Molecular Medicine Partnership UnitResearch Groups
Interfering with assembly and maturation of infectious HIV-1
Hans-Georg Kräusslich and John Briggs
John Briggs and Hans-Georg Kräusslich
HIV-1, the causative agent of AIDS, is a major human pathogen with >30 million infected people world-wide and several million deaths annually. More than twenty drugs targeting different stages of HIV replication are in clinical use, but there is still an urgent need for new antivirals. Rapid and wide-spread resistance and side effects of available drugs limit the currently available therapeutic arsenal. We apply a combination of virology with state-of-the-art electron microscopy methods to decipher the architecture and dynamic alterations of HIV during assembly and maturation. Applying these methods, we aim to (i) understand how the virus develops resistance against existing drugs, (ii) how novel drugs and drug candidates work and (iii) obtain sufficiently detailed structural information to inform structure-based drug design of compounds blocking formation of the virion.
Assembly and budding of HIV is directed by the viral Gag polyprotein. The virus is initially released as immature non-infectious particle consisting of mostly uncleaved Gag polyproteins. Extracellular maturation occurs after proteolytic processing of Gag at five different cleavage sites which is mediated by the virus-encoded, virion-associated protease (PR), translated as part of the Gag-Pol polyprotein. The immature virion consists of 2 - 3,000 Gag polyproteins arranged as spherical protein shell. Maturation leads to disassembly of the immature Gag layer, followed by a second assembly stage forming the mature cone-shaped capsid. Maturation and thus infectivity can be blocked by PR inhibitors, which are a mainstay of current anti-HIV therapy. Assembly of the immature as well as of the mature structure appear to be good antiviral targets, though only few compounds have been reported so far to affect these stages. The virion protein shell constitutes an irregular, heterogeneous structure, which makes structural analysis challenging. Cryo electron microscopy in combination with virology techniques is particularly suitable to overcome structural heterogeneity and to provide a higher resolution picture of the structures of the immature and mature virions as well as their intermediates. By doing so, these approaches will also provide the basis for an understanding of resistance to current drugs, define the mechanism of new compounds and identify new targets for structure-based drug development.
Research Goal 1: PI resistance
Protease inhibitors (PI) have been a key factor in the success of HIV therapy, but as with all clinically used drugs resistance has been observed.
Research Goal 2: Assembly inhibitors
Assembly of both the immature and the mature lattice appear to be good targets for antiviral agents, as multiple weak interactions must cooperate to achieve the ordered protein shell.
Research Goal 3: Structure to inform drug design
To understand the assembly of the immature virus and to development new compounds directed against this structure, it is important to obtain a high-resolution structural view of the immature virus.
Cryo-electron microscopy of tubular arrays of HIV-1 Gag resolves structures essential for immature virus assembly.
Bharat, T.A., Castillo Menendez, L.R., Hagen, W.J., Lux, V., Igonet, S., Schorb, M., Schur, F.K., Krausslich, H.G. & Briggs, J.A.
Proc Natl Acad Sci U S A. 2014 May 19. pii: 201401455. Europe PMC
The NC domain of Gag is dispensable for actin incorporation into HIV-1 and for association of viral budding sites with cortical F-actin.
Stauffer S1, Rahman SA, de Marco A, Carlson LA, Glass B, Oberwinkler H, Herold N, Briggs JA, Müller B, Grünewald K, Kräusslich HG.
J Virol. 2014 Apr 30. [Epub ahead of print]
Role of the SP2 Domain and Its Proteolytic Cleavage in HIV-1 Structural Maturation and Infectivity
de Marco, A., Heuser, A.M., Glass, B., Krausslich, H.G., Muller, B. & Briggs, J.A.
J Virol. 2012 Dec;86(24):13708-16. doi: 10.1128/JVI.01704-12. Epub 2012 Oct 10
The molecular architecture of HIV.
Briggs, J. A. Krausslich, H. G.
J Mol Biol 2011 410, 491-500. (Review)
Structural analysis of HIV-1 maturation using cryo-electron tomography.
de Marco, A., Muller, B., Glass, B., Riches, J. D., Krausslich, H. G. Briggs, J. A.
PLoS Pathog 2010 6, e1001215.
Cryo electron tomography of native HIV-1 budding sites.
Carlson, L. A., de Marco, A., Oberwinkler, H., Habermann, A., Briggs, J. A., Krausslich, H. G. Grunewald, K.
PLoS Pathog 2010 6, e1001173.
Structure and assembly of immature HIV.
Briggs, J. A., Riches, J. D., Glass, B., Bartonova, V., Zanetti, G. Krausslich, H. G.
Proc Natl Acad Sci U S A 2009 106, 11090-5.