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

Infectious mononucleosis complicated by transitory Epstein-Barr virus infection of T and natural killer cells

Epstein-Barr virus (EBV) typically infects B cells in infectious mononucleosis (IM), but a rare case shows EBV infection in T cells. Seven cases of lymphoproliferative disorder caused by EBV-positive cytotoxic T/natural killer (NK) cell proliferation in the lymph nodes, termed IM with transient EBV infection of T and NK cells (EBV + T/NK cells in IM), are reported here. The purpose of the study is to describe clinicopathological features of EBV + T/natural killer (NK) cells in IM of the lymph node. We retrospectively analysed seven cases of Chinese children and young people adults with EBV + T/NK cells in IM. We used morphological observation, immunohistochemical staining, EB virus in situ hybridisation detection, and analysis of T-cell receptor gene rearrangement. The patients were healthy prior to illness, experiencing sudden onset occurring in all the patients, with high fever as the first symptom, followed by lymphadenopathy and hepatosplenomegaly. Diagnosis occurred < 1.5 months of symptom onset. Most lymphocytes in lesions expressed CD3 and Granzyme B or TIA-1 and lacked CD5. CD56 was expressed in numerous cells in 5 of the 7 cases. EBV-encoded RNA (EBER) was detected in medium-to-large-sized cells (50-100 cells per cell/high-power field). T-cell receptor (TCR) gene rearrangement was seen in six cases, with monoclonal rearrangement in four cases. Treatment was conservative treatment but not chemotherapy. Four received anti-HLH therapy and others anti-inflammatory treatment. All patients survived with relapse after long-term clinical observation and follow-up. EBV + T/NK cells in IM can elicit malignant features that mimic T/NK-cell lymphoma pathologically and benign features mimicking IM clinically. These findings indicate that EBV + T/NK cells in IM could serve as valuable diagnosis. Additional clinical information, including age of onset (children and young people), nature of onset (sudden), disease course (short), symptoms (systemic), EBV infection status (acute), and lymph node involvement, is crucial for accurate diagnosis and prognostic evaluation.

EBV infected cells in the multiple sclerosis brain express PD-L1: How the virus and its niche may escape immune surveillance

The presence of EBV infected B cells in postmortem multiple sclerosis (MS) brain tissue suggests immune evasion strategies. Using immunohistochemical techniques we analysed the expression of the immune checkpoint molecule PD-L1 and its receptor PD-1 in MS brains containing B cell-enriched perivascular infiltrates and meningeal follicles, a major EBV reservoir. PD-1 and PD-L1 immunoreactivities were restricted to CNS-infiltrating immune cells. PD-L1 was expressed on B cells, including EBV infected B cells, while PD-1 was expressed on many CD8+ T cells, including EBV-specific CD8+ T-cells, and fewer CD4+ T cells. PD-L1+ cells and EBV infected cells were in close contact with PD-1+ T cells. PD-L1 expressed by EBV infected B cells could favour local immune evasion leading to EBV persistence and immunopathology in the MS brain.

The first autopsy case of Epstein-Barr virus-positive marginal zone lymphoma that deteriorated after COVID-19 vaccination

This is the first autopsy case of Epstein-Barr virus-positive marginal zone lymphoma (EBV + MZL) with an other iatrogenic immunodeficiency-associated lymphoproliferative disorders (LPD) (methotrexate [MTX]-associated LPD) that deteriorated after the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. This case had a unique immunophenotype. A 71-year-old female patient with rheumatoid arthritis receiving MTX presented with fatigue 1 week after the SARS-CoV-2 vaccination. She was hospitalized due to hepatorenal dysfunction and pancytopenia. Computed tomography revealed systemic lymphadenopathy. Her physical condition deteriorated, and the patient died. The autopsy revealed systemic lymphadenopathy comprising medium-sized atypical lymphocytes and scattered Hodgkin/Reed-Sternberg (H/RS)-like cells. An immunohistochemical examination showed that atypical lymphocytes were positive for CD79a and MUM-1 and some were positive for CD20 and IRTA-1. H/RS-like cells were immunoreactive for CD30 and CD15 and ringed by T cells. Both cell types were positive for EBV-encoded small RNA. The majority of H/RS-like cells were positive for CD20, whereas a small number of CD3-positive cells were admixed. We herein presented the first autopsy case of EBV + MZL that deteriorated after the SARS-CoV-2 vaccination.

Expression of EBV-encoded genes in children with asymptomatic infection detected by sensitive methods

Epstein-Barr virus (EBV) is an usually harmless virus whose oncogenic properties in vitro are related to its ability to transform lymphoid cells, and, in consequence, it can be associated with lymphomas. Since a few studies detected EBV presence in supposedly EBV-negative lymphomas, our aim was to evaluate EBV presence by sensitive gene expression assays in the tonsils from healthy pediatric donors from a region with high incidence of EBV-associated lymphomas. EBERs transcripts were detected by View RNA ISH in all cases, even in cases assessed negative by widely used in situ hybridization. The presence of LMP1 transcripts was proved in 93% of cases, co-expressed with EBNA2 in 30%. In this study, evidence for the expression of different latent and lytic viral genes in a population of young age of primary infection, detected with more sensitive methods, in particular at the germinal center, where most EBV-associated lymphomas originate, was provided.

Contribution of the Epstein-Barr virus to the oncogenesis of mature T-cell lymphoproliferative neoplasms

EBV is a lymphotropic virus, member of the Herpesviridae family that asymptomatically infects more than 90% of the human population, establishing a latent infection in memory B cells. EBV exhibits complex survival and persistence dynamics, replicating its genome through the proliferation of infected B cells or production of the lytic virions. Many studies have documented the infection of T/NK cells by EBV in healthy individuals during and after primary infection. This feature has been confirmed in humanized mouse models. Together these results have challenged the hypothesis that the infection of T/NK cells per se by EBV could be a triggering event for lymphomagenesis. Extranodal NK/T-cell lymphoma (ENKTCL) and Epstein-Barr virus (EBV)-positive nodal T- and NK-cell lymphoma (NKTCL) are two EBV-associated lymphomas of T/NK cells. These two lymphomas display different clinical, histological and molecular features. However, they share two intriguing characteristics: the association with EBV and a geographical prevalence in East Asia and Latin America. In this review we will discuss the genetic characteristics of EBV in order to understand the possible role of this virus in the oncogenesis of ENKTCL and NKTCL. In addition, the main immunohistological, molecular, cytogenetic and epigenetic differences between ENKTCL and NKTCL will be discussed, as well as EBV differences in latency patterns and other viral molecular characteristics.

Cytotoxic peripheral T-cell lymphomas and EBV-positive T/NK-cell lymphoproliferative diseases: emerging concepts, recent advances, and the putative role of clonal hematopoiesis. A report of the 2022 EA4HP/SH lymphoma workshop

Cytotoxic peripheral T-cell lymphomas and EBV-positive T/NK-cell lymphoproliferative diseases were discussed at the 2022 European Association for Haematopathology/Society for Hematopathology lymphoma workshop held in Florence, Italy. This session focused on (i) primary nodal EBV-positive T and NK-cell lymphomas (primary nodal-EBV-TNKL), (ii) extranodal EBV-positive T/NK lymphoproliferative diseases (LPD) in children and adults, (iii) cytotoxic peripheral T-cell lymphomas, NOS (cPTCL-NOS), EBV-negative, and (iv) miscellaneous cases. Primary nodal-EBV-TNKL is a newly recognized entity which is rare, aggressive, and associated with underlying immune deficiency/immune dysregulation. All cases presented with lymphadenopathy but some demonstrated involvement of tonsil/Waldeyer's ring and extranodal sites. The majority of tumors are of T-cell lineage, and the most frequent mutations involve the epigenetic modifier genes, such as TET2 and DNMT3A, and JAK-STAT genes. A spectrum of EBV-positive T/NK LPD involving extranodal sites were discussed and highlight the diagnostic challenge with primary nodal-EBV-TNKL when these extranodal EBV-positive T/NK LPD cases demonstrate predominant nodal disease either at presentation or during disease progression from chronic active EBV disease. The majority of cPTCL-NOS demonstrated the TBX21 phenotype. Some cases had a background of immunosuppression or immune dysregulation. Interestingly, an unexpected association of cPTCL-NOS, EBV-positive and negative, with TFH lymphomas/LPDs was observed in the workshop cases. Similar to a published literature, the genetic landscape of cPTCL-NOS from the workshop showed frequent mutations in epigenetic modifiers, including TET2 and DNMT3A, suggesting a role of clonal hematopoiesis in the disease pathogenesis.

Extranodal NK-/T-cell lymphoma, nasal type: what advances have been made in the last decade?

Extranodal NK-/T-cell lymphoma (ENKTCL) is a rare and highly aggressive malignancy with significant racial and geographic variations worldwide. In addition to the formerly "nasal-type" initial description, these lymphomas are predominantly extranodal in origin and typically cause vascular damage and tissue destruction, and although not fully understood, Epstein-Barr virus (EBV) has an important role in its pathogenesis. Initial assessment must include a hematopathology review of representative and viable tumor areas without necrosis for adequate immunohistochemistry studies, including EBV-encoded small RNA (EBER) in situ hybridization (ISH). Positron emission tomography with 18-fluorodeoxyglucose (¹⁸F-FDG-PET/CT) for accurate staging is essential, and most patients will have localized disease (IE/IIE) at diagnosis. Apart from other T-cell malignancies, the best treatment even for localized cases is combined modality therapy (chemotherapy plus radiotherapy) with non-anthracycline-based regimens. For advanced-stage disease, l-asparaginase-containing regimens have shown improved survival, but relapsed and refractory cases have very poor outcomes. Nowadays, even with a better understanding of pathogenic pathways, up-front therapy is completely based on chemotherapy and radiotherapy, and treatment-related mortality is not low. Future strategies targeting signaling pathways and immunotherapy are evolving, but we need to better identify those patients with dismal outcomes in a pre-emptive way. Given the rarity of the disease, international collaborations are urgently needed, and clinical trials are the way to change the future.

Differences in the Tumor Microenvironment of EBV-Associated Gastric Cancers Revealed Using Single-Cell Transcriptome Analysis

Epstein-Barr virus (EBV) is a gamma-herpesvirus associated with nearly 10% of gastric cancers (GCs). These EBV-associated GCs (EBVaGCs) are molecularly, histopathologically, and clinically distinct from EBV-negative GCs (EBVnGCs). While viral genes in EBVaGCs contribute to the carcinogenesis process, viral proteins also represent foreign antigens that could trigger enhanced immune responses compared to EBVnGCs. Despite prior investigations of the EBVaGC tumor microenvironment (TME), the cellular composition has not been thoroughly explored. In this study, cellular subpopulations overrepresented in EBVaGCs were identified and molecularly characterized. Genes consistently expressed across both bulk tumor and single-cell RNA sequencing data were highlighted, with the expression across the identified cellular subpopulations analyzed. As expected, based on existing histopathological analysis, EBVaGC is characterized by abundant lymphocytic infiltration of the stroma. Our molecular analysis identified three unique immune cell subpopulations in EBVaGC: T and B cells expressing high levels of proliferation markers and B cells expressing T cell features. The proliferating T cell cluster also expressed markers of follicular T helper cells. Overall, EBVaGC also exhibited unique features indicative of a higher inflammatory response. These substantial differences within the TME suggest that further detailed exploration of the cellular composition of EBVaGCs is needed, which may identify cellular subpopulations and phenotypes associated with patient outcomes.

T cell-mediated immunity during Epstein-Barr virus infections in children

Epstein-Barr virus (EBV) infection is extremely common worldwide, with approximately 90% of adults testing positive for EBV antibodies. Human are susceptible to EBV infection, and primary EBV infection typically occurs early in life. EBV infection can cause infectious mononucleosis (IM) as well as some severe non-neoplastic diseases, such as chronic active EBV infection (CAEBV) and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which can have a heavy disease burden. After primary EBV infection, individuals develop robust EBV-specific T cell immune responses, with EBV-specific CD8⁺ and part of CD4⁺ T cells functioning as cytotoxic T cells, defending against virus. Different proteins expressed during EBV's lytic replication and latent proliferation can cause varying degrees of cellular immune responses. Strong T cell immunity plays a key role in controlling infection by decreasing viral load and eliminating infected cells. However, the virus persists as latent infection in EBV healthy carriers even with robust T cell immune response. When reactivated, it undergoes lytic replication and then transmits virions to a new host. Currently, the relationship between the pathogenesis of lymphoproliferative diseases and the adaptive immune system is still not fully clarified and needs to be explored in the future. Investigating the T cell immune responses evoked by EBV and utilizing this knowledge to design promising prophylactic vaccines are urgent issues for future research due to the importance of T cell immunity.

Concordance of adenosine deaminase with immunoglobulins and lymphocyte subsets in EBV-related diseases

BACKGROUND

Clinical manifestations of Epstein-Barr virus (EBV) infection are diverse. This study aimed to explore the immune response in EBV-related diseases and the correlation between immune cells and adenosine deaminase (ADA) levels.

METHODS

This study was conducted at the Children's Hospital of Soochow University. In total, 104 patients with EBV-associated respiratory tract infection (EBV-RTI), 32 patients with atypical EBV infection, 54 patients with EBV-associated infectious mononucleosis (IM1, with normal alanine aminotransferase [ALT] levels), 50 patients with EBV-IM2 (with elevated ALT levels), 50 patients with acute respiratory infection (AURI, with other pathogens), and 30 healthy controls were enrolled in this study. Indicators of ADA, immunoglobulins (Igs), and lymphocyte subsets were analyzed for EBV-related diseases.

RESULTS

Differences in the white blood cell, lymphocyte counts, ADA levels, IgA, IgG and IgM titers, percentage of CD3⁺, CD3⁺CD4⁺, CD3⁺CD8⁺, CD16⁺CD56⁺, CD3^-CD19⁺, and CD19⁺CD23⁺ lymphocytes, and CD4⁺/CD8⁺ ratio between EBV-related disease groups were all statistically significant (P < 0.01). ADA levels in the EBV-related disease groups were significantly higher than those in the control group (P < 0.01). The lymphocyte count, ADA levels, IgA and IgG titers, and percentage of CD3⁺ and CD3⁺CD8 + lymphocytes in the atypical EBV infection, EBV-IM1, and EBV-IM2 groups were significantly higher than those in the EBV-RTI, AUTI, and control groups (P < 0.01), whereas the percentage of CD3⁺CD4⁺, CD3^-CD19⁺, and CD19⁺CD23⁺ lymphocytes and CD4⁺/CD8⁺ ratio showed the opposite trend. ADA levels were consistent with and closely related to the viral load and cellular and humoral immunity in EBV-related diseases.

CONCLUSIONS

ADA levels, humoral immunity, and cellular immunity were diverse in EBV-related diseases, and ADA was closely related to Igs and lymphocyte subsets.

The value of bile acid spectrum in the evaluation of hepatic injury in children with infectious mononucleosis caused by Epstein Barr virus infection

Background

Infectious mononucleosis (IM) is an acute infectious disease, caused by Epstein-Barr virus (EBV) infection, which can invade various systemic systems, among which hepatic injury is the most common. In this study, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to detect serum bile acid spectrum in IM children quantitatively, and to investigate its role in the early assessment of hepatic injury.

Methods

This case-control study was conducted at Yuhuan People's Hospital. A total of 60 IM children and 30 healthy children were included in the study. Among 60 children with IM, 30 had hepatic injury, and 30 without hepatic injury. The clinical and laboratory data were analyzed, and the serum bile acid spectrum and lymphocyte subsets were evaluated in the three groups.

Results

There were statistically significant differences in cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), glycochenodeoxycholic acid (GCDCA), glycodeoxycholic acid(GDCA), glycolithocholic acid (GLCA), taurocholic acid (TCA), taurochenodeoxycholic acid (TCDCA), taurodeoxycholic acid (TDCA), ursodeoxycholic acid (UDCA), glycoursodeoxycholic acid (GUDCA), tauroursodeoxycholic acid(TUDCA), percentage of NK cells, CD4+ and CD8+ in IM hepatic injury group, without hepatic injury group, and the healthy control group (P < 0.05). The percentage of NK cells was positively correlated with TCA (P < 0.05); it was negatively correlated with CDCA, DCA, LCA, GCDCA, GDCA, GLCA, TDCA, UDCA, GUDCA, TUDCA (P < 0.05). CD4+ was positively correlated with CA, TCA and TCDCA (P < 0.05); it was negatively correlated with CDCA, DCA, LCA, GCDCA, GDCA, GLCA, TDCA, UDCA, GUDCA and TUDCA (P < 0.05). CD8+ was positively correlated with CDCA, DCA, LCA, GCDCA, GDCA, GLCA, TDCA, UDCA, GUDCA and TUDCA (P < 0.05); it was negatively correlated with CA, TCA and TCDCA (P < 0.05). ROC curve analysis showed that CD8+, GDCA and GLCA had high predictive value for hepatic injury in IM patients.

Conclusions

UPLC-MS/MS method can sensitively detect the changes in serum bile acid spectrum before hepatic injury in children with IM, which is helpful for early assessment of hepatic injury in children with IM. The changes in lymphocyte subsets in IM children are related to some bile acid subfractions, which may be related to IM hepatic injury.

PD-L1 is upregulated in CD163+ tonsillar macrophages from children undergoing EBV primary infection

Epstein-Barr Virus (EBV) is a tumor associated virus that modulates not only the infected cells but also innate and adaptive immunity. Macrophages play a key role in tumor development and progression. Particularly, the M2 phenotype (CD163) with anti-inflammatory activity contributes to a favorable microenvironment for tumor development while the M1 (CD68) proinflammatory phenotype contributes to a restrictive one. In the context of pediatric EBV infection, little is known about macrophage contribution to PD-L1 expression, a molecule involved in immune exhaustion. We studied tonsils of primary infected (PI), healthy carriers (HC), reactivated (R), and not infected (NI) pediatric patients. Positive correlations were demonstrated for CD68+PD-L1+ in R and for CD163+PD-L1+ only in PI. Furthermore, CD163+PD-L1+ cell numbers were higher than PD-L1+CD68+ in PI patients. In addition, a positive correlation between PD-L1+CD163+ cells and LMP1 viral latent protein was observed in PI patients, and a positive correlation between PD-L1+CD68+ cells and BMRF1 lytic antigen was demonstrated. A positive correlation between TGF-β and PD-L1 expression was demonstrated in HC patients. Our findings indicate that EBV's lytic and latent antigens might be regulating macrophages' PD-L1 expression, particularly in PI patients, whereas, surprisingly, only TGF-β could be related to total PD-L1 upregulation. Given the relevance of macrophages and the PD-1/PD-L1 pathway in tumor progression and survival, more studies in early EBV infection could help to develop EBV-associated tumor therapies.

How EBV Infects: The Tropism and Underlying Molecular Mechanism for Viral Infection

The Epstein-Barr virus (EBV) is associated with a variety of human malignancies, including Burkitt's lymphoma, Hodgkin's disease, nasopharyngeal carcinoma and gastric cancers. EBV infection is crucial for the oncogenesis of its host cells. The prerequisite for the establishment of infection is the virus entry. Interactions of viral membrane glycoproteins and host membrane receptors play important roles in the process of virus entry into host cells. Current studies have shown that the main tropism for EBV are B cells and epithelial cells and that EBV is also found in the tumor cells derived from NK/T cells and leiomyosarcoma. However, the process of EBV infecting B cells and epithelial cells significantly differs, relying on heterogenous glycoprotein-receptor interactions. This review focuses on the tropism and molecular mechanism of EBV infection. We systematically summarize the key molecular events that mediate EBV cell tropism and its entry into target cells and provide a comprehensive overview.

Epstein-Barr Virus Genome Deletions in Epstein-Barr Virus-Positive T/NK Cell Lymphoproliferative Diseases

The main target cells for Epstein-Barr virus (EBV) infection and persistence are B lymphocytes, although T and NK cells can also become infected. In this paper, we characterize the EBV present in 21 pediatric and adult patients who were treated in France for a range of diseases that involve infection of T or NK cells. Of these 21 cases, 5 pediatric patients (21%) and 11 adult patients (52%) were of Caucasian origin. In about 30% of the cases, some of the EBV genomes contain a large deletion. The deletions are different in every patient but tend to cluster near the BART region of the viral genome. Detailed investigation of a family in which several members have persistent T or NK cell infection by EBV indicates that the virus genome deletions arise or are selected independently in each individual patient. Genome sequence polymorphisms in the EBV in these T or NK cell diseases reflect the geographic origin of the patient and not a distinct type of EBV (the 21 cases studied included examples of both type 1 and type 2 EBV infection). Using virus produced from type 1 or type 2 EBV genomes cloned in bacterial artificial chromosome (BAC) vectors, we demonstrate infection of T cells in cord blood from healthy donors. Our results are consistent with transient infection of some T cells being part of normal asymptomatic infection by EBV in young children. IMPORTANCE EBV contributes to several types of human cancer. Some cancers and nonmalignant lymphoproliferative diseases involving T or NK cells contain EBV. These diseases are relatively frequent in Japan and China and have been shown sometimes to have deletions in the EBV genome in the disease cells. We identify further examples of deletions within the EBV genome associated with T or NK cell diseases, and we provide evidence that the virus genomes with these deletions are most likely selected in the individual cases, rather than being transmitted between people during infection. We demonstrate EBV infection of cord blood T cells by highly characterized, cloned EBV genomes and suggest that transient infection of T cells may be part of normal asymptomatic infection by EBV in young children.

Adenosine deaminase as a marker for the severity of infectious mononucleosis secondary to EBV in children

Background

Infectious mononucleosis, a common disease in children and young adults, is often accompanied by elevated transaminase levels and rarely, liver failure. This study aimed to determine whether adenosine deaminase is a marker of severity in children with infectious mononucleosis, especially those with elevated alanine transaminase levels.

Methods

This case-control study was conducted at the Children’s Hospital of Soochow University. A total of 104 children with infectious mononucleosis and 50 controls with other acute infections and fever, tonsillitis, or lymphadenitis, were enrolled in the study. Among the 104 children with infectious mononucleosis, 54 had normal alanine transaminase levels and 50 had elevated alanine transaminase levels. The children’s clinical and laboratory data were analyzed to assess the diagnostic value of adenosine deaminase in the three groups.

Results

The adenosine deaminase level in the infectious mononucleosis group was significantly higher than that in the control group (P < 0.001). The adenosine deaminase levels were highly correlated with lymphocyte count, CD3⁺CD8⁺ T cells (%), CD4⁺/CD8⁺ ratio, and CD3⁻CD19⁺ (%) (r > 0.7, P < 0.01). The sensitivity and specificity of adenosine deaminase in predicting children with infectious mononucleosis were 97.1% and 94.0%, respectively. Furthermore, multivariate regression analysis revealed that adenosine deaminase level was a risk factor for elevated alanine transaminase in children with infectious mononucleosis.

Conclusions

Adenosine deaminase may be a marker of the severity of infectious mononucleosis in children, and a predictor of elevated alanine transaminase in children with infectious mononucleosis.

Uncovering early events in primary Epstein-Barr virus infection using a rabbit model

Epstein-Barr virus (EBV) is an oncogenic herpesvirus implicated in the pathogenesis of several malignant and non-malignant conditions. However, a number of fundamental aspects about the biology of EBV and the mechanism(s) by which this virus induces pathology remain unknown. One major obstacle has been the lack of a suitable animal model for EBV infection. In this study, using our recently established rabbit model of EBV infection, we examined the early events following primary EBV infection. We show that, both immunocompetent and immunosuppressed animals were readily susceptible to EBV infection. However, immunosuppressed animals showed marked splenomegaly and widespread infection. Following EBV infection, the virus primarily targeted naïve IgM+, CD20+, CD21+ and CD79a+ B cells. Infected cells expressed varying sets of viral latent/lytic gene products. Notably, co-expression of latent and lytic proteins in the same cell was not observed. Infected cells in type 0/1 latency (EBERs+), were small and proliferating (Ki67+). By contrast, cells in type 2/3 latency (LMP1+), were large, non-proliferating (Ki-67-) and p53+. Although infected B-cells were widely present in splenic follicles, they did not express germinal center marker, BCL-6. Taken together, this study shows for the first time, some of the early events following primary EBV infection.

"M1 macrophage polarization prevails in EBV infected children in an immuneregulatory environment"

Macrophages can be polarized toward a proinflammatory phenotype (M1) (CD68+) or to an anti-inflammatory one (M2) (CD163+). Polarization can be triggered by cytokines such as IFN-γ for M1, or IL-10 and TGF-β, for M2. In the context of pediatric EBV infection, little is known about macrophage polarization in EBV primary or persistent infection. When studying tonsils of patients undergoing primary infection (PI), healthy carrier (HC), reactivation (R) and not infected (NI), M1 profile prevailed in all infection status. However, an increase in M2 cells was observed in those patients with broader expression of latency antigens, in particular EBNA2. Tonsils from primary infected patients showed an increased IL-10 expression, whereas, unexpectedly, TGF-β expression correlated with M1 marker. Furthermore, an inverse correlation was demonstrated between CD68 and IFN-γ. Therefore, in the context of asymptomatic infection in children, M1 macrophage polarization prevails, even in the presence of IL-10 and TGF-ꞵ immunomodulatory cytokines, and it might be independent from lymphomagenesis process. Our finding indicates that macrophages may have a significant plasticity in response to different types of extrinsic stimuli, and further studies are required to investigate M1 polarization under anti-inflammatory stimuli. Importance Most studies on EBV primary infection have been performed in adolescents and young adult populations with Infectious Mononucleosis (IM) in developed countries. Furthermore, studies related to macrophage polarization were assessed in EBV-associated lymphomas, but little is known about macrophage polarization in the context of primary infection at the site of viral entry and replication, the tonsils. Therefore, the aim of this study was to characterize macrophage response in children undergoing EBV primary or persistent infection, in order to enlighten the role of macrophages in viral pathogenesis, in a population with a high incidence of EBV-associated lymphomas in children younger than 10 years old. This study may contribute to explain, at least in part, the asymptomatic viral infection in children from an underdeveloped region, since M1 polarization pattern prevails, but in a regulatory environment.

Macromolecular Nanotherapeutics and Antibiotic Adjuvants to Tackle Bacterial and Fungal Infections

The escalating rise in the population of multidrug-resistant (MDR) pathogens coupled with their biofilm forming ability has struck the global health as nightmare. Alongwith the threat of aforementioned menace, the sluggish development of new antibiotics and the continuous deterioration of the antibiotic pipeline has stimulated the scientific community toward the search of smart and innovative alternatives. In near future, membrane targeting antimicrobial polymers, inspired from antimicrobial peptides, can stand out significantly to combat against the MDR superbugs. Many of these amphiphilic polymers can form nanoaggregates through self-assembly with superior and selective antimicrobial efficacy. Additionally, these macromolecular nanoaggregrates can be utilized to engineer smart antibiotic-delivery system for on-demand drug-release, exploiting the infection site's micoenvironment. This strategy substantially increases the local concentration of antibiotics and reduces the associated off-target toxicity. Furthermore, amphiphilc macromolecules can be utilized to rejuvinate obsolete antibiotics to tackle the drug-resistant infections. This review article highlights the recent developments in macromolecular architecture to design numerous nanostructures with broad-spectrum antimicrobial activity, their application in fabricating smart drug delivery systems and their efficacy as antibiotic adjuvants to circumvent antimicrobial resistance. Finally, the current challenges and future prospects are briefly discussed for further exploration and their practical application in clinical settings.

The role of EBV in haematolymphoid proliferations: emerging concepts relevant to diagnosis and treatment

Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus with >90% of the adult population worldwide harbouring latent infection. A small subset of those infected develop EBV-associated neoplasms, including a range of lymphoproliferative disorders (LPD). The diagnostic distinction of these entities appears increasingly relevant as our understanding of EBV-host interactions and mechanisms of EBV-driven lymphomagenesis improves. EBV may lower the mutational threshold for malignant transformation, create potential vulnerabilities related to viral alteration of cell metabolism and allow for improved immune targeting. However, these tumours may escape immune surveillance by affecting their immune microenvironment, limiting viral gene expression or potential loss of the viral episome. Methods to manipulate the latency state of the virus to enhance immunogenicity are emerging as well as the potential to detect so-called 'hit and run' cases where EBV has been lost. Finally, measurement of EBV DNA remains an important biomarker for screening and monitoring of LPD. Methods to distinguish EBV DNA derived from virions during lytic activation from latent, methylated EBV DNA present in EBV-associated neoplasms may broaden the utility of this testing, particularly in patients with compromised immune function. We highlight some of these emerging areas relevant to the diagnosis and treatment of EBV-associated LPD with potential applicability to other EBV-associated neoplasms.

Comparative analysis of post-transplant lymphoproliferative disorders after solid organ and hematopoietic stem cell transplantation reveals differences in the tumor microenvironment

Post-transplant lymphoproliferative disorders (PTLD) occur after solid organ transplantation (SOT) or hematopoietic stem cell transplantation (HCT) and are frequently associated with Epstein-Barr virus (EBV). Because of the complex immune setup in PTLD patients, the tumor microenvironment (TME) is of particular interest to understand PTLD pathogenesis and elucidate predictive factors and possible treatment options. We present a comparative study of clinicopathological features of 48 PTLD after HCT (n = 26) or SOT (n = 22), including non-destructive (n = 6), polymorphic (n = 23), and monomorphic (n = 18) PTLD and classic Hodgkin lymphoma (n = 1). EBV was positive in 35 cases (73%). A detailed examination of the TME with image analysis-based quantification in 22 cases revealed an inflammatory TME despite underlying immunosuppression and significant differences in its density and composition depending on type of transplant, PTLD subtypes, and EBV status. Tumor-associated macrophages (TAMs) expressing CD163 (p = 0.0022) and Mannose (p = 0.0016) were enriched in PTLD after HCT. Double stains also showed differences in macrophage polarization, with more frequent M1 polarization after HCT (p = 0.0321). Higher counts for TAMs (CD163 (p = 0.0008) and cMaf (p = 0.0035)) as well as in the T cell compartment (Granzyme B (p = 0.0028), CD8 (p = 0.01), and for PD-L1 (p = 0.0305)) were observed depending on EBV status. In conclusion, despite the presence of immunosuppression, PTLD predominantly contains an inflammatory TME characterized by mostly M1-polarized macrophages and cytotoxic T cells. Status post HCT, EBV positivity, and polymorphic subtype are associated with an actively inflamed TME, indicating a specific response of the immune system. Further studies need to elucidate prognostic significance and potential therapeutic implications of the TME in PTLD.

Chronic Active Epstein-Barr Virus Infection: Is It Immunodeficiency, Malignancy, or Both?

Simple Summary

Chronic active Epstein–Barr virus (EBV) infection (CAEBV) is a rare syndrome of unknown etiology characterized by prolonged infectious mononucleosis-like symptoms and proliferation of EBV-infected T and/or natural killer cells. CAEBV has been primarily reported in East Asia and Latin America, suggesting a genetic predisposition in its pathogenesis. The clinical course of CAEBV is heterogeneous ranging from an indolent and occasionally self-limiting disease to an aggressive and fatal condition, but its prognosis is generally poor. This heterogeneous clinical picture does not suggest a simple etiology for the syndrome. Clinicopathological investigations of CAEBV suggest that it has aspects of both malignant neoplasm and immunodeficiency. This article summarizes the latest findings on CAEBV and discusses critical unsolved questions regarding its pathogenesis and disease concept.

Abstract

Chronic active Epstein–Barr virus (EBV) infection (CAEBV) is a rare syndrome characterized by prolonged infectious mononucleosis-like symptoms and elevated peripheral blood EBV DNA load in apparently immunocompetent persons. CAEBV has been primarily reported in East Asia and Latin America, suggesting a genetic predisposition in its pathogenesis. In most cases of CAEBV, EBV induces proliferation of its unusual host cells, T or natural killer (NK) cells. The clinical course of CAEBV is heterogeneous; some patients show an indolent course, remaining in a stable condition for years, whereas others show an aggressive course with a fatal outcome due to hemophagocytic lymphohistiocytosis, multiple organ failure, or progression to leukemia/lymphoma. The pathogenesis of CAEBV is unclear and clinicopathological investigations suggest that it has aspects of both malignant neoplasm and immunodeficiency. Recent genetic analyses of both viral and host genomes in CAEBV patients have led to discoveries that are improving our understanding of the nature of this syndrome. This article summarizes the latest findings on CAEBV and discusses critical unsolved questions regarding its pathogenesis and disease concept.

CD21 (Complement Receptor 2) Is the Receptor for Epstein-Barr Virus Entry into T Cells

Epstein-Barr virus (EBV) is associated with a number of T-cell diseases, including some peripheral T-cell lymphomas, hemophagocytic lymphohistiocytosis, and chronic active EBV disease. The tropism of EBV for B cells and epithelial cell infection has been well characterized, but infection of T cells has been minimally explored. We have recently shown that the EBV type 2 (EBV-2) strain has the unique ability to infect mature T cells. Utilizing an ex vivo infection model, we sought to understand the viral glycoprotein and cellular receptor required for EBV-2 infection of T cells. Here, using a neutralizing-antibody assay, we found that viral gp350 and complement receptor 2 (CD21) are required for CD3⁺ T-cell infection. Using the HB5 anti-CD21 antibody clone but not the Bly-4 anti-CD21 antibody clone, we detected expression of CD21 on both CD4⁺ and CD8⁺ T cells, with the highest expression on naive CD4 and CD8⁺ T-cell subsets. Using CRISPR to knock out CD21, we demonstrated that CD21 is necessary for EBV entry into the Jurkat T-cell line. Together, these results indicate that EBV uses the same viral glycoprotein and cellular receptor for both T- and B-cell infection.IMPORTANCE Epstein-Barr virus (EBV) has a well-described tropism for B cells and epithelial cells. Recently, we described the ability of a second strain of EBV, EBV type 2, to infect mature peripheral T cells. Using a neutralizing antibody assay, we determined that EBV uses the viral glycoprotein gp350 and the cellular protein CD21 to gain entry into mature peripheral T cells. CRISPR-Cas9 deletion of CD21 on the Jurkat T-cell line confirmed that CD21 is required for EBV infection. This study has broad implications, as we have defined a function for CD21 on mature peripheral T cells, i.e., as a receptor for EBV. In addition, the requirement for gp350 for T-cell entry has implications for EBV vaccine studies currently targeting the gp350 glycoprotein to prevent EBV-associated diseases.

Fine needle cytology features of an atypical presentation of infectious mononucleosis

Infectious mononucleosis (IM) is a very common disease, and although in most instances, the patient develops an asymptomatic infection, other patients progress into an array of signs and symptoms that tend to be characteristic of the pathological process, guiding the clinician into choosing the right laboratory examinations under the suspicion of this illness. The most common symptoms are pharyngitis, lymphadenopathies and pyrexia, and the probabilities to develop this mononucleosis triad become greater with age. In other instances, IM can be a challenging disease to diagnose, mainly because the patient debuts with unusual symptoms such as nausea, skin eruptions, diarrhea and epigastric discomfort. The aim of the present article is to report the case of a 21-year-old female with a reactivation of IM, developing only multiple, asymptomatic lymph node enlargements in the head and neck region, showing no other sign or symptom.

Distinctive EBV infection characteristics in children from a developing country

BACKGROUND

In developing countries, Epstein-Barr virus (EBV) infection is mostly asymptomatic in early childhood. EBV persistence may lead to different malignancies, such as B cell derived lymphomas. In Argentina, most children are seropositive at three years and an increased association between EBV and lymphoma was proved in children under 10 years old by our group.

OBJECTIVE

Our aim was to characterize EBV infection at the site of entry and reactivation of viral infection -the tonsils- in order to better understand the mechanism of viral persistence in pediatric patients.

METHODS

A cohort of 54 patients was described. We assessed specific antibodies profiles in sera; viral proteins presence by IHC on FFPE samples and EBV type from fresh tissue.

RESULTS

EBV type 1 was prevalent, mostly in the youngest patients. Asymptomatic primary infected patients presented higher viral loads and Latency 0/I or II patterns, whereas the Latency III pattern was observed mostly in healthy carriers. There were no differences between groups in the expression of viral lytic antigens. This study discloses new features in patients undergoing primary infection from a developing population. Low viral inoculum and restricted viral antigen expression may be responsible for the lack of symptoms in children from our country.

Differences in Epstein-Barr Virus Characteristics and Viral-Related Microenvironment Could Be Responsible for Lymphomagenesis in Children

In Argentina, Epstein-Barr virus (EBV) presence is associated with Hodgkin lymphoma (HL) in patients younger than 10 years, suggesting a relationship between low age of EBV infection and HL. Given that HL is derived from germinal centers (GC), our aim was to compare EBV protein expression and microenvironment markers between pediatric HL patients and EBV+GC in children. Methods: EBV presence and immune cell markers were assessed by in situ hybridization and immunohistochemistry (IHC). Results: Viral latency II pattern was proved in all HL patients and in 81.8% of EBV+ tonsillar GCs. LMP1 and LMP2 co-expression were proved in 45.7% HL cases, but only in 7.7% EBV+ GC in pediatric tonsils. An increase in CD4+, IL10, and CD68+ cells was observed in EBV+ GC. In pediatric HL patients, only the mean of IL10+ cells was statistically higher in EBV+ HL. Conclusions: Our findings point us out to suggest that LMP1 expression may be sufficient to drive neoplastic transformation, that an immune regulatory milieu counteracts cytotoxic environment in EBV-associated Hodgkin lymphoma, and that CD4+ and CD68+ cells may be recruited to act in a local collaborative way to restrict, at least in part, viral-mediated lymphomagenesis in tonsillar GC.

The Global Landscape of EBV-Associated Tumors

Epstein-Barr virus (EBV), a gamma-1 herpesvirus, is carried as a life-long asymptomatic infection by the great majority of individuals in all human populations. Yet this seemingly innocent virus is aetiologically linked to two pre-malignant lymphoproliferative diseases (LPDs) and up to nine distinct human tumors; collectively these have a huge global impact, being responsible for some 200,000 new cases of cancer arising worldwide each year. EBV replicates in oral epithelium but persists as a latent infection within the B cell system and several of its diseases are indeed of B cell origin; these include B-LPD of the immunocompromised, Hodgkin Lymphoma (HL), Burkitt Lymphoma (BL), Diffuse Large B cell Lymphoma (DLBCL) and two rarer tumors associated with profound immune impairment, plasmablastic lymphoma (PBL) and primary effusion lymphoma (PEL). Surprisingly, the virus is also linked to tumors arising in other cellular niches which, rather than being essential reservoirs of virus persistence in vivo, appear to represent rare cul-de-sacs of latent infection. These non-B cell tumors include LPDs and malignant lymphomas of T or NK cells, nasopharyngeal carcinoma (NPC) and gastric carcinoma of epithelial origin, and leiomyosarcoma, a rare smooth muscle cell tumor of the immunocompromised. Here we describe the main characteristics of these tumors, their distinct epidemiologies, histological features and degrees of EBV association, then consider how their different patterns of EBV latency may reflect the alternative latency programmes through which the virus first colonizes and then persists in immunocompetent host. For each tumor, we discuss current understanding of EBV's role in the oncogenic process, the identity (where known) of host genetic and environmental factors predisposing tumor development, and the recent evidence from cancer genomics identifying somatic changes that either complement or in some cases replace the contribution of the virus. Thereafter we look for possible connections between the pathogenesis of these apparently different malignancies and point to new research areas where insights may be gained.