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Biomedical subjects

H Kita

Publications and source records attributed to H Kita.

At least 91 records · Page 5Linked to original sources
PubMed1998

Time window for the contribution of the delta-opioid receptor to cardioprotection by ischemic preconditioning in the rat heart.

The present study aimed to examine (1) whether the role of the opioid receptor in ischemic preconditioning (PC) is consistent regardless of the duration of ischemic insult and (2) which opioid receptor subtype contributes to PC. In the first series of experiments, the effects of PC, a nonselective opioid receptor antagonist (naloxone), and their combination on the infarct size after various durations of ischemia were assessed. In anesthetized, open-chest rats, the coronary artery was occluded for 20, 30, or 40 minutes to induce infarction and was reperfused for 3 hours, PC was performed with two cycles of 5-minute ischemia followed by 5-minute reperfusion before the sustained ischemia. At 25 minutes before the ischemia, naloxone was injected alone or in combination with subsequent PC. Infarct size was determined by tetrazolium staining and was expressed as a percentage of the risk area size (%IS/RA). In the second series of experiments, the effects of a delta-receptor-selective antagonist, naltrindole (NTI), and a kappa-receptor selective antagonist, nor-binaltrophimine (nor-BNI), on PC before 30-minute coronary occlusion were assessed. In untreated controls, %IS/RA was 53.1 +/- 3.2 after 20 minutes, 67.9 +/- 3.9 after 30 minutes, and 87.8 +/- 2.0 after 40 minutes of ischemia, respectively. PC significantly reduced %IS/RA after 20, 30, and 40 minutes of ischemia to 3.1 +/- 0.8, 12.8 +/- 1.1, and 42.1 +/- 4.3, respectively (P < 0.05 vs. each control). Naloxone (6 mg/kg) partially attenuated the protection afforded by PC when the sustained ischemia was 30 minutes (%IS/RA = 27.4 +/- 4.5; P < 0.05 vs. PC), but this inhibitory effect of naloxone was not detected when the duration of the ischemia was 20 or 40 minutes. NTI (10 mg/kg) also attenuated infarct size limitation by PC after 30 minutes of ischemia (%IS/RA = 25.6 +/- 3.7), but nor-BNI (10 mg/kg) failed to modify infarct size limitation by PC (%IS/RA = 13.3 +/- 3.2). The present results suggest that activation of the opioid delta-receptor partly contributes to preconditioning against infarction in the rat and that there may be a time window (at around 30 minutes after the onset of ischemia) for this opioid receptor-mediated protective mechanism.

Animals↗
PubMed1998

Inhibition of interleukin-5 mediated eosinophil viability by fluticasone 17-propionate: comparison with other glucocorticoids.

BACKGROUND: Inhaled glucocorticoids are commonly employed to treat patients with asthma. Eosinophils are important effector cells in the pathogenesis of asthma, and, in vitro, glucocorticoids modulate eosinophil viability. OBJECTIVE: Using this glucocorticoid inhibition of eosinophil viability, we compared the in vitro potencies of several inhaled glucocorticoids with particular attention to fluticasone 17-propionate. METHODS: Eosinophils from normal or mildly atopic donors were purified, cultured with cytokines and glucocorticoids, and on day 4, after staining with propidium iodide, analysed by flow cytometry. RESULTS: Eosinophil viability was prolonged by interleukin (IL)-5 in a concentration-dependent manner; in contrast, dexamethasone inhibited the IL-5 effect. Fluticasone 17-propionate, 1.0-1000 nM, also inhibited the IL-5 effect in a concentration-dependent manner; interestingly, at 0.1 nM fluticasone 17-propionate modestly, but significantly, enhanced eosinophil survival. High concentrations of IL-5 and granulocyte-macrophage colony-stimulating factor essentially completely overcame the inhibitory effect of 1000 nM fluticasone 17-propionate on eosinophil survival. In contrast, although interferon-gamma-mediated eosinophil viability was inhibited by 1.0-1000 nM fluticasone 17-propionate, this inhibition was not overcome by increased concentrations of interferon-gamma. Comparison of the glucocorticoid inhibition of eosinophil viability in the presence of 10 pg/mL IL-5 resulted in these drug IC50 values (in nM): fluticasone 17-propionate, 1.3; budesonide, 8.5; triamcinolone acetonide, 25; flunisolide, 32; dexamethasone, 94; beclomethasone 17-monopropionate, 210; beclomethasone 17,21-dipropionate, 290; and hydrocortisone, >1000. CONCLUSION: Fluticasone 17-propionate's effect on cytokine-mediated eosinophil viability is similar qualitatively to other glucocorticoid preparations. However, quantitatively, fluticasone 17-propionate has the most potent suppressive effects on IL-5 mediated eosinophil viability among the currently available inhaled glucocorticoids in the United States.

Administration, Inhalation↗
PubMed1998

The nocturnal secretion of cardiac natriuretic peptides during obstructive sleep apnoea and its response to therapy with nasal continuous positive airway pressure.

The nocturnal secretion profile of the newly identified natriuretic peptide (NP), brain natriuretic peptide (BNP), was studied in 14 patients with obstructive sleep apnoea syndrome (OSAS) (apnoea hypopnoea index: 60.5 +/- 3.4, mean +/- SE) during two separate nights before and during nasal continuous positive airway pressure (NCPAP) therapy. Plasma levels of NPs (atrial natriuretic peptides; ANP and BNP) were measured at 2-h intervals during sleep. Simultaneously, blood pressure was measured by a non-invasive method (Finapres, Ohmeda, Englewood, CO, USA) and urine was collected for determining volume and catecholamine levels. Urinary and serum sodium concentration were determined before and after the study. Eight non-snoring subjects were also studied for the investigation of normal nocturnal profiles of BNP levels. To understand the discrete secretion profiles of the two NPs during sleep, blood was sampled from an additional seven patients every 5 min over a 30-min period around 00.00 and 04.00 hours before NCPAP. In patients with OSAS, plasma BNP levels increased from the beginning of sleep (22:00 h) to the morning (06:00 h) before NCPAP therapy (P < 0.01, ANOVA). Baseline BNP levels were not significantly correlated with patient's clinical and polysomnographic parameters. However, in the latter half of the sleep period (02:00-06:00 h), increases in BNP levels during the night before NCPAP therapy were significantly correlated with blood pressure elevations (systolic: r = 0.784 P < 0.01, diastolic: r = 0.587 P < 0.01) and with apnoea duration (r = 0.582 P < 0.01). In normal subjects BP and BNP levels were not changed significantly during sleep. Plasma BNP levels were well correlated with concomitant ANP levels (P < 0.001). NCPAP therapy reduced ANP and BNP levels during sleep and in the morning (P < 0.01). Plasma levels of BNP at 5 min intervals before NCPAP therapy revealed few variations. On the other hand, ANP levels fluctuated over the 30-min period. Changes in BNP levels during sleep in the patients with OSAS may be related to blood pressure variations, but may be too small to play a significant physiological role in regulating diuresis in OSAS. Further work is required to determine the precise role of dual natriuretic system in cardiovascular load and natriuresis in OSAS.

Atrial Natriuretic Factor↗
PubMed1998

Improvement of factor VII clotting activity following long-term NCPAP treatment in obstructive sleep apnoea syndrome.

Obstructive sleep apnoea syndrome (OSAS) is a very common disorder. Patients with OSAS are at an increased risk for cardiovascular events. It has also been reported that a 25% rise in factor VII clotting activity (FVIIc) is associated with a 55% increase in ischaemic heart disease death during the first 5 years. We examined the effects of nasal continuous positive airway pressure (NCPAP) treatment on FVIIc in patients with OSAS. FVIIc was investigated prospectively in 15 patients with OSAS before (mean +/- SEM apnoea and hypopnoea index (AHI) 61.5 +/- 4.2 and after (AHI 3.0 +/- 0.9) NCPAP treatment for immediate relief, at 1 month after treatment and at over 6 months. FVIIc levels gradually decreased after NCPAP treatment. After 6 months of NCPAP treatment, FVIIc levels had decreased significantly (before 141.1 +/- 11.7% vs. after 6 months 110.7 +/- 6.2%; p < 0.01). Six of the seven patients whose FVIIc levels were over 140% before the NCPAP treatment had FVIIc levels below 130% after 6 months or 1 year of NCPAP treatment. This decrease in FVIIc after long-term NCPAP treatment could improve mortality in OSAS patients. If patients, especially obese ones, present with high FVIIc of unknown origin, it would be prudent to check for OSAS.

Adult↗
PubMed1998

Suppression of reperfusion arrhythmias by preconditioning is inhibited by an ATP-sensitive potassium channel blocker, 5-hydroxydecanoate, but not by protein kinase C blockers in the rat.

It has been suggested that preconditioning (PC) against infarction in the rat heart is mediated by opening of ATP-sensitive potassium (KATP) channels, which may be induced by receptor-triggered activation of protein kinase C (PKC). However, the mechanism of suppression of reperfusion arrhythmias by PC remains unclear. This study first examined whether suppression of reperfusion arrhythmias by PC requires the activation of KATP channels, PKC, and opioid receptors. In anesthetized rats, reperfusion arrhythmias were induced by occluding the left main coronary artery for 5 min and subsequent reperfusion. In untreated control rats, the incidence of reperfusion ventricular tachycardia (VT) was 100%, and 80% of the VT deteriorated to ventricular fibrillation (VF). PC with 2-min ischemia/5-min reperfusion reduced the incidences of VT and VF to 30% and 0, respectively. Although a KATP channel blocker, 5-hydroxydecanoate (5-HD), alone caused no significant effect on the incidence of reperfusion VT, this agent blocked the suppression of reperfusion VT by PC (VT incidence, 91%). The incidence of reperfusion VF in the 5-HD-treated rats tended to be lower than that in the untreated controls and was not different between preconditioned and nonpreconditioned groups (30 vs. 27%). PKC inhibitors staurosporine and calphostin C modified neither reperfusion arrhythmias nor the antiarrhythmic effect of PC on reperfusion VT and VF. Naloxone (6 mg/kg, i.v.) did not alter the incidence or duration of VT in the nonpreconditioned heart. However, suppression of reperfusion VT by PC was prevented by naloxone (VT incidence, 70%). The incidence of reperfusion VF was similarly low in the naloxone-treated rats in both nonpreconditioned and preconditioned groups (20% vs. 0). In the second series of experiments, the effect of 5-HD on repetitive PC was assessed. Repetitive PC was performed with three cycles of 2-min ischemia/5-min reperfusion, which totally abolished reperfusion VT and VF. This antiarrhythmic effect of repetitive PC was not inhibited by 5-HD. These results suggest that KATP channels and opioid receptors may be partly involved in suppression of reperfusion arrhythmias, although their roles may be compensated for by other antiarrhythmic mechanisms in repetitive PC. In contrast with PC against infarction, PKC is unlikely to play a major role in PC against reperfusion arrhythmias in the rat.

Adenosine Triphosphate↗
PubMed1998

Signal transduction in activation of human eosinophils: G protein-dependent and -independent pathways.

Degranulation of eosinophils and subsequent release of toxic granule proteins play a key role in allergic diseases such as bronchial asthma. We have previously shown that stimulation of eosinophils with immobilized secretory immunoglobulin A (sIgA) induced the phosphorylation of several proteins including 51-, 65-, 73-, 78-, 100-, 105- and 113-kD proteins. Pervanadate, a protein tyrosine phosphatase inhibitor, also induced at least 7 tyrosine phosphorylated proteins including those observed with immobilized sIgA. Pervanadate also induced inositol phosphate (IP) production and degranulation of eosinophils in a concentration-dependent manner. Eosinophil production of IP and degranulation as well as tyrosine phosphorylation of proteins induced by sIgA were completely inhibited by a tyrosine kinase inhibitor, genistein, and pertussis toxin (PTX), suggesting the involvement of both the PTX-sensitive guanine nucleotide-binding (G) protein and protein tyrosine kinases (PTK) in sIgA-induced activation of eosinophils. In contrast, PTX did not affect tyrosine phosphorylation induced by sIgA or pervanadate. Furthermore, pervanadate-induced IP production was partially inhibited by PTX. Finally, a phospholipase C-gamma2 isoform was tyrosine phosphorylated by pervanadate, but not by sIgA. These findings suggest that at least two different pathways, i.e. PTK-mediated G protein-dependent or -independent PLC activation, are involved in the activation of human eosinophils.

Asthma↗
PubMed1998

Cross-linking of the beta2 integrin, CD11b/CD18, on human eosinophils induces protein tyrosine phosphorylation and cellular degranulation.

Adhesion molecules, including integrins, play an important role in the selective recruitment of eosinophils. It has recently been shown that integrins also modulate the functions of eosinophils. Here, we tested the hypothesis that cross-linking of the beta2 integrin, alphaMbeta2Mac-/, leads to intracellular signaling events such as activation of protein tyrosine kinases leading to eosinophil degranulation. Cross-of cell surface CD11b/with anti-tibody and goat anti-G immobilized onto the plate triggered tyrosine phosphorylation of several intracellular proteins, including the one with a 115-kD mass (pp115). The same stimulus also provoked degranulation of eosinophils. These findings suggest that engagement of beta2 integrin on eosinophils triggers the activation of intracellular signaling cascade which leads to cellular degranulation.

Antibodies↗
PubMed1998

Ligation of the beta2 integrin triggers activation and degranulation of human eosinophils.

Evidence suggests that cellular adhesion is critical for eosinophil effector functions. Here, we tested the hypothesis that an adhesion molecule, specifically beta2 integrin, participates in intracellular signaling events of eosinophils. Eosinophils stimulated with interleukin (IL)-5 and adherent to protein-coated tissue culture plates via beta2 integrin (CD18) showed tyrosine phosphorylation of a number of proteins. Among these proteins, tyrosine phosphorylation of the 105 kD and 115 kD proteins and the product of the c-cbl protooncogene, Cbl, was specifically inhibited using soluble anti-CD18 monoclonal antibody (mAb) to block eosinophil cell adhesion. Furthermore, phosphoinositide turnover of IL-5-stimulated adherent eosinophils was also inhibited by anti-CD18 mAb, suggesting that cellular adhesion plays important roles in eosinophil signal transduction. alphaM beta2 (Mac-1, CD11b/18) was one of the beta2 integrins involved in eosinophil adhesion to protein-coated plates. We found that direct ligation of eosinophil alphaM beta2 with anti-CD11b mAb coupled to polystyrene microbeads induced tyrosine phosphorylation of a 115 kD protein and Cbl. Furthermore, anti-CD11b mAb microbeads induced increases in both phosphoinositide hydrolysis and the eosinophil degranulation response. Control antibodies, such as mouse myeloma IgG1 and anti-HLA class I antigen mAb, did not induce these cellular responses. These results suggest that engagement of beta2 integrin either by cell adhesion or by anti-CD11b mAb triggers activation of an intracellular signaling cascade, including protein tyrosine phosphorylation and phosphoinositide turnover, and subsequent cellular degranulation in human eosinophils. Tyrosine phosphorylation of a 115 kD protein and Cbl may play important roles in adhesion-dependent cellular functions of eosinophils.

Antibodies, Monoclonal↗
PubMed1998

Granulocyte macrophage colony-stimulating factor augments ICAM-1 and VCAM-1 activation of eosinophil function.

Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) are members of the immunoglobulin superfamily adhesion molecules on vascular endothelium and important in the development of eosinophil (EOS) accumulation in allergic inflammation. To define the role of these adhesion proteins in EOS inflammation, peripheral blood EOS from allergic donors were incubated in either buffer (control)-, recombinant human (rh)-VCAM-1-, or rh-ICAM-1-coated plates, and the effects of these adhesion proteins on EOS effector functions were determined. VCAM-1 induced spontaneous EOS adhesion whereas EOS adhesion to ICAM-1 required a second signal, such as granulocyte macrophage colony-stimulating factor (GM-CSF). Although only VCAM-1 stimulated EOS superoxide anion (O2-) generation, the addition of GM-CSF (100 pM) to the reactions resulted in a greater and equivalent production of O2- with VCAM-1 and ICAM-1. In the presence of GM-CSF, ICAM-1 and VCAM-1 caused significant release of EOS-derived neurotoxin (EDN). Moreover, only ICAM-1 (no GM-CSF) promoted calcium ionophore A23187 (0.2 microM)-induced EOS leukotriene C4 (LTC4). Enhanced O2- generation, EDN release, and LTC4 generation observed with ICAM-1 and VCAM-1 were significantly inhibited by anti-beta2-integrin antibody. These results suggest that ICAM-1 and VCAM-1 are important in determining the eventual function of airway EOS.

Adult↗
PubMed1998

Effectiveness of polyclonal and monoclonal antibodies prepared for an immunoassay of the etofenprox insecticide.

Two polyclonal antibodies and three monoclonal antibodies specific to the etofenprox insecticide were prepared from rabbits and mice, respectively. The monoclonal antibodies were more reactive with etofenprox than the polyclonal antibodies by C-ELISA. Monoclonal antibody cl 205-65 was found to be the most tolerant to methanol, most highly reactive and most specific to etofenprox among the antibodies tested.

Animals↗
PubMed1998

Effects of nasal continuous positive airway pressure therapy on respiratory parameters of upper airway patency in patients with obstructive sleep apnea syndrome.

OBJECTIVES: To assess whether an initial treatment with nasal continuous positive airway pressure (NCPAP) therapy, applied for one night, had any effect on airway patency. METHODS: In 18 patients with obstructive sleep apnea syndrome (OSAS), we measured the total resistance of the respiratory system (Rrs) and their relevant lung functions before and after polysomnography, with and without NCPAP therapy. The Rrs was measured at 3 Hz with the forced oscillation technique. The overnight changes in the specific respiratory conductance (SGrs=reciprocal of the Rrs per unit lung volume) was also calculated in the sitting position. Since many reports have suggested that obesity, through fat deposits around the pharynx, can affect the mechanical and neuromuscular properties of the upper airway, we also investigated if the degree of obesity was related to the magnitude of improvement in these parameters. RESULTS: After the first night of NCPAP therapy, the Rrs decreased (sitting: 4.8+/-0.4 vs 4.3+/-0.4 cm H20/L/s, p < 0.05; lying: 6.5+/-0.4 vs 5.6+/-0.4 cm H20/L/s, p < 0.05) and the maximal voluntary ventilation increased in the morning (sitting: 101.6+/-5.8% vs 106.4+/-4.5%, p < 0.05; lying: 91.2+/-5.4% vs 97.9+/-4.7%, p < 0.05). The overnight difference in the SGrs showed a significant improvement after the initial treatment with NCPAP therapy (p < 0.05). However, the lung volume, flow volume loop, and closing volume in the morning did not change significantly after the therapy. An overnight decrease in the Rrs following NCPAP therapy is significantly correlated with the body mass index (sitting: r=0.54, p < 0.05; lying: r=0.61, p < 0.01). CONCLUSION: The improvements in Rrs without changes in spirometry may reflect improved upper airway patency after NCPAP therapy. The degree of obesity is suggested to be associated with the treatment effect on upper airway in patients with OSAS.

Adult↗
PubMed1998

[ACE inhibitors use in patients with acute coronary syndrome].

Angiotensin converting enzyme (ACE) inhibitors (ACE-I) reduce the incidence of re-infarction in patients with myocardial infarction (MI), and the DD genotype for the ACE gene is an independent risk factor of MI. These findings suggest involvement of ACE in the natural history of coronary plaques and in the pathogenesis of acute coronary syndrome (ACS). ACE-I potentially prevent coronary plaque rupture by suppressing angiotensin II-induced vasoconstriction and sympathetic nerve activity. Actions of ACE-I on risk factors, including insulin resistance, may retard the progression of atheromatous changes in the coronary artery. Furthermore, ACE-I attenuate contractile dysfunction due to myocardial stunning and hibernation, while it augments anti-infarct tolerance of the myocytes afforded by preconditioning. These actions on the myocardium may also be beneficial in ACS. Although favorable effects of ACE-I on the mortality rate of MI patients has been established, the benefit of chronic therapy with ACE-I for patients who have coronary artery disease without MI remains to be clarified.

Acute Disease↗
PubMed1997

Roles of CD9 molecules in survival and activation of human eosinophils.

CD9 is a cell surface glycoprotein belonging to the transmembrane 4 superfamily. In this report, we demonstrate that cross-linking CD9 with different forms of mAb activates distinct functions of human eosinophils. Anti-CD9 mAb (clone ALB6) immobilized onto tissue culture plates induced eosinophil degranulation. This effect of anti-CD9 mAb (clone ALB6) was unique because other immobilized clones of anti-CD9 mAb (clones FMC56 and ML13) or anti-HLA Class I mAb failed to induce degranulation. In addition, neutrophil degranulation was not provoked by the immobilized clone ALB6, consistent with a lack of expression of CD9 on neutrophils. Eosinophil degranulation induced by anti-CD9 mAb (clone ALB6) was abolished by pretreatment of eosinophils with anti-CD18 mAb, suggesting that beta2 integrins are involved in the reaction. In contrast to the results with immobilized clones, all clones of anti-CD9 mAb in soluble form enhanced eosinophil survival. This enhanced survival was inhibited by anti-granulocyte-macrophage-CSF (GM-CSF) mAb, suggesting that autocrine production of GM-CSF by eosinophils mediated the enhanced survival. In fact, by ELISA and RT-PCR, GM-CSF protein and mRNA were detected in supernatants and cell lysates of eosinophils stimulated by soluble anti-CD9 mAb, but not by immobilized mAb. These results indicate that CD9 serves as a molecule that delivers stimulation signals on eosinophils. The eosinophil's cellular responses may differ and be dependent on the manner of receptor ligation.

Antigens, CD↗
PubMed1997

Two excitatory motoneurons differ in quantal content of their junctional potentials in abdominal muscle fibers of the cricket, Gryllus bimaculatus.

In abdominal muscles 202 and 203 of the cricket, Gryllus bimaculatus, large and small excitatory junctional potentials (l- and s-EJPs) with similar durations can be recorded from the same muscle fibers. At the normal extracellular calcium ion concentration ([Ca(2+)](o)) of 5mM, the amplitudes of l-EJPs in both muscles were larger than the threshold membrane potential for muscle action potentials, which is about -40mV. Below 0.75mM [Ca(2+)](o), the amplitudes became much smaller and were below the firing level for the action potentials. At 0.5mM, they fluctuated and decreased to 10.3 and 1.9mV in muscles 202 and 203, respectively, and at 0.25mM frequent failures occurred. The amplitudes of s-EJPs at 5mM [Ca(2+)](o) were 13.3 and 5.1mV in muscles 202 and 203, respectively, and the fluctuating amplitudes were far below the threshold for muscle action potentials. Below 0.75mM, s-EJPs were rarely observed. The relation between log(EJP amplitude) and log([Ca(2+)](o)) was linear within a certain range of [Ca(2+)](o) and the slopes of the lines for l-EJPs were about twice as steep as those for s-EJPs in both muscles. In muscle 202, the amplitude distribution of l-EJPs obtained at 0.25mM and that of s-EJPs at 0.75mM both showed peaks at once and twice the voltage at the first peak, which were coincident with the voltages at the peaks of amplitude distributions of miniature EJPs recorded simultaneously. The reversal potentials for l- and s-EJPs in muscle 202 were +1.02 and +0.22mV, respectively. In muscle 202, the decreases in amplitude of both EJPs by L-glutamate were similar and concentration-dependent. The results suggest that the difference in amplitude between l- and s-EJPs is attributable mainly to the difference in quantal contents.

Journal Article↗
PubMed1997

Impaired induction of cytotoxic T lymphocytes by antagonism of a weak agonist borne by a variant hepatitis C virus epitope.

An epitope that acted as a weak agonist in the cytotoxicity assay was identified as part of the capsid protein of a hepatitis C virus (HCV) variant. In a low concentration, the variant epitope also had a weak antagonistic effect. When a minute amount of this variant epitope was added to the culture for induction, it selectively attenuated the expansion of major cytotoxic T cell populations and drastically reduced the cytotoxic responses against the wild-type epitope. Thus, antagonism to induction suppressed immune responses against both the wild type and the variant, thereby helping the persistence of not only variant itself but also the wild-type HCV. Because this variant was a weak agonist, most cytotoxic T cells induced with the wild-type epitope were cross-reactive with the variant and susceptible to the antagonism to induction. Only the T cells which were not cross-reactive with the variant and not susceptible to the antagonism survived the antagonism in induction. This implied that the specificity of the remaining immune response, if any, was directed exclusively to the wild-type epitope after the emergence of the variant. For viruses like HCV, being heterogeneous itself may contribute significantly toward persistent infection through antagonism to induction.

Antigenic Variation↗
PubMed1997

Cytotoxic T lymphocyte response and viral load in hepatitis C virus infection.

A cytotoxic T lymphocyte (CTL) response to the hepatitis C virus (HCV) nucleoprotein residues 88-96 that are the minimal and optimal epitope for human leukocyte antigen (HLA) B44-restricted CTLs was assessed in 27 HLA B44-positive patients with chronic HCV infection. Serum HCV RNA concentration and the amino acid sequence of the residues 81-100 were also determined. Three patients were infected with HCV with uncommon amino acid substitutions within the epitope. One was infected with HCV with an amino acid substitution in the flanking residues of the epitope. To stimulate CTLs in the peripheral blood, 9-mer peptides that corresponded to the residues 88-96 of the individual patients were synthesized and used. Seven of the 27 patients demonstrated a CTL response to the residues 88-96 with specific cytotoxic activities higher than 20%. The CTL activities were significantly higher in patients with a low titer of serum HCV RNA than in those with a high titer of serum HCV RNA (P = .0006). Some of the patients that demonstrated a CTL response to the residues 88-96 also demonstrated a CTL response to a newly identified HLA B44-restricted CTL epitope or a known HLA A11-restricted CTL epitope or both. No apparent association was observed between the CTL response and the stage of disease, or between the CTL response and the grade of necroinflammatory activity. The results suggest that the HLA B44-restricted CTLs together with other HCV-specific CTLs may inhibit the outgrowth of HCV and that high-titer infection with HCV may suppress the CTL responses.

Adult↗