Takeo Kuwata

Construction of human immunodeficiency virus 1/simian immunodeficiency virus strain mac chimeric viruses having vpr and/or nef of different parental origins and their in vitro and in vivo replication

We constructed a series of human immunodeficiency virus 1 (HIV-1)/simian immunodeficiency virus strain mac (SIVmac) chimeric viruses having vpr and/or nef genes of either HIV-1 or SIVmac based on a chimeric virus with LTRs, gag, pol, vif and vpx derived from SIVmac and tar, rev, vpu and env from HIV-1. All of the chimeric viruses replicated in human and macaque peripheral blood mononuclear cells (PBMCs) and in several CD4+ human cell lines, though their growth potentials were slightly different depending on whether vpr and nef were from HIV-1 or SIVmac, or were defective. The presence of nef accelerated replication in all the cells used and the replication of each chimera appeared to reflect that of the parental virus from which nef was derived. The presence of vpr had no clear effect in human and monkey PBMCs, but the replication of each chimera was influenced by the origin of vpr in H9 and A3.01 cells. NM-3rN, which carries HIV-1 vpr and SIVmac nef, was inoculated intravenously into three rhesus monkeys, three cynomolgus monkeys and two pig-tailed monkeys. From 2 to 14 weeks after inoculation, viruses were consistently re-isolated from all the monkeys and virus loads were as high as that of SIVmac reported previously. The results indicate that infection with NM-3rN is more efficient than any of our previous chimeric viruses and suggest that NM-3rN, having HIV-1 Env, will be a useful challenge virus for evaluating AIDS vaccines based on HIV-1 Env in macaque monkeys instead of chimpanzees.

Genetic subtypes of HIV type 1 in Republic of Congo.

To assess the molecular epidemiology of HIV-1 in Republic of Congo (Congo), we investigated 29 HIV-1s obtained from 82 Congolese AIDS and ARC patients in 1996 and 1997. Part of the env region including the V3 loop was phylogenetically analyzed. The genotypes observed were varied: of 29 specimens, 12 (41 %) were subtype A, 1 (3%) was subtype D, 6 (21%) were subtype G, 6 (21%) were subtype H, 2 (7%) were subtype J, and 2 (7%) could not be classified as any known subtypes (U, unclassified). The heterogeneous profile of HIV-1 infection was different from the profiles of neighboring Central African countries. These data show that subtypes G and H as well as subtype A were circulating with high prevalence. The fact that new genetic subtypes (J and U) are circulating indicates a need for a greater surveillance for these subtypes both in Congo as well as in other parts of the world.

Protection of monkeys vaccinated with vpr- and/or nef-defective simian immunodeficiency virus strain mac/human immunodeficiency virus type 1 chimeric viruses: a potential candidate live-attenuated human AIDS vaccine.

Two simian immunodeficiency virus strain mac (SIVmac)/human immunodeficiency virus type 1(HIV-1) chimeric viruses (SHIVs), designated NM-3 and NM-3n, with env derived from HIV-1 and defective vpr (plus defective nef for NM-3), were inoculated into seven macaques. These macaques were transiently or persistently infected and most of them produced long-lasting neutralizing antibodies and Env-specific killer T cells to HIV-1 with no AIDS-like symptoms. When they were challenged with another SHIV with intact vpr and nef (designated NM-3rN), all were protected as judged by virus recovery, DNA detection by PCR and antibody responses. Anti-HIV-1 Env-specific killer T cells were considered to have played a major role in this protection, but a non-specific defence mechanism as well as specific immunity also appeared to be involved. Thus, these two non-pathogenic SHIVs induced long-lasting protective immunities in macaques, suggesting the possibility of gene-defective SHIVs as attenuated live vaccines for human use.

Association of progressive CD4+ T cell decline in SIV infection with the induction of autoreactive Antibodies

The progressive decline of CD4+ T cells is a hallmark of disease progression in human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infection. Whereas the acute phase of the infection is dominated by virus-mediated depletion of memory CD4+ T cells, chronic infection is often associated with a progressive decline of total CD4+ T cells, including the naïve subset. The mechanism of this second phase of CD4+ T cell loss is unclear and may include immune activation–induced cell death, immune-mediated destruction, and regenerative or homeostatic failure. We studied patterns of CD4+ T cell subset depletion in blood and tissues in a group of 20 rhesus macaques inoculated with derivatives of the pathogenic SIVsmE543-3 or SIVmac239. Phenotypic analysis of CD4+ T cells demonstrated two patterns of CD4+ T cell depletion, primarily affecting either naïve or memory CD4+ T cells. Progressive decline of total CD4+ T cells was observed only in macaques with naïve CD4+ T cell depletion (ND), though the depletion of memory CD4+ T cells was profound in macaques with memory CD4+ T cell depletion (MD). ND macaques exhibited lower viral load and higher SIV-specific antibody responses and greater B cell activation than MD macaques. Depletion of naïve CD4+ T cells was associated with plasma antibodies autoreactive with CD4+ T cells, increasing numbers of IgG-coated CD4+ T cells, and increased incidence of autoreactive antibodies to platelets (GPIIIa), dsDNA, and phospholipid (aPL). Consistent with a biological role of these antibodies, these latter antibodies were accompanied by clinical features associated with autoimmune disorders, thrombocytopenia, and catastrophic thrombotic events. More importantly for AIDS pathogenesis, the level of autoreactive antibodies significantly correlated with the extent of naïve CD4+ T cell depletion. These results suggest an important role of autoreactive antibodies in the CD4+ T cell decline observed during progression to AIDS.

Chimeric viruses between SIVmac and various HIV-1 isolates have biological properties that are similar to those of the parental HIV-1.

Objective:To examine the biological properties of HIV-1/SIVmac chimeric viruses from HIV-1 isolates that have different replication rates, cell tropisms and cytopathicities. Design and methods:Four chimeric viruses with gag, pol, vif, vpx, nef and long terminal repeats of SIVmac and vpr, tat, rev, vpu and env of various HIV-1 isolates were constructed and compared in vitro. Cynomolgus monkeys were inoculated with two chimeras that were replicative in monkey peripheral blood mononuclear cells (PBMC). Results:The type-specific neutralization of the chimeras by monoclonal antibodies 0.5β and μ5.5, which recognize V3 of HIV-1IIIB and HIV-1MN respectively, was observed to be similar to those of the parental viruses, HIV-1NL432, HIV-1HAN2 and HIV-1SF13. The chimeras constructed from HIV-1SF2 and HIV-1SF13, which were isolates from the same individual but from different disease stages, reflected their parental properties, that is, the isolate from the later stage was rapid–high replicating, was more cytopathic and had a wider host range. Chimeras constructed from HIV-1HAN2, HIV-1SF13 and HIV-1NL432 were infectious to macaque monkeys, although the monkeys infected with the chimera from HIV-1SF13 showed lower virus loads and shorter viremic periods than those infected with the others. Conclusions:Chimeras have in vitro properties that are similar to those of their parental HIV-1 isolates, but their growth in macaque PBMC was dependent on which HIV-1 isolate was used. Evaluation of a vaccine by challenging with viruses possessing different antigenicities has become possible in macaque monkeys using newly constructed chimeras.

Role of apoptosis induction in both peripheral lymph nodes and thymus in progressive loss of CD4+ cells in SHIV-infected macaques.

To investigate the role of apoptosis in the progressive loss of CD4+ lymphocytes in HIV infection, we have used macaques infected with SHIV, a hybrid virus of HIV and simian immunodeficiency virus (SIV). In the present study, we sequentially analyzed apoptosis induction in the acute phase of SHIV infection. Four macaques infected with a pathogenic SHIV, SHIV89.6P, and four macaques infected with a nonpathogenic SHIV, NM-3rN, were analyzed during the first 2 or 4 weeks postinfection. In the 89.6P-infected macaques the number of peripheral CD4+ cells sharply decreased at 2 weeks postinfection and was maintained below 50/microl until 4 weeks postinfection, while in the NM-3rN-infected macques the number of the CD4+ cells did not change significantly. Plasma viral loads peaked at 2 and 2-3 weeks postinfection, and the peak values were about 1 x 10(9) and 10(6)-10(7) copies/ml in the 89.6P- and the NM-3rN-infected macaques, respectively. In the 89.6P-infected macaques, Fas antigen expression and the extent of apoptosis in PBMCs and peripheral lymph nodes increased at 1-2 weeks postinfection. A high number of apoptotic cells was also observed in thymus sections 2 and 4 weeks postinfection. On the other hand, apoptosis was scarcely induced in the NM-3rN-infected macaques. These results suggest that the extent of apoptosis induction is closely correlated with the pathogenicity of SHIV and that the apoptosis induction in peripheral lymphoid tissues and thymus, where T cell maturation occurs, may play an important role in the depletion of CD4+ lymphocytes in 89.6P infection.

Infectious Molecular Clones from a Simian Immunodeficiency Virus-Infected Rapid-Progressor (RP) Macaque: Evidence of Differential Selection of RP-Specific Envelope Mutations In Vitro and In Vivo

ABSTRACT A minor fraction of simian immunodeficiency virus (SIV)-infected macaques progress rapidly to AIDS in the absence of SIV-specific immune responses. Common mutations in conserved residues of env in three SIVsmE543-3-infected rapid-progressor (RP) macaques suggest the evolution of a common viral variant in RP macaques. The goal of the present study was to analyze the biological properties of these variants in vitro and in vivo through the derivation of infectious molecular clones. Virus isolated from a SIVsmE543-3-infected RP macaque, H445 was used to inoculate six naive rhesus macaques. Although RP-specific mutations dominated in H445 tissues, they represented only 10% of the population of the virus stock, suggesting a selective disadvantage in vitro. Only one of these macaques (H635) progressed rapidly to AIDS. Plasma virus during primary infection of H635 was similar to the inoculum. However, RP-specific mutations were apparently rapidly reselected by 4 to 9 weeks postinfection. Terminal plasma from H635 was used as a source of viral RNA to generate seven full-length, infectious molecular clones. With the exception of one clone, which was similar to SIVsmE543-3, clones with RP-specific mutations replicated with delayed kinetics in rhesus peripheral blood mononuclear cells and human T-cell lines. None of the clones replicated in monocyte-derived or alveolar macrophages, and all used CCR5 as their major coreceptor. RP variants appear to be well adapted to replicate in vivo in RP macaques but are at a disadvantage in tissue culture compared to their parent, SIVsmE543-3. Therefore, tissue culture may not provide a good surrogate for replication of RP variants in macaques. These infectious clones will provide a valuable reagent to study the roles of specific viral variants in rapid progression in vivo.

A new approach to AIDS research and prevention : The use of gene-mutated HIV-1/SIV chimeric viruses for anti-HIV-1 live-attenuated vaccines

The lack of a suitable animal model is a major obstacle to developing anti‐HIV‐1 vaccines. We successfully generated an SIVmac/HIV‐1 chimeric virus (SHIV) (designated as NM‐3rN) that contains the HIV‐1 env gene and is infectious to macaque monkeys. Challenging the vaccinated macaque monkeys with NM‐3rN, we developed an evaluation system for anti‐HIV‐1 Env‐targeted vaccines. For the purpose of making the vaccine, a series of gene‐mutated SHIVs were constructed. The monkeys vaccinated with these SHIVs had long‐term anti‐virus immunities without manifesting the disease, and became resistant to a challenge inoculation with NM‐3rN. The sera from a monkey showed that, after the vaccination, the neutralizing antibodies not only against the parental HIV‐1 but also against an antigenically different HIV‐1 were raised. In vivo experiments confirmed that the vaccinated monkeys were protected from the challenge inoculum of an antigenically different SHIV‐MN. Vaccination of monkeys with the attenuated SHIVs showed that further gene‐deletion of the SHIV resulted in less immunogenicity. Nevertheless, the attenuated SHIVs had a vaccine effect against the challenge inoculation. In addition to specific immunities including neutralizing antibodies and cytotoxic T cells, a more complicated immune mechanism induced by live vaccine appears to play a role in this protection. Our data suggest that the live vaccine can induce strong and wide‐range immunity against HIV‐1. These SHIVs should contribute to understanding the pathogenicity of AIDS and to the development of future anti‐HIV‐1 live vaccines for humans.

Construction of chimeric simian and human immunodeficiency viruses that produce interleukin 12

Chimeric simian and human immunodeficiency viruses (SHIVs) are useful for evaluating vaccine candidates against HIV-1 and for investigating the pathogenesis of HIV-1 in vivo. In addition, SHIVs are candidates for a vaccine against HIV-1 because attenuated SHIVs can induce long-lasting anti-HIV-1 Env humoral and cell-mediated immunity in monkeys without AIDS-like diseases. In this study, we inserted IL-12 genes in a nef-deleted SHIV to increase the ability of the SHIV to induce cell-mediated immunity against HIV-1. The SHIV vector was constructed by deleting the nef gene and replacing it with restriction enzyme sites. Since IL-12 consists of two subunit genes, p35 and p40, SHIVs with one or both of these genes were constructed. SHIVs with either one of the subunit genes could replicate without a deletion of the inserted gene, but SHIVs with two subunit genes replicated poorly and the inserted genes were rapidly deleted. Production of IL-12 was detected when both of the single-subunit SHIVs were coinfected. The production of IL-12 by the coinfection reached 800 pg/ml, and IL-12 was detected after serial passage in cell cultures, although this amount of IL-12 heterodimer was 150-1500 times less than that of the p40 subunits. These IL-12-producing SHIVs are candidates for a live-attenuated vaccine to induce effective cellular immunity against HIV-1.

Gene-mutated HIV-1/SIV chimeric viruses as AIDS live attenuated vaccines for potential human use

To develop an AIDS vaccine for human use as well as a suitable animal model for AIDS research, we constructed a series of HIV-1/SIVmac chimeric viruses (SHIVs). We successfully generated a SHIV (designated as NM-3rN) having the HIV-1 env gene, which enabled the evaluation of the efficacy of HIV-1 Env-targeted vaccines in macaque monkeys instead of chimpanzees. Two NM-3rN derivatives (NM-3 and NM-3n) induced long-term anti-virus immunities without manifesting the disease. The monkeys vaccinated with NM-3 or NM-3n became resistant to a challenge inoculation with NM-3rN. Serum from a monkey vaccinated with NM-3 neutralized not only the parental HIV-1 (NL432), but also an antigenically different HIV-1 (MN). In vivo experiments confirmed the heterologous protection against an SHIV having the HIV-1 (MN) env. In addition to specific immunity including neutralizing antibodies and cytotoxic T lymphocyte activity, nonspecific immunity such as natural killer activity is associated with this protection. These data suggest that the live vaccine has the ability to protect individuals against various types of HIVs. These SHIVs should contribute to the development of future anti-HIV-1 live vaccines in humans.