Fatal Immunopathogenesis by SIV/HIV-1 (SHIV) Containing a Variant Form of the HIV-1sf33 env Gene in Juvenile and Newborn Rhesus Macaques

Abstract

SIV/HIV-1 (SHIV) chimeric clones, constructed by substituting portions of the pathogenic molecular clone SIVmac239 with counterpart portions from HIV-1 clones, provide a means to analyze functions of selected HIV-1 genes in vivo in nonhuman primates. Our studies focused on SHIVSF33, which contains the vpu, tat, rev, and env genes of the cytopathic, T-cell line tropic clone HIV-1sf33 (subtype-B); this clone has a premature stop codon in the vpu gene. In three juvenile macaques inoculated intravenously with SHIVSF33, low-level persistent infection was established; no disease was observed for a period of >2 years. However, at approximately 16 months p.i., one of four SHIVSF33-infected juvenile macaques exhibited an increase in virus load, depletion of CD4(+) T cells in peripheral blood and lymph nodes, and other symptoms of simian AIDS (SAIDS). Virus recovered from this animal in the symptomatic stage was designated SHIVSF33a (A, adapted); this virus displayed multiple amino acid sequence changes throughout the HIV-1 env gene compared with the input SHIVSF33 clone. Additionally, a mutation in all clones from SHIVSF33a restored the open reading frame for the vpu gene. In vitro evaluations in tissue-culture systems revealed that SHIVSF33a replicated to higher levels and exhibited greater cytopathicity than SHIVSF33. Furthermore cloned env genes for SHIVSF33a were more fusogenic in a cell-fusion assay compared with the env gene of the SHIVSF33. Intravenous inoculation of SHIVsf33a into juvenile and newborn macaques resulted in a rapid decline in CD4(+) T cells to very low levels and development of a fatal AIDS-like disease. A cell-free preparation of this pathogenic chimeric virus also established persistent infection when applied to oral mucosal membranes of juvenile macaques and produced a fatal AIDS-like disease. These studies on pathogenic SHIVSF33a establish the basis for further investigations on the role of the HIV-1 env gene in virus adaptation and in mechanism(s) of immunodeficiency in primates; moreover, the chimeric virus SHIVSF33a can play a role in elucidating mucosal membrane transmission and development of antiviral vaccines in newborns as well as juvenile and adult macaques.

Induction of Simian AIDS in Infant Rhesus Macaques Infected with CCR5- or CXCR4-Utilizing Simian-Human Immunodeficiency Viruses Is Associated with Distinct Lesions of the Thymus

“…All viral stocks were quantitated for viral RNA by real-time reverse transcriptase-PCR (RT-PCR) (see below) and for SIV p27 gag by enzyme-linked immunosorbent assay (Beckman Coulter, Hialeah, Fla.). SHIV SF33A was prepared by passage in CEMX174 cells as previously described (28 Immunophenotypic characterization of peripheral blood lymphocytes was performed with a FACscan flow cytometer (BD Biosciences, San Jose, Calif.) together with monoclonal antibodies specific for CD3 (SP34), CD4 (M-T477), and CD8 (SK1), all obtained from BD Biosciences. Staining was performed with 50 l of whole blood or purified cells (10 6 to 10 7 /ml) in phosphate-buffered saline-0.5% bovine serum albumin.…”

“…Experimental infection of newborn Asian macaques with selected strains of simian immunodeficiency virus (SIV), or chimeric simian-human immunodeficiency virus (SHIV) causes a fatal AIDS-like disease that closely recapitulates the spectrum of disease in HIV-1-infected children (2,5,28,30). We selected two phenotypically distinct SHIV strains for in vivo studies in infant rhesus macaques: SHIV SF33A utilizes the CXCR4 coreceptor and produces a rapid decline of CD4 ϩ T cells in peripheral blood in both infant and adult macaques, and SHIV SF162P3 utilizes the CCR5 coreceptor and causes depletion of CD4 ϩ T cells in the gastrointestinal tract in adult macaques (14,28,29).…”

“…We selected two phenotypically distinct SHIV strains for in vivo studies in infant rhesus macaques: SHIV SF33A utilizes the CXCR4 coreceptor and produces a rapid decline of CD4 ϩ T cells in peripheral blood in both infant and adult macaques, and SHIV SF162P3 utilizes the CCR5 coreceptor and causes depletion of CD4 ϩ T cells in the gastrointestinal tract in adult macaques (14,28,29). We report that both of these SHIV strains induce simian AIDS in infant macaques but that each strain is associated with distinct patterns of viral expression and pathology in the thymus.…”

Properties of the Surface Envelope Glycoprotein Associated with Virulence of Simian-Human Immunodeficiency Virus SHIV SF33A Molecular Clones

“…Comparative studies of SHIVs that use CXCR4 and the CCR5 coreceptor (X4 and R5 SHIVs, respectively) have revealed the role of tropism in the rate and localization of CD4 ϩ T-cell depletion (19). Pathogenic X4 SHIVs typically cause a severe depletion of CD4 ϩ T lymphocytes in blood and peripheral lymph nodes within 1 month of infection (14,21,27,36). Pathogenic isolates of dualtropic R5X4 SHIVs also cause rapid CD4 ϩ T-cell depletion (29,46,50), while pathogenic R5 SHIVs cause a more protracted decrease of peripheral CD4 ϩ T cells similar to that seen in SIVmac infection (18).…”

Viral Protein U (Vpu)-Mediated Enhancement of Human Immunodeficiency Virus Type 1 Particle Release Depends on the Rate of Cellular Proliferation

“…Although HIV strains replicating in vitro often exhibit mutations that abrogate Vpu expression, in vivo the Vpu open reading frame remains intact (12). In addition, macaque models of simian-human immunodeficiency virus infections have shown that during the nonpathogenic stages of disease, the Vpu reading frame is often disrupted, but as the virus evolves and becomes more pathogenic, the Vpu reading frame is often found to be intact (24)(25)(26). Finally, HIV-1 infection of certain primary cells, such as terminally differentiated, nondividing macrophages, generally requires Vpu (2,33).…”