Characterization of EBV infection and NK subpopulations at the site of viral entry and reactivation in pediatric patients

FERRESSINI GERPE N; A VISTAROP; COHEN M; CALDIROLA MS; GAILLARD, I.; DE MATTEO, E.; M V PRECIADO; CHABAY P

Congreso; 28th European Congress of Clinical Microbiology and Infectious Diseases; 2018

Several studies demonstrated the key role of NK cells in the control of early infection and EBV-mediated transformation in children from developed countries. Our aim was, in pediatric patients from a developing population, to characterize EBV infection in relation to NK cell subsets at the tonsils, site of viral entry and reactivation.We analyzed 32 patients (2-15 years, median 5) undergoing tonsillectomy. EBV primary infection, reactivation or carrier status was defined by Anti-EBV VCA-IgM, VCA-IgG, Anti-EA-IgG and Anti-EBNA1 IgG. Viral load was measured by real rime PCR. Viral antigen expression was assessed by Immunohistochemistry (IHC) for LMP1, EBNA2 and BMRF1, and EBERS in situ Hybridization (ISH). CD56, CD16, GRANZIME B (GrB), and IFN IHC (expressed as positive cells/mm2) was performed to characterize NK cells. CD3, CD56, CD16, NKG2A and NKG2D NK subsets were identified in 13 patients by Flow Cytometry (FC). Eighteen primary infected patients,11 healthy carriers, 3 patients with viral reactivation and none EBV-seronegative patients were described. No significant differences regarding age or viral load between groups were demonstrated (p> 0.05). In primary infected patients, there was a negative correlation between age and viral load (r=0.5, p=0.0335). EBV-infected cells showed Latency I or II patterns, in all patients (p>0.05). CD56+ and IFN+ cells correlated between them (r=0.7, p=0.002) and with viral load (r= 0.5, p=0.0188; r=0.5 p=0.0228, respectively). Neither statistical differences in NK subsets in the 3 groups by FC nor a correlation between NK cell subsets numbers with viral load was established (p>0,05). In adults, symptomatic EBV primary infection display high viral load, latency III and lytic antigen expression, while low viral inoculum, restricted expression of EBV latent and lytic proteins was found in our 3 groups, maybe related to the lack of symptoms. Lower viral load in older children may reflect a recruitment of immune cells to control EBV infection at the site of viral entry. The prevalence of IFN- producing NK cells in tonsils might be involved in restriction of EBV viral load. The lack of NKG2A+NKG2D+ NK cells prevalence in our primarily infected patients could be related to increased susceptibly to develop EBV-associated lymphomas.