Recognition of nonstructural protein-peptides by cytotoxic t-lymphocytes raised against japanese encephalitis-virus

We have previously reported that Lyt(2+) cytotoxic T lymphocytes (CTL) can be raised against Japanese encephalitis virus (JEV) in BALB/c mice. In order to confirm the presence of H-2K(d)-restricted CTL and to examine their cross-recognition of West Wile virus (WNV), we tested the capacity of anti-JEV CTL to lyse uninfected syngeneic target cells that were pulsed with synthetic peptides. The sequence of the synthetic peptides was predicted based upon the H-2K(d) binding consensus motif. We show here that preincubation of uninfected syngeneic targets (P388D1) with JEV NS1- and NS3-derived peptides [NS1 (891-899) and NS3 (1804-1812)], but not with JEV NS5-derived peptide [NS5 (3370-3378)], partially sensitized them for lysis by polyclonal anti-JEV CTL. These results indicate the CTL recognition of NS1- and NS3-derived peptides of JEV.

Surface cathepsin B protects cytotoxic lymphocytes from self-destruction after degranulation.

The granule exocytosis cytotoxicity pathway is the major molecular mechanism for cytotoxic T lymphocyte (CTL) and natural killer (NK) cytotoxicity, but the question of how these cytotoxic lymphocytes avoid self-destruction after secreting perforin has remained unresolved. We show that CTL and NK cells die within a few hours if they are triggered to degranulate in the presence of nontoxic thiol cathepsin protease inhibitors. The potent activity of the impermeant, highly cathepsin B-specific membrane inhibitors CA074 and NS-196 strongly implicates extracellular cathepsin B. CTL suicide in the presence of cathepsin inhibitors requires the granule exocytosis cytotoxicity pathway, as it is normal with CTLs from gld mice, but does not occur in CTLs from perforin knockout mice. Flow cytometry shows that CTLs express low to undetectable levels of cathepsin B on their surface before degranulation, with a substantial rapid increase after T cell receptor triggering. Surface cathepsin B eluted from live CTL after degranulation by calcium chelation is the single chain processed form of active cathepsin B. Degranulated CTLs are surface biotinylated by the cathepsin B-specific affinity reagent NS-196, which exclusively labels immunoreactive cathepsin B. These experiments support a model in which granule-derived surface cathepsin B provides self-protection for degranulating cytotoxic lymphocytes.

Glycodelin A suppresses the cytolytic activity of CD8(+) T lymphocytes

Maternal tolerance to the semi-allogenic fetus is brought about by several mechanisms in humans Glycodelin A (GdA) secreted by the uterine mucosa and decidua is induced to high levels by progesterone between 12 and 16 weeks of pregnancy The glycoprotein an immunomodulator has been shown to be inhibitory to the survival and functions of almost all the immune cells CD8(+) T cells which predominate the T lymphocyte population in the decidua are relatively less studied We attempted to find out the possible mechanism if any of regulation of the cytolytic function of CD8(+) T cells during pregnancy Alloactivated CD8(+) T cells harbouring specific cytolytic activity against target cells exhibited compromised activity upon treatment with high concentrations of GdA Interestingly unlike the CD4(+) T cells CD8(+) T cells were resistant to GdA-induced apoptosis The inhibition of cytotoxic T lymphocyte activity was brought about by the downregulation of transcription of the cytolytic effector molecules granzyme B and perform and the degranulation of cytolytic vesicles These results suggest a protective role played by GdA during pregnancy by regulating the cytolytic activity of CD8(+) T cells (C) 2010 Elsevier Ltd All rights reserved

Cytotoxic T lymphocytes raised against Japanese encephalitis virus: effector cell phenotype, target specificity and in vitro virus clearance.

Several H-2 defined cell lines were examined for their ability to support infection and replication of Japanese encephalitis virus (JEV) before their use in in vitro and in vivo stimulation protocols for generating cytotoxic T lymphocytes (CTLs) against JEV. Among II different cell lines tested, two H-2(d) macrophage tumour lines (P388D1, RAW 264.7), an H-2(d) hybridoma (Sp2/0), an H-2K(k)D(d) neuroblastoma (Neuro 2a), and H-2(k) fibroblast cell line (L929) were found to support JEV infection and replication. These cell lines were used to generate anti-JEV CTLs by using in vivo immunization followed by in vitro stimulation of BALB/c mice. We observed that not only syngeneic and allogeneic infected cells but also JEV-infected xenogeneic cells could prime BALB/c mice for the generation of JEV-specific CTLs upon subsequent in vitro stimulation of splenocytes with JEV-infected syngeneic cells. Although infected xenogeneic cells were used for immunization, the anti-JEV effecters that were generated lysed infected syngeneic targets but not JEV-infected xenogeneic or allogeneic target cells in a 5h Cr-51 release assay. These anti-JEV effecters recognized syngeneic target cells infected with West Nile virus to a lesser extent and were shown to be Lyt-2.2(+) T cells. The results of unlabelled cold target competition studies suggested alterations in the cell surface expression of viral antigenic determinants recognized by these CTLs. We further demonstrate that the JEV-specific CTLs generated could virtually block the release of infectious virus particles from infected P388D1 and Neuro 2a cells in vitro.

Protection of adult but not newborn mice against lethal intracerebral challenge with Japanese encephalitis virus by adoptively transferred virus-specific cytotoxic T lymphocytes: Requirement for L3T4(+) T cells

The protective ability of cytotoxic T cells (CTL) raised in vitro against Japanese encephalitis virus (JEV) was examined by adoptive transfer experiments. Adoptive transfer of anti-JEV effecters by intracerebral (i.c.) but not by intraperitoneal (i.p.) or intravenous (i.v.) routes protected adult BALB/c mice against lethal i.c. JEV challenge. In contrast to adult mice, adoptive transfer of anti-JEV effecters into newborn (4-day-old) and suckling (8-14-day-old) mice did not confer protection. However, virus-induced death was delayed in suckling mice compared to newborn mice upon adoptive transfer. The specific reasons for lack of protection in newborn mice are not clear but virus load was found to be higher in newborn mice brains compared to those of adults and virus clearance was observed only in adult mice brains but not in newborn mice brains upon adoptive transfer. Specific depletion of Lyt 2.2(+), L3T4(+) or Thy-1(+) T cell populations before adoptive transfer abrogated the protective ability of transferred effecters. However, when Lyt 2.2(+) cell-depleted and L3T4(+) cell-depleted effecters were mixed and transferred into adult mice the protective activity was retained, demonstrating that both Lyt 2.2(+) and L3T4(+) T cells are necessary to confer protection. Although the presence of L3T4(+) T cells in adoptively transferred effector populations enhanced virus-specific serum neutralizing antibodies, the presence of neutralizing antibodies alone without Lyt 2.2(+) cells was not sufficient to confer protection.

Japanese encephalitis virus infection of mouse cell lines: ability to prime mice for generation of virus specific cytotoxic T lymphocytes and differences in CTL recognisable viral determinants

Ten different mouse cell lines were examined for Japanese encephalitis virus (JEV) infection in vitro and then tested for their ability to generate virus specific cytotoxic T lymphocytes (CTL). Among all cell lines examined, Neuro La (a neuroblastoma) was readily infected with JEV as examined by immunofluorescence and viral replication. Among other cells, P388D1, RAW 264.7 (Macrophage origin), Sp2/0 (B-cell Hybridoma), YAC-1 (T-cell lymphoma), and L929 (Fibroblast) were semipermissive to JEV infection. The cytopathic effects caused by progressive JEV infection varied from cell line to cell line. In the case of YAC-1 cells long-term viral antigen expression was observed without significant alterations in cell viability. Intermediate degrees of cytopathicity are seen in RAW 264.7 and L929 cells while infection of PS, Neuro 2a, P388D1 and Sp2/0 caused major viability losses. All infected cell lines were able to prime adult BALB/c (H-2(d)) mice for the generation of secondary JEV specific CTL. In contrast to YAC-1, the permissive neuroblastoma cell line Neuro 2a (H-2K(k)D(d)) was found to be least efficient in its ability to stimulate anti-viral CTL generation. Cold target competition studies demonstrated that both Neuro 2a and YAC-1 (H-2K(k)D(d)) cells expressed similar viral determinants that are recognised by CTL, suggesting that the reason for the lower ability of Neuro 2a to stimulate anti-viral CTL was not due to lack of viral CTL determinants. These findings demonstrate that a variety of mouse cell lines can be infected with Japanese encephalitis virus, and that these infected cells could be utilised to generate virus specific CTL in BALB/c mice.

In vivo clearance of Japanese encephalitis virus by adoptively transferred virus specific cytotoxic T lymphocytes

Japanese encephalitis virus (JEV) is a positive stranded RNA virus that belongs to the flavivirus group, JEV infection damages the central nervous system (CNS) and is one of the main causative agents of acute encephalitis, H-2 restricted virus-specific cytotoxic T lymphocytes (CTL) have been generated specifically against JEV in our laboratory and these CTL have been shown to protect mice against lethal challenge with JEV, Virus replication was found to be inhibited in the brains of animals that mere adoptively transferred with JEV specific CTL as revealed by immunohistological staining as,veil as viral plaque assays. We further show that virus specific CTL could be recovered from such protected mice as long as 45 days after adoptive transfer.

Glycodelin-A interferes with IL-2/IL-2R signalling to induce cell growth arrest, loss of effector functions and apoptosis in T-lymphocytes

The progesterone-regulated glycoprotein glycodelin-A (GdA), secreted by the decidualized endometrium at high concentrations in primates, inhibits the maternal immune response against fetal antigens and thereby contributes to the tolerance of the semi-allogenic fetus during a normal pregnancy. Our earlier studies demonstrated the ability of GdA to induce an intrinsic apoptotic cascade in CD4 T-lymphocytes and suppress the cytolytic effector function of CD8 T-lymphocytes. In this report, we investigated further into the mechanism of action of GdA controlling perforin and granzyme B expression in CD8 T-lymphocytes and the mechanism of action of GdA leading to lymphocyte death. Flow cytometry analysis was performed to check for the surface expression of interleukin-2 receptor (IL-2R) and intracellular eomesodermin (Eomes) in activated T-lymphocytes, whereas quantitative RTPCR analysis was used to find out their mRNA profile upon GdA treatment. Western analysis was carried out to confirm the protein level of Bax and Bcl-2. GdA reduces the surface expression of the high-affinity IL-2R complex by down-regulating the synthesis of IL-2R (CD25). This disturbs the optimal IL-2 signalling and decreases the Eomes expression, which along with IL-2 directly regulates perforin and granzymes expression. Consequently, the CD8 T-lymphocytes undergo growth arrest and are unable to mature into competent cytotoxic T-lymphocytes. In the CD4 T-lymphocytes, growth factor IL-2 deprivation leads to proliferation inhibition, decreased Bcl-2/enhanced Bax expression, culminating in mitochondrial stress and cell death. GdA spurs cell cycle arrest, loss of effector functions and apoptosis in different T-cell subsets by making T-lymphocytes unable to respond to IL-2.

Alpha-momorcharin inhibits HIV-1 replication in acutely but not chronically infected T-lymphocytes

AIM: To identify the anti-human immunodeficiency virus type 1 (HIV-1) activities of alpha-momorcharin ( alpha-MMC) from Momordica charantia in acutely and chronically infected lymphocytes. METHODS: The anti-HIV activities of alpha-MMC were examined by 1) the inhibition of syncytia formation induced by HIV-1 III B; 2) reduction of p24 core antigen expression level and decrease in numbers of HIV antigen positive cells in acutely and chronically infected cultures. The cytotoxic effects of alpha-MMC was tested by trypan blue dye exclusion or colorimetric MTT assay. RESULTS: alpha-MMC was found to obviously inhibit HIV-1 III B-inducing C8166 syncytia formation and markedly reduced both expression of p24 core antigen and the numbers of HIV antigen positive cells in acutely but not chronically HTV-1-infected culture. The median effective concentration (EC50) in these assays were 0.016, 0.07, and 0.32 mg.L-1, respectively. CONCLUSION: alpha-MMC is a unique component of momorcharin with anti-HIV activity, and markedly inhibited HIV-1 replication in acutely but not chronically HIV-1-infected T-lymphocytes.

Ultrastructural alteration of lymphocytes in spleen and pronephros of grass carp (Ctenopharyngodon idella) experimentally exposed to microcystin-LR

Relatively little is known in relation to pathological changes of immune organs in fish when exposed to MC-LR. The ultrastructural alteration of lymphocytes was examined in the spleen and pronephros of grass carp Ctenopharyngodon idella injected experimentally with microcystin-LR. The fish were intraperitoneally injected with MC-LR at a dose of 50 mu g/kg body weight, and the spleen and pronephros were dissected out at 1, 2, 7, 14 and 21 days post intraperitoneal injection (dpi). Pathological changes were then examined by transmission electron microscopy. Apoptosis was detected only in lymphocytes in the spleen, with obvious apoptotic features observed at 2 dpi; pathological changes of lymphocytes in the pronephros were also serious with mitochondria being highly edematous. However, damaged lymphocytes were almost un-observed in the spleen and pronephros at 21 dpi. These findings suggest that MC-LR can induce toxic effect on immune organs in grass carp, and the spleen may be much more sensitive to MC-LR stimulation. (C) 2008 Elsevier B.V. All rights reserved.