HHV-6 infection of tonsils and adenoids in children with hypertrophy and upper airway recurrent infections.
OBJECTIVE
Human herpes virus 6 (HHV-6), the agent of a self-limiting exanthematic disease in childhood, persists in a silent state in the secondary lymphoid organs and the reactivation is characterized by HHV-6-induced inflammatory cytokines. This study investigates the possible etiological role of HHV-6 in children affected by tonsil and adenoid hypertrophy.


METHODS
55 tonsils, 80 adenoids fresh tissues and 74 blood samples were collected from 80 children (mean age 4.8 years, 43.5% female) undergoing elective tonsillectomy and/or adenoidectomy for tissue hypertrophy. Moreover, patients with <5 years old documented upper airway recurrent infections not related to relapsing of acute tonsillitis. Specific IgG antibodies and virus detection (by PCR, variant A/B enzymatic genotyping and real-time PCR) were performed.


RESULTS
In our series, HHV-6 seroprevalence was tested at 50%. HHV-6 variant B was the unique strain finding in 25% of adenoids, in 12.7% of tonsils and in 4% of peripheral blood mononuclear cells (PBMCs). HHV-6-B was prevalent in tonsils of children affected by upper airway infections (17.8% vs 7.4%) while the adenoids represented the more frequent reservoir (30.7% vs 19.5%) in patients with hypertrophy. HHV-6 viral load was low, ranging from 80 to 600 copies/10(6) cells suggesting a latent/persistent phase of infection.


CONCLUSIONS
These results reinforce the role of the secondary lymphoid organs as an important reservoir for HHV-6B. Nevertheless, infection of lymphoid cells, sustained by a low level of replication, could be sufficient to increase the local injury through an autologous mechanism of inflammation.
Comar
Manola
M
Department of Public Medicine Sciences, UCO Hygiene and Preventive Medicine, University of Trieste and IRCCS Burlo Garofolo, Via dell'Istria no. 65/1, 34100 Trieste, Italy. comar@burlo.trieste.it
Grasso
Domenico
D
dal Molin
Gianna
G
Zocconi
Elisabetta
E
Campello
Cesare
C
D000234:Adenoids / Q000473:pathology* / Q000821:virology*; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006566:Herpesviridae Infections / Q000235:genetics / Q000276:immunology / Q000821:virology*; D015654:Herpesvirus 6, Human / Q000302:isolation & purification*; D006801:Humans; D006984:Hypertrophy / Q000473:pathology / Q000821:virology; D007074:Immunoglobulin G / Q000097:blood; D015850:Interleukin-6 / Q000276:immunology; D008297:Male; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016036:Seroepidemiologic Studies
D007074:Immunoglobulin G; D015850:Interleukin-6