Therapeutic vaccine-mediated Gag-specific CD8+ T-cell induction under anti-retroviral therapy augments anti-virus efficacy of CD8+ cells in simian immunodeficiency virus-infected macaques.

Anti-retroviral therapy (ART) can inhibit HIV proliferation but not achieve virus eradication from HIV-infected individuals. Under ART-based HIV control, virus-specific CD8+ T-cell responses are often reduced. Here, we investigated the impact of therapeutic vaccination inducing virus-specific CD8+ T-cell responses under ART on viral control in a macaque AIDS model. Twelve rhesus macaques received ART from week 12 to 32 after simian immunodeficiency virus (SIV) infection. Six of them were vaccinated with Sendai virus vectors expressing SIV Gag and Vif at weeks 26 and 32, and Gag/Vif-specific CD8+ T-cell responses were enhanced and became predominant. All macaques controlled viremia during ART but showed viremia rebound after ART cessation. Analysis of in vitro CD8+ cell ability to suppress replication of autologous lymphocytes-derived SIVs found augmentation of anti-SIV efficacy of CD8+ cells after vaccination. In the vaccinated animals, the anti-SIV efficacy of CD8+ cells at week 34 was correlated positively with Gag-specific CD8+ T-cell frequencies and inversely with rebound viral loads at week 34. These results indicate that Gag-specific CD8+ T-cell induction by therapeutic vaccination can augment anti-virus efficacy of CD8+ cells, which may be insufficient for functional cure but contribute to more stable viral control under ART.

Determination of a T cell receptor of potent CD8+ T cells against simian immunodeficiency virus infection in Burmese rhesus macaques.

Cumulative studies on human immunodeficiency virus (HIV)-infected individuals have shown association of major histocompatibility complex class I (MHC-I) polymorphisms with lower viral load and delayed AIDS progression, suggesting that HIV replication can be controlled by potent CD8+ T-cell responses. We have previously established an AIDS model of simian immunodeficiency virus (SIV) infection in Burmese rhesus macaques and found a potent CD8+ T cell targeting the Mamu-A1*065:01-restricted Gag241-249 epitope, which is located in a region corresponding to the HIV Gag240-249 TW10 epitope restricted by a protective MHC-I allele, HLA-B*57. In the present study, we determined a T cell receptor (TCR) of this Gag241-249 epitope-specific CD8+ T cell. cDNA clones encoding TCR-α and TCR-ß chains were obtained from a Gag241-249-specific CD8+ T-cell clone. Coexpression of these TCR-α and TCR-ß cDNAs resulted in reconstitution of a functional TCR specifically detected by Gag241-249 epitope-Mamu-A1*065:01 tetramer. Two of three previously-reported CD8+ T-cell escape mutations reduced binding affinity of Gag241-249 peptide to Mamu-A1*065:01 but the remaining one not. This is consistent with the data obtained by molecular modeling of the epitope-MHC-I complex and TCR. These results would contribute to understanding how viral CD8+ T-cell escape mutations are selected under structural constraint of viral proteins.

Association of lymph-node antigens with lower Gag-specific central-memory and higher Env-specific effector-memory CD8(+) T-cell frequencies in a macaque AIDS model.

Virus-specific CD8(+) T cells exert strong suppressive pressure on human/simian immunodeficiency virus (HIV/SIV) replication. These responses have been intensively examined in peripheral blood mononuclear cells (PBMCs) but not fully analyzed in lymph nodes (LNs), where interaction between CD8(+) T cells and HIV/SIV-infected cells occurs. Here, we investigated target antigen specificity of CD8(+) T cells in LNs in a macaque AIDS model. Analysis of virus antigen-specific CD8(+) T-cell responses in the inguinal LNs obtained from twenty rhesus macaques in the chronic phase of SIV infection showed an inverse correlation between viral loads and frequencies of CD8(+) T cells with CD28(+) CD95(+) central memory phenotype targeting the N-terminal half of SIV core antigen (Gag-N). In contrast, analysis of LNs but not PBMCs revealed a positive correlation between viral loads and frequencies of CD8(+) T cells with CD28(-)CD95(+) effector memory phenotype targeting the N-terminal half of SIV envelope (Env-N), soluble antigen. Indeed, LNs with detectable SIV capsid p27 antigen in the germinal center exhibited significantly lower Gag-N-specific CD28(+) CD95(+) CD8(+) T-cell and higher Env-N-specific CD28(-)CD95(+) CD8(+) T-cell responses than those without detectable p27. These results imply that core and envelope antigen-specific CD8(+) T cells show different patterns of interactions with HIV/SIV-infected cells.

Impact of vaccination on cytotoxic T lymphocyte immunodominance and cooperation against simian immunodeficiency virus replication in rhesus macaques.

Cytotoxic T lymphocyte (CTL) responses play a central role in viral suppression in human immunodeficiency virus (HIV) infections. Prophylactic vaccination resulting in effective CTL responses after viral exposure would contribute to HIV control. It is important to know how CTL memory induction by vaccination affects postexposure CTL responses. We previously showed vaccine-based control of a simian immunodeficiency virus (SIV) challenge in a group of Burmese rhesus macaques sharing a major histocompatibility complex class I haplotype. Gag(206-216) and Gag(241-249) epitope-specific CTL responses were responsible for this control. In the present study, we show the impact of individual epitope-specific CTL induction by prophylactic vaccination on postexposure CTL responses. In the acute phase after SIV challenge, dominant Gag(206-216)-specific CTL responses with delayed, naive-derived Gag(241-249)-specific CTL induction were observed in Gag(206-216) epitope-vaccinated animals with prophylactic induction of single Gag(206-216) epitope-specific CTL memory, and vice versa in Gag(241-249) epitope-vaccinated animals with single Gag(241-249) epitope-specific CTL induction. Animals with Gag(206-216)-specific CTL induction by vaccination selected for a Gag(206-216)-specific CTL escape mutation by week 5 and showed significantly less decline of plasma viral loads from week 3 to week 5 than in Gag(241-249) epitope-vaccinated animals without escape mutations. Our results present evidence indicating significant influence of prophylactic vaccination on postexposure CTL immunodominance and cooperation of vaccine antigen-specific and non-vaccine antigen-specific CTL responses, which affects virus control. These findings provide great insights into antigen design for CTL-inducing AIDS vaccines.

Major histocompatibility complex class I-restricted cytotoxic T lymphocyte responses during primary simian immunodeficiency virus infection in Burmese rhesus macaques.

Major histocompatibility complex class I (MHC-I)-restricted CD8(+) cytotoxic T lymphocyte (CTL) responses are crucial for the control of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) replication. In particular, Gag-specific CTL responses have been shown to exert strong suppressive pressure on HIV/SIV replication. Additionally, association of Vif-specific CTL frequencies with in vitro anti-SIV efficacy has been suggested recently. Host MHC-I genotypes could affect the immunodominance patterns of these potent CTL responses. Here, Gag- and Vif-specific CTL responses during primary SIVmac239 infection were examined in three groups of Burmese rhesus macaques, each group having a different MHC-I haplotype. The first group of four macaques, which possessed the MHC-I haplotype 90-010-Ie, did not show Gag- or Vif-specific CTL responses. However, Nef-specific CTL responses were elicited, suggesting that primary SIV infection does not induce predominant CTL responses specific for Gag/Vif epitopes restricted by 90-010-Ie-derived MHC-I molecules. In contrast, Gag- and Vif-specific CTL responses were induced in the second group of two 89-075-Iw-positive animals and the third group of two 91-010-Is-positive animals. Considering the potential of prophylactic vaccination to affect CTL immunodominance post-viral exposure, these groups of macaques would be useful for evaluation of vaccine antigen-specific CTL efficacy against SIV infection.

Strain-specific differences in the impact of human TRIM5alpha, different TRIM5alpha alleles, and the inhibition of capsid-cyclophilin A interactions on the infectivity of HIV-1.

HIV-1 infectivity is strongly restricted by TRIM5α from certain primate species but has been described as being only marginally susceptible to human TRIM5α. In this study, we evaluated the effects of the modulation of human TRIM5α activity (pretreatment of target cells with alpha interferon, expression of a pre-miRNA targeting TRIM5α, and/or overexpression of TRIM5γ), the inhibition of cyclophilin A (CypA)-CA interactions, and the expression of different allelic variants of human TRIM5α on the infectivity of a series of recombinant viruses carrying different patient-derived Gag-protease sequences. We show that HIV-1 displays virus-specific differences in its sensitivity to human TRIM5α and in its sensitivity to different TRIM5α alleles. The effect of inhibiting CypA-CA interactions is also strain specific, and blocking these interactions can either inhibit or improve viral infectivity, depending on the isolate studied. The inhibition of CypA-CA interactions also modulates viral sensitivity to human TRIM5α. In the absence of CypA-CA interactions, most viruses displayed increased sensitivity to the inhibitory effects of TRIM5α on viral replication, but one isolate showed a paradoxical decrease in sensitivity to TRIM5α. Taken together, these findings support a model in which three interlinked factors--capsid sequence, CypA levels, and TRIM5α--interact to determine capsid stability and therefore viral infectivity.

Involvement of thioredoxin-binding protein 2 in the antitumor activity of CD437.

The present authors previously reported that a synthetic retinoid, CD437, induces endoplasmic reticulum stress-mediated apoptosis in ovarian adenocarcinoma cells in spite of no response to natural retinoids. However, the precise mechanism of its proapoptotic action has not been fully determined. The present study herein demonstrates that apoptosis induction of ovarian adenocarcinoma SKOV3 cells by CD437 involves the upregulation of thioredoxin-binding protein 2 (TBP2) by a mechanism that is dependent on the intracellular calcium concentration. TBP2 is known to bind to and suppress thioredoxin (TRX) activity whereas TRX has an anti-apoptotic effect by inhibiting apoptosis signal-regulating kinase 1 (ASK1). The activation of ASK1 and its downstream molecule, c-Jun N-terminal kinase, was observed after induction of TBP2 by CD437. Interestingly, CD437 induced the association of TBP2 with TRX and, in turn, facilitated the dissociation of ASK1 from TRX. Moreover, blockade of TBP2 induction by small interfering RNA (siRNA) significantly attenuated the cytotoxic effect of CD437. These results suggest that TBP2 plays a critical role in the mechanism by which CD437 exerts proapoptotic action against SKOV3 cells.

Synthetic retinoid CD437 induces mitochondria-mediated apoptosis in hepatocellular carcinoma cells.

Retinoids play an important role in the regulation of cell growth and death. Synthetic retinoid CD437 reportedly induces apoptosis in various cancer cell lines. However, the mechanism of inducing apoptosis in hepatocellular carcinoma (HCC) cells by this agent remains to be clarified. In this study, we investigated the signaling pathway by which CD437 induces apoptosis in HCC cell lines. Apoptosis of six human HCC cell lines was induced by treatment with CD437. Caspase-3 and -9 were activated by CD437, suggesting that the apoptosis is mediated by mitochondrial pathways. Consistent with these findings, the treatment with CD437 upregulated Bax protein, downregulated Bcl-2 protein and released cytochrome c into the cytoplasm. Moreover, rhodamine123 staining revealed mitochondrial depolarization in the cells treated with CD437. These data of the present study suggest that CD437 induces apoptosis in HCC cells via mitochondrial pathways.

CD437 induces apoptosis in ovarian adenocarcinoma cells via ER stress signaling.

A synthetic retinoid, CD437, has been shown to exert potent anti-tumor activity against various types of cancer cell lines, regardless of their sensitivities to natural retinoids. We herein demonstrate that CD437 induces endoplasmic reticulum (ER) stress, including the up-regulation of CHOP, BIP and GADD34 mRNA through ER stress transducer (PERK and IRE1alpha) activation in an ovarian adenocarcinoma cell line, SKOV3. It was also shown that CD437 induced the CHOP and GADD34 expressions in another four ovarian adenocarcinoma cell lines, indicating that CD437 functions as an ER stress inducer in these cell lines. Moreover, the siRNA-mediated knockdown of inducible CHOP expression prevented the cytotoxic effect of CD437. These results suggest that ER stress plays an important role in the mechanism by which CD437 induces apoptosis in ovarian adenocarcinoma cells.

A role of Wnt/beta-catenin signals in hepatic fate specification of human umbilical cord blood-derived mesenchymal stem cells.

Human umbilical cord blood-derived mesenchymal stem cells (UCBMSCs) are expected to be an excellent source of cells for transplantation. In addition, the stem cell plasticity of human UCBMSCs, which can transdifferentiate into hepatocytes, has been reported. However, the mechanisms involved remain to be clarified. To identify the genes and/or signals that are important in specifying the hepatic fate of human UCBMSCs, we analyzed gene expression profiles during the hepatic differentiation of UCBMSCs with human telomerase reverse transcriptase, UCBMSCs immortalized by infection with a retrovirus carrying telomerase reverse transcriptase, but whose differentiation potential remains unchanged. Efficient differentiation was induced by 5-azacytidine (5-aza)/hepatocyte growth factor (HGF)/oncostatin M (OSM)/fibroblast growth factor 2 (FGF2) treatment in terms of function as well as protein expression: 2.5-fold increase in albumin, 4-fold increase in CCAAT enhancer-binding protein alpha, 1.5-fold increase in cytochrome p450 1A1/2, and 8-fold increase in periodic acid-Schiff staining. Consequently, we found that the expression of Wnt/beta-catenin-related genes downregulated, and the translocation of beta-catenin was observed along the cell membrane and in the cytoplasm, although some beta-catenin was still in the nucleus. Downregulation of Wnt/beta-catenin signals in the cells by Fz8-small interference RNA treatment, which was analyzed with a Tcf4 promoter-luciferase assay, resulted in similar hepatic differentiation to that observed with 5-azacytidine/HGF/OSM/FGF2. In addition, the subcellular distribution of beta-catenin was similar to that of cells treated with 5-azacytidine/HGF/OSM/FGF2. In conclusion, the suppression of Wnt/beta-catenin signaling induced the hepatic differentiation of UCBMSCs, suggesting that Wnt/beta-catenin signals play an important role in the hepatic fate specification of human UCBMSCs.