No evidence of ongoing HIV replication or compartmentalization in tissues during combination antiretroviral therapy: Implications for HIV eradication.

HIV persistence during combination antiretroviral therapy (cART) is the principal obstacle to cure. Mechanisms responsible for persistence remain uncertain; infections may be maintained by persistence and clonal expansion of infected cells or by ongoing replication in anatomic locations with poor antiretroviral penetration. These mechanisms require different strategies for eradication, and determining their contributions to HIV persistence is essential. We used phylogenetic approaches to investigate, at the DNA level, HIV populations in blood, lymphoid, and other infected tissues obtained at colonoscopy or autopsy in individuals who were on cART for 8 to 16 years. We found no evidence of ongoing replication or compartmentalization of HIV; we did detect clonal expansion of infected cells that were present before cART. Long-term persistence, and not ongoing replication, is primarily responsible for maintaining HIV. HIV-infected cells present when cART is initiated represent the only identifiable source of persistence and is the appropriate focus for eradication.

Peripartum cardiomyopathy.

Peripartum cardiomyopathy (PPCM) is a rare and potentially life-threatening disease that occurs toward the end of pregnancy or in the months following delivery in previously heart-healthy women. The incidence varies widely depending on geographical region and ethnic background, with an estimated number of 1 in 1000-1500 pregnancies in Germany. The course of the disease ranges from mild forms with minor symptoms to severe forms with acute heart failure and cardiogenic shock. The understanding of the etiology of PPCM has evolved in recent years. An oxidative stress-mediated cleaved 16-kDa fragment of the nursing hormone prolactin is thought to damage endothelial cells and cardiomyocytes. Bromocriptine, a dopamine-receptor agonist, effectively blocks prolactin release from the pituitary gland. In addition to standard heart failure therapy, this disease-specific treatment reduces morbidity and mortality in PPCM patients. This review summarizes the current knowledge on PPCM and the disease-specific treatment options.

Bone marrow failure and extramedullary hematopoiesis in McCune-Albright syndrome.

In fibrous dysplasia/McCune-Albright syndrome (FD/MAS), bone and bone marrow are, to varying degrees, replaced by fibro-osseous tissue typically devoid of hematopoietic marrow. Despite the extensive marrow replacement in severely affected patients, bone marrow failure is not commonly associated with FD/MAS. We present a 14-year-old girl with FD/MAS, who developed pancytopenia and extramedullary hematopoiesis (EMH) with no identified cause, in the setting of iatrogenic thyrotoxicosis and hyperparathyroidism. Pancytopenia, requiring monthly blood transfusions, persisted despite multiple strategies to correct these endocrinopathies. Due to worsening painful splenomegaly, likely as a result of sequestration, splenectomy was performed. Following splenectomy, pancytopenia resolved and patient has since been transfusion-independent. We report the first detailed case of bone marrow failure and EMH in FD/MAS. The etiology of marrow failure is likely multifactorial and related to the loss of marrow reserve due to extensive polyostotic FD, exacerbated by iatrogenic thyrotoxicosis and hyperparathyroidism. Mini Abstract: A patient with fibrous dysplasia developed bone marrow failure and extramedullary hematopoiesis. The etiology likely involved loss of hematopoetic marrow space and uncontrolled endocrinopathies. Splenectomy was therapeutic.

Complications of percutaneous liver biopsy with Klatskin needles: a 36-year single-centre experience.

BACKGROUND: Liver biopsy is the gold standard in evaluating liver diseases but is susceptible to complications. Safety data on aspiration needle biopsies remain limited. AIM: To evaluate the safety of percutaneous liver biopsy performed with Klatskin needle. METHODS: Clinical and biochemical data were retrospectively retrieved from sequential subjects who underwent liver biopsy with Klatskin needle from 1978 to 2015. Subjects with complications underwent thorough chart reviews for hospital course. RESULTS: Of 3357 biopsies performed, complications occurred in 135 (4%) biopsies with 33 (1%) resulting in major complications. Severe pain occurred in 78 (2.3%) subjects and bleeding occurred in 21 (0.6%) subjects. Biliary injury occurred in 8 (0.2%) biopsies. Three subjects died as a result of massive intraperitoneal bleeding. Compared to viral hepatitis, biopsies performed with certain diagnosis had significantly higher odds of major complications: NRH (OR: 17), DILI (OR: 20), GVHD (OR: 32) and HCC (OR: 34). Subjects with major complications had higher pre-biopsy median AP (153 vs. 78 U/L, P < 0.001), ALT (105 vs. 64 U/L, P < 0.05), AST (62 vs. 47 U/L, P < 0.02), along with marginally lower total bilirubin (1.0 vs. 0.7 mg/dL, P < 0.01) and albumin (3.7 vs. 4.0 g/dL, P < 0.001). By multivariate backward logistic regression, platelets ≤100 K/µL and aPTT >35 were independent risk factors of post-biopsy bleeding. CONCLUSION: Klatskin needle liver biopsies are safe with rare procedural morbidity. Our data suggests certain acutely ill subjects and those with systemic illnesses may be at higher risk of major complications. Clinicians should weigh the risks and benefits of liver biopsy in these patients with other alternative approaches.

Endoluminal Vacuum Therapy for Ivor Lewis Anastomotic Leaks: A Pilot Study in a Swine Model.

Anastomotic leaks are a serious complication associated with Ivor Lewis esophagectomies. Endoluminal negative pressure vacuum devices create a possible treatment alternative to conventional surgical intervention. Ten pigs had an intrathoracic esophageal anastomosis with a 1-cm defect. The experimental group had the device placed intraoperatively across the defect, whereas the control group did not. Once treatment was completed, a contrast fluoroscopic study and necropsy was performed. All control pigs had contrast extravasation on fluoroscopy and contamination on necropsy. The experimental group had no radiologic leak and no contamination on necropsy. The P value for leak is 0.03. This study demonstrated that endoluminal negative pressure vacuum therapy is tolerated in the swine model and is successful in facilitating the healing of anastomotic leaks. Endoluminal negative pressure vacuum therapy has potential clinical benefits, including decreased morbidity and length of hospital stay.

Noninvasive markers for staging fibrosis in chronic delta hepatitis.

BACKGROUND: Serum fibrosis markers are useful in staging chronic hepatitis B (HBV) and C (HCV) virus but have not been evaluated in chronic hepatitis D virus (HDV). AIM: To evaluate the utility of serum fibrosis markers [fibrosis-4 score (FIB-4), aspartate aminotransferase (AST) to alanine aminotransferase (ALT) ratio, aspartate aminotransferase ratio (AAR), age-platelet index (API), AST-to-platelet-ratio-index (APRI) and Hui score] in HDV infection. METHODS: Clinical and histologic laboratory data from HBV, HCV and HDV patients were evaluated and serum fibrosis markers were calculated. The ability of fibrosis markers to detect advanced fibrosis (Ishak ≥4) and cirrhosis (Ishak = 6) were evaluated and compared between viral infections. RESULTS: A total of 1003 subjects (HCV = 701, HBV = 240 and HDV = 62) with mean age of 46 ± 11 and 66% male were evaluated. HDV subjects had higher ALT and AST than HCV and lower platelets than both HBV and HCV. Histologically, HDV had the greatest percentage of Ishak ≥4 and necroinflammation. FIB-4 performed best in detecting advanced fibrosis and cirrhosis in all viral cohorts. In HDV, area under the receiver operator curve (AUROC) 95% confidence intervals for detecting advanced fibrosis were: FIB-4 = 0.70 (0.55-0.84), API = 0.69 (0.55-0.82), APRI = 0.68 (0.54-0.82), Hui score = 0.63 (0.49-0.78), AAR = 0.63 (0.48-0.77). The AUROC for detecting cirrhosis in HDV were: FIB-4 = 0.83 (0.69-0.97), API = 0.80 (0.66-0.95), APRI = 0.75 (0.61-0.89), Hui score = 0.70 (0.49-0.91) and AAR = 0.70 (0.48-0.93). Adjustment of published cut-offs led to marginal improvements in FIB4 for advanced fibrosis and of APRI for cirrhosis in HDV. CONCLUSIONS: Serum fibrosis markers have lower performance accuracy in chronic HDV infected patients compared to HBV and HCV patients. Other noninvasive fibrosis markers should be explored to assist in the management of these patients.

A phase II study of TRC105 in patients with hepatocellular carcinoma who have progressed on sorafenib.

BACKGROUND: Endoglin is an endothelial cell membrane receptor essential for angiogenesis and highly expressed on the vasculature of many tumor types, including hepatocellular carcinoma (HCC). TRC105 is a chimeric IgG1 anti-CD105 monoclonal antibody that inhibits angiogenesis and tumor growth by endothelial cell growth inhibition, ADCC and apoptosis, and complements VEGF inhibitors. OBJECTIVE: The aim of this phase II study was to evaluate the efficacy of anti-endoglin therapy with TRC105 in patients with advanced HCC, post-sorafenib. METHODS: Patients with HCC and compensated liver function (Childs-Pugh A/B7), ECOG 0/1, were enrolled to a single-arm, phase II study of TRC105 15 mg/kg IV every two weeks. Patients must have progressed on or been intolerant of prior sorafenib. A Simon optimal two-stage design was employed with a 50% four-month PFS target for progression to the second stage. Correlative biomarkers evaluated included DCE-MRI as well as plasma levels of angiogenic biomarkers and soluble CD105. RESULTS: A total accrual of 27 patients was planned. However, because of lack of efficacy and in accordance with the Simon two-stage design, 11 patients were enrolled. There were no grade 3/4 treatment-related toxicities. Most frequent toxicities were headache (G2; N = 3) and epistaxis (G1; N = 4). One patient had a confirmed partial response by standard RECIST criteria and biologic response on DCE-MRI but the four-month PFS was insufficient to proceed to the second stage of the study. CONCLUSIONS: TRC105 was well tolerated in this HCC population following sorafenib. Although there was evidence of clinical activity, this did not meet prespecified criteria to proceed to the second stage. TRC105 development in HCC continues as combination therapy with sorafenib.

Liver injury is associated with mortality in sickle cell disease.

BACKGROUND: Increased life expectancy in sickle cell disease (SCD) has resulted in greater recognition of the consequences of repeated intravascular vaso-occlusion and chronic haemolysis to multiple organ systems. AIM: To report the long-term consequences of liver dysfunction in SCD. METHODS: A cohort of SCD patients was prospectively evaluated at the National Institutes of Health (NIH) Clinical Center. The association of mortality with liver enzymes, parameters of liver synthetic function and iron overload was evaluated using Cox regression. RESULTS: Exactly, 247 SCD patients were followed up for 30 months of whom 22 (9%) died. After controlling for predictors, increased direct bilirubin (DB), ferritin, alkaline phosphatase and decreased albumin were independently associated with mortality. In a multivariable model, only high DB and ferritin remained significant. Ferritin correlated with hepatic iron content and total blood transfusions but not haemolysis markers. Forty patients underwent liver biopsies and 11 (28%) had fibrosis. Twelve of 26 patients (48%) had portal hypertension by hepatic venous pressure gradient (HVPG) measurements. All patients with advanced liver fibrosis had iron overload; however, most patients (69%) with iron overload were without significant hepatic fibrosis. Ferritin did not correlate with left ventricular dysfunction by echocardiography. DB correlated with bile acid levels suggesting liver pathology. Platelet count and soluble CD14 correlated with HVPG indicating portal hypertension. CONCLUSIONS: Ferritin and direct bilirubin are independently associated with mortality in sickle cell disease. Ferritin likely relates to transfusional iron overload, while direct bilirubin suggests impairment of hepatic function, possibly impairing patients' ability to tolerate systemic insults.

Comparative analysis of portal hepatic infiltrating leucocytes in acute drug-induced liver injury, idiopathic autoimmune and viral hepatitis.

Drug-induced liver injury (DILI) is often caused by innate and adaptive host immune responses. Characterization of inflammatory infiltrates in the liver may improve understanding of the underlying pathogenesis of DILI. This study aimed to enumerate and characterize leucocytes infiltrating liver tissue from subjects with acute DILI (n = 32) versus non-DILI causes of acute liver injury (n = 25). Immunostains for CD11b/CD4 (Kupffer and T helper cells), CD3/CD20 (T and B cells) and CD8/CD56 [T cytotoxic and natural killer (NK) cells] were evaluated in biopsies from subjects with acute DILI, either immunoallergic (IAD) or autoimmune (AID) and idiopathic autoimmune (AIH) and viral hepatitis (VH) and correlated with clinical and pathological features. All biopsies showed numerous CD8(+) T cells and macrophages. DILI cases had significantly fewer B lymphocytes than AIH and VH and significantly fewer NK cells than VH. Prominent plasma cells were unusual in IAD (three of 10 cases), but were associated strongly with AIH (eight of nine) and also observed in most with AID (six of nine). They were also found in five of 10 cases with VH. Liver biopsies from subjects with DILI were characterized by low counts of mature B cells and NK cells in portal triads in contrast to VH. NK cells were found only in cases of VH, whereas AIH and VH both showed higher counts of B cells than DILI. Plasma cells were associated most strongly with AIH and less so with AID, but were uncommon in IAD.

Long-term therapy of chronic delta hepatitis with peginterferon alfa.

BACKGROUND: Chronic delta hepatitis virus (HDV) infection rapidly progresses to cirrhosis. Treatment with peginterferon for up to 2 years is often without durable response. AIM: To examine the efficacy and safety of long-term peginterferon in achieving a durable response. METHODS: Treatment was initiated with 180 µg/week of peginterferon alfa-2a with titration to a maximal tolerable dose, for up to 5 years. Liver biopsies and hepatic venous pressure gradients (HVPG) were evaluated at baseline, 1, 3 and 5 years. The primary endpoint was histological improvement or loss of serum HDV and HBsAg at 3 years. RESULTS: Thirteen patients were treated for a median of 140 weeks (6-260) with an average peginterferon dose of 180 µg/week (90-270). At baseline, most had advanced disease (median Ishak fibrosis = 3) with portal hypertension (HVPG = 10.2 ± 6 mmHg). Five of 13 patients (39%) achieved the primary endpoint, with three seroconverting for HBsAg after 24, 37 and 202 weeks of treatment. Histological inflammation improved after 1 year, (median HAI: 10 vs. 7, P = 0.01) with persistence in 4/5 patients at 3 years (median HAI: 7.5). Greatest improvements occurred in the first year. Baseline bilirubin and HBsAg levels were significantly lower in virological responders than nonresponders. After 12 weeks, virological responders had a significant decline in HBsAg (1.5 log10 IU/mL, P = 0.05). CONCLUSION: Despite increased doses and duration of therapy, treatment of chronic HDV with peginterferon remains unsatisfactory. Quantitative measures of HBsAg may be an important biomarker of early response to peginterferon therapy in chronic delta hepatitis virus infection.

Differential expression of miR-17~92 identifies BCL2 as a therapeutic target in BCR-ABL-positive B-lineage acute lymphoblastic leukemia.

Despite advances in allogeneic stem cell transplantation, BCR-ABL-positive acute lymphoblastic leukaemia (ALL) remains a high-risk disease, necessitating the development of novel treatment strategies. As the known oncomir, miR-17~92, is regulated by BCR-ABL fusion in chronic myeloid leukaemia, we investigated its role in BCR-ABL translocated ALL. miR-17~92-encoded miRNAs were significantly less abundant in BCR-ABL-positive as compared to -negative ALL-cells and overexpression of miR-17~19b triggered apoptosis in a BCR-ABL-dependent manner. Stable isotope labelling of amino acids in culture (SILAC) followed by liquid chromatography and mass spectroscopy (LC-MS) identified several apoptosis-related proteins including Bcl2 as potential targets of miR-17~19b. We validated Bcl2 as a direct target of this miRNA cluster in mice and humans, and, similar to miR-17~19b overexpression, Bcl2-specific RNAi strongly induced apoptosis in BCR-ABL-positive cells. Furthermore, BCR-ABL-positive human ALL cell lines were more sensitive to pharmacological BCL2 inhibition than negative ones. Finally, in a xenograft model using patient-derived leukaemic blasts, real-time, in vivo imaging confirmed pharmacological inhibition of BCL2 as a new therapeutic strategy in BCR-ABL-positive ALL. These data demonstrate the role of miR-17~92 in regulation of apoptosis, and identify BCL2 as a therapeutic target of particular relevance in BCR-ABL-positive ALL.

Vitamin E and changes in serum alanine aminotransferase levels in patients with non-alcoholic steatohepatitis.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is a common cause of serum alanine aminotransferase (ALT) elevations and chronic liver disease, but it is unclear how well ALT elevations reflect the liver injury. AIM: To assess how well changes in ALT elevations reflect improvements in liver histology in response to vitamin E therapy. METHODS: The vitamin E and placebo arms of the Pioglitazone vs. Vitamin E vs. Placebo in Non-alcoholic Steatohepatitis (PIVENS) trial were reassessed for associations among changes in ALT levels, body weight and liver histology. An ALT response was defined as a decrease to ≤40 U/L and by ≥30% of baseline. Liver biopsies taken before and after treatment were scored for non-alcoholic fatty liver disease activity (NAS) and fibrosis. RESULTS: ALT responses were more frequent among vitamin E (48%) than placebo (16%) recipients (P < 0.001). Among vitamin E recipients, ALT responses were associated with decreases in NAS (P < 0.001), but not fibrosis scores (P = 0.34), whereas among placebo recipients, ALT responses were associated with significant decreases in both (P < 0.05). Weight loss (≥2 kg) was also associated with ALT response (P < 0.001), improvements in NAS (P < 0.001) and fibrosis (P < 0.02), but vitamin E had an added effect both with and without weight loss. Weight gain (≥2 kg) was associated with lack of ALT response and worsening NAS and fibrosis scores in patients not on vitamin E. CONCLUSIONS: Decrease of ALT levels to normal in patients with NASH is usually associated with improved histological activity. Management should stress the value of weight loss and strongly discourage weight gain. Vitamin E can improve both ALT levels and histology with and without weight loss. CLINICAL TRIAL NUMBER: NCT00063622.

Long-term outcome of chronic hepatitis C after sustained virological response to interferon-based therapy.

BACKGROUND: Although the short-term benefits of a sustained virological response (SVR) to interferon-based therapies of chronic hepatitis C (CHC) are well known, the long-term consequences of SVR are less clear. AIM: To assess changes in markers of disease activity and fibrosis in patients followed up to 23 years post-SVR. METHODS: The first 103 SVR patients (from 1984 to 2003) at the National Institutes of Health Clinical Center were evaluated. Serum markers before treatment and at the last visit were compared. Evaluations after 2007 included transient elastography (TE). RESULTS: Of 103 patients, three subsequently relapsed 0.7, 6.3 and 6.5 years post therapy. The remaining 100 patients (56 men, mean age 56 years) maintained SVR at final follow-up. No patients developed hepatic decompensation, but one with pre-treatment cirrhosis died 12 years post SVR of hepatocellular carcinoma. In comparison to pre-treatment values, markers improved at follow-up, including mean ALT (152-27 U/L), AST (87-24 U/L), alkaline phosphatase (78-69 U/L), IgG (1463-1113 mg/dL), platelet count (209 000-239 000/µL) and AST to platelet count ratio index (APRI: 1.31-0.33). TE was performed in 69 patients and was normal (<7.0 kPA) in 60%, moderately elevated (7.1-13.8) in 31% and cirrhotic range (>13.8) in 9%. TE and platelet counts at follow-up correlated with fibrosis on pre-treatment liver biopsy (P < 0.001). CONCLUSIONS: In 97% of patients with CHC, SVR is durable without evidence of disease progression, although some degree of hepatic fibrosis may persist and patients with pre-treatment cirrhosis are at continuing low risk for hepatocellular carcinoma.

Renal tubular dysfunction during long-term adefovir or tenofovir therapy in chronic hepatitis B.

BACKGROUND: Adefovir and tenofovir are nucleotide analogues used as long-term therapy of chronic hepatitis B. Side effects are few, but prolonged and high-dose therapy has been associated with proximal renal tubular dysfunction (RTD). AIM: To assess the incidence of RTD during long-term nucleotide therapy of chronic hepatitis B. METHODS: A total of 51 patients being treated at the Clinical Center, National Institutes of Health were studied. Diagnosis of RTD required de novo appearance of at least three of five features: hypophosphataemia, hypouricaemia, serum creatinine elevation, proteinuria or glucosuria. RESULTS: Among 51 patients treated for 1-10 (mean 7.4) years with adefovir (n = 42), tenofovir (n = 4) or adefovir followed by tenofovir (n = 5), 7 (14%) developed RTD. Time to onset ranged from 22 to 94 (mean 49) months with an estimated 10-year cumulative rate of 15%. All seven had low urinary percent maximal tubular reabsorption of phosphate (<82%). Patients with RTD were older (58 vs. 44 years; P = 0.01) and had lower baseline glomerular filtration rates (82 vs. 97 cc/min; P = 0.08) compared to those without; but did not differ in other features. Six patients with RTD were switched to entecavir, all subsequently had improvements in serum phosphate (2.0-3.0 mg/dL), creatinine (1.6-1.1 mg/dL), uric acid (2.7-3.8 mg/dL) and proteinuria. CONCLUSIONS: Renal tubular dysfunction develops in 15% of patients treated with adefovir or tenofovir for 2-9 years and is partially reversible with change to other antivirals. Monitoring for serum phosphate, creatinine and urinalysis is prudent during long-term adefovir and tenofovir therapy.

Randomised clinical trial: the benefit of combination therapy with adefovir and lamivudine for chronic hepatitis B.

BACKGROUND: Combination antiviral therapy holds the promise of increasing response rates while decreasing antiviral resistance, but has yet to be shown to be beneficial or necessary in chronic hepatitis B. AIM: To evaluate the benefit of combination therapy with adefovir and lamivudine versus adefovir alone in maintaining virological, biochemical and histological responses. METHODS: Patients with chronic hepatitis B with and without previous lamivudine therapy were randomised to receive adefovir alone (10 mg/daily) or adefovir and lamivudine (100 mg/daily) for up to 192 weeks. Study endpoints were (i) maintained virological (HBV DNA <500 copies/mL), biochemical and histological response, (ii) loss of HBeAg and (iii) loss of HBsAg. RESULTS: A total of 41 patients were enrolled, including 31 HBeAg -positive and 31 treatment-naïve subjects. 30 patients remained on assigned therapy at 192 weeks. The percentage of patients achieving a combined maintained response was higher in the combination than the monotherapy arm, both at week 48 (59% vs. 26%, P = 0.06) and 192 (68% vs. 31%, P = 0.03). At week 192, 76% of the combination vs. 36% of the monotherapy group had loss of HBeAg (P = 0.03). One patient receiving adefovir cleared HBsAg. Adefovir resistance developed in 6 of 19 (32%) monotherapy but none of 22 combination treated patients (P = 0.03). CONCLUSIONS: Extended combination therapy with lamivudine and adefovir is associated with a high rate of long-term virological and biochemical response. Adefovir monotherapy appears to be less effective mainly because of poor initial response and the ultimate development of antiviral resistance (www.Clinical. Trials.gov NCT00023309).

Duloxetine hepatotoxicity: a case-series from the drug-induced liver injury network.

BACKGROUND: Case reports suggest that duloxetine hepatotoxicity may arise, but risk factors, presenting features and clinical course are not well-described. AIM: To describe the presenting features and outcomes of seven well-characterized patients with suspected duloxetine hepatotoxicity. METHODS: Patients enrolled in the Drug-Induced Liver Injury Network Prospective Study underwent an extensive laboratory and clinical evaluation to exclude competing aetiologies of liver injury as well as a standardized assessment for causality and disease severity. RESULTS: Between 1/2006 and 9/2009, six of the seven cases of DILI attributed to duloxetine were assessed as definite or very likely. Median patient age was 49 years, six (86%) were women and the median latency from drug initiation to DILI onset was 50 days. Six patients developed jaundice and the median peak alanine aminotransferase in the five patients with acute hepatocellular injury was 1633 IU/L. Ascites developed in one patient and acute renal dysfunction in two others (29%). All patients recovered without liver transplantation even though three had pre-existing chronic liver disease. Liver histology in four cases demonstrated varying patterns of liver injury. CONCLUSIONS: Duloxetine hepatotoxicity developed within 2 months of drug intake and led to clinically significant liver injury. A spectrum of laboratory, histological and extra-hepatic features were noted at presentation.

Inoculation of sugarcane with Pantoea sp. increases amino acid contents in shoot tissues; serine, alanine, glutamine and asparagine permit concomitantly ammonium excretion and nitrogenase activity of the bacterium.

Pantoea sp. is an endophytic nitrogen-fixing bacterium isolated from sugarcane tissues. The aim of the present study was to determine the contents of amino acids in sugarcane as a result of inoculation of nodes and nodal roots with Pantoea sp. strain 9C and to evaluate the effects of amino acids on growth, nitrogenase activity and ammonium excretion of the bacterium. Content of almost all amino acids increased in 30-day-old plantlets by root inoculation. The most abundant amino acids in shoot tissues were asparagine and proline, and those in nodal roots were asparagine, proline, aspartic acid, glutamic acid and serine. The bacterium was able to grow on all tested amino acids except histidine, isoleucine and leucine. Nitrogenase Pantoea sp. was partially inhibited by 1, 2 or 5mmolL(-1) and completely inhibited by 10mmolL(-1) of NH(4)(+) in the media. Pantoea sp. showed nitrogenase activity in 5mmolL(-1) of serine, asparagine, threonine, alanine, proline, tyrosine, valine, methionine, lysine, phenylalanine, cysteine, tryptophan, citrulline and ornithine. Pantoea sp. did not excrete ammonium when it grew in vivo conditions favoring nitrogen fixation; however, ammonium was detected in the supernatant when 5mmolL(-1) asparagine, aspartic acid, alanine, serine or glutamine was added to the medium. The highest ammonium concentration in the supernatant was detected, when Pantoea grew on serine. Ammonium in the supernatant and nitrogenase activity were only detectable concomitantly when the medium was supplemented with serine, alanine, glutamine or asparagine. We discuss roles of amino acids on plant-bacteria interaction during the colonization of sugarcane plants.