Isolation and identification of the Akabane virus from mosquitoes in Yunnan Province, China / 病毒学报

ABSTRACT

To evaluate the prevalence of mosquito-borne viruses in Manshi and Ruili (Yunnan Province, China), we collected 2 149 mosquitoes (17 species) in August 2010. Virus isolation was undertaken by the cul- ture of baby hamster kidney cells (BHK-21 cells). Two virus-like isolates were obtained DHL10M117 was isolated from collected in Mangshi; DHL10M110 was obtained from Anopheles vagus collected in Rui- li. Both isolates caused cytopathic effects,illness and death in suckling mice inoculated with these isolates via the intracerebral route. Two positive amplicons, 702-bp from the S segment and 456-bp from the M segment,were obtained using reverse transcription-polymerase chain reaction using primers specific for the Akabane virus (AKV). Phylogenetic analysis suggested that these two virus stains had a distant relation- ship with AKVs from Kenya and Australia,but were genetically close to those from Japan,South Korea, and Taiwan. However,they were separate from other Asian strains and grouped into a small branch. The highest nucleotide and amino-acid sequence identity of the S segment was found with the CY-77 strain from Taiwan (96.6% and 99.6% for DHL10M117 and 96.7% and 100% for DHL10M110,respectively). Com- parison of the M segment showed they shared the highest amino acid identity with CY-77 (99.6% and 100%, respectively), whereas the highest nucleotide identity was found with the Iriki strain from Japan (99.6% and 100%, respectively). Compared with the MP496 strain from Kenya,they displayed lower lev- els of sequence homology, at 69.7% and 70.0% for nucleotide sequences of the two loci,and 91. 0% for a- mino acids. Our results identified that DHL10M117 and DHL10M110 were strains of AKV,and provided molecular biological evidence for the existence of AKV in Yunnan Province. These AKV strains that are circulating in Yunnan Province share a close genetic relationship with strains from the rest of Asia. Culex tritaeniorhynchus and Anopheles vagus may serve as transmission vectors.