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S K Arya

Publications and source records attributed to S K Arya.

At least 37 records · Page 2Linked to original sources
PubMed1990

Molecular characterization of an attenuated human immunodeficiency virus type 2 isolate.

Naturally occurring strains of human immunodeficiency virus (HIV) can vary considerably in their in vitro biological properties, and such differences may also be reflected in their in vivo pathogenesis. In an attempt to define genetic determinants of viral pathogenicity, we have molecularly cloned, sequenced, and characterized an attenuated isolate of HIV type 2 (HIV-2/ST) that differs from prototype HIV-2 strains in its inability to fuse with and kill susceptible CD4-bearing target cells. A proviral clone, termed JSP4-27, was identified to be transfection competent and to fully exhibit the noncytopathic and nonfusogenic properties of its parental isolate. Nucleotide sequence analysis of this clone revealed a genomic organization very similar to that of cytopathic HIV-2 strains and an overall nucleotide sequence homology of 88 to 90%. Amino acid sequence comparison confirmed the integrity of all major viral gene products in JSP4-27 but identified two amino acid sequence substitutions in its envelope fusion region. To investigate whether these mutations were responsible for the nonfusogenic phenotype of JSP4-27, we amplified, cloned, and sequenced the envelope fusion regions of four additional HIV-2/ST strains, two of which represented in vitro-generated, fusogenic and cytopathic variants of HIV-2/ST. The analysis showed that all HIV-2/ST strains examined, including the fusogenic variants, contained the same amino acid sequence changes. On the basis of these findings, we conclude that the attenuated phenotype of JSP4-27, and that of its parental virus, is not due to a direct alteration of the envelope fusion domain. Our results also show, for the first time, that individual replication-competent proviral clones can be representative of attenuated strains of HIV.

Amino Acid Sequence↗
PubMed1990

Human immunodeficiency virus type-2 gene expression: two enhancers and their activation by T-cell activators.

The human immunodeficiency viruses (HIVs) may include a spectrum of retroviruses with varying potential to infect their host, undergo long periods of latent infection, and induce pathology. Since expression of the viruses is in large part regulated by the sequence elements in their long terminal repeats (LTRs), this study was directed to an analysis of the regulatory elements in the HIV-2 LTR. The HIV-2 LTR was found to contain two enhancers. One of these enhancers is, in part, identical to the HIV-1 enhancer. This enhancer in HIV-1 is the T-cell activation response element; in HIV-2, however, it is the second enhancer that is mainly responsible for activation in response to T-cell activators. The second enhancer interacts with two nuclear binding proteins (85 kD and 27 kD mobility) that appear to be required for optimal enhancer function and activation. Observations such as these encourage the speculation that there may be subtle differences in the regulation of HIV-1 and HIV-2 expression that may be relevant to the possible longer latency and reduced pathogenicity of HIV-2.

Base Sequence↗
PubMed1989

Structure of simian immunodeficiency virus regulatory genes.

Three full-length cDNA clones were obtained from cells infected with the simian immunodeficiency virus (SIV) isolated from captive macaques (SIVMAC). Nucleotide sequence analyses suggested that these represented mRNA for the SIV MAC genes tat, rev (formerly, art/trs), and nef (formerly, 3'orf). The putative tat-specific clone was active in trans-activation of the SIV MAC long terminal repeat in COS-1 and Jurkat cells. In contrast, the human immunodeficiency virus 1 long terminal repeat was significantly trans-activated only in the COS-1 cells. This suggests that trans-activation by the SIV tat gene is modulated by cell-specific factors. The structure of all of the clones suggested an mRNA splicing pattern more complex than that described for human immunodeficiency virus 1.

Amino Acid Sequence↗
PubMed1988

D-penicillamine inhibits transactivation of human immunodeficiency virus type-1 (HIV-1) LTR by transactivator protein.

D-Penicillamine, an amino acid analogue of cysteine, has been shown to inhibit the transactivation of HIV-1 LTR by the transactivator protein, tat protein. The transactivation was studied in Jurkat cells co-transfected with plasmids containing HIV-LTR sequences fused to the bacterial chloramphenicol acetyltransferase (CAT) gene and HIV tat gene. The expression of CAT activity was a measure of transactivation of LTR by the tat protein. Incubation of transfected Jurkat cells with D-penicillamine led to inhibition of CAT activity. This inhibition was found to be concentration-dependent; more than 90% inhibition of chloramphenicol acetylation was seen in extracts prepared from cultures incubated with 40 micrograms/ml of D-penicillamine. Earlier experiments have shown that D-penicillamine at 40 micrograms/ml can completely inhibit HIV-1 (HTLV-III B) replication in H9 cells [(1986) Drug Res. 36, 184-186]. These results suggest that inhibition of transactivation may be the molecular mechanism involved in the inhibition of HIV-1 replication by D-penicillamine.

Cell Line↗
PubMed1988

Human immunodeficiency virus type 2 long terminal repeat: analysis of regulatory elements.

The long terminal repeats (LTRs) of the human immunodeficiency virus type 2 (HIV-2) and a related simian immunodeficiency virus (SIVmac) contain cis-acting positive regulatory elements upstream and the major transactivator gene (tat) response element and a possible negative regulatory element downstream of the transcriptional initiation site. The tat response element of HIV-2 and of SIVmac was more complex than that of HIV-1. Two structurally similar subelements within the HIV-2 tat response element could be identified. Both of these subelements were required for optimal transactivation by the HIV-2 tat gene product. Either of these subelements, however, was sufficient for transactivation by the HIV-1 tat gene product. These observations provide an explanation for the poor transactivation of HIV-1 LTR-directed gene expression by the HIV-2 tat gene product since the HIV-1 LTR contains an analog of only one of the HIV-2 subelements. The HIV-2 tat gene product also affected the function of the upstream elements, including enhancer activity. The response of these cis elements of HIV-2 to transactivation by HIV-2/SIVmac and HIV-1 tat gene differed somewhat in virus-infected and tat gene transfected cells, probably related to the differences in the effective concentration of the tat gene products and/or other viral or cellular factors. The steady-state levels of HIV-2 LTR-linked gene transcripts were much higher in the presence of HIV-2, SIVmac, and HIV-1 tat genes than in their absence, suggesting transcriptional modulation as a mechanism for tat gene function.

Base Sequence↗
PubMed1988

Human and simian immunodeficiency retroviruses: activation and differential transactivation of gene expression.

New West African human immunodeficiency viruses (HIV-2s) and simian immunodeficiency virus (SIV) contain functional transactivator (tat) gene and tat response elements. Their long terminal repeats (LTR) and tat genes are more related among themselves than to HIV-1 LTR and tat gene. The viral gene expression of HIV-2 as well as SIV can be stimulated by T cell activators, such as mitogens and phorbol esters. HIV-2 and SIV display a much broader transactivation response specificity than does HIV-1. The LTR-directed gene expression of HIV-2/SIV is not only transactivated by their own tat gene and by HIV-1 tat gene but also by factors in human T cell leukemia/lymphoma virus type I (HTLV-I) and simian virus 40 (SV40) infected cells, involving HTLV-I tat gene and SV40 T antigens, respectively. HIV-1 LTR-directed gene expression is much less transactivated by HIV-2/SIV tat genes and by factors in HTLV-I- and SV40-infected cells. Immune activation and heterologous transactivation of the LTR-directed gene expression may be relevant to the latency of virus infection and progression toward the acquired immunodeficiency syndrome (AIDS).

Animals↗
PubMed1987

3'-orf and sor genes of human immunodeficiency virus: in vitro transcription-translation and immunoreactive domains.

An in vitro transcription and translation procedure was designed to translate multiple open reading frames from cloned DNAs. For human immunodeficiency virus (HIV) cloned DNA carrying three open reading frames (sor, tat, and 3'-orf), the approach yielded three authentic polypeptides. Clearly, the internal initiation codons can be used for reinitiation of translation of the downstream open reading frames. However, the downstream open reading frames were translated with relatively lower translational efficiencies. In general, the translational efficiency of RNAs depended significantly on their structures. The in vitro approach was utilized further to map the immunoreactive domains of the 3'-orf and sor gene products of HIV. Deletion clones were constructed with deletions within the open reading frames. Translation products of these clones reacted differentially with anti-3'-orf and anti-sor rabbit immune sera and human sera from individuals with acquired immunodeficiency syndrome and related disorders. Apparently, recombinant 3'-orf and sor polypeptides used to immunize rabbits express many more immunogenic epitopes and/or different set of epitopes than is the case for the native proteins in humans infected with HIV. Immunoreactivity and immunogenicity of these gene products were significantly dependent on their structure and/or conformation.

Chromosome Deletion↗
PubMed1987

Genetic analysis of a new subgroup of human and simian T-lymphotropic retroviruses: HTLV-IV, LAV-2, SBL-6669, and STLV-IIIAGM.

A new primate retrovirus, STLV-IIIAGM, has been recently isolated from healthy African green monkeys and is apparently nonpathogenic in its natural host. However, spontaneous infection as well as inoculation of STLV-IIIAGM into macaques induces a disease with clinical features that resemble human AIDS. Independent isolates of human retroviruses, serologically closely related to STLV-IIIAGM, have been obtained from healthy individuals (HTLV-IV) and patients with immunodeficiency (LAV-2FG and SBL 6669) from West Africa. The latter have also been referred to as HIV-2 because, like HTLV-III/HIV-1, they may be associated with immune deficiency, or as West African human retroviruses because of their prevalence and probable origin from that region. We have molecularly cloned the STLV-IIIAGM genome and have generated probes from the gag-pol and envelope genes to analyze the genetic relatedness of these simian and human retroviruses. Our results indicate that all these retroviruses are genetically closely related to each other, HTLV-IV and STLV-IIIAGM differing only by a few restriction enzyme sites while LAV-2FG and SBL 6669 exhibit greater polymorphism from HTLV-IV/STLV-IIIAGM. These data mirror the variable degree of relatedness among members of the first subgroup of human retroviruses, HTLV-III/HIV.

Animals↗
PubMed1986

Synthesis of the complete trans-activation gene product of human T-lymphotropic virus type III in Escherichia coli: demonstration of immunogenicity in vivo and expression in vitro.

Human T-lymphotropic virus type III (HTLV-III) contains a gene (tat-III) the product of which activates the expression of viral genes in trans. We have expressed in Escherichia coli the complete tat-III-encoded protein as well as a truncated form that lacks three amino acids from the amino terminus. These proteins are recognized by sera of many, but not all, infected individuals including patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex, as well as asymptomatic seropositive persons. Seropositivity for the tat-III protein does not appear to correlate with the clinical stage of HTLV-III-related disease. Antibodies raised in rabbits against the E. coli-produced protein detect the native protein (apparent molecular mass, 14.5 kDa) in a virus-producing cell line. A second protein (26 kDa), of unknown origin but viral related, is also specifically recognized by the immune serum.

Base Sequence↗
PubMed1986

Three novel genes of human T-lymphotropic virus type III: immune reactivity of their products with sera from acquired immune deficiency syndrome patients.

Human T-lymphotropic virus type III or lymphoadenopathy associated virus (HTLV-III/LAV) is the cause of acquired immune deficiency syndrome (AIDS). In addition to the conventional retroviral genes involved in virus replication, namely, gag, pol, and env genes, DNA sequence analysis of HTLV-III genome predicted two additional open reading frames termed by us short open reading frame (sor) and 3' open reading frame (3' orf). Furthermore, functional analysis revealed another gene with transactivating function, termed tat. We have now structurally identified and functionally characterized these HTLV-III specific genes by way of cDNA cloning. DNA sequence analysis of the clones shows that the tat and 3' orf genes contain three exons and their transcription into functional mRNA involves two splicing events and that the sor gene contains at least two exons. In vitro transcription and translation of the cloned spliced sequences show that the sor, tat, and 3' orf genes code for polypeptides with apparent mobility of 24-25 kDa, 14-15 kDa, and 26-28 kDa, respectively. All three polypeptides are immune reactive and are immunogenic in the natural host. The results demonstrate that the three extra open reading frames of HTLV-III, two of which are unique to HTLV-III, are in fact genes that function in vivo and further allow the identification of three new and previously unrecognized HTLV-III antigens with differential immunogenicity in individuals with acquired immune deficiency syndrome and related disorders.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Polymorphism of the 3' open reading frame of the virus associated with the acquired immune deficiency syndrome, human T-lymphotropic virus type III.

The genome of the virus associated with the acquired immune deficiency syndrome (AIDS), human T-lymphotropic virus type III (HTLV-III), includes two open reading frames, not found in other retroviruses. One of these, designated 3' open reading frame (3'orf) is 648 base pairs (bp) in length, and overlaps with the 3' long terminal repeat (LTR) sequences. Sequences of additional HTLV-III clones were determined in order to estimate the level and location of variation within 3'orf, to gain some insight into the function of its protein product. Newly determined sequences are reported for 3'orf of two unintegrated clones of HTLV-III and three cDNA clones made from virion RNA derived from the same cell line infected with pooled blood samples of different patients with AIDS or AIDS-related complex symptoms (ARC). In addition, sequences for 3'orf were derived from an unintegrated viral clone derived from a different cell line infected with a distinct isolate from a single patient. These sequences are compared to those previously reported for six other viral clones. Sequences of 3'orf differ among clones by 1.1-10.4% bp and 2.4-17.0% of predicted amino acids. This represents significantly greater sequence variation than is found in the entire genome on average. Moreover, a functional proviral clone has a termination codon at amino acid residue 124 of this open reading frame. This raises questions concerning the structure, and regulation of expression of the protein encoded by 3'orf.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Trans-activator gene of human T-lymphotropic virus type III (HTLV-III).

Human T-lymphotropic virus type III (HTLV-III) encodes a trans-acting factor that activates the expression of genes linked to the HTLV-III long terminal repeat. By functional mapping of complementary DNA transcripts of viral messenger RNA's the major functional domain of the gene encoding this factor was localized to a region immediately before the env gene of the virus, a region previously thought to be noncoding. This newly identified gene consists of three exons, and its transcription into messenger RNA involves two splicing events bringing together sequences from the 5' part (287 base pairs), middle (268 base pairs), and 3'part (1258 base pairs) of the HTLV-III genome. A similar messenger RNA with a truncated second exon (70 base pairs) does not encode a trans-acting function. It is proposed that this second messenger RNA is the transcript of a gene (3'-orf) located after the env gene. Messenger RNA's were also identified for the env and gag-pol genes of HTLV-III.

Amino Acid Sequence↗
PubMed1985

Human T-cell growth factor (interleukin 2) and gamma-interferon genes: expression in human T-lymphotropic virus type III- and type I-infected cells.

Acquired immune deficiency syndrome (AIDS) is characterized by severe depletion of OKT4+ T lymphocytes and leukemia is associated with abnormal proliferation of maturation-arrested lymphocytes. Human T-lymphotropic virus type III (HTLV-III) or lymphoadenopathy virus (LAV) and type I (HTLV-I) are etiologically linked to AIDS and adult T-cell leukemia/lymphoma, respectively. T-cell growth factor (TCGF, also known as interleukin 2) is required for the growth of activated T-cells, which play an important role in immune regulation. gamma-Interferon (IFN-gamma) is also implicated in immune modulation. It was possible that T-cell depletion in acquired immune deficiency syndrome could be due to an impairment of TCGF synthesis and that adult T-cell leukemia could be due to unregulated production of TCGF. The results reported here show that the transcription of the TCGF gene was not impaired in cultured HTLV-III-infected cells. Paradoxically, the TCGF gene in HTLV-I-infected cells was transcriptionally inactive. The reverse was the case for the gamma-interferon gene--it was actively transcribed in HTLV-I-infected cells but not in the HTLV-III-infected and virus-producing H9 and H4 cell line. No evidence was obtained suggesting abnormal regulation of the TCGF or of the IFN-gamma gene consequent to HTLV-III infection. It thus appears that in both HTLV-III and HTLV-I infection, growth control and immune regulatory mechanisms may bypass a modulatory role of TCGF or of IFN-gamma.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Transcriptional modulation of human T-cell growth factor gene by phorbol ester and interleukin 1.

T-cell growth factor (TCGF) is a protein that is required for the continuous proliferation of activated normal T lymphocytes. It is produced by a subset of T lymphocytes upon appropriate stimulation. A human leukemic T-cell line (Jurkat) can be induced with the lectin phytohemagglutinin and the phorbol ester tetradecanoylphorbolacetate (TPA) to produce T-cell growth factor. This production was enhanced by including the lymphokine interleukin 1 in the induction medium. Interleukin 1 alone did not substantially increase T-cell growth factor production by cells treated only with phytohemagglutinin. These effects were preceded by and correlated with the induction of T-cell growth factor mRNA. Northern blot experiments with cloned TCGF DNA as a probe showed that TCGF mRNA was induced rapidly in cells treated with TPA and phytohemagglutinin, and this induction was augmented by interleukin 1. Thus, the production of T-cell growth factor was regulated at the level of its mRNA. Nuclear transcription experiments suggested that the TCGF gene was more actively transcribed in cells treated with TPA and phytohemagglutinin than in cells treated with phytohemagglutinin alone. The transcription of the TCGF gene was further increased when interleukin 1 was included along with TPA and phytohemagglutinin. When continued synthesis of RNA in induced cells was blocked with actinomycin D and cells were subsequently cultured in the presence or absence of inducing agents, the steady-state levels of TCGF mRNA declined in all cultures. This decline was roughly equivalent in cells incubated without the inducers and those incubated with phytohemagglutinin.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1984

Molecular characterization of human T-cell leukemia (lymphotropic) virus type III in the acquired immune deficiency syndrome.

The human T-cell leukemia (lymphotropic) virus type III (HTLV-III) appears to be central to the causation of the acquired immune deficiency syndrome (AIDS). Two full-length integrated proviral DNA forms of HTLV-III have now been cloned and analyzed, and DNA sequences of the virus in cell lines and fresh tissues from patients with AIDS or AIDS-related complex (ARC) have been characterized. The results revealed that (i) HTLV-III is an exogenous human retrovirus, approximately 10 kilobases in length, that lacks nucleic acid sequences derived from normal human DNA; (ii) HTLV-III, unlike HTLV types I and II, shows substantial diversity in its genomic restriction enzyme cleavage pattern; (iii) HTLV-III persists in substantial amounts in cells as unintegrated linear DNA, an uncommon property that has been linked to the cytopathic effects of certain animal retroviruses; and (iv) HTLV-III viral DNA can be detected in low levels in fresh (primary) lymphoid tissue of a minority of patients with AIDS or ARC but appears not to be present in Kaposi's sarcoma tissue. These findings have important implications concerning the biological properties of HTLV-III and the pathophysiology of AIDS and Kaposi's sarcoma.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Homology of genome of AIDS-associated virus with genomes of human T-cell leukemia viruses.

A T lymphotropic virus found in patients with the acquired immune deficiency syndrome (AIDS) or lymphadenopathy syndrome has been postulated to be the cause of AIDS. Immunological analysis of this retrovirus and its biological properties suggest that it is a member of the family of human T-lymphotropic retroviruses known as HTLV. Accordingly, it has been named HTLV-III. In the present report it is shown by nucleic acid hybridization that sequences of the genome of HTLV-III are homologous to the structural genes (gag, pol, and env) of both HTLV-I and HTLV-II and to a potential coding region called pX located between the env gene and the long terminal repeating sequence that is unique to the HTLV family of retroviruses.

Acquired Immunodeficiency Syndrome↗
PubMed1984

T-cell growth factor gene: lack of expression in human T-cell leukemia-lymphoma virus-infected cells.

Activated mature T cells require T-cell growth factor (TCGF) for continuous proliferation. However, many mature T cells infected with human T-cell leukemia-lymphoma virus grow independently of exogenously added TCGF. It is now reported that cells infected with this virus also lack detectable TCGF messenger RNA (less than one copy per cell) and thus do not produce their own growth factor. The results apparently rule out an autostimulation mechanism of growth control.

Cell Line↗