Treatment of fulminant acute Hepatitis B with nucles(t)id analogues is safe and does not lead to secondary chronification of Hepatitis B.

Background: Acute hepatitis B virus (HBV) infection is still a major cause of acute liver failure (ALF), necessitating a high rate of emergency liver transplantation (LTx). Acute infection is followed by high viral replication rates leading to hepatocyte death and, ultimately, ALF. The objective of treating HBV-induced ALF thus is to eliminate, or significantly suppress, HBV replication and therefore reduce cell death and support regeneration. Objective: In this retrospective study, we want to evaluate the timing, the safety, and the long-term virological outcome of this approach. Methods/results: In this study, we included 32 patients (16 female and 16 males; median age 39.5 years) with ALF due to hepatitis B, who were transferred to the university hospital Essen, Germany between January 2009 and December 2013. Before treatment, transaminases were highly elevated, bilirubin was increased, and elevated international normalized ratio (INR) revealed impaired liver function. HBV-DNA and HBsAg were positive. All 32 patients received oral antiviral treatment (3 lamivudine, 21 entecavir, and 8 tenofovir) between 1 day and 4 months after diagnosis of acute hepatitis B. One patient died, 2 were transplanted, one died shortly after LTx the other patient survived after LTx. These 3 patients received treatment in a state of advanced liver failure, and 1 patient 4 months after initial diagnosis of hepatitis B. Twenty-nine patients survived without LTx. Five patients were discharged without further follow-up. All 24 remaining patients became HBV-DNA negative in median of 100 days. Twenty-two patients were followed further, and all patients lost their HBsAg in median of 108 days. Sixteen of the 22 patients experienced a seroconversion to anti-HBs in median of 137 days. Four patients who were followed for 1 more year after HBsAg did not develop anti-HBs. None of the patients developed chronic hepatitis B. Conclusion: Immediate treatment of HBV-induced ALF with nucleos(t)id-analogues (NUCs) appears save and prevents LTx and death, and there is no indication for increased chronicity.

[HCV reinfection after liver transplantation - management and first experiences with telaprevir-based triple therapy]. / HCV-Reinfektion nach Lebertransplantation. Management und erste Ergebnisse mit der Telaprevir-basierten Triple-Therapie.

BACKGROUND AND OBJECTIVE: The management of hepatitis C virus (HCV) recurrence after liver transplantation (LTx) is a major challenge in patient care. For patients with HCV GT1, treatment standard with pegylated interferon (PEG-IFN) and ribavirin (RBV) has been augmented in 2011 by first generation protease inhibitors (PI), telaprevir (TVR) and boceprevir (BOC). We report our first experiences with TVR-based triple therapy in patients with GT1-reinfection of the graft. PATIENTS AND METHOD: 13 patients with histologically proven HCV GT1-reinfection of the graft received 12 weeks of PEG-IFN/RBV/TVR followed by 12 weeks of PEG-IFN/ RBV only. During the triple therapy phase immune suppression was tightly monitored, and the patients were also closely monitored for side effects. RESULTS: The dosage of immunosuppressants had to be reduced significantly (TAC: 30-fold; CSA 3,5-fold). Stable levels were achieved by daily or over-daily dosing of a special size application of 0,1 mg tacrolimus (Tac) bid or a minimal dose of 10 mg cyclosporine (CSA) bid or qd, respectively. In all patients hematological side effects were observed, 65 % of which required RBV dose reduction, administration of erythropoietin or blood transfusions. Increase of kidney retention values requiring infusions occurred in 50 %. All side effects were reversible. There were no early discontinuations of therapy. An early viral response (EVR) with viral decline below limit of detection was noted at week 12 in 9/13 patients and at week 12 in further 3 patients. CONCLUSION: Our preliminary results show high EVR response rates of TVR-based triple therapy in LTx patients with HCV-GT1 re-infection.

Acute management of refractory variceal bleeding in liver cirrhosis by self-expanding metal stents.

BACKGROUND AND AIMS: Current treatment strategies of variceal bleeding (VB) include banding and sclerotherapy. However, up to 10% of bleeding events remain refractory to standard therapy with high mortality. With this study, we aimed to evaluate the implantation of self-expanding metal stents (SEMS) for the management of therapy-refractory variceal bleeding. PATIENTS AND METHODS: Eight cirrhotic patients who presented to our unit with a total of 9 refractory bleeding events were treated by SEMS placement. RESULTS: Stenting resulted in immediate hemostasis in all cases without recurrent bleeding with SEMS in situ. After stabilization, 1 patient was treated by transjugular intrahepatic portosystemic shunt (TIPS) and after the second bleeding episode by TIPS dilation. One patient underwent orthotopic liver transplantation (OLT). The remaining patients were treated with standard drug regimens to reduce portal pressure. The SEMS were removed after a median of 11 days. No acute hemorrhage was noted on stent retrieval. While no early rebleeding occurred in the patients after TIPS implant, TIPS dilation or OLT, 3 out of 5 patients on conservative treatment experienced recurrence of VB within 9 days after SEMS removal. CONCLUSIONS: SEMS placement sufficiently stops hemorrhage in refractory VB. Due to the high rebleeding rate after conservative treatment alone following SEMS removal, this procedure may be utilized as a mere bridging method. Additional interventional and/or surgical methods to effectively reduce portal pressure (i.e. TIPS, OLT) should be considered. Further studies to evaluate the optimum treatment algorithm of refractory esophageal VB are warranted.

Glutathione-S-transferase subtypes α and π as a tool to predict and monitor graft failure or regeneration in a pilot study of living donor liver transplantation.

OBJECTIVE: Glutathione-S-transferase (GST) subtype α and π are differentially expressed in adult liver tissue. Objective of the study was if GST α and π may serve as predictive markers for liver surgery, especially transplantations. METHODS: 13 patients receiving living donor liver transplantation (LDLT) and their corresponding donors were analyzed for standard serum parameters (ALT, AST, γGT, bilirubin) as well as GST-α and -π before LDLT and daily for 10 days after LDLT. Patients (R) and donors (D) were grouped according to graft loss (R1/D1) or positive outcome (R2/D2) and above named serum parameters were compared between the groups. RESULTS: R1 showed significantly increased GST-α and significantly lower GST-π levels than R2 patients or the donors. There was a positive correlation between GST-α and ALT, AST as well as bilirubin and a negative correlation to γGT. However, γGT correlated positively with GST-π. Graft failure was associated with combined low GST-π levels in donors and their recipients before living donor liver transplantation. CONCLUSION: Our data suggest that high GST-α serum levels reflect ongoing liver damage while GST-π indicates the capacity and process of liver regeneration. Additionally, GST-π may be useful as marker for optimizing donor and recipient pairs in living donor liver transplantation.

A Rare Case of Propofol-Induced Acute Liver Failure and Literature Review.

The incidence of drug-induced acute liver failure is increasing. A number of drugs can inhibit mitochondrial functions, alter ß-oxidation and cause accumulation of free fatty acids within the hepatocytes. This may result in hepatic steatosis, cell death and liver injury. In our case, propofol, an anesthetic drug commonly used in adults and children, is suspected to have induced disturbance of the mitochondrial respiratory chain, which in consequence led to insufficient energy supply and finally liver failure. We report the case of a 35-year-old Caucasian woman with acute liver failure after anesthesia for stripping of varicose veins. Liver histology, imaging and laboratory data indicate drug-induced acute liver failure, presumably due to propofol. Hepatocyte death and microvesicular fatty degeneration of 90% of the liver parenchyma were observed before treatment with steroids. Six months later, a second biopsy was performed, which revealed only minimal steatosis and minimal periportal hepatitis. We suggest that propofol led to impaired fatty acid oxidation possibly due to a genetic susceptibility. This caused free fatty acid accumulation within hepatocytes, which presented as hepatocellular fatty degeneration and cell death. Large scale hepatocyte death was followed by impaired liver function and, consecutively, progressed to acute liver failure.

Acute liver failure in a metropolitan area in Germany: a retrospective study (2002 - 2008).

OBJECTIVES: To determine current etiologies of acute liver failure (ALF) and clinical and laboratory parameters associated with the outcome upon ALF, so as to identify the frequency of present causes of ALF in Germany as well as potential new prognostic parameters. PATIENTS: 134 adult patients (63 % females / 37 % males) aged 41 +/- 16 years (median: 38 years) with established ALF criteria. DESIGN AND SETTING: A retrospective study (1 / 2002 - 4 / 2008) on ALF patients from the Ruhr Area, the largest urban region located in northwestern Germany. Clinical and laboratory data were collected for a period of four weeks after study admission. RESULTS: Etiologies of ALF were identified as drug toxicity (39.6 % of the cases); combined viral hepatitides (23.1 %); or miscellaneous (16.4 %). In 20.9 % of the cases, the etiology remained indeterminate. Overall patient survival at four weeks was 81.3 %. While 89 patients (66.4 %) recovered under best supportive therapy, 26 patients (19.4 %) had to undergo liver transplantation. Increased body mass indices were significantly (p < 0.003) associated with a poor outcome. Intriguingly, high levels of cholestatic enzymes significantly (p < 0.01) correlated with a positive outcome. CONCLUSIONS: In providing first data on current ALF etiologies Germany, this study reveals that drug toxicity - in particular due to acetaminophen - has replaced viral hepatitis as the most single frequent cause of ALF in a densely populated urban area; this correlates with similar findings in the USA, the UK and Scandinavia. Lower body mass indices and elevated cholestatic enzyme levels had statistically significant prognostic power.

Core promoter mutant HBV non-responding to adefovir after viral breakthrough on lamivudine: rapid virologic response to tenofovir plus lamivudine in a cirrhotic patient.

BACKGROUND: In chronic hepatitis B patients undergoing therapy with LAM or ADV, viral breakthrough is possible due to the emergence of drug resistance. LAM resistant HBV strains are susceptible to ADV, while ADV resistant mutants remain sensitive to LAM. CASE REPORT: A male patient with HBV-related cirrhosis developed viral breakthrough (HBV DNA>1.8 x 106 IU/ml) after 4 1/2 years of treatment with LAM, and therapy was switched to ADV (10 mg/d). After three months, HBV remained highly replicative without any changes of ALT values, and ADV dose was increased (20 mg/d). Because of unchanged VL sequence analysis was performed three months later, which showed the mutation (rtS219A) and the concomitant mutation (sS210R) and 2 mutations in core promoter region (A1762T), (G1764A). During the sixth month of ADV monotherapy the patient developed liver failure. After administration of TDF plus LAM, HBV DNA became undetectable within 39 days. At day 41, the patient underwent OLT. TDF plus LAM were well tolerated, and the patient maintained undetectable HBV DNA levels, and in addition to HBIG a sustained HBsAg negative status over twenty-eight months post OLT. CONCLUSION: TDF plus LAM is a safe drug combination in case of viral breakthrough during LAM treatment and subsequent primary non-response to ADV. High VL persisting for >or= 6 months of continuous antiviral treatment may indicate drug resistance. Especially in cirrhotic patients with LAM resistance, "add on" of a nucleotide analogue is the right therapeutic strategy even before viral breakthrough gets apparent.

An antibiotic complex from Lysobacter enzymogenes strain C3: antimicrobial activity and role in plant disease control.

Lysobacter enzymogenes C3 is a bacterial biological control agent that exhibits antagonism against multiple fungal pathogens. Its antifungal activity was attributed in part to lytic enzymes. In this study, a heat-stable antifungal factor (HSAF), an antibiotic complex consisting of dihydromaltophilin and structurally related macrocyclic lactams, was found to be responsible for antagonism by C3 against fungi and oomycetes in culture. HSAF in purified form exhibited inhibitory activity against a wide range of fungal and oomycetes species in vitro, inhibiting spore germination, and disrupting hyphal polarity in sensitive fungi. When applied to tall fescue leaves as a partially-purified extract, HSAF at 25 mug/ml and higher inhibited germination of conidia of Bipolaris sorokiniana compared with the control. Although application of HSAF at 12.5 mug/ml did not reduce the incidence of conidial germination, it inhibited appressorium formation and suppressed Bipolaris leaf spot development. Two mutant strains of C3 (K19 and DeltaNRPS) that were disrupted in different domains in the hybrid polyketide synthase-nonribosomal peptide synthetase gene for HSAF biosynthesis and had lost the ability to produce HSAF were compared with the wild-type strain for biological control efficacy against Bipolaris leaf spot on tall fescue and Fusarium head blight, caused by Fusarium graminearum, on wheat. Both mutant strains exhibited decreased capacity to reduce the incidence and severity of Bipolaris leaf spot compared with C3. In contrast, the mutant strains were as efficacious as the wild-type strain in reducing the severity of Fusarium head blight. Thus, HSAF appears to be a mechanism for biological control by strain C3 against some, but not all, plant pathogenic fungi.

Health status in patients with Alzheimer's disease: an investigation of inter-rater agreement.

OBJECTIVE: The purpose of the present study was to examine the level of agreement between health status ratings provided by patients with Alzheimer's disease and by their proxies. BACKGROUND: Because proxy-completed responses are often necessary in assessing health outcomes for the elderly, it is necessary to determine the feasibility and potential limitations of using proxies as a patient substitutes. METHODS: To assess the potential utility of proxy responses on health status when subjects present a cognitive impairment, this study compared the responses of 70 subjects with Alzheimer's disease and those of their family and/or care provider proxy using the SF-36. Agreement between proxies and patients was measured by intraclass correlation coefficients (ICCs). RESULTS: The proportion of exact agreement between patients and proxies on the 36 items ranged from 3.3 to 41.7%. Results reveal poor to moderate agreement between patient and proxy reports. Proxy reliability varied according to the relationship of the proxy to the index subject. Agreement decreased significantly with increasing severity of dementia and with increasing severity of Physical status (Katz ADL). Agreement was better for measures of functions that are directly observable and relatively poor for more subjective measures. CONCLUSIONS: Our results confirm the importance of the information source used for patient health status.

Crohn's disease-induced non-alcoholic fatty liver disease (NAFLD) sensitizes for severe acute hepatitis B infection and liver failure.

Non-alcoholic fatty liver disease (NAFLD) commonly is associated with chronic inflammatory bowel disease (CIBD) and usually is considered to be stable and benign. However, NAFLD -- and in particular its subset, non-alcoholic steatohepatitis (NASH) -- may lead to progressive liver disease. Moreover, NAFLD sensitizes the liver to injury and increases the risk of developing acute-on-chronic liver failure following a "third hit". We here present one patient with NASH, as probably induced by long-standing Crohn's disease in the absence of ethanol consumption or abuse. The patient acquired an acute HBV infection and died from complications. As based on the clinical and histological findings, Crohn's disease appears to be a risk factor for developing NAFLD and thus to contribute to the progression into NASH. In conclusion, we suggest that Crohn's disease-related NAFLD may increase the vulnerability of the liver, which indicates that patients with a known history of CIBD merit special attention.

First Report of Leaf Spot of Smooth Bromegrass Caused by Pithomyces chartarum in Nebraska.

Smooth bromegrass (Bromus inermis Leyss.) is the most common perennial grass species cultivated for forage in North America. During late fall of 2004, smooth bromegrass plants in Lincoln, NE were observed to have brown lesions on leaf midveins that were several centimeters long. Symptomatic leaves were surface disinfested for 1 min in 2% NaOCl and incubated at 25°C on potato dextrose agar (PDA) and water agar. The fungus, Pithomyces chartarum (Berk. & Curt) Ellis, was isolated consistently and identified on the basis of morphological characteristics (1). Colonies were effused and black on PDA. Conidiophores measured 3.5 to 8 × 1.9 to 3.9 µm and were smooth and single. Conidia (7 to 25 × 9.5 to 14 µm) were broadly ellipsoidal, pale brown to dark brown, verrucose with mainly three transverse septa and one to two longitudinal septa. Pathogenicity tests were conducted on 50-day-old plants by spraying with a conidial suspension (2.5 × 105 spores per ml). Control plants were sprayed with sterile water. All plants were kept in a moist chamber (100% relative humidity) for 3 days and then transferred to a greenhouse (25°C, >70% relative humidity, and a 12-h photoperiod). One week after spraying, elongated lesions developed on leaf midveins of inoculated plants from which P. chartarum was consistently reisolated. No symptoms were observed on control plants. While P. chartarum has been described as a saprotroph or a parasite on a wide range of plants primarily in the tropics and subtropics, including the southern United States (2), it was reported previously on B. inermis only in Canada (3). This report expands the distribution and host range of P. chartarum as a pathogen in the United States. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England, 1971. (2) D. F. Farr et al. Fungal Databases, Systematic Botany and Mycology Laboratory, On-line publication. ARS, USDA, 2005. (3) J. H. Ginns. Compendium of Plant Disease and Decay Fungi in Canada 1960-1980. Res. Br. Can. Agric. Publ. 1813, 1986.

Mutagenesis of beta-1,3-Glucanase Genes in Lysobacter enzymogenes Strain C3 Results in Reduced Biological Control Activity Toward Bipolaris Leaf Spot of Tall Fescue and Pythium Damping-Off of Sugar Beet.

ABSTRACT Lysobacter enzymogenes produces extracellular lytic enzymes capable of degrading the cell walls of fungi and oomycetes. Many of these enzymes, including beta-1,3-glucanases, are thought to contribute to the biological control activity expressed by several strains of the species. L. enzymogenes strain C3 produces multiple extracellular beta-1,3-glucanases encoded by the gluA, gluB, and gluC genes. Analysis of the genes indicates they are homologous to previously characterized genes in the related strain N4-7, each sharing >95% amino acid sequence identity to their respective counterparts. The gluA and gluC gene products encode enzymes belonging to family 16 glycosyl hydrolases, whereas gluB encodes an enzyme belonging to family 64. Mutational analysis indicated that the three genes accounted for the total beta-1,3-glucanase activity detected in culture. Strain G123, mutated in all three glucanase genes, was reduced in its ability to grow in a minimal medium containing laminarin as a sole carbon source. Although strain G123 was not affected in antimicrobial activity toward Bipolaris sorokiniana or Pythium ultimum var. ultimum using in vitro assays, it was significantly reduced in biological control activity against Bipolaris leaf spot of tall fescue and Pythium damping-off of sugar beet. These results provide direct supportive evidence for the role of beta-1,3-glucanases in biocontrol activity of L. enzymogenes strain C3.

[Purpura fulminans. A fatal consequence of a widely used medication?]. / Purpura fulminans Fatale Folge einer alltäglichen Therapie?

A 39-year old man developed purpura fulminans, a manifestation of disseminated intravascular coagulopathy, with rhabdomyolsis following the i.m. injection of diclofenac.

Evaluation of the quality of life in dementia with a generic quality of life questionnaire: the Duke Health Profile.

OBJECTIVE: The study was designed to determine the acceptability, feasibility and validity of measuring quality of life in a representative sample of dementia patients with a generic instrument, the Duke Health Profile. METHOD: The French version of the Duke Health Profile was administered to 148 subjects with a mental disorder according to the DSM-III-R diagnostic criteria. The feasibility and acceptability of employing the instrument were determined by the refusal rate, the type of administration, and the percentage and distribution of missing data. Reliability was determined with Cronbach's alpha coefficient. Instrument reproducibility was assessed with the intraclass correlation coefficient for test-retest values. Internal construct validity was determined by factor analysis. Discriminant capacity was determined by comparing the average scores on each measure among patients with and without an additional chronic pathology. The measurements obtained were compared by source of information (patient, family proxy and care provider proxy). RESULTS: The feasibility and acceptability of the instrument was good. Only 2% of the patients refused to complete the questionnaire. Help from the interviewer was necessary in 79% of the cases. The average completion time was 10.6 min. Missing data exist in only 3.5% of the cases on average, except among patients with severe dementia (Mini Mental State Examination <10). For reliability, internal consistency was acceptable (Cronbach's coefficient alpha = 0.5--0.7) when the self-esteem (0.23) and social health (0.26) concepts were eliminated. Reproducibility as measured by test-retest scores was moderate to good (intraclass correlation coefficient r = 0.53--0.80), except for anxiety (0.48) and perceived health (0.45). Severity of dementia mainly affected the feasibility, acceptability and reproducibility of the instrument. The family proxy seemed to agree more with the patient than did the care provider proxy. CONCLUSION: Quality of life can be measured in patients with dementia, but special tools need to be developed for severe dementia.

Agreement between patients' and proxies' reports of quality of life in Alzheimer's disease.

Agreement between self reports and proxy reports of health-related quality of life (H RQoL) was examined in a sample of 76 patients with mild to moderate Alzheimer's disease and their proxies. Patients and proxies completed an '17-item Duke health profile'. The items were rephrased for the proxy. The proportion of exact agreement between patients and proxies on the 17 items ranged from 26.3 to 52.6%. Results reveal poor to moderate agreement (intraclass correlation coefficients (ICCs) from 0.00 to 0.61 for 10 subscales) between patients' and proxies' reports. Agreement was higher for measures of function that are directly observable (physical health, disability) and relatively poor for more subjective measures. Proxy reliability varied according to the relationship of the proxy to the index subject. Spouses and nurses agreed more closely with index subjects than did children or nurses' aides. Agreement decreased with increasing severity of dementia. Statistically significant differences in mean scores were noted for several dimensions, with proxies tending to rate the patients as having a lower quality of life than the patients themselves. This study indicates the importance of considering the information source of a patient's HRQoL. However, assessments by proxies should be used with caution.

Measuring general health status in dementia: practical and methodological issues in using the SF-36.

The objective of this study was to examine the measurement properties of the Medical Outcomes Study (MOS) 36-Item Short-Form health survey (SF-36) in a representative sample of dementia patients. A total of 138 subjects with dementia were evaluated with the SF-36. They were recruited from 16 centers, including 7 university hospital centers. Dementia severity, demographic variables, co-morbidity and functional limitations were also measured. The measurements obtained were compared by source of information (patient, family proxy, and care provider proxy). Thirteen patients refused to complete this questionnaire. Help from the interviewer was necessary in 72.8% of the cases. The average completion time was 18.8 minutes. Missing data exist in only 5.6% of the cases on average, except among patients with severe dementia (Mini Mental State Examination <10). With regard to reliability, internal consistency was acceptable to good; Cronbach's a ranged from a low of 0.59 to a high of 0.92 across subscales (median 0.75). Test-retest intraclass correlation coefficients were moderate to good (range 0.51-0.81) except for Role emotional (0.17), Bodily pain (0.49) and Mental health (0.45). For patients with MMSE > or = 15, test-retest coefficients were better (range 0.53-0.90). Intraclass correlation coefficient suggests that proxies are a poor substitute for obtaining a patient's perspective of his/her health status. In conclusion, the SF-36 is unsuitable for severe dementia, because severity of disease mainly affected the feasibility, acceptability, and reproducibility of the instrument. This study, however, confirms that it is possible to question subjects with mild to moderate dementia on their health status.

[Diagnosis of malnutrition in the elderly by dual energy absorptiometry]. / Diagnostic de la dénutrition chez les personnes âgées par l'absorptiométrie biénergétique.

OBJECTIVES: Denutrition is a frequent condition in elderly persons and may have major consequences. A noninvasive investigation, whole body dual energy X-ray absorptiometry, should allow, by direct measurement of body composition, early and reliable diagnosis of denutrition. This study was conducted to elaborate a diagnostic tool using this exam and to test its validity. PATIENTS AND METHODS: A global index of denutrition was proposed combining anthropometric, biological criteria, and the Mini Nutritional Assessment scale. Two agreement analyses were made between classical diagnostic criteria of nutritional status and body fat and fat free mass assessed by anthropometry and absorptiometry. An association between nutritional status and body absorptiometric composition were studied with univariate analysis followed by a multivariate logistic regression model. This model allowed an elaboration of a nutritional absorptiometric index (NAI). RESULTS: One hundred one elderly subjects were included. Twenty-three were considered to be in a state of denutrition. Agreement was poor between anthropometric and biological diagnostic criteria of denutrition. It was good between the different masses assess by anthropometry and absorptiometry. Subjects in a state of denutrition had significantly lower body fat and lower fat free mass. The fat free mass index (fat free mass divided by the square height) and body fat were entered into a logistic model and composed the NAI, which showed good diagnostic validity in terms of specificity and sensitivity. DISCUSSION: Absorptiometry appears to be a simple reliable diagnostic tool for assessing denutrition in elderly persons in routine practice. Further studies are required and should lead to a confirmation of the interest of these absorptiometric indexes.

New modular delivery system for diagnostic and therapeutic pre-targeting using tautomer-specific monoclonal antibody EM-6-47 and 3-substituted adenines.

We have developed a new modular affinity system for the 2-step delivery of functional molecules to target cells. The system is based on the tautomer-specific monoclonal antibody (MAb) EM-6-47, which binds to 3- and 3,8-substituted adenines with high affinity (Ka > 10(9) l/mol) without cross-reacting with naturally occurring purine derivatives. This MAb serves as the hapten-specific fusion partner to produce bispecific MAbs (bs-MAbs) recognizing a target cell antigen and a low-m.w. hapten as carrier molecule for, e.g., radionuclides. Either the C-8 or the N-3 position of adenines can be used for conjugation with effector molecules; the remaining position may be substituted with different moieties to modulate the pharmacokinetics of the haptens. Different 3- and 3,8-substituted adenines conjugated to the chelates DOTA and DTPA or to the drug daunomycin were synthesized. Adenine-chelate derivatives were efficiently labeled with (111)In and 90Y, while high-affinity binding of 3-substituted adenines to MAb EM-6-47 remained almost unaffected by the conjugation to radiochelates. To confirm the validity of the delivery system, a prototype bs-MAb, EM-168-47, was generated by somatic cell fusion of MAb EM-6-47 and MAb EM-168-2, the latter recognizing a surface antigen on canine hematopoietic cells. Two-step targeting assays in vitro verified the bs-MAb-mediated, dose-dependent delivery of (111)In-labeled adenine-chelate derivatives to myeloid cells. This system represents a powerful tool for new pre-targeting approaches relying on bs-MAbs and low-m.w. haptens. Suitable cellular antigens can be targeted by fusing the appropriate MAbs with hapten-specific MAb EM-6-47, and tailor-made 3-substituted adenines may be labeled with diagnostic or therapeutic radionuclides, cytotoxic drugs or other functional molecules.