Characterization of simian and human immunodeficiency chimeric viruses re-isolated from vaccinated macaque monkeys after challenge infection.

Monkeys that have been vaccinated with nef-deleted SHIVs were either fully or partially protected against challenge with acute pathogenic SHIV-89.6 P. Viruses isolated from these vaccinated monkeys were all found to be the 89.6 P challenge virus using PCR amplification and restriction enzyme analysis of the env region of the viruses. Analysis of the 3'-end of the env region and 5'-half of the nef region using a heteroduplex mobility assay revealed that the parental 89.6 P and re-isolated viruses from unvaccinated 89.6 P-infected monkeys had quite an abundant and similar heterogeneous quasispecies population. In contrast, the viruses isolated from the vaccinated monkeys had different and fewer quasispecies indicating a selective immune pressure in the vaccinated monkeys. The in vitro replication of the viruses isolated from the vaccinated monkeys in human and macaque peripheral blood mononucular cells (PBMCs) as well as in established cell lines such as M8166 and HSC-F cells, were slow and delayed when compared to the parental 89.6 P and re-isolated viruses from unvaccinated 89.6 P-infected monkeys. Further comparison revealed that in HSC-F cells the viruses from vaccinated monkeys again showed delayed and weak CD4(+) cell down-modulation as well as having little or no effect on cell growth or cell viability on HSC-F cells and monkey PBMC. Thus we noticed that these re-isolated 89.6 P viruses from the vaccinated monkeys had changed or had been selected for low pathogenic viruses in the monkeys. This suggests that though the vaccination did not completely prevent the replication of the challenge virus in the monkeys it did contain the challenge virus by suppressing the pathogenic variants. This further enhances the prospects of this nef-deleted SHIV as the bases for effective anti-HIV vaccine candidates.

Cytokine kinetics in the plasma of monkeys infected with pathogenic and nonpathogenic simian and human immunodeficiency chimeric viruses at an early stage of infection.

To evaluate the pattern of cytokines as a result of pathogenic and nonpathogenic SHIV infections in monkeys, we analyzed the cytokines interleukin (IL)-2, IL-4, IL-10, IL-12, and interferon (IFN)-gamma in the plasma of 8 monkeys infected with either pathogenic 89.6P or nonpathogenic NM-3rN chimeric viruses. The cytokine kinetics in the 89.6P-infected monkeys was characterized by increases of IL-2, IL-10, and to some extent IFN-gamma and a decrease of IL-12. Although that of NM-3rN-infected monkeys was characterized by an increase of IFN-gamma, and a transient decrease of IL-12. IL-4 was not detected in any of the monkeys. The results, therefore, showed a mixture of Th-1 and Th-2 cytokine profiles implying these cytokines are not clear enough to use as an index of the pathogenicity of the viruses at an early stage of infection.

Construction of an SIV/HIV type 1 chimeric virus with the human interleukin 6 gene and its production of interleukin 6 in monkey and human cells.

The switch from a Th1- to a Th2-type cytokine response is reported to be involved in human immunodeficiency virus (HIV) disease progression. To study the effect of IL-6, one of the Th2-type cytokines, on AIDS pathogenesis, we constructed an SIV/HIV-1 chimeric virus (SHIV) having the human IL-6 gene (SHIV-IL6) SHIV-IL6 could replicate in M8166, a human T cell line, as well as in monkey and human peripheral blood mononuclear cells (PBMCs). Along with the SHIV-IL6 replication, IL-6 was detected in the culture supernatant by ELISA. The maximum level of IL-6 was 35, 15, and 8 ng/ml in M8166, human PBMCs, and monkey PBMCs, respectively. The expressed IL-6 was biologically active as shown by the proliferation of IL-6-dependent murine hybridoma (MH-60) cells. The inserted IL-6 gene was stable for at least four passages (45 days after the initial infection) in M8166 cells, suggesting the ability to achieve stable expression of IL-6 in long-term experiments. Therefore, we successfully established an SHIV system expressing IL-6, and this is the first report of an SHIV expressing a Th2-type cytokine. With this system, IL-6 should be expressed in the regions where the virus replicates, and therefore the inoculation of macaque monkeys with SHIV-IL6 is expected to provide further information on the etiology of AIDS.

Plasma levels of the chemokine RANTES in macaque monkeys infected with pathogenic and non-pathogenic SIV/HIV-1 chimeric viruses at an early stage of infection.

Plasma levels of the chemokine RANTES were examined in monkeys infected with either a pathogenic simian and human immunodeficiency chimeric virus (SHIV) or a non-pathogenic SHIV to determine whether RANTES levels were related to the pathogenicity of the virus, the plasma viral load, or the kinetics of CD4+ T-cells. In the results no significant correlation was found between the RANTES kinetics and changes in the CD4+ T-cell numbers nor the plasma viral loads in any of the monkeys, although a transient decrease of the RANTES level was observed in the pathogenic virus-infected monkeys. At least, the plasma RANTES level can not be used as an index of the pathogenicity of the virus at the early stage of infection.