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Biomedical subjects

A L Notkins

Publications and source records attributed to A L Notkins.

At least 73 records · Page 4Linked to original sources

Transplantation of skin from human immunodeficiency virus type 1-transgenic mice to normal congenic mice results in graft rejection.

Skin from mice transgenic (Tg) for part of the human immunodeficiency virus type 1 (HIV-1) genome was transplanted onto normal mice of the same strain. All Tg grafts were rejected within 29 days. In contrast, skin from normal mice that was transplanted to HIV-1-Tg recipients remained viable for > 67 days. Histologic examination of Tg grafts on normal mice showed evidence of monocytic infiltrates. Monocytic infiltrates were not observed, however, when either normal or Tg skin was transplanted onto Tg mice. Immunohistologic staining verified the presence of gp120 protein expression in the Tg-transplanted skin but not in adjacent normal skin. It is concluded that the Tg mice are immunologically tolerant to the HIV-1 gene products they express.

Animals↗

Both VH and VL chains of polyreactive IgM antibody are required for polyreactivity: expression of Fab in Escherichia coli.

Monoclonal polyreactive antibodies can bind to many structurally dissimilar self and non-self antigens. Neither the precise antigen-binding site on the polyreactive antibody molecule nor the molecular basis of polyreactivity has been elucidated. The present study was initiated to see whether antibody genes encoding the Fab fragment of a human monoclonal polyreactive IgM antibody (MoAb 67) could be efficiently expressed in Escherichia coli, and whether the bacterially expressed Fab fragments possessed biological activity. cDNA encoding the variable domains of the heavy and light chains of MoAb 67 were cloned, amplified by polymerase chain reaction (PCR) and expressed in E. coli. Neither the recombinant heavy nor light chain showed antigen-binding activity. In contrast, the recombinant Fab 67 fragment showed the same antigen-binding reactivity profile as the native IgM antibody. It is concluded that the antigen-binding activity of polyreactive antibodies resides in the Fab fragment, and that both the heavy and light chains are required for activity.

Antibodies, Anti-Idiotypic↗

Maternal-fetal interactions affect growth of human immunodeficiency virus type 1 transgenic mice.

Infants vertically infected with human immunodeficiency virus type 1 (HIV-1) often manifest profoundly deficient growth with failure to thrive. The pathologic mechanisms that produce growth failure associated with pediatric HIV infection are not clear. Transgenic mice homozygous for a gag/pol deletion mutant of the infectious provirus pNL4-3 have been found to manifest a similar growth failure pattern. To explore the influence of HIV-1 on fetal growth and maternal-fetal interactions, we examined intrauterine growth of transgenic and nontransgenic mice and evaluated the consequence of embryo transfer into normal and heterozygous transgenic mothers. Mice homozygous for the HIV transgene had normal intrauterine and birth weights but uniformly displayed severe growth retardation postnatally. Transgene expression was prominent in transgenic fetuses and their placentas and in uteri of transgenic mothers, as determined by Northern analysis. Although embryo transfer did not affect intrauterine growth, the pregnancy rate in transgenic mothers was markedly lower than in nontransgenic controls. In both fetal and neonatal tissues, transgene expression was significantly greater in homozygous animals when compared with heterozygotes, but the difference was magnified postnatally. These results suggest that HIV gene expression affected both mother and neonate. In the mother, expression of the HIV-1 transgene reduced postfertilization pregnancy rate. Once the animal was pregnant, however, the effects of transgene expression on the homozygous fetus were overcome in utero, possibly by the contribution of maternal factors or by inhibition of HIV-1 gene expression by a fetal or maternal factor(s). In the neonate, HIV-1 transgene expression increased dramatically in homozygotes and was associated with profound growth failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Transgenic models of HIV-1.

Transgenic technology has been very successful at providing insights into possible processes involved in HIV-induced pathogenesis. The availability of these small animal models for the study of HIV-related syndromes including KS, epidermal proliferative lesions, HIV-associated nephropathy, AIDS-related growth failure and cachexia may well facilitate the development of novel therapies for these complications. Other phenotypes created in mice, such as cataracts and hepatic cancer [59], may not have human analogies but may still provide insight into pathogenesis. Thus, transgenic models have already provided resources to study many manifestations of AIDS and others are likely to be developed. The optimal strategy for designing future transgenic animals, however, is less clear. No transgenic mouse model has been generated to date that will provide an avenue for vaccine development. This advance awaits the further discovery of the host factors that facilitate the virus replicative cycle in humans and a better understanding of these pathways in the mouse. For the development of molecular-based therapy, however, the currently available models may well be adequate to test molecular inhibitors of transcription [7,60,61] and post-transcriptional processing of viral mRNA [62]. Whether single or multigenic constructs under the control of the LTR are better or worse for this purpose is a debatable issue. Transgenic technology may yet make an additional contribution to the development of molecular therapy for AIDS. The best method of demonstrating that a gene therapeutic strategy is safe to administer to patients has not been determined. By introducing potentially therapeutic constructs into mice as transgenes, their safety can be assessed in many different cell types in vivo, analogous to toxicological testing in rodents for systemically administered drugs. Thus, transgenic technology has already provided insights into the pathogenesis of HIV-1. While it has not yet proven its utility for vaccine development, transgenic technology holds the promise of being an active participant in the development of both safe and effective gene therapy approaches for the treatment of AIDS.

AIDS Dementia Complex↗

Isolation, sequence and expression of a novel mouse brain cDNA, mIA-2, and its relatedness to members of the protein tyrosine phosphatase family.

This study describes the isolation of a putative transmembrane protein tyrosine phosphatase (PTP), mIA-2, from a mouse brain cDNA library. The cDNA encodes 979 amino acids containing a unique extracellular domain and a single intracellular catalytic domain. Expression of mIA-2 was found primarily in the central nervous system and in neuroendocrine cells. The sequence shares a high degree of homology with its human counterpart (92% identity), especially in the intracellular domain, which shows 99.3% identity between the two species. In both human and mouse IA-2, several substitutions were found in the highly conserved regions including an Ala to Asp substitution in the core sequence. Bacterial expression of a glutathione S-transferase fusion protein showed that mIA-2 had no enzyme activity with conventional substrates such as Raytide, myelin basic protein, angiotensin, RR-src and pNpp. When tested with the total tyrosine-phosphorylated cellular proteins isolated on an anti-phosphotyrosine antibody column, it also showed little, if any, enzyme activity. These findings suggest that mIA-2 is a new member of the transmembrane PTP family that either has very narrow substrate specificity perhaps requiring post-translational modification for enzyme activity or has a still unknown biological function.

Amino Acid Sequence↗

Growth failure and AIDS-like cachexia syndrome in HIV-1 transgenic mice.

The mechanisms which predispose to growth failure in infants and children infected with immunodeficiency virus type-1 (HIV-1) are not fully understood. The contributions of viral replication and CD4+ T cell depletion to growth failure in an HIV-1 transgenic mouse model were investigated. Mice homozygous for the transgene, a gag-pol deletion mutant of the HIV-1 provirus pNL4-3, exhibited marked cachexia, growth retardation, lymphoproliferation with a reduction in the percentage of CD4+ T cells but an increase in the absolute number of splenic CD4+ and CD8+ T cells, thymic hypoplasia, and early death. Despite the absence of T cells, athymic nude mice, homozygous for the HIV transgene, displayed comparable growth failure. The results indicate that AIDS-like cachexia may be produced by expression of viral envelope or accessory genes, need not be accompanied by absolute depletion of CD4+ T cells, and may occur independent of T cell function.

Acquired Immunodeficiency Syndrome↗

Genomic organization, 5'-upstream sequence, and chromosomal localization of an insulinoma-associated intronless gene, IA-1.

IA-1 is a novel cDNA originally isolated from a human insulinoma subtraction library (ISL-153). It encodes a protein containing both a zinc finger DNA-binding domain and a putative prohormone domain. IA-1 transcripts have been found thus far only in tumors of neuroendocrine origin. Clinical studies have shown that IA-1 is a sensitive marker for neuroendocrine differentiation of human lung tumors. In this study, we cloned and sequenced the entire IA-1 gene and its 5'-upstream region from a human liver genomic library. In situ hybridization localized the IA-1 gene to the short arm of human chromosome 20. Sequence analysis and restriction enzyme mapping showed that the IA-1 gene is uninterrupted and appears to be intronless. Evidence that IA-1 is an intronless gene that can translate into protein was obtained from in vitro translation studies that showed that both IA-1 cDNA and IA-1 genomic DNA yielded identical protein products of approximately 61,000 daltons. Examination of the 5'-upstream region (2090 base pairs) revealed several tissue-specific regulatory elements, including glucokinase upstream promoter elements and a Pit-1 factor binding site. The presence of several different upstream regulatory elements may account for IA-1 gene expression in different neuroendocrine tumors.

Base Sequence↗

cDNA sequence and genomic organization of mouse secretin.

A murine insulinoma library was constructed by subtracting glucagonoma cDNAs from insulinoma cDNAs. Comparison of the nucleotide sequence of one of the clones with sequences from the GenBank database showed that it was a member of the secretin family. The clone, 490 bp long, encodes a protein of 133 amino acids consisting of a signal peptide, a N-terminal peptide, secretin, and a C-terminal peptide, which showed 88% and 80% homology with rat and porcine secretin precursor proteins, respectively. The translated secretin peptide showed a unique Met to Thr substitution at position 5 as compared to the secretins from other species. That the Met to Thr substitution was not tumor-related was demonstrated by the fact that an identical sequence was found in cDNA from normal mouse intestine. Studies on the mouse secretin gene revealed that it contains four exons separated by 81 bp, 110 bp, and 96 bp introns.

Amino Acid Sequence↗

Modulation of the expression of CD5 antigen on the surface of human peripheral B lymphocytes.

In this study, we investigated the expression of CD5 molecules on the surface of mature human peripheral B lymphocytes. Human CD5+ B cells were isolated from tonsils and peripheral blood. Their terminal differentiation into plasma cells was induced with IL-2. In the presence of this lymphokine, a subset of CD5+ B cells ceased to express CD5 proteins on their surface. When CD5+ B cells and non-B cells were removed from the suspension. CD5 antigens were spontaneously reexpressed on the surface of CD5- B cells. This suggests that the CD5- phenotype of a subset of B cells in these suspensions resulted from pressure(s) exerted on them by the other cellular components of the suspensions. B cells which have reexpressed membrane CD5 in the absence of CD5+ B cells and non-B cells retained their ability to reprogress to CD5- phenotype and to undergo terminal differentiation into plasma cells when stimulated with IL-2. A short exposure (4 hr) of CD5- B cells to 5 nM IL-2 resulted in the loss of their capability to spontaneously reexpress surface CD5 in the absence of other lymphoid cells. Taken together, these data suggest that the expression of CD5 antigens on B cell membrane is governed by a network-type balance between all cellular compartments within the suspension. Fluctuations of this equilibrium results in the shuttling of B cells between CD5+ and CD5+ phenotypes until they become irreversibly engaged in the terminal differentiation pathway. The interconversion CD5+<==>CD5- on B cell membrane does not argue for CD5 molecule as the marker of a distinct B cell lineage.

Antigens, CD↗

Half-life of polyreactive antibodies.

Monoclonal polyreactive antibodies bind to a variety of self and foreign antigens. In contrast, monoclonal monoreactive antibodies bind to a single or restricted number of known antigens. The rate at which polyreactive antibodies are removed from the circulation compared to monoreactive antibodies has not been determined. In the present experiments, human monoclonal polyreactive and monoreactive antibodies of different isotypes were injected intravenously into mice and the clearance from the circulation was determined. The half-life of polyreactive IgM, IgA, and IgG antibodies was 8.0, 8.2, and 9.8 hr, respectively, compared to 35.4, 26.6, and 280 hr for monoreactive IgM, IgA, and IgG antibodies, respectively. Examination of tissue sections from animals given intravenous antibody showed substantial deposition of polyreactive, but not monoreactive, antibodies in several organs, the liver being the principal site of deposition. It is concluded that polyreactive antibodies are cleared from the circulation substantially faster than monoreactive antibodies.

Animals↗

Polyreactive IgM antibodies in the circulation are masked by antigen binding.

Human plasma containing IgM showed only minimal, if any, reactivity with a panel of antigens as measured by ELISA. In contrast, affinity-purified IgM showed many times more reactivity with the same panel of antigens. When plasma was added back to the affinity-purified IgM, the reactivity of the IgM with antigens was completely inhibited by undiluted plasma and by as much as 40% with as little as a 1:100 dilution of plasma. When the affinity-purified IgM was affinity-purified a second time by passage through antigen-specific columns (e.g., insulin or Fc or beta-galactosidase), the eluted antibodies bound not only to the antigen used for purification, but also to a panel of unrelated antigens, indicating that the antibodies were polyreactive. It is concluded that polyreactive IgM antibodies are present in the circulation but are masked by binding to circulating antigens.

Antibody Specificity↗

bFGF and its low affinity receptors in the pathogenesis of HIV-associated nephropathy in transgenic mice.

HIV-associated nephropathy is characterized by extensive tubulointerstitial disease with epithelial cell injury, microcystic proliferation, and tubular regeneration with glomerulosclerosis. To explore the role of bFGF as a mediator of HIV-induced interstitial disease, we utilized an HIV transgenic mouse model that manifests clinical and histological features observed in patients. In transgenic mice, simultaneous renal epithelial cell proliferation and injury were detected in vivo. In areas of microcystic proliferation, immunoreactive bFGF colocalized with extracellular matrix. Kidneys from transgenic mice had increased bFGF low affinity binding sites, particularly in the renal interstitium. In vitro, transgenic renal tubular epithelial cells proliferated more rapidly and generated tubular structures spontaneously, in marked contrast to nontransgenic renal cells where these pathologic features could be mimicked by exogenous bFGF. These studies suggest that renal bFGF and its receptors play an important role in the pathogenesis of HIV-associated nephropathy.

AIDS-Associated Nephropathy↗

Molecular cloning and identification of a receptor-type protein tyrosine phosphatase, IA-2, from human insulinoma.

A novel 3.6-kb cDNA, IA-2, with a 2,937-bp open reading frame was isolated from a human insulinoma subtraction library (ISL-153). The predicted amino acid sequence and in vitro-translated product of IA-2 cDNA revealed a 979-amino-acid protein with a pI value of 7.09 and a molecular mass of 105,847 daltons. The protein sequence is consistent with a signal peptide, an extracellular domain, a transmembrane region, and an intracellular domain. The extracellular domain contains an unusual cysteine-rich region following the signal peptide. The intracellular cytoplasmic domain of IA-2 possesses highly conserved regions similar to the catalytic domains found in members of the protein tyrosine phosphatase (PTP) family. Northern blot analysis showed that IA-2 mRNA was expressed in five of five freshly isolated human insulinomas, rat and mouse insulinoma cell lines, and enriched normal mouse islets. It also was found in normal human brain, pituitary, pancreas, and brain tumor cell lines, but not in a variety of other normal or tumor tissues. Based on the sequence and expression data, it appears that IA-2 is a new member of the receptor-type PTP family that is expressed in islet and brain tissues.

Amino Acid Sequence↗

Development of human monoclonal antibodies to rabies.

A total of nine human monoclonal antibodies (MAbs) to rabies virus were generated from peripheral B lymphocytes of subjects immunized with human diploid cell rabies vaccine by somatic cell hybridization. The MAbs were analyzed for their antigen-binding specificities using ELISA, Western blot, and immunoprecipitation assays. The different assays made it possible to identify MAbs directed to the surface glycoprotein, nucleoprotein, nominal phosphoprotein, and matrix protein. One of the MAbs that recognized the surface glycoprotein neutralized rabies virus.

Antibodies, Monoclonal↗

Human polyreactive and monoreactive antibodies: effect of glycosylation on antigen binding.

The present experiments were initiated to determine whether the carbohydrate portions of antibody molecules contribute to polyreactivity. Cell lines making human monoclonal polyreactive or monoreactive antibodies of the immunoglobulin (Ig) M, IgG and IgA isotypes were treated with tunicamycin to block N-linked glycosylation of the proteins. Analysis of the secreted native and non-glycosylated proteins revealed a > 95% inhibition of [3H]mannose incorporation. Electrophoresis on sodium dodecyl sulphate-polyacrylamide gels of the proteins from tunicamycin-treated cells showed increased mobility and the absence of [3H]mannose incorporation of the immunoglobulin heavy chains, consistent with the lack of glycosylation. The native and non-glycosylated antibodies were then tested for their ability to bind different antigens. Despite the lack of glycosylation, both polyreactive and monoreactive antibodies bound to antigens with little if any loss of reactivity or specificity. It is concluded that the carbohydrate moieties do not contribute significantly to polyreactivity.

Antibodies, Bispecific↗

Clearance of LDH-5 from the circulation of inbred mice correlates with binding to macrophages.

Flow cytometry showed that the enzyme lactate dehydrogenase (LDH-5) binds to peritoneal macrophages. The degree of binding appears to be genetically controlled and varies depending on the inbred strain of mouse. The rate at which LDH-5 is cleared from the circulation correlates with the degree of binding to macrophages. These findings suggest that the binding of LDH-5 to macrophages may serve as an in-vitro index of enzyme clearance.

Animals↗

IA-1, a new marker for neuroendocrine differentiation in human lung cancer cell lines.

IA-1 is a recently isolated novel complementary DNA which encodes a protein of 510 amino acids that contains both a zinc finger DNA-binding domain and a putative prohormone domain. mRNA expression of IA-1 has been found thus far only in tumors of neuroendocrine origin. In this report we describe the expression of IA-1 mRNA in a panel of 64 human lung cancer cell lines. IA-1 mRNA was detected by Northern blot analysis in 97% (30 of 31) of small cell lung cancer cell lines. In contrast, IA-1 mRNA was detected in only 13% (4 of 30) of non-small cell lung cancer cell lines. Nine of the 30 (30%) expressed either chromogranin A mRNA or produced L-dopa decarboxylase. Four of these 9 (44%) had detectable levels of IA-1 mRNA. In most of the lung cancer cell lines examined, IA-1 showed high concordance with the other neuroendocrine markers, L-dopa decarboxylase, and chromogranin A. The one exception was a variant small cell lung cancer cell line which expressed low or nondetectable levels of L-dopa decarboxylase. IA-1 is a candidate marker of neuroendocrine differentiation of human lung tumors.

Biomarkers, Tumor↗