Detection of Human Papillomaviruses in the Nasopharynx of Breastfed Infants: New Findings and Meta-Analysis

Vertical transmission of human papillomaviruses (HPVs) from mother to infant is known to occur during labor, delivery or breastfeeding. Infection with mucosal HPV 6 and 11 may cause recurrent respiratory papillomatosis in children, which is a rare and severe respiratory disease. The cutaneous HPV genotypes have also been described to be transmitted from mother to newborn through skin-to-skin contacts and during breastfeeding. To investigate the perinatal transmission of alpha and beta HPVs we collected nasopharyngeal specimens from 0–12-months-old infants born by vaginal delivery and breastfed at the time of sample collection. The mucosal and cutaneous HPVs were searched by nested PCR using the MY09/11-MGPs and CP65/70-CP66/69 primer sets, respectively, and genotypes identified by direct sequencing analysis. Fourteen out of 113 (12.4%) samples tested positive for HPV and sequence analysis allowed us to identify eight beta genotypes (HPV 5b, 20, 25, 100, 107, 124, 152 and RTRX7). Moreover, we performed a comprehensive review of published studies on the prevalence of mucosal and cutaneous HPVs among 5126 newborns and observed that 10% and 53% were positive for alpha and beta HPVs, respectively. In all studies there was an inverse correlation between the rate of alpha HPV positivity and age, while a significant positive trend was observed in beta HPV detection and age with the highest rate among children older than 12 months (Χ2 test for trend of 10.6, p < 0.001). Further studies are needed to confirm the hypothesis that beta HPVs are transmitted to breastfeeding infants through shedding of viruses in the breast milk or on the external breast epithelium.