Challenge of Chimpanzees Immunized with a Recombinant Canarypox-HIV-1 Virus

AbstractTo evaluate the potential protective efficacy of a live recombinant human immunodeficiency virus type 1 (HIV-1) canarypox vaccine candidate, two chimpanzees were immunized five times with ALVAC-HIV-1 vCP250, a recombinant canarypox virus that expresses the HIV-1IIIB(LAI)gp120/TM,gag,and protease gene products. One month after the last booster inoculation, the animals were challenged by intravenous injection of cell-associated virus in the form of peripheral blood mononuclear cells from an HIV-1IIIB(LAI)-infected chimpanzee. One chimpanzee with a neutralizing antibody titer to HIV-1IIIB(LAI)of 128 at the time of challenge was protected, whereas both the second animal, with a neutralizing antibody titer of 32, and a naive control animal became infected. At 5 months after challenge, the protected chimpanzee and a third animal, previously immunized with various HIV-1MNantigens, were given a booster inoculation. The two animals were challenged intravenously 5 weeks later with twenty 50% tissue culture infectious doses of cell-free HIV-1DH12, a heterologous subtype B isolate. Neither chimpanzee had neutralizing antibodies to HIV-1DH12, and neither one was protected from infection with this isolate. The immune responses elicited by vaccination against HIV-1IIIB(LAI)or HIV-1MNdid not, therefore, protect the animals from challenge with the heterologous cell-free HIV-1DH12

Differential Selection of Specific Human Immunodeficiency Virus Type 1/JC499 Variants after Mucosal and Parenteral Inoculation of Chimpanzees

Regardless of the route of transmission, it is generally accepted that the human immunodeficiency virus type 1 (HIV-1) quasispecies transmitted from an infected individual to an uninfected individual is genetically homogeneous. This finding and the observation that HIV-1 genotypes in recipients are minor variants in the donors suggest strongly that selection for specific variants occurs. However, most analyses have been limited to the V3 region of env. In addition, the exact time at which most new infections occurred was not known, making it almost impossible to analyze virus populations present in donor-recipient pairs at the time of HIV-1 transmission. To circumvent this problem, three chimpanzees were inoculated with a genetically defined stock of cell-free HIV-1/JC499 by one of three routes: intravenously or via the cervical or penile mucosa. PCR products of the C2-to-V5 region of env were amplified from both proviral DNA and virion RNA in blood samples collected soon after infection and were screened by heteroduplex analysis (HDA). Those PCR products with distinct HDA banding patterns were cloned and sequenced. In all three animals, transmitted variants encoded one of two V3-loop populations identified in the inoculum, indicating relative homogeneity in this region. However, different virus populations, defined by combinations of specific V4 and V5 sequences, were found when variants in the animal inoculated intravenously (at least 13 V4-plus-V5 combinations) were compared with those in the two animals inoculated by the mucosal routes (limited to only four V4-plus-V5 combinations). The only V4-plus-V5 population in variants found in all three chimpanzees was the major population in the inoculum, which contained viruses with more than 30 different V4-plus-V5 combinations. That the majority of the V4-plus-V5 genotypes in variants transmitted to all three animals were minor populations in the inoculum indicated that selective transmission defined by the V4-plus-V5 regions had occurred but that distinct populations were transmitted by parenteral versus mucosal routes. These results indicate that the putative homogeneity of HIV-1 variants in a newly infected individual might be an artifact of the region of the env gene evaluated and that regions other than V3 might play a major role in selective transmission

Mobilization of CD34+ Progenitor Cells in Association with Decreased Proliferation in the Bone Marrow of Macaques after Administration of the Fms-Like Tyrosine Kinase 3 Ligand ▿

Fms-like tyrosine kinase 3 ligand (FLT3-L) is critical for the differentiation and self-renewal of CD34+ progenitor cells in primates and has been used therapeutically to mobilize progenitor and dendritic cells in vivo. However, little is known regarding the expansion of progenitor cells outside of peripheral blood, particularly in bone marrow (BM), where progenitor cells primarily reside. Evaluation of FLT3-L-mediated cell mobilization during lentivirus infections, where the numbers of CD34+ progenitor cells are reduced, is limited. We enumerated frequencies and absolute numbers of CD34+ progenitor cells in blood and BM of naive and SIV- or SHIV-infected macaques during and after the administration of FLT3-L. Flow cytometric analyses revealed that, while CD34+ cells increased in the circulation, no expansion was observed in BM. Furthermore, in the BM intracellular Ki67, a marker of cell proliferation, was downregulated in CD34+ progenitor cells but was upregulated significantly in the bulk cell population. Although the exact mechanism(s) remains unclear, these data suggest that CD34+ cell mobilization in blood was the result of cellular emigration from BM and not the proliferation of CD34+ cells already in the periphery. It is possible that the decreased progenitor cell proliferation observed in BM is evidence of a negative regulatory mechanism preventing hyperproliferation and development of neoplastic cells

Simian Immunodeficiency Virus (SIV)/Immunoglobulin G Immune Complexes in SIV-Infected Macaques Block Detection of CD16 but Not Cytolytic Activity of Natural Killer Cells

Natural killer cells are components of the innate immune system that play an important role in eliminating viruses and malignant cells. Using simian immunodeficiency virus (SIV) infection of macaques as a model, flow cytometry revealed a gradual loss of CD16(+) NK cell numbers that was associated with disease progression. Of note, the apparent loss of NK cells was detected in whole-blood samples but not in isolated peripheral blood mononuclear cells (PBMC), suggesting that an inhibitor(s) of the antibody used to detect CD16, the low-affinity immunoglobulin G (IgG) receptor, was present in blood but was removed during PBMC isolation. (Actual decreases in CD16(+) cell numbers in PBMC generally were not detected until animals became lymphopenic.) The putative decrease in CD16(+) cell numbers in whole blood correlated with increasing SIV-specific antibody titers and levels of plasma virion RNA. With the addition of increasing amounts of plasma from progressor, but not nonprogressor, macaques to PBMC from an uninfected animal, the apparent percentage of CD16(+) cells and the mean fluorescence intensity of antibodies binding to CD16 declined proportionately. A similar decrease was observed with the addition of monomeric IgG (mIgG) and IgG immune complexes (IgG-ICs) purified from the inhibitory plasma samples; some of the ICs contained SIV p27(gag) antigen and/or virions. Of interest, addition of purified IgG/IgG-ICs to NK cell lytic assays did not inhibit killing of K562 cells. These results indicate that during progressive SIV and, by inference, human immunodeficiency virus disease, CD16(+) NK cell numbers can be underestimated, or the cells not detected at all, when one is using a whole-blood fluorescence-activated cell sorter assay and a fluorochrome-labeled antibody that can be blocked by mIgG or IgG-ICs. Although this blocking had no apparent effect on NK cell activity in vitro, the in vivo effects are unknown

Protection against lethal simian immunodeficiency virus SIVsmmPBj14 disease by a recombinant Semliki forest virus gp160 vaccine and by a gp120 subunit vaccine

SCOPUS: ar.jinfo:eu-repo/semantics/publishe