(1/181) DNA immunization with HIV-1 tat mutated in the trans activation domain induces humoral and cellular immune responses against wild-type Tat.
Intramuscular immunization of mice with plasmids encoding two transdominant negative mutants of the HIV-1 Tat protein (Tat22 and Tat22/37) elicited a humoral response to wild-type Tat that is comparable to that induced by inoculation of wild-type tat DNA or Tat protein. The percentage of the responders and the Ab titers continued to increase after three additional DNA boosts and pretreatment with bupivacaine at the site of inoculation, without a significant difference (p > 0.05) among the three groups of mice immunized with mutant and wild-type tat genes. By utilizing synthetic peptides representing the amino acid sequence of Tat, one major B cell epitope was defined within the cysteine-rich domain of Tat. Anti-Tat IgG Abs directed against this epitope were found in mice immunized with all tat DNA constructs, whereas different Tat epitopes were detected in mice immunized with the Tat protein. Similarly, IgG2a was the predominant isotype in DNA-immunized mice, with both mutants and wild-type tat genes, as compared with protein immunization, which induced mostly IgG1 and IgG3. Sera from most immunized mice neutralized the effect of extracellular Tat in activating HIV-1 replication. A cellular response was also elicited as indicated by the proliferation of splenocytes when stimulated with wild-type Tat. These results indicate that the wild-type Tat Ag is recognized by Abs and T cells induced by DNA immunization with mutated tat genes, suggesting the possible use of these Tat transdominant mutants, lacking viral trans activation activity and capable of blocking wild-type Tat activity, in the development of an anti-HIV-1 vaccine. (+info)
(2/181) Y chromosomal polymorphisms reveal founding lineages in the Finns and the Saami.
Y chromosomal polymorphisms were studied in 502 males from 16 Eurasian ethnic groups including the Finns, Saami (Inari Lake area and Skolt Saami), Karelians, Mari, Mokshas, Erzas, Hungarians (Budapest area and Csangos), Khanty, Mansi, Yakuts, Koryaks, Nivkhs, Mongolians, and Latvians. The samples were analysed for polymorphisms in the Y chromosome specific Alu insertion (YAP) and six microsatellites (DYS19, DYS389-I and II, DYS390, DYS392, DYS393). The populations were also screened for the recently described Tat polymorphism. The incidence of YAP+ type was highest in the Csangos and in other Hungarians (37.5% and 17.5%, respectively). In the Karelians and the Latvians it was present at approximately the same level as commonly found in other European populations, whilst absent in our further samples of Eurasian populations, including the Finns and the Saami. Aside from the Hungarians, the C allele of the Tat polymorphism was common in all the Finno-Ugric speaking populations (from 8.2% to 63.2%), with highest incidence in the Ob-Ugrian Khanty. The C allele was also found in the Latvians (29.4%). The haplotypes found associated with the Tat C allele showed consistently lower density than those associated with the T allele, indicating that the T allele is the original form. The computation of the age of the Tat C suggested that the mutation might be a relatively recent event giving a maximum likelihood estimate of 4440 years (95% confidence interval about 3140-6200 years). The distribution patterns of the 222 haplotypes found varied considerably among the populations. In the Finns a majority of the haplotypes could be assigned to two distinct groups, one of which harboured the C allele of the Tat polymorphism, indicating dichotomous primary source of genetic variation among Finnish males. The presence of a bottleneck or founding effect in the male lineages of some of the populations, namely in the Finns and the Saami, would appear to be one likely interpretation for these findings. (+info)
(3/181) Expression of the human immunodeficiency virus-Tat gene in lymphoid tissues of transgenic mice is associated with B-cell lymphoma.
The human immunodeficiency virus type 1 (HIV-1) Tat gene, a potent transactivator of viral and cellular genes, has been proposed as a key agent in the pathogenesis of acquired immune deficiency syndrome related disorders, including non-Hodgkin's lymphoma. In cultured cells, the HIV-1 Tat protein can induce the expression of the cytokines interleukin-6 (IL-6) and IL-10, which are known to induce proliferation and differentiation of lymphoid cells. Such alterations in cytokine expression, together with a secondary genetic event, are thought to ultimately lead to oncogenic transformation. To address the influence of Tat on lymphoid development in the context of the whole organism, we produced several transgenic mouse lines that express the Tat gene under the control of an actin promoter. We show here that this promoter directs expression to a variety of sites, including spleen, bone marrow, and lymph nodes. Approximately 25% to 30% of the Tat-transgenic population developed enlarged spleens within 1 year after birth. On histological examination, a significant number of spleens from Tat-transgenic mice exhibited malignant lymphoma of B-cell origin. IgG heavy chain rearrangement confirmed the clonal B-cell nature of these lymphoproliferations. In contrast, T-cell receptor genes exhibited a germline (unrearranged) structure. Reverse transcription polymerase chain reaction analysis of transgenic spleens revealed that mRNA encoding cytokines IL-6 and IL-10 was upregulated, suggesting a possible mechanism for the B-cell expansion in vivo. (+info)
(4/181) The Tat protein of human immunodeficiency virus type-1 promotes vascular cell growth and locomotion by engaging the alpha5beta1 and alphavbeta3 integrins and by mobilizing sequestered basic fibroblast growth factor.
The Tat protein of human immunodeficiency virus type-1 (HIV-1) has been shown to be released during acute infection of T cells by HIV-1 and to promote angiogenesis and Kaposi's sarcoma (KS) development in infected individuals. In this study, we investigated the molecular mechanisms responsible for the angiogenic effects of Tat. The results shown herein indicate that two different Tat domains cooperate to induce these effects by different pathways. The arginine-glycine-aspartic acid (RGD) sequence present at the carboxyterminal of Tat mediates vascular cell migration and invasion by binding to the alpha5beta1 and alphavbeta3 integrins. This interaction also provides endothelial cells with the adhesion signal they require to grow in response to mitogens. At the same time, the Tat basic sequence retrieves into a soluble form extracellular basic fibroblast growth factor (bFGF) bound to heparan sulfate proteoglycans by competing for heparin-binding sites. This soluble bFGF mediates Tat-induced vascular cell growth. These effects resemble those of extracellular matrix proteins, suggesting that Tat enhances angiogenesis and promotes KS progression by a molecular mimicry of these molecules. (+info)
(5/181) Susceptibility of HIV-1-TAT transfected cells to undergo apoptosis. Biochemical mechanisms.
The effects of HIV-1 Tat protein on mitochondria membrane permeability and apoptosis were analysed in lymphoid cells. In this report we show that stable-transfected HIV-Tat cells are primed to undergo apoptosis upon serum withdrawal. This effect was observed in both the Jhan T cell line and the K562 cells, the latter expressing the bcr-abl chimeric gene, which confers resistance to apoptosis induced by different stimuli. Using a cytofluorimetric approach we have determined that serum withdrawal induces a disruption of the transmembrane mitochondrial potential (Deltapsim) followed by an increase of reactive oxygen species (ROS) and the subsequent DNA nuclear loss in K562-Tat cells but not in the K562-pcDNA cell line. These pre-apoptotic events were associated with the cleavage of the caspase-3, while the expression of Bcl-2, Bcl-XL and Bax proteins was not affected by the presence of Tat. Regardless of the steady state of the Bax protein, we found that in both K562 and K562-Tat cells, this protein is located in the nucleus, but after serum withdrawal its localization was mainly in the cytoplasm. The activity of caspase-3 detected in K562-Tat cells after serum withdrawal paralleled with the mitochondria permeability transition. Nevertheless, in Jhan-Tat cells the inhibition of this caspase with the specific inhibitor, z-DEVD-cmk, did not affect the disruption of the mitochondria potential induced by serum withdrawal. Interestingly, we found that HIV-Tat protein accumulates at the mitochondria in the K562-Tat cells cultured under low serum conditions, and this mitochondrial localization correlated with the Deltapsim disruption detected in these cells. In addition, HIV-1 Tat protein synergies with protoporphyrin IX (PPIX), a ligand of the mitochondrial benzodiazepine receptor, in the induction of apoptosis in both Jhan and K562 cells. Thus, HIV-1 Tat protein may induce apoptosis by a mechanism that involves mitochondrial PT and may contribute to the lymphocyte depletion seen in AIDS patients. (+info)
(6/181) A second target for the peptoid Tat/transactivation response element inhibitor CGP64222: inhibition of human immunodeficiency virus replication by blocking CXC-chemokine receptor 4-mediated virus entry.
The peptoid CGP64222 has been previously demonstrated to inhibit the human immunodeficiency virus (HIV) Tat/transactivation response element complex formation. It has previously been shown that CGP64222 selectively inhibits HIV-1 long terminal repeat-driven gene expression and HIV-1(LAV) replication in lymphocytes. Here, we show that CGP64222 inhibits the replication of a wide range of laboratory strains of HIV-1 and HIV-2 in MT-4 cells. However, CGP64222 proved inactive in MT-4 cells against HIV-1 strains that are resistant to the bicyclams. The bicyclams are known to specifically interact with CXC-chemokine receptor 4, the main coreceptor used by T-tropic HIV strains to enter the cells. Mechanism of action studies revealed that CGP64222 can inhibit the HIV replicative cycle, also through a selective interaction with the CXC-chemokine receptor 4 coreceptor. (+info)
(7/181) Inhibition of HIV-1 replication in chronically infected cell lines and peripheral blood mononuclear cells by retrovirus-mediated antitat gene transfer.
Among potential genetic targets for intervention in the HIV-1 life cycle, the tat gene product is a key target. We investigated the ability of an antitat gene to inhibit HIV-1 activation and replication in chronically infected promonocyte (U1) and T cell (ACH-2) lines in vitro. U1 and ACH-2 cells were transduced with an antitat gene expressing RNA with dual (polymeric Tat activation response element and antisense-tat) function that interferes with HIV-1 replication. Tumor necrosis factor-alpha (TNF-alpha) plus phorbol 12- myristate 13-acetate (PMA)-induced HIV-1 expression, as determined by reverse transcribed PCR and reverse transcriptase (RT) assays, was significantly inhibited in U1 and ACH-2 cells transduced with the antitat gene, compared with the cells transduced with control vector and untransduced cells. This resistance to TNF-alpha plus PMA-induced HIV-1 expression was demonstrated in antitat gene-transduced U1 and ACH-2 cells maintained in G418-free media for 5 months, suggesting that functional antitat gene may persist for many months in transduced cells and their progeny. Most importantly, we demonstrate that the antitat gene, when introduced into peripheral blood mononuclear cells (PBMC) isolated from patients with HIV-1 infection, inhibited TNF-alpha plus PMA-induced viral replication as determined by RT-PCR and RT activity. In addition, the antitat gene enhanced the survival of CD4+ T lymphocytes from such patients. These data suggest the feasibility of utilizing antitat gene therapy to block activation and replication of HIV-1 in latently infected monocytes and T- lymphocytes in vivo. Gene Therapy (2000) 7, 321-328. (+info)
(8/181) CD8+ T cell-mediated suppressive activity inhibits HIV-1 after virus entry with kinetics indicating effects on virus gene expression.
Individuals infected with HIV-1 have varying rates of progression to AIDS. Cellular immune responses, comprised of cytolytic and noncytolytic CD8(+) T cell effector functions, are considered important for controlling viremia and maintaining the clinically asymptomatic state. Although there is general agreement regarding CD8(+) T lymphocyte cytotoxic functions, considerable controversy exists over the nature of the noncytolytic antiviral activity of CD8(+) cells. The discovery that RANTES (regulated on activation, normal T cell expressed and secreted), MIP-1alpha, and MIP-1beta (macrophage inflammatory protein 1 alpha and beta) could inhibit HIV-1 replication by blocking viral entry processes led to the notion that these molecules are responsible for the CD8(+) cell suppressive activity. However, T tropic HIV isolates requiring the CXCR4 coreceptor for entry are insensitive to the antiviral effects of these beta-chemokines. Using a CXCR4-dependent virus, we determined that the mechanism of CD8(+) T cell-mediated activity did act after viral entry into the host cell. We also define the kinetics of the HIV life cycle in primary activated human CD4(+)-enriched T cells by using an HIV-1 reporter virus system pseudotyped with the CXCR4-dependent HIV-1 envelope gene of NL4-3. Analysis of these kinetic data indicates that CD8(+) T cell-mediated suppressive activity acts at a stage in the viral life cycle after entry and independently of the HIV envelope. Additionally, we show that the antiviral activity targets stages of the virus life cycle correlating with transcription and early proviral gene expression. These findings not only provide a range of possible targets for the CD8(+) T cell-mediated activity but also support the notion that this antiviral activity is multifactorial in nature. (+info)