Whole-genome sequencing of live attenuated bovine adenovirus type 7 vaccine strain TS-GT suggests biomarkers for virulence attenuation

Bovine adenovirus type 7 (BAdV-7) is one of the most important respiratory and enteric pathogens in the cattle industry. Although live attenuated vaccines are used to control the virus in Japan, limited information is available on the genomic regions that determine viral pathogenicity. We determined the complete genome sequence of the attenuated BAdV-7 strain TS-GT. The genome is 30,052 bp long and contains 45-bp inverted terminal repeats and 30 predicted genes. A genome sequence comparison showed that 99.9% of the TS-GT genome is identical to the prototypic and pathogenic BAdV-7 strain Fukuroi; however, the TS-GT genome contains a novel mutation and four indels. We describe here potential relationships between these genomic changes and the biological characteristics of BAdV-7.

Structure of a Cell Entry Defective Human Adenovirus Provides Insights into Precursor Proteins and Capsid Maturation

Maturation of adenoviruses is distinguished by proteolytic processing of several interior minor capsid proteins and core proteins by the adenoviral protease and subsequent reorganization of adenovirus core. We report the results derived from the icosahedrally averaged cryo-EM structure of a cell entry defective form of adenovirus, designated ts1, at a resolution of 3.7 Å as well as of the localized reconstructions of unique hexons and penton base. The virion structure revealed the structures and organization of precursors of minor capsid proteins, pIIIa, pVI and pVIII, which are closely associated with the hexons on the capsid interior. In addition to a well-ordered helical domain (a.a. 310-397) of pIIIa, highlights of the structure include the precursors of VIII display significantly different structures near the cleavage sites. Moreover, we traced residues 4-96 of the membrane lytic protein (pVI) that includes an amphipathic helix occluded deep in the hexon cavity suggesting the possibility of co-assembly of hexons with the precursors of VI. In addition, we observe a second copy of pVI ordered up to residue L40 in the peripentonal hexons and a few fragments of density corresponding to 2nd and 3rd copies of pVI in other hexons. However, we see no evidence of precursors of VII binding in the hexon cavity. These findings suggest the possibility that differently bound pVI molecules undergo processing at the N-terminal cleavage sites at varying efficiencies, subsequently creating competition between the cleaved and uncleaved forms of VI, followed by reorganization, processing, and release of VI molecules from the hexon cavities.

Rapid Adenovirus typing method for species identification

Adenoviruses are characterized by a large variability, reflected by their classification in species A to G. Certain species, eg A and C, could be associated with increased clinical severity, both in immunocompetent and immunocompromised hosts suggesting that in some instances species identification provides clinically relevant information. Here we designed a novel "pVI rapid typing method" to obtain quick, simple and cost effective species assignment for Adenoviruses, thanks to combined fusion temperature (Tm) and amplicon size analysis. Rapid typing results were compared to Sanger sequencing in the hexon gene for 140 Adenovirus-positive clinical samples included in the Typadeno study. Species A and C could be identified with a 100% positive predictive value, thus confirming the value of this simple typing method.

First generation inhibitors of the adenovirus proteinase

As there are more than 50 adenovirus serotypes, the likelihood of developing an effective vaccine is low. Here we describe inhibitors of the adenovirus proteinase (AVP) with the ultimate objective of developing anti-adenovirus agents. Inhibitors were identified via structure-based drug design using as druggable sites the active site and a conserved cofactor pocket in the crystal structures of AVP. A lead compound was identified that had an IC50 of 18 μM. One of eight structural derivatives of the lead compound had an IC50 of 140 nM against AVP and an IC50 of 490 nM against the AVP with its cofactor bound.