Good outcomes after pediatric intraperitoneal kidney transplant

BACKGROUND

Kidney transplantation in small children is technically challenging. Consideration of whether to use intraperitoneal versus extraperitoneal placement of the graft depends on patient size, clinical history, anatomy, and surgical preference. We report a large single-center experience of intraperitoneal kidney transplantation and their outcomes.

METHODS

We conducted a retrospective review of pediatric patients who underwent kidney transplantation from April 2011 to March 2018 at a single large volume center. We identified those with intraperitoneal placement and assessed their outcomes, including graft and patient survival, rejection episodes, and surgical or non-surgical complications.

RESULTS

Forty-six of 168 pediatric kidney transplants (27%) were placed intraperitoneally in children mean age 5.5 ± 2.3 years (range 1.6-10 years) with median body weight 18.2 ± 5 kg (range 11.4-28.6 kg) during the study period. Two patients (4%) had vascular complications; 10 (22%) had urologic complications requiring intervention; all retained graft function. Thirteen patients (28%) had prolonged post-operative ileus. Eight (17%) patients had rejection episodes ≤6 months post-transplant. Only one case resulted in graft loss and was associated with recurrent focal segmental glomerular sclerosis (FSGS). Two patients (4%) had chronic rejection and subsequent graft loss by 5-year follow-up. At 7-year follow-up, graft survival was 93% and patient survival was 98%.

CONCLUSIONS

The intraperitoneal approach offers access to the great vessels, which allows greater inflow and outflow and more abdominal capacity for an adult donor kidney, which is beneficial in very small patients. Risk of graft failure and surgical complications were not increased when compared to other published data on pediatric kidney transplants.

Allograft discard risk index for heart transplantation

BACKGROUND

The numberof patients awaiting heart transplantation (HTx) substantially exceeds the number of donor hearts transplanted each year, yet nearly 65% of eligible donor hearts are discarded rather than transplanted.

METHODS

Deceased organ donors listed within the UNOS Deceased Donor Database between 2010 and 2020 were reviewed. Those greater than 10 years old and consented for heart donation were included and randomly separated into training (n = 48 435) and validation (n = 24 217) cohorts. A discard risk index (DSRI) was created using the results of univariable and multivariable analyses. Discard data were assessed at DSRI value deciles, and stratum-specific likelihood ratio (SSLR) analysis and Kaplan-Meier survival function were used for mortality data.

RESULTS

Factors associated with higher DSRI values included donor age > 45, LVEF, HBV-core antibodies, hypertension, and diabetes. The DSRI C-statistic was .906 in the training cohort and .904 in the validation cohort. The DSRI did not reliably predict 30-day or 1-year mortality after transplantation (C-statistic .539 and .532, respectively).

CONCLUSIONS

The factors leading to heart allograft discard are not correlated to the same degree with post-transplant outcomes. This suggests that optimizing utilization of certain allografts with slightly higher risk of discard could increase the heart donor pool with limited impact on posttransplant mortality.

Elevated serum sodium in recipients of liver transplantation has a substantial impact on outcomes

Dysnatremias are a rare but significant event in liver transplantation. While recipient pre-transplant hypernatremia has been demonstrated to increase post-transplant mortality, the degree of hypernatremia and the impact of its resolution have been less well characterized. Here, we used multivariate Cox regression with a comprehensive list of donor and recipient factors in order to conduct a robust multivariate retrospective database study of 54,311 United Network for Organ Sharing (UNOS) liver transplant patients to analyze the effect of pre-transplant serum sodium on post-transplant mortality, post-transplant length of hospitalization, and post-transplant graft survival. Mortality and graft failure increased in a stepwise fashion with increasing pre-transplant hypernatremia: 145 -150 mEq/L (HR = 1.118 and HR = 1.113), 150-155 mEq/L (HR = 1.324 and HR = 1.306), and > 155 mEq/L (HR = 1.623 and HR = 1.661). Pre-transplant hypo- and hypernatremia also increased length of post-transplant hospitalization: < 125 mEq/L (HR = 1.098), 125-130 mEq/L (HR = 1.060), 145 -150 mEq/L (HR = 1.140), and 150-155 mEq/L (HR = 1.358). Resolution of hypernatremia showed no significant difference in mortality compared with normonatremia, while unresolved hypernatremia significantly increased mortality (HR = 1.254), including a durable long-term increased mortality risk for patients with creatinine < 2 mg/dL and MELD < 25. Pre-transplant hypernatremia serves as a morbid prognostic indicator for post-transplant morbidity and mortality.

Factors associated with long-term graft survival in pediatric kidney transplant recipients

Pediatric kidney transplant recipients generally have good outcomes post-transplantation. However, the younger age and longer life span after transplantation in the pediatric population make understanding the multifactorial nature of long-term graft survival critical. This investigation analyzes factors associated with 10-year survival to identify areas for improvement in patient care. Kaplan-Meier with log-rank test and univariable and multivariable logistic regression methods were used to retrospectively analyze 7785 kidney transplant recipients under the age of 18 years from January 1, 1998, until March 9, 2008, using United Network for Organ Sharing (UNOS) data. Our end-point was death-censored 10-year graft survival after excluding recipients whose grafts failed within one year of transplant. Recipients aged 5-18 years had lower 10-year graft survival, which worsened as age increased: 5-9 years (OR: 0.66; CI: 0.52-0.83), 10-14 years (OR: 0.43; CI: 0.33-0.55), and 15-18 years (OR: 0.34; CI: 0.26-0.44). Recipient African American ethnicity (OR: 0.67; CI: 0.58-0.78) and Hispanic donor ethnicity (OR: 0.82; CI: 0.72-0.94) had worse outcomes than other donor and recipient ethnicities, as did patients on dialysis at the time of transplant (OR: 0.82; CI: 0.73-0.91). Recipient private insurance status (OR: 1.35; CI: 1.22-1.50) was protective for 10-year graft survival. By establishing the role of age, race, and insurance status on long-term graft survival, we hope to guide clinicians in identifying patients at high risk for graft failure. This study highlights the need for increased allocation of resources and medical care to reduce the disparity in outcomes for certain patient populations.

The Ryanodine Receptor Contributes to the Lysophosphatidylcholine-Induced Mineralization in Valvular Interstitial Cells

PURPOSE

Fibrocalcific aortic valve disease (CAVD) is caused by the deposition of calcific nodules in the aortic valve leaflets, resulting in progressive loss of function that ultimately requires surgical intervention. This process is actively mediated by the resident valvular interstitial cells (VICs), which, in response to oxidized lipids, transition from a quiescent to an osteoblast-like state. The purpose of this study was to examine if the ryanodine receptor, an intracellular calcium channel, could be therapeutically targeted to prevent this phenotypic conversion.

METHODS

The expression of the ryanodine receptor in porcine aortic VICs was characterized by qRT-PCR and immunofluorescence. Next, the VICs were exposed to lysophosphatidylcholine, an oxidized lipid commonly found in low-density lipoprotein, while the activity of the ryanodine receptor was modulated with ryanodine. The cultures were analyzed for markers of cellular mineralization, alkaline phosphatase activity, proliferation, and apoptosis.

RESULTS

Porcine aortic VICs predominantly express isoform 3 of the ryanodine receptors, and this protein mediates the cellular response to LPC. Exposure to LPC caused elevated intracellular calcium concentration in VICs, raised levels of alkaline phosphatase activity, and increased calcific nodule formation, but these changes were reversed when the activity of the ryanodine receptor was blocked.

CONCLUSIONS

Our findings suggest blocking the activity of the ryanodine receptor can attenuate the valvular mineralization caused by LPC. We conclude that oxidized lipids, such as LPC, play an important role in the development and progression of CAVD and that the ryanodine receptor is a promising target for pharmacological intervention.

The decreasing predictive power of MELD in an era of changing etiology of liver disease

The field of liver transplantation has shifted considerably in the MELD era, including changing allocation, immunosuppression, and liver failure etiologies, as well as better supportive therapies. Our aim was to evaluate the predictive accuracy of the MELD score over time. The United Network for Organ Sharing provided de-identified data on 120 156 patients listed for liver transplant from 2002-2016. The ability of the MELD score to predict 90-day mortality was evaluated by a concordance (C-) statistic and corroborated with competing risk analysis. The MELD score's concordance with 90-day mortality has downtrended from 0.80 in 2003 to 0.70 in 2015. While lab MELD scores at listing and transplant climbed in that interval, score at waitlist death remained steady near 35. Listing age increased from 50 to 54 years. HCV-positive status at listing dropped from 33 to 17%. The concordance of MELD and mortality does not differ with age (>60 = 0.73, <60 = 0.74), but is lower in diseases that are increasing most rapidly-alcoholic liver disease and non-alcoholic fatty liver disease-and higher in those that are declining, particularly in HCV-positive patients (HCV positive = 0.77; negative = 0.73). While MELD still predicts mortality, its accuracy has decreased; changing etiology of disease may contribute.

Single amino acid changes in the mumps virus haemagglutinin–neuraminidase and polymerase proteins are associated with neuroattenuation

It has previously been shown that three amino acid changes, one each in the fusion (F; Ala/Thr-91→Thr), haemagglutinin–neuraminidase (HN; Ser-466→Asn) and polymerase (L; Ile-736→Val) proteins, are associated with attenuation of a neurovirulent clinical isolate of mumps virus (88-1961) following serial passage in vitro. Here, using full-length cDNA plasmid clones and site-directed mutagenesis, it was shown that the single amino acid change in the HN protein and to a lesser extent, the change in the L protein, resulted in neuroattenuation, as assessed in rats. The combination of both amino acid changes caused neuroattenuation of the virus to levels previously reported for the clinical isolate following attenuation in vitro. The amino acid change in the F protein, despite having a dramatic effect on protein function in vitro, was previously shown to not be involved in the observed neuroattenuation, highlighting the importance of conducting confirmatory in vivo studies. This report provides additional supporting evidence for the role of the HN protein as a virulence factor and, as far as is known, is the first report to associate an amino acid change in the L protein with mumps virus neuroattenuation.

Randomized controlled trial comparing Merocel and RapidRhino packing in the management of anterior epistaxis

OBJECTIVES

A prospective non-blinded randomized controlled trial to compare the efficacy of Merocel and RapidRhino nasal packs in the treatment of anterior epistaxis.

METHODS

Fifty-two consecutive participants admitted with anterior epistaxis refractory to digital pressure or nasal cautery were randomized to treatment using one or other of the nasal packs. Patients who required repacking because of continued bleeding, only the first packs were included in the analysis. Haemostatic properties of the packs were measured by grading bleeding during and after removal of the pack (0-4, where four is uncontrollable) and by noting if the nose was re-packed or not. The difficulty of insertion and removal (graded 0-3 by clinician where 3 is the most difficult) and the participant's perception of discomfort (graded 0-10, where 10 is the worst pain) during insertion and removal of the pack were also measured.

RESULTS

For bleeding, the mean values for Merocel and RapidRhino during packing and after pack removal were not significant (P = 0.38 and 0.82 respectively). The mean values of patient discomfort on insertion were 6.9 and 5.0 (P = 0.01), and for discomfort on removal were 4.6 and 3.4 (P = 0.05) respectively. The mean values of insertion graded by the clinician were 1.7 and 0.9 (P = 0.0003), and for removal were 1.4 and 0.4 (P < 0.0001).

CONCLUSIONS

RapidRhino and Merocel are equally effective in the control of anterior epistaxis but RapidRhino is significantly more comfortable for the patient and easier for the healthcare worker during insertion and removal.

Transient quadriplegia following re-puncture of tracheo-oesophageal fistula

We present a case of a laryngectomized patient who underwent re-puncture of tracheo-oesophageal fistula for speaking valve voice restoration, resulting in a previously unreported inherent complication of this procedure: extradural abscess of the cervical spine with transient quadriplegia.

The role of magnetic resonance imaging in the assessment of suspected extrinsic tracheobronchial compression due to vascular anomalies

AIMS

To evaluate the role of magnetic resonance imaging (MRI) in the assessment of children with suspected extrinsic tracheobronchial compression due to vascular anomalies.

METHODS

Retrospective case note review in a tertiary referral centre. Twenty nine children who underwent dynamic laryngotracheobronchoscopy (DLTB) and were found to have a clinical suspicion of extrinsic tracheobronchial compression were evaluated. All subsequently underwent thoracic MRI within 10 days. The findings on endoscopy were compared to those of MRI, and where performed, echocardiography, aortography, and surgery.

RESULTS

There were 17 males and 12 females (mean age 5 months, range 28 weeks gestation to 60 months). The most common presenting features were stridor and cyanotic episodes. MRI showed abnormalities in 21 patients. There were five vascular rings (three double aortic arches and two right aortic arches) and 11 cases of innominate artery compression. Other vascular anomalies noted included aberrant right subclavian artery and aneurysmal left pulmonary artery. Echocardiography was generally found to be unhelpful in the diagnosis of extra-cardiac vascular abnormalities. Angiography was subsequently conducted in eight children; findings agreed with those shown on MRI. Surgery was performed on all five vascular rings, one innominate artery compression, and one aneurysmal left pulmonary artery. Surgical findings were also compatible with the preoperative MRI.

CONCLUSIONS

This study shows the successful use of MRI as the initial imaging modality in endoscopically suspected extrinsic vascular compression of the upper airway. It enables accurate delineation of vascular anomalies and, unlike aortography, is non-invasive and does not require the use of contrast media.

A quantitative determination of multi-protein interactions by the analysis of confocal images using a pixel-by-pixel assessment algorithm

MOTIVATION

Recent advances in confocal microscopy have allowed scientists to assess the expression, and to some extent, the interaction/colocalization of multiple molecules within cells and tissues. In some instances, accurately quantifying the colocalization of two or more proteins may be critical. This can require the acquisition of multiple Z plane images (Z stacks) throughout a specimen and, as such, we report here the successful development of a freeware, open-source image analysis tool, IMAJIN_COLOC, developed in PERL (v. 5.8, build 806), using the PERLMagick libraries (ImageMagick). Using a pixel-by-pixel analysis algorithm, IMAJIN_COLOC can analyze images for antigen expression (any number of colors) and can measure all possible combinations of colocalization for up to three colors by analyzing a Z stack gallery acquired for each sample. The simultaneous (i.e. in a single pass) analysis of three-color colocalization, and batch analysis capabilities are distinctive features of this program.

RESULTS

A control image, containing known individual and colocalized pixel counts, was used to validate the accuracy of IMAJIN_COLOC. As further validation, pixel counts and colocalization values from the control image were compared to those obtained with the software packaged with the Zeiss laser-scanning microscope (LSM AIM, version 3.2). The values from both programs were found to be identical. To demonstrate the applicability of this program in addressing novel biological questions, we examined the role of neurons in eliciting an immune reaction in response to viral infection. Specifically, we successfully examined expression of the chemokine RANTES in measles virus (MV) infected hippocampal neurons and quantified changes in RANTES production throughout the disease period. The resultant quantitative data were also evaluated visually, using a gif image created during the analysis.

AVAILABILITY

PERL (ActivePerl, version 5.8) is available at activestate.com; the PERLMagick libraries are available at imagemagick.org, and IMAJIN_COLOC, the source code and user documentation can be downloaded from http://www.fda.gov/cber/research/imaging/imageanalysis.htm.

Expression of somatostatin receptors in arginine vasopressin hormone-secreting olfactory neuroblastoma--report of two cases

OBJECTIVE

Arginine vasopressin hormone-secreting olfactory neuroblastomas are extremely rare, with fewer than twenty cases reported in the literature. Two of these cases, both initially presenting with the syndrome of inappropriate antidiuretic hormone, are presented. The second tumour was successfully identified using somatostatin receptor (octreotide) radiographic scintography.

METHOD

The pathological specimens from both cases were examined immunohistochemically for somatostatin receptors.

RESULTS

Samples from both cases demonstrated positivity for somatostatin receptors.

CONCLUSIONS

This report demonstrates the potential use of somatastatin analogues in the investigation, follow-up and treatment of patients with olfactory neuroblastoma.

Histiocytic necrotising lymphadenitis (Kikuchi's disease): A rare cause of cervical lymphadenopathy

Both Head and Neck Surgeons and General Surgeons are frequently referred patients with cervical lymphadenopathy. An uncommon but important cause is histiocytic necrotising lymphadenitis. This is a benign self-limiting disease that has been confused with malignant lymphomas. Some patients may also experience distressing and debilitating symptoms which can last for months. We describe four cases to illustrate the varied clinical presentation of this disease and present new signs seen in association with it. A remarkable therapeutic response to a short course of oral corticosteroids was observed in one case.

Two major histocompatibility complex class I-restricted epitopes of the Borna disease virus p10 protein identified by cytotoxic T lymphocytes induced by DNA-based immunization

Borna disease virus (BDV) infection of Lewis rats is the most studied animal model of Borna disease, an often fatal encephalomyelitis. In this experimental model, BDV-specific CD8(+) cytotoxic T lymphocytes (CTLs) play a prominent role in the immunopathogenesis of infection by the noncytolytic, persistent BDV. Of the six open reading frames of BDV, CTLs to BDV X (p10) and the L-polymerase have never been studied. In this study, we used plasmid immunization to investigate the CTL response to BDV X and N. Plasmid-based immunization was a potent CTL inducer in Lewis rats. Anti-X CTLs were primed by a single injection of the p10 cDNA. Two codominant p10 epitopes, M(1)SSDLRLTLL(10) and T(8)LLELVRRL(16), associated with the RT1.A(l) major histocompatibility complex class I molecules of the Lewis rats, were identified. In addition, immunization with a BDV p40-expressing plasmid confirmed the previously reported RT1.A(l)-restricted A(230)SYAQMTTY(238) peptide as the CTL target for BDV N. In contrast to the CTL responses, plasmid vaccination was a poor inducer of an antibody response to p10. Three injections of a recombinant eukaryotic expression plasmid of BDV p10 were needed to generate a weak anti-p10 immunoglobulin M response. However, the antibody response could be optimized by a protein boost after priming with cDNA.

Prevalence of circulating antibodies to p10, a non-structural protein of the Borna disease virus in cats with ataxia

Japanese domestic cats were surveyed for circulating antibodies to the plO and p24 proteins of the Borna disease virus (BDV) by Western blotting. Twenty-four of 52 cats (46.2%) with ataxia and other neurologic symptoms of unknown cause were positive for antibodies to BDV p10 and/or p24. In contrast, cats without neurological symptoms gave a significantly lower prevalence of anti-BDV antibodies to p10 and/or p24 (36 of 152 cats, 23.7%). Thirty specific pathogen-free (SPF) cats tested as controls were uniformly negative to BDV pl0 and p24 antigens. These results suggest that BDV may play a role in ataxia in cats. Additionally, our results suggest that it is necessary to use both p10 and p24 as antigens to detect circulating antibodies to BDV in cats.

Incidental findings on magnetic resonance imaging screening for cerebellopontine angle tumours

The otolaryngologist who requests magnetic resonance imaging (MRI) scans to exclude cerebellopontine angle (CPA) tumours may discover incidental pathologies. We retrospectively reviewed the results of 644 consecutive MRI screening scans with the aim of identifying findings other than CPA tumours. Two hundred and eighty-nine (45 per cent) scans featured one or more anomalies or abnormalities, including CPA tumour (23, four per cent), vascular loop (30, five per cent), basilar artery ectasia (13, two per cent), multiple high signal areas (135,21 per cent), brain atrophy (52, eight per cent), sinus findings (56, nine per cent), middle ear/mastoid disease (34, five per cent), and a variety of other findings (39, six per cent) including clinically serious lesions (11, two per cent). The significance and management of these incidental findings is discussed. The majority were not clinically significant but the occasional presence of a serious incidental pathology should be borne in mind. Basilar artery ectasia and multiple high signal areas may be responsible for the symptoms investigated by MRI, and screening for cerebrovascular disease risk factors in such patients may be appropriate.

Structure and expression of a novel frizzled gene isolated from the developing mouse gut

The Wnt/APC (adenomatous polyposis coli)/beta-catenin pathway plays a central role in the pathogenesis of colorectal cancer and probably also in normal development of the gastrointestinal tract. Frizzled proteins function as cell-surface receptors for the Wnt family of extracellular ligands. Many components of the Wnt signalling pathway are expressed widely, and determinants of tissue-specific functions are poorly understood. A better understanding of how Wnt signalling regulates tissue-specific development and gut epithelial homoeostasis requires characterization of the many components of this signalling pathway. We therefore wished to identify frizzled genes with limited tissue distribution of expression and isolated Mfz10, a novel member of the mouse family of frizzled genes, from the developing fetal gut. Highest levels of Mfz10 mRNA are detected throughout late embryonic development, in the brain, heart, lung and digestive tract. In adult mice Mfz10 mRNA is detected at highest levels in the heart, brain and lung. Expression in the adult gastrointestinal tract is much weaker, with higher levels in foregut derivatives (oesophagus and stomach) compared with regions derived from the fetal midgut and hindgut; particularly strong mRNA expression is observed in the squamous epithelium of the oesophagus. The amino acid sequence of Mfz10 is nearly identical to that of human FzE2 (also known as FzD2). Interestingly, mRNA levels of human FzD2 are reported to be up-regulated in oesophageal squamous cell carcinomas. These findings suggest a likely role for Mfz10 in the developing and adult foregut.

Action of the Caenorhabditis elegans GATA factor END-1 in Xenopus suggests that similar mechanisms initiate endoderm development in ecdysozoa and vertebrates

In ecdysozoan protostomes, including arthropods and nematodes, transcription factors of the GATA family specify the endoderm: Drosophila dGATAb (ABF/Serpent) and Caenorhabditis elegans END-1 play important roles in generating this primary germ layer. end-1 is the earliest expressed endoderm-specific gene known in C. elegans and appears to initiate the program of gene expression required for endoderm differentiation, including a cascade of GATA factors required for development and maintenance of the intestine. Among vertebrate GATA proteins, the GATA-4/5/6 subfamily regulates aspects of late endoderm development, but a role for GATA factors in establishing the endoderm is unknown. We show here that END-1 binds to the canonical target DNA sequence WGATAR with specificity similar to that of vertebrate GATA-1 and GATA-4, and that it functions as a transcriptional activator. We exploited this activity of END-1 to demonstrate that establishment of the vertebrate endoderm, like that of invertebrate species, also appears to involve GATA transcriptional activity. Like the known vertebrate endoderm regulators Mixer and Sox17, END-1 is a potent activator of endoderm differentiation in isolated Xenopus ectoderm. Moreover, a dominant inhibitory GATA-binding fusion protein abrogates endoderm differentiation in intact embryos. By examining these effects in conjunction with those of Mixer- and Sox17beta-activating and dominant inhibitory constructs, we further establish the likely relationships between GATA activity and these regulators in early development of the vertebrate endoderm. These results suggest that GATA factors may function sequentially to regulate endoderm differentiation in both protostomes and deuterostomes.

Characterization of the P protein-binding domain on the 10-kilodalton protein of Borna disease virus

The Borna disease virus (BDV) is the prototype member of the Bornaviridae, and it replicates in the cell nucleus. The BDV p24P and p40N proteins carry nuclear localization signals (NLS) and are found in the nuclei of infected cells. The BDV p10 protein does not have an NLS, but it binds with P and/or N and is translocated to the nucleus. Hence, p10 may play a role in the replication of BDV in the cell nucleus. Here, we show that the P-binding domain is located in the N terminus of p10 and that S(3) and L(16) are important for the interaction.

The use of inhalers in patients with tracheal stomas or tracheostomy tubes

Patients with chronic obstructive airways disease (COAD) or asthma who have a tracheostomy tube or tracheal stoma have difficulty using metered dose inhalers (MDIs) because of a failure to achieve a good seal between the tracheostomy tube or stoma and the MDI or spacer device mouthpiece. Many such patients therefore utilize nebulizers. MDIs in comparison to nebulizers have the advantages of being more compact, portable, easy to use, less time-consuming, and cheaper. We present the case of a 74-year-old man who underwent a laryngectomy with tracheal stoma formation who had a poor response with nebulizers and required oral steroids. He was subsequently, with the help of a number of attached devices, able to use his MDIs to good effect. We describe a number of devices and adaptors to enable patients with laryngectomy stomas or tracheostomy tubes to utilize MDIs and undergo respiratory function tests. We recommend that all such patients should have the benefit of a consultation with a dedicated respiratory nurse who can provide the appropriate MDIs, devices and adaptors to optimize the treatment of their lower respiratory tract condition.

Nuclear localization of the protein from the open reading frame x1 of the Borna disease virus was through interactions with the viral nucleoprotein

Previous studies have predicted the presence of a small open reading frame (ORFx1) located between ORF-1 and ORF-2 of the Borna disease viral (BDV) genome. The ORFx1 is expressed as a p10 protein that is localized in the nucleus and cytoplasm of BDV-infected cells. In this study, we cloned the nucleotide sequence of ORFx1 into expression vectors and showed that it is expressed as p10. An anti-p10 serum gave nuclear and cytoplasmic staining of cells persistently infected with BDV. Immunoprecipitation of p10 from BDV-infected cells coprecipitated the p40 nucleoprotein N and the 24-kDa viral phosphoprotein P. Transient transfection of noninfected cells showed that p10 and p40 can be coprecipitated and revealed that p10 localized in the cytoplasm was imported into the nucleus in the presence of the BDV p40 N. In vitro protein-protein interaction studies on solid phase showed the direct interaction of the p10 with the BDV N protein. The subcellular distribution of p10 and its interaction with p40 suggest that this protein may play a role in the nuclear replication and/or transcription of BDV.