Complete genome sequence analysis and phylogenetic classification of the novel Aeromonas phage AHP-1, a potential member of the genus Tequatrovirus.

Aeromonas phage AHP-1 was originally isolated from crucian carp (Carassius carassius) tissue. It was able to infect Aeromonas hydrophila and A. salmonicida. Genome sequence analysis revealed a 218,317-bp-long linear genome with an overall G + C content of 47.9%, 315 open reading frames (ORFs), and 25 tRNA sequences. Its genome was found to contain 67 unique ORFs (21.26%) that did not show any homology to previously characterized proteins. A comparative genome analysis suggested that its closest neighbors are unclassified phages belonging to the genus Tequatrovirus of the subfamily Tevenvirinae.

Reduction of Cell Fusion by Deletion in the Hypervariable Region of the Spike Protein of Mouse Hepatitis Virus.

Deletions in the spike gene of mouse hepatitis virus (MHV) produce several variants with diverse biological characteristics, highlighting the significance of the spike gene in viral pathogenesis. In this study, we characterized the JHM-X strain, which has a deletion in the hypervariable region (HVR) of the spike gene, compared with the cl-2 strain, which has a full spike gene. Cytopathic effects (CPEs) induced by the two strains revealed that the size of the CPE produced by cl-2 is much greater than that produced by JHM-X in delayed brain tumor (DBT) cells. Thus, this finding explains the greater fusion activity of cl-2 than JHM-X in cultured cells, and we speculate that the deletion region of the spike protein is involved in the fusion activity differences. In contrast with the fusion activity, a comparison of the virus growth kinetics revealed that the titer of JHM-X was approximately 100 times higher than that of cl-2. We found that the deletion region of the spike protein was involved in fusion activity differences, whereas cl-2 produced significantly higher luciferase activity than JHM-X upon similar expression levels of the spike protein. However, the reason behind the growth difference is still unknown. Overall, we discovered that deletion in the HVR of the spike gene could be involved in the fusion activity differences between the two strains.