Generation of the Pathogenic R5-Tropic SHIVAd8 by Serial Passaging in Rhesus Macaques.

Laboratory of Molecular Microbiology, National Institutes of Health, Bethesda, MD 20892-0460, USA.
Journal of Virology (Impact Factor: 4.44). 02/2010; 84(9):4769-81. DOI: 10.1128/JVI.02279-09
Source: PubMed


A new pathogenic R5-tropic simian/human immunodeficiency virus (SHIV) was generated following serial passaging in rhesus macaques. All 13 animals inoculated with SHIV(AD8) passaged lineages experienced marked depletions of CD4(+) T cells. Ten of these infected monkeys became normal progressors (NPs) and had gradual losses of both memory and naïve CD4(+) T lymphocytes, generated antiviral CD4(+) and CD8(+) T cell responses, and sustained chronic immune activation while maintaining variable levels of plasma viremia (10(2) to 10(5) RNA copies/ml for up to 3 years postinfection [p.i.]). To date, five NPs developed AIDS associated with opportunistic infections caused by Pneumocystis carinii, Mycobacterium avium, and Campylobacter coli that required euthanasia between weeks 100 and 199 p.i. Three other NPs have experienced marked depletions of circulating CD4(+) T lymphocytes (92 to 154 cells/microl) following 1 to 2 years of infection. When tested for coreceptor usage, the viruses isolated from four NPs at the time of their euthanasia remained R5 tropic. Three of the 13 SHIV(AD8)-inoculated macaques experienced a rapid-progressor syndrome characterized by sustained plasma viremia of >1 x 10(7) RNA copies/ml and rapid irreversible loss of memory CD4(+) T cells that required euthanasia between weeks 19 and 23 postinfection. The sustained viremia, associated depletion of CD4(+) T lymphocytes, and induction of AIDS make the SHIV(AD8) lineage of viruses a potentially valuable reagent for vaccine studies.

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Available from: Tatsuhiko Igarashi,
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    • "Peripheral lymph nodes were found to be the preferred sites of X4 emergence and expansion in macaques infected with R5 SHIVs [42,51,52]. Because longitudinal samples (w8, 46, 54, 84) from the inguinal lymph node (Ing LN) of FF94 were available, we analyzed this tissue compartment as well as the PBMC and serum samples collected at the corresponding time points for X4 emergence in this animal. "
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    ABSTRACT: Background Mucosally transmissible and pathogenic CCR5 (R5)-tropic simian-human immunodeficiency virus (SHIV) molecular clones are useful reagents to identity neutralization escape in HIV-1 vaccine experiments and to study the envelope evolutionary process and mechanistic basis for coreceptor switch during the course of natural infection. Results We observed progression to AIDS in rhesus macaques infected intrarectally with molecular clones of the pathogenic R5 SHIVSF162P3N isolate. Expansion to CXCR4 usage was documented in one diseased macaque that mounted a neutralizing antibody response and in another that failed to do so, with the latter displaying a rapid progressor phenotype. V3 loop envelop glycoprotein gp120 sequence changes that are predictive of a CXCR4 (X4)-using phenotype in HIV-1 subtype B primary isolates, specifically basic amino acid substations at positions 11 (S11R), 24 (G24R) and 25 (D25K) of the loop were detected in the two infected macaques. Functional assays showed that envelopes with V3 S11R or D25K mutation were dual-tropic, infecting CD4+ target cells that expressed either the CCR5 or CXCR4 coreceptor. And, consistent with findings of coreceptor switching in macaques infected with the pathogenic isolate, CXCR4-using variant was first detected in the lymph node of the chronically infected rhesus monkey several weeks prior to its presence in peripheral blood. Moreover, X4 emergence in this macaque coincided with persistent peripheral CD4+ T cell loss and a decline in neutralizing antibody titer that are suggestive of immune deterioration, with macrophages as the major virus-producing cells at the end-stage of disease. Conclusions The data showed that molecular clones derived from the R5 SHIVSF162P3N isolate are mucosally transmissible and induced disease in a manner similar to that observed in HIV-1 infected individuals, providing a relevant and useful animal infection model for in-depth analyses of host selection pressures and the env evolutionary changes that influence disease outcome, coreceptor switching and vaccine escape.
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    • "However, one would argue that IHR-mediated generation of SHIV does not allow for a detailed genetic analysis, such as mutagenesis of particular gene(s), because of the virus being ''swarm.'' While this is undeniable, the vast majority of currently available replicationcompetent SHIVs are resultants of evolution through animal-toanimal passage and exist as quasispecies (Joag et al., 1996 #49; Reimann et al., 1996a #52; Igarashi et al., 1999 #156; Harouse et al., 2001 #154; Song et al., 2006 #158; Nishimura et al., 2010 #157}. A molecular-cloned virus representing the properties of the swarm is attainable by introduction of consensus sequences to a molecular clone, if necessary. "
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    • "Infection with X4-tropic SHIVs such as SHIV89.6P results in acute CD4+ T cell depletion, while R5-tropic SHIVs such as SHIV162P3 induce persistent infection leading to chronic disease progression (Tsai et al., 2007; Nishimura et al., 2010; Zhuang et al., 2011). These SHIVs are useful especially for the analysis of Env-specific antibody responses (Ng et al., 2010; Watkins et al., 2011). "
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