Granzyme B PET Imaging of Immune Checkpoint Inhibitor Combinations in Colon Cancer Phenotypes

PURPOSE

Immune checkpoint inhibitor (ICI) monotherapy and combination regimens are being actively pursued as strategies to improve durable response rates in cancer patients. However, the biology surrounding combination therapies is not well understood and may increase the likelihood of immune-mediated adverse events. Accurate stratification of ICI response by non-invasive PET imaging may help ensure safe therapy management across a wide number of cancer phenotypes.

PROCEDURES

We have assessed the ability of a fluorine-labelled peptide, [18F]AlF-mNOTA-GZP, targeting granzyme B, to stratify ICI response in two syngeneic models of colon cancer, CT26 and MC38. In vivo tumour uptake of [18F]AlF-mNOTA-GZP following ICI monotherapy, or in combination with PD-1 was characterised and correlated with changes in tumour-associated immune cell populations.

RESULTS

[18F]AlF-mNOTA-GZP showed good predictive ability and correlated well with changes in tumour-associated T cells, especially CD8+ T cells; however, overall uptake and response to monotherapy or combination therapies was very different in the CT26 and MC38 tumours, likely due to the immunostimulatory environment imbued by the MSI-high phenotype in MC38 tumours.

CONCLUSIONS

[18F]AlF-mNOTA-GZP uptake correlates well with changes in CD8+ T cell populations and is able to stratify tumour response to a range of ICIs administered as monotherapies or in combination. However, tracer uptake can be significantly affected by preexisting phenotypic abnormalities potentially confusing data interpretation.

MicroRNA-30b regulates insulin sensitivity by targeting SERCA2b in non-alcoholic fatty liver disease

BACKGROUND & AIMS

Insulin resistance is strongly associated with non-alcoholic fatty liver disease, a chronic, obesity-related liver disease. Increased endoplasmic reticulum (ER) stress plays an important role in the development of insulin resistance. In this study, we investigated the roles of miRNAs in regulating ER stress in the liver of rats with obesity.

METHODS

We used miRNA microarray to determine the miRNA expression profiles in the liver of rats fed with a high fat diet (HFD). We used prediction algorithms and luciferase reporter assay to identify the target gene of miRNAs. To overexpress the miRNA miR-30b or inhibit miR-30b rats were injected with lentivirus particles containing PGLV3-miR-30b or PGLV3-miR-30b antimiR through tail vein. Hepatic steatosis was measured using transient elastography in human subjects.

RESULTS

Our data showed that miR-30b was markedly up-regulated in the liver of HFD-treated rats. Bioinformatic and in vitro and in vivo studies led us to identify sarco(endo)plasmic reticulum Ca²⁺ -ATPase 2b (SERCA2b), as a novel target of miR-30b. Overexpression of miR-30b induced ER stress and insulin resistance in rats fed with normal diet, whereas inhibition of miR-30b by miR-30b antimiR suppressed ER stress and insulin resistance in HFD-treated rats. Finally, our data demonstrated that there was a positive correlation between serum miR-30b levels and hepatic steatosis or homoeostasis model assessment of insulin resistance (HOMA-IR) in human subjects.

CONCLUSIONS

Our findings suggest that miR-30b represents not only a potential target for the treatment of insulin resistance, but also a non-invasive disease biomarker of NAFLD.

Diagnostic value of plasma miR-210 combined with serum tumor markers in pancreatic cancer

AIM: To evaluate the diagnostic value of the combination of plasma miR-210 with serum tumor markers in patients with pancreatic cancer.

METHODS: Sixty patients with pancreatic cancer, twenty patients with chronic pancreatitis, and ten normal people were included in the study. Total RNA was extracted from plasma samples for measurement of miR-210 levels using real-time PCR. Simultaneously, serum tumor markers carbohydrate antigen 199 (CA199), CA242 and carcino-embryonic antigen (CEA) were determined. The relationship between miR-210 levels and clinical characteristics of pancreatic cancer patients was analyzed. The diagnostic efficiency of combination of plasma miR-210 with serum tumor markers CA199, CA242, and CEA in pancreatic cancer patients was evaluated.

RESULTS: The relative abundance of plasma miR-210 was significantly higher in the pancreatic cancer group than in the chronic pancreatitis and normal groups (4.12 ± 4.51 vs 1.49 ± 3.94, -1.73 ± 4.82; P < 0.01 for both). Plasma miR-210 levels showed no significant correlation with CA199, CA242, CEA, tumor diameter, TNM stage or clinical stage in pancreatic cancer patients. Analysis using a binary logistic regression model showed that the diagnostic sensitivity and specificity of miR-210 alone were 96.7% and 50% for the pancreatic cancer group vs normal group, 95% and 25% for the pancreatic cancer group vs chronic pancreatitis group, and 86.7% and 40% for the pancreatic cancer group vs chronic pancreatitis and normal group. When plasma miR-210 was combined with serum tumor markers CA199, CA242, or CEA, the sensitivity and specificity in the three groups were 96.7% and 70%, 90% and 85%, 86.7% and 90%, respectively.

CONCLUSION: The combination of plasma miR-210 with serum tumor markers CA199, CA242 or CEA can improve diagnostic efficiency in patients with pancreatic cancer.

Effects of complete Freund's adjuvant on immunohistochemical distribution of IL-1beta and IL-1R I in neurons and glia cells of dorsal root ganglion

AIM

To investigate the effects of complete Freund adjuvant (CFA) on inflammatory hyperalgesia and morphological change of the coexistence of interleukin-1 beta (IL-1beta) and type I IL-1 receptor (IL-1RI) in neurons and glia cells of rat dorsal root ganglion (DRG).

METHODS

The pain-related parameters and the expression of IL-1RI and IL-1beta positive neurons and glia cells of DRG in normal saline (NS) and adjuvant-induced arthritic (AA) group were examined with pain behavior assessment methods and immunohistochemical assay, respectively.

RESULTS

Five hours, 1 d, and 2 d after intra-articular injection of 50 microL CFA, tactile hyperalgesia induced by CFA was observed in the foot flexion and extension scores of the ipsilateral hindpaw of AA group. Three days after injection, the distribution of IL-1RI/IL-1beta double-stained coexisted neurons and glia cells were observed in ipsilateral DRG of both groups. The number of IL-1beta positive neurons, IL-1RI positive neurons, IL-1beta/IL-1RI double-stained neurons, and IL-1RI positive glia cells in ipsilateral DRG of the AA group were higher than that of NS group (P<0.05 or P<0.01).

CONCLUSION

The coexistence of IL-1beta and IL-1RI in neurons and nonneuronal cells suggests an as yet unknown autocrine and/or paracrine function of IL-1beta in the DRG. The function was enhanced in articular arthritis induced by CFA and could play an important role in hyperalgesia under inflammatory conditions.

Prognostic indicators of survival in infants with congenital diaphragmatic hernia

PURPOSE

This study sought to identify the factors predictive of the short-term outcome in infants with congenital diaphragmatic hernia (CDH).

METHODS

We retrospectively reviewed medical records from September 1985 to December 1998 for all infants born with CDH and managed at National Taiwan University Hospital (NTUH). Coexisting pathology and measures of respiratory function were analyzed to determine the prognostic factors.

RESULTS

A total of 32 infants with CDH were managed at NTUH over the past 13 years. The investigated factors associated with poor prognosis in CDH included congenital heart disease, chromosomal abnormality, pneumothorax, and preoperative parameters including arterial partial carbon dioxide pressure greater than 40 mmHg, arterial partial oxygen pressure less than 100 mmHg, alveolo-arterial partial oxygen pressure greater than 610 mmHg, and oxygen index (OI) greater than 0.4. Multiple logistic regression analyses indicated that only an OI greater than 0.4 and pneumothorax were significant indicators of poor prognosis. When the incidence of pneumothorax was compared between patients who received ventilation using a conventional mechanical ventilator or high-frequency oscillatory ventilator (HFOV), a trend toward a lower incidence of pneumothorax in those using HFOV for initial stabilization was found (p = 0.08).

CONCLUSIONS

An OI greater than 0.4 before surgery and pneumothorax are poor prognostic indicators in infants with CDH. A high OI is reflective of the severity of pulmonary dysfunction in infants. Pneumothorax further compromises the dysfunction of a hypoplastic lung in infants with CDH. The results of this study show the importance of avoiding iatrogenic pneumothorax during management of infants with CDH.

Congenital diaphragmatic hernia misdiagnosed as pneumothorax in a newborn

Congenital diaphragmatic hernia (CDH) is usually left sided and has a large defect allowing abdominal viscera herniated into thoracic cavity. The chest films usually show air-filled stomach and/or loops of bowel in the ipsilateral hemithorax with mediastinal shift. We report a newborn with CDH, presenting as hyperlucent hemithorax, right-shifted mediastinum, apparently normal pattern of abdominal bowel gas, with the tip of nasogastric tube below the left hemidiaphragm on the radiograph. It was initially misdiagnosed as pneumothorax, and the acute respiratory distress was temporarily relieved by needle aspiration. Hyperlucent hemithorax due to intrathoracic gastric dilatation alone is an unusual presentation of CDH in neonatal period. Absence of stomach bubble in the left upper quadrant of the abdomen, in both radiography and abdominal sonography, is an important clue to make diagnosis of CDH in this misleading condition.

Brief perinatal hypoxia increases severity of pulmonary hypertension after reexposure to hypoxia in infant rats

We hypothesized that disrupted alveolarization and lung vascular growth caused by brief perinatal hypoxia would predispose infant rats to higher risk for developing pulmonary hypertension when reexposed to hypoxia. Pregnant rats were exposed to 11% inspired oxygen fraction (barometric pressure, 410 mmHg; inspired oxygen pressure, 76 mmHg) for 3 days before birth and were maintained in hypoxia for 3 days after birth. Control rats were born and raised in room air. At 2 wk of age, rats from both groups were exposed to hypoxia for 1 wk or kept in room air. We found that brief perinatal hypoxia resulted in a greater increase in right ventricular systolic pressure and higher ratio of right ventricle to left ventricle plus septum weights after reexposure to hypoxia after 2 wk of age. Moreover, perinatal hypoxic rats had decreased radial alveolar counts and reduced pulmonary artery density. We conclude that brief perinatal hypoxia increases the severity of pulmonary hypertension when rats are reexposed to hypoxia. We speculate that disrupted alveolarization and lung vascular growth following brief perinatal hypoxia may increase the risk for severe pulmonary hypertension with exposure to adverse stimuli later in life.

Cyanotic congenital heart disease and necrotizing enterocolitis: report of three cases

Three infants with cyanotic congenital heart diseases (CCHD) had abdominal distension, poor activity at day 2, day 3, and day 23. The abdominal roentgenograms showed dilated bowel loops, pneumatosis intestinalis, and pneumoperitoneum. Necrotizing enterocolitis (NEC) was diagnosed. After medical and surgical intervention, one infant survived. In this report, we discuss the relationship between CCHD and NEC. The possible risk factors were also discussed, and it is recommended that NEC be a considered significant complication of infants with CCHD.

Granulocyte colony-stimulating factor in the cord blood of premature neonates born to mothers with pregnancy-induced hypertension

OBJECTIVES

To estimate the cord blood levels of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in preterm infants and to study the relationship of these levels to pregnancy-induced hypertension (PIH) and absolute neutrophil counts.

STUDY DESIGN

G-CSF and GM-CSF levels in the cord blood of preterm neonates (n = 74) either with or without maternal PIH were estimated by enzyme-linked immunosorbent assay.

RESULTS

Infants in the PIH group had lower white blood cell, absolute neutrophil, absolute lymphocyte, and monocyte counts. The levels of G-CSF in cord blood were significantly lower in infants whose mothers had PIH (P =.04) and in infants with neutropenia (P =. 01). G-CSF levels were positively correlated with both absolute neutrophil count (P =.02) and total white blood cell count (P =.01). GM-CSF was undetectable in all subjects. According to logistic regression with neutropenia as the dependent variable, only maternal PIH (P <.001), gestational age (P <.001), and G-CSF (P =.01) were independently related.

CONCLUSION

In this study maternal PIH and low gestational age were significantly associated with neutropenia in premature infants. Low G-CSF levels may contribute to the neutropenia that is commonly seen in infants born to mothers with PIH.

Longitudinal study of serum free thyroxine and thyrotropin levels by chemiluminescent immunoassay during infancy

From October 1996 to December 1997, ninety normal infants born at full-term were enrolled in this study. There were 59 female infants and 31 male infants. Both serum free thyroxine and thyrotropin levels were measured by chemiluminescent immunoassay in the first week (n = 75), 3 months (n = 66), 6 months (n = 79), and 12 months (n = 77) of age. Serum free thyroxine levels (ng/dL) (mean +/- standard deviation) were 2.2 +/- 0.5, 1.3 +/- 0.2, 1.2 +/- 0.2, 1.0 +/- 0.2 for each age group, respectively. Serum thyrotropin levels (mIU/L) (mean +/- standard deviation) were 9.7 +/- 6.7, 3.0 +/- 1.6, 2.7 +/- 1.3, 2.5 +/- 1.2 for each age group, respectively. There was no significant difference between the levels of these two parameters between male and female. The present study provides the reference data for the normal range of thyroid function during infancy. Our results also show that the serum free T4 and TSH levels tend to decline during the first year of life.

Hepatitis B surface antigenemia at birth: a long-term follow-up study

OBJECTIVE

To investigate the prevalence and outcome of hepatitis B surface antigenemia in newborns of hepatitis B e antigen (HBeAg)-positive hepatitis B surface antigen (HBsAg) carrier mothers under the current immunoprophylaxis program.

STUDY DESIGN

From 1984 to 1993, 665 high-risk newborns born to HBeAg-positive HBsAg carrier mothers were prospectively recruited. The newborns were tested for HBsAg soon after birth, before hepatitis B immune globulin administration. All newborns received hepatitis B immune globulin within 24 hours after birth plus subsequent hepatitis B vaccination. Those who were seropositive for HBsAg at birth were regularly followed up for their hepatitis B virus (HBV) markers, liver function profiles, and alpha-fetoprotein levels from 1984 to 1996.

RESULTS

Sixteen (2.4%) of the 665 subjects were found to be seropositive for HBsAg at birth, and all remained HBsAg-positive at 6 months of age. Twelve of the 16 received long-term follow-up care, and all were confirmed to have chronic HBV infection. Of the 12, 2 had HBeAg seroconversion, and 1 had alanine aminotransferase flares without HBeAg seroconversion. Delayed appearance of hepatitis B core antibody (anti-HBc) occurred in 2 without alanine aminotransferase elevation.

CONCLUSIONS

Current immunoprophylaxis strategy does not protect newborns with surface antigenemia, apparently acquired in utero, from becoming HBV carriers. Immunologic attempts to eliminate HBV may occur in carrier children infected in utero, despite their profound immune tolerance to HBV.

Early outcome of extremely low birth weight infants in Taiwan

We retrospectively evaluated the outcome and the risk factors for mortality among extremely low birth weight (ELBW) infants born at National Taiwan University Hospital. The records of all live-born infants with body birth weight of less than 1,000 g from January 1, 1993, to December 31, 1996, were evaluated. Infants with major anomalies or whose parents refused resuscitation were excluded from the analysis. There were 81 ELBW infants (0.59%) among a total of 13,835 live births during the study period, and 73 cases were enrolled for study. The mean gestational age (GA) was 27.2 (range, 24-34) weeks. Sixty-six percent of the ELBW infants were born by cesarean delivery. Respiratory distress syndrome occurred in 64% of infants and exogenous surfactant therapy was given to 47%, while intermittent mandatory ventilation was given to 85%. Symptomatic patent ductus arteriosus occurred in 34% of infants, septicemia in 30%, chronic lung disease in 48%, grade III to IV intraventricular hemorrhage in 27%, stage III to V retinopathy of prematurity in 33%, and necrotizing enterocolitis in 8%. Neonatal survival was 74%, survival to discharge was 60%, and intact survival was 50%. The survival rate was 40% for infants with a birth body of weight less than or equal to 750 g, and 68% for those with a birth body weight of greater than 750 g. While survival was 27% for infants with a GA of less than 26 weeks, it was 75% for those with a GA of greater than or equal to 26 weeks. The survival rate improved year by year for those with a GA less than 28 weeks. Cox regression analysis of survival showed that Apgar score at 1 minute (p = 0.0063), pulmonary hypertension (p = 0.012), and severe intraventricular hemorrhage (p = 0.0031) were the most important factors associated with mortality. Though the outcome of ELBW infants in our institute seems poorer than in some more developed countries, it is improving. The prognosis for ELBW infants of 24 to 25 weeks' GA remains guarded under our present care.

Comparison of the outcome of extremely-low-birth-weight infants between two periods

A comparison was made of the outcome of 73 neonates born with their birth weight of 500-999 gm in National Taiwan University Hospital during the period between January 1, 1993 and December 31, 1996 (Period II), with the outcome of 21 such neonates born between April 1, 1988 and October 31, 1992 (Period I). Exclusion criteria included parental refusal for resuscitation, and major anomalies. Data were collected via a predetermined record sheet. The incidences of the extremely-low-birth-weight infants were 23/10,173 (0.23%) and 81/13,835 (0.59%) in Periods I and II, respectively. Early neonatal mortality rate was significant decreased in Period II (43% versus 14%). The limit of viability was improved from gestational age of 26 weeks or 700 gm to gestational age of 24 weeks or 600 gm. The incidence of neonatal morbidity (80% versus 50%) and total survival rate (48% versus 60%) have not changed significantly as seen in this limited number of cases. This study concluded that, with the introduction of exogenous surfactant and modern neonatal care, early neonatal survival rate and the limit of viability were improved.

Factors associated with high-frequency oscillatory ventilation response in infants with respiratory failure

A prospective, clinical study was conducted to investigate the factors associated with the effectiveness and outcome of high-frequency oscillatory ventilation (HFOV) in infants with respiratory failure unresponsive to optimal conventional respiratory and pharmacological therapy. A high-lung volume strategy was used in cases with diffuse lung disease. A total of 30 treatments in 24 patients (including 14 premature infants), aged 1 to 127 days, was included for analysis. By 6 to 8 hours, > 20% improvement in oxygenation (good response) was noted in 57% of treatments. < 20% improvement (poor response) in 20%, 23% showed delayed response 10 to 24 hours after initiation of HFOV. Thirty-five percent of treatments with initial good response deteriorated later because of severe underlying problems or occurrence of ventilatory complications. Seventeen treatments (57%) were weaned successfully to conventional mechanical ventilation (CMV). Poor response was associated with a higher oxygenation index prior to HFOV and a severe underlying problem. Failure to be successfully weaned to CMV was associated with a higher mean airway pressure and a severe underlying condition. Premature infants and infants with the persistent pulmonary hypertension of newborn usually had a good response to HFOV. From results of this study, it is concluded that patients with severe lung disease and a severe underlying problem responded poorly to HFOV. An initial good response did not predict successful weaning.

Etiology and outcome of hydrops fetalis

Hydrops fetalis is a morbid condition caused by a wide variety of diseases. Although treatment for some underlying pathologies is becoming available, the prognosis remains poor. To analyze the etiology and outcome of hydrops fetalis, we reviewed the records of 79 fetuses encountered at the National Taiwan University Hospital between January 1993 and October 1996. The mean +/- standard deviation gestational age at presentation was 24.9 +/- 6.3 weeks. One case was due to RhE incompatibility. Seventy-eight fetuses were diagnosed as having nonimmune hydrops fetalis; this was idiopathic in 20 fetuses. In the other 58, the causes and associated conditions were classified into eight groups: hematologic (25), cardiovascular (15), chromosomal (5), gastrointestinal (4), cystic hygroma (3), pulmonary (2), infection (2), and miscellaneous (3). One fetus with cystic hygroma also had a chromosomal abnormality (Turner's syndrome). The most common cause of nonimmune hydrops fetalis was homozygous alpha-thalassemia (31%). Twenty-nine fetuses were lost to follow-up after initial evaluation and 50 fetuses were delivered at our hospital. Of these, there were eight cases of antepartum death, 24 cases of intrapartum death, and 18 live births. Seventeen of the live-born infants were treated at our neonatal intensive care unit, of whom only seven survived.

High-frequency oscillatory ventilation for infants and children with adult respiratory distress syndrome

Two infants and two children suffered from severe hypoxemia, presenting as a ratio of arterial to alveolar PaO2 < 0.1, persisting for more than 3 hours in spite of high settings on conventional mechanical ventilator. Adult respiratory distress syndrome was diagnosed with the support of bilateral diffuse haziness on chest radiographs. High-frequency oscillatory ventilation with high-lung-volume strategy resulted in prompt decrease in oxygenation index and increase in ratio of arterial to alveolar P O2 in three (75%) of the 4 patients within 6 hours. After a mean duration of 96 hours, high-frequency oscillatory ventilation could be weaned off and conventional ventilation could be resumed at lower mean airway pressure in 3 patients. They continued to improve and finally recovered. The other one showed initially steady improvement on high-frequency oscillatory ventilation for 20 hours, but ultimately died of unresolved cytomegalovirus pneumonitis and intractable pulmonary hemorrhage. There were 2 episodes of pneumothorax developing during high-frequency oscillatory ventilation. After decreasing mean airway pressure and amplitude, the airleak resolved with chest tube insertion. We conclude that high-frequency oscillatory ventilation with high-lung-volume strategy may be an effective rescue therapy to relieve profound hypoxemia in infants and children with adult respiratory distress syndrome.

Hydrops fetalis due to placental chorioangioma: report of one case

Chorioangioma is the most common tumor of the placenta. However, a large one complicated with hydrops fetalis is rare. We report a patient who had hydrops fetalis associated with placental chorioangioma. The clinical manifestations included generalized edema, coagulopathy, thrombocytopenia, anemia, hypoproteinemia and hepatosplenomegaly. The hospital course was complicated with acute renal failure and repeated pneumonia. The patient died on the 54th day of life due to persistent lung atelectasis and hypovolemic shock. The pathophysiology and management of the complications of hydrops fetalis with chorioangioma are discussed.

Clinical relevance of the detection of hepatitis delta virus RNA in serum by RNA hybridization and polymerase chain reaction

Hepatitis delta virus nucleic acid was detected by dot-blot hybridization using RNA probe and reverse transcription/polymerase chain reaction amplification in 223 serum samples from 66 patients with hepatitis D virus infection. Seven cases with chronic hepatitis D virus infection were treated with interferon: six for 3 months and one for 7.5 years. By using the primers located in the putative conserved regions, the technique of reverse transcription/polymerase chain reaction amplification was 10(3) to 10(4) times more sensitive than that of dot-blot hybridization. The main findings of this study are: (i) HDV RNA could be detected in the absence of any other serological hepatitis D virus marker in serum from acute hepatitis patients with IgM anti-HBc; (ii) high titer anti-HD antibodies (IgM and total anti-HD) persisted in patients during short-term interferon treatment, and in one patient during long-term interferon treatment, despite clearance of serum HDV RNA even after 3 years; (iii) total anti-HD alone was detected in the absence of IgM anti-HD and serum HDV RNA. These observations indicate that the detection of HDV RNA by molecular techniques in serum is a useful, sensitive and non-invasive technique for the early diagnosis and follow up of hepatitis D virus infection, as well as for the monitoring of antiviral therapy. In addition, total anti-HD antibody in the absence of HDV RNA may be the only residual marker of past infection. Finally, the choice of the technique for hepatitis D virus detection is important for the optimal assessment of the clinical stage and monitoring of antiviral therapy in hepatitis D virus-infected patients.

Detection of small and large genomes of hepatitis D virus in serum of patients with hepatitis D

By combining the polymerase chain reaction (PCR) with restriction enzyme digestion technologies, we characterized the genomes for the small and large delta proteins of HDV in retrospective analysis of sera from 10 patients with varied clinical outcomes. Both small and large genomes of HDV were present in all 13 serum samples from the 6 acute and 4 chronic cases studied, while the specific HDV proteins (P24 and P27) could be detected by immunoblot analysis in only 4 of them. The relative amounts and ratios of the genomes for the large and the small proteins of HDV were different for each individual. The molecular ratio of large to small HDV genomes in serum correlated with viral replication. When the replication of HDV RNA increased, the ratio decreased and vice-versa. No specific correlation, however, was found between the ratio of both molecular forms and the clinical outcome.

Discovery of a novel point mutation changing the HDAg expression of a hepatitis delta virus isolate from Central African Republic

None of the mutations so far discovered in several hepatitis delta virus (HDV) isolates appears to determine important changes in HDV specific protein (HDAg) expression, except for a putative mutation at nucleotide 1012 converting an amber stop codon (TAG) to a codon for tryptophan (TGG). Here we present the characterization of an HDV obtained from the liver of a woodchuck inoculated with sera from fulminant HDV patients in Central African Republic (CAR). By restriction enzyme analysis and sequencing of HDAg-coding region cDNA clones, we found that this HDV isolate bears a novel mutation (T to A) at nucleotide 1013 which converts the amber stop codon (TAG) to a codon for lysine (AAG). Comparison of these nucleotide sequences with those available from American, Japanese, Taiwanese, French, Italian and Nauru isolates showed a variability of 1.7 to 21.5% and 1.9 to 28.7% at the nucleic acid and amino acid levels, respectively. The HDAg-encoding sequence of the CAR isolate is closely related to that of the Italian HDV isolate. The in vitro expression of this HDV isolate resulted in a unique HDAg species (28K) which was identical with that characterized in vivo.