Virology reports最新文献

Ducks are generally considered as potential reservoirs for different genotypes of Newcastle disease virus (NDV) and to be resistant even to velogenic NDV strains. However, outbreaks of highly virulent genotype VII NDV lethal to ducks have been frequently reported in China in recent years. But until now, the pathogenesis and potential vaccine of duck-origin genotype VII NDV are not known. In this study, a reverse genetics system using the prevalent high virulence genotype VIId isolate SS1 was constructed. Based on this system, a red fluorescent protein (RFP)-expressing virus was generated by inserting an additional transcription cassette coding for the RFP between the noncoding region of P and M genes. The rescue of the recombinant viruses was confirmed by western blotting, fluorescence microscopy and genetic marker detection. In addition, the replication kinetics, biological characteristics and pathogenicity of the rescued viruses were indistinguishable from the parental wild-type virus. Moreover, the recombinant virus rSS1-RFP could efficiently replicate in most of the duck tissues, especially in duck immune organs. The results obtained suggest that this reverse genetics system will provide a useful tool for the analysis of duck-origin NDV pathogenesis and dissemination, as well as preparation for novel vaccine vector or genotype-matched NDV attenuated vaccines used in ducks.

The HIV-1 restriction factor SAMHD1 has the ability to negatively modulate retrotransposition of the long interspersed element 1(LINE-1). By exploring the ability of human SAMHD1 polymorphisms to inhibit LINE-1, we found that the single nucleotide polymorphism S33A present in the Korean population lose the ability to inhibit LINE-1 retrotransposition. Because SAMHD1 residue S33 is phosphorylated in human cycling and non-cycling cells, we demonstrated that SAMHD1 requires to be either phosphorylated on position 33 or to contain a bulky residue in order to inhibit LINE-1 retrotransposition. Therefore this unique mutation uncouples functions in this important restriction factor.

Arboviruses circulate in the biota of northern Australia, sometimes causing disease in animals and humans. Five different arboviruses, isolated and stored for over 30 years, were re-cultured and sequenced using high-throughput sequencing technology (Ion Torrent PGM) for identification and genetic characterization. Phylogenetic analysis, primarily of sequence fragments of the large segment, indicated classification as members of the Family Bunyaviridae (Belmont, Little Sussex, Parker's Farm, and Thimiri viruses). Another was identified as a member of the Family Rhabdoviridae (Beatrice Hill virus) based on phylogenetic analysis of the RNA polymerase region.

Betanodavirus infections have a significant impact through direct losses and trade restrictions for aquaculture sectors in Australia. The giant grouper, Epinephelus lanceolatus, is a high-value, fast-growing species with significant aquaculture potential. With subacute to chronic mortalities reported from a commercial aquaculture facility in northern Queensland, the viral nervous necrosis in the affected fish was confirmed using a RT-qPCR followed by virus isolation using the SSN-1 cell line. The RNA1 and RNA2 segments were sequenced and nucleotide sequences were compared with betanodavirus sequences from GenBank. Phylogenetic analysis revealed that both these sequences clustered with sequences representing red spotted grouper nervous necrosis virus genotype and showed high sequence identity to virus sequences affecting other grouper species. This is the first report confirming infection by betanodavirus in E. lanceolatus from Australia with successful isolation of the virus in a cell culture system, and analysis of nearly full length RNA1 and RNA2 sequences.

Dasheen mosaic virus (DsMV) the main causative agent of mosaic disease in elephant foot yam (Amorphophallus paeoniifolius) belongs to Potyviridae. The complete genome sequence of DsMV infecting A. paeoniifolius in Kerala state, India was assembled from the whole transcriptome sequencing reads of diseased host samples. The sequence of the virus which showed 83% identity with DsMV infecting Zantedeschia aethiopica (China) was confirmed through amplification and sequencing with primers designed based on the assembled sequence. Unambiguous recombination events mainly confined to the 5′ terminal 4000 nucleotides of the genome with phylogenetically related potyviruses were recognized. The length and genome composition towards the 3′ end comprising NIb, CP and 3′ UTR were not dependent on the host or the source region.

Hepatitis A virus (HAV) infection is the most common cause of acute viral hepatitis and has significant implications to public health worldwide. To characterize HAV strains circulating in China, five samples collected in different provinces from 2006–2009 were entirely sequenced. Phylogenetic analysis based on distinct segments showed that all five sequences belonged to subgenotype IA, but with slight differences in some fragments. No amino acid mutations were found at the known neutralizing epitope sites, and one unique substitution was identified near the immunodominant site. While no intertypic recombination was detected, intratypic recombination signals were found in the study. Molecular evolution analyses showed that the estimated mean substitution rate of genotype I worldwide was 3.27 × 10^− 4 substitutions/site/year, and the time to the most recent common ancestor (tMRCA) was about 267 years ago. The quasispecies distribution across the complete genome was also evaluated, and the high mutation frequency regions were mainly at the nonstructural protein coding sequences. This study contributed information on the genotype distribution, selection pressure, neutralizing epitope site mutations, recombination events and quasispecies distribution of HAV strains in China. The evolutionary status of genotype I worldwide was also analyzed, which will provide a reference for future HAV molecular epidemiology studies.

Different hypotheses have been elaborated to explain how the HTLV spread throughout the world. It has been proposed that the virus was introduced in Bahia, during the slave-trade period from the 16th century to 19th century. However, there is no information about the HTLV evolutionary history in southern Bahia. The phylogeny is fundamental in order to clarify its introduction and dispersion. The DNA of 29 samples was extracted, followed by nested-PCR assay for the LTR and DNA sequencing. These sequences were analyzed by phylogenic methods. The mtDNA ancestry markers and β^A-globin haplotypes were analyzed by PCR/RFLP. In relation to HTLV subtyping, all samples were classified as cosmopolitan subtype and transcontinental subgroup. Results suggest an ancient post-Columbian introduction of HTLV-1a-A associated with the slave trade between the XVI and late XIX centuries in southern Bahia. As regards the ethnicity of HTLV-infected women, the haplotype characterization of β-globin gene and the mtDNA ethnicity of HTLV-infected women, we have detected a major African contribution, with a predominance of Benin and Bantu types. HTLV-1 infection is spread in Bahia and the point of origin was possibly Salvador.

Marek's disease (MD) is a T-cell lymphoma of chickens caused by the oncogenic Marek's disease virus (MDV). MD is primarily controlled by live-attenuated vaccines generated by repeated in vitro serial passage. Previous efforts to characterize attenuated MDVs identified numerous mutations, particularly a convergence of high-frequency mutations around amino acids 60–63 within ICP4 (RS1), therefore, ICP4 was considered a candidate gene deserving further characterization. Recombinant MDVs were generated containing a single Q63H mutation or double Q63H + S1630P mutations. Despite the repetitive nature of mutations within ICP4, neither recombinant virus decreased virulence, although one mutant reduced in vivo replication and failed to transmit horizontally. Our results indicate that these mutations are insufficient to reduce disease incidence in infected birds, and suggest that variants in ICP4 do not directly alter virulence, but rather may enhance MDV replication rates in vitro, offering an explanation for the widespread occurrence of ICP4 mutations in a variety of attenuated herpesviruses.

Simian immunodeficiency virus (SIV) is a robust pathogen used in non-human primates to model HIV vaccines. SIV encodes a number of potential vaccine targets. By far the largest and most conserved protein target in SIV is gag-pol encodes many epitopes with potential to drive multivalent T cell responses. While it is an attractive antigen, pol is only translated after a frame shift from gag so that only 1 in 10 gag proteins include this larger antigen. The codon bias of native lentiviral genes are also mismatched with the abundance of tRNAs in mammalian cells resulting in poor expression of unmodified SIV genes. To provide a better SIV gag-pol immunogen for gene-based vaccination, we codon-optimized the full gag-pol sequence from SIVmac239. To increase pol expression, we artificially moved the pol sequence in frame to gag to bypass the need for a translational frame shift for its expression. Finally, we inserted four “self-cleaving” picornavirus sequences into gag p24, protease, reverse transcriptase, and into integrase to fragment the proteins for potentially better immune presentation. We demonstrate that these immunogens are well expressed in vitro and drive similar antibody and T cell responses with or without cleavage sequences.