The immunogenicity of human-origin therapeutic antibodies are associated with V gene usage

Therapeutic antibodies can elicit unwanted immune responses in a subset of patients, which leads to the production of anti-drug antibodies (ADA). Some of these ADAs have been reported to effect the pharmacokinetics, efficacy and/or safety of the therapeutic antibodies. The sequence diversity of antibodies are generated by VDJ recombination and mutagenesis. While the antibody generation process can create a large candidate pool for identifying high-affinity antibodies, it also could produce sequences that are foreign to the human immune system. However, it is not clear how VDJ recombination and mutagenesis impact the clinical ADA rate of therapeutic antibodies. In this study, we identified a positive correlation between the clinical ADA rate and the number of introduced mutations in the antibody sequences. We also found that the use of rare V alleles in human-origin antibody therapeutics is associated with higher risk of immunogenicity. The results suggest that antibody engineering projects should start with frameworks that contain commonly used V alleles and prioritize antibody candidates with low number of mutations to reduce the risk of immunogenicity.

An Anticancer Drug Cocktail of Three Kinase Inhibitors Improved Response to a Dendritic Cell-Based Cancer Vaccine

Monocyte-derived dendritic cell (moDC)-based cancer therapies intended to elicit antitumor T-cell responses have limited efficacy in most clinical trials. However, potent and sustained antitumor activity in a limited number of patients highlights the therapeutic potential of moDCs. In vitro culture conditions used to generate moDCs can be inconsistent, and moDCs generated in vitro are less effective than natural DCs. On the basis of our study highlighting the ability for certain kinase inhibitors to enhance tumor antigenicity, we therefore screened kinase inhibitors for their ability to improve DC immunogenicity. We identified AKT inhibitor MK2206, DNA-PK inhibitor NU7441, and MEK inhibitor trametinib as the compounds most effective at modulating moDC immunogenicity. The combination of these drugs, referred to as MKNUTRA, enhanced moDC activity over treatment with individual drugs while exhibiting minimal toxicity. An evaluation of 335 activation and T-cell-suppressive surface proteins on moDCs revealed that MKNUTRA treatment more effectively matured cells and reduced the expression of tolerogenic proteins as compared with control moDCs. MKNUTRA treatment imparted to ICT107, a glioblastoma (GBM) DC-based vaccine that has completed phase II trials, an increased ability to stimulate patient-derived autologous CD8+ T cells against the brain tumor antigens IL13Rα2(345-354) and TRP2(180-188) In vivo, treating ICT107 with MKNUTRA, prior to injection into mice with an established GBM tumor, reduced tumor growth kinetics. This response was associated with an increased frequency of tumor-reactive lymphocytes within tumors and in peripheral tissues. These studies broaden the application of targeted anticancer drugs and highlight their ability to increase moDC immunogenicity.

Immunological targeting of CD133 in recurrent glioblastoma: A multi-center phase I translational and clinical study of autologous CD133 dendritic cell immunotherapy

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Background: A hallmark of glioblastoma is the high incidence of tumor recurrence, thought to be triggered by cancer stem cells. These tumorigenic cells are resistant to irradiation and chemotherapeutic agents. The target antigen, CD-133, was chosen because it has been reported as a cancer stem cell antigen overexpressed in glioblastoma tumors and associated with shorter survival. Recent clinical trials suggest that the mean overall survival for these patients is roughly 5-9 months, emphasizing the important unmet medical need in this disease requiring additional strategic approaches. Dendritic cell immunotherapies such as ICT-121 could provide benefit to patients by educating their immune systems to induce the formation of cytotoxic T cells that attack tumor cells bearing the target antigen. In addition to immediate attack on tumor cells present at dosing, a long-term memory response effective against tumor recurrence might be induced. Immunotherapy, such as ICT-121, that targets cancer stem cells could be an important treatment for this disease. Methods: This Phase I multi-center trial of ICT-121 targeting CD133 was designed to assess safety and tolerability (primary endpoint) and to monitor overall survival and progression-free survival (secondary endpoints). ICT-121 is comprised of autologous dendritic cells that are loaded with two HLA-A2 restricted epitopes of the CD133 antigen. CD133 is overexpressed on glioblastoma cancer stem cells. The HLA-A2 patients that had undergone resection for recurrence of glioblastoma were treated with ICT-121 once a week for 4 weeks during the induction phase and then once every 2 months during the maintenance phase until disease progression, death, ICT-121 depletion or discontinuation. Results: A total of 20 patients were treated and eight of these patients are still alive. Immune response data with cytokine mRNA expression demonstrated a response to the CD133 epitopes. A total of 20 patients were treated and eight of these patients are still alive. Conclusions: The results from this Phase I trial suggest that ICT-121 is both safe and well-tolerated with an immune response seen in a subset of patients. Clinical trial information: NCT02049489.

Clinical Manifestations of an Anti-Drug Antibody Response: Autoimmune Reactions

Antibodies can be generated against a therapeutic protein upon administration to human subjects. When the therapeutic protein closely mimics one of the subject's endogenous proteins, those antibodies might bind to the endogenous protein in addition to the therapeutic protein. This scenario results when tolerance to the endogenous protein is broken. The consequences of breaking tolerance include an autoimmune response where antibodies are generated against the endogenous protein. These autoantibodies could have significant clinical relevance depending on several factors, including the redundancy of action of the endogenous protein as well as the concentration, binding affinity, and neutralizing potential of the antibodies. The consequences of a therapeutic-protein-induced autoimmune reaction can be challenging to manage as the stimulus for further perpetuation of the immune response can shift from the therapeutic protein to the endogenous protein. The potential for inducing an autoimmune response is one of the reasons that the immune response to a therapeutic protein should be monitored if it persists through the end of the study.

Should we continue to drain the pylorus in patients undergoing an esophagectomy?

A systematic review of the literature was performed to assess the necessity of a pyloric drainage procedure during an esophagectomy with gastric conduit reconstruction. Earlier data recommend performing a pyloric drainage procedure for all esophagectomies; however, recent studies have questioned this. A thorough literature search (January 2001-November 2011) was performed using the terms esophagectomy, pyloroplasty, pyloromyotomy, botulinum toxin, and pyloric drainage. Only studies that compared patient outcome after undergoing an esophagectomy with a pyloric drainage procedure with those undergoing an esophagectomy without a pyloric drainage procedure were selected. Only four studies, comprising 668 patients in total, were identified that compared patient outcome after undergoing an esophagectomy with or without a pyloric drainage procedure, and two additional meta-analyses were identified and selected for discussion. All studies were retrospective, and because of the heterogeneity of studies, patient demographics, reporting, and statistical analysis of patient outcome, pooling of data and meta-analysis could not be performed. Careful analysis demonstrated that pyloric drainage procedure was associated with a non-significant trend for delayed gastric emptying and biliary reflux, while not affecting the incidence of dumping. No correlation was determined between a pyloric drainage procedure and anastomotic leaks, postoperative pulmonary complications, length of hospital stay, and overall perioperative morbidity. While there are risks associated with a pyloric drainage procedure and data exist supporting its omission during an esophagectomy, no good conclusion can be drawn from the current literature. Larger multi-institutional, prospective studies are required to definitively answer this question.

Stratification of antibody-positive subjects by antibody level reveals an impact of immunogenicity on pharmacokinetics

The availability of highly sensitive immunoassays enables the detection of antidrug antibody (ADA) responses of various concentrations and affinities. The analysis of the impact of antibody status on drug pharmacokinetics (PK) is confounded by the presence of low-affinity or low-concentration antibody responses within the dataset. In a phase 2 clinical trial, a large proportion of subjects (45%) developed ADA following weekly dosing with AMG 317, a fully human monoclonal antibody therapeutic. The antibody responses displayed a wide range of relative concentrations (30 ng/mL to >13 μg/mL) and peaked at various times during the study. To evaluate the impact of immunogenicity on PK, AMG 317 concentration data were analyzed following stratification by dose group, time point, antibody status (positive or negative), and antibody level (relative concentration). With dose group as a stratifying variable, a moderate reduction in AMG 317 levels (<50%) was observed in antibody-positive subjects when compared to antibody-negative subjects, but the difference was not statistically significant in all dose groups. The most significant reduction in AMG 317 levels was revealed when antibody data was stratified by both time point and antibody level. In general, high ADA concentrations (>500 ng/mL) and later time points (week 12) were associated with significantly (up to 97%) lower trough AMG 317 concentrations. The use of quasi-quantitative antibody data and appropriate statistical methods was critical for the most comprehensive evaluation of the impact of immunogenicity on PK.

Immunogenicity issues in drug development

Immunogenicity is an important factor that manufacturers must consider as they develop new protein therapeutics. It is important to understand the immunogenicity of new proteins both at the preclinical phase and in the clinical phase of development. This paper provides an overview of the issues that manufacturers should consider including some of the potential reasons that some proteins induce an immune response, a discussion regarding current methodology used to understand immunogenicity, and some examples of marketed protein therapeutics with immunogenicity issues. Given the increasing scrutiny from regulatory agencies around the way immunogenicity is assessed by manufacturers, the strategy of detecting and characterizing antibodies that are formed against protein therapeutics is becoming an important topic. Screening assays are typically performed first on all serum samples collected in the course of a trial to detect the presence of antibodies that can bind to the protein therapeutic. There are several platforms in use: radioimmune precipitation assays (RIP), enzyme linked immunosorbent assays (ELISA), electrochemiluminescent assays (ECL), and biosensor-based assays. Each has its advantages and disadvantages, and needs to be evaluated to identify the optimal platform for a specific therapeutic protein. Once antibodies are identified, a confirmatory assay is performed to verify and characterize the antibodies. A biological assay should be used next to test if these antibodies are capable of neutralizing the biological effect of the drug. Any sample that is positive for neutralizing antibodies, indicates that the antibody is probably having an impact on the patient's ability to derive full benefit from the therapeutic protein, and may be critical for patient safety.

Development and characterization of a human antibody reference panel against erythropoietin suitable for the standardization of ESA immunogenicity testing

Recombinant human erythropoietin (EPO) has been used therapeutically for more than two decades in the treatment of anemia. Although EPO is generally well tolerated, in rare cases, patients have developed anti-EPO antibodies that can negatively impact safety and efficacy. Therefore, the detection of antibodies against EPO is a regulatory requirement during clinical development and post-approval. Although it is a rare phenomenon, antibody-mediated pure red cell aplasia (PRCA) is a serious complication than can result from antibodies that develop and neutralize EPO as well as endogenous erythropoietin. Currently, there are no universally accepted analytical methods to detect the full repertoire of binding and neutralizing anti-EPO antibodies. A number of different methods that differ in terms of antibodies detected and assay sensitivities are used by different manufacturers. There is also a lack of antibody reference reagents, and therefore no consistent basis for detecting and measuring anti-EPO antibodies. Reference reagents, with established ranges, are essential to monitor the safety and efficacy of all erythropoiesis-stimulating agents (ESAs) structurally related to human erythropoietin. This is the first report of the development and characterization of a panel of fully human antibodies against EPO suitable as reference reagents. The characteristics of antibodies within the panel were selected based on the prevalence of non-neutralizing IgG and IgM antibodies in non-PRCA patients and neutralizing IgG antibodies, including IgG1 and IgG4, in antibody-mediated PRCA subjects. The reference panel includes antibodies of high- and low-affinity with binding specificity to neutralizing and non-neutralizing erythropoietin epitopes. The subclass of human antibodies in this reference panel includes an IgG1, IgG2, and IgG4, as well as an IgM isotype. This antibody panel could help select appropriate immunogenicity assays, guide validation, and monitor assay performance. Further, this human anti-ESA antibody panel may help set the limits of each assay platform in terms of the full repertoire of the anti-ESA antibodies, and may facilitate standardization of ESA immunogenicity reporting across assay platforms.

Epitope characterization of pre-existing and developing antibodies to an aglycosylated monoclonal antibody therapeutic of G1m17,1 allotype

Allotypes of IgG1 molecules can influence the immunogenicity of therapeutic monoclonal antibodies and may account for the presence of some pre-existing antibodies. An electrochemiluminescent (ECL) bridging immunoassay was used to characterize the binding epitopes of anti-therapeutic antibodies (ATAs) in a Phase 1 single ascending dose clinical trial of a therapeutic aglycosylated IgG1monoclonal antibody (mAb). There was no evidence for ATAs specific for a possible neo-epitope created due to the lack of glycosylation. ATAs that developed post-treatment were specific for the F(ab')2, whereas, pre-existing ATAs were specific to the Fc region. Further characterization of the pre-existing ATAs identified the specific epitope to be the G1m1 allotype determinant in the Fc of the therapeutic. A novel competitive bridging assay was developed to verify that serum IgG1 from subjects with pre-existing anti-G1m1 antibodies was homozygous for the antithetical allotype (G1m3). The endogenous G1m allotype of all subjects was assessed and correlation to ATA incidence and adverse events was evaluated. Interestingly, the pre-existing anti-allotype antibody in subjects persisted but was not augmented after dosing, indicating the lack of a secondary immune response to this epitope. These studies indicate the relationship of the therapeutic allotype and the corresponding allotype of subjects is an important component to further understand the impact of immunogenicity on the safety and efficacy of therapeutic antibodies.

Extent of lymph node resection does not increase perioperative morbidity and mortality after surgery for stage I lung cancer in the elderly

BACKGROUND & OBJECTIVES

Pathologic evaluation of > 10 lymph nodes (LNs) is considered necessary for accurate lung cancer staging. However, physicians have concerns about increased risk in perioperative mortality (POM) and morbidity with more extensive LN sampling, particularly in the elderly. In this study, we compared the outcomes in elderly patients with stage I non-small cell lung cancer (NSCLC) undergoing extensive (> 10 nodes) and limited (≤ 10 nodes) LN resections.

METHODS

Using data from the Surveillance, Epidemiology and End Results registry linked to Medicare records, we identified 4975 patients ≥ 65 years of age with stage I NSCLC who underwent a lobectomy between 1992 and 2002. Risk of perioperative morbidity and POM after the evaluation of ≤ 10 vs. >10 LNs was compared among patients after adjusting for propensity scores.

RESULTS

Multiple regression analysis showed similar POM between the two groups (OR, 1,01; 95% CI, 0,71-1,44). Other postoperative complications were similar across groups except for thromboembolic events, which were more common among patients undergoing resection of > 10 LNs (OR, 1,72; 95% CI, 1,12-2,63).

CONCLUSIONS

These data suggest that evaluation of > 10 LNs, which allows for more accurate staging, appears to be safe in the elderly patients undergoing lobectomy for stage I NSCLC without compromising postoperative recovery.

Immunogenicity of panitumumab in combination chemotherapy clinical trials

BACKGROUND

Panitumumab is a fully human antibody against the epidermal growth factor receptor that is indicated for the treatment of metastatic colorectal cancer (mCRC) after disease progression on standard chemotherapy. The purpose of this analysis was to examine the immunogenicity of panitumumab and to evaluate the effect of anti-panitumumab antibodies on pharmacokinetic and safety profiles in patients with mCRC receiving panitumumab in combination with oxaliplatin- or irinotecan-based chemotherapies.

METHODS

Three validated assays (two screening immunoassays and a neutralizing antibody bioassay) were used to detect the presence of anti-panitumumab antibodies in serum samples collected from patients enrolled in four panitumumab combination chemotherapy clinical trials. The impact of anti-panitumumab antibodies on pharmacokinetic and safety profiles was analyzed using population pharmacokinetic analysis and descriptive statistics, respectively.

RESULTS

Of 1124 patients treated with panitumumab in combination with oxaliplatin- or irinotecan-based chemotherapy with postbaseline samples available for testing, 20 (1.8%) patients developed binding antibodies and 2 (0.2%) developed neutralizing antibodies. The incidence of anti-panitumumab antibodies was similar in patients with tumors expressing wild-type or mutant KRAS and in patients receiving oxaliplatin- or irinotecan-based chemotherapies. No evidence of an altered pharmacokinetic or safety profile was found in patients who tested positive for anti-panitumumab antibodies.

CONCLUSIONS

The immunogenicity of panitumumab in the combination chemotherapy setting was infrequent and similar to the immunogenicity observed in the monotherapy setting. Panitumumab immunogenicity did not appear to alter pharmacokinetic or safety profiles. This low rate of immunogenicity may be attributed to the fully human nature of panitumumab.

Strategy to confirm the presence of anti-erythropoietin neutralizing antibodies in human serum

Functional cell-based assays are the preferred method to test for the presence of anti-rHuEPO neutralizing antibodies (NAbs). However, due to the unpredictable nature of test serum matrix effects on cell-based assays, confirmatory assays are essential for verifying NAb positive results observed during the course of sample testing. The cell-based assay used for the detection of NAbs described by Wei et al. [1] used 32D-EPOR cells, a murine myeloid cell line transfected with the human EPO receptor (EPOR). The 32D-EPOR cell line responded to either rHuEPO or murine interleukin 3 (mIL-3) with proliferation. NAbs were expected to only inhibit rHuEPO-induced cell proliferation and not mIL-3 induced proliferation. Due to reliance on proliferation, the results from this cell-based assay can be confounded by the presence of non-antibody inhibitory serum factors. This paper describes a strategy for confirming that the inhibition of rHuEPO-induced proliferation in a cell-based assay is only attributable to NAbs. The strategy of antibody depletion uses a resin mixture composed of Protein G Sepharose and Protein L Sepharose (Protein G/L resin) to significantly reduce the concentration of immunoglobulins of IgG, IgM and IgA isotypes from human serum prior to testing in the cell-based assay. If the reduction in immunoglobulins in a serum sample corresponds to a reduction in inhibition of EPO-induced proliferation, it would infer that EPO neutralizing activity is antibody-mediated and not due to non-antibody inhibitory serum factors.

Assessment of immunogenicity of romiplostim in clinical studies with ITP subjects

Romiplostim is an Fc-peptide fusion protein that activates intracellular transcriptional pathways via the thrombopoietin (TPO) receptor leading to increased platelet production. Romiplostim has been engineered to have no amino acid sequence homology to endogenous TPO. Recombinant protein therapeutics can be at a risk of development of an antibody response that can impact efficacy and safety. Hence, a strategy to detect potential antibody formation to the drug and to related endogenous molecules can be useful. The immunogenicity assessment strategy involved both the detection and characterization of binding and neutralizing antibodies. The method for detection was based on a surface plasmon resonance biosensor platform using the Biacore 3000. Samples that tested positive for binding antibodies in the Biacore immunoassay were then tested in a neutralization assay. Serum samples from 225 subjects with immune thrombocytopenic purpura (ITP) dosed with romiplostim and 45 ITP subjects dosed with placebo were tested for romiplostim and TPO antibodies. Prior to romiplostim treatment, 17 subjects (7%) tested romiplostim antibody positive and 12 subjects (5%) tested TPO antibody positive for pre-existing binding antibodies. After romiplostim exposure, 11% of the subjects exhibited binding antibodies against romiplostim and 5% of the subjects with ITP showed binding antibodies against TPO. The antibodies against romiplostim did not cross-react with TPO and vice versa. No cases of anti-TPO neutralizing antibodies were detected in romiplostim-treated subjects. The incidence of anti-romiplostim neutralizing antibodies to romiplostim was 0.4% (one subject); this subject tested negative at the time of follow-up 4 months later. No impact on platelet profiles were apparent in subjects that had antibodies to romiplostim to date. In summary, administration of romiplostim in ITP subjects resulted in the development of a binding antibody response against romiplostim and TPO ligand. One subject developed a neutralizing antibody response to romiplostim that impacted the platelet counts of this subject. No neutralizing antibodies to endogenous TPO were observed.

Comparing exponentially weighted moving average and run rules in process control of semiquantitative immunogenicity immunoassays

The immunogenicity immunoassay validation process ensures development of a robust, reproducible method. However, no matter how well developed, validated, and maintained a method is, in the course of running a large number of samples over time, it is not uncommon to see bad reagents, poorly calibrated equipment, personnel errors, or other unknown and unpredictable factors that have an impact in the performance of the method and quality of the sample results. The immunogenicity immunoassay thus needs to be closely monitored with an internal statistical quality control process overtime to ensure a consistent and reliable output. The statistical process control has been widely applied to monitor manufacturing processes and in clinical laboratories. Its application to immunogenicity immunoassays is relatively novel. Limited guidance is available to implement the process to monitor semiquantitative immunogenicity immunoassay performance. Here, we have performed a suitability evaluation for process control charts with actual laboratory data from three immunogenicity immunoassay methods each utilizing a different technology platform. Additionally, a panel of prepared samples designed to assess long-term method performance were periodically evaluated for over a year. Finally, we make recommendations for an internal quality control process based on the results of these evaluations.

A step-wise approach for transfer of immunogenicity assays during clinical drug development

We designed a three-step statistical approach to transfer bioanalytical assays (ELISA and Biacore) which evaluates the (1) average equivalence between the two labs (2) concordance in individual sample results between the two labs, and (3) long-term stability of assay performance. Each experimental design evaluated the contribution of four critical variables to the overall variability. Two lots of each variable were examined in a controlled experiment. The variables tested for ELISA were analyst, plate washer, biotinylated-therapeutic protein, and streptavidin-horseradish peroxidase; and for Biacore were analyst, instrument, chip lot, and conjugation chemistry reagent lots. Equivalence in the mean signal to noise (S/N) or mean relative units (RU) between the two labs was established through statistical evaluation of the assay performance characteristics across multiple assay variables. Concordance between the two labs in the individual sample results was subsequently verified both quantitatively and qualitatively. The long-term maintenance of assay stability was monitored by performance testing of a predefined set of samples which were prepared in sufficient quantities to last several years. The process of method validation for biomarker testing in clinical trials is to analyze the variability of the assay performance. However, different factors contribute to this variability and need to be evaluated when the method is transferred to another site/lab. Lack of understanding the critical variables can potentially result in unexpected problems and delays. The three-step statistical approach of assay transfer provides a robust process for transferring complex biological assays.

Influence of race on kidney transplantation in the Department of Defense healthcare system

BACKGROUND

We report the influence of race on transplant outcomes in the Department of Defense (DOD) system.

METHODS

Retrospective cohort analysis of all kidney transplants performed at WRAMC from 1996 to 2005. Kaplan-Meier analysis was used to assess for differences in graft survival, and Cox regression was used to calculate adjusted hazard ratios for graft loss. For our analyses, we used the cutoff of 6 years (year 2000) when we introduced thymoglobulin induction; maintenance immunosuppression consisted of mycophenolate mofetil and tacrolimus, and rapid steroid taper (completed withdrawal at 6 weeks) was used for all patients.

RESULTS

There were 220 transplants (91 Blacks, 107 Caucasians and 22 Asians). Because the curve for graft survival for Blacks over time violated the proportional hazards assumption (at 6 years post-transplant), analysis was segregated into two segments. Through 6 years of follow-up, graft survival was 77% for Blacks and 81% for non-Blacks (p = 0.74 by log rank). Through 9 potential years of follow-up, graft survival for Blacks was 56% and 78% for Whites (p = 0.005). In Cox regression analysis, Black race, compared with non-Black race, was not significantly associated with graft loss at 6 years, but was significantly associated with graft loss occurring after 6 years.

CONCLUSIONS

In the DOD health system, no significant differences were seen in graft survival among recipients of different races at 6 years. Black recipients who received a kidney transplant before the year 2000 showed decreased graft survival compared to non-Blacks. This was consistent with change in immunosuppressive regimen in our institution with the introduction of thymoglobulin induction and maintenance therapy with tacrolimus, mycophenolate mofetil and withdrawal of prednisone at 6 weeks.

The development and validation of a sensitive, dual-flow cell, SPR-based biosensor immunoassay for the detection, semi-quantitation, and characterization of antibodies to darbepoetin alfa and epoetin alfa in human serum

A surface plasmon resonance (SPR)-based biosensor immunoassay was developed and validated using the Biacore 3000 instrument to detect, semi-quantitate, and characterize serum antibodies against darbepoetin alfa (Aranesp) and epoetin alfa (EPOGEN). In this sensitive, dual-flow cell assay, epoetin alfa and darbepoetin alfa are covalently immobilized onto consecutive flow cells of a carboxymethyl dextran-coated sensor chip. Diluted human serum samples are injected sequentially over both surfaces. The binding of serum antibodies to the immobilized proteins are detected and recorded in real time based on the principles of SPR. Furthermore, antibody binding is confirmed with a secondary anti-human immunoglobulin antibody. Positive samples are further characterized to determine the relative concentration of the antibodies using an affinity-purified, rabbit anti-epoetin alfa antibody as a reference control. The assay can detect 80ng/ml and 100ng/ml of antibody to epoetin alfa and darbepoetin alfa, respectively. The dynamic range of the assay is from 0.078microg/ml to 10microg/ml using a rabbit antibody with demonstrated accuracy and intra- and inter-assay precision. Approximately 80 serum samples can be analyzed on each sensor chip while maintaining a stable baseline and consistent immunological reactivity. The analysis of serum samples from subjects administered with epoetin alfa or darbepoetin alfa provided evidence that the assay can detect varying concentrations of antibodies of different off rates, isotypes, and IgG subclasses.

Feasibility of a multiplex flow cytometric bead immunoassay for detection of anti-epoetin alfa antibodies

Immunogenicity profiles of recombinant therapeutic proteins are important to understand because antibodies raised against these molecules may have important clinical sequelae. The purpose of the present study was to demonstrate that a flow cytometric bead array could be used to detect clinically relevant antibodies with specificity to such therapeutics. We chose to evaluate well-characterized specimens from persons treated with epoetin alfa that developed antibody-mediated pure red blood cell aplasia as a means to demonstrate the utility of this platform. Our data show that this assay is capable of detecting anti-epoetin alfa antibodies with a relative antibody concentration of 50 ng/ml, where 25 of 25 sera spiked with antibodies at this concentration scored positive. Moreover, the assay was designed to include positive and negative control beads for each specimen that is processed to ensure the specificity of the signal when detected. Measurement of interassay precision supports quantitative estimates of relative antibody concentrations in the range of 313 to 5,000 ng/ml, where the percent coefficient of variation did not exceed 20%. With respect to clinical specimens, antibodies with specificity for epoetin alfa could be easily detected in a set of specimens from persons with pure red blood cell aplasia that had prior exposure to the EPREX brand of recombinant epoetin alfa. Further development and validation of this approach may facilitate successful widespread application of the method for detection of anti-epoetin alfa antibodies, as well as antibodies directed against other recombinant therapeutic proteins.

Development of a Maturing T-Cell-Mediated Immune Response in Patients with Idiopathic Parkinson’s Disease Receiving r-metHuGDNF Via Continuous Intraputaminal Infusion

The development of a maturing T-cell-mediated immune response was characterized in Parkinson's disease subjects receiving recombinant human glial-derived neurotrophic factor (r-metHuGDNF) via continuous bilateral intraputaminal infusion. Eighteen of 34 subjects tested positive for anti-r-metHuGDNF-binding antibodies. Four subjects developed neutralizing activity, three of which demonstrated classic immunoglobulin class switching from IgM to IgG. An increase of anti-r-metHuGDNF IgG-binding antibodies correlated with the development of neutralizing activity. All serum samples from two subjects with neutralizing activity were characterized for IgG subclasses. These data revealed an initial anti-r-metHuGDNF IgG population where IgG1 >> IgG2 >> IgG4, and IgG3 concentrations were negligible. However, continued antigenic stimulation resulted in concentration changes where IgG4 > IgG1> IgG2, indicating a mature immune response. In addition, using in silico techniques, two immunodominant MHC class II T-cell epitopes were predicted for the native GDNF sequence. These data demonstrate development of a mature T-cell-mediated immune response in these subjects.

Comparing ELISA and Surface Plasmon Resonance for Assessing Clinical Immunogenicity of Panitumumab

Evaluation of the immunogenicity of panitumumab, a fully human anti-epidermal growth factor receptor mAb approved for use in colorectal cancer patients, led to the development of two separate immunoassays for the detection of anti-panitumumab Abs. The first immunoassay used a bridging ELISA capable of detecting 10 ng/ml positive control anti-panitumumab Ab. The ELISA incorporated an acid dissociation step to reduce drug interference and tolerated the presence of approximately 100-fold molar excess of drug. During eight clinical trials, the ELISA detected developing Ab responses in 2 of 612 (0.3%) subjects. In one of the ELISA positive subjects, neutralizing Abs were detected using an epidermal growth factor receptor phosphorylation bioassay. The second immunoassay used a Biacore biosensor immunoassay format capable of detecting 1 mug/ml positive control Ab while tolerating the presence of equal molar amounts of drug. Although less sensitive and less tolerant to competing drug in the assay, the Biacore assay detected developing Ab responses in 25 of the 604 (4.1%) subjects. Additionally, the Biacore assay identified eight subjects who developed neutralizing Abs. Mouse mAbs with affinities ranging from 1.1 x 10(-6) to 8.4 x 10(-10) M were used to characterize both assay types. The ELISA was more sensitive for the detection of higher affinity mAbs and detected high-affinity mAbs in the presence of higher molar ratio of drug to mAb. The Biacore assay was more sensitive for detection of lower affinity mAbs and detected low affinity Abs in the presence of higher molar ratios of drug to mAb.

Recommendations for the design, optimization, and qualification of cell-based assays used for the detection of neutralizing antibody responses elicited to biological therapeutics

The administration of biological therapeutics can evoke some level of immune response to the drug product in the receiving subjects. An immune response comprised of neutralizing antibodies can lead to loss of efficacy or potentially more serious clinical sequelae. Therefore, it is important to monitor the immunogenicity of biological therapeutics throughout the drug product development cycle. Immunoassays are typically used to screen for the presence and development of anti-drug product antibodies. However, in-vitro cell-based assays prove extremely useful for the characterization of immunoassay-positive samples to determine if the detected antibodies have neutralizing properties. This document provides scientific recommendations based on the experience of the authors for the development of cell-based assays for the detection of neutralizing antibodies in non-clinical and clinical studies.

Development and validation of a quantitative cell-based bioassay for comparing the pharmacokinetic profiles of two recombinant erythropoietic proteins in serum

An in vitro cell-based bioassay was developed and validated to assess the pharmacokinetic profiles of two novel therapeutic recombinant proteins (EP1 and EP2) with erythropoiesis stimulating properties in Sprague-Dawley rats. While immunoassays are the standard choice for evaluating the pharmacokinetic parameters of drugs, no immunoassay was available for EP2, necessitating the need for a quantitative bioassay capable of measuring both EP1 and EP2 separately so that appropriate comparisons could be made. The bioassay described here utilizes a sub clone of the murine 32D cell line transfected with the gene encoding for the human erythopoietin (HuEPO) receptor. Erythropoietin (EPO), EP1 and EP2 exert their proliferative effect on the cell line by signaling through the HuEPO receptor. The proliferation induced by the erythropoietic proteins was measured by [methyl-(3)H]thymidine incorporation into the cellular DNA. The assay was conducted in 96-well microtiter plates and had relatively high throughput. The Guidelines of the International Conference on Harmonization (ICH) were followed for the validation of the different assay parameters including robustness, linearity, accuracy, precision, limit of quantitation (LOQ) and specificity. The robustness of the bioassay is demonstrated by the lack of an effect of age of the 32D cell culture on the performance of the EP2 bioassay. The bioassay demonstrated good linearity, yielding a coefficient of determination of 0.99 or higher for both EP1 and EP2. The assay showed reproducible dose-response curves for EP1 in the range of 0.039-2.5 ng/mL and for EP2 in the range of 0.125-8 ng/mL. The accuracy estimates ranged between 98% and 108% for EP1 and between 90% and 110% for EP2 in the reproducible range mentioned above. Intermediate precision (within-plate R.S.D.) in the same range was within 26% and 17% for the EP1 and EP2 bioassays, respectively. The validated bioassays for EP1 and EP2 were utilized to quantitatively analyze serum samples from a pharmacokinetic study conducted to compare the profiles of the two compounds in Sprague-Dawley rats.

A novel method for detecting neutralizing antibodies against therapeutic proteins by measuring gene expression

The presence of neutralizing antibodies against protein therapeutics is a concern in the biomedical field. Such antibodies not only reduce the efficacy of protein therapeutics, but also impose potential dangers to the patients receiving them. To date, a small number of in vitro cell-based bioassays for detecting neutralizing antibodies against therapeutic proteins have been developed. Most of the existing assays, however, either involve the use of radioactive materials or have limited sensitivities and/or poor specificities. With advances in mRNA profiling and detection techniques, we have established a novel and non-radioactive bioassay system using branched DNA (bDNA) technology for detecting protein-therapeutic neutralizing antibodies in patient serum. Our assay measures the variations of target gene expression that reflect the biologic effect of the therapeutic agent and the capability of the antibodies, if present, to neutralize the therapeutics. Compared with most existing assays, the new assay is more sensitive and specific, and completely eliminates the use of radioactive materials. Application of the new assay system can be widely expanded if new target genes and responding cell lines for other therapeutics are identified or engineered.

Recommendations for the design and optimization of immunoassays used in the detection of host antibodies against biotechnology products

Most biopharmaceutical therapeutics elicit some level of antibody response against the product. This antibody response can, in some cases, lead to potentially serious side effects and/or loss of efficacy. Therefore, the immunogenicity of therapeutic proteins is a concern for clinicians, manufacturers and regulatory agencies. In order to assess immunogenicity of these molecules, appropriate detection, quantitation and characterization of antibody responses are necessary. Inadequately designed antibody assays have led to the hampering of product development or, during licensure, post-marketing commitments. This document provides scientific recommendations based on the experience of the authors for the development of anti-product antibody immunoassays intended for preclinical or clinical studies. While the main focus of this document is assay design considerations, we provide scientific focus and background to the various assay performance parameters necessary for developing a valid assay. Sections on assay performance parameters, including those that appear in regulatory guidances, are contained in this manuscript.

Acute renal allograft rejection following pegylated IFN-alpha treatment for chronic HCV in a repeat allograft recipient on hemodialysis: a case report

Interferon alpha (IFN-alpha) can be effective therapy for patients with chronic kidney disease who have chronic hepatitis C (HCV). However, acute allograft rejection has been reported in association with IFN-alpha following kidney transplantation, and therefore IFN therapy is recommended prior to, rather than after, kidney transplantation whenever feasible. The special case of repeat allograft recipients who contract HCV after the first transplantation presents special difficulties. This report features the case of a repeat allograft recipient who presented with neutropenic fevers after 5 months of pegylated IFN-alpha therapy, initiated 6 months following the functional loss of his third graft and the reinitiation of hemodialysis (HD). Physical exam, radiographic and laboratory findings led to allograft nephrectomy. The pathologic findings supported a diagnosis of acute-on-chronic rejection. This represents a rare case of IFN-alpha induced rejection following allograft failure and return to HD in a repeat allograft recipient. It also calls attention to the need for a high index of suspicion for the development of allograft rejection, which may require allograft nephrectomy even after allograft 'failure'.

Detection of neutralizing anti-therapeutic protein antibodies in serum or plasma samples containing high levels of the therapeutic protein

Neutralizing antibodies against therapeutic proteins can be potentially harmful if the antibody blocks not only the therapeutic activities of the therapeutic protein but also the normal functions of the endogenous counterpart. Detection of the neutralizing anti-therapeutic protein antibodies generally relies on bioassays measuring changes in the biologic activity of the therapeutic protein triggered by the presence of the antibody. Most of the bioassays, particularly the cell-based in vitro assays, fail to detect neutralizing anti-therapeutic protein antibodies when the remaining therapeutic protein level in the assay samples is high. The remaining therapeutic protein, either a free molecule or an immune complex with anti-therapeutic protein antibodies, can inhibit the neutralizing activity of the antibody and prevent detection. We describe the development of a procedure that uses acid dissociation and affinity adsorption to remove therapeutic protein from assay samples. With this procedure, we can detect the presence of neutralizing anti-therapeutic protein antibodies from samples containing high levels of therapeutic protein.

An acid dissociation bridging ELISA for detection of antibodies directed against therapeutic proteins in the presence of antigen

Bridging Enzyme-Linked Immunosorbent Assay (ELISA) is commonly used in detection of antibodies directed against therapeutic proteins. Advantages of the bridging ELISA include the capability to detect antibodies regardless of their isotype or the species of origin. However, detection of antibodies can be difficult, if not impossible, in the presence of high levels of the antigen in the sample matrix. This protocol describes a bridging ELISA that uses a covalently coupled high density antigen surface combined with an acid dissociation step to allow for antibody detection in the presence of antigen in human serum.

Assays for detecting and diagnosing antibody-mediated pure red cell aplasia (PRCA): an assessment of available procedures

Antibody (Ab)-mediated pure red cell aplasia (PRCA) develops when patients mount a neutralizing Ab response to recombinant erythropoiesis-stimulating agents (ESAs) such as epoetin-alpha (EPO). These neutralizing Abs can also cross-neutralize endogenous EPO, leading to a state of absolute EPO resistance and transfusion dependence. The diagnosis of Ab-mediated PRCA in part relies on the sensitive and specific detection of serum anti-EPO Abs and a confirmatory examination of patients' bone marrow for lack of erythroid precursors. To date, a variety of assays have been used to detect anti-EPO Abs, including radioimmunoprecipitation (RIP) assay, enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR) and bioassays that measure neutralizing Abs. Each of these assays can yield informative results and possess characteristic benefits and limitations, so it is unclear whether or not a "superior" assay is required or possible. To date, a universal standardized assay has not yet been established that would facilitate the comparison of Ab data derived from different laboratories and retrospective analysis of stored sera. This review evaluates the results of studies measuring anti-EPO Abs with different assays and compares their relative advantages and disadvantages in terms of specificity, sensitivity, ease of use and ability to measure Ab-binding affinities and subclasses. These comparisons provide a basis for determining the optimal assay(s) for screening and/or analysis of patients' serum for anti-EPO Abs during treatment or after onset of Ab-mediated PRCA.

Characterization of an immune response

The characterization of any detected antibodies provides detailed information that can be critical to understanding the significance of an immune response. The BIAcore immunoassay provides a straightforward means of characterizing many aspects of the immune response including antibody concentration, specificity, binding affinity, and the presence of isotypes. One important aspect of the immune response is determination of neutralizing capability, which requires a biological assay. The ultimate clinical significance of an immune response can only be fully understood when data from antibody characterization are coupled with clinical data from the patient. Some of the factors that can contribute to the clinical significance of an immune response are: (i) magnitude of the immune response (concentration of antibodies detected); (ii) duration of the immune response (continuous antibody production or sporadic and not sustained); (iii) correlation with any adverse events; (iv) correlation with a change in pharmacokinetics (either mediating sustained circulation or enhanced clearance of the drug); (v) biological neutralization of the drug; (vi) biological neutralization of an endogenous protein. Full characterization of the immune response requires the incorporation of antibody assays, pharmacokinetic assays, and clinical data.

Development and validation of a cell-based bioassay for the detection of neutralizing antibodies against recombinant human erythropoietin in clinical studies

An in vitro cell-based bioassay capable of detecting neutralizing antibodies (NAb) to recombinant human erythropoietin (rHuEPO) in clinical samples was developed and validated. The bioassay uses the IL-3-dependent murine 32D cell line transfected with human EPO receptors (EPOR). This cell line responds to rHuEPO with proliferation measurable by [methyl-3H] thymidine incorporation into the cellular DNA. The reduction of rHuEPO-induced cell proliferation response indicates the possible presence of anti-rHuEPO NAb. In addition, a specificity assay using murine IL-3 (mIL-3) induced proliferation of the same cell line was developed and validated. The specificity assay allowed testing of samples that inhibited the biologic activity of rHuEPO to evaluate whether the inhibition was specific and not attributable to cytotoxicity of the serum sample. Both assays are conducted in a 5% human serum matrix in 96-well microtiter plates. The Guidelines of the International Conference on Harmonization (ICH) were followed for the validation of different assay parameters including analytical recovery, precision, sensitivity, specificity, selectivity, and robustness. The anti-rHuEPO NAb assay is capable of detecting concentrations of NAb equivalent to 500 ng/ml of the positive control antibody in undiluted human serum. The anti-rHuEPO NAb assay yielded consistent results with cells cultured for up to 30 days. The positive control antibody maintained its ability to inhibit the biologic activity of rHuEPO upon freezing and thawing. The presence of free rHuEPO in serum samples interfered with the detection of the antibody. The validated assay was sensitive, specific and robust and was successfully used to monitor NAb development in patients.

Evaluation of methods to detect and characterize antibodies against recombinant human erythropoietin

BACKGROUND

From May 1998 to November 2000, 13 European patients developed antibody-mediated pure red cell aplasia during treatment with recombinant human erythropoietin (rHuEPO), reinforcing the need for analytical testing for antibodies against erythropoietic agents. Specimens from 8 patients were provided for further antibody testing and characterization.

METHODS

We evaluated 4 analytical methods with these sera: radioimmune precipitation (RIP), enzyme-linked immunosorbent assay (ELISA), biosensor immunoassay, and a bioassay for identification of neutralizing antibodies.

RESULTS

The RIP, biosensor immunoassay, and biological assay performed equally to detect and quantify anti-rHuEPO antibodies. The ELISA failed to detect antibodies in 2 patient samples. The biosensor immunoassay could determine antibody isotypes, subclasses, and dissociation rates and the bioassay could determine whether these antibodies were able to neutralize the biological effect of the drug; the other assays could not make this determination.

CONCLUSION

We recommend the use of the biosensor immunoassay followed by a bioassay to best identify and characterize anti-rHuEPO antibodies. The biosensor immunoassay allows for identification of all classes and subclasses of immunoglobulins and is a preferred method for the identification of lower-affinity antibodies. The bioassay is needed to determine if the antibodies identified have the capacity to neutralize a biological effect of the drug in a cell-based system.

Drug-induced and antibody-mediated pure red cell aplasia: a review of literature and current knowledge

Anti-erythropoietin (EPO)-induced pure red cell aplasia (PRCA) is an uncommon, potentially life-threatening condition in which the bone marrow stops manufacturing red blood cells. In the past few years, reports of drug-induced, anti-EPO antibody-mediated PRCA have increased substantially, with most cases attributed to the use of one erythropoiesis-stimulating protein, Eprex. A literature review was undertaken to document the reports of drug-induced PRCA, with all drugs and drug regimens. The sudden increase in reports of antibody-mediated PRCA is discussed.

New technologies for the detection of antibodies to therapeutic proteins

The determination of antibody formation in response to a therapeutic product requires that a variety of data be evaluated. In addition to examining immuno-assay and bioassay results, it is important to determine any clinical relevance. By also examining pharmacokinetic data as well as other clinical results, an evaluation can be made as to whether any clinically relevant antibodies were generated. To help in this evaluation, it is important to fully characterize the antibodies that are generated. Both the BIAcore and IGEN platforms are powerful tools for determining if antibodies have been produced in a subject The BIAcore is also able to characterize these antibodies as to isotype, relative concentration, and relative affinity. The bioassay result can identify serum samples that contain an agent capable of inhibiting a biological effect of a drug. When combined with the results of an immuno-assay, it is possible to determine if the antibodies are capable of neutralizing the drug.

Use of preoperative functional neuroimaging to predict language deficits from epilepsy surgery

BACKGROUND

Left anterior temporal lobectomy (L-ATL) may be complicated by confrontation naming deficits.

OBJECTIVE

To determine whether preoperative fMRI predicts such deficits in patients with epilepsy undergoing L-ATL.

METHODS

Twenty-four patients with L-ATL underwent preoperative language mapping with fMRI, preoperative intracarotid amobarbital (Wada) testing for language dominance, and pre- and postoperative neuropsychological testing. fMRI laterality indexes (LIs), reflecting the interhemispheric difference between activated volumes in left and right homologous regions of interest, were calculated for each patient. Relationships between the fMRI LI, Wada language dominance, and naming outcome were examined.

RESULTS

Both the fMRI LI (p < 0.001) and the Wada test (p < 0.05) were predictive of naming outcome. fMRI showed 100% sensitivity and 73% specificity in predicting significant naming decline. Both fMRI and the Wada test were more predictive than age at seizure onset or preoperative naming performance.

CONCLUSIONS

Preoperative fMRI predicted naming decline in patients undergoing left anterior temporal lobectomy surgery.

Use of biosensors to monitor the immune response

Biosensor instruments, such as the BIACORE, are gaining popularity for analysing serum samples for the presence of antibodies. These instruments offer several advantages in the detection and subsequent characterization of clinically relevant antibodies generated in response to administration of therapeutic proteins. Much like other common immunoassay platforms, immobilized ligand is used to capture antibodies. Unlike conventional approaches, the ligand is immobilized to the surface of a biosensor chip, with detection based upon surface plasmon resonance. This assay platform, therefore, does not require reporter molecules such as enzymes, fluorochromes or radioisotopes that are common to conventional immunoassay methodologies. Additional desirable features of the biosensor platform include real-time detection of the binding of antibody to ligand (for kinetic measurements) as well as straightforward characterization of antibody isotype, specificity and relative concentration. This is all performed with minimum serum requirements (typically 10 microlitres per sample analysed) in a fully automated environment. The unique features of the biosensor instrument warrant that these assays are referred to as biosensor immunoassays to clearly distinguish them from more conventional immunoassay methodologies, such as ELISA.

Validation of the BIACORE 3000 platform for detection of antibodies against erythropoietic agents in human serum samples

OBJECTIVE

To develop a validated BIACORE immunoassay for the detection and characterization of serum antibodies with specificity for erythropoietic molecules (e.g. darbepoetin alfa).

METHODS

New Zealand White rabbits (n = 8) were immunized by an intramuscular injection of darbepoetin alfa/adjuvant at 0, 4, 6, and 8 weeks. Serum was collected for 6 weeks after final injection and pooled for affinity purification. Antibody immunoassay measurements were performed using a BIACORE 3000 with darbepoetin alfa immobilized to the biosensor surface. Human serum samples were spiked with the affinity-purified rabbit antibody to develop and validate the BIACORE immunoassay.

RESULTS

The assay was shown to be stable through 180 sample/regeneration cycles and had a threshold of 45.8 response units. The validated limit of detection was 0.40 microg/ml in 100% human serum. The method was robust, with variability not exceeding a 20% coefficient of variation, well within acceptable limits for typical immunoassays.

CONCLUSION

All protein-based therapeutics have a potential for immunogenicity, and antibodies raised against these molecules may have important clinical sequelae. The biotechnology and pharmaceutical industries are challenged to address this potential by developing robust analytical platforms to detect and characterize antibodies directed against therapeutic proteins in clinical specimens. Traditionally, radioimmune precipitation assays and/or enzyme-linked immunoassays (ELISAs) are used for primary detection of host immune response; however, the BIACORE platform may be better suited for this purpose in many instances. This platform represents a robust tool that should be considered for the detection and characterization of antibodies directed against protein-based therapeutics.

Spatial variation of plasma flow in the oxazolone-stimulated microcirculation

INTRODUCTION

In cutaneous lymphocytic inflammation, enhanced regional blood flow is suggested by persistent erythema and warmth. Direct assessment of the microcirculation, however, has been limited by tissue edema and skin thickness.

METHODS

To assess the microcirculatory adaptations to the epicutaneous antigen oxazolone, we studied the first pass kinetics and microvascular topography of the inflammatory skin microcirculation using a specially adapted epi-illumination intravital microscopy system. The fluorescence intravital videomicroscopy and streaming image acquisition of fluorescein-labeled dextran (approximately 500,000 MW) injections were used to assess changes in plasma flow.

RESULTS

Direct plasma tracer injections of both the oxazolone-stimulated and control microcirculation demonstrated comparable transit times (leading edge and intensity-weighted peak times) from the carotid artery to the superficial vascular plexus (p > 0.05). In contrast to transit times, continuous infusion of the plasma tracer demonstrated a significant increase in the delivery of the fluorescein-labeled dextran to the oxazolone-stimulated microcirculation. Quantitative morphometry of intravital microscopic images demonstrated a 2.2-fold increase in the mean diameter of vessels in the superficial vascular plexus (p < 0.01). Further, fluorescence intensity mapping indicated that the increase was associated with increased perfusion of focal regions of the superficial vascular plexus (p < 0.001).

CONCLUSIONS

These results indicate that the oxazolone-stimulated adaptations of the inflammatory microcirculation include both microvascular dilatation and the redistribution of plasma flow.

Esophagectomy for esophageal cancer

This review considers the esophagectomy techniques in the treatment of esophageal cancer and provides the guidelines for optimizing the patients' chances at cure, minimizing the risk of mediastinal enteric leak (which carries a mortality rate as high as 50%) and minimizing associated pulmonary insufficiency and infection. The 4 most commonly used routes for resection and replacement include a transhiatal, transthoracic (Ivor-Lewis), tri-incisional (right chest then simultaneous abdominal and left neck), and left chest (distal tumors). Each of these techniques will be described as will the use of colon and jejunum for esophageal replacement. The healthy stomach is the preferred conduit for esophageal replacement. The stomach is well vascularized, easily reaches to the neck, and requires only a single anastomosis for re-establishing intestinal continuity. When the stomach is not available (usually because of prior surgery or disease) the choice of conduits include colon and jejunum. With respect to minimally invasive esophagectomy for esophageal cancer, several groups have significant experience with this and report excellent results. This is an evolving technique but holds much promise for improving the quality of life of patients with cancer without compromising their survival. In locally advanced middle third tumors, thoracotomy and dissection under direct vision's desirable and improves the safety of the operation. The same may apply to tumors receiving neoadjuvant therapy. For tumors of the distal esophagus, transhiatal, tri-incisional, and Ivor-Lewis resection are probably equally as safe, and appear to result in equivalent long-term survival. An intrathoracic anastomotic leak is disastrous, carrying a mortality rate of up to 50%. Any surgeon who performs esophagectomy with an intrathoracic anastomosis must do so with a low incidence of leakage, certainly under 5%. Consideration should be given to a cervical placement if there are factors increasing the risk such as the use of induction therapy.

Impact of HIV seropositivity on graft and patient survival after cadaveric renal transplantation in the United States in the pre highly active antiretroviral therapy (HAART) era: an historical cohort analysis of the United States Renal Data System

BACKGROUND

National statistics are presented for patient survival and graft survival in patients seropositive for the human immunodeficiency virus (HIV+) at the time of renal transplantation in the era prior to highly active antiretroviral therapy (HAART).

METHODS

Historical cohort analysis of 63, 210 cadaveric solitary renal transplant recipients with valid HIV serology entries in the United States Renal Data System (USRDS) from 1 January 1987 to 30 June 1997. The medical evidence form was also used for additional variables but, because of fewer available values, was analyzed in a separate model. Outcomes were patient characteristics and survival associated with HIV+ status.

RESULTS

Thirty-two patients (0.05%) in the study period were HIV+ at transplant. HIV+ patients were comparable to the national renal transplant population in terms of gender and ethnic distribution but were younger and had younger donors and better HLA matching than the USRDS population. Patient and graft three-year survival were significantly reduced in HIV+ recipients (53% graft, 83% patient survival) relative to the USRDS population (73% and 88%, respectively). In multivariate analysis, HIV+ status was independently associated with patient mortality and decreased graft survival in recipients of cadaveric kidney transplants.

CONCLUSIONS

This analysis was retrospective and may underestimate the number of HIV+ patients transplanted in the United States. Although the clinical details of patient selection for transplant were unknown, these results show HIV+ patients can have successful outcomes after cadaveric renal transplantation, although outcomes are significantly different from HIV- recipients.