Enhanced replication of M-tropic HIV-1 strains in Herpesvirus saimiri immortalised T-cells which express CCR5

Enhanced replication of R5 HIV-1 isolates in vitro by a small-molecule reagent targeting HIV-1 protease

CHEMICAL ENHANCEMENT: Designed to target HIV-1 protease, a novel γ-hydroxyphosphonate has been found to significantly enhance viral replication in a panel of clinically relevant R5 HIV-1 isolates. This unexpected result constitutes the first instance of a small molecule capable of doing this, and it has implications for the preparation and use of R5 isolates in vaccine and drug development.

Inhibition of HIV-1 replication by long-term treatment with a chimeric RNA containing shRNA and TAR decoy RNA

Combinatorial therapies for the treatment of HIV-1 infection are effective for reducing patient viral loads and slowing the progression to AIDS. Our strategy was based on an anti-HIV-1 shRNA vector system in which HIV-1 vif-shRNA was fused to a decoy TAR RNA (mini-TAR RNA) to generate vif-shRNA-decoy TAR RNA under the control of the human U6 Pol III promoter. Upon expression in human cells, the RNA molecule was cleaved into its component parts, which inhibited HIV-1 replication in a synergistic manner. This chimeric RNA expressed a dual RNA moiety and greatly enhanced the inhibition of HIV-1 replication under the production of resistant virus by short interference RNA (siRNA) in long-term culture assays. We suggest that this technique provides a practical basis for the application of siRNA-based gene therapy in the treatment of HIV/AIDS.

Sulfated beta-glucan derived from oat bran with potent anti-HIV activity

China is a major producer of oats; the annual harvested area of 350,000 ha yields approximately 465,000 tons, giving an average yield of 1.33 tons/ha. The bran is not used for animal feed as it is of poor digestibility and low nutritive content and is considered a waste byproduct. Therefore, it is advantageous to produce a value-added product from the bran. We extracted the native polysaccharide, a linear (1-3)-, (1-4)-linked beta-glucan (OBG) from the oat bran and synthesized a sulfated derivative OBGS containing 36.5% sulfate. OBGS had potent activity against a primary isolate of human immunodeficiency virus (HIV-1) in peripheral blood mononuclear cells at a concentration (EC(50)=5.98 x 10(-4) microM) approximately 15,000 times below its cytotoxic concentration. OBGS was also active postinfection (EC(50)=5.3 x 10(-4) microM) and protected pretreated peripheral mononuclear cells (EC(50)=5.2 x 10(-2) microM) washed free of the compounds prior to infection. Thus, OBGS has potential as a vaginal microbicide and is the first such report for oat bran derived sulfated beta-glucan.

Structural features and anti-HIV-1 activity of novel polysaccharides from red algae Grateloupia longifolia and Grateloupia filicina

Since sulphated polysaccharides have antiviral activity in vitro, we examined the structure and antiretroviral activity of native sulphated galactans extracted from the red algae, Grateloupia filicina (GFP) and Grateloupia longifolia (GLP). The sulphate contents of GFP and GLPE (the 1,4-alpha-d-glucan-glucanohydrolase digest of GLP) were 25.7 and 18.5%, respectively. The sulphate ester groups were located at carbon 2 for GFP and at carbon 2 and 6 for GLPE. Antiretroviral activity was investigated with a primary isolate (PI) of HIV-1 and human peripheral blood mononuclear cells (PBMCs) rather than T-cell line adapted (TCLA) HIV-1 and T-cell lines because it is more representative of the in vivo situation. Both compounds and their derivatives had potent anti-HIV-1 activity when added at the time of infection, and 2h post-infection (EC50s 0.010-0.003microM, EC(90s) 0.87-0.33microM) and low cytotoxicity. Their potential medical application as virucidal vaginal formulations is discussed.

Cell transformation by Herpesvirus saimiri

Herpesvirus saimiri (Saimiriine herpesvirus-2), a gamma2-herpesvirus (rhadinovirus) of non-human primates, causes T-lymphoproliferative diseases in susceptible organisms and transforms human and non-human T lymphocytes to continuous growth in vitro in the absence of stimulation. T cells transformed by H. saimiri retain many characteristics of intact T lymphocytes, such as the sensitivity to interleukin-2 and the ability to recognize the corresponding antigens. As a result, H. saimiri is widely used in immunobiology for immortalization of various difficult-to-obtain and/or -to-maintain T cells in order to obtain useful experimental models. In particular, H. saimiri-transformed human T cells are highly susceptible to infection with HIV-1 and -2. This makes them a convenient tool for propagation of poorly replicating strains of HIV, including primary clinical isolates. Therefore, the mechanisms mediating transformation of T cells by H. saimiri are of considerable interest. A single transformation-associated protein, StpA or StpB, mediates cell transformation by H. saimiri strains of group A or B, respectively. Strains of group C, which exhibit the highest oncogenic potential, have two proteins involved in transformation-StpC and Tip. Both proteins have been shown to dramatically affect signal transduction pathways leading to the activation of crucial transcription factors. This review is focused on the biological effects and molecular mechanisms of action of proteins involved in H. saimiri-dependent transformation.

Homeostatic role of IL-7 in HIV-1 infected children on HAART: association with immunological and virological parameters

AIM

To investigate the role of IL-7 in HIV-infected children on highly active antiretroviral therapy (HAART) and its association with laboratory parameters related to disease progression.

PATIENTS AND METHODS

A cross-sectional study in 31 vertically HIV-infected children (median age 8.4 y) treated with HAART, and a longitudinal study in four of those same children was carried out. In both studies, viral load, CD4+ T-cell counts, thymic production of T cells by TCR rearrangement excision circles (TRECs), IL-7 plasma levels and viral phenotype were determined.

RESULTS

IL-7 levels were higher in HIV-infected children than in age-matched, uninfected controls. In addition, HIV children with CD4+ T cells between 200 and 500 T cells/mm3 had higher IL-7 levels and lower TREC values than HIV-infected children with CD4+ T cells >500 T cells/mm3. IL-7 levels were higher in children with syncytium-inducing (SI) phenotype than in those with non-syncytium-inducing (NSI) variants. During the follow-up of four HIV children, the decrease in viral load after HAART was always associated with a recovery of CD4+ T cells and TRECs, which was followed by a decrease in IL-7 returning to the levels present prior to the drop in CD4+ T cells. The four HIV-infected children had SI/X4 isolates in PBMC before HAART, and the viral phenotype switched to NSI/R5 after HAART.

CONCLUSION

Our data suggest that IL-7 plays a key role in the maintenance of T-cell homeostasis in HIV-infected children on HAART, both through peripheral expansion and through a thymus-dependent mechanism.

Herpesvirus saimiri-encoded proteins Tip and StpC modulate human immunodeficiency virus type 1 replication in T-cell lines and lymphocytes independently of viral tropism

Herpesvirus saimiri (HVS)-transformed T-lymphocytes are permissive for both X4 and R5 strains of human immunodeficiency virus type 1 (HIV-1). HVS-encoded proteins tyrosine-kinase interacting protein (Tip) and saimiri transformation-associated protein subgroup C (StpC) were previously implicated in altering HIV permissiveness. MOLT4 cells expressing StpC or StpC and Tip are permissive for X4 strains of HIV-1. In contrast, HIV-1 was restricted in MOLT4 cells expressing Tip alone. Here we show that MOLT4 cells and primary lymphocytes expressing StpC are permissive for R5 strains of HIV-1 while Tip expression restricted R5 strains. These results suggest that intracellular immunization with Tip and StpC could be developed as models for therapeutic strategies targeting both X4 and R5 strains of HIV-1.

Tip, an Lck-interacting protein of Herpesvirus saimiri, causes Fas- and Lck-dependent apoptosis of T lymphocytes

Saimiriine herpesvirus-2 (Herpesvirus saimiri) transforms T lymphocytes, including human, to continuous growth in vitro. H. saimiri-induced transformation is becoming an important tool of T-cell biology, including studies of HIV replication. Two proteins of H. saimiri subgroup C, Tip and StpC, are essential for T-cell transformation. In spite of the important role of these proteins, their biological functions and the molecular mechanisms of their action remain insufficiently understood. To further elucidate the effects of Tip on T cells, we transduced T lymphocytes, using an efficient lentiviral gene transfer system, to express Tip in the absence of other H. saimiri proteins. Our results indicate that Tip specifically inhibits IL-2 production by human T lymphocytes. Furthermore, Tip promotes T-cell apoptosis, which appears to be the reason for the observed decrease in IL-2 production. Finally, the apoptotic effect of Tip in T cells is mediated by Fas and requires the presence of active Lck in the cell.

Efficient lentiviral transduction of Herpesvirus saimiri immortalized T cells as a model for gene therapy in primary immunodeficiencies

Infection of human T lymphocytes with the Herpesvirus saimiri (HVS) yields immortalized T-cell lines (HVS-T) which retain all the phenotypical and functional characteristics of their parental cells. This represents a new experimental model for studying genetic disorders of T lymphocytes. In spite of the efforts of many laboratories, no satisfactory way has been found so far to modify HVS-T cells genetically. We have analyzed the capacity of oncoretroviral (MLV)- and lentiviral (HIV-1)-based vectors pseudotyped with vesicular stomatitis virus glycoprotein (VSVg) to transduce HVS-T cells. HIV-1-derived vectors efficiently transduced HVS-T cell lines, reaching up to 85% of cells expressing the transgene in a single round of infection. MLV-based vectors, on the other hand, were unable to transduce more than 1% of any of the HVS-T cell lines analyzed. Lentiviral-driven gene expression was maintained constant and stable in HVS-T cells for a minimum of 48 days. We also observed that although the lentiviral transduction efficiency achieved on HVS-T cells is lower than that obtained with tumor or primary endothelial cells, it is nevertheless similar to that found with activated primary T cells.

Herpesvirus saimiri-immortalized human lymphocytes: novel hosts for analyzing HIV type 1 in vitro neutralization

Herpesvirus saimiri-immortalized CD4(+) T lymphocytes (HVS T cells) are activated memory cells that support efficient replication of primary R5 strains of HIV-1, which predominate in virus transmission. Being continuous, they are phenotypically more stable and technically less demanding than peripheral blood mononuclear cells (PBMCs). Here we present the first report using HVS T cells to assay HIV-1 neutralization in vitro. Neutralization sensitivities of paired viruses isolated from individuals in both HVS T cells (CN-2 cells) and PBMCs were similar, with homologous and heterologous plasma/sera in both CN-2- and PBMC-based assays. Analysis of V3 loop and CD4-binding site (CD4-BS) sequences showed that changes present in CN-2 isolates were neither more numerous nor more significant than those selected in their PBMC counterparts. Neutralization profiles of CN-2/PBMC virus pairs were similar again when V3- and CD4-binding site (BS)-specific monoclonal antibodies, whose mapped epitopes were conserved or of similar sequence in the virus pairs, were tested. Unlike other T cell line isolates, CN-2 isolates were not more sensitive to neutralization than their PBMC counterparts. We also show that HVS T cells do not appear to exert significant biological selection pressures on primary isolates. Paired viruses have a similar phenotype with respect to syncytium formation, cell tropism, and coreceptor usage. Thus CN-2 cells are suitable hosts for assaying neutralization and could be useful in standardizing neutralization assays performed in different laboratories.

Selection following isolation of human immunodeficiency virus type 1 in peripheral blood mononuclear cells and herpesvirus saimiri-transformed T cells is comparable

In attempts to improve isolation rates and virus yields for human immunodeficiency virus (HIV), the use of herpesvirus saimiri-immortalized T cells (HVS T cells) has been investigated as an alternative to/improvement over peripheral blood mononuclear cells (PBMCs). Here we characterize isolates rescued, in the two cell types, from two asymptomatic, long-term non-progressing HIV-1-infected individuals. All rescued viruses replicated in PBMCs and HVS T cells only, displaying a non-syncytium inducing (NSI) phenotype, and using CCR5 as co-receptor. Furthermore, PBMC/HVS T cell virus pairs displayed similar neutralization profiles. Full-length, expression-competent env genes were rescued from all virus isolates and directly from the patient samples using proviral DNA and viral RNA as templates. Compared with the sequences retrieved directly from the patient samples, both cell types showed similar selection characteristics. Whilst the selections were distinct for individual patient samples, they shared a common characteristic in selecting for viruses with increased negative charge across the V2 domain of the viral glycoproteins. The latter was observed at the env gene sequencing level for three other patients whose HIV strains were isolated in PBMCs only. This further supports a common selection for viral sequences that display a macrophage-tropic/NSI phenotype and shows that HVS T cells are a viable alternative to PBMCs for HIV-1 isolation.

Herpesvirus saimiri

Herpesvirus saimiri (saimiriine herpesvirus 2) is the classical prototype of the gamma(2)-herpesviruses or rhadinoviruses, which also contains a human member, the Kaposi's sarcoma-associated herpesvirus. The T-lymphotropic Herpesvirus saimiri establishes specific replicative and persistent conditions in different primate host species. Virtually all squirrel monkeys (Saimiri sciureus) are persistently infected with this virus. In its natural host, the virus does not cause disease, whereas it induces fatal acute T-cell lymphoma in other monkey species after experimental infection. The virus can be isolated by cocultivation of permissive epithelial cells with peripheral blood cells from naturally infected squirrel monkeys and from susceptible New World monkeys during the virus-induced disease. Tumour-derived and in vitro-transformed T-cell lines from New World monkeys release virus particles. Herpesvirus ateles is a closely related virus of spider monkeys (Ateles spp.) and has similar pathogenic properties to Herpesvirus saimiri in other New World primate species. Similar to other rhadinoviruses, the genome of Herpesvirus saimiri harbours a series of virus genes with pronounced homology to cellular counterparts including a D-type cyclin, a G-protein-coupled receptor, an interleukin-17, a superantigen homologue, and several inhibitors of the complement cascade and of different apoptosis pathways. Preserved function has been demonstrated for most of the homologues of cellular proteins. These viral functions are mostly dispensable for the transforming and pathogenic capability of the virus. However, they are considered relevant for the apathogenic persistence of Herpesvirus saimiri in its natural host. A terminal region of the non-repetitive coding part of the virus genome is essential for pathogenicity and T-cell transformation. Based on the pathogenic phenotypes and the different alleles of this variable region, the virus strains have been assigned to three subgroups, termed A, B and C. In the highly oncogenic subgroup C strains, the two virus genes stpC and tip are transcribed from one bicistronic mRNA and are essential for transformation and leukaemia induction. stpC fulfils the typical criteria of an oncogene; its product interacts with Ras and tumour necrosis factor-associated factors and induces mitogen-activated protein kinase and nuclear factor kappa B activation. Tip interacts with the RNA transport factor Tap, with signal transduction and activation of transcription factors, and with the T-cellular tyrosine kinase Lck, which is activated by this interaction and phosphorylates Tip as a substrate. It is of particular interest that certain subgroup C virus strains such as C488 are capable of transforming human T lymphocytes to stable growth in culture. The transformed human T cells harbour multiple copies of the viral genome in the form of stable, non-integrated episomes. The cells express only a few virus genes and do not produce virus particles. The transformed cells maintain the antigen specificity and many other essential functions of their parental T-cell clones. Based on the preserved functional phenotype of the transformed T cells, Herpesvirus saimiri provides useful tools for T-cell immunology, for gene transfer and possibly also for experimental adoptive immunotherapy.

Altered replication of human immunodeficiency virus type 1 (HIV-1) in T cell lines retrovirally transduced to express Herpesvirus saimiri proteins StpC and/or Tip

Human peripheral blood T lymphocytes are transformed in vitro to continuous proliferation by Herpesvirus saimiri subgroup C strains. It has been previously shown that H. saimiri-transformed human T cell lines are a permissive system for HIV-1 and 2 replication and are highly susceptible to infection by HIV-1 and 2. Two open reading frames of H. saimiri, StpC and Tip, are required for T cell transformation and are unique to this herpesvirus. The successful transduction of human T cells with retroviral vectors expressing H. saimiri proteins StpC and Tip has allowed us to extend the previously mentioned observations and investigate the role of StpC and Tip in replication of HIV-1 T-tropic strains (IIIB, MN, and RF) in human T cell lines. StpC expression in Molt4 dramatically enhanced HIV-1 replication as measured by Tat protein expression, syncytia formation, and accumulation of reverse transcriptase activity. In contrast, Tip expression in Molt4 cells inhibited HIV-1 replication and cytopathic effects relative to Molt4 cells transduced with the empty vector alone. The StpC-induced phenotype dominated in Molt4 cells transduced to express both StpC and Tip, suggesting that StpC is responsible for facilitating HIV-1 replication in H. saimiri-transformed T cells. Colony-forming ability of Tip-expressing Molt4 cells following HIV-1 infection was greatly enhanced over Molt4 cells expressing either StpC or no H. saimiri proteins at all. HIV-1 proviral DNA could be detected by PCR in surviving Molt4 cells expressing StpC or Tip, indicating that a persistent infection was established. A better understanding of the effects of Tip and StpC proteins on the biology of human hemopoietic stem cells may lead to novel therapeutic interventions for the treatment of AIDS.