Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0021051 (immunodeficiency)
71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used a recombinant vaccinia virus (VV) which expresses high levels of human immunodeficiency virus-1 (HIV-1) gag proteins to analyze the processing pathway of the gag p55 precursor. HIV-1 gag proteins were isolated from [3H]leucine-labeled VV:gag-infected H9 T lymphocytes by immunoprecipitation with either anti-p24, anti-p17, or anti-p6 antibodies. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that processing of the p55 precursor involves three major intermediates (p41a, p41b, and p39). The p41a and p39 proteins contain the p17 and p24 protein segments, and the p41b is comprised of p24 and p15 segments. On two-dimensional gels, each intermediate as well as the mature p24 and p17 proteins migrated as distinct species. [3H]Myristic acid labeling of the HIV-1 gag proteins revealed that in addition to p55 and p17, the p41a and p39 intermediates, but not p41b, are myristylated, confirming that myristylation occurs at the NH2 terminus before cleavage of the p55 precursor protein. We conclude that the myristylated HIV-1 gag p55 precursor is initially cleaved at random either at the p17/p24 junction or at two sites between p24 and p15 proteins, resulting in three intermediates (p41a, p41b, and p39) which are subsequently cleaved to yield mature gag proteins.
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PMID:Identification of protein intermediates in the processing of the p55 HIV-1 gag precursor in cells infected with recombinant vaccinia virus. 278 91

The prevalence of antibodies to human immunodeficiency virus (HIV = LAV/HTLV-III) in a rural population from the Ifakara area in southeastern Tanzania was investigated. Sera from 286 individuals collected from 1982 to 1984 in connection with a study on liver disorders were tested by an ELISA. Fifty-two (18.2%) of the sera were found positive. While the positives were largely confirmed by one commercial ELISA, they were completely negative by two others. Confirmatory testing by Western blot and competition Western blot showed that the reactivity detected by more sensitive of these assays was largely due to IgG antibodies binding to the HIV core (gag) proteins p17, its precursor p55 and, in some cases, p24. These tests also indicated, however, that the reactive antibodies could not have been elicited by HIV, but possibly by an unknown retrovirus or another cross-reactive agent. Thus, by 1984, the area investigated was largely free of HIV infection, but a significant proportion of its population may harbor another retrovirus of unknown pathogenicity.
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PMID:Specificity of human immunodeficiency virus (LAV/HTLV-III)-reactive antibodies in African sera from southeastern Tanzania. 287 46

Structural heterogeneity in human immunodeficiency virus (HIV-1) isolates from different sources has been reported. In order to investigate if the virus exhibits heterogeneity in vivo, HIV-1 was isolated over a 3 year period (1983-1985) from a blood donor who progressed from the asymptomatic carrier state to frank AIDS. The HIV-1 specific proteins were characterized and compared by metabolic labelling and immunoprecipitation of infected cells and by Western blot analysis of gradient purified isolates. The data indicate polymorphism in the apparent size of gag gene-encoded p55 and env gene-encoded p41 proteins. The possibility of genomic variations was evaluated by studying the restriction enzyme polymorphism of integrated proviral DNA. Genetic diversity between 1983, 1984 and 1985 isolates was demonstrated by a change in the number and/or size of restriction fragments. In addition, genetic variation was also observed in HIV-1 isolated from the blood transfusion recipient of this donor. Subsequent analysis of the quantitative and qualitative titre of HIV-1 specific antibodies in the donor recipient sera demonstrated a concomitant change with the observed structural variation in the virus. These studies may be useful in elucidating virus or host-related critical events which lead to the onset of AIDS following infection with HIV-1.
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PMID:DNA and protein heterogeneity in serial isolates of human immunodeficiency virus (HIV-1): indication of change in vivo. 289 45

Retroviral proteins, including those from the human immunodeficiency virus (HIV), are synthesized as polyprotein precursors that require proteolytic cleavage to yield the mature viral proteins. A 99-residue polypeptide, encoded by the 5' end of the pol gene, has been proposed as the processing protease of HIV. The chemical synthesis of the 99-residue peptide was carried out by the solid-phase method, and the isolated product was found to exhibit specific proteolytic activity upon folding under reducing conditions. Upon size-exclusion chromatography, enzymatic activity was eluted at a point consistent with a dimeric molecular size. Specificity was demonstrated by the cleavage of the natural substrate HIV gag p55 into gag p24 and gag p17, as well as cleavage of small peptide substrates representing processing sites of HIV fusion proteins. The proteolytic action of the synthetic product could be inhibited by pepstatin, an aspartic protease inhibitor.
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PMID:Chemical synthesis and enzymatic activity of a 99-residue peptide with a sequence proposed for the human immunodeficiency virus protease. 305 Sep 88

Both membrane (p55) and soluble (p45) forms of TAC-reactive interleukin-2 receptor (IL-2R) are expressed and/or released by activated lymphocytes or monocytes. Previous work has detected increased levels of circulating, TAC-soluble IL-2R (soluble TAC antigen) in the serum of most B-cell chronic lymphocytic leukemia (B-CLL) patients. We detected soluble TAC antigen in B-CLL patients (mean of 3,332 U/mL v 410 for controls). Serum soluble TAC antigen levels increased with stage (mean value of 1,187 U/mL for stage 0 v 2,527 for stage 2 and 5,410 for stages 3 and 4). We next attempted to determine whether the elevated serum levels of soluble TAC antigen in B-CLL patients might result from shedding or secretion of the receptor from the circulating, malignant B cells. Purified, malignant B cells from B-CLL patients were capable of producing easily detectable soluble TAC antigen after 48 hours of in vitro culture (range of 60 to 1,563 U/mL). IL-2R production by CLL B cells was dose dependent in most patients over a concentration of 10 x 10(6) to 60 x 10(6)/mL. In contrast, there was little or no detectable soluble TAC antigen when highly purified T cells from the same patients were cultured. Finally, despite elaboration of soluble IL-2R by CLL B cells, membrane expression of B-cell IL-2R was detected in only six of 11 patients. Thus, the cellular source of the elevated serum IL-2R levels is the malignant CLL B cell. Taken together these data suggest that (a) the malignant CLL B cell is "activated" in terms of release of soluble IL-2R and may serve as a tumor marker in this disease and (b) the elevated levels of circulating IL-2R may be an associated factor in the cellular immunodeficiency noted in B-CLL patients.
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PMID:The malignant B cells from B-chronic lymphocytic leukemia patients release TAC-soluble interleukin-2 receptors. 313 58

Isolation of the human immunodeficiency virus (HIV) has been attempted from the cerebrospinal fluid (CSF) of 29 subjects with varying severity of HIV infection. Virus could be isolated from patients in all stages of disease including patients with primary HIV infection and asymptomatic carriers. In the early stages of infection free virus was infrequently present in the CSF but could be isolated from the cells present in CSF. This suggests that HIV may reach the brain at a very early stage of infection and that initially there is little production of virus from infected cells. In the late stages of HIV infection, associated with increasing severity of immunodeficiency, free virus could readily be isolated from the CSF. With one exception, all of these patients had neurological and/or psychiatric symptoms, as compared to only 2 (of 13) subjects in the early stages of infection. All patients with HIV-specific antibodies in serum had antibodies also in CSF. Examined by a radioimmunoprecipitation assay, CSF was more often found to contain antibodies to the precursor (p55) of viral core proteins than the corresponding serum of the patients. We propose that immune disturbances have an essential pathogenic role in the neurological/psychiatric symptoms associated with HIV infection, possibly through allowing increased viral expression in the central nervous system.
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PMID:Human immunodeficiency virus infection of the brain. I. Virus isolation and detection of HIV specific antibodies in the cerebrospinal fluid of patients with varying clinical conditions. 321 22

Retroviral proteins are synthesized as polyprotein precursors that undergo proteolytic cleavages to yield the mature viral proteins. The role of the human immunodeficiency virus (HIV) protease in the viral replication cycle was examined by use of a site-directed mutation in the protease gene. The HIV protease gene product was expressed in Escherichia coli and observed to cleave HIV gag p55 to gag p24 and gag p17 in vitro. Substitution of aspartic acid residue 25 (Asp-25) of this protein with an asparagine residue did not affect the expression of the protein, but it eliminated detectable in vitro proteolytic activity against HIV gag p55. A mutant HIV provirus was constructed that contained the Asn-25 mutation within the protease gene. SW480 human colon carcinoma cells transfected with the Asn-25 mutant proviral DNA produced virions that contained gag p55 but not gag p24, whereas virions from cells transfected with the wild-type DNA contained both gag p55 and gag p24. The mutant virions were not able to infect MT-4 lymphoid cells. In contrast, these cells were highly sensitive to infection by the wild-type virions. These results demonstrate that the HIV protease is an essential viral enzyme and, consequently, an attractive target for anti-HIV drugs.
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PMID:Active human immunodeficiency virus protease is required for viral infectivity. 329 Sep 1

The mature gag and pol proteins of human immunodeficiency virus (HIV) and all retroviruses derive from large gag and gag-pol polyprotein precursors by posttranslational cleavage. A highly specific, virally encoded protease is required for this essential proteolytic processing. In this study, the HIV protease gene product was expressed in Escherichia coli and shown to autocatalyze its maturation from a larger precursor. In addition, this bacterially produced HIV protease specifically processed an HIV p55 gag polyprotein precursor when coexpressed in E. coli. This system will allow detailed structure-function analysis of the HIV protease and provides a simple assay for the development of potential therapeutic agents directed against this critical viral enzyme.
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PMID:Human immunodeficiency virus protease expressed in Escherichia coli exhibits autoprocessing and specific maturation of the gag precursor. 332 Oct 60

Electrophoretic immunoblotting (EIB [Western blotting]) has emerged as the major method for verification of seropositivity for human immunodeficiency virus (HIV) and therefore needs to be thoroughly characterized. The specificities of three EIB systems, our own and two commercial systems, were studied with anticellular sera and serial dilutions of human sera. We demonstrated that in one system, anti-HLA classes I and II gave bands comigrating with viral proteins, which can be controlled by EIB with uninfected H9 cells. In addition, animal antisera, including anti-immunoglobulin enzyme conjugates, occasionally reacted with HIV gag proteins, necessitating appropriate controls. Whereas none of 10 blood donors reacted at the standard dilution in serum (1/100 or 1/400) in any of the three systems, 6, 1, and 2 of 10 donors reacted with p24, p55, or both at a dilution of 1/10 for the three systems tested. Thus, nonspecific reactions can arise in several ways and justify critical EIB interpretation. The sensitivity of the three systems was studied by comparative titrations and direct quantification of bound immunoglobulin G (IgG). In the titrations with all three, the minor anti-HIV bands p53 and p64, coded from pol, were often detectable in higher dilutions than were antibodies to any other HIV protein. The minimum visible amounts of IgG bound per HIV protein band estimated by extra- and interpolation in densitometric curves and liquid scintillation counting of radiolabeled patient IgG were approximately 0.1, 0.05, and 0.02 ng per band in the three systems. One of the commercial systems had both the highest sensitivity and highest specificity.
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PMID:Specificities and sensitivities of three systems for determination of antibodies to human immunodeficiency virus by electrophoretic immunoblotting. 342 44

A current concept of the serological response to human immunodeficiency virus (HIV) infection in humans is that antibodies to core antigens (p55, p24, and p15) are detectable earlier during initial stages of antibody production than antibodies against envelope antigens (gp160, gp120, and gp41). Comparative studies of Western blot (immunoblot), radioimmunoprecipitation assay (RIPA), and enzyme-linked immunosorbent assay (ELISA) during initial antibody production are limited to case reports and have not resolved the issue. Thirty of the 37 participants who are part of a prospective study had at least one specimen that was negative for anti-gp41 but had one or more other bands on Western blot. Twenty-seven of these 30 specimens were reactive for anti-gp120/160 in the RIPA. Of the same 30 specimens, kits from Bionetics identified 2 (7%), ElectroNucleonics 4 (13%), Abbott 13 (43%), Du Pont 25 (83%), and Genetic Systems 25 (83%). All participants had evidence of serological progression by Western blot, including a gp41 band, on subsequent visits; the ELISA kits of all manufacturers identified these later specimens with greater accuracy. These data show that the RIPA detects anti-envelope antibodies that may be not detectable by Western blot and that the production of anti-envelope antibodies approximately parallels the production of anti-core antibodies. The false-negative results by ELISA would permit transmission of HIV by blood transfusion from donors in early stages of infection. The sensitivity of licensed ELISA kits should be improved to identify antibody as soon as possible after infection.
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PMID:Detection of early antibodies in human immunodeficiency virus infection by enzyme-linked immunosorbent assay, Western blot, and radioimmunoprecipitation. 347 69


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