Seroprevalence of neutralizing antibodies to human mastadenovirus serotypes 3 and 7 in healthy children from Guangdong Province

Severe adenovirus pneumonia is becoming more common in children infected with human mastadenovirus (HAdV)-3 and HAdV-7 than in those infected with other types of adenoviruses. Recently, there has been a trend toward an increasing prevalence of pneumonia caused by HAdV-7, an important viral pathogen in Pediatric Intensive Care Unit infections. Children infected with HAdV-7 have more serious symptoms of acute respiratory infections and other complications than those infected with HAdV-3. No specific anti-adenovirus drugs or vaccines are available for treatment or prevention. Therefore, we investigated the seroprevalence and titer levels of neutralizing antibodies (NAbs) against HAdV-3 and HAdV-7 in healthy children in Guangdong Province. We found that the seropositivity rates and antibody titers for HAdV-3 NAb were higher than those for HAdV-7 NAb. In children between 6 and 12 months of age, the seropositivity rates and titers were significantly low against HAdV-3 and HAdV-7. The HAdV-7-positive rate was significantly higher in the HAdV-3-positive samples than in the HAdV-3-negative samples. The HAdV-7 NAbs carried by the 0-6-month age group were dominated by low titers. These results reveal a low level of herd immunity against HAdV-3 and HAdV-7 in children, clarifying the importance of monitoring these two highly virulent adenoviruses, developing prophylactic vaccines, and predicting potential outbreaks.