INDIVIDUALISATION OF HIV THERAPY: THE CLINICIAN'S PERSPECTIVE

SUMMARY Assessment of clinical and laboratory markers of HIV infection may be used to individualise antiretroviral therapy. Data suggest that measures of viral load may be of considerable value as both a baseline and dynamic therapy marker, making these tools particularly useful in driving therapeutic decisions. Similarly, in-vitro data regarding intracellular pharmacokinetics and activity, resistance patterns and potential synergy of antiretroviral agents may be used to guide selection of optimal treatment regimens in clinical practice.     

Structural requirements of platelet chemokines for neutrophil activation

Using recombinantly expressed proteins and synthetic peptides, we examined the structural/functional features of the platelet chemokines, neutrophil-activating peptide-2 (NAP-2) and platelet factor 4 (PF4); that were important in their activation of neutrophils. Previous studies with the chemokine interleukin-8 (IL-8) had shown that the N- terminal region preceding the first cysteine residue was critical in defining neutrophil-activating properties. We examined whether NAP-2 and PF4 had similar structural requirements. In the Ale-glu-leu-arg (AELR) N-terminus of NAP-2, substitution of E or R abolished Ca2+ mobilization and elastase secretion. Unlike the parent molecule PF4, AELR/PF4, the hybrid formed by replacing the N-terminal sequence of PF4 before the first cysteine residue with the homologous sequence of NAP- 2, stimulated Ca2+ mobilization and elastase secretion. Furthermore, the effect of amino acid substitutions in the ELR motif differed from those seen with NAP-2 in that conserved substitutions of E or R in NAP- 2 abolished activity, but only reduced neutrophil activation in the hybrid. These studies show that just as with IL-8, the N-termini of NAP- 2 and PF4 are critical for high-level neutrophil-activating function. Desensitization studies provided information on receptor binding. NAP- 2, which binds almost exclusively to the type 2 IL-8 receptor (IL-8R), did not desensitize neutrophils to activation by IL-8 because IL-8 could bind to and activate via both type 1 and 2 IL-8R. AELR/PF4 appears to bind to both types of receptors because it desensitized neutrophils to NAP-2 activation; but was not desensitized by NAP-2, and because it desensitized to and was desensitized by IL-8. Thus, although NAP-2 and AELR/PF4 share approximately 60% amino acid homology, they have different receptor affinities. Studies were performed to define the role of the C-termini of these platelet chemokines in receptor binding. Heparin and a monoclonal antibody specific for the heparin- binding domain of PF4 both inhibited Ca2+ mobilization and elastase release, further suggesting that the C-terminus of these chemokines is important in receptor binding. Synthetic NAP-2(51-70) failed to mobilize Ca2+, whereas PF4(47-70) and PF4(58-70) induced Ca2+ mobilization and secretion of elastase at high concentrations. Pertussis toxin inhibited neutrophil activation by 40% to 50%, establishing a role for G-protein-coupled receptors such as the IL-8Rs in activation by the PF4 C-terminal peptides.(ABSTRACT TRUNCATED AT 400 WORDS)     

Impact of Implementing the 2013 ACC/AHA Cholesterol Guidelines on Vascular Events in a Statewide Community‐Based Practice Registry

Electronic health record data were analyzed to estimate the number of statin‐eligible adults with the 2013 American College of Cardiology/American Heart Association cholesterol guidelines not taking statin therapy and the impact of recommended statin therapy on 10‐year atherosclerotic cardiovascular disease (ASCVD₁₀) events. Adults aged 21 to 80 years in an outpatient network with ≥1 clinic visit(s) from January 2011 to June 2014 with data to calculate ASCVD₁₀ were eligible. Moderate‐intensity statin therapy was assumed to lower low‐density lipoprotein cholesterol by 30% and high‐intensity therapy was assumed to reduce low‐density lipoprotein cholesterol by 50%. ASCVD events were assumed to decline 22% for each 39 mg/dL decline in low‐density lipoprotein cholesterol. Among 411,768 adults, 260,434 (63.2%) were not taking statins and 103,478 (39.7%) were eligible for a statin, including 79,069 (76.4%) patients with hypertension. Estimated ASCVD₁₀ events were 18,781 without and 13,328 with statin therapy, a 29.0% relative and 5.3% absolute risk reduction with a number needed to treat of 19. The 2013 cholesterol guidelines are a relatively efficient approach to reducing ASCVD in untreated, statin‐eligible adults who often have concomitant hypertension.     

Principles and practice of HIV-protease inhibitor pharmacoenhancement

Continually maintaining maximally suppressive drug concentrations represents a key defence against the emergence of resistance. If drug levels fall and replication occurs, the opportunity for mutant virus to be selected occurs. It has been increasingly recognized that variability in the pharmacokinetics of antiretrovirals, particularly protease inhibitors (PIs), means that drug exposure is not always optimal, giving the virus a chance to replicate. A significant number of patients receiving PIs two or three times daily will have trough (C_trough or C_min) plasma concentrations, which are close to, or below, the plasma protein binding‐corrected inhibitory concentration (IC₅₀ or IC₉₅) during the dosing interval. It is primarily in this context that therapeutic drug monitoring of PIs has been proposed as an aid to patient management, to ensure that patients maintain adequate drug concentrations throughout the dosing interval. Ideally, an antiretroviral drug will have a pharmacokinetic (PK) profile that maintains drug levels well above the viral inhibitory concentration throughout the entire dosing interval. Beneficial drug–drug interactions have been shown to improve PI pharmacokinetics. Ritonavir (RTV) inhibits the key enzymes that limit the bioavailability or speed the metabolism of other PIs. It is therefore increasingly used for boosting and maintaining PI plasma concentrations. At low (100 mg twice a day) doses it acts as a pharmacoenhancer of indinavir (IDV), amprenavir, saquinavir, lopinavir and to a more limited degree nelfinavir. Using a pharmacoenhancer with a PI results in increased exposure to the PI, higher C_min levels, and in most cases prolonged elimination half‐lives. The long‐term clinical benefits of PK enhancing are unknown as are the long‐term toxicities, although the incidence of nephrolithiasis with IDV appears increased when IDV is combined with low‐dose RTV in HIV‐infected patients. Head‐to‐head clinical comparisons of boosted PI regimens will help answer some of the questions that remain with regard to PK enhancement.     

Ex vivo expansion with stem cell factor and interleukin-11 augments both short-term recovery posttransplant and the ability to serially transplant marrow

The characterization of many cytokines involved in the control of hematopoiesis has led to intense investigation into their potential use in ex vivo culture to expand progenitor numbers. We have established the optimum ex vivo culture conditions that allow substantial amplification of transient engrafting murine stem cells and which, simultaneously, augment the ability to sustain serial bone marrow transplantation (BMT). Short-term incubation of unfractionated BM cells in liquid culture with stem cell factor (SCF) and interleukin-11 (IL- 11) produced a 50-fold amplification of clonogenic multipotential progenitors (CFU-A). Following such ex vivo expansion, substantially fewer cells were required to rescue lethally irradiated mice. When transplanted in cell doses above threshold for engraftment, BM cells expanded ex vivo resulted in significantly more rapid hematopoietic recovery. In a serial transplantation model, unmanipulated BM was only able to consistently sustain secondary BMT recipients, but BM expanded ex vivo has sustained quaternary BMT recipients that remain alive and well more than 140 days after 4th degree BMT. These results show augmentation of both short-term recovery posttransplant and the ability to serially transplant marrow by preincubation in culture with SCF and IL-11.     

CD40 ligand triggered interleukin-6 secretion in multiple myeloma

Previous studies have suggested that interleukin-6 (IL-6) may mediate growth of multiple myeloma (MM) in either an autocrine or paracrine growth mechanism. However, those molecules which can trigger IL-6 secretion either by tumor cells or non-MM marrow cells are not well characterized. In the present study, we have examined the expression and functional significance of CD40 on MM and plasma cell leukemia (PCL) cells and derived cell lines, as well as long-term bone marrow stromal cells (BMSCs) and derived cell lines. CD40 was expressed on the majority of MM cells (> 90%) and BMSCs (> 70%). Triggering via CD40 using NIH3T3 CD40 ligand transfectant (CD40LT) cells increased (> 30%) cell surface CD80, CD18, CD11a, CD11b, and CD11c expression on MM cell lines. Culture with either fresh or paraformaldehyde fixed NIH3T3 CD40LT cells upregulates IL-6 secretion in MM cells and MM-derived cell lines, as well as normal and MM bone marrow mononuclear cells (BMMCs), BMSCs, and BMSC lines; this effect can be specifically blocked by anti- CD40 monoclonal antibody (MoAb). BMMCs and BMSCs from patients with MM secreted significantly more IL-6 than those from healthy donors (n = 3, P < .001); moreover, after stimulation using CD40L, IL-6 secretion was fourfold greater (n = 3, P < .001) from MM BMMCs and BMSCs than from normal BMMCs and BMSCs. Myeloma (CD38+CD45RA-) cells and non-MM (CD38+CD45RA+, CD38-CD45RA+, and CD38-CD45RA-) BMMCs were separated by dual fluorescence cell sorting. The latter secreted fourfold more IL-6 than the former (n = 2, P < .001). Increased IL-6 secretion (up to 28- fold) and proliferation (Stimulation index 10) by CD38+CD45RA-MM cells was triggered by culture with NIH3T3 CD40LT cells. Finally, anti- CD40MoAb partially (30%) blocked tumor cell to BMSC adhesion-induced IL- 6 secretion. These studies support the view that CD40L may trigger IL-6 secretion by both MM cells and BMSCs and that IL-6-mediated autocrine and paracrine growth mechanisms may be possible in MM.     

Ethnic and racial difference in Helicobacter pylori infection in patients with immune thrombocytopenia treated at a major urban medical center

Immune thrombocytopenia (ITP) is an autoimmune disorder with a complex immunopathology and pathogenesis characterized by thrombocytopenia and bleeding manifestations. The disorder is separated into primary (idiopathic) ITP and secondary ITP, when associated with other immune or lymphoproliferative disorders and certain chronic infections. Helicobacter pylori (H. pylori) is a recognized bacterial cause of ITP. In regions with high prevalence of infection, bacterial eradication has resulted in improvement in platelet count. However, the prevalence of H. pylori infection and response to antimicrobial therapy in North American ITP patients is reportedly low. We evaluated the prevalence of H. pylori infection in ITP patients diagnosed and treated at a large urban medical center. Eighty-two patients were screened for H. pylori, by stool antigen (n = 54), H. pylori breath test (n = 11), and H. pylori antibodies (n = 16), of which 15 (18.3%) were white non-Hispanic (WNH), 55 (67%) Hispanic (H), 8 (9.8%) Asian (A), and 4 (4.9%) African-American (AA). Of the screened patients, 36/82 (43.9%) tested positive for H. pylori. The prevalence of H. pylori infection within the represented ethnic groups was 2/15 (13%) WNH, 29/55 (52.7%) H, 3/8 (37.5%) A, and 2/4 (50%) AA. There was a significant difference in prevalence of infection comparing WNH and H patients (p = 0.007). There were 36 treated patients, with H. pylori eradication documented in 26 patients. Fifteen of the 26 patients were evaluable for response with 8 of 15 (53%) having clinical responses, 6 complete responses, and 2 partial responses. Our study demonstrates an increased prevalence of H. pylori infection in the Hispanic ITP population with a reasonable platelet response among patients with H. pylori eradication.