Intensity-dependent modulatory effects of vagus nerve stimulation on cortical excitability.

OBJECTIVES: Vagus nerve stimulation (VNS) is an effective treatment for refractory epilepsy. It remains unknown whether VNS efficacy is dependent on output current intensity. The present study investigated the effect of various VNS output current intensities on cortical excitability in the motor cortex stimulation rat model. The hypothesis was that output current intensities in the lower range are sufficient to significantly affect cortical excitability. MATERIAL AND METHODS: VNS at four output current intensities (0 mA, 0.25 mA, 0.5 mA and 1 mA) was randomly administered in rats (n = 15) on four consecutive days. Per output current intensity, the animals underwent five-one-hour periods: (i) baseline, (ii) VNS1, (iii) wash-out1, (iv) VNS2 and (v) wash-out2. After each one-hour period, the motor seizure threshold (MST) was measured and compared to baseline (i.e. ∆MSTbaseline , ∆MSTVNS 1 , ∆MSTwash-out1 , ∆MSTVNS 2 and ∆MSTwash-out2 ). Finally, the mean ∆MSTbaseline , mean ∆MSTwash-out1 , mean ∆MSTwash-out2 and mean ∆MSTVNS per VNS output current intensity were calculated. RESULTS: No differences were found between the mean ∆MSTbaseline , mean ∆MSTwash-out1 and mean ∆MSTwash-out2 within each VNS output current intensity. The mean ∆MSTVNS at 0 mA, 0.25 mA, 0.5 mA and 1 mA was 15.3 ± 14.6 µA, 101.8 ± 23.5 µA, 108.1 ± 24.4 µA and 85.7 ± 18.1 µA respectively. The mean ∆MSTVNS at 0.25 mA, 0.5 mA and 1 mA were significantly larger compared to the mean ∆MSTVNS at 0 mA (P = 0.002 for 0.25 mA; P = 0.001 for 0.5 mA; P = 0.011 for 1 mA). CONCLUSIONS: This study confirms efficacy of VNS in the motor cortex stimulation rat model and indicates that, of the output current intensities tested, 0.25 mA is sufficient to decrease cortical excitability and higher output current intensities may not be required.

Leukemic CD3+ LGL share functional properties with their CD8+ CD57+ cell counterpart expanded after BMT.

Leukemic T-LGL (large granular lymphocyte) composed of clonal CD3+ TCR alphabeta+ CD8+ CD57+ cells were compared with oligoclonally CD3+ CD8hi+ CD57- lymphocytes expanded after BMT. Leukemic CD3+ CD8hi+ CD57+ LGL showed several phenotypic differences such as an upregulation of CD16 and adhesion molecules (mainly CD11c, CD58 and CD54), activation markers and an exclusive CD45RA isoform expression. Unstimulated CD3+ CD8+ CD57+ LGL from both leukemic and BMT donors spontaneously developed an ex vivo CTL-like CD3-redirected cytotoxicity but no NK cell activity. Different stimuli (PHA, PMA or rhIL-2) induced similar cytotoxic profiles after a 6-day culture involving a CD3-redirected lysis predominating over a low NK cell activity. However, culture of leukemic LGL with these stimuli allowed either a 2 week persistence (PMA or rhIL-2) of CD8+ CD57+ LGL or their disappearance after 3 days (PHA). Furthermore, leukemic CD8hi+ CD57+ T lymphocytes produced an inhibitor of cytotoxic functions as previously described for BMT recipients' CD8+ CD57+ cells. Thus, despite some phenotypic differences between both cell sources, leukemic CD57+ T-LGL display the same functional characteristics of cytotoxic effector and immunoregulatory T cells as CD8+ CD57+ T cells from BMT recipients which might represent their normal counterpart.

[Live attenuated measles vaccine as a potential multivalent pediatric vaccination vector]. / Utilisation potentielle du vaccin vivant atténué contre la rougeole comme vecteur de vaccination pédiatrique multivalent.

Live attenuated RNA viruses make highly efficient vaccines. Among them, measles virus (MV) vaccine has been given to a very large number of children and shown to be highly efficacious and safe. MV vaccine induces a life-long immunity after a single or two low-dose injections. It is easily produced on a large scale in most countries and can be distributed at low cost. Reversion to pathogenicity has never been observed with this vaccine. For all these characteristics, MV vaccine might be a very promising vector to immunize children against both measles and other infectious agents such as HIV or flaviviruses, in the developing world. In this article, we describe recent data demonstrating the capacity of recombinant Schwarz measles virus to express proteins from Human Immunodeficiency or West Nile viruses, and to induce specific immune responses able, in the case of West Nile virus, to protect from an experimental challenge.

Application of the potassium-titanyl-phosphate laser during extraocular muscle surgery: technique and histopathology.

We determined laser parameters and delivery system requirements for successful use of the potassium-titanyl-phosphate (KTP) laser for strabismus surgery and its histopathologic effect on extraocular muscle, tendon, sclera, and cornea of human and rabbit eyes. Enucleated cadaver eyes and exenterated rabbit orbital contents were used. Using a 200-microns fiberoptic tip delivery system, varying laser energies were used to perform muscle insertion site and corneal damage, tenotomies, and myotomies. Pulse durations of 0.5 second and energies above 0.8 watt were needed for tenotomy or myotomy. No damage to the surrounding tissues or sclera was observed with laser tenotomy or myotomy performed 0.5 mm from the insertion site. Energy above 0.8 watt applied directly caused full thickness disruption. In comparison to scissor myotomy, the laser provided charring of the superficial tissues. This study shows that the KTP laser can be safely and accurately used for extraocular muscle tenotomy or myotomy.

Cutting edge: RANTES regulates Fas ligand expression and killing by HIV-specific CD8 cytotoxic T cells.

Based on the previous observation that RANTES mediates the cytotoxic activity of human HIV-specific CD8+ T cells via the chemokine receptor CCR3, we studied the effect of this chemokine on different effector CD8+ cytolytic cells requiring Fas/Fas ligand (FasL) or perforin-dependent pathway. In CTLs derived from PBMCs of HIV-infected patients, both the spontaneous and the RANTES-induced cytotoxicity were inhibited by anti-FasL neutralizing Abs. In contrast, allogeneic CTLs or NK cells killing through perforin were not affected by RANTES and anti-FasL Ab. Accordingly, RANTES enhanced the expression of FasL in a concentration- and time-dependent manner in HIV-specific CTLs, whereas anti-RANTES Ab decreased markedly FasL expression. Finally, cell surface expression of FasL protein in HIV-specific CTLs was also up-regulated by eotaxin, a selective ligand for CCR3. Our observations show that the action of RANTES via CCR3 is necessary to regulate FasL expression on HIV-specific CD8+ T cells that kill through the Fas/FasL pathway.

An inhibitor of cytotoxic functions produced by CD8+CD57+ T lymphocytes from patients suffering from AIDS and immunosuppressed bone marrow recipients.

An inhibitor of the cytotoxic functions (ICF) mediated by human immunodeficiency virus (HIV)- or HLA-specific cytotoxic T lymphocytes, natural killer and lymphokine-activated killer (LAK) cells is secreted by CD8+CD57+ T lymphocytes, a subset expanded during infection with HIV and after bone marrow transplantation. We previously showed an apparent molecular mass of 20-30 kDa for this soluble glycosylated concanavalin A-binding inhibitor which is distinct from known cytokines. Here, we report a characterization of the mechanism of action of this CD8+CD57+ ICF. We show that the ICF-induced inhibition of LAK cell cytolytic activity is transient, with a spontaneous recovery of cytolytic potential after 18 h. When testing interactions of ICF with a large set of cytokines we found that the ICF-mediated inhibition of cytotoxic functions is antagonized by two cytokines: recombinant interleukin (rIL)-4 and recombinant interferon (rIFN)-gamma. Finally, we show that ICF acts at the level of cytolytic effector cells, where it induces a significant increase of cyclic AMP (cAMP) level. In contrast, no modification of either cell surface antigen expression or of target/effector cell conjugate formation could be evidenced. Addition of rIL-4 and rIFN-gamma reverses such an increase of cAMP levels and in parallel restores the cytolytic activity. Altogether, these data demonstrate that the glycoprotein ICF produced by CD8+CD57+ cells (1) inhibits cell-mediated cytotoxicity by sensitizing cytolytic effector cells to the cAMP pathway, and (2) is part of a cytokine network controlling cell-mediated cytotoxic functions.

Dynamics of HIV-specific CD8+ T lymphocytes with changes in viral load.The RESTIM and COMET Study Groups.

The influence of HIV burden variations on the frequencies of Ag-specific CD8+ T cell responses was evaluated before and during highly active antiretroviral therapy by analyzing the number, diversity, and function of these cells. The frequencies of HLA-A2-restricted CD8+ PBL binding HLA-A2/HIV-epitope tetramers or producing IFN-gamma were below 1%. A panel of 16 CTL epitopes covering 15 HLA class I molecules in 14 patients allowed us to test 3.8 epitopes/patient and to detect 2.2 +/- 1.8 HIV epitope-specific CD8+ subsets per patient with a median frequency of 0.24% (0.11-4. 79%). During the first month of treatment, viral load rapidly decreased and frequencies of HIV-specific CD8 PBL tripled, eight new HIV specificities appeared of 11 undetectable at entry, while CMV-specific CD8+ PBL also appeared. With efficient HIV load control, all HIV specificities decayed involving a reduction of the CD8+CD27+CD11ahigh HIV-specific effector subset. Virus rebounds triggered by scheduled drug interruptions or transient therapeutic failures induced four patterns of epitope-specific CD8+ lymphocyte dynamics, i.e., peaks or disappearance of preexisting specificities, emergence of new specificities, or lack of changes. The HIV load rebounds mobilized both effector/memory HIV- and CMV-specific CD8+ lymphocytes. Therefore, frequencies of virus-specific CD8 T cells appear to be positively correlated to HIV production in most cases during highly active antiretroviral therapy, but an inverse correlation can also be observed with rapid virus changes that might involve redistribution, sequestration, or expansion of these Ag-specific CD8 T cells. Future strategies of therapeutic interruptions should take into account these various HIV-specific cell dynamics during HIV rebounds.

CD8hi+CD57+ T lymphocytes are enriched in antigen-specific T cells capable of down-modulating cytotoxic activity.

Major expansions of CD8hi+CD57+ T lymphocytes frequently occur during human immunodeficiency virus (HIV) infection and after transplantation. To investigate mechanisms of such cell expansion, we compared the activation and functional status of CD8hi+CD57+ and CD57-peripheral blood lymphocytes (PBL) from normal, bone marrow transplantation (BMT) and HIV+ donors. The CD8hi+CD57+ PBL from BMT and HIV+ donors preferentially displayed CD38 and HLA-DR activation markers without correlation between CD8hi+CD57+ percentages and HIV load, the CD45RA+ isoform in all ex vivo conditions but acquired CD45RO after in vitro expansion, CD11b and CD11c in BMT and HIV+ donors but decreased expression of CD62-L, VLA-2 and VLA-6. The CD8hi+CD57+ cells were positive for perforin and granzyme B and spontaneously mediated cytolytic activity in a CD3-redirected assay. In contrast the inhibitor of cytolytic functions (ICF) produced by CD8hi+CD57+ cells down-modulated the CD3-redirected cytolytic activity but only at low levels of CD3 cross-linking. While CD3-triggering induced a low, if any, short-term proliferation of CD8+CD57+ cells, this subset could be amplified after long-term stimulation either with mitogens or with HIV antigens, thereby enriched in HIV-specific T cells producing tumor necrosis factor-alpha. Altogether these data suggest that CD8hi+CD57+ cells represent a terminal differentiation state of activated effector cytotoxic T lymphocytes which are enriched in antigen-specific T cells and down-modulate their own cytolytic potential, thus participating in a negative control of effector cell functions during persistent viral infections or transplantations.