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Biomedical subjects

S Vento

Publications and source records attributed to S Vento.

At least 73 records · Page 4Linked to original sources
PubMed1993

Risk of reactivation of tuberculosis in the course of human immunodeficiency virus infection.

OBJECTIVES: To establish, in a longitudinal study, whether reactivation of latent tuberculous infection takes place below an identifiable immunological threshold in subjects with human immunodeficiency virus (HIV) infection. METHODS: We followed up for 2 years 44 subjects with HIV infection who had a positive intradermal reaction to tuberculin. All subjects were asymptomatic at enrollment. End points of the study were the development of active tuberculosis or the final evaluation (24 months since the beginning) for those who did not develop tuberculosis over the study period. Total lymphocyte count, CD4+ lymphocyte count and beta-2 microglobulin serum levels were measured at baseline, during the period of observation (every 3-6 months) and at the end point. Multiple Antigen Skin Testing and purified protein derivative (PPD) testing were also performed at baseline and end point, as well as in intermediate phases of the study (every 6 and 12 months respectively). RESULTS: Ten subjects (22.7%) developed tuberculosis during the study period. Both baseline and end point values of the parameters investigated differed significantly between subjects who developed tuberculosis and those who did not. Cox's model showed that total and CD4+ lymphocyte counts as well as beta-2 microglobulin levels had a prognostic value at a univariate analysis; CD4+ and beta-2 microglobulin retained statistical significance in a multivariate evaluation. CD4+ lymphocyte count was the parameter most strongly associated with the development of tuberculosis. CONCLUSIONS: Tuberculosis in this setting most often reactivates only when immune surveillance has fallen to an identifiable level. Planners of antituberculous chemoprophylactic policies should consider the downgrading tendency of immune function in these subjects in order to choose the most appropriate time to intervene in the course of HIV infection. Starting prophylaxis in HIV-infected subjects only when CD4+ cells have dropped below the value of 500/mm3 seems to be a more fruitful option than the currently adopted strategy, which recommends time-limited (12 months) administration of daily isoniazid to all PPD+ HIV-infected subjects regardless their immunological status.

Adult↗
PubMed1991

Identification of hepatitis A virus as a trigger for autoimmune chronic hepatitis type 1 in susceptible individuals.

To identify factors contributing to the pathogenesis of autoimmune chronic active hepatitis (CAH) healthy relatives of 13 patients with the disorder were followed prospectively for 4 years. 58 relatives were monitored for various serological markers and for T-lymphocyte migration inhibitory activity every 2 months. 3 cases of subclinical acute hepatitis A occurred during the study. In 2 of the 3 subjects, before hepatitis A virus (HAV) infection, there was a defect in suppressor-inducer T lymphocytes specifically controlling immune responses to the asialoglycoprotein receptor, an antigen expressed on the hepatocyte surface. In these 2 subjects, specific helper T cells and antibodies to the asialoglycoprotein receptor persisted and increased after acute hepatitis A, and autoimmune CAH type 1 developed within 5 months. Thus, in susceptible individuals HAV is a trigger for autoimmune CAH.

Adult↗
PubMed1991

Identification of T cell epitopes on hepatitis B surface antigen.

The antigenic sites for human T lymphocytes on hepatitis B surface antigen (HBsAg) have been studied using synthetic peptides. The results indicate that aminoacid residues 24-28 of HBsAg (located near the amino terminus of the HBsAg molecule) constitute an immunodominant "helper" determinant, whereas residues 17-18 and/or 34-36 represent a major "suppressor" epitope. However, non responsiveness to currently used hepatitis B virus (HBV) vaccines (employing the whole HBsAg molecule) does not depend, in the vast majority of cases, on suppressor T cells. In vivo experiments with synthetic peptide vaccines are needed to verify the possibility of enhancing the production of protective antibodies against the hepatitis B virus.

Amino Acid Sequence↗
PubMed1990

Patterns of cellular immune responses to thyrocyte membrane antigens and specific immunoregulatory defects in autoimmune thyroid disease.

Although Graves' disease (GD), Hashimoto's thyroiditis (HT) and idiopathic myxoedema (Myx) are clinically distinct autoimmune thyroid diseases, previous studies using crude thyroid preparations as a source of antigens have failed to identify differences in cellular immune responses. In this study, we have assessed cellular immunity in patients with these disorders to two antigen preparations (derived from thyroid gland and cervical fat) enriched in cell membranes and known to share a functional TSH receptor. Using an indirect T-lymphocyte migration inhibitory factor (T-LIF) assay, T-cell immunity to thyroid membranes was demonstrated in 11/11 patients with GD, 4/5 with HT and 4/5 with Myx, but in none of 18 patients with chronic active hepatitis (another organ-specific autoimmune disease) or sixteen healthy controls. In contrast, T lymphocytes responsive to adipocyte membranes were detected only in patients with GD. TSH binding inhibiting antibodies were found exclusively in six patients with GD, and thyroid stimulating antibodies in five of these patients. In co-culture experiments designed to study the activity of antigen-specific suppressor T cells, low numbers of T cells from 6/6 normal controls, 4/4 patients with HT and 5/5 patients with myxoedema suppressed the response to adipocyte membranes of T lymphocytes from patients with Graves' disease. The results of this study demonstrate different patterns of T-cell reactivity to thyroid antigens in patients with Graves' disease, Hashimoto's thyroiditis and myxoedema and suggest that cellular immunity to the TSH receptor is restricted to patients with Graves' disease and associated with a defect in the specific immunoregulatory control of this response.

Adolescent↗
PubMed1988

Sequential studies of pre-S2 antigenemia and anti-pre-S2 antibodies in relation to viral replication in acute hepatitis B followed from the early incubation phase.

To determine the time sequence of expression of pre-S2 peptide (120-150) during the presymptomatic phase of acute hepatitis B, we used a monoclonal antibody radioimmunoassay in five subjects followed from 30 to 70 days before the onset of liver damage. Pre-S2 peptide was present in serum at low levels from the early incubation phase and started to increase immediately after the first detection of HBV-DNA in serum, in parallel with the increase in HBsAg levels. During the symptomatic phase, levels of pre-S2 peptide declined rapidly; it was no longer detectable after recovery. Anti-pre-S2 antibodies were detected, in four patients, only in the recovery phase. These results demonstrate that expression of pre-S2 peptide occurs very early in the incubation phase of acute HBV infection and is cleared in parallel with HBsAg. Anti-pre-S2 antibodies seem to play no role in viral clearance in these patients.

Adolescent↗