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Biomedical subjects

A De Maria

Publications and source records attributed to A De Maria.

At least 19 recordsLinked to original sources
PubMed2002

Synthesis, structure, and second-order nonlinear optical properties of copper(II) and palladium(II) acentric complexes with N-salicylidene-N'-aroylhydrazine tridentate ligands.

Two new N-salicylidene-N'-aroylhydrazines ligands have been prepared: N-4-diethylaminosalicylidene-N'-4-nitrobenzoyl-hydrazine (L(1)) and N-4-diethylaminosalicylidene-N'-4-(4-nitrophenylethylidene)-benzoyl-hydrazine (L(2)). The ligands are properly functionalized with strong electron donor-acceptor groups and are of potential interest in second-order nonlinear optics (NLO). Dimeric copper(II) and palladium(II) complexes with L(1) and L(2) have been prepared, and, starting from these, mononuclear acentric adducts with pyridine as a further ligand have been prepared and characterized. The X-ray structures of three adducts are also reported. The NLO activity of the adducts has been determined by EFISH measurements giving mubeta values up to 1500 x 10(-48) esu for an incident wavelength of 1.907 microm.

Journal Article↗
PubMed2001

Differential disappearance of inhibitory natural killer cell receptors during HAART and possible impairment of HIV-1-specific CD8 cytotoxic T lymphocytes.

BACKGROUND: Highly active antiretroviral therapy (HAART) is associated with a decrease in viral replication to undetectable levels and with an increase in CD4 T lymphocytes. Residual HIV-1 replication occurs together with incomplete recovery of cytotoxic CD8 T lymphocyte (CTL) numbers and function. We sought to determine whether expression of HLA class I-specific inhibitory natural killer receptors (iNKR) on the CTL of patients who had been treated successfully with HAART for 24 months could be involved, at least in part, in residual CTL functional inhibition. METHODS: Two-colour cytofluorometry was used to analyse the expression of six different iNKR including p58.1, p58.2, p70, p140, CD94/NKG2A and LIR1/ILT2 on the CD3, CD8 lymphocytes of eight patients with successful long-term suppression of viral replication before and after 3, 6 and 24 months of HAART. Healthy subjects were analysed as controls. HIV-1-specific cytotoxic activity was determined after 24 months of HAART in the presence and absence of iNKR-masking. RESULTS: No significant reduction of iNKR expression on CD8 T cells was observed by 6 months. Expression of p70 and p140 was inversely correlated with the increasing CD4 numbers. After 24 months CD8 T-lymphocytes expressing p58.1, p58.2, p70, p140 and CD94/NKG2A returned to levels indistinguishable from those of the healthy controls. A significantly increased proportion of CD8 CTL still expressed LIR1/ILT2, a receptor with broad HLA-class I specificity. Functional analysis of freshly separated cells revealed that the disruption of the interaction between LIR1/ILT2 and HLA-class I could partly restore HIV-1-specific lysis. CONCLUSIONS: A decrease in CD3CD8iNKR cells is observed beyond 6 months of HAART. In some patients functional impairment due to LIR1/ILT2 expression may persist even after 24 months of successful HAART.

Adult↗
PubMed2001

Identification, molecular cloning and functional characterization of NKp46 and NKp30 natural cytotoxicity receptors in Macaca fascicularis NK cells.

Natural killer (NK) cell recognition and function in humans is regulated by multiple cell surface receptors. The "on" signal leading to NK cell triggering is primarily mediated by natural cytotoxicity receptors (NCR). Analysis of NK cells in primate animal models is of particular relevance because NK cells may play an essential role in host defenses against infections. We analyzed Macaca fascicularis PBMC and in vitro-derived NK cell populations and clones by cytofluorometry, using a wide panel of mAb, and by cytolytic activity assays. In addition, RT-PCR strategy and transient transfections were used to isolate M. fascicularis NCR. NCR-specific mAb reactivity (anti-NKp46 and anti-NKp30) was present on M. fascicularis PBMC and on NK cell cultures. Macaque NCR were functional in both redirected killing and in mAb-mediated masking assays. Cloning of macNKp46 and macNKp30 NCR homologous genes showed a high sequence similarity (86 % and 88 %, respectively) with their human counterparts. Attempts at identifying NKp44 surface reactivity and at cloning the macaque homologue were unsuccessful. NKp46 and NKp30 NCRs, but not NKp44, are highly conserved in M. fascicularis NK cells. This suggests the possibility of a staged appearance of the NCR during phylogenesis and provides a useful tool for the study of natural immunity correlates of protection in primate SIV/SHIV infection models.

Amino Acid Sequence↗
PubMed2001

The MHC class II transactivator: prey and hunter in infectious diseases.

The MHC class II transcriptional activator (CIITA) is the major regulator of expression of MHC class II genes. Thus, CIITA plays a fundamental role in the regulation of the immune response. Here, we discuss our findings on the dual role of CIITA during infections, as the target (prey) for certain pathogens but the host effector (hunter) against other pathogens, including HIV-1. This dual role is placed in an evolutionary context as a rather peculiar example of a strategy used by pathogens to evade host defenses and a counteraction of the host to minimize the survival and spread of the pathogen.

Animals↗
PubMed2001

Utility of B-natriuretic peptide as a rapid, point-of-care test for screening patients undergoing echocardiography to determine left ventricular dysfunction.

BACKGROUND: Although echocardiography is an important tool for making the diagnosis of left ventricular (LV) dysfunction, the cost of this procedure limits its use as a routine screening tool for this purpose. Brain natriuretic peptide (BNP) accurately reflects ventricular pressure, and preliminary studies have found it to be highly sensitive and highly specific in diagnosing congestive heart failure in the emergency department. We hypothesized that BNP might therefore be useful as a screening tool before echocardiography in patients with suspected LV dysfunction. METHODS: Subjects included patients referred for echocardiography to evaluate the presence or absence of LV dysfunction. Patients with known LV dysfunction were excluded from analysis. BNP was measured by a point-of-care immunoassay (Biosite Diagnostics, San Diego, Calif). The results of BNP levels were blinded from cardiologists making the assessment of LV function. Patients were divided into those with normal ventricular function, abnormal systolic ventricular function, abnormal diastolic function, and evidence of both systolic and diastolic dysfunction. RESULTS: Two hundred patients in whom LV function was unknown were studied. In the 105 patients (53%) whose ventricular function was subsequently determined to be normal by echocardiography, BNP levels averaged 37 +/- 6 pg/mL. This was significantly less than in those patients with either ultimate diastolic dysfunction (BNP 391 +/- 89 pg/mL (P <.001) or systolic dysfunction (BNP 572 +/- 115 pg/mL (P <.001). A receiver-operator characteristic curve showing the sensitivity and specificity of BNP against the echocardiography diagnosis revealed the area under the curve (accuracy) was 0.95. At a BNP level of 75 pg/mL was 98% specific for detecting the presence or absence of LV dysfunction by echocardiography. CONCLUSIONS: A simple, rapid test for BNP, which can be performed at the bedside or in the clinic, can reliably predict the presence or absence of LV dysfunction on echocardiogram. The data indicate that BNP may be an excellent screening tool for LV dysfunction and may, in fact, preclude the need for echocardiography in many patients.

Aged↗
PubMed2000

Multiple HLA-class I-specific inhibitory NK receptor expression and IL-4/IL-5 production by CD8+ T-cell clones in HIV-1 infection.

Several mechanisms may contribute to the decline in HIV-1 specific CD8+ cytotoxic T-lymphocyte (CTL) activity that is observed in infected patients, including loss of CD4+ cell help, antigenic shift, impaired clonogenicity and functional impairment due to expression of inhibitory NK receptors (iNKRs). In addition to a decrease in HIV-1-specific cytolytic activity, an increased proportion of CD8+ T-cells producing IL-4 and IL-5 has been recently observed in advanced HIV-1 infection. Remarkably, an impaired HIV-1-specific CTL activity was primarily detected among the TC0/Tc2 CD8+ CTLs. A series of CD3+CD8+ T-cell clones expressing inhibitory NK receptors (iNKRs) isolated from HIV-1 infected patients was analyzed in order to determine their cytokine production pattern and to assess the extent of iNKR expression at the single cell level. Our data indicate that iNKR+CD3+CD8+ clones isolated from infected patients frequently express multiple iNKR and may produce IL-4 and IL-5 to a relevant extent.

Antigens, CD↗
PubMed2000

HLA-class I-specific inhibitory receptors in HIV-1 infection.

One of the most characteristic and, at the same time, puzzling features of the cellular immune response towards HIV-1 is represented by an early vigorous HIV-specific CD8+ CTL response that does not prevent disease progression in the vast majority of patients. In this context, there is a striking mismatch over the course of disease progression between increasing numbers of activated CD8+ T cells and apparent decrease of virus-specific CD8+ CTLs. Inhibitory NK receptors (iNKRs) specific for HLA class I molecules can be expressed on CD8+ T-cells of healthy individuals and deliver inhibitory signals that determine decreased CTL function. Their expression on CD8+ CTL may be induced by IL-15 or TGFP in vitro, and may represent an important regulatory function for the fine-tuning of the antigen-specific T cell response against tumors and intracytoplasmic pathogens. In HIV-1 infected patients, relevant proportions of peripheral blood CD8+ T lymphocytes express iNKRs belonging to the Ig superfamily (p58/p70/p140) and CD94/NKG2A. Presence of iNKRs on CD8+ CTLs impairs HIV-1-specific cytolytic activity in vitro and may allow uncontrolled viral replication and spread following functional inhibition of CTL effectors in infected patients.

HIV Infections↗
PubMed1997

Expression of HLA class I-specific inhibitory natural killer cell receptors in HIV-specific cytolytic T lymphocytes: impairment of specific cytolytic functions.

Human T lymphocytes have been shown to express inhibitory natural killer cell receptors (NKR), which can down-regulate T cell antigen receptor-mediated T cell function, including cytolytic activity. In the present study, we demonstrate that CD3+NKR+ cells can be identified in HIV-infected patients. HIV-specific cytolytic activity was analyzed in five patients in whom autologous lymphoblastoid B cell lines could be derived as a source of autologous target cells. Phytohemagglutinin-activated T cell populations that had been cultured in interleukin 2 displayed HIV-specific cytotoxic T lymphocyte (CTL) activity against HIV env, gag, pol, and nef in 3 of 5 patients. Addition of anti-NKR mAb of IgM isotype could increase the specific CTL activity. Moreover, in one additional patient, HIV-specific CTL activity was undetectable; however, after addition of anti-NKR mAb such CTL activity appeared de novo. Similar results were obtained by analysis of CD3+NKR+ clones derived from two patients. These data provide direct evidence that CD3+NKR+ cells may include antigen (HIV)-specific CTLs and that mAb-mediated masking of inhibitory NKR may revert the down-regulation of CTL function.

Antibodies, Monoclonal↗
PubMed1996

Detection of virus in vertically exposed HIV-antibody-negative children.

BACKGROUND: HIV-infected mothers can transmit their infection to their children in utero or at delivery (vertical transmission). There have been cases of children who were reported as acquiring infection vertically and later clearing the infection. We report the frequency of this phenomenon in a European cohort study. METHODS: In four centres of the European Collaborative Study of children born to HIV-infected mothers, 299 children became HIV-antibody-negative and 264 of these had been followed up with virus culture and PCR for viral DNA at least once. FINDINGS: Nine of the 264 children were positive by virus culture or PCR, and subsequently seroreverted. Two of the nine tested virus-positive after they became antibody-negative. Six cases were virus-positive early in life and became negative thereafter, which is consistent with clearance of infection. The pattern was less clear in the other three. The nine cases had had their last virus test at age 16-101 months. All nine children had been bottlefed only. Eight had been delivered vaginally. The children had no HIV-related symptoms and received no anti-HIV treatments. Based on only those children who had two or more positive virological tests, we estimate that 2.7% (6/219) cleared or "tolerated" the virus. INTERPRETATION: The detection of virus or viral DNA in "uninfected" children born to HIV-infected mothers was rare and was not associated with clinical disease or immunological abnormalities. The timing of samples will affect the documentation of clearance since, in uninfected children of HIV-positive mothers who cleared the virus, viraemia was intermittent. Current paediatric opinion is to inform parents of children who serorevert that the child is not HIV-infected.

Child, Preschool↗
PubMed1995

Use of polymerase chain reaction and quantitative antibody tests in children born to human immunodeficiency virus-1-infected mothers.

The diagnosis of human immunodeficiency virus (HIV) infection in children born to HIV-infected mothers is complicated by the presence of passively acquired maternal antibodies, and exclusion of infection in these infants remains problematic. The use of genome detection by polymerase chain reaction (PCR) amplification and the quantification of anti-HIV-1 antibodies were examined as methods for early diagnosis. Blood samples were taken from 84 non-breast-fed infants of HIV-infected mothers in five Italian and Spanish centres, a subgroup of children enrolled in the European Collaborative Study (ECS) for whom clinical and immunological information has been documented from birth. Whole blood was added to glycigel cryopreservative, stored, and tested in the United Kingdom by a nested PCR method. Antibody to HIV-1 was detected and quantified by titration using a gelatin particle agglutination test. PCR sensitivity and specificity were assessed. Twenty-one of the 84 children tested were infected. The estimated PCR sensitivity ranged from 0% (95% CI 0-26%) on day 1, 57% (19-85) on day 7, to 63% (33-92) on day 30. The negative predictive value of PCR ranged from 85% (83-88) on day 0 to 98% (94-100) at 3 months of age. On average, the level of maternal antibody halved every 33 days (31-36.5) in uninfected children. Between 6 and 9 months of age, increases in antibody titres in infected children were not more informative than absolute levels. These findings suggest that antibody measurement may supplement genomic diagnosis and that this collection method provides an alternative to the use of dried blood spots.

Age Factors↗
PubMed1995

Adhesion of human neuroblasts to HIV-1 tat.

Several neuropathologic findings in infants and children with human immunodeficiency virus type-1 (HIV-1) infection are different from those observed in adults, probably related to the fact that the retroviral infection occurs in the setting of neuro-development. This report describes the interaction and biologic activity of tat, the HIV-1 trans-activating protein on human neuroblasts. Two human neuroblastoma cell lines, LAN-5 and GI-CA-N, have been studied for their capability to adhere to tat (full recombinant protein) and to two different peptide residues of it. Both cells adhere to tat and tat46-60 basic domain, although not to tat65-80 residue, which contains the RGD (arginine-glycine-aspartic acid) motif. Adhesion to collagen I was inhibited by preincubating GI-CA-N cells with tat,46-60 although not with tat,65-80 indicating the capability of the basic residue to interfere with collagen I-induced cellular adhesion. The expression of 200-kD neurofilaments induced by collagen I was not induced by tat,46-60 indicating that neural differentiation along the same pathway is not mimicked by this peptide. Neuroblast cell proliferation was not affected by adhesion to tat46-60 nor to tat.65-80 GI-CA-N cells are not permissive to HIV-1 infection. However, proviral DNA was documented in the cell lysate for 14 consecutive in vitro passages, whereas HIV-1 transcription was never detectable. This would exclude the possibility that tat would be transduced by these cells. GI-CA-N stained negative for CD4, although positive for Gal-C, which may explain HIV-1 entry. Results show that immature human neural cells interact with tat protein and/or its basic residue in vitro. A mechanism similar to that herein described would possibly be active in vivo, which may help in clarifying the pathogenic mechanisms of neurologic dysfunction and destruction of the CNS observed in infants infected with HIV-1.

Amino Acid Sequence↗
PubMed1995

Characterisation of eye-lens DNases: long term persistence of activity in post apoptotic lens fibre cells.

Fibre cells in the ocular lens exhibit a constitutive apoptotic process of nuclear degradation that includes chromatin breakage, generating a ladder pattern of DNA fragments. This process is intrinsic to the normal terminal differentiation program. Despite the loss of nucleus and cytoplasmic organelles, the terminal differentiated fibre cells remain in the lens during the whole life span of the individual. The lens cells thus provide a unique system in which to determine the presence and fate of endonucleases once the chromatin has been cleaved. We report here on the presence of DNase activity in nucleated and anucleated lens cells. Using a nuclease gel assay and double-stranded DNA as substrate, we found active 30 and 60 kDa DNases. The enzymatic activities were Ca(2+), Mg(2+) dependent, and active at neutral pH. The relative amount of these forms changed during development and aging of the lens fibre cells. Both forms were inhibited by Zn(2+), aurintricarboxylic acid, and G-actin. The proteins were also separated by SDS-PAGE, renatured after removing SDS and incubated in the presence of native DNA adsorbed to a membrane. Therefore it was possible to demonstrate, by means of a nick translation reaction, that the enzymes produced single strand cuts. Based on these findings we propose that these chick lens nucleases are probably related to DNase I.

Journal Article↗