HHV-6 was found in 33% of adenoid and 45% of tonsil tissues, with the highest rates found in younger children.
Finnish investigators assessed the presence of nucleic acid from 22 viruses in resected tissue and nasopharyngeal aspirates from patients with chronic adenotonsillar disease, ranging in age from 1 to 20 years old. They found herpesviruses and respiratory viruses in 89% and 94% respectively, more often in tonsils than in adenoids.
HHV-6 was the most prevalent of the herpesviruses, and was found in the adenoids, tonsils and/or nasopharyngeal aspirates of 67% of patients. Prevalence of the viruses in people of different ages was not remarkably different except that HHV-6 was more prevalent in adenoids of young children than in older children.
HHV-7 was the most common virus found in tonsils, and the viral load for both HHV-6 and HHV-7 was much higher in tonsil than adenoid tissues. No DNA of HSV2 or VZV, and very little of CMV or HSV1, was found in the adenotonsillar tissues. In contrast to HHV-6 and HHV-7, which were found more often and in higher abundance in tonsils than in adenoids, rhinovirus was found in 60% of adenoids and 7% of tonsils.
The Finnish study did not differentiate between HHV-6A and HHV-6B, but a previous study of pediatric tonsils determined that 97% of HHV-6 positive samples were HHV-6B with positive staining was largely in the squamous epithelium of tonsillar crypts (Roush 2001).
No healthy control tissues were studied, for ethical reasons.
The authors conclude that adenoid and tonsil tissues may serve as a viral reservoir in non-acutely ill patients and deserves further study.
Read the full article: Ivasca 2022