Identification of a new genogroup of aquareovirus by RNA-RNA hybridization

Researchers analyzed 22 aquareovirus isolates from fish and shellfish worldwide to determine their genetic relationships using RNA-RNA hybridization techniques. Aquareviruses are double-stranded RNA viruses belonging to the family Reoviridae that infect aquatic animals. By comparing the electrophoretic mobility of their 11 genomic RNA segments and performing reciprocal dot blot hybridization under high-stringency conditions, the authors identified genetic groupings among the isolates. Eight isolates belonged to genogroup A, twelve to genogroup B, and two isolates—PSR (from chum salmon) and SCR (from chinook salmon)—represented a previously unknown sixth genogroup designated F. The researchers confirmed that PSR and SCR shared sequence relatedness across all eleven cognate genome segments, establishing them as a distinct genetic group. No genetic relationship was detected between aquareviruses and mammalian rotavirus SA11. These findings extend previous work identifying five genogroups and provide a molecular basis for classifying newly isolated aquareviruses. The study demonstrates that viruses from different fish species can belong to the same genogroup, and geographic location may correlate with genogroup distribution.

Key findings

• A new sixth genetic genogroup (genogroup F) of aquareovirus was identified, represented by two isolates (PSR and SCR) from different salmon species that showed sequence homology across all 11 genome segments.
• Of 22 aquareovirus isolates analyzed, eight belonged to genogroup A and twelve to genogroup B, while genogroups C, D, and E each contained single representatives.
• Aquareviruses showed no genetic relatedness to mammalian rotavirus SA11 under any hybridization stringency conditions tested.
• Genogroup B isolates were all recovered from Washington, USA, while genogroup A isolates came from diverse geographic locations, suggesting geographic clustering of certain genogroups.
• RNA-RNA hybridization proved effective for distinguishing genetic relationships among aquareovirus isolates, providing a molecular criterion for genogroup classification.