Email: Andrea.Cimarelli[at]ens-lyon.fr
Tel: +33 (0)4 72 72 86 96
Fax: +33 (0)4 72 72 81 37

Introduction

Following virion envelope to cellular receptor engagement and subsequent membranes fusion, the viral core finds itself in the cytoplasm of the target cell. At this time the retroviral RNA genome must find its way to the nucleus for integration into the host genome to occur and productive infection to set in. The viral genome is not naked and exposed in such environment, but associated to viral protein in a nucleoprotein complex whose primary goal is to chaperone it until integration in the proviral DNA form. In such complexes, the viral RNA genome is reverse transcribed into double stranded proviral DNA, transported toward the nucleus first and inside the nucleus later and finally integrated. This series of complex events constitutes overall the early phases of the viral life cycle that deal with how the virus establishes infection in target cells. The virus must come to terms with its environment and it does so by either recruiting or diverting cellular factors to its own aims or by simply counteracting and blocking the negative action that the cell may mount against it (a cartoon view of such interplay is given in figure 1).

Our overall goal is to understand the complex relations established between virus and cell during viral infection and in brief to understand how the virus infects its target cells. Our main interest remains the study of the human immunodeficiency type I virus (HIV-1) and this is why we focus on infection of the different primary cell types targeted by HIV in vivo, i.e. lymphocytes, macrophages and dendritic cells (DCs). Given that a great deal of information may be gathered by comparison among closely or distantly related viruses, we generally carry out our studies by comparing infection by HIV-1 with that of SIV (the simian counterpart of HIV), or with that of simpler retroviruses such as the murine leukemia viruses (MLV). Differences between HIV and SIV may reveal a particular adaptation of the virus for its natural host, while differences between HIV and MLV may reveal steps specific for lentiviruses, rather than general to retroviruses. In our studies we make use of retroviral vectors, simplified version of their respective wild type viruses, that provide a simplified model with which to study viral infection in a single-round non-replicative system and by virtue of which defects can be precisely quantified and ascribed to a specific step. We do hope that the results obtained will serve our understanding of basic virology but that they may be ultimately exploited against the virus itself and serve as well gene therapy applications by virtue of the use of retroviral and lentiviral vectors currently developped and used in the laboratory

Present projects

(note that projects are indicative and only general lines of research are given)

1. Role of viral proteins in infection.
    Viral nucleoprotein complexes sometimes referred to as reverse or pre-integration complexes (RTCs or PICs, respectively) are most likely to be whimsical and of evolving nature, due to the intricacy of the tasks they are called to perform. Several viral proteins have been found to be part of them: Matrix (MA), Capsid (CA), Nucleocapsid protein (NC), reverse transcriptase (RT), integrase (IN) and the viral regulatory protein Vpr.
    What is the role of these proteins during HIV  infection and at which stage do they act? If a role in the nuclear import of the proviral DNA has been described for some of these proteins, the results remain, for the most part, controversial. We are currently addressing this complex issue using mutants of some of these viral proteins and examining the different phases of viral infection affected.
    As an example of the results that can be gathered by comparison between closely related viruses, we have determined that the viral protein Vpx coded by certain strains of SIV and by HIV-2 is absolutely required for infection of DCs despite being dispensable for infection of other cell types. This is in contrast with the situation of HIV-1 that requires no viral regulatory proteins for cell infection. These results suggest that the structural proteins Gag-Pro-Pol of HIV-1 and SIV are not equivalent (at least in DCs) and that those of HIV-1 have evolved a superior ability in infection. Given the importance that DCs have in HIV-1 pathogenesis, we are trying to identify the structural protein of HIV-1 that confers it an advantage over its SIV counterpart, as well as trying to pinpoint the function of Vpx in the infection of DCs.
2. Identification of cellular proteins involved in viral infection
    If we are on one hand focusing on the viral components that are required for viral infection, we are as well interested in those cellular proteins that, recruited during this process, have the ability to influence it. To identify such proteins we are using both a novel cellular based selection method and a more classical biochemical approach that uses Vpx as a bait for cellular protein fishing. In this search, we focus on the identification of cellular factors that play a role during infection of DCs.
3. Simple retroviruses cannot infect non-dividing cells (the importance of the exception)
    Although it is commonly accepted that simple retroviruses such as murine leukemia viruses (MLV) are impaired in the infection of non-dividing cells, as they have not evolved -contrarily to lentiviruses- to bypass an intact nuclear membrane barrier, we have recently found that primary human macrophages are the exception in which, despite the absence of cell division, MLV infection occurs rather efficiently. This exception to the rule suggests that something other than -or in addition to- the nuclear membrane barrier influences MLV’s ability to infect non-dividing cells more generally. We are now trying to identify the factors that are responsible for successful infection of macrophages by MLV.
4. Modifying virion particles of HIV to target viral accessory proteins for vaccination
   Vaccination strategies against HIV now share two common features in the induction of broad and cell-mediated anti-viral immune responses, in the hope that both these features would prevent viral spread and replication in vivo. Indeed, the targeting of multiple viral antigens appears important to provide a composite selective pressure against the virus and to decrease its ability to escape immune pressure by mutation. In this line of thoughts, we have decided to modify virion-like particles (VLPs) of HIV-1 to generate cell-mediated immune responses against the highest number of viral antigens possible. We are now beginning this project with the evaluation of the immunogenicity of a first version of such modified VLPs that contain in addition to Gag high levels of the accessory proteins Tat, Rev and Nef.

Recent Selected Publications

• Goujon C, Arfi V, Pertel T, Luban J, Lienard J, Rigal D, Darlix JL, Cimarelli A. (2008) Characterization of SIVsm/HIV-2 Vpx function in human myeloid cells. J. Virol. 2008, Oct 1. [Abstract] [PubMed]
  
• Berger G, Goujon C, Darlix JL, Cimarelli A. (2008) SIV(MAC) Vpx improves the transduction of dendritic cells with nonintegrative HIV-1-derived vectors. Gene Ther. 2008 Jul 31. [Abstract] [PubMed]
• Arfi V, Rivière L, Jarrosson-Wuillème L, Goujon C, Rigal D, Darlix JL and Cimarelli A. (2008) Characterization of the early steps of infection of primary blood monocytes by HIV-1. J. Virol. 2008, Apr 16. [Abstract] [PubMed]
  
• Goujon C, Riviere L, Jarrosson-Wuilleme L, Bernaud J, Rigal D, Darlix JL, Cimarelli A. (2007) SIVsm/HIV-2 Vpx proteins promote retroviral escape from a proteasome-dependent restriction pathway present in human dendritic cells. Retrovirology. 4(1):2. [Abstract] [Full Text] [PDF] [PubMed]
• Goujon C, Jarrosson-Wuillème L, Bernaud J, Rigal D, Darlix JL, Cimarelli A. (2006) With a little help from a friend: increasing HIV transduction of monocyte-derived dendritic cells with virion-like particles of SIV(MAC). Gene Ther. 13(12):991-4. [Abstract] [PubMed]
• Jarrosson-Wuilleme L, Goujon C, Bernaud J, Rigal D, Darlix JL, Cimarelli A. (2006) Transduction of nondividing human macrophages with gammaretrovirus-derived vectors. J Virol. 80(3):1152-9. [Abstract] [Full Text] [PDF] [PubMed]

PubMed List of all Cimarelli Publications