Abstract
Two live attenuated oral rotavirus vaccines, Rotarix and RotaTeq, have been introduced as voluntary vaccination in Japan since 2011 and 2012, respectively. Effectiveness of the vaccines has been confirmed, whereas concerns such as shedding of the vaccine strains and gastroenteritis cases caused by vaccine strains are not well assessed. We aimed to identify the vaccine strains in children with acute gastroenteritis (AGE) to investigate the prevalence of AGE caused by vaccination or horizontal transmission of vaccine strains. A total of 1,824 stool samples were collected from children with AGE at six outpatient clinics in 2012–2015. Among all, 372 group A rotavirus (RVA) positive samples were screened for vaccine components by real-time RT-PCR which were designed to differentiate vaccine strains from rotavirus wild-type strains with high specificity. For samples possessing both vaccine and wild-type strains, analyses by next-generation sequencing (NGS) were conducted to characterize viruses existed in the intestine. As a result, Rotarix-derived strains were identified in 6 of 372 (1.6%) RVA positive samples whereas no RotaTeq strain was detected. Among six samples, four possessed Rotarix-derived strains while two possessed both Rotarix-derived strains and wild-type strains. In addition, other pathogens such as norovirus, enterovirus and E.coli were detected in four samples. The contribution of these vaccine strains to each patient’s symptoms was unclear as all of the cases were vaccinated 2–14 days before sample collection. Proportion of average coverage for each segmented gene by NGS strongly suggested the concurrent infection of the vaccine-derived strain and the wild-type strain rather than reassortment of these two strains in one sample. This is the first study to report the prevalence of vaccine-derived strains in patients with RVA AGE in Japan as 1.6% without evidence of horizontal transmission. The results emphasized the importance of continuous monitoring on vaccine strains and their clinical impacts on children.
Highlights
Rotavirus infection is a leading cause of acute gastroenteritis (AGE) among children under five years of age causing approximately 215,000 deaths in a year worldwide [1]
All stool samples were initially screened by a method of multiplex RT-PCR which was designed for detection of 11 diarrhea causing viruses including rotavirus, norovirus (GI and GII), adenovirus, astrovirus, sapovirus, aichivirus, parechovirus and enterovirus [24]
Partial NSP2 gene of Rotarix strain was detected in seven samples (1.9%), whereas no products of RotaTeq VP6 gene strain were detected
Summary
Rotavirus infection is a leading cause of acute gastroenteritis (AGE) among children under five years of age causing approximately 215,000 deaths in a year worldwide [1]. Group A rotaviruses (RVA) are a leading cause of AGE in children and are further classified based on genotypes of two outer capsid proteins, VP7 (G-type) and VP4 (P-type) [2]. In addition to G/P-genotyping, a complete genome classification system was developed by rotavirus classification working group (RCWG) [3]. Since RNA segments from different rotaviruses within the same group would reassort with high frequency during dual infections of cells, a comprehensive classification on 11 genome segments allows us to identify reassortments to confirm interspecies transmission [2,4,5]
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