The chemokines are a large family of small signaling proteins that bind to G-protein-coupled receptors (GPCRs) on target cells and mediate the directional migration of immune cells into sites of infection or inflammation. The large DNA viruses, particularly the poxviruses and herpesviruses, have evolved several mechanisms to corrupt the normal functioning of the chemokine network. Two strategies rely on mimicking chemokines or chemokine receptors. A third strategy involves the production of secreted chemokine-binding proteins (CKBPs) that exhibit no sequence similarity to any known host proteins, yet function to competitively bind and inhibit the interactions of chemokines with cognate receptors. Each strategy has provided unique insights into the elusively complex world of the chemokines. Here, we focus on recent advances made in the understanding of secreted CKBPs encoded by poxviruses and herpesviruses. A better understanding of how viral CKBPs function to manipulate the immune response may provide further clues as to how to develop specific therapeutic agents to abrogate chemokine-mediated disease conditions. (+info)
Infection control for gene therapy: a busy physician's primer.
(34/406)
Gene therapy is being studied for the treatment of a wide variety of acquired and inherited disorders. Retroviruses, adenoviruses, poxviruses, adeno-associated virus, herpesviruses, and others are being engineered to serve as gene therapy vectors and are being administered to patients in a clinical setting. Infection control professionals will be asked to evaluate the use and safety of these agents in their clinics and hospitals. This review summarizes key aspects of the biotechnology and the vectors involved in gene therapy and makes recommendations for infection control. (+info)
Roles of uracil-DNA glycosylase and dUTPase in virus replication.
(35/406)
Herpesviruses and poxviruses are known to encode the DNA repair enzyme uracil-DNA glycosylase (UNG), an enzyme involved in the base excision repair pathway that specifically removes the RNA base uracil from DNA, while at least one retrovirus (human immunodeficiency virus type 1) packages cellular UNG into virus particles. In these instances, UNG is implicated as being important in virus replication. However, a clear understanding of the role(s) of UNG in virus replication remains elusive. Herpesviruses, poxviruses and some retroviruses encode dUTPase, an enzyme that can minimize the misincorporation of uracil into DNA. The encoding of dUTPase by these viruses also implies their importance in virus replication. An understanding at the molecular level of how these viruses replicate in non-dividing cells should provide clues to the biological relevance of UNG and dUTPase function in virus replication. (+info)
The vaccinia virus C12L protein inhibits mouse IL-18 and promotes virus virulence in the murine intranasal model.
(36/406)
A bioassay that measured the interleukin (IL)-12-induced production of interferon (IFN)-gamma from mouse splenocytes was used to identify a soluble factor in the supernatants of vaccinia virus (VV)-infected cells that inhibited the production of IFN-gamma. This soluble factor was expressed by 14 out of 16 VV strains including the Western Reserve (WR) strain, but strains Copenhagen and Tashkent and a mutant of strain WR called 6/2 lacked this activity. The gene encoding this activity was identified as C12L by transferring DNA present in VV WR but missing in VV WR 6/2 into VV Copenhagen and testing for expression of the soluble factor. The C12L protein shows amino acid similarity to IL-18 binding proteins that are encoded by poxviruses, mice and humans, and C12L protein produced from VV or baculovirus inhibited the biological activity of mouse IL-18 in vitro. Thus the inhibition of IL-12-induced IFN-gamma production was due to indirect effects of C12L on IL-18, illustrating the synergistic action of these pro-inflammatory cytokines. To study the role of the C12L protein in the virus life-cycle, we constructed a deletion mutant lacking the C12L gene and a revertant virus in which the gene was reinserted into the deletion mutant. In vitro the replication and plaque size of these viruses were indistinguishable. However, infection of BALB/c mice by the intranasal route showed that the deletion mutant was attenuated and induced lower weight loss and signs of illness compared to controls. (+info)
Containment of simian immunodeficiency virus infection in vaccinated macaques: correlation with the magnitude of virus-specific pre- and postchallenge CD4+ and CD8+ T cell responses.
(37/406)
Macaques infected with the SIV strain SIVmac251 develop a disease closely resembling human AIDS characterized by high viremia, progressive loss of CD4(+) T cells, occurrence of opportunistic infection, cachexia, and lymphomas. We report in this study that vaccination with the genetically attenuated poxvirus vector expressing the structural Ags of SIVmac (NYVAC-SIV-gag, pol, env) in combination with priming with DNA-SIV-gag, env resulted in significant suppression of viremia within 2 mo after mucosal exposure to the highly pathogenic SIVmac251 in the majority of vaccinated macaques. The control of viremia in these macaques was long lasting and inversely correlated to the level of both pre- and postchallenge Gag-specific lymphoproliferative responses, as well as to the level of total SIV-specific CD4(+) T lymphocyte responses at the peak of acute viremia as detected by intracellular cytokine-staining assay. Viremia containment also correlated with the frequency of the immunodominant Gag(181-189)CM9 epitope-specific CD8(+) T cells present before the challenge or expanded during acute infection. These data indicate, for the first time, the importance of vaccine-induced CD4(+) Th cell responses as an immune correlate of viremia containment. The results presented in this work also further demonstrate the potential of a DNA-prime/attenuated poxvirus-boost vaccine regimen in an animal model that well mirrors human AIDS. (+info)
Poxvirus Orthologous Clusters (POCs).
(38/406)
Poxvirus Orthologous Clusters (POCs) is a JAVA client-server application which accesses an updated database containing all complete poxvirus genomes; it automatically groups orthologous genes into families based on BLASTP scores for assessment by a human database curator. POCs has a user-friendly interface permitting complex SQL queries to retrieve interesting groups of DNA and protein sequences as well as gene families for subsequent interrogation by a variety of integrated tools: BLASTP, BLASTX, TBLASTN, Jalview (multiple alignment), Dotlet (Dotplot), Laj (local alignment), and NAP (nucleotide to amino acid alignment). (+info)
Immunosuppressive activity of a subline of the mouse EL-4 lymphoma. Evidence for minute virus of mice causing the inhibition.
(39/406)
Filtered culture fluids from the early in vitro passages of a subline of the C57BL/6 mouse EL-4 lymphoma, EL-4(G-), were strongly inhibitory for BABL/c vs. C57BL/6 mixed lymphocyte cultures (MLC). The inhibitory activity could be preserved by storage at -75 degrees C or 4 degrees C, thus allowing its further characterization. The inhibitory factor was particulate (nondialyzable, sedimentable at 100,000 g for 1 h), very small (recovered after 0.10 mum filtration), sensitive to UV irradiation, but heat stable (56 degrees C, 1 h) and resistant to chloroform. It was infectious, since later, noninhibitory passages of EL-4(G-) tissue culture cells became strongly inhibitory upon inoculation with the culture fluid. This data was consistent with the inhibitory factor being an infectious virus. Virus analysis by mouse antibody production tests revealed that viruses were indeed present in EL-4(G-) ascites cells and in the culture fluid, and not in a late passage of EL-4(G-) tissue culture cells which were not inhibitory. Neutralization of the inhibitory factor was achieved by pretreatment with ascitic fluid or with the sera raised against those (EL-4(G-)-derived materials which contained viruses. Mouse reference immune sera against minute virus of mice (MVM) completely neutralized the inhibitory factor in the culture fluid or in EL-4(G-) ascites cells. Two prototype MVM strains, and one Kilham rat virus preparation, did not inhibit the mouse MLC. Thus, the possibility exists that a variant of MVM, or an unidentified virus, has been grown and selected for in EL-4(G-) cells and recognized, due to its immunosuppressive characteristics. In any event, immunosuppression by EL-4(G-) cells was not mediated by the tumor cells, their metabolic products, or associated endogenous type C viruses, but by an exogenous virus, most likely a variant MVM with immunosuppressive characteristics. This adds weight to a parallel observation from our laboratory on the immunosuppressive effects of Kilham rat virus in rat lymphocyte cultures. (+info)
Equivalent immunogenicity of the highly attenuated poxvirus-based ALVAC-SIV and NYVAC-SIV vaccine candidates in SIVmac251-infected macaques.
(40/406)
Therapeutic immunization of HIV-1-infected individuals may induce and/or enhance HIV-1-specific immune responses and decrease the dependency on antiretroviral drug treatment. However, repeated immunizations with live-recombinant vectors may induce vector-specific immune responses that interfere with the elicitation of vigorous immune responses to the desired antigen. Therefore, the use of mixed-modality vaccinations may be necessary to induce sustained virus-specific immune responses in HIV-1-infected individuals treated with antiretroviral therapy (ART). Thus, the relative immunogenicity of various vaccine modalities needs to be assessed. Here we compared the immunogenicity of two vaccine candidates, the canarypox-based ALVAC-SIV-gag-pol-env (ALVAC-SIV-gpe) and the vaccinia-based NYVAC-SIV-gag-pol-env (NYVAC-SIV-gpe), in rhesus macaques infected with SIVmac251 and treated with ART by 2 weeks postinfection. Both ALVAC-SIV-gpe and NYVAC-SIV-gpe vaccine candidates induced and/or enhanced a virus-specific CD8+ T cell response to a similar extent, as demonstrated by tetramer staining of Gag-specific CD8+ T cells. Similarly, both vaccines elicited comparable lymphoproliferative responses (LPRs) to the SIV p27 Gag and gp120 Env proteins. Thus, both these vaccine modalities alone or in combination may be suitable candidate vaccines for immune therapy of HIV-1-infected individuals. (+info)