Zika病毒与Zika病毒病

Zika病毒(Zika virus,ZIKV)是一种新现虫媒病毒,属于黄病毒科黄病毒属。其感染后临床表现为轻症发热,因病重住院者罕见。流行病学数据显示Zika病毒病的流行与自身免疫性神经性疾病格林-巴利综合征及先天性小头畸形有关,引起了专家和公众的关注,但具体机制有待深入研究。     

Feline immunodeficiency virus ORF-Ais required for virus particle formation and virus infectivity

The orf-A (orf-2) gene of feline immunodeficiency virus (FIV) is a small open reading frame predicted to encode a 77-amino-acid protein that contains putative domains similar to those of the ungulate lentiviral Tat protein. Orf-A is reported to be critical for efficient viral replication in vitro and in vivo. A series of FIV-pPPR-derived proviruses with in-frame deletions and point mutations within orf-A were constructed and tested for replication in feline lymphoid cells. Orf-A mutant proviruses were also tested for viral gene and protein expression, viral particle formation, and virion infectivity. Deletions within orf-A severely restricted FIV replication in feline peripheral blood mononuclear cells (PBMC) and interleukin-2-dependent T-cell lines. In addition, substitutions of alanines for leucines in the putative leucine-rich domain, for cysteines in the putative cysteine-rich domain, and for a tryptophan at position 43 in Orf-A restricted the replication of FIV mutants. Deletions and point mutations in orf-A imposed a small effect or no effect on FIV long-terminal-repeat-driven viral gene expression and had no effect on viral protein expression. However, release of cell-free, virion-associated viral RNA in supernatants from cells transfected with orf-A mutant proviruses was severely restricted but was rescued by cotransfection with a wild-type Orf-A expression vector. In addition, virions derived from orf-A mutant proviruses expressed reduced infectivity for feline PBMC. Our findings suggest that Orf-A functions involve multiple steps of the FIV life cycle including both virion formation and infectivity. Furthermore, these observations suggest that Orf-A represents an FIV-encoded analog more similar to the accessory gene vpr, vpu, or nef than to the regulatory gene tat encoded by the primate lentiviruses.     

Interaction of cucumber mosaic virus and potato virus y with tobacco mosaic virus

A study was performed on the interaction of cucumber mosaic virus (CMV) of potato virus Y (PVY) with tobacco mosaic virus (TMV). Interference was evaluated using tobacco plantsNicotiana tabacum cv. Java responding to CMV and PVY with a systemic infection and to TMV with local necrotic lesions. The decrease in TMV — induced lesion number gave evidence of a decrease in susceptibility caused by the previous infection with CMV or PVY, the decrease of lesion enlargement demonstrated a decreased TMV reproduction in the plants previously infected with CMV or PVY. The interference concerned was incomplete, as evaluated from reproduction of the challenging TMV and from the decrease in susceptibility of the host to TMV brought about by the first infection with CMV or PVY.     

Reassembly of brome mosaic virus from dissociated virus

The reconstitution of Brome Mosaic Virus (BMV) has been studied using neutron scattering. Experiments were performed on disassembled virus without subsequent separation of components. Phase diagrams of the disassembly and subsequent reassembly of BMV were established as a function of pH and LiCl molarity by analytical centrifugation and quasi-elastic light scattering. Disassembly occurs at a pH above 6.5 and above 0.8 M LiCl. On reassembly, if the pH is lowered first, capsids are formed without subsequent incorporation of RNA. Neutron scattering was used to investigate the formation of virus particles, when the ionic strength was lowered from 1.4 to 0.1 M LiCl at pH 7.8. The reconstitution was followed continuously. As it was driven by a lowering of the ionic strength the kinetics of the process cannot be studied for short times. However the fact that at any given ionic strength no evolution of the scattering was observed with time implies that the reconstitution is complete within a few minutes. The observations in buffers with various amounts of D₂O lead to the conclusion that the reassembly is achieved by co-condensation of the RNA and of the capsid proteins.     

Evolutionary relationship of alfalfa mosaic virus with cucumber mosaic virus and brome mosaic virus

The amino acid sequences of the non-structural protein (molecular weight 35,000; 3a protein) from three plant viruses — cucumber mosaic, brome mosaic and alfalfa mosaic have been systematically compared using the partial genomic sequences for these three viruses already available. The 3a protein of cucumber mosaic virus has an amino acid sequence homology of 33.7% with the corresponding protein of brome mosaic virus. A similar protein from alfalfa mosaic virus has a homology of 18.2% and 14.2% with the protein from brome mosaic virus and cucumber mosaic virus, respectively. These results suggest that the three plant viruses are evolutionarily related, although, the evolutionary distance between alfalfa mosaic virus and cucumber mosaic virus or brome mosaic virus is much larger than the corresponding distance between the latter two viruses.     

TT virus

Non-enveloped TT virus (TTV), recognized in 1997, contains single-stranded circular DNA (about 3,800 nucleotides) and seems to be a member of Circinoviridae, a new family of hepatitis viruses. The data on the occurrence of TTV are highly controversial: 1-22% in blood donors, 20-40% in hematological patients, 15-35% in patients with liver diseases. The virus has been found to be transmitted by the oral-fecal route as it penetrates via bile into feces and is then excreted from the gastrointestinal tract. A relatively low percentage of the occurrence of TTV infection in groups of risk may be regarded as the evidence that sexual and injection routes are not the main route of its transmission. Further investigations are necessary to establish the regularities of the epidemiology of TTV, to obtain information on its pathogenicity and on the methods for diagnosing hepatitis caused by this virus.     

Human immunodeficiency virus drug therapy and virus load.

Analysis of the short-term dynamics of human immunodeficiency virus (HIV) type 1 infection in response to drug therapy has elucidated crucial kinetic properties of viral dynamics in vivo (D. D. Ho et al., Nature 373:123-126, 1995; A. S. Perelson et al., Science 271:1582-1586, 1996; X. Wei et al., Nature 373:117-122, 1995). Here we investigated long-term changes in virus load in patients treated with a combination of lamivudine and zidovudine to identify principal factors responsible for the observed 10- to 100-fold sustained suppression of virus load in vivo. Interestingly, most standard accounts of virus dynamics cannot explain a large sustained reduction without shifting the virus very close to extinction. The effect can be explained by taking into consideration either (i) the immune response against HIV, (ii) the killing of uninfected CD4 cells, or (iii) the differential efficacies of the drugs in different cell populations.     

Bovine virus diarrhea virus in free-living deer from Denmark

Free-living deer are suggested as a possible source of infection of cattle with bovine virus diarrhea (BVD) virus. To examine this hypothesis blood samples from 476 free-living deer were collected during two different periods and tested for BVD virus and antibody in Denmark. In 1995-96, 207 animals were tested. These included 149 roe deer (Capreolus capreolus), 29 fallow deer (Dama dama), 20 red deer (Cervus elaphus) and one sika deer (Cervus sika). For the remaining eight animals no species information was available. In 1998-99, 269 animals were tested including 212 roe deer and 57 red deer. The animals were selected from areas with a relatively high prevalence of cattle herds with a BVD persistent infection status in 1997 and 1998. All 207 samples from 1995-96 were found antibody-negative except two samples from red deer. Only 158 of the 207 samples were tested for virus and were all found negative. Of the 269 samples from 1998-99 all but one were antibody negative. The positive sample was from a red deer. All samples were virus-negative. It appears that BVD infection does not occur in roe deer in Denmark. The presence of antibody in a few red deer from various districts in Jutland probably results from cattle to deer transmission, rather than spread among deer. Hence, the possibility of free-living deer as a source of infection for cattle in Denmark seems to be remote.