Novel Escape Mutants Suggest an Extensive TRIM5α Binding Site Spanning the Entire Outer Surface of the Murine Leukemia Virus Capsid Protein

After entry into target cells, retroviruses encounter the host restriction factors such as Fv1 and TRIM5α. While it is clear that these factors target retrovirus capsid proteins (CA), recognition remains poorly defined in the absence of structural information. To better understand the binding interaction between TRIM5α and CA, we selected a panel of novel N-tropic murine leukaemia virus (N-MLV) escape mutants by a serial passage of replication competent N-MLV in rhesus macaque TRIM5α (rhTRIM5α)-positive cells using a small percentage of unrestricted cells to allow multiple rounds of virus replication. The newly identified mutations, many of which involve changes in charge, are distributed over the outer ‘top’ surface of N-MLV CA, including the N-terminal β-hairpin, and map up to 29 Ao apart. Biological characterisation with a number of restriction factors revealed that only one of the new mutations affects restriction by human TRIM5α, indicating significant differences in the binding interaction between N-MLV and the two TRIM5αs, whereas three of the mutations result in dual sensitivity to Fv1n and Fv1b. Structural studies of two mutants show that no major changes in the overall CA conformation are associated with escape from restriction. We conclude that interactions involving much, if not all, of the surface of CA are vital for TRIM5α binding

Identification and phylogenetic characterization of HTLV-I from a native inhabitant of Easter Island (Rapa Nui)

en que se dividen las islas del Pacífico siendo esta área endémica para el virus humano linfotrópico de células T tipo I (HTLV-I). Mientras tanto las otras dos regiones como la Polinesia y la Micronesia tienen una muy baja incidencia del virus. En un esfuerzo por interiorizarmos mejor sobre la prevalencia del virus en estas regiones de Océano Pacífico se hizo un estudio seroepidemiológico en la isla de Pascua, localizada en el extremo este de la Polinesia. En una investigación en 138 sujetos que incluía 108 rapanuis, realizado en la Isla de Pascua, se identificó un caso seropositivo para HTLV-J entre los pascuenses. Se aisló un nuevo HTLV-I derivado de un portador (E-12) que fue filogenéticamente analizado para entender el origen y la ancestral propagación del HTLV-I a la isla. Este análisis demostró que el virus aislado de E-12 pertenece al sub-grupo A del Grupo Cosmopolita y que difiere claramente del HTLV-I encontrado en la Melanesia que es reconocido como altamente divergente. En el subgrupo A, E-12 es asociado con el HTLV-I sudamericano, que incluye todas aquellas cepas encontradas entre los indígenas de América del Sur. Este resultado sugiere que el virus aislado tiene un origen Sudamericano más que Melanésico

High Prevalence of Simian T-Lymphotropic Virus Type L in Wild Ethiopian Baboons

Simian T-cell leukemia viruses (STLVs) are the simian counterparts of human T-cell leukemia viruses (HTLVs). A novel, divergent type of STLV (STLV-L) from captive baboons was reported in 1994, but its natural prevalence remained unclear. We investigated the prevalence of STLV-L in 519 blood samples from wild-living nonhuman primates in Ethiopia. Seropositive monkeys having cross-reactive antibodies against HTLV were found among 22 out of 40 hamadryas baboons, 8 of 96 anubis baboons, 24 of 50 baboons that are hybrids between hamadryas and anubis baboons, and 41 of 177 grivet monkeys, but not in 156 gelada baboons. A Western blotting assay showed that sera obtained from seropositive hamadryas and hybrid baboons exhibited STLV-L-like reactivity. A PCR assay successfully amplified STLV sequences, which were subsequently sequenced and confirmed as being closely related to STLV-L. Surprisingly, further PCR showed that nearly half of the hamadryas (20 out of 40) and hybrid (19 out of 50) baboons had STLV-L DNA sequences. In contrast, most of the seropositive anubis baboons and grivet monkeys carried typical STLV-1 but not STLV-L. These observations demonstrate that STLV-L naturally prevails among hamadryas and hybrid baboons at significantly high rates. STLV-1 and -2, the close relative of STLV-L, are believed to have jumped across simian-human barriers, which resulted in widespread infection of HTLV-1 and -2. Further studies are required to know if STLV-L is spreading into human populations