M1 Macrophage Polarization Prevails in Epstein-Barr Virus-Infected Children in an Immunoregulatory 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-ß, for M2. In the context of pediatric Epstein Barr virus (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-ß 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 Epstein Barr virus (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, given that M1 polarization pattern prevails, but in a regulatory environment.

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.

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.