Identification of Highly Attenuated Mutants of Simian Immunodeficiency Virus

Abstract

Deletion mutants of the pathogenic clone of simian immunodeficiency virus isolate 239 (SIVmac239) were derived that are missingnef, vpr, and upstream sequences (US) in the U3 region of the LTR (SIVmac239Δ3), nef, vpx, and US (SIVmac239Δ3x), and nef, vpr,vpx, and US (SIVmac239Δ4). These multiply deleted derivatives replicated well in the continuously growing CEMx174 cell line and were infectious for rhesus monkeys. However, on the basis of virus load measurements, strength of antibody responses, and lack of disease progression, these mutants were highly attenuated. Measurements of cell-associated viral load agreed well with assays of plasma viral RNA load and with the strengths of the antibody responses; thus, these measurements likely reflected the extent of viral replication in vivo. A derivative of SIVmac239 lacking vif sequences (SIVmac239Δvif) could be consistently grown only in avif-complementing cell line. This Δvif virus appeared to be very weakly infectious for rhesus monkeys on the basis of sensitive antibody tests only. The weak antibody responses elicited by SIVmac239Δvif were apparently in response to low levels of replicating virus since they were not elicited by heat-inactivated virus and the anti-SIV antibody responses persisted for greater than 1 year. These results, and the results of previous studies, allow a rank ordering of the relative virulence of nine mutant strains of SIVmac according to the following order: Δvpr > Δvpx > ΔvprΔvpx ≅ Δnef > Δ3 > Δ3x ≥ Δ4 > Δvif > Δ5. The results also demonstrate that almost any desired level of attenuation can be achieved, ranging from still pathogenic in a significant proportion of animals (Δvpr and Δvpx) to not detectably infectious (Δ5), simply by varying the number and location of deletions in these five loci.

The antiviral factor APOBEC3G improves CTL recognition of cultured HIV-infected T cells

“…It will be worth examining the contribution of A3G polymorphism in the induction of CTL responses. Simian immunodeficiency virus (SIV) might also be used to further characterize the role of A3G in CTL activation because Vif-deficient SIV replicates poorly but elicits an antibody response in macaques (Desrosiers et al, 1998).…”

Neuropathogenesis of Simian Immunodeficiency Virus in Neonatal Rhesus Macaques

“…Virion-associated SIV RNA in plasma and CSF was quantified by using a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay on an Applied Biosystems (Foster City, CA) Prism 7700 sequence detection system as described previously. 30,31 Results shown are averages of duplicate determinations. Analyses of viral RNA levels were performed by Drs.…”

Vif and the p55 Gag Polyprotein of Human Immunodeficiency Virus Type 1 Are Present in Colocalizing Membrane-Free Cytoplasmic Complexes

“…Lentiviruses such as human immunodeficiency virus type 1 (HIV-1) encode a number of genes in addition to the gag, pol, and env genes that are expressed by all replication-competent retroviruses (12,17). One of these additional genes, vif (viral infectivity factor), is expressed by all known lentiviruses except equine infectious anemia virus (40) and is essential for the pathogenic replication of lentiviruses in vivo (13,31).…”