all, post-transplant patients and also to significantly reduce viral loads with normalization of transaminases in those who have developed recurrent infection. The antiviral regimen should be robust and minimize the risk of breakthrough mutations. A prudent approach may be the implication of combination antiviral therapy. This review summarizes the efficacy of previous regimens utilized to prevent and treat recurrent HBV following OLT. Particular attention will be paid to the newer nucleoside and nucleotide analogs and the direction for future strategies to treat HBV in the post transplant setting.

Production of recombinant humanized anti-HBsAg Fab fragment from Pichia pastoris by fermentation

In this report, we describe the high-yield secretory expression of the recombinant human anti-HBsAg Fab fragment from Pichia pastoris that was achieved by co-integration of the genes encoding the heavy and light chains (both under the control of alcohol oxidase promoter) into the genome of the yeast cells. The fed-batch fermentations were carried out in a 5 L scale. Both chains of the Fab were successfully expressed upon methanol induction. The absorbance (OD600) of the broth can reach 350 approximately 500 at the end of fed-batch phase. After the induction, the expression level of the recombinant Fab (soluble) reached 420 approximately 458 mg/L. The recombinant Fab fragment was purified from the crude culture supernatant by ion exchange chromatography and the purity of the recombinant Fab fragment was over 95%. The affinity activities of the crude fermentation supernatant and the purified Fab were analyzed by indirect ELISA, which showed that the purified recombinant Fab fragment had high affinity activity with hepatitis B surface antigen.

Is Hepatitis B Immunoglobulin Prophylaxis Needed for Liver Transplantation in the Era of New Antivirals?

Chronic infection with hepatitis B virus (HBV) is one of the most common causes of cirrhosis of the liver and hepatocellular carcinoma worldwide, frequently requiring liver transplantation. Other nonliver organ transplants get infected de novo or through reactivation from previous active or inactive infections. With significant improvements in the surgical techniques and immunosuppressive regimens over the last 20 years, organ transplantation has become the most effective and lifesaving therapy for patients with chronic renal failure, cirrhosis, hepatocarcinoma, and heart failure. Until recently chronic HBV infection was considered a formal contraindication for liver transplantation, since recurrence of infection without prophylaxis occurs in 75% to 90% of the patients, with significant morbidity and mortality and few therapeutic alternatives. However, the introduction of hepatitis B immunoglobulin (HBIG) a decade ago to reduce the risk of reinfection of liver grafts, and more recently the availability of nucleoside analogues with few side effects and easy administration, have led to a dramatic improvement in patient outcomes with a risk of long-term HBV reinfection of less than 10% with combined HBIG and lamivudine prophylaxis. Chronic HBV infection in kidney, heart, and other organs has become a serious long-term problem and one of the most frequent and important comorbidities affecting graft and patient survival. Fortunately the introduction of nucleoside analogues allows significant control of viral replication and prevents progression of liver disease and other organ damage. In the present article we discuss the current indications for HBV prophylaxis and treatment prior to and after organ transplantation, as well as the most cost-effective way to apply different regimens to reduce side effects and improve survival and quality of life after transplantation.

Transgenic plant-derived pharmaceuticals – the practical approach?

Production of biopharmaceuticals in transgenic plants would involve the creation of a new industry. Those transgenic plants, including staple food crops, could provide many benefits to people all over the world. However, the new industry might require a strict regulation system. It is probable that such a strict system would not be acceptable to Japan or to most developing countries. Many countries should use non-food crops for production of biopharmaceuticals and take on more simple systems. The new industry must develop strategies for promoting the benefits of transgenic plant-derived biopharmaceuticals on both the domestic and worldwide scales.

Treatment of hepatitis B and C after liver transplantation. Part 1, hepatitis B

The outcome of OLT for HBV-related liver disease is dependent on the prevention of allograft re-infection. Over the past decade, major advances have been made in the management of HBV transplant candidates. The advent of long-term hepatitis B immune globulin (HBIG) administration as a prophylaxis against HBV recurrence, and the introduction of new antiviral agents against HBV infection, such as lamivudine (LAM), were a major breakthrough in the management of these patients. Results of OLT for HBV infection are similar to those achieved with other indications. Pre-OLT antiviral treatment such as LAM can suppress HBV replication before OLT and thus decrease the risk of re-infection of the graft. Combination prophylaxis with LAM and HBIG after transplantation highly effectively reduces the rate of HBV re-infection, even in HBV replicative cirrhotic patients. The optimal HBIG protocol in the LAM era is yet to be defined: dosing of HBIG, routes of administration, and possibility of stopping HBIG. Several antiviral drugs have been developed for the management of HBV infection on the graft, so outcome is currently good.

Hepatitis B and hepatitis C viruses in liver transplantation

Liver transplantation (LT) for end-stage liver disease (ESLD) secondary to hepatitis viruses has evolved rapidly during the last two decades. ESLD secondary to hepatitis C virus (HCV) accounts for approximately 50% of LT in the United States and Europe. Despite the decrease in the number of new HCV infections, the prevalence of advanced HCV-related liver disease is steadily increasing. In light of the near universal recurrence of posttransplantation HCV infection and our limited ability to treat recurrent disease, transplantation is in danger of being overrun by viral hepatitis, unless effective strategies can be used to treat disease, expand the donor pool of available organs, and prevent disease recurrence. In the early 1980s, results of LT for chronic hepatitis B virus infection were hampered by recurrent infection and subsequent allograft failure. However, with the introduction of passive immunoprophylaxis with hepatitis B immunoglobulin and treatment with potent nucleoside analogs, there has been a resurgence of LT for hepatitis B virus-related ESLD. Despite the wide acceptance of LT as a therapy for ESLD, there is little consensus on the appropriate immunosuppressive regimens, and prophylactic and therapeutic treatments vary widely from one center to another. This review summarizes available data and highlights appropriate strategies to improve outcomes.

Transgenic tobacco cells producing the human monoclonal antibody to hepatitis B virus surface antigen

The recombinant human monoclonal antibody (MAb) against hepatitis B virus (HBV) surface antigen (HBsAg) was expressed in tobacco suspension cultures. The parental CL4MAb was produced by the Epstein-Barr virus (EBV) transformed human cell line TAPC301-CL4. The CL4MAb cDNA was introduced into tobacco suspension cells by Agrobacterium mediated transformation. The monoclonal antibodies (MAbs), B294 and B303, which were derived from CL4 and subsequently produced in plant cells were selected for study. After purification on Protein A columns, B294 and B303 MAbs had anti-HBs relative affinity constants similar to the parental CL4MAb. B303 MAb interacted with cell surface HBsAgs and showed complement-dependent cytotoxicity in a manner that was similar to anti-HBs human immunoglobulins (HBIg) that are used clinically. The results of this study point to the feasibility of producing MAbs to HBsAg in plants as an alternative to HBIg.