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Biomedical subjects

R C Gallo

Publications and source records attributed to R C Gallo.

At least 145 records · Page 8Linked to original sources
PubMed1994

Block of HIV-1 infection by a combination of antisense tat RNA and TAR decoys: a strategy for control of HIV-1.

The tat gene product (Tat) of HIV-1 is an early regulatory protein necessary for viral gene expression and replication. Tat may also play a role as an extracellular protein in both HIV-1 replication and AIDS-associated disorders such as Kaposi's sarcoma. Thus, Tat represents a good target for gene therapy against AIDS. Here we show that when vectors expressing antisense tat RNA are transiently transfected into CD4+ cells, they block about 70% of HIV-1 replication and inhibit the rescue of Tat-defective HIV-1 proviruses by inhibition of Tat protein expression and consequent lack of transcriptional activation of the HIV-promoter. However, antisense tat vectors cannot block the activity of extracellular Tat protein. Another tat inhibitory construct (poly-Tat-activation response; TAR) previously suggested to inhibit HIV-1 transactivation by sequestering the Tat protein, inhibited the activity of extracellular Tat, but like antisense tat RNA did not completely block viral gene expression and replication. These results suggested that one mode of inhibition is not sufficient to block Tat function. However, when the antisense tat and the poly-TAR constructs were combined HIV-1 gene expression was completely blocked (94-98%), suggesting that a combination of inhibitory genes blocking Tat by sequential steps may be a better approach for AIDS gene therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Loss of a neutralizing epitope by a spontaneous point mutation in the V3 loop of HIV-1 isolated from an infected laboratory worker.

The third hypervariable region, or V3 loop, represents the principal neutralizing domain of the gp120 envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1). Sequential viral isolates from a laboratory worker (LW) accidentally infected with HIV-1IIIB in 1985 were analyzed using type-specific neutralizing monoclonal antibodies directed to the V3 loop. A single amino acid substitution, Ala-->Thr at position 21 in the V3 loop of HIV-1LW isolated in 1987, was shown to determine the loss of the neutralizing epitope recognized by one of the monoclonal antibodies (M77). However, this antibody efficiently recognized linear V3 loop peptides containing either the Ala or Thr residue at position 21, indicating that a local change in conformation was responsible for the epitope loss in the native gp120. Molecular modeling studies, experimentally supported by different amino acid replacements at position 21, indicated that the Ala-->Thr substitution leads to a drastic change in the domain of the V3 loop, which contains the complementary surface for antibody binding. These results provide evidence for the first time that a conformation-dependent epitope within the V3 loop of HIV-1 is involved in the generation of neutralization escape mutants in vivo.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Low levels of deoxynucleotides in peripheral blood lymphocytes: a strategy to inhibit human immunodeficiency virus type 1 replication.

Human immunodeficiency virus type 1 (HIV-1) viral DNA synthesis in quiescent and activated peripheral blood lymphocytes (PBLs) was studied. Incomplete viral DNA (previously demonstrated to be associated with HIV-1 virions) is carried by HIV-1 virions into quiescent and activated PBLs, contributing to the formation of an early viral DNA pool in these cells. The viral DNA is subsequently completed but only extremely slowly and inefficiently in quiescent PBLs compared to that in stimulated PBLs. We find that this correlates with significantly lower levels of dNTP substrates in quiescent compared to activated PBLs. At these low dNTP concentrations, HIV-1 reverse transcriptase acts in a partially distributive manner. Increasing dNTP concentrations from the levels of quiescent PBLs to the levels of activated PBLs increases the processive action of reverse transcriptase, which in turn stimulates rapid and efficient formation of full-length DNA. Furthermore, hydroxyurea treatment of stimulated PBLs decreases the dNTP levels and the DNA synthesis rate to levels comparable to quiescent PBLs. Our data therefore indicate that low levels of dNTP may explain why HIV-1 DNA is synthesized slowly and inefficiently in quiescent PBLs and suggest that pharmacologic induction of low dNTP levels represents a therapeutic approach for inhibition of HIV-1 replication.

Adult↗
PubMed1993

The Tat protein of human immunodeficiency virus type 1, a growth factor for AIDS Kaposi sarcoma and cytokine-activated vascular cells, induces adhesion of the same cell types by using integrin receptors recognizing the RGD amino acid sequence.

Spindle-shaped cells of vascular origin are the probable tumor cells of Kaposi sarcoma (KS). These cells, derived from patients with KS and AIDS, proliferate in response to extracellular Tat protein of human immunodeficiency virus type 1. Normal vascular cells, believed to be the progenitors of AIDS-KS cells, acquire spindle morphology and become responsive to the mitogenic effect of Tat after culture with inflammatory cytokines. Such cytokines are increased in human immunodeficiency virus type 1-infected people, suggesting that immune stimulation (rather than immune deficiency) is a component of AIDS-KS pathogenesis. Here we show that (i) Tat promotes adhesion of AIDS-KS and normal vascular cells; (ii) adhesion of normal vascular cells to Tat is induced by exposure of the cells to the same cytokines; (iii) adhesion is associated with the amino acid sequence RGD of Tat through a specific interaction with the integrin receptors alpha 5 beta 1 and alpha v beta 3, although it is augmented by the basic region; and (iv) the expression of both integrins is increased by the same cytokines that promote these cells to acquire spindle morphology and become responsive to the adhesion and growth effects of Tat. The results also suggest that RGD-recognizing integrins mediate the vascular cell-growth-promoting effect of Tat.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Inhibition of human immunodeficiency virus type 1 replication by regulated expression of a polymeric Tat activation response RNA decoy as a strategy for gene therapy in AIDS.

We are investigating a strategy for somatic gene therapy to treat human immunodeficiency virus type 1 (HIV-1) infection by intracellular expression of an RNA decoy and a ribozyme. The RNA decoy, consisting of polymeric Tat activation response elements (TARs), is designed to compete for Tat binding in an equilibrium with viral TAR RNA, thereby inhibiting viral replication. The expression of polymeric TAR is regulated by the HIV long terminal repeat (LTR) and transcriptional activation is dependent on the presence of HIV Tat. Our initial studies indicated that plasmids expressing up to 50 tandem copies of TAR RNA (50TAR) inhibited tat-mediated gene expression by > 90% in a transient transfection assay. A HIV LTR-driven 50TAR construct was subcloned into a replication-defective retroviral vector to ensure high-efficiency gene transfer into T lymphocytes. In addition, a gag RNA-specific ribozyme gene was introduced into the 50TAR containing retroviral vector to enhance the inhibitory effect of the construct (designated TAR-Rib). A human T-cell line (Molt3) was infected (transduced) with the TAR-Rib recombinant retrovirus and challenged with either HIV-1 or simian immunodeficiency virus (SIV). HIV-1 replication was inhibited by 99% in the TAR-Rib-transduced T cells and was maintained over a 14-month period, suggesting that this antiviral strategy represses the formation of escape mutants. Interestingly, the TAR-Rib also inhibited SIV replication in transduced T cells, which suggests that polymeric TAR is a general inhibitor of primate lentiviruses; therefore, the macaque model could be used for further in vivo testing of this antiviral gene therapy strategy.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Long-term treatment of human immunodeficiency virus-infected cells with antisense oligonucleotide phosphorothioates.

The antiviral activity of antisense oligodeoxynucleotide phosphorothioates complementary to the tat gene, the gag mRNA, and the rev mRNA were studied in a long-term infection model. Three antisense oligonucleotides directed to the splice-acceptor site of the tat gene failed to suppress human immunodeficiency virus type 1 replication at 1 microM concentration in long-term culture. In contrast, two oligodeoxynucleotide phosphorothioates (28-mer) complementary to the gag and the rev mRNAs inhibited viral replication for > 80 days, and the antiviral activity was sequence- and length-dependent. In addition, after pretreatment of cells we could reduce the concentration of the antisense oligodeoxynucleotides by > 10-fold and still maintain the inhibition of viral replication. These results suggest that chemotherapy for human immunodeficiency virus type 1 infection with antisense oligodeoxynucleotide phosphorothioates may be achieved by an initial high-dose treatment followed by a lower maintenance dose.

Antiviral Agents↗
PubMed1993

Infection of natural killer cells by human herpesvirus 6.

Natural killer (NK) cells are a functionally defined subset of non-T, non-B lymphocytes of bone marrow origin, which induce lysis of selected target cells, including neoplastic and virus-infected cells. The NK cell function provides an important mechanism of primary defence against viruses in vivo, as demonstrated by the occurrence of multiple herpesvirus infections in patients congenitally lacking NK cells. Here we show that functionally competent CD3- NK clones can be productively infected by human herpesvirus 6 (HHV-6), a T-lymphotropic DNA virus that may play a role in the acquired immunodeficiency syndrome (AIDS) and in the chronic fatigue syndrome, two disorders associated with a defective NK cell activity. The infection is cytopathic and induces de novo expression of CD4, an antigen not expressed within the NK lineage, thereby predisposing NK cells to infection by human immunodeficiency virus type 1 (HIV-1). These results provide evidence that a herpesvirus can directly target and kill NK cells, a potential strategy to suppress the natural anti-viral immunity of the host.

Adult↗
PubMed1993

Abnormal in vitro proliferation and differentiation of T cell colony-forming cells in patients with tropical spastic paraparesis/human T lymphocyte virus type I (HTLV-I)-associated myeloencephalopathy and healthy HTLV-I carriers.

T cell colonies were generated from the peripheral blood mononuclear cells (PBMC) of 10 patients with tropical spastic paraparesis/human T lymphocyte virus type I (HTLV-I)-associated myeloencephalopathy (TSP/HAM), two healthy HTLV-I carriers, and 17 healthy HTLV-I-seronegative subjects. PBMC were cultured in methylcellulose in the absence of added growth factors (spontaneous T cell colonies), or in the presence of phorbol myristate acetate and interleukin 2 (induced T cell colonies). PBMC T cell colony-forming cells (T-CFC) from all TSP/HAM patients and HTLV-I carriers were able to grow in the absence of added growth factors and/or mitogenic stimulation. Pooled spontaneous and induced colonies were composed of cells bearing CD3+, CD4+, CD8+, and CD1+ antigens. Colonies from normal HTLV-I-seronegative subjects displayed mature cells bearing the CD3+, CD4+, CD8+, and CD1- surface phenotype. In addition, spontaneous and induced T cell colonies expressed HTLV-I antigens in 18-38% of the cells from TSP/HAM patients and HTLV-I carriers. These results demonstrate that HTLV-I infection is associated with an abnormal proliferation and differentiation of T cell progenitors in vitro and that the T-CFC from HTLV-I-seropositive individuals are infected, suggesting that T-CFC abnormalities may play a predominant role in the pathophysiology of HTLV-I.

CD3 Complex↗
PubMed1993

Frequency of adult T-cell leukaemia/lymphoma and HTLV-I in Ibadan, Nigeria.

Sera from a small sample of adult blood donors, healthy school children and patients with lymphoma, leukaemia, non-haematologic cancer, congenital and inflammatory disorders from Ibadan, Nigeria were screened for HTLV-I antibody by an enzyme-linked immunoabsorbent assay and confirmed by investigational Western blot. Seventy-nine of 236 positively screened samples could not be tested for confirmation. Seropositive reactivity was observed in nine of 123 blood donors, and 3 of 46 healthy school children but banding patterns on Western blot were often sparse. Among non-Burkitt's non Hodgkin's lymphoma patients six of 30 were HTLV-I positive including four of four with clinical features of adult T-cell leukaemia (ATL). Other clinical conditions had a frequency of positivity indistinguishable from healthy donors. Western blot patterns ranged from strong with multiple bands, which were uncommon, to those with only p24 and p21 envelope positive which were frequent. Given the relative paucity of clinical ATL and the unusual Western blot patterns the true rate of HTLV-I infection may be lower than estimated. It is possible that a cross-reactive HTLV-I-like virus accounts for this pattern.

Adolescent↗
PubMed1993

The human immunodeficiency virus type 1 (HIV-1) vif protein is located in the cytoplasm of infected cells and its effect on viral replication is equivalent in HIV-2.

The human immunodeficiency virus type 1 (HIV-1) vif gene (viral infectivity gene) plays an important role in viral replication in vitro. We demonstrated that the Vif protein is membrane associated in HIV-1-infected cells and have investigated the role in viral replication of the equivalent gene in HIV-2. We constructed an HIV-2 vif minus mutant and studied its virulence and cellular tropism in vitro. Parallel experiments were also performed with an HIV-1 vif mutant to ascertain whether the two distantly related HIV-2 and HIV-1 genes might exert the same effect on viral replication. The results indicated that both HIV-1 and HIV-2 vif minus cell-free infection was not impaired when the SupT-1 cell line was used. However, differential degrees of impairment in viral replication were observed when other cell lines were used (Molt-3, U-937). Nevertheless, when viral production could not be detected, rescue experiments by coculture with the permissive cell line SupT-1 were generally positive, indicating that the viruses were still present in the inoculated cells. In contrast, when primary human cells (peripheral blood mononuclear cells and purified macrophages) were infected with HIV-1 and HIV-2 vif minus viruses no productive infection was observed and generally no virus was rescued by cocultivation. Thus, like in HIV-1, the vif gene of HIV-2 is crucial for viral infectivity in primary cells and might represent an attractive target for therapy.

Cell Compartmentation↗
PubMed1993

Human immunodeficiency virus (HIV) type 1 strain MN neutralizing antibody in HIV-infected children: correlation with clinical status and prognostic value.

Protective immunity to human immunodeficiency virus (HIV) was examined in 228 serial sera from 58 HIV-infected children before and during antiretroviral therapy. Binding antibodies to putative protective V3 epitopes of HIV-1IIIB and HIV-1MN were investigated by a peptide ELISA, and neutralizing antibodies by inhibition of HIV-1MN cell-free viral infection. No difference in binding of total IgG or IgG subclasses was observed between patients with mild (group A) or advanced disease (group B). However, group A patients were more likely to possess neutralizing antibody titers > or = 225 (P = .040 after adjustment for CD4). This threshold titer also predicted clinical outcome in patients with age-adjusted CD4 count > 10% of normal median. Patients with titers < 225 more frequently encountered major clinical events during follow-up than did patients with titers > or = 225 (P = .0028). Epitopes other than the linear V3 loop contribute to this protective immune response. Identification of these epitopes should assist immune therapy of AIDS and HIV vaccine development.

Adolescent↗
PubMed1993

Release, uptake, and effects of extracellular human immunodeficiency virus type 1 Tat protein on cell growth and viral transactivation.

During acute human immunodeficiency virus type 1 (HIV-1) infection or after transfection of the tat gene, Tat protein is released into the cell culture supernatant. In this extracellular form, Tat stimulates both HIV-1 gene expression and the growth of cells derived from Kaposi's sarcoma (KS) lesions of HIV-1-infected individuals (AIDS-KS cells). Tat protein and its biological activities appear in the cell supernatants at the peak of Tat expression, when the rate of cell death is low (infection) or cell death is undetectable (transfection) and increased levels of cytoplasmic Tat are present. Tat-containing supernatants stimulate maximal AIDS-KS cell growth but only low to moderate levels of HIV-1 gene expression. This is due to the different concentrations of exogenous Tat required for the two effects. The cell growth-promoting effects of Tat peak at between 0.1 and 1 ng of purified recombinant protein per ml in the cell growth medium and do not increase with concentration. In contrast, both the detection of nuclear-localized Tat taken up by cells and the induction of HIV-1 gene expression or replication require higher Tat concentrations (> or = 100 ng/ml), and all increase linearly with increasing amounts of the exogenous protein. These data suggest that Tat can be released by a mechanism(s) other than cell death and that the cell growth-promoting activity and the virus-transactivating effect of extracellular Tat are mediated by different pathways.

Animals↗
PubMed1993

Inhibition of Rev activity and human immunodeficiency virus type 1 replication by antisense oligodeoxynucleotide phosphorothioate analogs directed against the Rev-responsive element.

The interaction between the Rev protein of human immunodeficiency virus type 1 and its highly structured and conserved RNA target, the Rev-responsive element, is required for virus replication. We demonstrate that antisense oligodeoxynucleotide phosphorothioate analogs directed against the Rev-responsive element effectively inhibit Rev activity, as well as human immunodeficiency virus type 1 replication, and are candidates for antiviral therapy.

Base Sequence↗
PubMed1993

Complete nucleotide sequence of a highly divergent human T-cell leukemia (lymphotropic) virus type I (HTLV-I) variant from melanesia: genetic and phylogenetic relationship to HTLV-I strains from other geographical regions.

The high prevalences of antibodies against human T-cell leukemia (lymphotropic) virus type I (HTLV-I) reported for remote populations in Papua New Guinea and the Solomon Islands and for some aboriginal populations in Australia have been verified by virus isolation. Limited genetic analysis of the transmembrane portion (gp21) of the envelope gene of these viruses indicates the existence of highly divergent HTLV-I strains in Melanesia. Here, we report the complete nucleotide sequence of an HTLV-I isolate (designated HTLV-IMEL5) from the Solomon Islands. The overall nucleotide divergence of HTLV-IMEL5 from the prototype HTLV-IATK was approximately 8.5%. The degree of variability in the amino acid sequences of structural genes ranged between 3 and 11% and was higher (8.5 to 25%) for the regulatory (tax and rex) genes and the other genes encoded by the pX region. Since HTLV-IMEL5 was as distantly related to HTLV-II as to the other known HTLV-I strains, it could not have arisen from a reocmbinational event involving HTLV-II but rather might be an example of independent viral evolution in this remote population. These data provide important insights and raise new questions about the origin and global dissemination of HTLV-I.

Amino Acid Sequence↗
PubMed1993

Antisense phosphorothioate oligodeoxynucleotides targeted to the vpr gene inhibit human immunodeficiency virus type 1 replication in primary human macrophages.

The replication of human immunodeficiency viruses (HIV) in human macrophages is influenced by genetic determinants which have been mapped predominantly to the viral envelope. However, in HIV-2, the vpr gene has also been suggested as an important modulator of viral expression in human macrophages. We synthesized five antisense phosphorothioate oligodeoxynucleotides complementary to the vpr mRNA of HIV-1Ba-L, a highly macrophage-tropic viral strain, and measured their effect on HIV-1Ba-L replication in primary human macrophages. All of the oligodeoxynucleotides displayed some level of non-sequence-specific inhibition of viral replication; however, only the antisense one had an additional effect on viral production in primary macrophages. Of the five antisense oligodeoxynucleotides tested, only one did not show any additional effect on viral production, whereas all the others inhibited viral replication to a similar degree (70 to 100%). Variation in the degree of inhibition was observed by using five different donors of human primary macrophages. The phosphorothioate oligonucleotides, targeted to the initiating methionine of the Vpr protein, had an inhibitory effect at both 20 and 10 microM only when the size was increased from 24 to 27 bases. Thus, HIV-1 replication in human macrophages is modulated by the expression of the vpr gene, and it is conceivable that vpr antisense oligodeoxynucleotides could be used in combination with antisense oligodeoxynucleotides against other HIV-1 regulatory genes to better control viral expression in human macrophages.

Amino Acid Sequence↗
PubMed1993

Serological, biological, and molecular characterization of New Zealand white rabbits infected by intraperitoneal inoculation with cell-free human immunodeficiency virus.

The availability of a small laboratory animal model suitable for the evaluation of methods for prevention and treatment of human immunodeficiency virus type 1 infection would be a valuable resource for AIDS research. Here we describe the infection of a strain of domestic rabbits by intraperitoneal inoculation with cell-free human immunodeficiency virus type 1. Evidence of infection includes the presence of an immune response that has persisted for almost 3 years and the detection of an reisolation of infectious virus from peripheral blood mononuclear cells (PBMCs) and other tissues during the first 2 years. Typical viral proteins, DNA and RNA patterns, were observed in rabbit PBMCs and in cells infected by cocultivation with rabbit PBMCs. While a number of possible pathological changes were evaluated in infected rabbits, the presence of changes in lymph node structure similar to those reported in infected humans merits further investigation.

Acquired Immunodeficiency Syndrome↗