Protective effects of nef-deleted SHIV or that having IFN-gamma against disease induced with a pathogenic virus early after vaccination.

To clarify the involvement of primitive non-specific immune responses in the protective effects of a live, attenuated virus, each two rhesus macaques were intravenously immunized with an attenuated chimeric simian and human immunodeficiency virus (SHIV) in which the nef gene was deleted (SHIV-NI) or a SHIV having human IFN-gamma inserted into the deleted nef region (SHIV IFN-gamma). These immunized monkeys were intravenously challenged with a heterologous pathogenic SHIV (SHIV-C2/1) at four weeks post immunization (wpi). After vaccination, one of each SHIV-NI- or SHIV IFN-gamma-immunized monkeys showed a low level of SIV Gag-specific lymphocyte proliferative response but did not have neutralizing antibodies to both the parental and challenge viruses. After the challenge, the plasma viral RNA loads of the challenge virus were suppressed in all the immunized monkeys and the severe CD4+ T cell loss observed in the unimmunized monkeys was not found. Thus, both SHIV IFN-gamma and SHIV-NI infections could prevent from disease progression by a pathogenic virus early after immunization, suggesting that primitive non-specific immune response elicited by attenuated virus infection, in addition to highly acquired virus-specific immunity, contributes to the protective effect against a pathogenic virus.

The quantity and diversity of infectious viruses in various tissues of SHIV-infected monkeys at the early and AIDS stages.

To detect the major sites of viral replication in immunodeficiency virus-infected individuals, we quantified proviral DNA and infectious viruses using quantitative PCR and a plaque assay, respectively, in various tissues of SHIV(KU-2)-infected monkeys in the early and AIDS stages of infection. Compared the quantity of infectious virus among PBMC and the lymphoid tissues, the mesenteric lymph node had the largest number of infectious viruses at the AIDS stage more than at the early stage of infection. These results suggested that the gastrointestinal tract was a major site of viral replication. In the brain, proviral DNA was detected at the early and AIDS stage of infection, but infectious viruses were detected at only the AIDS stage. Moreover, we analyzed the nucleotide sequences of the env V3 region in infectious virus clones isolated from each plaque. The viruses in the lymphoid tissues of the monkey that developed AIDS diverged from the inoculated virus and had the same three amino acid substitutions. However, the viruses in the brain were almost identical to the inoculated virus, suggesting that the virus entered the brain early after infection and persisted without replication and genetic diversion until the AIDS stage.

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.

Protection of macaques against a SHIV with a homologous HIV-1 Env and a pathogenic SHIV-89.6P with a heterologous Env by vaccination with multiple gene-deleted SHIVs.

To evaluate the potential of SHIVs as anti-HIV-1 live vaccines, we constructed two gene-deleted SHIVs, designated SHIV-drn and SHIV-dxrn. The former lacks vpr/nef and the latter lacks vpx/vpr/nef. Four macaques that had been vaccinated with SHIV-drn were challenged with SHIV-NM-3rN, which has an HIV-1 Env that is the same as that of SHIV-drn. No challenge virus was detected by DNA PCR in, or recovered from, two of the macaques. In the other two, challenge virus was detected once and twice, respectively. Plasma viral loads were much lower than those in unvaccinated controls. Another four macaques were vaccinated with SHIV-dxrn. These macaques showed resistance but less than that of SHIV-drn-vaccinated macaques. When the two SHIV-drn-vaccinated macaques were challenged with pathogenic SHIV-89.6P, which has an HIV-1 Env that is antigenically different from that of SHIV-drn, replication of the challenge virus was restricted, and the usual decrease in the number of CD4(+) cells was prevented. In this protection, it is noteworthy that protection involved not only neutralizing antibodies and killer cell activity, but also other unknown specific and nonspecific immunity elicited by the infection.

Replication capacity of simian immunodeficiency virus in cultured macaque macrophages and dendritic cells is not prerequisite for intravaginal transmission of the virus in macaques.

In order to test the hypothesis that macrophages and dendritic cells (DCs) in mucosal tissue play an important role in heterosexual transmission of human immunodeficiency virus, the replication capacities of two simian immunodeficiency viruses (SIVs) were examined in cultured macrophages and DCs as well as in cultured PBMCs in vitro. The virus strains were a T cell-tropic SIV, SIVmac239, and a T cell- and macrophage-tropic (dual-tropic) SIV, SIVmac239/316E. The infectivities of these viruses to cynomolgus macaques by intravaginal inoculation were also compared. Although both virus strains replicated well in cultured PBMCs, SIVmac239 did not replicate in cultured macrophages, whereas SIVmac239/316E did. Both strains showed little replication in cultured DCs, but a high virus yield could be obtained when SIVmac239/316E-infected DCs were co-cultured with uninfected PBMCs. A mixture of these SIVs was inoculated intravaginally to three monkeys and the virus strain that first appeared through the vaginal mucosa was determined. The virus clones detected first in PBMCs, inguinal lymph nodes and vaginal wash cells (VWCs) after the virus inoculation were of SIVmac239 in all cases, except for one clone of SIVmac239/316E in VWCs of one monkey at one time-point. These results show that the infectivity of the virus in intravaginal transmission did not depend on the cell tropism in vitro of the virus.

Genomic analysis of the viral population in genital secretions early after infection of simian immunodeficiency viruses in macaque monkeys.

To clarify the change in the viral population during passage from the vaginal cavity to blood circulation and vice versa, we examined the viral clones detected in cells in vaginal washes (VWCs) early after inoculation and after systemic infection with polyclonal SIV. In two intravaginally inoculated monkeys, the viral clones found in VWCs at 18 days p.i. were shown to be some of those contained in the inoculum, whereas the viral population in the peripheral blood mononuclear cells (PBMCs) was a monotype. This gradual decrease of viral clones suggested the possible existence of two barriers, one at the genital tract and the other between the genital tract and the blood. Later, at one month p.i., the viral clones in VWCs became rather restricted, whereas those in PBMCs diverged from a single clone to several clones. This suggested that different mechanisms affect the viral populations in PBMCs and VWCs. In order to examine how the viral population was affected by passage from the blood to the vaginal cavity, a monkey was intravenously inoculated and the viral clones in VWCs were analyzed at 14 days p.i., at a time of the heterogeneous population in PBMCs. The viral population in VWCs was found to be a single clone and this clone was a minor type in PBMCs, suggesting that the major clone in PBMCs was not always secreted to the vaginal cavity.

Rapid and progressive CD4+ decline in a monkey infected with an SIV+HIV-1 chimeric virus.

We previously constructed a simian immunodeficiency virus+human immunodeficiency virus type 1 (HIV-1) chimeric virus, NM-3rN to generate a pathogenic HIV-1 in macaque monkeys. During the in vivo passage of this virus in several monkeys, a viral strain, R43-56 was obtained which acquired a better replication ability in vivo. MM121, one of the three monkeys inoculated with the R43-56, showed weight loss, diarrhea and a rapid and continuous decrease in CD4+ lymphocytes at the moribund stage. An autopsy revealed generalized lymphadenopathy, dehydration, and ileocecal intussusception. In situ hybridization showed that the virus infection was in systemic lymphoid organs. We are presently monitoring the survivors to obtain candidates for a more virulent virus. R43-56 may be a better challenge virus and useful tool for human acquired immunodeficiency syndrome research.

Restriction of viral population by intravaginal infection of simian immunodeficiency viruses in macaque monkeys.

In order to examine whether the viral population is affected by intramucosal transmission, we analyzed the viral genotypes first detected in peripheral blood mononuclear cells (PBMCs) after intravaginal inoculation, before virus antibodies were detectable, and compared them with those in the inoculum. Three female cynomolgus macaques were inoculated intravaginally and a fourth was inoculated intravenously with polyclonal simian immunodeficiency viruses (SIVmac32H). The provirus genomes which first appeared in PBMC were sequenced in the V1 to V2 region of the SIV envelope gene. A comparison of the sequences obtained from each monkey revealed a homogeneous or heterogeneous viral population depending on the infection route. In the intravenously inoculated monkey, the viral population was heterogenous and was similar to that in the virus inoculum. On the other hand, in the intravaginally inoculated monkeys, single genotypes (in two monkeys) and one genotype with a slight variation (in one monkey) were found, but they were different from each other, having no characteristic sequences in the V1 to V2 region in common. None of the genotypes found in the PBMC were major genotypes in the virus inoculum. These results suggest that some selective mechanism, which differs among individuals, restricts the viral population during mucosal transmission.

Infection of an HIV-1/SIVmac chimeric virus having HIV-1 env to macaque monkeys via the vaginal cavity.

We previously reported that an HIV-1/SIVmac chimeric virus (designated as NM-3rN) having HIV-1 env efficiently infected macaque monkeys by intravenous inoculation. In this study, this chimeric virus was atraumatically inoculated into the vaginal cavity of two rhesus and one cynomolgus monkeys. Although antibody response and detection of proviral genome by PCR were observed in both rhesus monkeys, virus recovery was only once from PBMC in one of them. In the cynomolgus monkey, no virus was recovered and proviral DNA detection was rare. Thus, vaginal inoculation with NM-3rN resulted in poor systemic infection, implying the presence of selective pressure while passing through mucosal membranes.

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 SIVmax 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 0.5 beta and mu 5.5, 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.

Replication and cytopathogenicity of human immunodeficiency virus type 1 (HIV-1)/simian immunodeficiency virus agm3 chimeric viruses in human and monkey cells: the 5' half of the HIV-1 genome is responsible for virus cytopathogenicity.

Two chimeric viruses were constructed between human immunodeficiency virus type 1 (HIV-1) and an apathogenic simian immunodeficiency virus (SIVagm3mc) from African green monkeys. One of the chimeras, HE-A391, expressed the HIV-1-derived env, vpu, tat and rev genes and the SIVagm3mc-derived LTR and the gag, pol and vif genes. The other chimera, SE-H13, contained the SIVagm3mc-derived env, tat and rev genes and the HIV-1-derived LTR and the gag, pol, vif and nef genes. Both constructs yielded infectious viruses and their phenotypes (growth-competence and cell-killing capacity) were examined in various CD4+ cells including human and monkey PBMCs. The results indicated that the replicative properties of the chimeras were mainly dependent on the 5'-genomic half of the parental viruses, and the determinant for viral cytopathogenicity was located within the 5' half of the HIV-1 genome.

Light and electron microscopic localization of lipids in Blastocystis hominis.

Localization of the lipid of Blastocystis hominis was histochemically demonstrated. B. hominis was fixed with glutaraldehyde, treated with detergents, and stained with Sudan black B or Nile blue. The central vacuole of B. hominis stained with Sudan black B showed many black droplets with great variation in staining intensity. In Nile blue staining, the central vacuole showed many pinkish granules or homogeneous blue reactions. These results indicated the presence of neutral lipids and/or acidic lipids in the central vacuole. At the ultrastructural level, the central vacuole and some cytoplasmic vesicles showed enhanced electron density after post-fixation with imidazole-buffered osmium tetroxide solution. Great variation in the density and distribution of the electron-dense materials was observed in the central vacuole. Since the electron-dense vesicles were frequently observed in the cytoplasm, B. hominis may accumulate the lipid in the central vacuole, the function of which is not well known.

Histochemical detection of carbohydrates of Blastocystis hominis.

The carbohydrates of Blastocystis hominis were detected by histochemical techniques using light and electron microscopy. B. hominis, fixed with various fixatives, followed by treatment with detergents, were stained with periodic acid-Schiff (PAS) or alcian blue (AB). Intense PAS reactions were observed in cells fixed with glutaraldehyde or 1/2 Karnovsky fixative. The cells fixed with other fixatives showed weak or no reactions with PAS staining. Similar results were seen in the case of AB stain. These results indicated that, depending on the fixative used, B. hominis contained PAS- or AB-reactive carbohydrates. At the electron microscopic level, ultrathin sections of B. hominis were stained with periodic acid methenamine silver (PA-MS) or periodic acid thiocarbohydrazide-silver proteinate (PA-TCH-SP) staining techniques. Intense, positive reactions with PA-MS or PA-TCH-SP were observed on the central vacuole, Golgi apparatus, and cytoplasmic vesicles. The filamentous layer showed moderate reactions with PA-MS, whereas in PA-TCH-SP stain, it was stained more densely. The staining intensity of the central vacuole varied from cell to cell. The presence of membrane fusions of the cytoplasmic vesicles with the central vacuole indicated the accumulation of carbohydrates in the central vacuole.