Feline immunodeficiency virus (FIV) is a member of the Retroviridae family. It is the causative agent of an acquired immunodeficiency syndrome (AIDS) in cats and wild felines. Its capsid protein (CA) drives the assembly of the viral particle, which is a critical step in the viral replication cycle. Here, the first atomic structure of full-length FIV CA to 1.67 Å resolution is determined. The crystallized protein exhibits an original tetrameric assembly, composed of dimers which are stabilized by an intermolecular disulfide bridge induced by the crystallogenesis conditions. The FIV CA displays a standard α-helical CA topology with two domains, separated by a linker shorter than other retroviral CAs. The β-hairpin motif at its amino terminal end, which interacts with nucleotides in HIV-1, is unusually long in FIV CA. Interestingly, this functional β-motif is formed in this construct in the absence of the conserved N-terminal proline. The FIV CA exhibits a cis Arg–Pro bond in the CypA-binding loop, which is absent in known structures of lentiviral CAs. This structure represents the first tri-dimensional structure of a functional, full-length FIV CA.

Human C-reactive protein (CRP) is an acute phase protein, which harbours both host defence and scavenging properties. In this study, we obtained two new crystal forms of CRP, where CRP forms a symmetric, staggered dimer of pentamers. In one of these structures, obtained in the presence of HIV-1 Tat protein, this dimer of pentamers is stabilized by two zinc ions trapped within a cleft of the effector face of CRP. These two decameric interfaces involve complementary surfaces of CRP pentamers and bury a large area of ~2000 Å(2) per pentamer, suggesting a biological role of this interface. These two novel decameric interfaces and the involvement of zinc might have important consequences in the understanding of CRP biological functions.

Feline immunodeficiency virus (FIV) is a member of the retroviridae family of viruses. It causes acquired immunodeficiency syndrome (AIDS) in worldwide domestic and non-domestic cats and is a cause of an important veterinary issue. The genome organization of FIV and the clinical characteristics of the disease caused by FIV are similar to human immunodeficiency virus (HIV). Both viruses infect T lymphocytes, monocytes, and macrophages, with a similar replication cycle in infected cells. Thus, the infection of cats with FIV is also a useful tool for the study and development of novel drugs and vaccines against HIV. Anti-retroviral drugs studied extensively with regards to HIV infection have targeted different steps of the virus replication cycle: (1) disruption of the interaction with host cell surface receptors and co-receptors; (2) inhibition of fusion of the virus and cell membranes; (3) blocking of the reverse transcription of viral genomic RNA; (4) interruption of nuclear translocation and integration of viral DNA into host genomes; (5) prevention of viral transcript processing and nuclear export; and (6) inhibition of virion assembly and maturation. Despite the great success of anti-retroviral therapy in slowing HIV progression in humans, a similar therapy has not been thoroughly investigated for FIV infection in cats, mostly because of the little structural information available for FIV proteins. The FIV capsid protein (CA) drives the assembly of the viral particle, which is a critical step in the viral replication cycle. During this step, the CA protein oligomerizes to form a protective coat that surrounds the viral genome. In this work, we perform a large-scale screening of four hundred molecules from our in-house library using an in vitro assembly assay of p24, combined with microscale thermophoresis, to estimate binding affinity. This screening led to the discovery of around four novel hits that inhibited capsid assembly in vitro. These may provide new antiviral drugs against FIV.

Feline immunodeficiency virus (FIV) is a member of the retroviridae family of viruses.

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