Improved procedure for the measurement of telomere length in whole cells by PNA probe and flow cytometry.

OBJECTIVES: Peptide nucleic acid (PNA) probes hybridize to denatured telomeric sequences in cells permeabilized in hot formamide. In reported protocols, the hybridization was conducted in solutions with high formamide concentrations to avoid the DNA renaturation that can hamper binding of the oligo-PNA probe to specific sequences. We postulated that telomeric DNA, confined in the nuclear microvolume, is not able to properly renature after hot formamide denaturation. Therefore, to improve hybridization conditions between the probe and the target sequences, it might be possible to add probe to sample after the complete removal of formamide. MATERIALS AND METHODS: After telomeric DNA denaturation in hot formamide solution and several washes to remove the ionic solvent, cells were hybridized overnight at room temperature with human telomere-specific PNA probe conjugated with Cy5 fluorochrome, Cy5-OO-(CCCTAA)(3) . After stringency washes and staining with ethidium bromide, the cells were analysed by flow cytometry and by using a confocal microscope. RESULTS: Using three continuous cell lines, different in DNA content and telomere length, and resting human peripheral blood T and B lymphocytes, we demonstrated that the oligo-PNA probe hybridized to telomeric sequences after complete removal of formamide and that in the preserved nucleus, telomeric sequence denaturation is irreversible. CONCLUSION: According to our experience, oligo-PNA binding results is efficient, specific and proportional to telomere length. These, our original findings, can form the technological basis of actual in situ hybridization on preserved whole cells.

Lymphocyte activation gene-3 (LAG-3) expression and IFN-gamma production are variably coregulated in different human T lymphocyte subpopulations.

We evaluated the relationship between cytokine profile and the expression of the lymphocyte activation gene-3 (LAG-3) in both T cell clones and polyclonal T cell lines; LAG-3 is a CD4-like protein whose expression is reportedly restricted to Th1/0 cells and dependent upon IFN-gamma. We found that, while LAG-3 was expressed only by CD4+ T cell clones producing IFN-gamma, most CD8+ clones producing IL-4 but not IFN-gamma (i.e., with a T cytotoxic-2-like profile) were LAG-3+. The intensity of LAG-3 expression by CD8+ clones correlated with the amount of released IFN-gamma, suggesting that this cytokine is not required for expression but rather for the up-regulation of LAG-3. Flow cytometric analyses of polyclonal T cell lines confirmed that LAG-3 could be expressed by both CD4+ and CD8+ cells that did not contain cytoplasmic IFN-gamma. In these cell lines, large proportions of CD4+ and CD8+ cells coexpressed LAG-3 and CD30, a putative marker of Th2-like cells. Overall, our data do not support the earlier suggestion that LAG-3 and CD30 are selective markers of T cells with type-1 and type-2 cytokine profiles, respectively.

Death of bystander cells by a novel pathway involving early mitochondrial damage in human immunodeficiency virus-related lymphadenopathy.

Destruction of immune cells in peripheral lymphoid tissues plays presumably a pivotal role in acquired immune deficiency syndrome pathogenesis. We found that cell suspensions obtained from lymph nodes of eight human immunodeficiency virus (HIV)-infected individuals contained variable proportions (2.1% to 18.3%, median 11.2%) of dead lymphocytes permeable to supravital dyes, represented by CD4+, CD8+, and B cells. The frequency of dead cells correlated directly (R = 0.847) with the amount of HIV provirus in the cell populations, and HIV provirus was enriched in the dead cell fractions. Similar proportions of dead cells were observed in cell suspensions from lymphadenopathic lymph nodes of HIV- donors, but not from small resting HIV- lymph nodes. Electron microscopic and flow cytometric analyses revealed that most dead cells from HIV+ lymph nodes lacked internucleosomal DNA fragmentation but displayed combined features of apoptosis and necrosis, eg, chromatin condensation and mitochondrial swelling. Cells with similar morphology were readily identified in lymph node tissue sections, and marked mitochondrial swelling could be occasionally observed in cells with otherwise normal morphology. Our findings have two major implications. One is that the in vivo cell death in HIV-infected lymph nodes occurs predominantly through a novel pathway, related to but distinct from classical apoptosis and characterised by early and severe mitochondrial damage. The second implication is that HIV-related lymphadenopathy is accompanied in vivo by massive destruction of uninfected lymph node cells. Comparable levels of cell death were observed in other inflammatory lymphadenopathies not related to HIV; however, the uniquely endless and generalized nature of HIV lymphadenopathy might render this "inflammatory" cell destruction a powerful pathogenetic mechanism, accounting for the progressive disruption and depletion of lymphoid tissues seen in HIV infection.

Comparison of the Vbeta repertoire in peripheral blood and in lymph nodes of HIV-infected subjects reveals skewed usage predominantly in CD8+ T cells.

Perturbations of the repertoire of variable-beta (Vbeta) regions of the T cell receptor have been observed in patients infected by HIV and have been attributed to stimulation by viral antigens or superantigens. We further sought for traces of HIV-induced perturbations by comparing Vbeta repertoire in peripheral blood and in lymphoid tissues of six infected patients. Vbeta expression was studied with a panel of 17 anti-Vbeta antibodies covering about 50% of the entire repertoire. We observed major divergences between lymph nodes and peripheral blood in the expression of several Vbeta segments, and these differences were significantly more frequent in CD8+ than in CD4+ T cells (P = 0.0097). Vbeta2 was perturbed in CD8 cells from all but one patient. One HIV-negative subject with localized reactive lymphadenopathy of unknown etiology had four perturbed Vbeta segments, including Vbeta2, in CD8+ cells, while another uninfected subject with an unreactive lymph node architecture had no perturbations. Our findings suggest that stimulation by HIV or by other antigens determines divergences in the Vbeta repertoire between lymphoid tissues and peripheral blood predominantly in CD8+ T cells.

Measurement of apoptotic cells in peripheral blood.

The measurement of apoptosis in peripheral blood might represent a useful tool in acquired immunodeficiency syndrome (AIDS) and cancer research. Among the many assays that are currently used to identify apoptotic leukocytes, flow cytometric methods are the most valuable in terms of rapidity, simplicity, and level of analytical detail. Some flow cytometric assays may also offer the additional advantage of detecting the earliest phases of apoptosis, which is paramount importance for measuring apoptotic cells in vivo before they are destroyed by phagocytes.

Frequency of provirus-bearing CD4+ cells in HIV type 1 infection correlates with extent of in vitro apoptosis of CD8+ but not of CD4+ cells.

Lymphocytes from HIV-1-infected subjects undergo massive apoptosis when cultured in vitro, and this phenomenon might reflect pathogenetic mechanisms leading to immune dysfunction in vivo. However, (1) lymphocyte death is not restricted to CD4+ cells but seems to involve predominantly CD8+ cells, and (2) the same phenomenon occurs in other viral infections. Furthermore, it is not known whether a relationship exists between the HIV-1 burden and this type of cell death. In this work we sought to determine whether the HIV-1 provirus load correlates with the propensity to apoptosis of CD4+ and CD8+ cells. We studied 10 HIV-1-infected patients with CD4+ cell counts above 500/mm3 and free of concomitant infections. We correlated the frequency of HIV-1-infected CD4+ cells with the extent of culture-induced apoptosis as well as with the phenotype of the apoptotic lymphocytes. We found that the magnitude of apoptosis correlated with the frequency of HIV-1-infected CD4+ cells (p = 0.0007), and that increasing viral load and apoptosis were associated with a shift to the selective death of CD8+ cells. Our data support the view that, in addition to CD4+ cell killing, another immunopathogenic effect of HIV might be that of priming CD8+ cells to apoptosis. In vivo, this could eventually lead to the exhaustion of the cytotoxic T cell compartment.

Detection and characterization of apoptotic peripheral blood lymphocytes in human immunodeficiency virus infection and cancer chemotherapy by a novel flow immunocytometric method.

We have developed a quantitative and sensitive flow cytometric method for the detection of human apoptotic lymphocytes that, unlike previously described assays, allows their identification in mixed populations of peripheral blood leukocytes as well as their immunophenotyping. Apoptotic lymphocytes are identified on the basis of peculiar light scatter changes, reflecting their smaller size and their modified nucleus/cytoplasm organization, and of the decreased expression of surface CD45 molecules. Based on these criteria, apoptotic lymphocytes generated by exposure to ionizing radiation can be easily distinguished from viable cells and from necrotic lymphocytes generated by treatment with antibody and complement. Using this assay, we reappraised the phenomenon of the in vitro apoptosis of lymphocytes from patients with human immunodeficiency virus (HIV) infection. Lymphocytes from HIV patients, unlike those from normal HIV-negative subjects, undergo apoptosis upon simple in vitro culture. We found that the percentages of lymphocytes undergoing apoptosis were significantly higher in patients with low CD4 cell counts (< 400/microL) than in patients at earlier stages (> 400 CD4 cells/microL). However, phenotypic analysis disclosed that apoptotic lymphocytes generated in these cultures were mostly CD8+ T cells and CD19+ B cells. Thus, in contrast to what has been previously suggested, the phenomenon of in vitro lymphocyte apoptosis might not be pathogenetically related to the depletion of CD4+ T cells in acquired immunodeficiency syndrome. Nevertheless, it might represent an useful marker of disease progression. Our assay allows the analysis of unfractionated peripheral blood leukocytes and thus the identification of apoptotic lymphocytes circulating in vivo. Apoptotic lymphocytes could indeed be detected in the circulation of a patient with cancer shortly after high-dose cytotoxic chemotherapy. By contrast, no apoptotic lymphocytes could be detected in vivo in patients with early or advanced HIV infection.

Cholinergic markers are expressed in developing and mature neurons of chick dorsal root ganglia.

The presence of acetylcholinesterase has been reported in chick dorsal root ganglia at early developmental stages although acetylcholine is not known to play a role in these ganglia. Recently, we reported that during development the level of acetylcholinesterase increases continuously and the enzyme becomes gradually expressed in all sensory neurons. These observations prompted the study of the developmental pattern of expression of other cholinergic markers, such as choline acetyltransferase (ChAT) and the high affinity transport mechanism for choline. ChAT activity is barely detectable at early developmental stages (E7) and increases markedly thereafter, with an activity profile similar to that described for acetylcholinesterase. A similar increase in enzyme activity is also observed when ChAT is measured in dorsal root ganglia explants and in dissociated cells in culture. The study of ChAT activity in cultured cells shows an increase over a period of 3 days, thus ruling out the hypothesis that motor fibers, still associated to the ganglia, may represent a possible source of the enzyme. Immunostaining of whole ganglia or cultured cells shows that ChAT immunoreactivity is not restricted to a specific neuronal sub-population but appears as a common marker of sensory neurons. High affinity choline uptake, blocked by hemicholinium, is present in sensory neurons cultured from E7 dorsal root ganglia. Observations on cultured neurons from later stages (E18) indicate that choline transport is not a transient property of sensory neurons. These observations show a similar pattern of expression of several cholinergic markers during development. Such a pattern is maintained at significant levels also in mature ganglia.

Sulphate polyanions prolong the incubation period of scrapie-infected hamsters.

The effect of the organic sulphated polyanions, pentosan sulphate (SP54), dextran sulphate 500 (DS500) and suramin, have been tested on golden Syrian hamsters infected with the 263K strain of scrapie by the intraperitoneal (i.p.) or the intracerebral route. SP54 had the greatest effect in prolonging the incubation period of the disease when administered within 2 h of the i.p. inoculum. The same amount of SP54 given 24 h after scrapie inoculation had a potent effect in some animals and no effect in others. This result suggests that SP54 inhibits the uptake of the scrapie agent into the nerve endings and/or carrier cells at the site of the inoculum, i.e. the peritoneum, and that this event occurs in about 24 h. DS500 had a similar although less potent effect (22.4 days delay during the incubation period) than SP54 (54.4 days) when administered within 2 h of scrapie injection by the i.p. route, and suramin had only a minimal effect (10 days). This study suggests that treatment of scrapie and related spongiform encephalopathies of animals and man is possible only before the agent has reached the clinical target areas of the brain.

Experimental drug treatment of scrapie: a pathogenetic basis for rationale therapeutics.

Pharmacological treatment with polyanions or amphotericin B in hamsters with experimental scrapie reveals that it is possible to delay the appearance of the disease only when the drug is given before the invasion of the agent into the clinical target areas of the brain. We suggest such early treatment may be possible for individuals at high risk of acquiring the disease, such as healthy mutation-positive relatives of patients with familial Creutzfeldt-Jakob disease or Gerstmann-Sträussler syndrome, or recipients of potentially contaminated pituitary-extracted human growth hormone.