Antiviral response and HIV-1 inhibition in sickle cell disease.

Sickle cell disease (SCD) is characterized by hemolysis, vaso-occlusion, and ischemia. HIV-1 infection was previously shown to be suppressed in SCD PBMCs. Here, we report that HIV-1 suppression is attributed to the increased expression of iron, hypoxia, and interferon-induced innate antiviral factors. Inhibition of upregulated antiviral genes, HMOX-1, CDKN1A, and CH25H, increased HIV-1 replication in SCD PBMCs, suggesting their critical role in HIV-1 suppression. Levels of IFN-ß were elevated in SCD patients. Sickle cell hemoglobin (HbS) treatment of THP-1-derived and primary monocyte-derived macrophages induced production of IFN-ß, upregulated antiviral gene expression, and suppressed HIV-1 infection. Infection with mouse-adapted EcoHIV was suppressed in the SCD mice that also exhibited elevated levels of antiviral restriction factors. Our findings suggest that hemolysis and release of HbS leads to the induction of IFN-ß production, induction of cellular antiviral state by the expression of iron and IFN-driven factors, and suppression of HIV-1 infection.

Cerebral artery conditional blood velocity in sickle cell disease: a multicentre study and evidence for active treatment.

OBJECTIVE: To obtain multicentre data on the prevalence of normal, high or conditional (intermediate) blood velocity in the cerebral arteries among children with sickle cell disease (SCD) in Nigeria. DESIGN: A prospective observational study in five tertiary healthcare institutions. By transcranial Doppler (TCD) ultrasonography, cerebral artery peak systolic blood velocity (PSV) was determined in 193 children with SCD and time averaged mean of the maximum blood velocity (TAMMV) in a different cohort of 115 children. This design was to make the findings relevant to hospitals with TCD equipment that measure either PSV or TAMMV. SETTING: Nigeria. PARTICIPANTS: 308 children (126 girls, 182 boys; age 2-16 years). MAIN OUTCOME MEASURES: Percentage of children with SCD who have normal, high or intermediate (often termed conditional) PSV or TAMMV. RESULTS: In the cohort of 193 children, PSV was normal in 150 (77.7%), high in 7 (3.6%) and conditional in 36 (18.7%). In the cohort of 115 children, TAMMV was normal in 96 (84%), high in 7 (6%) and conditional in 12 (10%). There were no significant differences in gender or age distribution between the PSV and TAMMV cohorts. Altogether, cerebral artery blood velocity was normal in 246/308 children (80%), high in 14 (4.5%) and conditional in 48 (15.5%). CONCLUSION: Since conditional blood velocity in cerebral arteries can progress to high values and predispose to stroke, the proportion of children with SCD who are affected (15.5%) raises the question of whether regular monitoring and proactive intervention ought to be the standard of care.

Plasma concentration of fucosyltransferase 7 is not associated with the number of clinically overt vaso-occlusive events in sickle cell disease.

Objective: To determine if the number of vaso-occlusive events in SCD relates to plasma concentration of fucosyltransferase 7 (FUT7), which catalyses the synthesis of selectin ligands. Design: A prospective, analytical study. Setting: Haematology and Chemical Pathology Departments of tertiary healthcare centres. Participants: Steady state HbSS individuals aged 13-45 years, 20 had 3 or more vaso-occlusive crises that required hospital admission in the previous year (with or without complications of SCD); 17 other HbSS persons had 0-1 vaso-occlusive crisis that required hospital admission in the previous year and no disease complications. Intervention: Steady-state plasma concentrations of FUT7 measured by ELISA were compared between SCD patients who had one vaso-occlusive crisis requiring hospital treatment in the previous year but no disease complications and those who had >3 crises with or without complications. Main Outcome Measures: Plasma level of FUT7and the number of vaso-occlusive events in each HbSS patient. Results: Mean + standard deviation plasma concentration of FUT7 was 8.6 + 2.7 ng/ml in patients with >3 vasoocclusive crises in the previous year and 7.3 + 1.7 ng/ml in those with 0-1 crisis and no complications; independent sample t-test, p > 0.05, not significantly different. Conclusion: Plasma concentration of fucosyltransferase7 is not associated with the number of vaso-occlusive events in sickle cell disease. Funding: None declared.

Prevalence of venous thromboembolism and its associations in a large racially homogenous population of sickle cell disease patients.

To determine the prevalence of venous thromboembolism (VTE) among adult sickle cell disease (SCD) patients in Nigeria. METHODS: This was a multicentre retrospective study in which the medical records of adult SCD patients were reviewed. Information on demographics, steady-state haemogram, clinical phenotypes, duration of follow-up, history of VTE including risk factors and management was collected. RESULTS: Of the 509 SCD patients with a median (IQR) duration of follow-up of 2 years, 10 (2.0%) had VTE (9 DVT and 1 PE). Their median (IQR) age was 27 (22.8-30.3) years. Identifiable risk factors for VTE included positive family history (2, 20%) surgery, splenectomy, paraplegia and cancer (1, 10% each). No risk factor was identifiable in four persons. VTE had no significant association with age and gender. VTE was significantly associated with the following events: acute chest syndrome [p = .002, odds ratio (OR) 8, 95% CI 2.2-28.9], osteonecrosis [p = .012, OR 5.24, 95% CI, 1.45-18.91] and vaso-occlusive crisis [p = .035]. Also significantly associated with VTE were pulmonary hypertension [p = .001, OR 23.3, 95%CI 5.18-105.06] and stroke [p = .032, OR 9.35, 95%CI 0.87-53.25]. CONCLUSION: The prevalence of VTE among SCD patients in Nigeria is low. It is significantly associated with vaso-occlusive crisis, pulmonary hypertension and stroke.

Effect of Sickle Cell Trait on Human Immunodeficiency Virus Type 1 Infection.

Introduction: Whereas several studies show that homozygous (HbSS) sickle cell disease protects against human immunodeficiency virus infection, it is not clear if human immunodeficiency virus infection is affected by the heterozygous state of the sickle globin gene (HbAS or sickle cell trait). Objective: To evaluate the effects of sickle cell trait on the prevalence and severity of human immunodeficiency virus type 1 infection in a large patient population. Methods: Hemoglobin genotype was determined by high performance liquid chromatography (HPLC) in 1,226 HIV-1 patients in Nigeria. Their demographic data were documented. Blood CD4+ cell counts and HIV-1 viral load previously determined on the same blood samples to guide clinical care were used as indices of severity of HIV-1 infection. Statistical analysis of the data was done to evaluate the effects of sickle cell trait on the severity and prevalence of HIV-1 infection, relative to the prevalence of 1.4% in the general population of Nigeria. Results and Discussion: The distribution of hemoglobin genotypes among the HIV-1 patients was comparable to that in the general population of Nigeria (Chi-squared statistic =1.025; p value = 0.31, not significant). Neither viral load (p = 0.32) nor blood CD4+ cell count (p = 0.30) was significantly different between all HbAS versus all HbAA patients. There was a trend towards lower viral load in females and a significant interaction between gender and HbAS for viral load (P = 0.018), suggesting that sickle cell trait might be associated with the severity of HIV-1 infection in females. Conclusion: The findings suggest that sickle cell trait might be associated with severity of HIV-1 infection in female, but not all, patients. Larger, prospective studies are required to further investigate the effect of sickle cell trait on HIV-1 infection.

Plasma Concentration of 12-Hydroxyeicosatetraenoic Acid, Single Nucleotide Polymorphisms of 12-Lipooxygenase Gene and Vaso-Occlusion in Sickle Cell Disease.

Background and Novel Aspect of this Work: In the light of previous findings that inflammation predisposes to intercellular adhesion and microvascular occlusion in sickle cell disease (SCD), this study investigated the relationship between the number of vaso-occlusive events in SCD, plasma levels of the pro-inflammatory molecules 12-Hydroxyeicosatetraenoic acid (12-HETE), TNF-α and IL-1ß; and single nucleotide polymorphisms (SNPs) in the gene 12-Lipooxygenase (ALOX-12), which encodes the enzyme 12-Lipoxygenase that catalyzes the biosynthesis of 12-HETE. Objective: To evaluate the relationship between vaso-occlusion in SCD and plasma concentrations of 12-HETE, TNF-α, and IL-1ß; and single nucleotide polymorphisms (SNPs) in ALOX-12 gene. Participants and Methods: In 50 HbSS patients, the numbers of vaso-occlusive crisis requiring hospital treatment in the previous 1 year and the vaso-occlusive complications of SCD developed to date (e.g stroke) were added to obtain the vaso-occlusive events (VOE) score. In the HbSS patients and 30 healthy sibling control persons, plasma concentrations of 12-HETE, TNF-α and IL-1ß were measured by ELISA, the ALOX12 SNPs rs2073438 and rs1126667 detected by DNA sequencing, and the accrued data statistically analyzed. Results: Compared to SCD patients with VOE score 0-1, those with scores ≥3 had higher plasma levels of 12-HETE (p < 0.0001) and TNF-α (p = 0.19), but not IL-1ß (p = 0.27). VOE score showed strong direct correlation with plasma level of 12-HETE (r = 0.65, p < 0.0001), but not with TNF-α nor IL-1ß. Neither VOE score nor plasma concentration of 12-HETE showed any relationship with the ALOX12 SNPs rs2073438 and rs1126667. Conclusion: The strong direct correlation of VOE score with plasma concentration of 12-HETE suggests that the clinical relevance of this pro-inflammatory molecule in SCD-associated vaso-occlusion needs to be evaluated in further studies.

Pilot assessment of omega-3 fatty acids and potassium thiocyanate in sickle cell anemia patients with conditional peak systolic cerebral artery blood velocity.

OBJECTIVE: The purpose of this pilot study was to explore the effect of omega-3 fatty acids and potassium thiocyanate on conditional peak systolic cerebral artery blood velocity in children with sickle cell anemia (SCA). METHODS: Transcranial doppler ultrasonography (TCD) was done on 232 SCA children, and 21 found with conditional peak systolic blood velocity (PSV) of 200-249 cm/s in internal carotid, middle or anterior cerebral arteries. These were randomized to receive omega-3 fatty acids and potassium thiocyanate with standard treatment of SCA (test group, N = 14), or standard treatment only (control group, N = 7). After 3 months of treatment, PSV was measured again. RESULTS: Right middle cerebral artery PSV was significantly reduced in the test relative to the control groups (p = 0.04). PSV returned to normal in 79% of the test versus 43% of the control group; and increased to abnormal in one member of the control group, but none of the test group. CONCLUSIONS: The pilot data suggest that in SCA, omega-3 fatty acids and potassium thiocyanate might reduce conditional blood velocity to normal, or prevent progression to abnormal values. A larger, randomized, clinical trial is required to further address the current gap in management of conditional TCD blood velocity.

Clinical and Laboratory Predictors of Frequency of Painful Crises among Sickle Cell Anaemia Patients in Nigeria.

INTRODUCTION: The severity of Sickle Cell Anaemia (SCA) in terms of frequency of painful Vaso-Occlusive Crises (VOC) may be affected by clinical and haematological parameters amongst others. Elucidation of these factors in a given disease prevalent environment is necessary for prompt and effective management of patients with frequent painful VOC. AIM: This study aimed at determining the clinical and laboratory predictors of frequency of painful VOC among SCA patients in Enugu, Southeastern Nigeria. MATERIALS AND METHODS: It was a cross-sectional study of 100 consecutive SCA patients receiving care at the University of Nigeria Teaching Hospital, Enugu, Nigeria between May 2012 and February 2014. The eligible patients were categorized into two groups namely; Group A and Group B. Group A/study group (severe disease) comprised SCA patients who had experienced three or more painful crises (≥3 crises) in the last one year preceding the study but, currently in steady state, while Group B/control group (mild-moderate disease), comprised SCA patients matched for age, sex, highest educational status, and occupation but who have had no painful crisis or had only one or two painful crises (0-2 crises) in the last one year preceding the study and currently in steady state. RESULTS: The overall mean age of the patients was 18.4±12.2 (range=2-52) years. The mean values of the haematological parameters including haemoglobin concentration, white cell count, platelet count, and neutrophil count were significantly higher in those with severe crises than mild-moderate crises (p<0.05). Sickle cell related complications including Avascular Necrosis (AVN) and leg ulcers were significantly higher in the study group than the control group (p<0.05). CONCLUSION: There was significant association between the frequency of crises and haemogblobin level, platelet and neutrophil counts and some clinical parameters: AVN, nephropathy and stroke. Future preventive interventions for reduction in frequency of crisis amongst patients with SCA could be targeted at controlling the blood levels of the identified haematological parameters.

Investigational selectin-targeted therapy of sickle cell disease.

INTRODUCTION: Under conditions of blood flow, selectins mediate the intercellular adhesion between erythrocytes, leukocytes, platelets and vascular endothelium that contribute to vaso-occlusion and tissue damage in sickle cell disease (SCD). Therefore, selectin antagonists have the potential to ameliorate SCD. AREAS COVERED: In this review, the author discusses the cellular and molecular basis of vaso-occlusion in SCD, and presents evidence that selectin-mediated cell adhesion has clinical importance in this disorder. The author discusses molecular structure of human selectins and their physiological ligands and highlights clinical trials of selectin-targeted therapy of SCD. Herein, the author also assesses the benefits and limitations of the selectin antagonists that are currently under evaluation for SCD, and offers suggestions for the future. EXPERT OPINION: In Phase I and II clinical trials, rivipansel and heparin demonstrated promising efficacy and safety in SCD. Although selectin blockade could potentially impair immune response, an increased incidence of infection was not reported in SCD patients treated with heparin (n = 127) or rivipansel (n = 111). The efficacy and safety findings from Phase I and II clinical studies are encouraging the commencement of Phase III studies to further evaluate selectin-targeted therapy in SCD.

Addition of multimodal therapy to standard management of steady state sickle cell disease.

Most people on folic acid to boost erythropoiesis and prophylactic antimicrobials, the standard management of steady state sickle cell disease (SCD), have unacceptable numbers of crises. The objective of this study was to evaluate the effects of adding multimodal therapy with potassium thiocyanate and omega-3 fatty acids to the standard management of steady state SCD. Pre- and post-treatment numbers of crises and other disease indices were compared in 16 HbSS individuals on folic acid and paludrine after 12 months of adding eicosapentaenoic acid 15 mg/kg/day, docosahexaenoic acid 10 mg/kg/day, and potassium thiocyanate 1-2 mL/day, each milliliter of which contained 250 mg of thiocyanate and 100 micrograms of iodine to prevent hypothyroidism: a possible side-effect due to competitive inhibition of the transport of iodide into the thyroid gland by thiocyanate. Median number of crises reduced from 3/yr to 1/yr (P < 0.0001). There was no evidence of impaired thyroid function. Plasma level of tri-iodothyronine improved (P < 0.0001). Steady state full blood count and bilirubin level did not change significantly. The findings suggest that addition of potassium thiocyanate and eicosapentaenoic and docosahexaenoic acids to standard management of steady state SCD reduces the number of crises. This observation needs to be evaluated in larger studies.

Increased prevalence of activated protein C resistance during pregnancy may implicate venous thrombo embolic disorders as a common cause of maternal mortality in Nigeria

Background: Acquired resistance to protein C in pregnancy has been established as one of the factors associated with thromboembolic phenomenon, an important cause of maternal mortality and morbidity. Objectives: To establish the mean levels of PCA ratio (measure of protein C resistance) of among our pregnant women since maternal mortality rate of the country is on the increase despite efforts to reduce this trend. Materials and Methods: A prospective study was carried out in a tertiary institution in Enugu State, Southeastern Nigeria over the 7 months period from May 2010 to November 2010. Two hundred pregnant women and 50 non pregnant female controls were recruited and PCA ratio, (coagulometric assay) were determined. Results: There was a non significant difference between the mean and standard deviation PCA ratio of the female non pregnant controls and pregnant women in 2nd trimester 4.32±0.4 and 4.30±0.4 respectively. A significant difference was noted between the controls and pregnant women in 3rd trimester 4.32±0.4 and 3.87±0.5 respectively also between the pregnant women in their 2nd and 3rd trimester 4.30±0.4 and 3.87±0.5 respectively. Conclusion: There is increased protein resistance C in our pregnant women. This may implicate thromboembolic disorders as one of the leading causes of increase maternal mortality despite a downward trend in the prevalence of post partum haemorrhage

Pilot study of omega-3 fatty acid supplements in sickle cell disease.

In a previous retrospective study, it was observed that the greater the amounts of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the blood, the lesser the number of complications of sickle cell disease (SCD) and the higher the steady state haemoglobin level. SCD causes ischaemia-reperfusion injury and inflammation; which can be ameliorated by a metabolite of DHA that down-regulates expression of pro-inflammatory genes. The objectives of this prospective pilot study were to evaluate the effects of DHA and EPA supplements in SCD, and test the hypothesis that these effects are mediated partly by reducing inflammation. Oral DHA and EPA supplements were given to 16 SCD patients for 6 months. We then compared pre- and post-supplementation values of number of crisis, steady state Hb, plasma unconjugated bilirubin and three indices of inflammation: plasma interleukin-6, blood neutrophil and platelet counts. There was a significant reduction in the plasma level of unconjugated bilirubin, and the number of sickle cell crisis; but not in the markers of inflammation. The pilot data suggest that DHA and EPA supplements reduce the number of crisis and steady state haemolysis in SCD; but provide no evidence that these effects are mediated by reducing inflammation.

Height, weight, body mass index and ocular biometry in patients with sickle cell disease.

PURPOSE: To investigate the effects of physical size on refractive error and the dimensions of optical components in sickle cell disease (SCD). METHODS: The design was cross sectional. Height and weight of adult patients suffering from SCD were measured, and body mass index (BMI) was calculated. Anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD) and axial length (AL) were measured using A-scan ultrasonography. Corneal radius of curvature (CR) was measured using a keratometer. Non-cycloplegic refractive error was determined subjectively. RESULTS: Subjects with SC genotype were significantly taller than those with SS genotype. In the unadjusted data, height was correlated with VCD [p = 0.02, 0.44 mm deeper per 10 cm increase in height, 95% CI (0.65, 8.25)] and AL [p = 0.03, 0.42 mm longer for every 10 cm increase in height, 95%CI (0.49, 7.99)]. The relationship between height, VCD and AL was absent after adjustment for age, gender, genotype and weight. BMI (kg m(-2)) was correlated with AL/CR ratio in both unadjusted (p = 0.04, -0.10 decrease per 1 kg m(-2), 95% CI (-0.018, -0.001) and adjusted data (p = 0.05, -0.10 decrease per 10 kg m(-2), 95% CI (-0.0189, 0.0001). Refractive error was not related to height, weight or BMI. CONCLUSIONS: Physical size does not affect refractive error or optical components in adult patients with SCD.

Patients with sickle cell disease have reduced blood antioxidant protection.

In previous studies, we found that homozygous sickle cell (HbSS) patients, compared with their healthy (HbAA) counterparts, had reduced levels of the omega-3 fatty acids, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, in red cells, platelets, and mononuclear cells. These differences were not due to lower intake of the two fatty acids. We have investigated whether reduced antioxidant status in the patients could help explain the observed phenomenon. Blood specimens previously obtained for fatty acid study from Nigerian (26 HbSS and 30 HbAA) and British (30 HbSS, 9 sickle cell-hemoglobin C/HbSC, and 15 HbAA) subjects were analyzed for antioxidant status. The Nigerian HbSS patients compared with the controls had lower plasma retinol, alpha-tocopherol, and beta-carotene concentrations (p < 0.005) and reduced activity of red cell Cu/Zn-superoxide dismutase (Cu/Zn-SOD) (p < 0.05). Similarly, the British HbSS group had reduced concentrations of plasma alpha-tocopherol (p < 0.005), and activities of red cell Cu/Zn-superoxide dismutase (p < 0.05) and Se-glutathione peroxidase (Se-GPx) (p < 0.005) than the controls. In addition, the British patients in comparison with those who had HbSC, a mild form of the disease, had lower alpha-tocopherol than that of the HbAA controls (p < 0.005). In the British sickle cell patients, there was a positive correlation between red cell ethanolamine phosphoglyceride (EPG) DHA and Cu/Zn-SOD activity (r = 0.700, p < 0.05), choline phosphoglyceride (CPG) DHA and Se-GPx activity (r = 0.605, p < 0.05), and CPG EPA and Se-GPx activity (r = 0.558, p > 0.05). Similarly, the percent DHA in red cell EPG was positively related with the activity of Se-GPx in the patients with HbSC (r = 0.674, p < 0.05). These findings suggest that the lower levels of membrane EPA and DHA in blood cells of the HbSS patients could be due to peroxidation resulting from a compromised antioxidant competence.

The linear effects of alpha-thalassaemia, the UGT1A1 and HMOX1 polymorphisms on cholelithiasis in sickle cell disease.

Serum bilirubin levels and predisposition to gallstones in sickle cell disease (SCD) are influenced by genetic variation in the hepatic uridine diphosphate (UDP)-glucuronosyltransferase (UGT1A1) gene, but the association is not consistent. This study investigated whether variation in the gene encoding haem oxygenase (HMOX1), a rate-limiting enzyme upstream of UGT1A in the haem catabolic pathway, and alpha-thalassaemia could explain some of the inconsistent effects. The UGT1A1 [TA](n) and HMOX1 [GT](n) promoter polymorphisms and alpha globin genotypes were determined in 263 SCD patients (199 HbSS, 5 HbS/beta(0), 59 HbSC). Detection of gallstones was based on ultrasound of the liver/biliary tree. Regression analysis showed that serum bilirubin levels and the incidence of gallstones were strongly associated with the number of UGT1A1 [TA] repeats in all subjects (P < 0.0001 and P < 0.01, respectively). While HMOX1 genotype had no effect, co-inheritance of alpha-thalassaemia reduced serum bilirubin levels in all SCD patients independently of the number of UGT1A1 [TA] repeats. Each additional [TA] repeat is associated with an increase in mean serum bilirubin levels of 21% and cholelithiasis risk of 87% in SCD.

A randomised comparison of deferasirox versus deferoxamine for the treatment of transfusional iron overload in sickle cell disease.

Deferasirox is a once-daily, oral iron chelator developed for treating transfusional iron overload. Preclinical studies indicated that the kidney was a potential target organ of toxicity. As patients with sickle cell disease often have abnormal baseline renal function, the primary objective of this randomised, open-label, phase II trial was to evaluate the safety and tolerability of deferasirox in comparison with deferoxamine in this population. Assessment of efficacy, as measured by change in liver iron concentration (LIC) using biosusceptometry, was a secondary objective. A total of 195 adult and paediatric patients received deferasirox (n = 132) or deferoxamine (n = 63). Adverse events most commonly associated with deferasirox were mild, including transient nausea, vomiting, diarrhoea, abdominal pain and skin rash. Abnormal laboratory studies with deferasirox were occasionally associated with mild non-progressive increases in serum creatinine and reversible elevations in liver function tests. Discontinuation rates from deferasirox (11.4%) and deferoxamine (11.1%) were similar. Over 1 year, similar dose-dependent LIC reductions were observed with deferasirox and deferoxamine. Once-daily oral deferasirox has acceptable tolerability and appears to have similar efficacy to deferoxamine in reducing iron burden in transfused patients with sickle cell disease.

White blood cell count as a predictor of the severity of sickle cell disease during pregnancy.

OBJECTIVE: Increasing epidemiological evidence implicates leukocytosis as a major risk factor for poor outcome in non-pregnant sickle cell disease (SCD) patients. The aim of this study was to investigate whether steady-state white blood cell (WBC) count can predict SCD-related problems in pregnancy. DESIGN: Retrospective observational study of 40 SCD pregnant women who had their antenatal care at Guy's & St Thomas' NHS Trust, London. Twenty-six women developed clinical complications related to SCD during their pregnancy (painful crisis, chest symptoms, infections, severe anaemia requiring blood transfusion, pre-eclampsia, and/or thromboembolism) and 14 remained asymptomatic. The steady-state leukocyte counts early in pregnancy were compared between the two groups and receiver operator characteristics (ROC) curve was plotted for different values of WBC. RESULTS: Compared to asymptomatic patients, women who developed SCD-related complications had significantly higher total WBC count [11.2 x 10(9)L(-1) (SD 3.22) versus 8 x 10(9)L(-1) (2.8), p<0.01], higher lymphocyte count [3 x 10(9)L(-1) (1.62) versus 1.6 x 10(9)L(-1) (0.65), p<0.01] and higher monocyte count [0.8 x 10(9)L(-1) (0.47) versus 0.4 x 10(9)L(-1) (0.21), p<0.01]. The neutrophil count showed a similar trend but the difference did not reach statistical significance [6.6 x 10(9)L(-1) (2.29) versus 5.7 x 10(9)L(-1) (2.15), p=0.22]. The area under the ROC curve was 74% (95% CI: 56-92). CONCLUSION: WBC count early in pregnancy was significantly higher in women who subsequently developed clinical problems related to SCD. The WBC may be used as a predictor of the severity of SCD in pregnancy.

Investigational agents for sickle cell disease.

Developments in the treatment of sickle cell disease (SCD) have not kept pace with advances in understanding the pathophysiology of this haemoglobinopathy. Drugs undergoing preclinical and clinical assessment for the therapy of these globin gene disorders are discussed in this article. Beginning with investigational agents for treatment of SCD as a whole, the discussion proceeds to drugs being developed for specific manifestations or iatrogenic complications. Despite being licensed in the USA, the prototype antisickling agent, hydroxycarbamide, has not attained worldwide clinical use because of concerns about long-term toxicity. The less toxic decitabine, which (as with hydroxycarbamide) increases fetal haemoglobin level, cannot be administered orally; therefore, the search continues for effective and safe antisickling drugs that can be taken orally. The naturally occurring benzaldehyde 5-hydroxymethyl-2-furfural has shown promising antisickling properties in vitro, and when administered to transgenic sickle mice. These effects are surpassed by the new synthetic pyridyl derivatives of benzaldehyde. Studies in humans with SCD are required to assess the clinical efficacy of these benzaldehydes. Niprisan, another antisickling agent with significant clinical efficacy and an attractive safety profile, is undergoing further development. The prospects of antiadhesion therapy in SCD are demonstrated by a recombinant protein containing the Fc fragment of IgG fused to the natural ligand for selectins: the conjugate significantly inhibited blood vessel occlusion in transgenic sickle mice. Whereas the orally administrable iron-chelating agent deferasirox is likely to increasingly take the place of desferioxamine (which can only be given parenterally), effective treatment of priapism in SCD remains a distressing challenge.

Abnormality of erythrocyte membrane n-3 long chain polyunsaturated fatty acids in sickle cell haemoglobin C (HbSC) disease is not as remarkable as in sickle cell anaemia (HbSS).

Sickle cell disease (SCD) is a group of inherited blood disorders in which clinical illness results from the presence of erythrocytes with sickled haemoglobin (HbS). Blood vessel occlusion is a fundamental pathological process in SCD. Sickle cell haemoglobin C (HbSC) disease and sickle cell anaemia (HbSS) share some pathophysiology and clinical manifestations. However, the former is generally less severe. Erythrocytes of HbSC patients have longer life span, reduced haemolysis, and lower propensity to adhere to vascular endothelium than those of their HbSS counterparts. The structure and function of erythrocytes are strongly modulated by membrane long chain polyunsaturated fatty acids (LCPUFA). We have tested the possibility that HbSC and HbSS patients have different membrane fatty acid composition consistent with the difference in their clinical severity. Steady-state patients, 9 HbSC and 28 HbSS, and 15 HbAA were studied. The HbSC patients had a higher level of linoleic (LA, P<0.05) and docosahexaenoic (DHA, P<0.05) acids, and lower arachidonic acid (AA, P<0.01) and AA/eicosapentaenoic acid (EPA) ratio (P<0.05) in erythrocyte choline phosphoglycerides (CPG) compared with the HbSS group. Similarly, the level of EPA was higher and AA/EPA ratio (P<0.01) lower in serine phosphoglycerides of the HbSC patients. In contrast to the HbSC, the HbSS group had lower levels of EPA (P<0.001), DHA (P<0.05), total n-3 metabolites and total n-3 fatty acids (P<0.001) in erythrocyte CPG compared with the healthy HbAA controls. Moreover, the HbSS patients with disease complications compared with those without complications had reduced DHA and total n-3 fatty acids (P<0.005) in erythrocyte CPG. The abnormalities in erythrocyte in LCPUFA which is manifested by an increase in AA and a decrease in EPA and DHA in HbSS relative to HbSC disease observed in this study are consistent with the contrast in clinical severity between the two entities.

Leukocyte adhesion and the pathophysiology of sickle cell disease.

PURPOSE OF REVIEW: This article discusses the importance of leukocyte adhesion in sickle cell disease, and how this could be modulated for clinical benefit. RECENT FINDINGS: Recurrent inflammation and vasculopathy occur in sickle cell disease. As a result, leukocytes and vascular endothelial cells are activated and increase their expression of adhesion molecules. Adhesion of leukocytes to other blood cells and endothelium contributes to vaso-occlusion in sickle cell disease. High-level expression of adhesion molecules by leukocytes is associated with clinically severe disease. Pancellular membrane lipid abnormalities, including reduced proportions of omega-3 fatty acids, occur in sickle cell disease. These lipid abnormalities are more severe in patients with disease complications and in those with a greater degree of anaemia. Since lipid constitution of cell membranes affects surface expression of adhesion molecules, the above findings could account for earlier observations that omega-3 fatty acids reduce P-selectin expression and reduce the frequency of sickle cell crisis. By inhibition of nuclear factor kappaB, glucocorticoids reduce activation of vascular endothelial cells, their expression of ligands for leukocyte adhesion molecules, and vaso-occlusion. Monoclonal antibodies to vascular endothelial intercellular adhesion molecule-1 inhibited hypoxia-induced vaso-occlusion in transgenic sickle mice. SUMMARY: Although hydroxyurea and glucocorticoids reduce adhesion molecule expression by leukocytes and vascular endothelial cells, cytotoxicity and systemic side effects dampen enthusiasm for their use in sickle cell disease. Omega-3 fatty acids have shown promising efficacy and safety in pilot studies. A large clinical trial of these naturally occurring substances is required.