Detection of Epstein–Barr virus in children's adenoids by in situ hybridization

Abstract

Adenoidal hypertrophy is the most frequent cause of superior airway obstruction in children. As a part of Waldeyer's ring, adenoids play an important immunological role during childhood. Although this tissue serves as a defense against bacteria, viruses, and foreign bodies, it may present infections (adenoiditis). Sometimes adenoid increases in size due to immune response, allergic reaction, or an unknown mechanism. When the reason of increase is unknown, the term hypertrophy or idiopathic benign hyperplasia (IBH) is used. Among viral infections, Epstein–Barr virus (EBV) infection stands out. It is much more frequent in children than expected and can also be responsible for adenoidal hypertrophy. Primary infection by EBV occurs in early childhood, and is characterized by symptoms of the common cold and may be clinically silent. EBV infection has as a characteristic period of latency, and involves lymphoproliferation in the tissues. Frequently, an IBH can actually be caused by EBV. The purpose of this study was to detect the presence of EBV in adenoids of young and older children using in situ hybridization (ISH) to assess the possible influence of EBV in adenoidal hypertrophy. We selected children from 1 to 13 years old in two otorhinolaryngology services (private and public) who underwent adenoidectomy due to adenoidal hypertrophy (AH). We divided them into two age groups: 21 children aged between 12 and 24 months old (mean: 18 months), and 50 children aged between 25 months and 13 years old (mean: 6.6 years). After surgery, adenoids were fixed in formalin at 10% and processed for ISH techniques. We used Novocastra probes EBER. Rhinopharynx carcinoma was used as positivity control. In the first group of younger children, there were seven positive cases for EBV (33%), and in the second group, there were 36 positive cases for EBV (72%). In all cases, 61% was positive for EBV: 83% mildly positive, 8.5% moderately positive, and 8.5% strongly positive for EBV (number of infected lymphocytes). EBV has a tropism through the rhinopharynx and oral cavity, and our study enabled us to assess EBV frequency in the adenoids, and also to infer that children over 25 months old present a greater chance of being infected by EBV.