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L Hyland

Publications and source records attributed to L Hyland.

At least 19 recordsLinked to original sources
PubMed2001

Nasal-associated lymphoid tissue is a site of long-term virus-specific antibody production following respiratory virus infection of mice.

Nasal immunoglobulin A provides an initial defense against inhaled respiratory pathogens. However, it is not known whether the nasal-associated lymphoid tissues (NALT) are able to mount an effective long-lasting pathogen-specific immune response, nor is it known whether functional differences exist between the organized NALT (O-NALT) and the diffuse NALT lining the nasal passages (D-NALT). Here we show that although both the O-NALT and the D-NALT are capable of producing virus-specific antibody in response to influenza virus infection, the frequency of specific antibody-forming cells in the D-NALT is much greater than the frequency observed in the O-NALT. Furthermore, we show that the D-NALT but not the O-NALT is the site of long-term virus-specific humoral immunity which lasts for the life of the animal. These results indicate that the D-NALT is not only the major effector site of the NALT but also the site of local long-term specific antibody production.

Animals↗
PubMed1999

Constitutive expression of interleukin 4 in vivo does not lead to the development of T helper 2 type CD8+ T cells secreting interleukin 4 or interleukin 5.

Interleukin 4 (IL-4) has been shown to commit CD8+ T cells to a T helper (Th) 2 functional phenotype in vitro. To study the effects of IL-4 on CD8+ T cell development in vivo we analysed the CD8+ T cell phenotype in mice constitutively expressing IL-4. Purified CD8+ T cells from uninfected or flu infected IL-4 transgenic (tg) animals produced no detectable IL-4 or IL-5 after in vitro stimulation on anti-CD3 coated plates. However, CD8+ T cells from IL-4 tg mice could be converted into IL-4 and IL-5 producers in vitro in the presence of exogenous added IL-4, showing that these cells were still responsive to IL-4. IL-4 tg mice also showed a delay in influenza virus clearance from the lung, which was probably due to the observed reduction of total CD8+ T cell numbers in the IL-4 tg animals since IL-4 tg CD8+ T cells showed normal levels of influenza-specific cytotoxicity in comparison to controls. Taken together these results suggest that CD8+ T cells are not necessarily switched to a Th2 phenotype by the presence of IL-4 and that some other factor(s) may be important in the switch process of CD8+ T cells in vivo, since the addition of IL-4 during CD8+ T cell activation in vitro leads to Th2 type CD8+ T cells secreting IL-4 and IL-5.

Animals↗
PubMed1995

Subverting lymph node trafficking by treatment with the Mel-14 monoclonal antibody to L-selectin does not prevent an effective host response to Sendai virus.

A single 250-micrograms dose of the Mel-14 mAb to L-selectin greatly diminished the extent of L-selectin expression on lymphocytes and decreased (60 to 90%) the massive cellular recruitment to the cervical and mediastinal lymph nodes that follows intranasal infection of naive C57BL/6 mice with Sendai virus. The numbers of CD8+ CTL precursors in the mediastinal lymph nodes were considerably reduced on day 7, when compared with virus-infected mice given a control rat IgG2a, but potent CTL effectors were present in the lungs of both groups by day 10 after infection, and the overall magnitude of CTL precursor generation was not obviously compromised. The early dominance of Sendai virus-specific IgM Ab-forming cells was prolonged in the Mel-14-treated mice, whereas plasma cells producing virus-specific IgA were abnormally prominent in the lymph nodes but not in the spleen. The kinetics of virus-specific Ab-forming cells generation and the serum Ab response for the various IgG isotypes were also delayed. Thus, though L-selectin is clearly important for the localization of naive lymphocytes to regional lymph nodes, the Mel-14-treated mouse can still deal effectively with a virus that causes productive infection only in the respiratory tract. The spleen, where L-selectin does not determine lymphocyte trafficking, is a major site for the compensatory T cell and B cell responses.

Animals↗
PubMed1995

Distinctive kinetics of the antibody-forming cell response to Sendai virus infection of mice in different anatomical compartments.

The single-cell ELISPOT assay was used to determine the frequency and isotype commitment of virus-specific antibody-forming cells (AFC) at different anatomical locations following intranasal Sendai virus infection of C57BL/6 and 129/Sv mice. AFC responses in the mediastinal and cervical lymph nodes showed sharp increases and declines, first of IgM AFC, peaking about 7 days after infection, and then of IgG and IgA AFC, peaking about 10 days after infection. A wave of IgM AFC preceding the other isotypes was less evident in the spleen, where peak frequencies of AFC occurred 14 days after infection. Virus-specific AFC appeared in the bone marrow with a unique kinetic pattern, increasing in frequency gradually over the first 3 weeks after infection to a plateau that remained constant. Circulating IgM and IgG achieved significant titers approximately a week after infection; IgM titers were transient, but IgG levels increased sharply and remained high, reflecting the longevity of the bone marrow AFC response. Strain differences in isotype bias were noted, particularly preferential switching to the gamma 2a gene in 129/Sv mice. The B-cell response to acute respiratory viral infection thus exhibits features that are distinct from the primary response to nonreplicating antigens.

Animals↗
PubMed1995

Host response to Sendai virus in mice lacking class II major histocompatibility complex glycoproteins.

The development of Sendai virus-specific cytotoxic T-lymphocyte (CTL) effectors and precursors (CTLp) has been compared for mice that are homozygous (-/-) for a disruption of the H-2I-Ab class II major histocompatibility complex glycoprotein and for normal (+/+) controls. The generation of CD8+ CTLp was not diminished in the -/- mice, though they failed to make virus-specific immunoglobulin G class antibodies. While the cellularity of the regional lymph nodes was decreased, the inflammatory process assayed by bronchoalveolar lavage (BAL) of the pneumonic lung was not modified, and potent CTL effectors were present in BAL populations recovered from both groups at day 10 after infection. There was little effect on virus clearance. Production of interleukin-2 by both freshly isolated BAL inflammatory cells and cultured lymph node cells was greatly diminished, though the -/- mice still made substantial levels of gamma interferon. However, treating the mice with a single dose of a monoclonal antibody to this cytokine, at least some of which is made by CD8+ T cells, did not decrease CTLp frequencies. As found previously with CD4-depleted H-2b mice, the development of Sendai virus-specific CD8+ T-cell-mediated immunity is not compromised by the absence of a concurrent class II major histocompatibility complex-restricted response.

Animals↗
PubMed1994

Virus-specific CD8+ T-cell memory determined by clonal burst size.

Although some viruses, particularly the herpes viruses, may never be eliminated from the body, others like influenza A, regularly reinfect humans and boost waning crossreactive CD8+ T-cell immunity. Prolonged T-cell memory is found for viruses that are unlikely to be re-encountered and which do not persist in the host genome, indicating that CD8+ T-cell memory might be independent of continued (or sporadic) antigenic exposure. A feature of virus-specific CD8+ T-cell memory is that antigen-specific cytotoxic T-lymphocyte precursors (CTLp) are greatly increased and remain high throughout life. The idea that persistence of the inducing antigen is essential is based on experiments in which adoptively transferred CD8+ memory T cells could not be detected for more than a few weeks in naive recipient mice without secondary challenge. Here we show that restimulation of such chimaeric mice with an inducing Sendai virus antigen increases the clonal burst size more than 7-fold within 8 days, making memory CTLp easier to detect in the longer term. We find that Sendai-virus-specific CTLp are maintained for > 250 days in irradiated uninfected recipients, including reconstituted beta 2-microglobulin-/- mice. To determine whether a source of viral peptide can persist after primary infection, we gave Sendai-virus-specific Thy1.1+ memory spleen cells to naive mice that had been minimally depleted of Thy1.2+ T cells, or to comparable recipients that had recovered from infection with Sendai virus or influenza virus. Although antibody against Sendai virus was never found in the naive recipients, Sendai-virus-specific CD8+ memory T cells were maintained equally well in each case for > 100 days after cell transfer. We find no evidence for persisting depots of viral protein that might feed into the endogenous processing pathway and maintain virus-specific CD8+ T-cell memory.

Animals↗
PubMed1994

Mice lacking CD8+ T cells develop greater numbers of IgA-producing cells in response to a respiratory virus infection.

Antibody production profiles have been compared for Sendai virus infection of normal mice and mice that lack CD8+ T cells as a consequence of treatment with a lymphocyte subset-specific monoclonal antibody or homozygous disruption of the beta 2-microglobulin (beta 2-m(-/-)) gene encoding the light chain of the class I major histocompatibility complex glycoprotein. Using the single-cell ELISPOT assay, we show a relative increase in IgA antibody forming cell (AFC) numbers in the mediastinal lymph node (MLN), spleen, and bone marrow of the CD8-depleted mice. This is reflected in higher serum IgA titers. Similarly, secondary infection with a large dose of Sendai virus leads to greater prevalence of virus-specific IgA AFCs as early as Day 5 postinfection in the beta 2-m(-/-) mice. Also, in primed beta 2-m(-/-) mice challenged with vaccinia constructs containing the genes for the hemagglutinin-neuraminidase (HN), nuclear protein, or the fusion protein of Sendai virus, the majority of the virus-specific AFCs in the MLN are specific for HN and secrete IgA.

Animals↗
PubMed1994

Respiratory virus infection of mice provokes a permanent humoral immune response.

We have observed that respiratory virus infection of mice provokes an extremely persistent humoral immune reaction, due to a long-sustained population of antibody-secreting cells in the bone marrow. Theories of humoral immunity that strongly distinguish primary and secondary reactions thus may not adequately describe the immune response to respiratory viruses.

Animals↗
PubMed1994

Use of high efficacy, lower dose triple therapy to reduce side effects of eradicating Helicobacter pylori.

OBJECTIVES: To evaluate two triple-therapy (TT) regimens of colloidal bismuth subcitrate (CBS), metronidazole, and tetracycline HCl in eradicating Helicobacter pylori, with particular attention to the frequency of resulting adverse effects of the two therapies. METHODS: A prospective, randomized controlled trial was conducted in patients with symptoms of dyspepsia who were positive for H. pylori. Subjects received a 14-day course of either 4 x/day therapy of CBS (108 mg), tetracycline HCl (500 mg), and metronidazole (250 mg), or 5 x/day therapy of CBS (108 mg), tetracycline HCl (250 mg), and metronidazole (200 mg). H. pylori status was determined endoscopically by urease test, histology, and culture. Standard questionnaires were administered to determine compliance to treatment and side effects of therapy. RESULTS: H. pylori was eradicated in 196/213 (92%) patients in the 4 x/day group and 202/210 (96%) in the 5 x/day group (p = 0.07). Side effects were significantly less frequent and less severe in the 5 x/day group (p < 0.01). CONCLUSIONS: We conclude that a lower dose, 5 x/day triple therapy treatment of H. pylori is equally efficacious to the standard 4 x/day therapy, but is accompanied by fewer and milder adverse effects.

Abdominal Pain↗
PubMed1991

Helicobacter pylori-negative duodenal ulcer.

Most patients with chronic duodenal ulcer (DU) craters have gastritis associated with Helicobacter pylori (HP), now thought to be the major cause of DU. A smaller proportion of DU patients have no detectable HP. In this study, we examined the frequency and causes of HP-negative duodenal ulcers. In 302 consecutive patients with endoscopic diagnosis of duodenal ulcer, 284 (94%) were found to have associated HP gastritis, whereas 18 (6%) were HP-negative on histology, culture, and urease test. The largest subgroup of HP-negative patients (8/18) was made up of those who had been taking nonsteroidal antiinflammatory drugs (NSAIDs), followed closely (4/18) by patients with recent intake of antibiotics. Causes of DU in the remaining subgroups included two patients with duodenal Crohn's disease, two with Gastrospirillum hominis infection, one with penetrating carcinoma of the pancreas and one with no detectable cause. We conclude that, although the most common causal factor of duodenal ulcer is HP, some 6% of DU's will be HP-negative, signaling unusual etiology. It is now important to identify the cause of duodenal ulcer so as to initiate appropriate therapy.

Adult↗
PubMed1989

Recurrence of duodenal ulcer and Campylobacter pylori infection after eradication.

The role of Campylobacter pylori gastritis in dyspepsia could be clarified more readily if reliable eradication therapy were available. Antibiotic monotherapy and combined therapy with an antibiotic agent plus a bismuth compound have yielded poor long-term results. In this study, bismuth-tetracycline-metronidazole triple therapy has been used to eradicate C. pylori infection in 100 consecutive patients who were suffering from either a duodenal ulcer or non-ulcer dyspepsia. Examination of a follow-up endoscopic biopsy at eight weeks after treatment showed an eradication rate of C. pylori of 94%. Of 64 patients whose biopsy samples were free of C. pylori infection at eight weeks and who were available for reassessment, 60 (94%) patients had samples that remained free of C. pylori infection on examination of a repeat endoscopic biopsy at 12-37 months (mean, 19.3 months). It is concluded that "triple chemotherapy" can achieve long-term eradication of C. pylori infection effectively in the majority of treated patients and that the recurrence of duodenal ulcers thus may be diminished.

Administration, Oral↗
PubMed1989

Peptide substrates and inhibitors of the HIV-1 protease.

Oligopeptides containing the consensus retroviral protease cleavage sequence Ser/Thr-X-Y-Tyr/Phe-Pro are substrates for purified recombinant HIV-1 protease with Km's in the millimolar range. The minimum sequence containing the consensus pentapeptide which serves as a good substrate is a heptapeptide spanning the P4-P3' residues. Substitution of reduced Phe-Pro or Tyr-Pro dipeptide isosteres or the statine analog 3-hydroxy-4-amino-5-phenylpentanoic acid for the scissile dipeptide afforded inhibitors of HIV-1 protease with Ki values in the micromolar range, three orders of magnitude better in affinity than the corresponding substrates. Inhibitors of HIV-1 protease may provide a novel and potentially useful therapeutic approach to the treatment of acquired immune deficiency syndrome (AIDS).

Amino Acid Sequence↗
PubMed1989

Inhibition of human immunodeficiency virus 1 protease in vitro: rational design of substrate analogue inhibitors.

Inhibitors of the protease from human immunodeficiency virus 1 (HIV-1) were designed, synthesized, and kinetically characterized. Analogues of a heptapeptide substrate of HIV-1 protease with sequence similar to the p17-p24 cleavage site in the natural substrate, Pr55gag, were synthesized in which the scissile dipeptide bond was replaced with bonds from six categories of stable mimics of an aspartic proteolysis transition state or intermediate. These mimics included an analogue of statine, hydroxyethylene isosteres, two categories of phosphinic acids, a reduced amide isostere, and an alpha,alpha-difluoroketone. The resulting peptide analogues were linear competitive inhibitors of purified recombinant HIV-1 protease with inhibition constants ranging from 18 nM to 40 microM depending on the type of inhibitor. A truncated inhibitor, an analogue of a hexapeptide, retained full inhibitory potency. The most potent inhibitors, containing the hydroxyethylene isostere, effectively blocked the proteolytic processing of a recombinant form of Pr55gag by HIV-1 protease in a cell-free assay.

Amino Acid Sequence↗
PubMed1987

Age-related alterations in alpha 1- and beta-adrenoceptors mediated responsiveness of rat aorta.

We have examined the responsiveness of alpha- and beta-adrenoceptors in aortae from 1.5, 3, 6 and 24 month old rats. The isometric contraction to phenylephrine was antagonised competitively by prazosin with a pA2 value of 9.45, suggesting that the receptor is an alpha 1-adrenoceptor. The potency of phenylephrine was significantly reduced in 24 months old as compared with all younger rats combined. The maximum contraction to phenylephrine was unaltered in 24 month old rats. The maximum contraction to potassium chloride was significantly less than that to phenylephrine only in 1.5 months old rats. In tissues contracted by potassium chloride, isoprenaline produced a marked relaxation in 1.5 months old animals, but there was a progressive loss with increasing age of the beta-adrenoceptor-mediated relaxation which was markedly reduced by 6 months and abolished in 24 months old. It is concluded that, in the rat aorta, there is a decrease in alpha 1-adrenoceptor responsiveness in senescence, and a loss of beta-adrenoceptor-mediated responses in maturation.

Aging↗
PubMed1986

Alpha-adrenoceptor responsiveness in the aged rat.

The effects of ageing on vascular alpha 1- and alpha 2-adrenoceptors were examined using anaesthetised and pithed young (3-7 months) and old (21-24 months) Sprague-Dawley rats. In pithed animals, the pressor and cardioinhibitory effects of the alpha 2-adrenoceptor agonist xylazine were significantly reduced in old animals (8- and 6-fold shift), but the pressor effects of the alpha 1-adrenoceptor agonist amidephrine were not significantly altered by ageing. In anaesthetised rats, the pressor response to the mixed alpha-adrenoceptor agonist noradrenaline (NA) was not significantly altered, and the pressor potency of the alpha 1-adrenoceptor agonist amidephrine was only slightly reduced (1.7-fold shift) in old animals. In the presence of cocaine (1 mg kg-1) the pressor potency of NA was markedly reduced (13-fold shift) in old animals. In the presence of prazosin (1 mg kg-1) to eliminate alpha 1-adrenoceptor-mediated responses, the pressor potency of NA was markedly reduced in old as animals as compared to young animals (16-fold shift). The neuronal uptake blocker cocaine (1 mg kg-1) significantly potentiated the pressor response to NA only in young. In summary, we have found a reduced alpha 2-adrenoceptor-mediated pressor and cardioinhibitory responsiveness and a reduced neuronal uptake of NA in old animals with little change in alpha 1-adrenoceptor-mediated vascular responsiveness.

Aging↗
PubMed1986

An examination of 5-hydroxytryptamine receptors in human saphenous vein.

We have examined the effects of antagonists on the isometric contraction of the human saphenous vein produced by 5-hydroxytryptamine (5-HT). The 5-HT2-antagonist ketanserin (1 microM) had little effect on the lower part of the concentration-response curve to 5-HT, but markedly shifted the upper part of the curve. Yohimbine caused an approximately parallel shift of the concentration-response curve to 5-HT, with a pA2 of 5.48, much lower than its pA2 against noradrenaline in the absence (6.36) or presence (7.06) of cocaine. It is concluded that there are two components to the contractile response to 5-HT in human saphenous vein: at low concentrations 5-HT activates a yohimbine-sensitive receptor, and at higher concentrations 5-HT activates a 5-HT2-receptor.

Adult↗
PubMed1985

An investigation of age-related changes in pre- and postjunctional alpha-adrenoceptors in human saphenous vein.

The responsiveness of prejunctional alpha 2-, postjunctional alpha 1- and postjunctional alpha 2-adrenoceptors was examined in human isolated saphenous veins from male patients in the age range 37-70. There was no age-related alteration in the prejunctional potency of the alpha 2-adrenoceptor agonist xylazine for inhibiting the stimulation-evoked overflow of tritium in tissues preincubated with [3H]noradrenaline. The alpha 2-adrenoceptor antagonist yohimbine (0.01-1 microM) and the alpha 1-adrenoceptor antagonist prazosin (0.1-1 microM) significantly reduced stimulation-evoked contractions in a concentration-dependent manner. There was no significant age-related correlation for the potency of prazosin but there was a significant negative correlation between the potency of yohimbine and age (r = 0.70, n = 11, P less than 0.05), i.e. the potency of yohimbine decreased with increasing age. The decreased postjunctional potency of yohimbine may reflect a loss of alpha 2-adrenoceptors with increasing age.

Adult↗