Biomedical subjects

Marcus Williams

Publications and source records attributed to Marcus Williams.

4 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

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↗

PubMed2005

HPV-16 L1 VLP vaccine elicits a broad-spectrum of cytokine responses in whole blood.

Here, we evaluated innate and adaptive immune system cytokine responses induced by HPV-16 L1 VLP in whole blood (WB) cultures from individuals receiving the vaccine (n=20) or placebo (n=4) before and after vaccination. 11 cytokines were measured: IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, IFN-gamma, TNF-alpha, and GM-CSF using multiplex bead arrays. Cytokine profiles from WB samples clearly discriminated between vaccine and placebo recipients and between pre and post-vaccination responses. Significant increases in Th1, Th2 and inflammatory cytokines were observed in WB assays following vaccination. Results from WB assays were compared against parallel PBMC-based assays in a subset of patients. Differences between whole blood assay and PBMC were observed, with the highest levels of induction found for WB for several cytokines. Our results indicate that multiplex assays for cytokine profiling in WB are an efficient tool for assessing broad spectrum, innate and adaptive immune responses to vaccines and identifying immunologic correlates of protection in efficacy studies.

Adolescent↗