Biomedical subjects

Alfonso J García-Piñeres

Publications and source records attributed to Alfonso J García-Piñeres.

8 recordsLinked to original sources

PubMed2006

Persistent human papillomavirus infection is associated with a generalized decrease in immune responsiveness in older women.

The development of cervical cancer and its precursors are linked to persistent infection with oncogenic types of human papillomavirus (HPV). Host immune responses seem to be determinants of risk for this disease. However, little is known about the immunologic determinants of HPV persistence. Here, we examined the association between lymphoproliferative responses to antigens/mitogens and persistent HPV infection in women older than 45 years. Women included in this study were participants in a 10,000-woman population-based cohort study of cervical neoplasia in Costa Rica. Women older than 45 years and HPV DNA positive at a screening visit were selected as cases (n = 283). We selected a comparably sized control group of HPV DNA-negative women, matched to cases on age and time since enrollment (n = 261). At an additional clinical visit, women were cytologically and virologically rescreened, and cervical and blood specimens were collected. Proliferative responses to phytohemagglutinin (PHA), influenza virus (Flu), and HPV16 virus-like particle (VLP) were lower among women with persistent HPV infection [median counts per minute (cpm): 72,849 for PHA, 1,241 for Flu, and 727 for VLP] than for the control group (median cpm: 107,049 for PHA, 2,111 for Flu, and 2,068 for VLP). The decreases were most profound in women with long-term persistence and were only observed for the oldest age group (>/=65 years). Our results indicate that an impairment in host immunologic responses is associated to persistent HPV infection. The fact that effects were evident for all studied stimuli is suggestive of a generalized effect.

Age Factors↗

PubMed2006

Cellular immune responses to HPV-18, -31, and -53 in healthy volunteers immunized with recombinant HPV-16 L1 virus-like particles.

Human papillomavirus-like particles (HPV VLP) are candidate vaccines that have shown to be efficacious in reducing infection and inducing robust antiviral immunity. Neutralizing antibodies generated by vaccination are largely type-specific, but little is known about the type-specificity of cellular immune responses to VLP vaccination. To determine whether vaccination with HPV-16 L1VLP induces cellular immunity to heterologous HPV types (HPV-18, HPV-31, and HPV-53), we examined proliferative and cytokine responses in vaccine (n=11) and placebo (n=5) recipients. Increased proliferative and cytokine responses to heterologous types were observed postvaccination in some individuals. The proportion of women responding to heterologous types postvaccination (36%-55%) was lower than that observed in response to HPV-16 (73%). Response to HPV-16 VLP predicted response to other types. The strongest correlations in response were observed between HPV-16 and HPV-31, consistent with their phylogenetic relatedness. In summary, PBMC from HPV-16 VLP vaccine recipients can respond to L1VLP from heterologous HPV types, suggesting the presence of conserved T cell epitopes.

Adolescent↗

PubMed2006

DNAse treatment following thawing of cryopreserved PBMC is a procedure suitable for lymphocyte functional studies.

Testing freshly isolated PBMC is not practical for immune monitoring analysis in large clinical trials or natural history studies. Thus, cryopreserved PBMC represent a more practical alternative. However, cell clumping is a common problem following thawing of PBMC isolated from blood that was previously transported and stored. Cell clumping leads to loss of cells, and could affect cell function and/or phenotype. The development and validation of procedures that prevent cell clumping and preserve cell function and surface marker expression levels are necessary to allow evaluation of immune function and phenotype in cryopreserved samples from clinical studies. The incorporation of a DNAse treatment step in the standard thawing procedure efficiently avoided clump formation, and did not result in detectable changes in cell viability, expression of standard leukocyte surface markers or two key parameters of immune function, proliferation and cytokine induction in response to a variety of common stimuli. Therefore, this procedure seems suitable for standard immunologic assays.

Antigens↗

PubMed2006

Role of DC-SIGN in the activation of dendritic cells by HPV-16 L1 virus-like particle vaccine.

Dendritic cell-specific intercellular adhesion molecule-grabbing non-integrin (DC-SIGN), a specific C-type lectin expressed on DC, binds and transmits different pathogens to susceptible cells. In the present study, we examined the role of DC-SIGN in the capture of human papillomavirus (HPV) pseudovirions and activation of DC. We demonstrate that HPV virus-like particles (VLP) bind to DC-SIGN expressed on transfected Raji cells and that antibodies against DC-SIGN block this interaction. DC take up VLP, which activate expression of costimulatory markers and cytokines/chemokines. Although our results indicate that DC-SIGN is not the major receptor for VLP in DC, this interaction contributes to the activation of DC surface antigens (HLA class I) and of various cytokines/chemokines, particularly TNF-alpha, IL-6, and RANTES. Induction of these markers in DC by VLP was significantly abrogated when binding to DC-SIGN was blocked by anti-DC-SIGN antibodies. These results suggest that DC-SIGN has a functional role in DC activation induced by HPV-16 L1-VLP, and thus highlight new aspects of DC interactions with HPV VLP.

Antibodies, Monoclonal↗

PubMed2004

Quantitative structure-activity relationship of sesquiterpene lactones as inhibitors of the transcription factor NF-kappaB.

Sesquiterpene lactones (SLs) are the active compounds of a variety of traditionally used medicinal plants from the Asteraceae family. They are known to possess a considerable antiinflammatory activity in different inflammation models. They inhibit the transcription factor NF-kappaB probably by alkylating cysteine38 in the DNA binding domain of the p65 subunit. Here we investigate a set of 103 different sesquiterpene lactones representing 6 structural groups (44 germacranolides, 16 heliangolides, 22 guaianolides, 9 pseudoguaianolides, 2 hypocretenolides, 10 eudesmanolides) for their NF-kappaB inhibiting properties and the resulting IC(100)-values were submitted to a QSAR study. Properties important for the inhibition potency are discussed for the whole data set and for subsets of the different structural classes.

Electrophoretic Mobility Shift Assay↗

PubMed2004

Sesquiterpene lactones inhibit luciferase but not beta-galactosidase activity in vitro and ex vivo.

Reporter enzymes such as firefly luciferase or beta-galactosidase of Escherichia coli are frequently used to study transcriptional activity of genes and to investigate the effects of novel compounds on gene or transcription factor activity. It is generally assumed that the activity of these enzymes is unaffected by the treatment conditions. Therefore, this factor is not considered when interpreting the data obtained. Biologically active compounds such as sesquiterpene lactones (SLs) have also been tested in reporter gene assays for their influence on gene expression. Here we show in in vitro and ex vivo experiments that SLs inhibit firefly luciferase activity probably by direct targeting of the enzyme while beta-galactosidase remains almost completely unaffected. The loss of luciferase activity after SL treatment could be an effect of their sulfhydryl-modifying potency and the subsequent alteration of the enzyme's tertiary structure. These results demonstrate that the effect of the test substance on the reporter enzyme used should be taken into consideration when the transcriptional effect of novel compounds is investigated.

Animals↗

PubMed2003

Effect of sesquiterpene lactones on the expression of the activation marker CD69 and of IL-2 in T-lymphocytes in whole blood.

We used flow cytometry to investigate the inhibitory effect of sesquiterpene lactones (SLs) on T-cell activation measured by the expression of its early marker CD69, and on interleukin (IL)-2, a mediator of activation, in whole blood. SLs are biologically active compounds found especially in plants from the Asteraceae family. Overnight treatment of blood with these substances led to the inhibition of CD69 and IL-2 expression. Interestingly, bifunctional SLs showed a weaker activity than monofunctional substances, which is in contradiction with the data obtained so far, using other biological test systems. Additionally, SLs did not completely inhibit CD69 or IL-2 expression. We also determined their toxicity and observed only a low effect. Up to now, studies on cytotoxicity have only been performed using cultured cell lines. From these results it may be supposed that these natural compounds preferentially show toxic effects towards transformed cell lines. Altogether, the results demonstrated that SLs effectively inhibit the activation of the T-lymphocyte response in whole blood and proved the utility of a whole blood system in studying their biological effects.

Antigens, CD↗

PubMed2002

Guaianolides from Viguiera gardneri inhibit the transcription factor NF-kappaB.

Five guaianolides and a germacrolide were isolated from the leaf rinse extract of Viguiera gardneri (Asteraceae), together with known compounds. All compounds were detected in glandular trichomes collected from the leaves and were analyzed by HPLC. Structure elucidation was based on the analysis of spectroscopic data. Low energy conformations were obtained by quantum mechanical calculations. Three closely related guaianolides which were isolated as the main compounds were studied for their anti-inflammatory activity using the transcription factor NF-kappaB as molecular target. NF-kappaB DNA binding was inhibited at sesquiterpene lactones concentrations of 10 or 50 microM.

Asteraceae↗