This is an RSS newsfeed from BioMed Central It is intended to be used with an RSS reader. For more information about RSS newsfeeds from BioMed Central, visit http://www.biomedcentral.com/info/about/rss/ http://www.retrovirology.com The latest articles from Retrovirology (ISSN 1742-4690) published by BioMed Central Background: The development of an immunocompetent, genetically modified mouse model to study HIV-1 pathogenesis and to test antiviral strategies has been hampered by the fact that cells from native mice do not or only inefficiently support several steps of the HIV-1 replication cycle. Upon HIV-1 infection, mouse T-cell lines fail to express viral proteins, but the underlying replication barrier has thus far not been unambiguously identified. Here, we performed a kinetic and quantitative assessment of consecutive steps in the early phase of the HIV-1 replication cycle in T-cells from mice and humans. Results: Both T-cell lines and primary T-cells from mice harbor a severe post-entry defect that is independent of potential species-specific differences in LTR transactivation. Reverse transcription occurred efficiently following VSV-G-mediated entry of virions into mouse T-cells, and abundant levels of 2-LTR circles indicated successful nuclear import of the pre-integration complex. To probe the next step in the retroviral replication cycle, i.e. the integration of HIV-1 into the host cell genome, we established and validated a nested real-time PCR to specifically quantify HIV-1 integrants exploiting highly repetitive mouse B1 elements. Importantly, we demonstrate that the frequency of integrant formation is diminished 18- to >305-fold in mouse T-cell lines compared to a human counterpart, resulting in a largely abortive infection. Moreover, differences in transgene expression from residual vector integrants, the transcription off which is cyclin T1-independent, provided evidence for an additional, peri-integrational deficit in certain mouse T-cell lines. Conclusions: In contrast to earlier reports, we find that mouse T-cells efficiently support early replication steps up to and including nuclear import, but restrict HIV-1 at the level of chromosomal integration. http://www.retrovirology.com/content/5/1/58 Hanna-Mari Tervo, Christine Goffinet and Oliver T Keppler Retrovirology 2008, 5:58 2008-07-08 doi:10.1186/1742-4690-5-58 Retrovirology 1742-4690 5 58 2008-07-08 Background: The machinery of early HIV-1 replication still remains to be elucidated. Recently the viral core was reported to persist in the infected cell cytoplasm as an assembled particle, giving rise to the reverse transcription complex responsible for the synthesis of proviral DNA and its transport to the nucleus. Numerous studies have demonstrated that reverse transcription of the HIV-1 genome into proviral DNA is tightly dependent upon proper assembly of the capsid (CA) protein into mature cores that display appropriate stability. The functional impact of structural properties of the core in early replicative steps has yet to be determined. Results: Here, we show that infectivity of HIV-1 mutants bearing S149A and S178A mutations in CA can be efficiently restored when pseudotyped with vesicular stomatitis virus envelope glycoprotein, that addresses the mutant cores through the endocytic pathway rather than by fusion at the plasma membrane. The mechanisms by which these mutations disrupt virus infectivity were investigated. S149A and S178A mutants were unable to complete reverse transcription and/or produce 2-LTR DNA. Morphological analysis of viral particles and in vitro uncoating assays of isolated cores demonstrated that infectivity defects resulted from disruption of the viral core assembly and stability for S149A and S178A mutants, respectively. Consistent with these results, both mutants failed to saturate TRIM-antiviral restriction activity. Conclusions: Defects generated at the level of core assembly and stability by S149A and S178A mutations are sensitive to the way of delivery of viral nucleoprotein complexes into the target cell. Addressing CA mutants through the endocytic pathway may compensate for defects generated at the reverse transcription/nuclear import level subsequent to impairment of core assembly or stability. http://www.retrovirology.com/content/5/1/57 Sonia Brun, Maxime Solignat, Bernard Gay, Eric Bernard, Laurent Chaloin, David Fenard, Christian Devaux, Nathalie Chazal and Laurence Briant Retrovirology 2008, 5:57 2008-07-07 doi:10.1186/1742-4690-5-57 Retrovirology 1742-4690 5 57 2008-07-07 The recently released results of the Merck's Phase IIb "test-of concept" vaccine trials have shown no protection from HIV-1 infection in the vaccinated group compared with a control group vaccinated with placebo. The study was designed to test the Merck's MRKAd5 trivalent candidate vaccine. The vaccine formulation was expected to stimulate a HIV-specific T cell immune response and to either prevent infection, or to reduce the levels of the viral load in vaccinated subjects. Upon the first evaluation of the interim data, the independent Data and Safety Monitoring Board (DSMB) underscored no protection from HIV-1 infection in the vaccine-inoculated volunteers compared with the control group; accordingly, the vaccine trial was stopped. This disappointing outcome warrants a critical analysis of the current vaccine studies and calls for a renewed effort toward a rational design of novel immunogens to be tested in large primate trials. http://www.retrovirology.com/content/5/1/56 Enrico Iaccino, Marco Schiavone, Giuseppe Fiume, Ileana Quinto and Giuseppe Scala Retrovirology 2008, 5:56 2008-07-02 doi:10.1186/1742-4690-5-56 Retrovirology 1742-4690 5 56 2008-07-02 APOBEC3G is a cytidine deaminase with potent antiviral activity. The protein deaminates single-stranded DNA but is known to bind cellular and viral RNAs. There is increasing evidence that RNA binding of APOBEC3G is important for packaging into viral particles. However, there is no consensus yet on the type of RNA involved. http://www.retrovirology.com/content/5/1/55 Klaus Strebel and Mohammad A Khan Retrovirology 2008, 5:55 2008-07-02 doi:10.1186/1742-4690-5-55 Retrovirology 1742-4690 5 55 2008-07-02 Human APOBEC3 proteins are editing enzymes that can interfere with the replication of exogenous retroviruses such as human immunodeficiency virus (HIV), hepadnaviruses such as hepatitis B virus (HBV), and with the retrotransposition of endogenous retroelements such as long-interspersed nuclear elements (LINE) and Alu. Here, we show that APOBEC3G, but not other APOBEC3 family members, binds 7SL RNA, the common ancestor of Alu RNAs that is specifically recruited into HIV virions. Our data further indicate that APOBEC3G recognizes 7SL RNA and Alu RNA by its common structure, the Alu domain, suggesting a mechanism for APOBEC3G-mediated inhibition of Alu retrotransposition. However, we also demonstrate that APOBEC3F and APOBEC3G are normally recruited into and inhibit the infectivity of [increment]Vif HIV1 virions when 7SLRNA is prevented from accessing particles by RNA interference against SRP14 or by over expression of SRP19, both components of the signal recognition particle. We thus conclude that 7SL RNA is not an essential mediator of the virion packaging of these antiviral cytidine deaminases. http://www.retrovirology.com/content/5/1/54 Daniel Bach, Shyam Peddi, Bastien Mangeat, Asvin Lakkaraju, Katarina Strub and Didier Trono Retrovirology 2008, 5:54 2008-07-02 doi:10.1186/1742-4690-5-54 Retrovirology 1742-4690 5 54 2008-07-02 Background: Several factors determine the risk of HIV mother-to-child transmission (MTCT), such as coinfections in placentas from HIV-1 positive mothers with other pathogens. Chagas' disease is one of the most endemic zoonoses in Latin America, caused by the protozoan Trypanosoma cruzi. The purpose of the study was to determine whether T. cruzi modifies HIV infection of the placenta at the tissue or cellular level. Results: Simple and double infections were carried out on a placental histoculture system (chorionic villi isolated from term placentas from HIV and Chagas negative mothers) and on the choriocarcinoma BeWo cell line. Trypomastigotes of T. cruzi (VD lethal strain), either purified from mouse blood or from Vero cell cultures, 24h-supernatants of blood and cellular trypomastigotes, and the VSV-G pseudotyped HIV-1 reporter virus were used for the coinfections. Viral transduction was evaluated by quantification of luciferase activity. Coinfection with whole trypomastigotes, either from mouse blood or from cell cultures, decreased viral pseudotype luciferase activity in placental histocultures. Similar results were obtained from BeWo cells. Supernatants of stimulated histocultures were used for the simultaneous determination of 29 cytokines and chemokines with the Luminex technology. In histocultures infected with trypomastigotes, as well as in coinfected tissues, IL-6, IL-8, IP-10 and MCP-1 production was significantly lower than in controls or HIV-1 transducted tissue. A similar decrease was observed in histocultures treated with 24h-supernatants of blood trypomastigotes, but not in coinfected tissues. Conclusions: Our results demonstrated that the presence of an intracellular pathogen, such as T. cruzi, is able to impair HIV-1 transduction in an in vitro system of human placental histoculture. Direct effects of the parasite on cellular structures as well as on cellular/viral proteins essential for HIV-1 replication might influence viral transduction in this model. Nonetheless, additional mechanisms including modulation of cytokines/chemokines at placental level could not be excluded in the inhibition observed. Further experiments need to be conducted in order to elucidate the mechanism(s) involved in this phenomenon. Therefore, coinfection with T. cruzi may have a deleterious effect on HIV-1 transduction and thus could play an important role in viral outcome at the placental level. http://www.retrovirology.com/content/5/1/53 Guillermina Laura Dolcini, Maria Elisa Solana, Guadalupe Andreani, Ana Maria Celentano, Laura Maria Parodi, Ana Maria Donato, Natalia Elissondo, Stella Maris Gonzalez Cappa, Luis David Giavedoni and Liliana Martinez Peralta Retrovirology 2008, 5:53 2008-07-01 doi:10.1186/1742-4690-5-53 Retrovirology 1742-4690 5 53 2008-07-01 Background: More than 10 members of seven-transmembrane G protein-coupled receptors (GPCRs) have been shown to work as coreceptors for human immunodeficiency virus type 1 (HIV-1), HIV type 2 (HIV-2), and simian immunodeficiency viruses (SIVs). As a common feature of HIV/SIV coreceptors, several tyrosines are present in their amino-terminal extracellular regions (NTRs). We noticed that a receptor for N-formylpeptides, FPRL1, also contains three tyrosines in its NTR. It has been reported that monocytes expressing both CCR5 and FPRL1 in addition to CD4 are activated by ligands or agonists of FPRL1. The activated monocytes down-modulate CCR5 and, as a result, become resistant to HIV-1. Thus, FPRL1 plays effective roles in the protection of monocyptes against HIV-1 infection. However, its own coreceptor activity has not been detected. In this study, we examined the HIV/SIV coreceptor activity of FPRL1. Results: A CD4-transduced human glioblastoma cell line, NP-2/CD4, is remarkably insusceptible to HIV/SIV infection. When NP-2/CD4 cells are transduced with GPCR genes coding coreceptors, the cells become susceptible to HIV/SIV strains. Thus, NP-2/CD4 cells can be used as the reporter cells to determine the coreceptor activities of GPCRs. When NP-2/CD4 cells were transduced with FPRL1 gene, the resultant NP-2/CD4/FPRL1 cells became susceptible to several cell line-adapted HIV/SIV strains. Moreover, FPRL1 is efficiently used as a coreceptor for many primary HIV-1 isolates. Amino acids that clearly link to the FPRL1 use of HIV-1 could not be detected in the V3 loop of the Env protein. Coreceptor activity of FPRL1 was partially blocked by its ligand, forymyl-Met-Leu-Phe (fMLF) peptide. Conclusion: We conclude that FPRL1 is a novel and efficient HIV/SIV coreceptor. FPRL1 works as a bifunctional factor to HIV-1 infection, namely protective or promotive factor in different conditions. FPRL1 expression has been detected in the lung, spleen, testis, and neutrophils. We also detected FPRL1 mRNA in 293T (embryonal kidney), C8166 (T cell), HOS (osteosarcoma), Molt4#8 (T cell), U251MG (astrocytoma), U87/CD4 (CD4-transduced glioma), and peripheral blood lymphocytes. The occurrence of HIV-1 infection assisted by FPRL1 in vivo and its roles in generation and progression of acquired immune deficiency syndrome should be elucidated further. http://www.retrovirology.com/content/5/1/52 Nobuaki Shimizu, Atsushi Tanaka, Takahisa Mori, Takahiro Ohtsuki, Aliful Hoque, Atsushi Jinno-Oue, Chatchawann Apichartpiyakul, Shigeru Kusagawa, Yutaka Takebe and Hiroo Hoshino Retrovirology 2008, 5:52 2008-06-25 doi:10.1186/1742-4690-5-52 Retrovirology 1742-4690 5 52 2008-06-25 Members of the APOBEC family of cellular cytidine deaminases represent a recently identified group of proteins that provide immunity to infection by retroviruses and protect the cell from endogenous mobile retroelements. Yet, HIV-1 is largely immune to the intrinsic antiviral effects of APOBEC proteins because it encodes Vif (viral infectivity factor), an accessory protein that is critical for in vivo replication of HIV-1. In the absence of Vif, APOBEC proteins are encapsidated by budding virus particles and either cause extensive cytidine to uridine editing of negative sense single-stranded DNA during reverse transcription or restrict virus replication through deaminase-independent mechanisms. Thus, the primary function of Vif is to prevent encapsidation of APOBEC proteins into viral particles. This is in part accomplished by the ability of Vif to induce the ubiquitin-dependent degradation of some of the APOBEC proteins. However, Vif is also able to prevent encapsidation of APOBEC3G and APOBEC3F through degradation-independent mechanism(s). The goal of this review is to recapitulate current knowledge of the functional interaction of HIV-1 and its Vif protein with the APOBEC3 subfamily of proteins and to summarize our present understanding of the mechanism of APOBEC3-dependent retrovirus restriction. http://www.retrovirology.com/content/5/1/51 Ritu Goila-Gaur and Klaus Strebel Retrovirology 2008, 5:51 2008-06-24 doi:10.1186/1742-4690-5-51 Retrovirology 1742-4690 5 51 2008-06-24 Background: Prolonged, altered hematopoietic reconstitution is commonly observed in patients undergoing myeloablative conditioning and bone marrow and/or mobilized peripheral blood-derived stem cell transplantation. We studied the reconstitution of myeloid and lymphoid compartments after the transplantation of autologous CD34+ bone marrow cells following gamma irradiation in cynomolgus macaques. Results: The bone marrow cells were first transduced ex vivo with a lentiviral vector encoding eGFP, with a mean efficiency of 72%+/-4%. The vector used was derived from the simian immunodeficiency lentivirus SIVmac251, VSV-g pseudotyped and encoded eGFP under the control of the phosphoglycerate kinase promoter. After myeloid differentiation, GFP was detected in colony-forming cells (37%+/-10%). A previous study showed that transduction rates did not differ significantly between colony-forming cells and immature cells capable of initiating long-term cultures, indicating that progenitor cells and highly immature hematopoietic cells were transduced with similar efficiency. Blood cells producing eGFP were detected as early as three days after transplantation, and eGFP-producing granulocyte and mononuclear cells persisted for more than one year in the periphery. Conclusion: The transplantation of CD34+ bone marrow cells had beneficial effects for the ex vivo proliferation and differentiation of hematopoietic progenitors, favoring reconstitution of the T- and B-lymphocyte, thrombocyte and red blood cell compartments. http://www.retrovirology.com/content/5/1/50 Sonia Derdouch, Wilfried Gay, Didier Negre, Stephane Prost, Mikael Le Dantec, Benoit Delache, Gwenaelle Auregan, Thibault Andrieu, Jean-Jacques Leplat, Francois-Loic Cosset and Roger Le Grand Retrovirology 2008, 5:50 2008-06-19 doi:10.1186/1742-4690-5-50 Retrovirology 1742-4690 5 50 2008-06-19 For many years, scientists and suppliers have refered to AMV-RT as the reverse transcriptase produced by the Avian Myelobalstosis Virus. This manuscript briefly reviews the molecular basis for biological dependence of AMV for the envelope and RT proteins that are produced by its natural helper the Myeloblastosis Associated Virus (MAV). Because the wide use of the term «AMV RT» obscures scientific facts, it is worthwhile to clarify this issue for the scientific community, especially for younger scientists who might not be aware of the functional relationships that exist between these two viruses. http://www.retrovirology.com/content/5/1/49 Bernard Perbal Retrovirology 2008, 5:49 2008-06-16 doi:10.1186/1742-4690-5-49 Retrovirology 1742-4690 5 49 2008-06-16