Frequent methylation of p16INK4A and p14ARF genes implicated in the evolution of chronic myeloid leukaemia from its chronic to accelerated phase

The frequency and mechanism of p16(INK4A) and p14(ARF) gene alterations were studied in cell samples from 30 patients with Philadelphia (Ph) chromosome-positive chronic myeloid leukaemia (CML), both at diagnosis and at the onset of the accelerated phase (AP) of the disease. No alterations in the p16(INK4A) or p14(ARF) genes were found in any of the chronic phase (CP) samples. DNA sequencing analyses detected p16(INK4A) or p14(ARF) mutations in 17 AP samples. All mutations were heterozygous without loss of the other allele. Aberrant methylation of the p16(INK4A) or p14(ARF) promoters was found in 14 of 30 AP samples. The most common situation was the simultaneous methylation of both promoters. Our data indicate that p16(INK4A) and p14(ARF) are primary targets for inactivation by promoter methylation in the acceleration of CML. Transcriptional silencing of the p16(INK4A) and p14(ARF) genes may be important in the conversion of CML from the CP to the AP.

Vertical transmission of human immunodeficiency virus

Sensitive detection methods, such as DNA PCR and RNA PCR suggest that vertical transmission of human immunodeficiency virus (HIV) occurs at three major time periods; in utero, around the time of birth, and postpartum as a result of breastfeeding (Fig. 1). Detection of proviral DNA in infant's blood at birth suggests that transmission occurred prior to delivery. A working definition for time of infection is that HIV detection by DNA PCR in the first 48 h of life indicates in utero transmission, while peripartum transmission is considered if DNA PCR is negative the first 48 h, but then it is positive 7 or more days later [1]. Generally, in the breastfeeding population, breast milk transmission is thought to occur if virus is not detected by PCR at 3-5 months of life but is detected thereafter within the breastfeeding period [2]. Using these definitions and guidelines, studies has suggested that in developed countries the majority, or two thirds of vertical transmission occur peripartum, and one-third in utero [3-6]. The low rate of breastfeeding transmission is due to the practice of advising known HIV-positive mothers not to feed breast milk. However, since the implementation of antiretroviral treatment in prophylaxis of HIV-positive mothers, some studies have suggested that in utero infection accounts for a larger percentage of vertical transmissions [7]. In developing countries, although the majority of infections occurs also peripartum, a significant percentage, 10-17%, is thought to be due to breastfeeding [2, 8, 9].

Induction of HIV-1 replication in latently infected syncytiotrophoblast cells by contact with placental macrophages: role of interleukin-6 and tumor necrosis factor-alpha

The syncytiotrophoblast (ST) layer of the human placenta has an important role in limiting transplacental viral spread from mother to fetus. Although certain strains of human immunodeficiency virus type 1 (HIV-1) may enter ST cells, the trophoblast does not exhibit permissiveness for HIV-1. The present study tested the possibility that placental macrophages might induce replication of HIV-1 carried in ST cells and, further, that infected ST cells would be capable of transmitting virus into neighboring macrophages. For this purpose, we investigated HIV-1 replication in ST cells grown alone or cocultured with uninfected placental macrophages. The macrophage-tropic Ba-L strain of HIV-1, capable of entering ST cells, was used throughout our studies. We demonstrated that interactions between ST cells and macrophages activated HIV-1 from latency and induced its replication in ST cells. After having become permissive for viral replication, ST cells delivered HIV-1 to the cocultured macrophages, as evidenced by detection of virus-specific antigens in these cells. The stimulatory effect of coculture on HIV-1 gene expression in ST cells was mediated by marked tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) release from macrophages, an effect caused by contact between the different placental cells. Results of this study suggest an interactive role for the ST layer and placental macrophages in the dissemination of HIV-1 among placental tissue. Data reported here may also explain why macrophage-tropic HIV-1 strains are transmitted preferentially during pregnancy.

Pseudotypes of vesicular stomatitis virus-bearing envelope antigens of certain HIV-1 strains permissively infect human syncytiotrophoblasts cultured in vitro: implications for in vivo infection of syncytiotrophoblasts by cell-free HIV-1

Intrauterine infection of the fetus is clearly an important mode of vertical transmission of human immunodeficiency virus type 1 (HIV-1). The syncytiotrophoblast layer of the human placenta must be traversed by HIV-1 in order to reach underlying cells and fetal capillaries. Although HIV-1 has been detected in the syncytiotrophoblast layer in situ, there is conflicting evidence regarding infection of syncytiotrophoblast cells with cell-free virus. The phenotypic mixing between HIV-1 and vesicular stomatitis virus (VSV) has been exploited to assay the susceptibility of human term syncytiotrophoblast cells to penetration by various strains of HIV-1. VSV(HIV-1(IIIB)) and VSV(HIV-1(Ba-L)) pseudotypes were found to enter syncytiotrophoblast cells. In contrast, VSV pseudotyped with envelope glycoproteins of RF, MN, or Ada-M strains of HIV-1 did not infect syncytiotrophoblasts. Plating efficiency of VSV(HIV-1(IIIB)) and VSV(HIV-1(Ba-L)) was 10-fold lower on syncytiotrophoblasts than on T-cells and macrophages, respectively. Incubation of VSV(HIV-1(IIIB)) and VSV(HIV-1(Ba-L)) viruses with appropriate HIV-1 neutralizing sera before infection strongly inhibited entry of pseudotyped VSV into syncytiotrophoblast cells. These findings demonstrated that infection of syncytiotrophoblasts with VSV(HIV-1) pseudotypes was mediated by Env from IIIB and Ba-L strains of HIV-1. Monoclonal antibodies (MAb) to CD4, CXCR4, CCR5, and CCR3 were tested for their ability to block VSV(HIV-1) infection of syncytiotrophoblast cells. Neither the anti-CD4 nor the anti-CXCR4, anti-CCR5, and anti-CCR3 MAb had any inhibitory effect on infection of syncytiotrophoblast cells with VSV(HIV-1) pseudotypes. Results from this study suggest that cell-free HIV-1 can enter syncytiotrophoblasts and the susceptibility of these cells to penetration by the virus is strain dependent. Pseudotype infection merely demonstrates that the first steps in HIV-1 replication are possible in syncytiotrophoblast cells.

HHV-8 ELISA based on a one-step affinity capture of biotinylated K8.1 antigen

The immunogenic envelope antigen gp35-37 of human herpesvirus-8 (HHV-8) is encoded by orfK8.1. An ELISA is described using streptavidin capture of bacterially expressed and biotinylated recombinant K8.1 antigen. The antigen capture strategy provides a simple and reliable method, which does not require high yield production and purification of the recombinant antigen before the serological assay. The specificity and sensitivity of the K8.1 ELISA were validated by gp35-37 envelope antigen Western blot and anti-lytic membrane immunofluorescence assay using lytically induced HHV-8 infected BCBL-1 cells. Under the established ELISA conditions, eight of the 10 Kaposi's sarcoma patients and five of the 180 healthy blood donors had IgG antibodies to K8.1 envelope antigen.

Soluble gC1q-R/p33, a cell protein that binds to the globular "heads" of C1q, effectively inhibits the growth of HIV-1 strains in cell cultures

C1q and the outer envelope protein of HIV, gp120, have several structural and functional similarities. Therefore, it is plausible to assume that proteins that are able to interact with C1q may also interact with isolated gp120 as well as the whole HIV-1 virus. Based on this hypothesis, we studied the potential ability of the recombinant form of the 33-kDa protein, which binds to the globular "heads" of C1q (gC1q-R/p33), to inhibit the growth of different HIV-1 strains in cell cultures. gC1q-R/p33 was found to effectively and dose-dependently inhibit the production of one T-lymphotropic (X4) and one macrophage-tropic (R5) strain in human T cell lines (MT-4 and H9) and human monocyte-derived macrophage cultures, respectively. At a concentration range of 5-25 microg/ml, gC1q-R caused a marked and prolonged suppression of virus production. The extent of inhibition was enhanced when gC1q-R was first incubated with and then removed from the target cell cultures before virus infection, compared to that when the cells were infected with gC1q-R-HIV mixtures. The extent of inhibition was comparable to that of the Leu3a anti-CD4 antibody. Addition of gC1q-R to the cell cultures on day 1 or 2 after infection induced markedly less inhibition of HIV-1 growth than pretreatment of the cells just before or together with the infective HIV strains. In ELISA experiments, gC1q-R did not bind to a solid-phase recombinant gp120 while strong and dose-dependent binding of gC1q-R to solid-phase CD4 was observed. Our present findings indicate that gC1q-R is an effective inhibitor of HIV-1 infection, which prevents viral entry by blocking the interaction between CD4 and gp120. Since gC1q-R is a human protein, it is most probably not antigenic in humans. It would seem logical, therefore, to consider gC1q-R or its fragments involved in the CD4 binding as potential therapeutic agents.

Alterations of P53 and RB genes and the evolution of the accelerated phase of chronic myeloid leukemia

Using the single-strand conformation polymorphism and heteroduplex analyses, the P53 and RB genes were analyzed in cell samples from twenty-eight patients with chronic myeloid leukemia (CML) both at diagnosis and at the onset of accelerated phase (AP) of the disease. No alterations of the P53 or RB genes were found in any of the chronic phase (CP) samples. Structural abnormalities of the P53 gene were observed in ten of twenty-eight AP samples within exons 4, 5, 7 and 9. Of the ten cases of AP disease with altered P53 genes, five patients also suffered from the deletion of the other allele. Alterations of the RB gene could be detected in six AP samples, and aberrant band patterns were found in the analysis of exons 2, 3, 4, 6, 7, 13, 14, 17, 21 and 26. Among the six AP samples with structural abnormalities of the RB gene, two showed the loss of the other allele. It is of note that alterations of both P53 and RB genes were observed in two AP samples. Our data strongly suggest that abnormalities of the P53 and RB genes and acceleration of CML are linked events in some cases of AP.

Mutation of the RB1 gene caused unilateral retinoblastoma in early Age

Fluorescence in situ hybridization (FISH) was applied for the detection of the retinoblastoma tumor-suppressor gene deletion on retinoblastoma tumor cells obtained from the unilateral tumor of a 3-month-old boy. Both retinoblastoma tumor cells and peripheral lymphocytes of the patient showed one hybridization signal per cell at the retinoblastoma-1 locus, indicating that one copy of the gene was deleted. Peripheral blood lymphocytes obtained from the patient's parents had two copies per cell for the gene. Retinoblastoma nuclear phosphoprotein expression could not be detected in the tumor tissue. No copy number alterations were detected with ten different centromeric DNA probes in the tumor cells. The deletion at the RB1 locus detected by FISH suggested that this gene alteration was heritable. The parental peripheral blood lymphocytes did not show the loss of the gene; thus the first deletion may have taken place in either of the parental germ cells. The second somatic mutation of the RB1 gene was probably under the detection limit of FISH. The second allelic alterations were detected by using the polymerase chain reaction for all exons of the retinoblastoma gene.

Alteration of substrate and inhibitor specificity of feline immunodeficiency virus protease

Feline immunodeficiency virus (FIV) protease is structurally very similar to human immunodeficiency virus (HIV) protease but exhibits distinct substrate and inhibitor specificities. We performed mutagenesis of subsite residues of FIV protease in order to define interactions that dictate this specificity. The I37V, N55M, M56I, V59I, and Q99V mutants yielded full activity. The I37V, N55M, V59I, and Q99V mutants showed a significant increase in activity against the HIV-1 reverse transcriptase/integrase and P2/nucleocapsid junction peptides compared with wild-type (wt) FIV protease. The I37V, V59I, and Q99V mutants also showed an increase in activity against two rapidly cleaved peptides selected by cleavage of a phage display library with HIV-1 protease. Mutations at Q54K, I98P, and L101I dramatically reduced activity. Mutants containing a I35D or I57G substitution showed no activity against either FIV or HIV substrates. FIV proteases all failed to cut HIV-1 matrix/capsid, P1/P6, P6/protease, and protease/reverse transcriptase junctions, indicating that none of the substitutions were sufficient to change the specificity completely. The I37V, N55M, M56I, V59I, and Q99V mutants, compared with wt FIV protease, all showed inhibitor specificity more similar to that of HIV-1 protease. The data also suggest that FIV protease prefers a hydrophobic P2/P2' residue like Val over Asn or Glu, which are utilized by HIV-1 protease, and that S2/S2' might play a critical role in distinguishing FIV and HIV-1 protease by specificity. The findings extend our observations regarding the interactions involved in substrate binding and aid in the development of broad-based inhibitors.

Differential patterns of interaction between HIV type 1 and HTLV type I in monocyte-derived macrophages cultured in vitro: implications for in vivo coinfection with HIV type 1 and HTLV type I

The interaction between human immunodeficiency virus type 1 (HIV-1) and human T cell leukemia-lymphoma virus type I (HTLV-I) has generated substantial interest. However, there is disagreement on the in vivo consequences of the double infection. We investigated the interactions between HIV-1 and HTLV-I in monocyte-derived macrophages cultured in vitro. For study, the T cell-tropic strain IIIB and the macrophagetropic strain Ada-M of HIV-1 were used. The HTLV-I was prepared from the supernatants of the virus-producing MT-2 cell line. We found that coinfection of macrophages with T cell-tropic HIV-1 and HTLV-I significantly enhanced HIV-1 replication, whereas double infection of the cells with macrophage-tropic HIV-1 and HTLV-I resulted in marked upregulation of HTLV-I production. Stimulatory interactions between HIV-1 and HTLV-I were mediated by their trans-acting proteins. Results of study on nuclear translocation of proviral DNA showed that the tax gene product of HTLV-I was able to facilitate the nuclear import of the reverse-transcribed HIV-1(IIIB) DNA. In contrast, the HIV-1 Tat protein did not increase the intranuclear trafficking of HTLV-I DNA, which suggests another mechanism for HTLV-I enhancement by the tat gene product. In conclusion, this study provides possible mechanisms whereby coinfection of an individual with HIV-1 and HTLV-I may influence the clinical outcome of double infection.

Placental macrophage contact potentiates the complete replicative cycle of human cytomegalovirus in syncytiotrophoblast cells: role of interleukin-8 and transforming growth factor-beta1

Although syncytiotrophoblast (ST) cells can be infected by human cytomegalovirus (HCMV), in vitro studies have indicated that ST cells do not support the complete viral reproductive cycle, or HCMV replication may occur in less than 3% of ST cells. The present study tested the possibility that placental macrophages might enhance activation of HCMV carried in ST cells and, further, that infected ST cells would be capable of transmitting virus to neighboring macrophages. For this purpose, we studied HCMV replication in ST cells grown alone or cocultured with uninfected placental macrophages. Our results demonstrated that HCMV gene expression in ST cells was markedly upregulated by coculture with macrophages, resulting in release of substantial amounts of infectious virus from HCMV-infected ST cells. After having become permissive for viral replication, ST cells delivered HCMV to the cocultured macrophages, as evidenced by detection of virus-specific antigens in these cells. The stimulatory effect of coculture on HCMV gene expression in ST cells was mediated by marked interleukin-8 (IL-8) and transforming growth factor-beta1 (TGF-beta1) release from macrophages, an effect caused by contact between the different placental cells. Our findings indicate an interactive role for the ST layer and placental macrophages in the dissemination of HCMV among placental tissue. Eventually, these interactions may contribute to the transmission of HCMV from mother to the fetus.

Role of interleukin-8 and transforming growth factor-beta1 in enhancement of human cytomegalovirus replication by human T cell leukemia-lymphoma virus type I in macrophages coinfected with both viruses

Human cytomegalovirus (HCMV) is one of the most frequent opportunistic agents causing severe illness in chronic human T cell leukemia-lymphoma virus type I (HTLV-I) infection. Our previous studies have shown that coinfection of macrophages with HCMV and HTLV-I significantly enhances HCMV replication, resulting in release of infectious HCMV from dually infected cells. We found that double infection of macrophages with HCMV and HTLV-I induced a rapid production of substantial amounts of interleukin-8 (IL-8) and transforming growth factor-beta1 (TGF-beta1). Results of transfection studies demonstrated that the tax gene product of HTLV-I was able to induce secretion of IL-8 and TGF-beta1. In addition to its cytokine-inducing effect, the Tax protein could interact with HCMV synergistically to result in production of much higher levels of IL-8 and TGF-beta1 than expected on the basis of their separate activities. Treatment of dually infected macrophage cultures with neutralizing antibodies to IL-8 and TGF-beta1 led to a nearly 1000-fold decrease in release of infectious HCMV from coinfected cells. Similar results were obtained when anti-IL-8 and anti-TGF-beta1 treatments were combined in macrophage cultures transfected with the tax gene before HCMV infection. Our results suggest that the stimulatory effect of HTLV-I Tax protein on HCMV replication in coinfected macrophages is largely mediated by high levels of IL-8 and TGF-beta1 production.

Changes in oncogene expression implicated in evolution of chronic granulocytic leukemia from its chronic phase to acceleration

Expression of nine oncogenes was investigated in cell samples from fifteen patients with Philadelphia chromosome (Ph)-positive chronic granulocytic leukemia (CGL) both at diagnosis and at the onset of accelerated phase (AP) of the disease. The bcr-abl fusion gene, the H-ras gene and the c-myb gene were universally expressed. In comparison with the chronic phase (CP) of the disease, an increase in the levels of bcr-abl-, c-myb- and H-ras-related transcripts was found in three, two and three AP samples, respectively. Elevation of the bcr-abl-related message was associated with duplication of the Ph chromosome and amplification of the bcr-abl fusion gene in one AP sample. No CP samples were positive for c-myc or c-sis expression. On the contrary, c-myc and c-sis were expressed in three and four AP samples, respectively. The presence of c-myc-related transcript was associated with trisomy 8 with or without amplification of the c-myc oncogene in leukemia cells of two patients with CGL in AP. No changes of oncogene expression were found in four AP samples. However, we observed deletions of chromosome 13 and 17 or i(17q) in three of them, suggesting that tumor suppressor gene alterations may also be responsible for the development of AP of CGL. Our data indicate that heterogeneous alterations in oncogenes and tumor suppressor genes accompany the evolution of CGL-CP to the AP of the disease.