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A T Haase

Publications and source records attributed to A T Haase.

At least 55 records · Page 3Linked to original sources
PubMed1994

The rev gene of visna virus is required for productive infection.

To assess the role of the animal lentivirus rev regulatory gene product in the life cycle of visna virus, we introduced mutations into the functional fourth exon of the rev gene of visna virus. Cultured cells transfected with a full-length clone of visna DNA produce infectious virus but visna DNA with mutations in rev does not. The documented requirement for a functional rev gene in productive infections establishes the essential role of this gene in the replication of an animal lentivirus.

Amino Acid Sequence↗
PubMed1993

Massive covert infection of helper T lymphocytes and macrophages by HIV during the incubation period of AIDS.

Animal and human lentiviruses elude host defences by establishing covert infections and eventually cause disease through cumulative losses of cells that die with activation of viral gene expression. We used polymerase chain reaction in situ double-label methods to determine how many CD4+ lymphocytes are latently infected by human immunodeficiency virus (HIV) in patient lymph nodes and whether the pool of infected cells is large enough to account for immune depletion through continual activation of viral gene expression and attrition of cells responding to antigens. We discovered an extraordinarily large number of latently infected CD4+ lymphocytes and macrophages throughout the lymphoid system from early to late stages of infection, and confirmed the extracellular association of HIV with follicular dendritic cells. Follicular dendritic cells may transmit infection to cells as they migrate through lymphoid follicles. Latently infected lymphocytes and macrophages constitute an intracellular reservoir large enough ultimately to contribute to much of the immune depletion in AIDS, and represent a difficult problem that must be resolved in developing effective treatments and protective vaccine.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Analysis of human immunodeficiency virus-infected tissues by amplification and in situ hybridization reveals latent and permissive infections at single-cell resolution.

Latent and productive viral infections are at the extremes of the spectrum of virus-cell interactions that are thought to play a major role in the ability of such important human pathogens as human immunodeficiency virus (HIV) to elude host defenses and cause disease. The recent development of PCR-based methods to amplify target sequences in individual cells in routinely fixed tissues affords opportunities to directly examine the subtle and covert virus-cell relationships at the latent end of the spectrum that are inaccessible to analysis by conventional in situ hybridization techniques. We have now used PCR in situ with in situ hybridization to document latent and permissive HIV infection in routinely fixed and paraffin-embedded tissue. In one of the first specimens we examined, a tumor biopsy from an HIV-infected individual, we found many of the lymphocytes and lymphocytes infiltrating the tumor had HIV DNA that was detectable only by PCR in situ. The fraction of positive cells varied regionally, but there were foci where most of the cells contained HIV DNA. Most of these lymphocytes and macrophages are latently infected, as we could detect HIV RNA in fewer than one in a thousand of these cells. We also detected HIV RNA, surprisingly, in 6% of the tumor cells, where the number of copies of viral RNA per cell was equivalent to productively infected cell lines. The alternative states of HIV-gene expression and high local concentration of latently infected lymphocytes and monocytes revealed by these studies conceptually supports models of lentiviral pathogenesis that attribute persistence to the reservoir of latently infected cells and disease to the consequences of viral-gene expression in this population. The magnitude of infection of lymphocytes documented in this report is also consistent with the emerging view that HIV infection per se could contribute substantially to depletion of immune cells in AIDS.

Adenocarcinoma↗
PubMed1993

Increased expression of heat shock protein, transferrin, and beta 2-microglobulin in astrocytes during scrapie.

Scrapie is a slow infection and neurodegenerative disease of animals characterized pathologically by formation of amyloid, astrocytosis, vacuolation and injury and death of neurons. Our previous studies of scrapie point to: (i) a critical role for the astrocyte in responding to, and perhaps inadvertently contributing to, the neuropathological manifestations of infection; and (ii), the hypothesis that the astrocyte executes a programed response to neurological injury analogous to the stress response. The expression of genes encoding transferrin and beta 2-microglobulin has been shown to increase during scrapie and we sought in the studies reported here to determine whether this modulated expression would map to astrocytes. We also looked for changes in a heat shock protein that is induced in the stress response. We show that transferrin, beta 2-microglobulin and heat shock 72 kD protein all increase in astrocytes in the course of infection. We speculate in the discussion on the possible functions of these and other proteins in neurodegenerative processes and why these functions so frequently reside in the astrocyte.

Animals↗
PubMed1992

nef-naf nexus?

Explore the source record for details and available documents.

Journal Article↗
PubMed1991

Scrapie-associated prion protein accumulates in astrocytes during scrapie infection.

In the course of scrapie, a transmissible spongiform encephalopathy caused by an unconventional agent, a normal cellular protein is converted to an abnormal form that copurifies with infectivity and aggregates to form deposits of amyloid. We have used immunocytochemistry and methods that enhance detection of amyloidogenic proteins to investigate the types of cells in the central nervous system which are involved in the formation of the abnormal scrapie-associated protein. We show that this protein accumulates in astrocytes prior to the cardinal neuropathological changes in scrapie--astrogliosis, vacuolation, neuron loss, and amyloid deposition. These findings implicate the astrocyte in the formation of the scrapie isoform of the prion protein and amyloid in scrapie and suggest that this cell type might also be involved in the replication of the scrapie agent.

Amyloid↗
PubMed1991

Isolation of replication-competent molecular clones of visna virus.

Visna virus is the prototypic member of a subfamily of retroviruses responsible for slow infections of animals and humans. As a part of our investigation of the functions of viral gene products in virus replication, we have isolated three infectious molecular clones and determined the complete nucleotide sequences of two of the clones. We have also characterized the progeny of the biologically cloned viral stocks and of the infectious clones and document considerable heterogeneity in plaque size and antigenic phenotype of the former that is reduced to near homogeneity in the progeny of the infectious clones. It thus should now be possible to trace the emergence of antigenic variants of visna virus as well as ascribe defined functions to structural and regulatory genes of the virus in determining neurovirulence and the slow tempo of infection.

Amino Acid Sequence↗
PubMed1991

In situ amplification of visna virus DNA in tissue sections reveals a reservoir of latently infected cells.

Maedi and visna are, respectively, the pulmonary and neurological manifestations of slowly progressive infections of sheep caused by retroviruses of the lentivirus subfamily. Lentivirus infections are also persistent infections in which host defenses are generally not successful in eliminating the infectious agent because of restricted viral gene expression in many infected cells. In this report, we describe a method for amplifying and detecting viral DNA in tissue sections which has made it possible to verify experimentally the postulated existence of this reservoir of latently infected cells, as well as to estimate the actual number of cells which harbor viral genomes in infected tissues. In the discussion, we present a simple mathematical model that relates this number to the rate at which inflammatory lesions develop. This model can account for both the slow progression of natural infections and for the rapid accumulation of inflammatory foci in the high dosage experimental system analysed in our studies.

Animals↗
PubMed1991

Neuropathological changes in scrapie and Alzheimer's disease are associated with increased expression of apolipoprotein E and cathepsin D in astrocytes.

With the rationale that the neuropathological similarities between scrapie and Alzheimer's disease reflect convergent pathological mechanisms involving altered gene expression, we set out to identify molecular events involved in both processes, using scrapie as a model to study the time course of these changes. We differentially screened a cDNA library constructed from scrapie-infected mice to identify mRNAs that increase or decrease during disease and discovered in this way two mRNAs that are increased in scrapie and Alzheimer's disease. These mRNAs were subsequently shown by sequence analysis to encode apolipoprotein E and cathepsin D (EC 3.4.23.5). Using in situ hybridization and immunocytochemistry to define the cellular and anatomic pathology of altered gene expression, we found that in both diseases the increase in apolipoprotein E and cathepsin D mRNAs and proteins occurred in activated astrocytes. In scrapie, the increase in gene expression occurred soon after the amyloid-forming abnormal isoform of the prion protein has been shown to accumulate in astrocytes. In Alzheimer's disease, the increased expression of cathepsin D also occurred in association with beta-amyloid. These studies reveal some of the molecular antecedents of neuropathological changes in scrapie and Alzheimer's disease and accord new prominence to the role of astrocytes in neurodegenerative conditions.

Aged↗
PubMed1990

Amplification and detection of lentiviral DNA inside cells.

Visna virus and human immunodeficiency virus are prototypes of animal and human lentiviruses, respectively, that persist and are disseminated despite the host immune response because cells in the tissues and the bloodstream harbor viral genomes in a covert state. To facilitate identification of these latently infected cells, the polymerase chain reaction has been adapted to amplify viral DNA in fixed cells for detection by in situ hybridization. By using a multiple primer set that generates DNA segments with overlapping cohesive termini, visna virus DNA can be amplified, retained, and detected in infected cells with sensitivities that exceed those of existing methods by more than 2 orders of magnitude. This advance in single-cell technology should prove useful in diagnosing and gaining insight into the pathogenesis of viral infections and provide new opportunities to look for viruses in chronic diseases of unknown etiology.

Animals↗
PubMed1990

Human herpes virus infections and Alzheimer's disease.

Herpes viruses cause acute and chronic diseases of the peripheral and central nervous systems and have been implicated in the aetiology of Alzheimer's disease (AD). In this investigation the relevance of human herpes virus infection to AD was assessed by in situ hybridization. The abundant latency associated transcript(s) of herpes simplex virus type 1 (HSV-1) were detected at a significantly higher incidence in the trigeminal ganglia of individuals with AD than in controls. But we could find no evidence of viral RNA in the central nervous system (CNS), looking specifically in the hippocampal cortex of demented individuals with extensive neuropathological changes of AD. These studies solve one problem in testing the viral hypothesis of causation, i.e. the sensitivity of the methods used in the search for latent infection. But the central issue remains unresolved because of necessity, only the end stage of a prolonged pathophysiological process has been examined. Our conclusions are qualified accordingly.

Alzheimer Disease↗
PubMed1989

Increased monokines in cytomegalovirus infected myelomonocytic cell cultures.

In an investigation of the role of monokines in CMV associated immunosuppression we document modulation of both TNF and IL-1 beta in CMV infected THP-1 cells. CMV infected cultures released almost two-fold more IL-1 beta protein and contained significantly higher IL-1 beta mRNA levels than uninfected cultures for 72-96 h after induction. In both CMV infected and uninfected cultures, significant amounts of IL-1 beta protein were not detected until 24 h post induction, while maximum amounts of TNF were detected in culture supernatants by 3 h post induction, suggesting that TNF may play a role in IL-1 beta induction. TNF levels subsequently declined but in infected cultures remained over 2.5-fold higher than controls through 96 h. The CMV alteration in the kinetics and extent of IL-1 beta release must be indirectly mediated by CMV since only 1% of THP-1 cells were infected. Most infected cells expressed CMV immediate early proteins but did not overexpress IL-1. We speculate that CMV infected cells release excess TNF or other stimulatory factors which increase IL-1 beta synthesis. Since IL-1 beta is increased, the decreased IL-1 'activity' described by others as an explanation in part for the immunosuppressive effects of infection may actually reflect alterations of IL-1 inhibitor levels during CMV infection.

Autoradiography↗
PubMed1987

The molecular pathogenesis of astrogliosis in scrapie and Alzheimer's disease.

In slow infections caused by scrapie and other unconventional agents, and in Alzheimer's disease (AD), the formation of neuritic plaques and the increase in astrocytes and astrocyte-specific protein, glial fibrillary acidic protein (GFAP), are pathological changes common to both conditions. With the rationale that these parallels imply convergent pathogenetic mechanisms, we identified a gene whose expression increases in both. We now report the results of a more extensive analysis of this gene and show that by sequence analysis it is highly homologous and likely identical to GFAP. GFAP mRNA accumulates late in the course of scrapie in subpial and periventricular astrocytes and in cells in foci in the hippocampus. The increased abundance of GFAP mRNA is accompanied by an increase in the corresponding protein. GFAP mRNA is localized by in situ hybridization to the cell body and processes of astrocytes. In AD, the latter pattern predominates, consistent with induction of GFAP mRNA in the sites of synthesis in glial processes in the neuritic plaque.

Alzheimer Disease↗
PubMed1987

Interactions of human cytomegalovirus with leukocytes in vivo: analysis by in situ hybridization.

Reactivation of human cytomegalovirus (HCMV) from latency occurs in immunosuppressed individuals and infection is itself immunosuppressive. To better understand the basis for this virally induced impairment of immune function, we have analyzed virus-leukocyte interactions by in situ hybridization. We detected viral DNA in 12 viremic patients in the mononuclear cell population, predominantly in cells identified as monocytes by their morphology and by labelling the cells with a monocyte specific monoclonal antibody prior to in situ hybridization. We detected immediate early RNA in infected cells at frequencies comparable to DNA (10(-3) to 10(-5)). By contrast, no viral transcripts were detected in polymorphonuclear cells and viral DNA was inclusively cytoplasmic in accord with the interpretation that this cell type harbors HCMV in phagosomes. These findings in vivo continue to suggest that infection of monocytes plays an important part in the immunosuppressive effects of HCMV infections.

Autoradiography↗
PubMed1987

Detection of herpes virus genome in Alzheimer's disease by in situ hybridization: a preliminary study.

The hypothesis that the limbic predilection for the histopathological lesions of Alzheimer's disease may be due to reactivation of Herpes simplex virus from the trigeminal ganglia is being tested by in situ hybridization, utilizing post mortem tissues harvested in a longitudinal study of this organic dementia. Techniques demonstrating Herpes virus DNA with sensitivity in the subgenomous range have already shown that this common viral agent resides in latent form within the Gasserian neurones of aged individuals. The possibility that such material when reactivated could travel via trigeminal branches to the medial temporal lobe of the human brain is under investigation.

Aged↗