- Volume 96, Issue 12, 2015

Human immunodeficiency virus type 1 (HIV-1) transmission often results from infection by a single transmitted/founder (T/F) virus. Here, we investigated the sensitivity of T/F HIV-1 envelope glycoproteins (Envs) to microbicide candidate carbohydrate-binding agents (CBAs) griffithsin (GRFT), cyanovirin-N (CV-N) and Galanthus nivalis agglutinin (GNA), showing that T/F Envs demonstrated different sensitivity to CBAs, with IC50 values ranging from 0.006 ± 0.0003 to >10 nM for GRFT, from 0.6 ± 0.2 to 28.9 ± 2.9 nM for CV-N and from 1.3 ± 0.2 to >500 nM for GNA. We further revealed that deglycosylation at position 295 or 448 decreased the sensitivity of T/F Env to GRFT, and at 339 to both CV-N and GNA. Mutation of all the three glcyans rendered a CBA-sensitive T/F Env largely resistant to GRFT, indicating that the sensitivity of T/F Env to GRFT is mainly determined by glycans at 295, 339 and 448. Our study identified specific T/F Env residues associated with CBA sensitivity.

Behavioural fever is a widely conserved response to infection. The host increases body temperature (T b) by altering their preferred temperature (T p), generating a fever and delaying or avoiding pathogen-induced mortality. This response is not ubiquitous in insects, however, although few studies have investigated this response to viral infection. Here, we examined the change in T p of Drosophila in response to virus infection using a thermal gradient. No difference in T p was observed. We suggest that the lack of behavioural fever could be due to the increased energy cost of maintaining a higher T b whilst the immune response is active. To the best of our knowledge, this is the first study to assay for changes in T p of infected Drosophila.

The yak (Bos grunniens) is an iconic symbol in the high-altitude region of the Qinghai–Tibetan Plateau. Diarrhoea is a common disease in yaks, resulting in major economic losses. To investigate the diversity of viral species, we reported the metagenomics-derived virome in a pooled faecal sample of 20 diarrhoeic yaks. The nine viruses found in the pooled diarrhoeic samples, in order of abundance of nucleic acid sequence, were influenza A virus, bovine viral diarrhoea virus (BVDV), rotavirus, ungulate tetraparvovirus 1 (bovine hokovirus), astrovirus (AstV), bovine enterovirus, hepatitis E virus, kobuvirus and woodchuck hepatitis virus. Compared with healthy yaks, only AstV had a significantly higher prevalence rate in diarrhoeal samples, indicating a correlation with the clinical symptoms of diarrhoea in yaks. To further investigate the molecular characterization of yak AstV, a near-full genome was obtained from a diarrhoeic sample. It was 6243 bp in length and shared 46.4–66.2 % similarity with other related bovine AstVs from faeces. Phylogenetic analysis of the genome demonstrated that the yak AstV fell within the bovine AstVs cluster, but was located in a unique lineage, suggesting a novel AstV species was identified in yaks. Interestingly, the ORF2 region of yak AstV had closer similarity and genetically relationship with deer AstV strain CcAstV-2 than that of the bovine AstVs. Further analysis showed that one possible interspecies recombination event occurred in ORF2. In summary, this study expanded our understanding of the viral communities of diarrhoeal yaks and identified a novel AstV that was associated with diarrhoea in yaks.

The genome sequence, genetic characterization and nblA gene function of Microcystis aeruginosa myovirus isolated from Lake Dianchi in China (MaMV-DC) have been analysed. The genome DNA is 169 223 bp long, with 170 predicted protein-coding genes (001L–170L) and a tRNA gene. About one-sixth of these genes have homologues in the host cyanobacteria M. aeruginosa. The genome carries a gene homologous to host nblA, which encodes a protein involved in the degradation of cyanobacterial phycobilisome. Its expression during MaMV-DC infection was confirmed by reverse transcriptase PCR and Western blot detection and abundant expression was companied by the significant decline of phycocyanin content and massive release of progeny MaMV-DC. In addition, expressing MaMV-DC nblA reduced the phycocyanin peak and the phycocyanin to chlorophyll ratio in model cyanobacteria. These results confirm that horizontal gene transfer events have occurred between cyanobacterial host and cyanomyovirus and suggest that MaMV-DC carrying host-derived genes (such as 005L, that codes for NblA) is responsible for more efficient expression of cyanophage genes and release of progeny cyanophage. This study provides novel insight into the horizontal gene transfer in cyanophage and the interactions between cyanophage and their host.

Prion protein (PrP) is present at extremely low levels in the blood of animals and its detection is complicated by the poor sensitivity of current standard methodologies. Interesting results have been obtained with recent advanced technologies that are able to detect minute amounts of the pathological PrP (PrPSc), but their efficiency is reduced by various factors present in blood. In this study, we were able to extract cellular PrP (PrPC) from plasma-derived exosomes by a simple, fast method without the use of differential ultracentrifugation and to visualize it by Western blotting, reducing the presence of most plasma proteins. This result confirms that blood is capable of releasing PrP in association with exosomes and could be useful to better study its role in the pathogenesis of transmissible spongiform encephalopathies.