Expression of the pol gene of human endogenous retroviruses HERV-K and -W in leukemia patients.

The human endogenous retroviruses (HERVs) are a family of endogenous retroviruses that integrated into the germ cell DNA of primates over 30 million years ago. HERV expression seems impaired in several diseases, ranging from autoimmune to neoplastic disorders. The purpose of this study was to evaluate the overall endogenous retroviral transcription profile in bone marrow (BM) samples. A total of 30 paediatric high-risk leukaemia patients (lymphoid and myeloid malignancies) were tested for HERVs virus gene expression. Our findings show that HERV-K expression was significantly higher in leukaemia patients when compared to healthy donors of a similar median age. We observed a significantly high expression of HERV-K in acute lymphoblastic leukemia (ALL) patients. In this study, we also found a relative overexpression of the endogenous retrovirus HERV-K in BM cells from the majority of leukemia samples analyzed, in particular in ALL. This overexpression might be related to lymphatic leukemogenesis and it warrants further investigations.

Human endogenous retrovirus (HERV) expression is not induced by treatment with the histone deacetylase (HDAC) inhibitors in cellular models of HIV-1 latency.

BACKGROUND: While antiretroviral therapies have improved life expectancy and reduced viral loads in HIV-1-positive individuals, the cessation of treatment results in a rebound of viral replication. This suggests that a reservoir of latently-infected cells remains within these patients, the identity of which is ill-defined and therefore difficult to target therapeutically. Current strategies are aimed at using drugs such as histone deacetylase (HDAC) inhibitors to induce the expression of latent HIV-1 proviruses in order to activate and ultimately eradicate this reservoir of infected cells. One concern with the use of HDAC inhibitors is that they could up-regulate human endogenous retroviruses (HERVs), as well as HIV-1, with potentially pathophysiological consequences. RESULTS: In this study, we analysed the transcription of HERV genes in HIV-1 latency T cell (J-LAT 8.4) and monocyte (U1) models following treatment with the HDAC inhibitors, vorinostat, panobinostat and romidepsin. We examined the expression of HERV-K (HML-2) env and pol, as well as the co-opted genes HERV-W env (syncytin-1), HERV-FRD env (syncytin-2), in these cell lines. Finally, we investigated HERV expression in primary human T cells. CONCLUSIONS: We show that HDAC inhibitors did not substantially increase the transcription of the analysed HERV env or pol genes, suggesting that histone acetylation is not crucial for controlling HERV expression in these experimental models and in ex vivo primary human T cells. Importantly, this indicates that unwanted HERV expression does not appear to be a barrier to the use of HDAC inhibitors in HIV-1 cure strategies.

Fatal liver failure caused by reactivation of lamivudine-resistant hepatitis B virus: a case report.

We present a case of fetal liver failure caused by the activation of lamivudine-resistant hepatitis B virus (HBV) nine months after lamivudine treatment. A 57-year old man visited our hospital for the treatment of decompensated chronic hepatitis B. Lamivudine was started in December 2001. Subsequently, serum HBV was negative for HBV DNA with seroconversion from HBeAg to anti-HBe and improvement of liver function. However, HBV DNA and HBeAg were again detected in September 2002. He was complicated by breakthrough hepatitis and admitted to our hospital in November for severely impaired liver function. Vidarabine treatment was started and serum HBV DNA and alanine aminotransferase (ALT) decreased transiently. However, after the start of alpha-interferon treatment, HBV DNA level increased and liver function deteriorated. He died 1 mo after admission. An analysis of amino acid sequences in the polymerase region revealed that rtM204I/V with rtL80I/V occurred at the time of viral breakthrough. After the start of antiviral treatment, rtL180M was detected in addition to rtM204I/V and rtL80I/V, and became predominant in the terminal stage of the disease. HBV clone with a high replication capacity may be produced by antiviral treatment leading to the worsening of liver function. Antiviral therapy for patients with breakthrough hepatitis in advanced liver disease should be carefully performed.

A flavonoid from medicinal plants blocks hepatitis B virus-e antigen secretion in HBV-infected hepatocytes.

A flavonoid molecule that showed a unique anti-HBV function was isolated from Phyllanthus urinaria. The molecular formula was determined as C14H6O8 based on FAM-MS analysis and the structure was determined by NMR. The identified flavonoid molecule, ellagic acid, showed unique anti-HBV functions. Ellagic acid did not inhibit either HBV polymerase activity, HBV replication or block HBsAg secretion. Rather, ellagic acid blocks effectively HBeAg secretion in HepG2 2.2.15 cells (IC50=0.07 microg/ml). Since HBeAg is involved in immune tolerance during HBV infection, ellagic acid, a newly identified functional anti-HBV compound, may be a new candidate therapeutic against immune tolerance in HBV-infected individuals.

Association of hepatitis B virus polymerase with promyelocytic leukemia nuclear bodies mediated by the S100 family protein p11.

Hepatitis B virus (HBV) polymerase (Pol) interacts with cellular chaperone proteins and thereby performs multiple functions necessary for viral replication. Yeast two-hybrid analysis was applied to identify additional cellular targets required for HBV Pol function. HBV Pol interacted with S100A10 (p11), a Ca(2+)-modulated protein previously shown to bind to annexin II. The interaction between HBV Pol and p11 was confirmed by co-immunoprecipitation of the two proteins synthesized either in vitro or in transfected cells and by inhibition of the DNA polymerase activity of HBV Pol by p11. Immunofluorescence analysis of transfected human cell lines revealed that, although most HBV Pol and p11 was restricted to the cytoplasm, a small proportion of each protein colocalized as nuclear speckles; HBV Pol was not detected in the nucleus in the absence of p11. The HBV Pol-p11 nuclear speckles coincided with nuclear bodies containing the promyelocytic leukemia protein PML. Furthermore, the association of HBV Pol-p11 with PML was increased by exposure of cells to EGTA and inhibited by valinomycin. These results suggest a role for p11 in modulation of HBV Pol function and implicate PML nuclear bodies and intracellular Ca(2+) in viral replication.

Generation of cytotoxic T cells against virus-infected human brain macrophages in a murine model of HIV-1 encephalitis.

HIV-1 encephalitis (HIVE) and its associated dementia can occur in up to 20% of infected individuals, usually when productive viral replication in brain mononuclear phagocytes (macrophages and microglia) and depletion of CD4(+) T lymphocytes are most significant. T cells control viral replication through much of HIV-1 disease, but how this occurs remains incompletely understood. With this in mind, we studied HIV-1-specific CTL responses in a nonobese diabetic (NOD)-SCID mouse model of HIVE. HIV-1-infected monocyte-derived macrophages (MDM) were injected into the basal ganglia after syngeneic immune reconstitution by HLA-A*0201-positive human PBL to generate a human PBL-NOD-SCID HIVE mouse. Engrafted T lymphocytes produced HIV-1gag- and HIV-1pol-specific CTL against virus-infected brain MDM within 7 days. This was demonstrated by tetramer staining of human PBL in mouse spleens and by IFN-gamma ELISPOT. CD8, granzyme B, HLA-DR, and CD45R0 Ag-reactive T cells and CD79alpha-positive B cells migrated to and were in contact with human MDM in brain areas where infected macrophages were abundant. The numbers of productively infected MDM were markedly reduced (>85%) during 2 wk of observation. The human PBL-NOD-SCID HIVE mouse provides a new tool for studies of cellular immune responses against HIV-1-infected brain mononuclear phagocytes during natural disease and after vaccination.

Frequency and phenotyping of human immunodeficiency virus (HIV)-specific CD8+ T cells in HIV-infected children, using major histocompatibility complex class I peptide tetramers.

HLA-A*02 tetramers complexed to human immunodeficiency virus (HIV) Gag SLYNTVATL and HIV Pol ILKEPVHGV peptides were used to characterize HLA class I-restricted CD8(+) T cells in 41 HIV-infected children. The frequencies and the phenotype of specific circulating CD8(+) T cells were determined in whole-blood samples by means of cytometric analysis. Background staining of 13 HLA-A*02-negative patients showed that the frequency of CD8(+) T cells was <0.01%. Of the 28 HLA-A*02-positive patients, blood samples from 26 stained positive at least once the Gag tetramer (mean CD8(+) T cells, 0.87%; range, 0.1%-3.9%), and blood samples from 21 stained positive for the Pol tetramer (mean CD8(+) T cells, 0.59%; range, 0.1%-5.5%). The tetramer-binding cells were CD28(-), CD45RA(-), CD45RO(+), HLA-DR(+), and CD69(-) T lymphocytes. HIV-specific CD8(+) T cells can be detected easily in peripheral blood of HIV-infected children, using HLA tetramers combined with HIV peptides. These cells are memory activated CD28(-)CD8(+) T lymphocytes.

Organization of HIV-1 pol is critical for Pol polyprotein processing.

The HIV pol sequentially encodes protease (PR), reverse transcriptase (RT), and integrase (IN) from the 5'-3' direction. We explored the significance of this gene arrangement. All six possible gene dispositions were examined. In two situations where PR was removed from the leading place and no two genes were in their original location, viral polyprotein processing was abolished. Processing of the polyprotein did not occur when IN was translocated to the front of PR-RT. However, in the following two arrangements, the polyprotein was processed but only at specific sites. First, PR remained in the leading position while the locations of RT and IN were exchanged; viral polyprotein was processed at a site between the upstream transframe peptide (TF) and PR. Second, PR was placed after RT-IN and located at the distal end of Pol. Processing occurred only at the created junction between TF and RT. These results indicated that cleavage after TF occurred autocatalytically but did not proceed to a second site, which needed an extraneous PR for trans-action. Therefore, arranging Pol in the order of PR-RT-IN warrants the streamline processing of the polyprotein once the autocleavage is initiated.

Determination of the true prevalence of infection with the human T-cell lymphotropic viruses (HTLV-I/II) may require a combination of biomolecular and serological analyses.

Infection with the human T-cell lymphotropic virus types I and II (HTLV-I/II) usually is determined by tests that detect antibodies to the viral structural proteins. However, recent studies revealed that patients with mycosis fungoides have proviral DNA sequences related to the HTLV transactivating-transforming gene tax, without having antibodies to the virus. These results raised the possibility that the prevalence of HTLV infection in the general population of the United States also may be underestimated. To reassess the prevalence of HTLV-I/II infection effectively, a population at increased risk for infection (i.e., a cohort of injection drug users [IDUs]) was studied. Paired sera and peripheral blood mononuclear cells (PBMCs) from 81 IDUs were subjected to testing by Western blot analysis for antibodies to the viral structural proteins gag and env and by polymerase chain reaction (PCR) Southern analysis to detect gag, pol and tax proviral DNA sequences. Western blot assays showed 1 of 81 IDUs to be positive for HTLV-I, 14 to be positive for antibodies to HTLV-II, and 3 to be HTLV-serotype indeterminate. When whole-cell lysates of PBMCs from these individuals were subjected to PCR and Southern analysis. 39 of 81 were found to have HTLV-related sequences. A total of nine IDUs were found to be infected with HTLV-I, a figure nearly 10 times higher than that estimated by serology alone. Bio-molecular analysis showed HTLV-II-specific proviral sequences in 21 IDUs. Three individuals were seropositive for HTLV-II but lacked PCR evidence of gag, pol and tax sequences. Thus, the overall prevalence of HTLV infection among this cohort was 59% (43 of 81) (i.e., more than twice the frequency predicted by serology, 18 of 81 or 22%). These results indicate that it may be necessary to incorporate biomolecular as well as serological methodologies to identify all persons infected with these retroviruses.

Use of the polymerase chain reaction to screen cell banks for retroviruses.

The polymerase chain reaction (PCR) may be used to increase the sensitivity for detecting nucleic acids of specific adventitious agents. PCR can be used in combination with other assays such as infectivity or co-cultivation to increase the sensitivity of detecting adventitious agents or to identify a particular adventitious agent present in the test sample. In addition, PCR is useful for confirming the results of other assays such as reverse transcriptase or electron microscopy. Sources of the test sample, passage history and raw materials added to the test sample are considered when deciding upon the appropriate screening procedures and the adventitious agents for which to screen. In developing a PCR assay, the experiments should be designed to address specificity, sensitivity and reproducibility. Assay development issues include design of primers for the particular retroviruses in question, determination of quantity of sample to test, potential levels of interference, and appropriate positive and negative controls. Validation of a PCR assay is necessary to prove reproducibility for detecting the retrovirus. Data are presented on the qualification of a primate master cell bank to assure the absence of simian immunodeficiency viruses.

Role of the C terminus Gag protein in human immunodeficiency virus type 1 virion assembly and maturation.

Lentiviral Gag polyproteins have a proline-rich protein, p6, at their C terminus. There are conflicting reports about the function of p6 in virus release. In the present work, mutants that affect p6 of human immunodeficiency virus type 1 (HIV-1) Gag polyprotein were constructed and analysed. None of the mutants prevented virus release completely; however, detachment of budding particles was less efficient as evidenced by electron microscopy. Virions of the p6 truncation mutant B2TAA had a significantly reduced number of Pol proteins (p66, p51 and p34) and an increased amount of incompletely processed Gag proteins compared with the parental virus. A mutation that altered the cleavage site between p6 and p1 did not significantly affect virus assembly, virus release or protein processing with the exception of cleavage between p6 and p1. However, virions of this mutant (B2P6C) exhibited irregular-shaped core structures that were distinct from the cone-shaped core structure seen in the parental virion. B2P6C mutant virus was non-infectious in CD4+ T cells. These results suggest that mutations in p6 affect efficient detachment of budding particles from the cell surface. Proper cleavage between p6 and p1 may be critical for the formation of the distinctive cone-shaped core structure of HIV-1 virions.

Establishment of novel lymphoid cell lines dually infected with human T cell lymphotropic viruses types I and II.

With the goal of establishing an in vitro system of dual infection with human T cell lymphotropic viruses (HTLV) types I and II, rabbit lymphocytes were cocultured with a mixture of lethally irradiated HTLV-I-producing Ra-1 and HTLV-II-producing RII cell lines. This gave rise to a lymphoid cell line, RW-1, that was dually infected with HTLV-I and -II as detected by immunofluorescence staining, electron microscopy, and polymerase chain reaction using primers specific for the pol and env regions of each virus and by Southern blot hybridization. Two clonal cell lines derived from RW-1 were also coinfected with the viruses, indicating that dual infection had occurred at the single cell level. The coinfection could be readily propagated to fresh lymphocytes by coculture with RW-1. In contrast, attempts to superinfect HTLV-I-infected lymphoid cell lines with HTLV-II and vice versa were consistently unsuccessful, suggesting receptor interference between HTLV-I and -II.

Detection of antibodies to human immunodeficiency virus type I by using synthetic peptides and time-resolved fluoroimmunoassay (TR-FIA).

A simple, rapid, reproducible and sensitive peptide-Time-Resolved-Fluoroimmunoassay (TR-FIA) method is described which allows the detection of antibodies to the Human Immunodeficiency Virus type 1 (HIV-1). By using a panel of synthetic peptide antigens that covered env, gag and pol amino acid sequences, a 20 amino acid peptide (GIWGCSGKLICTTAVPWNAS) describing an immunodominant and conserved domain on the gp41 region of the BH10 clone was found to be the most reactive in this study. Optimal conditions for antigen concentration, serum dilution and incubation time were established. The peptide-TR-FIA is specific, as assessed by testing HIV-1 positive sera which included samples from AIDS, ARC patients and HIV-positive drug users. The test was used to detect HIV antibodies in 250 well characterized HIV-1 positive sera and 50 normal sera. Peptide-TR-FIA results indicate that the env peptide was highly reactive with HIV-positive sera showing a sensitivity of 100%. None of the 50 control sera showed positive reactivity against the synthetic peptide. Furthermore the peptide-TR-FIA allowed a fine titration of antibodies to defined epitopes of immunodominant HIV structural proteins that usually cannot be achieved by peptide-ELISA assays.

A fluorometric assay for HIV-protease activity using high-performance liquid chromatography.

A rapid sensitive method for the quantification of in vitro HIV-protease activity has been developed on the basis of the endoproteolytic conversion of N-Dns-SQ-NYPIV to N-Dns-SQNY. The use of the N-dansyl group as a fluorescence label was shown to not significantly alter the apparent kinetic parameters for the peptide-enzyme interaction. Using fluorescence detection, the dansylated product and unconverted substrate are detected in a single rapid (3 min) isocratic reverse-phase HPLC separation in quantities as low as 0.2 pmol. The method is highly reproducible and suited to a variety of applications including the analysis of large sample numbers and rigorous enzymological studies.

A simple Escherichia coli system for monitoring HIV protease activity: analysis of two temperature-sensitive protease mutants.

A simple Escherichia coli system has been developed for the detection of human immunodeficiency virus (HIV) protease activity. In this system, the protease sequence is placed downstream of the HIV gag polypeptide in an operon arrangement. Upon expression of the operon, gag serves as the substrate for the protease; the level of protease activity can be determined by measurement of the cleavage product of gag in cell extracts by Western immunoblotting. This system is useful in both detection of protease mutations generated by mutagenesis and in testing substrate specificity of the protease by mutagenesis of the gag sequence. Using this system, we have observed that modification of the N-terminus of HIV protease renders the enzyme temperature sensitive; the temperature sensitivity is made more pronounced by the conserved change of valine to isoleucine at residue eleven.

Chromophoric peptide substrates for the spectrophotometric assay of HIV-1 protease.

Purified HIV-1 protease hydrolyzes H-Ser-Gln-Asn-Leu-Phe(NO2)-Leu-Asp-Gly-NH2 (Peptide 1) and acetyl-Arg-Lys-Ile-Leu-Phe(NO2)-Leu-Asp-Gly-NH2 (Peptide 2) between the (p-nitro)phenylalanyl and leucyl residues. The cleavage of Peptides 1 and 2 resulted in a decrease in uv absorbance at 310 nm. The HIV-1 protease-catalyzed peptidolysis of Peptides 1 and 2 was characterized by a linear time course at substrate turnover of less than 20%. The solubilities of these substrates at pH 5.0 were sufficient to provide initial rate measurements over a concentration range of 0.05-0.5 mM. Steady-state kinetic data and inhibition constants using both spectrophotometric and high performance liquid chromatography (HPLC) analysis of the peptidolysis of these substrates resulted in comparable values.