Epidemiological presentation of EBV infection and characterization of NK subpopulations in the tonsils of pediatric patients compared with non-infected patients

Abstract

Several studies demonstrated the keyrole of NK cells in the control of early infection and EBVmediated transformation in children from developed countries. Therefore, our aim wasto characterizeEBV infectionin relation to NK cell subsets at the tonsils, site of viral entry and reactivation, inchildren from Argentina.We analyzed 76 patients (1-15 years, median 5) undergoing tonsillectomy. EBV primary infection(PI), reactivation (R), carrier (HC), or non-infected (NI) status was defined by serology. Viral load(VL) was evaluated by qPCR.Viral antigen expression was assessed by Immunohistochemistry(IHC) for LMP1, LMP2A, EBNA2 and BMRF1, and byEBERS in situ Hybridization (ISH). CD56,CD16, IFNg and GrzB IHC (expressed as positive cells/mm2) was performed tocharacterize NKcells. CD3, CD56, CD16, NKG2A and NKG2DNK subsets were identifiedin 44patients by FlowCytometry (FC). EBV typification was performed using primers directed against EBNA3C gene.Twenty-three PI patients,38HC,10 R patients and 5 NI patients were discriminated. No significantdifferences regarding age and VL among groups were demonstrated(p> 0.05) even though PI patientshad a higher VL mean. Unexpectedly, latency III pattern was observed exclusively in HC (p=0.0342,X2 test). CD56+ and IFNg+ cells by IHC displayed a positive correlation between them in the wholeseries (r=0.3009, p=0,0256) and specifically in PI (r=0.5298, p=0.0163). FC analysis revealed nospecific NK cell population in the three groups of EBV- infected patients (p>0.05), while a negativecorrelation between CD56+ and VL in all patients (r=-0,6623, p=0.005) and particularly in PI (r=-0,6623, p=0.005) was proved. In PI we observed correlation between age and NKG2A+NKG2D+NK cells (r=0,6685, p=0.0245).Regarding EBV types in cases with good quality DNA, EBV1 was prevalent in the whole series,given that 19 patients were positive for EBV-1, 6 for EBV-2 and one PI patient was co- infected,moreover, EBV1 was statistically distributed in patients younger than 10 years (p=0.0468, Fisherexact test)The low viral inoculum along with restricted expression of EBV latent and lytic proteins was foundin PI, maybe related to the lack of symptoms. Even though no specific NK subpopulation wasdescribed, IFNg- producing NK cells may be involved the control of viral infection in all EBV-infectedpatients.