Multi-Low-Dose Mucosal Simian Immunodeficiency Virus SIVmac239 Challenge of Cynomolgus Macaques Immunized with “Hyperattenuated” SIV Constructs

Abstract

Hyperattenuated simian immunodeficiency virus SIVmac239-derived constructs ⌬5-CMV and ⌬6-CCI are an effort to render SIV incapable of, in practical terms, both reversion and recombination while maintaining the immune features of SIV as a retrovirus. Primary inoculation of cynomolgus macaques with 10 8 50% tissue culture infective doses (TCID 50 ) of ⌬5-CMV or ⌬6-CCI induced low-level humoral and cellular responses detectable in the absence of measureable in vivo replication. The first of three DNA boosts resulted in elevated gamma interferon (IFN-␥) enzyme-linked immunospot (ELISPOT) responses to Gag, Pol, and Env in the ⌬5-CMV vaccine group compared to the ⌬6-CCI vaccine group (P ‫؍‬ 0.001). Weekly intrarectal challenge with a low dose of SIVmac239 followed by a dose escalation was conducted until all animals became infected. The mean peak viral load of the ⌬5-CMV-vaccinated animals (3.7 ؋ 10 5 copies/ml) was ϳ1 log unit lower than that of the control animals. More dramatically, the viral load set point of these animals was decreased by 3 log units compared to that of the controls (<50 versus 1.64 ؋ 10 4

Experimental Infection of Cynomolgus Macaques (Macaca fascicularis) with Human Varicella-Zoster Virus

“…For assessment of activation levels and potential target cell populations, cryopreserved PBMCs were thawed and isolated over a Percoll (GE Healthcare Bio-Sciences, NJ) gradient as described previously (38). The cells were resuspended to 2.5 ϫ 10 6 /ml in R10 medium, and 500,000 cells were plated per well in a V-bottom 96-well plate.…”

“…Flow cytometric analysis and intracellular cytokine assays. Routine complete blood counts and immunophenotyping were conducted as described previously (38). Briefly, 5,000 lymphocytes (CD45 ϩ [clone TU116]; low side scatter [SSC]) were acquired.…”

“…The cells were washed with R10 medium, centrifuged, resuspended in PBS containing 3% FBS, and stored on ice in preparation for immediate surface staining. Peripheral blood mononuclear cells (PBMCs) were obtained from whole-blood samples by Percoll density gradient separation as described previously (38).…”

A critical analysis of the cynomolgus macaque, Macaca fascicularis, as a model to test HIV-1/SIV vaccine efficacy

“…While most early vaccine trials were performed with single high dose inocula in an effort to ensure that all animals became infected, this approach has been modified so as to better replicate the natural low in vivo acquisition rates. In this respect, low dose repeated challenge models are being used in which a low virus dose requires several or many challenges through various mucosal routes to infect macaques, but also sometimes systemically, the end point however remains the infection of all animals [39].…”

Simian-Human Immunodeficiency Viruses and Their Impact on Non-Human Primate Models for AIDS

“…Cynomolgus macaques of Philippine origin were infected intrarectally with multiple-low dose exposures to SIVmac239. However, there was a need for an escalating dose regimen to infect some of the macaques [162].Cynomolgus macaques are susceptible to infection by the rectal route with SIVsm, but have lower steady state plasma RNA concentrations than rhesus macaques [163]. Successful intrarectal inoculation of cynomolgus macaques with a single high dose of SIVmac239 and the ability to generate escape variants to CD8 T-cell responses has been demonstrated as well [164,165].…”