Metagenomic analysis identifies human adenovirus 31 in children with acute flaccid paralysis in Tunisia

A variety of viruses can cause acute flaccid paralysis (AFP). However, the causative agent, sometimes, remains undetermined. Metagenomics helps in identifying viruses not diagnosed by conventional methods. Stool samples from AFP (n = 104) and non-AFP (n = 114) cases that tested enterovirus-negative by WHO standard methods were investigated. A metagenomics approach, first used on five pools of four samples each, revealed the presence of adenovirus sequences. Amplification in A549 cells and full-genome sequencing were used for complete virus identification and for designing a PCR assay to screen individual related samples. Metagenomic analysis showed that adenovirus sequences that were closely to the A31 and A61 genotypes were the most abundant. Two out of the corresponding 20 individual samples were found positive by PCR, and isolates were obtained in cell culture. Phylogenetic analysis based on complete genome sequences showed that the viruses belong to HAdV-A31 genotype (98-100% nucleotide sequence identity). PCR analysis of stool samples from all AFP and non-AFP cases revealed that a larger proportion of the positive samples were from AFP cases (17.3%) than from non-AFP cases (2.4%). These results open the way to studies aiming to test a possible role of HAdV-A31 in the pathogenesis of AFP.