Levels of Soluble Endothelial Protein C Receptor Are Associated with CD4+ Changes in Maraviroc-Treated HIV-Infected Patients

BACKGROUND: Inflammation is a key feature of HIV infection and is correlated with long-term negative cardiovascular outcomes. Therapy-induced increases in CD4(+) cell counts can control inflammation, as shown by decreases of coagulation and inflammation markers during efficacious therapy. Maraviroc, a CCR5-antagonist, has resulted in larger increases in CD4(+) counts both in naïve and experienced subjects compared to traditional antiretroviral therapy. OBJECTIVES AND METHODS: To examine if a member of the protein C anticoagulant and anti-inflammatory pathway, and marker of coagulation and inflammation, the soluble endothelial protein C receptor, is modified by infection and therapy-related variables in patients treated with Maraviroc. Endothelial protein C receptor, together with other established markers of inflammation and coagulation (CRP, IL-6, D-dimer and soluble thrombomodulin) was studied in 43 patients on traditional antiretroviral therapy and in 45 on Maraviroc during 48 weeks of follow-up. RESULTS: Soluble endothelial protein C receptor was the only marker that could discriminate at least partially between patients with a good response to Maraviroc and patients who did not respond with an adequate increase in CD4(+) cell counts (more than 500 cells/µL by week 48). CONCLUSIONS: Elevated levels of soluble endothelial protein C receptor, a sensitive marker of endothelial damage, indicated a low level of inflammation and coagulation activation in Maraviroc treated patients not picked up by other widely used markers. Persistent elevated levels of this marker at 48 weeks from beginning of treatment with Maraviroc were related to a poor increase in CD4(+) cells

Multifunctional specificity of the protein C/activated protein C Gla domain

Activated protein C (APC) has potent anticoagulant and antiinflammatory properties that are mediated in part by its interactions with its cofactor protein S and the endothelial cell protein C receptor (EPCR). The protein C/APC Gla domain is implicated in both interactions. We sought to identify how the protein C Gla domain enables specific protein-protein interactions in addition to its conserved role in phospholipid binding. The human prothrombin Gla domain, which cannot bind EPCR or support protein S cofactor activity, has 22/45 residues that are not shared with the human protein C Gla domain. We hypothesized that the unique protein C/APC Gla domain residues were responsible for mediating the specific interactions. To assess this, we generated 13 recombinant protein C/APC variants incorporating the prothrombin residue substitutions. Despite anticoagulant activity similar to wild-type APC in the absence of protein S, APC variants APC(PT33 -39) (N33S/V34S/D35T/D36A/L38D/A39V) and APC(PT36/38/39) (D36A/L38D/A39V) were not stimulated by protein S, whereas APC(PT35/36) (D35T/D36A) exhibited reduced protein S sensitivity. Moreover, PC(PT8/10) (L8V/H10K) displayed negligible EPCR affinity, despite normal binding to anionic phospholipid vesicles and factor Va proteolysis in the presence and absence of protein S. A single residue variant, PC(PT8), also failed to bind EPCR. Factor VIIa, which also possesses Leu-8, bound soluble EPCR with similar affinity to wild-type protein C, collectively confirming Leu-8 as the critical residue for EPCR recognition. These results reveal the specific Gla domain residues responsible for mediating protein C/APC molecular recognition with both its cofactor and receptor and further illustrate the multifunctional potential of Gla domains

Evaluation of platelet function in essential thrombocythemia under different analytical conditions

Background. Studies of platelet aggregation (PA) in essential thrombocythemia (ET) reported contrasting results, likely due to differences in analytical conditions. Objective. We investigated platelet aggregation using different techniques and analytical conditions. Patients and Methods. PA was studied by light-transmission aggregometry (LTA) in platelet-rich plasma (PRP) and impedance aggregometry in PRP and whole blood (WB). ADP, collagen, thrombin receptor activating peptide (TRAP-14) and adrenaline were used as agonists. Since ET patients (n = 41) were on treatment with aspirin (100 mg/d), healthy controls (n = 29) were given aspirin (100 mg/d) for 5 days before testing: therefore, thromboxane A2-independent PA was tested in all subjects. Blood samples were collected in citrate (C) [low Ca2+] or lepirudin (L) [physiological Ca2+]; platelet count was adjusted to 250 x 109/L in a set of C-PRP (adjusted C-PRP) and left unmodified in the other samples. Results. Results of PA in 17 ET patients who were poor responders to aspirin (high serum thromboxane B2 levels) were not included in the analysis. With LTA, PA in ET was lower than in controls in adjusted C-PRP and normal in native C-PRP and L-PRP. With impedance aggregometry, PA in L-PRP and L-WB tended to be higher in ET than in controls. Platelet serotonin and ADP contents were reduced in ET. The percentages of circulating platelets expressing P-selectin and platelet-leukocyte hetero-aggregates were higher in ET. Conclusions. Analytical conditions dramatically affect in vitro PA of ET patients, which appears defective under the least physiological conditions and normal/supranormal under conditions that are closer to the physiological

Changes in metabolic variables and CD4⁺ cell counts over time in patients on ART (solid line, squares) or ART with MVC (broken line, circles).

<p>* denotes p<0.05 and ** p<0.01 for differences between the two patient groups at the time shown (Mann-Whitney test after non parametric analysis of variance for repeated measures).</p

HIV-RNA copy levels by time and treatment group.

<p>Data is presented as median and range. 49 copies is the lower limit of detection of the assay, and it was written in the database to indicate that the HIV-RNA was undetectable.</p

Age and laboratory variables at baseline of patients on ART (n = 43) or ART and MVC (n = 45).

<p>Results are presented as median and range.</p>*<p>p = 0.013 for direct comparison (Mann-Whitney).</p>§<p>p = 0.003 for direct comparison (Mann-Whitney).</p

Median (range) levels of sEPCR.

<p>Median (range) levels of sEPCR.</p