Accumulation of p53 in infectious mononucleosis tissues

Revisiting the Tissue Microenvironment of Infectious Mononucleosis: Identification of EBV Infection in T Cells and Deep Characterization of Immune Profiles

To aid understanding of primary EBV infection, we have performed an in depth analysis of EBV-infected cells and of local immune cells in tonsils from infectious mononucleosis (IM) patients. We show that EBV is present in approximately 50% of B-cells showing heterogeneous patterns of latent viral gene expression probably reflecting different stages of infection. While the vast majority of EBV+ cells are B-cells, around 9% express T-cell antigens, with a predominance of CD8+ over CD4+ cells. PD-L1 was expressed by a median of 14% of EBV+ cells. The numbers of EBER+PD-L1+ cells were directly correlated with the numbers of EBER+CD3+ and EBER+CD8+ cells suggesting a possible role for PD-L1 in EBV infection of T-cells. The microenvironment of IM tonsils was characterized by a predominance of M1-polarized macrophages over M2-polarized cells. However, at the T-cell level, a heterogeneous picture emerged with numerous Th1/cytotoxic cells accompanied and sometimes outnumbered by Th2/regulatory T-cells. Further, we observed a direct correlation between the numbers of Th2-like cells and EBV- B-cells. Also, a prevalence of cytotoxic T-cells over Th2-like cells was associated with an increased viral load. These observations point to contribution of B- and Th2-like cells to the control of primary EBV infection. 35% of CD8+ cells were differentiated CD8+TBET+ cells, frequently detected in post-capillary venules. An inverse correlation was observed between the numbers of CD8+TBET+ cells and viral load suggesting a pivotal role for these cells in the control of primary EBV infection. Our results provide the basis for a better understanding of immune reactions in EBV-associated tumors.

p53 as a retrovirus-induced oxidative stress modulator

Infection of astrocytes by the neuropathogenic mutant of Moloney murine leukemia virus, ts1, exhibits increased levels of reactive oxygen species (ROS) and signs of oxidative stress compared with uninfected astrocytes. Previously, we have demonstrated that ts1 infection caused two separate events of ROS upregulation. The first upregulation occurs during early viral establishment in host cells and the second during the virus-mediated apoptotic process. In this study, we show that virus-mediated ROS upregulation activates the protein kinase, ataxia telangiectasia mutated, which in turn phosphorylates serine 15 on p53. This activation of p53 however, is unlikely associated with ts1-induced cell death. Rather p53 appears to be involved in suppressing intracellular ROS levels in astrocytes under oxidative stress. The activated p53 appears to delay retroviral gene expression by suppressing NADPH oxidase, a superoxide-producing enzyme. These results suggest that p53 plays a role as a retrovirus-mediated oxidative stress modulator.

Atypical hyperplasia of the marginal zone of B follicles in a polymorphic Epstein-Barr virus-associated lymphoproliferative disorder occurring in an adolescent with human immunodeficiency virus infection

Epstein-Barr virus (EBV)-associated lymphoid proliferations that are similar to post-transplantation lymphoproliferative disorders may occasionally occur in the setting of human immunodeficiency virus (HIV) infection. Herein, we describe such a lesion involving the adenoids in a HIV-seropositive adolescent who acquired immunity against EBV during childhood. On microscopic examination, the marginal zone of B follicles and the interfollicular area were enlarged due to the accumulation of small or intermediate-sized lymphocytes, immunoblasts, epithelioid histiocytes, and plasma cells. A few atypical immunoblasts resembling Reed-Sternberg cells were also present. Most of the cells seen in these expanded regions belonged to the B-cell lineage and displayed a phenotype consistent with that of postgerminal center B cells. No clonal rearrangement of the genes coding for the heavy chain of the immunoglobulin could be demonstrated by polymerase chain reaction analysis. In-situ hybridization studies revealed the presence of EBV early RNA in a significant number of these cells, which suggests the participation of this virus in the pathogenesis of such a B-cell proliferation. The clinical course was benign; no progression or recurrence could be seen more than 24 months after the diagnosis. This atypical lymphoproliferative disorder is probably related to polyclonal reactivation of a latent EBV infection due to a local or systemic immune imbalance induced by HIV replication. Recognition of this reactive condition is important to prevent overtreatment.

Low frequency of Epstein Barr virus association and high frequency of p53 overexpression in an Argentinean pediatric T-cell lymphoma series

T-cell non-Hodgkin's lymphomas (NHLs) represent 10% to 15% of all diagnosed lymphomas in Western countries. Various geographic frequencies of T-cell NHL have been documented, in part reflecting increased exposure to pathogenic factors such as Epstein-Barr virus (EBV). Our aims were to assess EBV and p53 expression in Argentine pediatric T-cell lymphoma and to correlate them with patients' survival. Epstein-Barr encoded RNAs (EBERs) in situ hybridization and LMP1 and p53 immunohistochemical staining were performed on formalin-fixed paraffin-embedded lymph node biopsies from 25 pediatric T-lymphoma patients. In 17 of 25 samples good-quality DNA was obtained, and EBER polymerase chain reaction was assessed to confirm in situ hybridization and immunohistochemical results. Epstein-Barr virus expression was found in 8.0% of cases. p53-positive staining was distributed in 92% of pediatric cases. Kaplan-Meier survival analysis showed that neither EBV nor p53 expression was statistically significantly associated with event-free survival. Our data showed a low frequency of EBV association with pediatric T-cell lymphoma. It seems that p53 plays an important role in proliferation in our studied population, since it is overexpressed in 92% of T-cell lymphoma cases.

Down-regulation of Jab1, HIF-1alpha, and VEGF by Moloney murine leukemia virus-ts1 infection: a possible cause of neurodegeneration

Moloney murine leukemia virus-temperature sensitive (MoMuLV-ts1)-mediated neuronal death is a result of both loss of glial support and release of cytokines and neurotoxins from ts1-infected glial cells. Here the authors propose vascular endothelial growth factor (VEGF) down-regulation as another contributory factor in neuronal degeneration induced by ts1 infection. To determine how ts1 affects VEGF expression in ts1-infected brain, the authors examined the expression of several proteins that are important in regulating the expression of VEGF. The authors found significant decreases in Jun-activating domain-binding protein 1 (Jab1), hypoxia-inducible factor (HIF)-1alpha, and VEGF levels and increases in p53 protein levels in ts1-infected brains compared to noninfected control brains. The authors suggest that a decrease Jab1 expression in ts1 infection leads to accumulation of p53, which binds to HIF-1alpha to accelerate its degradation. A rapid degradation of HIF-1alpha leads to decreased VEGF production and secretion. Considering that endothelial cells are the most conspicuous in virus replication and production in ts1 infection, but are not killed by the infection, the authors examined the expression of these proteins using infected and noninfected mouse cerebrovascular endothelial (CVE) cells. The ts1- infected CVE cells showed decreased Jab1, HIF-1alpha, and VEGF mRNA and protein levels and increased p53 protein levels compared with noninfected cells, consistent with the results found in vivo. These results confirm that ts1 infection results in insufficient secretion of VEGF from endothelial cells and may result in decreased neuroprotection. This study suggested that ts1-mediated neuropathology in mice may result from changes in expression and activity of Jab1, p53, and HIF-1alpha, with a final target on VEGF expression and neuronal degeneration.

Induction of p53 accumulation by Moloney murine leukemia virus-ts1 infection in astrocytes via activation of extracellular signal-regulated kinases 1/2

SUMMARY

We previously reported that Moloney murine leukemia virus-ts1-mediated neuronal degeneration in mice is likely a result of both loss of glial support and release of cytokines and neurotoxins from ts1-infected glial cells. Viral infection in some cell types regulates expression of p53 protein, a key regulator of cell proliferation and death. Therefore, we hypothesized that p53 and its dependent genes may be linked with ts1-mediated neuropathology. We examined the presence of p53 and its dependent gene product, a proapoptotic protein bax-alpha, in ts1-induced spongiform encephalomyelopathy. Compared with controls, the lesions of infected animals contained increased levels of p53 and bax-alpha in astrocytes, as shown by strong nuclear p53 and cytoplasmic bax-alpha immunoreactivity in astrocytes. To determine how ts1 affects p53 expression in astrocytes, we then assessed the expression of p53 and its dependent genes, such as bax-alpha and p21, in infected and uninfected immortalized C1 astrocytes and studied possible pathways responsible for p53 accumulation in infected astrocytes. In these studies using mitogen-activated protein kinase inhibitors, infection-induced increases in the p53 level were partially blocked by PD98059, a synthetic inhibitor of MEK1 that is the immediate upstream kinase of extracellular signal-regulated kinases 1/2 (ERK1/2), but not by SB202190, a potent p38 kinase inhibitor. Furthermore, treatment with PD98059 significantly decreased the level of p21 protein, a p53-dependent gene product. These results suggest that ts1 infection may stabilize p53 protein through activation of ERKs in C1 astrocytes, leading to increased expression of the p21 and bax-alpha proteins, both of which induce cell cycle arrest and apoptosis. Our studies suggest that ts1 neuropathology in mice may result from changes in expression and activity of p53, brought about in part by ts1 activation of ERK.

Lymphomas of the oral cavity: histology, immunologic type, and incidence of Epstein-Barr virus infection

The purpose of this study was to determine the histologic class and immunologic phenotype of lymphomas presenting initially in the oral cavity and whether this correlated to a high incidence of Epstein-Barr virus (EBV) infection as has been reported with lymphomas in the nasal cavity. Seventy-one cases of oral lymphomas from the oral pathology referral service were analyzed retrospectively. They were classified according to the Revised European American Lymphoma (REAL) classification system using routine immunohistochemistry. EBV infection was determined by detection of early viral RNA sequences (EBER) and latent membrane protein (LMP-1) expression. Only non-Hodgkin's lymphomas were observed, with a female predominance of 2:1. They were primarily of B-cell origin and histologically classified mainly as large B-cell type (68%); T-cell lymphomas were rare (8%). EBV infection was observed in 14% of the B-cell lymphomas, an incidence rate higher than that reported in studies of B-cell lymphomas not located in the oral cavity but not as high as that observed in pleomorphic T-cell lymphomas (all sites, 36%) or nasal cavity T-cell lymphomas (nearly 100%). Interestingly, EBV proliferation did not correlate with expression of either Bcl-2 or p53.

p53 Mutations in nasal natural killer/T-cell lymphoma from Mexico: association with large cell morphology and advanced disease

Nasal NK/T-cell lymphoma is a unique form of lymphoma highly associated with Epstein-Barr virus, and with a characteristic geographic distribution. Recently, we showed that p53 is overexpressed in a high percentage of nasal NK/T-cell lymphomas. The aim of this study was to analyze the status of the p53 gene, and correlate it with the expression of p53 protein and its downstream target, the cyclin-dependent kinase inhibitor p21, in a series of 25 cases of well-characterized nasal NK/T-cell lymphoma from Mexico. The highly conserved exons 5 to 8 of the p53 gene were amplified by polymerase chain reaction and screened for mutations by denaturing high-pressure liquid chromatography. Abnormal polymerase chain reaction products detected by denaturing high-pressure liquid chromatography and additional selected cases were sequenced. In addition, the incidence of loss of heterozygosity at the p53 locus was analyzed in 12 cases. Of the 25 patients, 17 were male and 8 female (M:F ratio, 2.1:1), with a median age of 43 years (range, 21 to 93 years). Morphologically, most of the cases were composed of a mixture of medium-sized cells and large transformed cells (21 cases), and four cases were composed exclusively of large transformed cells. Three different groups determined by p53 gene status and expression of p53 protein were identified: group 1 was p53 +/p53 mutated (five cases, all with p53 missense mutations). Morphologically, three of the five cases were composed of large cells. All five cases revealed overexpression of p53 in the majority of the tumor cells with a mean of 86%. Unexpectedly, three of these cases also showed overexpression of p21. Four of the five patients presented with clinical stage IVB and died with disease. Group 2 was p53+/p53 wild-type (10 cases). Histologically, nine cases were of the mixed type, and one of the large cell type. The percentage of p53 overexpressing cells was lower than in the previous group with a mean of 23%. p21 was positive in 7 of the 10 cases. Six patients in this group presented with clinical stages I to II and four patients with advanced disease (stage III and IV). Five patients are alive 12 to 120 months later (mean, 24 months), three with no evidence of disease. Group 3 was p53-/p53 wild-type (10 cases). All cases showed mixed cell morphology. p21 was positive in 5 of 10 cases. Four patients presented with clinical stage I to II and six patients with advanced disease. Four patients are alive with no evidence of disease 9 to 60 months later (mean, 10 months). Overall, p53 mutations were present in 24% (5 of 21) of the evaluable cases, all of them overexpressing p53 in the majority of tumor cells. Cases with p53 mutations were associated with large cell morphology (P = 0.0162) and presented more often with advanced stage disease. Loss of heterozygosity at chromosome 17p was found only in 2 of the 12 (17%) cases investigated, both cases showed p53 mutations of the remaining allele. P21 overexpression (60% of cases) is frequent in nasal NK/T-cell lymphoma and seems to be independent of p53 gene status. The overexpression of p53 and p21, independent of p53 mutations, although as yet not clear, might be the result of Epstein-Barr virus infection, and warrants further investigation.