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Biomedical subjects

A B Kulkarni

Publications and source records attributed to A B Kulkarni.

At least 73 records · Page 4Linked to original sources
PubMed1992

Resistance to respiratory syncytial virus (RSV) challenge induced by infection with a vaccinia virus recombinant expressing the RSV M2 protein (Vac-M2) is mediated by CD8+ T cells, while that induced by Vac-F or Vac-G recombinants is mediated by antibodies.

It was previously demonstrated that the vaccinia virus recombinants expressing the respiratory syncytial virus (RSV) F, G, or M2 (also designated as 22K) protein (Vac-F, Vac-G, or Vac-M2, respectively) induced almost complete resistance to RSV challenge in BALB/c mice. In the present study, we sought to identify the humoral and/or cellular mediators of this resistance. Mice were immunized by infection with a single recombinant vaccinia virus and were subsequently given a monoclonal antibody directed against CD4+ or CD8+ T cells or gamma interferon (IFN-gamma) to cause depletion of effector T cells or IFN-gamma, respectively, at the time of RSV challenge (10 days after immunization). Mice immunized with Vac-F or Vac-G were completely or almost completely resistant to RSV challenge after depletion of both CD4+ and CD8+ T cells prior to challenge, indicating that these cells were not required at the time of virus challenge for expression of resistance to RSV infection induced by the recombinants. In contrast, the high level of protection of mice immunized with Vac-M2 was completely abrogated by depletion of CD8+ T cells, whereas depletion of CD4+ T cells or IFN-gamma resulted in intermediate levels of resistance. These results demonstrate that antibodies are sufficient to mediate the resistance to RSV induced by the F and G proteins, whereas the resistance induced by the M2 protein is mediated primarily by CD8+ T cells, with CD4+ T cells and IFN-gamma also contributing to resistance.

Animals↗
PubMed1992

Analysis of murine major histocompatibility complex class II-restricted T-cell responses to the flavivirus Kunjin by using vaccinia virus expression.

The present paper analyzes the influence of major histocompatibility complex (MHC) class II (Ir) genes on MHC class II-restricted T-cell responses to West Nile virus (WNV) and recombinant vaccinia virus-derived Kunjin virus antigens and identifies the immunodominant Kunjin virus antigens. Generally, mice were primed by intravenous infection with WNV or Kunjin virus, and their CD4+ T cells were stimulated in vitro 14 days later with WNV or Kunjin virus antigens to pulse macrophage or B-cell antigen-presenting cells (APC). WNV-specific in vitro T-cell responses from H-2b mice were higher than those from H-2d, H-2k, and H-2q mice. When recombinant vaccinia virus-derived Kunjin virus antigen preparations were tested in vitro, Kunjin virus-immune T cells of H-2b haplotype responded most strongly to structural (prM, C, E) and membrane-associated nonstructural (NS1) proteins encoded by VKV 1031 and showed weaker responses to cytosolic nonstructural protein NS5 (VKV 1022), whereas the responders of H-2k haplotype responded most strongly to the antigens encoded by VKV 1022 and gave lesser responses to VKV 1031. H-2d T cells gave weaker responses than either H-2b or H-2k cells, with responses to VKV 1031 generally being higher than those to VKV 1022. Responses to VKV 1023 or VKV 1024 encoding all of the NS3 to NS5 gene sequence or to VKV 1023 encoding all of NS3 were weak or absent. Within a given inbred strain, B cells and macrophages differed in their abilities to present recombinant vaccinia virus-derived Kunjin virus antigens, both in terms of magnitude of T-cell responses induced and the particular Kunjin virus protein presented. T cells from different non-MHC genetic backgrounds varied in their requirements of macrophage numbers as APC for maximum reactivity, suggesting that the concentration of class II MHC antigens and other molecules affecting APC-T-cell interaction varied in mice with different genetic backgrounds. Regardless of MHC haplotype, responses to VKV 1024, which encompasses VKV 1023 and VKV 1022, were either absent or lower than those to VKV 1022, possibly reflecting differences in the processing requirements of these two proteins. When mice were primed intravenously with recombinant vaccinia virus and when their CD4+ T cells were stimulated in vitro with native Kunjin virus antigens, VKV 1031 primed more efficiently than Kunjin virus and VKV 1022 primed similarly to Kunjin virus.

Animals↗
PubMed1992

Two-way cross-protection between West Nile and Japanese encephalitis viruses in bonnet macaques.

Cross-protection between Japanese encephalitis (JE) and West Nile (WN) viruses was tested in bonnet macaques (Macaca radiata) immunized either with JE virus (JEV) or WN virus (WNV). JEV immunized monkeys were challenged by intranasal (i.n.) route with WNV and vice versa. Four control unimmunized monkeys were similarly infected either with WNV or JEV. Two of three control monkeys infected with WNV, developed paralysis followed by death. Virus was recovered from the central nervous system (CNS) of the both dead control monkeys and the histopathological examination of CNS revealed changes suggestive of viral encephalitis. The control monkey infected with JEV developed encephalitis and the virus was recovered from the blood and CNS. All the 3 JEV-immunized monkeys withstood WNV challenge, whereas only 2 of the 5 WNV immunized monkeys withstood the challenge with JEV. Out of 3 WNV-immunized monkeys surviving challenge with JEV, 2 revealed symptoms suggestive of mild encephalitis followed by complete recovery. The third monkey died on the 60th day post-infection (p.i.) without any symptoms and virus was recovered only from the olfactory lobe. These studies indicate that the immunization with JEV protects the bonnet macaques against WNV, whereas the WNV immunization only reduces the severity of the disease due to JEV.

Animals↗
PubMed1991

Functional analysis of macrophages, B cells and splenic dendritic cells as antigen-presenting cells in West Nile virus-specific murine T lymphocyte proliferation.

In this paper, the relative efficacy of macrophages, B cells and splenic dendritic cells (SDC) in presenting West Nile virus (WNV) antigens to WNV memory CD4+ T cells is examined. The results indicate that, under appropriate conditions, all these cell types can function as antigen-presenting cells (APC). Listeria-induced peritoneal macrophages induced higher proliferative responses than SDC or B cells derived from naive or 14 day WNV-primed mice. The ability of Listeria-induced macrophage populations to present antigen was specifically inhibited by anti-Class II major histocompatibility complex (MHC) antibodies. On a cell population basis, B cells obtained from mice primed with WNV 14 days previously evoked higher responses than resting B cells. B cells from mice receiving weekly injections of WNV over a period of 4 weeks elicited optimal responses with lower doses of antigen than naive or 14 day WNV-primed B cells. When macrophages were used as APC, addition of specific antibodies to WNV resulted in increased efficiency of presentation, probably due to increased uptake of antigen by opsonization. In contrast, addition of anti-WNV antibodies to hyperimmune B cells reduced their efficacy presumably by reducing uptake of antigen by B cell surface immunoglobulin. When SDC from C57BL/6 mice were used as APC, WNV-specific proliferative responses were directly related to the number of stimulator cells used, and the background proliferation with mock antigen was two- to five-fold lower than specific responses. Higher levels of background proliferation were stimulated by SDC from CBA/H mice so that the antigen-specific responses were always less than two-fold higher than background.

Animals↗
PubMed1991

Effect of high ligand concentration on West Nile virus-specific T cell proliferation.

In this paper the phenomenon of suppression of proliferation in vitro of 14 day primed, West Nile Virus (WNV)-specific, murine CD4+ T cells by large numbers of antigen-presenting macrophages and B cells has been investigated. Suppression was apparently not mediated by prostaglandins, as the use of indomethacin in cultures at four times the usual concentration did not reverse suppression. Experiments were designed to evaluate the contribution of major histocompatibility complex (MHC) Class II and nominal WNV antigens in causing suppression of T cell proliferation. Listeria- or thioglycollate-induced macrophages from CBA/H (H-2k) mice, when treated with heat-killed Listeria in vitro for 1 h to maintain or increase, respectively, MHC Class II levels before the addition of alloreactive Iak-specific T cells caused inverse dose-responses; the highest T cell proliferation occurred at a stimulator to responder (S : R) ratio of 0.25 and profound suppression at a S : R ratio of 1 or 2. In contrast, untreated thioglycollate-induced macrophages, which express low MHC Class II levels, gave a direct dose-response with increasing T cell proliferation as antigen-presenting cell (APC) numbers increased. Addition of anti-Ia antibodies (or their Fab fragments) to cultures caused a significant reversal of suppression of anti-WNV T cells imposed by high numbers of Listeria-induced macrophages or 14 day WNV-primed B cell APC. Suppression was also reversed by reducing the concentration of WNV antigen. These observations support the notion that the suppression of T cell proliferation observed at high S : R ratios was due to high concentrations of ligand (WNV-derived peptide complexed with Class II MHC) on APC.

Animals↗
PubMed1991

In vitro T-cell proliferative response to the flavivirus, west Nile.

West Nile virus (WNV)-specific murine T-cell proliferation in vitro was investigated in terms of conditions that optimize antigen-specific responses and reduce background proliferation. The responder populations consisted of splenocytes from WNV-primed mice enriched for L3T4+ T cells. Ia+ antigen-presenting cells (APC) were derived from splenocytes of WNV-primed or naive mice. Antigen was a lysate prepared from WNV-infected Vero cells at 12 h postinfection. Strong virus-specific proliferative responses were observed when antigen-pulsed APC were cocultured with responders at a 1:1 ratio. Substantial nonspecific proliferation occurred when culture medium supplemented with 5% fetal bovine serum (FBS) was used, whereas with 1% normal mouse serum a higher degree of antigen specificity was evident, although the magnitude of the responses was lower. The best separation between antigen-specific and background proliferation was obtained by using an exogenous source of T-cell growth factors to amplify for 2 days the proliferation of L3T4+ cells triggered by an initial 3 days of culture with antigen-pulsed APC. This investigation has defined optimal conditions for investigating the stimulation of WNV-primed L3T4+ T-cell proliferation in response to the presentation of viral gene products by Ia+ APC. This assay should permit detailed analysis of the efficiency of various APC populations and identification of viral antigens that stimulate the proliferation of Class II MHC-restricted T cells.

Animals↗
PubMed1987

Human ribosomal DNA fragments amplified in hamster cells are transcribed only by RNA polymerase II and are not silver stained.

Cloned human rRNA gene fragments that included the promoter region were introduced into Chinese hamster dihydrofolate reductase-deficient (dhfr-) cells by cotransformation with a dhfr minigene and amplified by selection for methotrexate resistance. The human ribosomal DNA was transcribed by RNA polymerase II, not RNA polymerase I or III. The metaphase chromosome regions containing the transcriptionally active human ribosomal DNA failed to show silver staining.

Animals↗
PubMed1985

Acute phase mediators and glucocorticoids elevate alpha 1-acid glycoprotein gene transcription.

Acute phase mediators and glucocorticoids increase the synthesis of the acute phase protein alpha 1-acid glycoprotein, also known as orosomucoid, by inducing the hepatic level of its mRNA. Concurrently the acute phase response depresses the hepatic synthesis of albumin and alpha 2u-globulin and their mRNA levels. Present transcriptional studies in isolated liver nuclei demonstrate that turpentine-induced acute phase mediators simultaneously enhance transcription of the alpha 1-acid glycoprotein gene and diminish transcription of albumin and alpha 2u-globulin genes; parallel alterations in the hepatic level of the corresponding mRNAs ensue. The present transcriptional studies also demonstrate that administration of dexamethasone to adrenalectomized rats dramatically elevates the rate of transcription of the alpha 1-acid glycoprotein gene as well as the alpha 2u-globulin and the albumin genes, leading to elevations in alpha 1-acid glycoprotein and alpha 2u-globulin hepatic mRNA levels. Thus, hepatic alpha 1-acid glycoprotein mRNA levels are predominantly regulated in vivo at the transcriptional level by glucocorticoids as well as by acute phase mediators.

Adrenalectomy↗
PubMed1985

Developmental and hormonal regulation of alpha 2u-globulin gene transcription.

Hepatic alpha 2u-globulin protein and RNA levels are under developmental and complex multihormonal control. The present studies directly evaluate the degree to which this regulation is transcriptional. alpha 2u-Globulin transcription was determined by measuring nuclear runoff RNA in vitro, and tissue alpha 2u-globulin mRNA levels were measured by dot blot hybridization. These studies reveal that (i) in male rats the transcriptional rate of the alpha 2u-globulin genes increases during postnatal development; (ii) no alpha 2u-globulin transcription is detectable in hepatic nuclei derived from hypophysectomized rats; (iii) growth hormone and glucocorticoid are both absolutely required, and glucocorticoid can replace androgen for alpha 2u-globulin gene transcription in the livers of hypophysectomized male rats; and (iv) chronic treatment of mature male rats with estrogen results in a progressive decrease in the hepatic transcription of alpha 2u-globulin genes. In all instances changes in the transcriptional rate of alpha 2u-globulin genes paralleled the tissue level of alpha 2u-globulin RNA. Thus transcriptional control predominates in regulating hepatic alpha 2u-globulin RNA levels.

Age Factors↗
PubMed1984

Differential regulation of alpha 2u globulin gene expression in liver, lachrymal gland, and salivary gland.

The alpha 2u globulins, products of a highly homologous multigene family, are synthesized in the liver and submaxillary salivary glands of the rat. Although their precise function has not been ascertained, they are of interest because of the complex developmental and hormonal regulation of their tissue levels. We now report that alpha 2u globulin is synthesized in a third tissue of the rat, the extraorbital lachrymal gland. Immunocytochemical studies indicate that the distribution of alpha 2u globulin is more homogeneous in the lachrymal gland than in the liver or submaxillary gland. In situ hybridization to alpha 2u globulin RNA reveals specific signal only over the acinar cells of the lachrymal gland. Several different isoelectric forms of alpha 2u globulin are encoded by lachrymal gland mRNA. The major lachrymal and salivary gland isoforms are indistinguishable from one another, but more acidic than the hepatic isoforms. In addition, analysis of double-stranded cDNAs with a diagnostic restriction-enzyme pair detects no differences between the alpha 2u globulin mRNAs of lachrymal and salivary gland, but clearly distinguishes these from their hepatic counterparts. In spite of the similarity between the lachrymal and salivary gland alpha 2u globulin gene products, we find that the hormonal and developmental regulation of alpha 2u globulin expression differs markedly in these two tissues. In the liver, where a different subset of alpha 2u globulin genes is expressed, a third regulatory phenotype is observed.

Alpha-Globulins↗
PubMed1983

Pulmonary superoxide dismutase activity in the mouse infected with Ancylostoma caninum larvae.

Albino mice were infected per os with 1000 infective larvae of Ancylostoma caninum and pulmonary superoxide dismutase activity was studied after completion of lung migration. The total superoxide dismutase activity per mg of lung protein was elevated by 15% in infected mice. Of the two forms of superoxide dismutases studied, that containing Cu-Zn was elevated by 44%. This suggests that A. caninum in mice may result in histopathological changes leading to transient pulmonary oxygen toxicity.

Ancylostomiasis↗
PubMed1983

Effects of early thiamin deficiency and subsequent rehabilitation on the cholinergic system in developing rat brain.

The effects of thiamin deficiency during pregnancy and/or lactation on brain cholinergic system in rat pups were studied. Dietary rehabilitation for a period of 5 weeks from the 28th day was instituted to study possible 'catch-up' in the brain acetylcholine levels. Brain acetylcholine level was found to be significantly decreased on the 21st and 28th days in pups of the dams fed thiamin deficient diet during gestation and lactation, whereas it was decreased on the 28th day in pups of the dams fed thiamin deficient diet during lactation. Activities of cholinergic enzymes remained unaltered in both the deficient groups. Subsequent dietary rehabilitation was found to reverse the deficits in brain acetylcholine levels.

Acetylcholine↗