Human papillomavirus in tonsillectomy specimen from China and Pakistan - Prevalence and genotype distribution.

Background: The expected corresponding increase in tonsillar human papillomavirus (HPV) infection associated with increasing incidence of oropharyngeal squamous cell carcinoma (OPSCC) substantiate the evaluation of normal tonsillar tissue in different population. The epidemiology of HPV in tonsillar tissue varies geographically. This study evaluated samples from two countries to determine the prevalence in respective samples.

Objective: To characterize HPV infection in non-malignant tonsillar tissue from Shaanxi, China (herein after referred to as China) and Punjab, Pakistan (herein after referred to as Pakistan).

Methodology: The DNA extracted from formalin-fixed, paraffin-embedded tumor free tonsillar tissue was evaluated using polymerase chain reaction (PCR). A total of 367 cases from China and 139 cases from Pakistan were screened for HPV DNA using GP5+/GP6+ consensus primer. Genotype of the positive cases was determined for common HPV types (6, 11, 16, 18, 52, 58) simultaneously by type-specific PCR.

Results: The mean age of cohorts in China was 13.42 (Median age 7, Range 2-72 years) while in Pakistan it was 10.77 (Median age 8, Range 3-42 years) the gender distribution was 61.6% male in China and in Pakistan they were 56.8%, rest were females. The overall prevalence of HPV in China was 2.45% and 2.16% in Pakistan. High risk human papillomavirus was 1.63% in China with 5 cases positive for HPV 16 and HPV 58 in 1 case. In Pakistan, 2 cases (1.43%) of HPV 16 were detected. Low-risk types include HPV 11 present in 2 cases from China, while HPV 6 was detected in 1 case each from both the countries.

Conclusion: A low prevalence of HPV was found in China and Pakistan; high-risk and low-risk HPV were detectable in tonsillar tissue from both countries. Age stratification (< 5 years, 5-14 years, 15-25 years, > 25 years) suggest that sexual and non-sexual transmission of the virus can occur. The difference in the genotype distribution geographically within China and with Pakistan was observed in the case of HPV 58. The most common type in both the countries was HPV 16.