A Randomized Placebo-Controlled Efficacy Study of a Prime Boost Therapeutic Vaccination Strategy in HIV-1-Infected Individuals: VRI02 ANRS 149 LIGHT Phase II Trial.

In this placebo-controlled phase II randomized clinical trial, 103 human immunodeficiency virus type 1 (HIV-1)-infected patients under cART (combined antiretroviral treatment) were randomized 2:1 to receive either 3 doses of DNA GTU-MultiHIV B (coding for Rev, Nef, Tat, Gag, and gp160) at week 0 (W0), W4, and W12, followed by 2 doses of LIPO-5 vaccine containing long peptides from Gag, Pol, and Nef at W20 and W24, or placebo. Analytical treatment interruption (ATI) was performed between W36 to W48. At W28, vaccinees experienced an increase in functional CD4+ T-cell responses (P < 0.001 for each cytokine compared to W0) measured, predominantly against Gag and Pol/Env, and an increase in HIV-specific CD8+ T cells producing interleukin 2 (IL-2) and tumor necrosis factor alpha (TNF-α) (P = 0.001 and 0.013, respectively), predominantly against Pol/Env and Nef. However, analysis of T-cell subsets by mass cytometry in a subpopulation showed an increase in the W28/W0 ratio for memory CD8+ T cells coexpressing exhaustion and senescence markers such as PD-1/TIGIT (P = 0.004) and CD27/CD57 (P = 0.044) in vaccinees compared to the placebo group. During ATI, all patients experienced viral rebound, with the maximum observed HIV RNA level at W42 (median, 4.63 log10 copies [cp]/ml; interquartile range [IQR], 4.00 to 5.09), without any difference between arms. No patient resumed cART for CD4 cell count drop. Globally, the vaccine strategy was safe. However, a secondary HIV transmission during ATI was observed. These data show that the prime-boost combination of DNA and LIPO-5 vaccines elicited broad and polyfunctional T cells. The contrast between the quality of immune responses and the lack of potent viral control underscores the need for combined immunomodulatory strategies. (This study has been registered at ClinicalTrials.gov under registration no. NCT01492985.)IMPORTANCE In this placebo-controlled phase II randomized clinical trial, we evaluated the safety and immunogenicity of a therapeutic prime-boost vaccine strategy using a recombinant DNA vaccine (GTU-MultiHIV B clade) followed by a boost vaccination with a lipopeptide vaccine (HIV-LIPO-5) in HIV-infected patients on combined antiretroviral therapy. We show here that this prime-boost strategy is well tolerated, consistently with previous studies in HIV-1-infected individuals and healthy volunteers who received each vaccine component individually. Compared to the placebo group, vaccinees elicited strong and polyfunctional HIV-specific CD4+ and CD8+ T-cell responses. However, these immune responses presented some qualitative defects and were not able to control viremia following antiretroviral treatment interruption, as no difference in HIV viral rebound was observed in the vaccine and placebo groups. Several lessons were learned from these results, pointing out the urgent need to combine vaccine strategies with other immune-based interventions.

Planning HIV therapy to prevent future comorbidities: patient years for tenofovir alafenamide.

Since the introduction of suppressive antiretroviral therapy (ART), HIV has become a chronic disease, with infected people in high-income countries approaching similar life expectancy to the general population. As this population ages, an increasing number of people with HIV are living with age-, treatment-, and disease-related comorbidities. Lifestyle factors such as smoking, alcohol abuse, and substance misuse have a role in age-related comorbidity. Some degree of immune dysfunction is suggested by the presence of markers of immune activation/inflammation despite effective suppression of HIV replication. Cumulative exposure to some antiretroviral drugs contributes to HIV-associated comorbidities, with risk increasing with age. Specifically, tenofovir disoproxil fumarate (TDF), ritonavir-boosted atazanavir, and ritonavir-boosted lopinavir are associated with renal impairment, and TDF is known to cause loss of bone mineral density. Tenofovir alafenamide (TAF) was developed to improve on the safety profile of TDF, while maintaining its efficacy. TAF has better stability in plasma, and higher intracellular accumulation of tenofovir diphosphate in target cells, which has resulted in improved antiviral activity at lower doses with improved renal and bone safety. TAF has been studied extensively in randomized clinical trials and real-world studies. TAF-based regimens are recommended over TDF-containing regimens for the improved safety profile.

Low incidence of acute rejection within 6 months of kidney transplantation in HIV-infected recipients treated with raltegravir: the Agence Nationale de Recherche sur le Sida et les Hépatites Virales (ANRS) 153 TREVE trial.

OBJECTIVES: High rates of clinical acute rejection after kidney transplantation have been reported in people living with HIV (PLHIV), probably as a consequence of drug interactions. We therefore investigated the incidence of acute rejection within 6 months of transplantation in HIV-infected recipients treated with a protease-inhibitor-free raltegravir-based regimen. METHODS: The Agence Nationale de Recherche sur le Sida et les Hépatites Virales (ANRS) 153 TREVE (NCT01453192) study was a prospective multicentre single-arm trial in adult PLHIV awaiting kidney transplantation, with viral load < 50 HIV-1 RNA copies/mL, CD4 T-cell count > 200 cells/µL, and HIV-1 strains sensitive to raltegravir, aiming to demonstrate 6-month clinical acute rejection rates < 30%. Time to transplantation was compared with that for uninfected subjects matched for age, sex and registration date. RESULTS: In total, 61 participants were enrolled in the study, and 26 underwent kidney transplantation. Two participants experienced clinical acute rejection, corresponding to an estimated clinical acute rejection rate of 8% [95% confidence interval (CI) 2-24%] at 6 and 12 months post-transplantation. HIV infection remained under control in all but one participant, who temporarily stopped antiretroviral treatment. Median time to transplantation was longer in PLHIV than in controls (4.3 versus 2.8 years, respectively; P = 0.002) and was not influenced by blood group. CONCLUSIONS: Acute rejection rates were low after kidney transplantation in PLHIV treated with a raltegravir-based regimen. However, PLHIV have poorer access to transplantation than HIV-uninfected individuals after registration on the waiting list.

Hospitalization of HIV positive patients: Significant demand affecting all hospital sectors.

BACKGROUND: In a context of the evolution of severe morbidities in patients living with HIV (PLWH), the aim of this study was to describe reasons for hospitalization and the mode of care for the patients requiring hospitalization. METHODS: All admissions (≥24h) of PLWH to 10 hospitals in the south of Paris (COREVIH Ile-de-France Sud) between 1/1/2011 and 12/31/2011 were identified. The hospital database and the file of patients followed in the HIV referral department of each hospital were matched. Detailed clinical and biological data were collected, by returning to the individual medical records, for a random sample (65% of hospitalized patients). RESULTS: A total of 3013 hospitalizations (1489 patients) were recorded in 2011. The estimated rate of hospitalized patients was about 8% among the 10105 PLWH routinely managed in COREVIH Ile-de-France Sud in 2011. The majority (58.5%) of these hospitalizations occurred in a unit other than the HIV referral unit. Non-AIDS-defining infections were the main reason for admission (16.4%), followed by HIV-related diseases (15.6%), hepatic/gastrointestinal diseases (12.0%), and cardiovascular diseases (10.3%). The median length of stay was 5 days overall (IQR: 2-11), it was longer among patients admitted to a referral HIV care unit than to another ward. HIV infection had been diagnosed >10 years previously in 61.4% of these hospitalized patients. They often had associated comorbidities (coinfection HCV/HVB 40.5%, smoking 45.8%; hypertension 33.4%, dyslipidemia 28.8%, diabetes 14.8%). Subjects over 60 years old accounted for 15% of hospitalized patients, most of them were virologically controlled under HIV treatment, and cardiovascular diseases were their leading reason for admission. CONCLUSION: Needs for hospitalization among PLWH remain important, with a wide variety in causes of admission, involving all hospital departments. It is essential to prevent comorbidities to reduce these hospitalizations, and to maintain a link between the management of PLWH, that becomes rightly, increasing ambulatory, and recourse to specialized inpatient services.

Immune response to pertussis vaccine in COPD patients.

Exacerbation triggered by respiratory infection is an important cause of morbidity and mortality in chronic obstructive pulmonary disease (COPD) patients. Strategies aiming to preventing infection may have significant public health impact. Our previous study demonstrated decreased immunological response to seasonal flu vaccination in COPD patients, questioning the efficiency of other vaccines in this group of patients. We performed a prospective, monocenter, longitudinal study that evaluated the humoral and cellular responses upon pertussis vaccination. We included 13 patients with stable COPD and 8 healthy volunteers. No difference in circulating B and T cell subsets at baseline was noted. Both groups presented similar levels of TFH, plasmablasts and pertussis specific antibodies induction after vaccination. Moreover, monitoring T cell immunity after ex-vivo peptide stimulation revealed equivalent induction of functional and specific CD4+ T cells (IFNγ, TNFα and IL-2-expressing T cells) in both groups. Our results highlight the immunological efficiency of pertussis vaccination in this particularly vulnerable population and challenge the concept that COPD patients are less responsive to all immunization strategies. Healthcare providers should stress the necessity of decennial Tdap booster vaccination in COPD patients.

Effects of recombinant human interleukin 7 on T-cell recovery and thymic output in HIV-infected patients receiving antiretroviral therapy: results of a phase I/IIa randomized, placebo-controlled, multicenter study.

BACKGROUND: The immune deficiency of human immunodeficiency virus (HIV) infection is not fully corrected with ARV therapy. Interleukin-7 (IL-7) can boost CD4 T-cell counts, but optimal dosing and mechanisms of cellular increases need to be defined. METHODS: We performed a randomized placebo-controlled dose escalation (10, 20 and 30 µg/kg) trial of 3 weekly doses of recombinant human IL-7 (rhIL-7) in ARV-treated HIV-infected persons with CD4 T-cell counts between 101 and 400 cells/µL and plasma HIV levels <50 copies/mL. Toxicity, activity and the impact of rhIL-7 on immune reconstitution were monitored. RESULTS: Doses of rhIL-7 up to 20 µg/kg were well tolerated. CD4 increases of predominantly naive and central memory T cells were brisk (averaging 323 cells/µL at 12 weeks) and durable (up to 1 year). Increased cell cycling and transient increased bcl-2 expression were noted. Expanded cells did not have the characteristics of regulatory or activated T cells. Transient low-level HIV viremia was seen in 6 of 26 treated patients; modest increases in total levels of intracellular HIV DNA were proportional to CD4 T-cell expansions. IL-7 seemed to increase thymic output and tended to improve the T-cell receptor (TCR) repertoire in persons with low TCR diversity. CONCLUSIONS: Three weekly doses of rhIL-7 at 20 µg/kg are well tolerated and lead to a dose-dependent CD4 T-cell increase and the broadening of TCR diversity in some subjects. These data suggest that this rhIL-7 dose could be advanced in future rhIL-7 clinical studies. CLINICAL TRIALS REGISTRATION: NCT0047732.

What are the prospects for durable immune control?

During the SARS CoV-2 primary infection, the neutralizing antibodies focused against the spike (S) glycoproteins are responsible for blockage of virus-host cell interaction. The cellular response mediated by CD4+ and CD8+ T-cells is responsible for control of viremia. Immune memory against SARS-CoV-2 depends on virus type, replication kinetics and route of penetration. The formation and persistence of germinal centers are critical for the generation of affinity-matured plasma cells and memory B cells capable of mediating durable immunity. They can persist up to 30 weeks after vaccination and several months after infection. Heterogeneity in the longevity of the vaccination-induced GC response is significant.

[Fractures of the lateral process of the talus. Retrospective study of 44 cases]. / Fractures et séquelles de fractures de l'apophyse latérale du talus. Etude rétrospective à propos de 44 cas.

PURPOSE OF THE STUDY: Fractures of the lateral process of the talus are often not diagnosed. The cohorts of the literature are small. The aim of the study was to analyse these fractures with a large group of patients. MATERIAL AND METHOD: Forty-four fractures in 43 patients were reviewed with an average follow-up of 17 months. The diagnosis had been made immediately in 14 cases and secondarily in 30 cases with a delay of 46 months. Patients had been evaluated with Kitaoka's score and radiographies using Hawkins classification. Fractures occurred during sport practise in 19 cases. The most frequent mechanism was association of dorsal flexion and pronation. There were associated lesions in 44% of cases. RESULTS: In the group of delayed diagnosis, we found 14 cases of associated pseudarthrodesis and sub-talar osteoarthritis, two cases of isolated pseudarthrodesis, two cases of isolated sub-talar osteoarthritis. After treatment in this group, the result at the last follow up was very good in 15 cases (50%), good in seven cases (23%), average in seven cases (23%) and bad in one case (4%). In the group of immediate diagnosis five of 14 patients had at least one complication: 29% of pseudarthrodesis and 29% of sub-talar osteoarthritis. After treatment in this group, the result at the last follow-up was very good in eight cases (58%), good in four cases (28%) and average in two cases (14%). Immediate diagnosis was correlated with better results at the last follow-up. In the sub-group of immediate diagnosis, among patients who had an orthopaedic treatment, the rate of secondarily surgery was 42%. CONCLUSION: The fracture of lateral process of the talus is quite frequent and occurs among young people. Spontaneous evolution is severe with two major complications: pseudarthrodesis and sub-talar osteo-arthritis. Treatment is always required in case of displaced fracture.

Prevalence of Plasmodium falciparum cytochrome b gene mutations in isolates imported from Africa, and implications for atovaquone resistance.

The atovaquone resistance of malaria parasites correlates with mutations in the cytochrome b gene. We sequenced the Plasmodium falciparum cytochrome b gene of 135 African isolates. Our data showed a high mutation rate (8.9%); however, the risk of emergence spreading of atovaquone-resistant P. falciparum strains could be limited.

A novel mechanism for HIV1-mediated bystander CD4+ T-cell death: neighboring dying cells drive the capacity of HIV1 to kill noncycling primary CD4+ T cells.

CD4+ T-cell death is a crucial feature of AIDS pathogenesis, but the mechanisms involved remain unclear. Here, we present in vitro findings that identify a novel process of HIV1 mediated killing of bystander CD4+ T cells, which does not require productive infection of these cells but depends on the presence of neighboring dying cells. X4-tropic HIV1 strains, which use CD4 and CXCR4 as receptors for cell entry, caused death of unstimulated noncycling primary CD4+ T cells only if the viruses were produced by dying, productively infected T cells, but not by living, chronically infected T cells or by living HIV1-transfected HeLa cells. Inducing cell death in HIV1-transfected HeLa cells was sufficient to obtain viruses that caused CD4+ T-cell death. The addition of supernatants from dying control cells, including primary T cells, allowed viruses produced by living HIV1-transfected cells to cause CD4+ T-cell death. CD4+ T-cell killing required HIV1 fusion and/or entry into these cells, but neither HIV1 envelope-mediated CD4 or CXCR4 signaling nor the presence of the HIV1 Nef protein in the viral particles. Supernatants from dying control cells contained CD95 ligand (CD95L), and antibody-mediated neutralization of CD95L prevented these supernatants from complementing HIV1 in inducing CD4+ T-cell death. Our in vitro findings suggest that the very extent of cell death induced in vivo during HIV1 infection by either virus cytopathic effects or immune activation may by itself provide an amplification loop in AIDS pathogenesis. More generally, they provide a paradigm for pathogen-mediated killing processes in which the extent of cell death occurring in the microenvironment might drive the capacity of the pathogen to induce further cell death.

Caspase-dependent and -independent T-cell death pathways in pathogenic simian immunodeficiency virus infection: relationship to disease progression.

Studies of human immunodeficiency virus (HIV) and nonhuman primate models of pathogenic and nonpathogenic simian immunodeficiency virus (SIV) infections have suggested that enhanced ex vivo CD4 T-cell death is a feature of pathogenic infection in vivo. However, the relative contributions of the extrinsic and intrinsic pathways to programmed T-cell death in SIV infection have not been studied. We report here that the spontaneous death rate of CD4+ T cells from pathogenic SIVmac251-infected rhesus macaques ex vivo is correlated with CD4 T-cell depletion and plasma viral load in vivo. CD4+ T cells from SIVmac251-infected macaques showed upregulation of the death ligand (CD95L) and of the proapoptotic proteins Bim and Bak, but not of Bax. Both CD4+ and CD8+ T cells from SIVmac251-infected macaques underwent caspase-dependent death following CD95 ligation. The spontaneous death of CD4+ and CD8+ T cells was not prevented by a decoy CD95 receptor or by a broad-spectrum caspase inhibitor (zVAD-fmk), suggesting that this form of cell death is independent of CD95/CD95L interaction and caspase activation. IL-2 and IL-15 prevented the spontaneous death of CD4+ and CD8+ T cells, whereas IL-10 prevented only CD8 T-cell death and IL-7 had no effect on T-cell death. Our results indicate that caspase-dependent and caspase-independent pathways are involved in the death of T cells in pathogenic SIVmac251-infected primates.

[Sequelae of intra-articular calcaneal fractures: patterns and management]. / Chirurgie des séquelles des fractures du calcanéum: à propos de 24 cas.

PURPOSE OF THE STUDY: We reviewed retrospectively 24 feet with sequelae of transtalar process fractures of the calcaneum in order to identify the lesion pattern and determine optimal management options, both for acute and sequelar lesions. MATERIAL AND METHODS: There were fourteen men and nine women, mean age 42 years (19-73). Twenty-three had subtalar osteoarthritis, eight had calcaneocuboid osteoarthritis, and fifteen had lateral submalleolar conflicts. There were twelve fibular tendon dislocations or fissurations, three tarsal tunnel syndromes, and two plantar splinters. Prior to treatment, all patients complained of pain. Preoperatively, walking distance was less than 500 m for thirteen patients, 2000-3000 m for four, and greater than 3000 m for five. Mean subtalar joint motion was 30% (0-100%) compared with the healthy side and mean frontal misalignment of the rear foot was 6 degrees valgus. Physical examination, podoscopy and x-rays were obtained in all patients. The Kitaoka score was noted. RESULT: Mean follow-up was 36 months (24-72). Sequelae were treated with a single procedure or with combinations: subtalar arthrodesis (n = 23) including one in association with calcaneocuboid arthrodesis, tension on fibular tendons (n = 7), neurolysis of the posterior tibial nerve (n = 3), resection of plantar splinters (n = 2), resection of the lateral shell (n = 14), and osteotomy (n = 2) to lower the greater tubercle of the calcaneum because of pain when wearing shoes. The mean Kitaoka function score was 31.7/100 (14-79) preoperatively. After treatment, the mean score was 81.7/100 (31-94), giving a 73.2% gain. The outcome was considered good in sixteen feet, fair in six, and poor in two. Mean walking distance was greater than 3000 m for 18 patients. Mean frontal misalignment of the rear foot under loading was 4.5 degrees valgus and the podoscopy demonstrated flat foot in thirteen patients. Three subtalar arthrodesis required revision for nonhealing. DISCUSSION: Initial treatment of a fracture, particularly an articular fracture, of the calcaneum must avoid disabling postoperative pain and shoe wearing problems. These sequelae basically concern: subtalar and calcaneocuboid arthritis, lateral submalleolar conflict, fibular tendon injury, plantar splinters, tarsal tunnel syndrome, loss of height, and misalignment of the rear foot. At the sequelar stage, the physical examination is primordial to confirm the lesion and search for any complication which could develop later postoperatively when walking distance becomes longer. For nine patients with residual pain, four resulted from lesions which were missed at the preoperative physical examination. Arthrodesis of the subtalar joint should be preferred over realignment of the rear foot and can be associated with the treatment of conflicts. This management scheme allows treating during a single operative time all sequelae, thus limiting recovery time. A scan of the ankle and foot with or without opacification of the fibular tendons is needed to confirm the physical examination which, for us, remains the key to successful surgery.

Effects of two low-osmolar contrast media, ioxaglate and iopamidol, on erythrocyte membrane elasticity.

RATIONALE AND OBJECTIVES: The effect of ioxaglate and iopamidol, two recently developed low-osmolality contrast media, on the shear elasticity of erythrocyte membranes was studied at an iodine concentration of 300 mg/mL and at a 20% volume concentration and compared with that obtained for control solutions matched in osmolality. METHODS: The authors used a micromanipulation technique, which consists of visualizing deformations of individual erythrocytes when gently aspirated into the tip of a glass micropipette by an accurately controlled pressure. An erythrocyte membrane shear elasticity modulus mu was then deduced. An increase in mu corresponded to an increase in erythrocyte membrane rigidity. RESULTS: In all cases, the erythrocytes remained discocytic. The shear elasticity modulus of the erythrocyte membrane is found to be (1) in the presence of ioxaglate (4.3 +/- 0.9 microN/m) lower (P < .001) than in the presence of hyperosmolar saline (6.2 +/- 1.3 microN/m) and lower (P < .02) than in the presence of iso-osmolar control (4.7 +/- 0.7 microN/m); (2) in the presence of iopamidol (5.4 +/- 0.7 microN/m) lower (P < .001) than in the presence of hyperosmolar sucrose (6.4 +/- 1.2 microN/m) and higher (P < .001) than in the presence of iso-osmolar control (4.7 +/- 0.7 microN/m); and (3) lower (P < .001) in the presence of ioxaglate (4.3 +/- 0.9 microN/m) than in the presence of iopamidol (5.4 +/- 0.7 microN/m). CONCLUSIONS: Under the experimental conditions used, both contrast media (ioxaglate and iopamidol) modify the erythrocyte membrane shear elasticity modulus less than do the matched hyperosmolar controls. Moreover, ioxaglate makes the erythrocyte membrane less rigid, and iopamidol makes the erythrocyte membrane more rigid than does the iso-osmolar control.

New pseudo-stationary phases for electrokinetic capillary chromatography. Complexes between bovine serum albumin and sodium dodecyl sulfate.

The complexes formed between a protein (bovine serum albumin, BSA) and a surfactant (sodium dodecyl sulfate, SDS) were studied as separation carriers in electrokinetic chromatography. Selectivities different from those with either SDS or BSA alone in the background electrolyte (BGE) were obtained. Separation performances were demonstrated to be closely related to the type of complex formed, as predicted by the isotherm curve of SDS on BSA. For each composition of background electrolyte, capacity factors and resolutions were calculated. We compared the results with these complexes to electropherograms using BGE containing either BSA or SDS alone. The separation of a mixture of phenols indicate that some compositions of the BSA-SDS complexes are efficient selectors.

Relevance of measuring red blood cell disaggregability in insulin-dependent diabetic patients.

A viscometric study of blood from insulin-treated diabetic patients is carried out. Patients are divided into three major groups--group I: without or with minimal retinopathy and recent diabetes (n = 37), group II: without or with minimal retinopathy and at least 20 years of diabetes duration (n = 35), group III: with severe retinopathy (n = 27). Each group is also subdivided according to the glycosylated hemoglobin (HbA1c) level, used to assess long-term glycemic control. Finally, the rheological parameters of six groups are compared: three of which have a HbA1c level less than 7.5% [I1 (n = 15), II1 (n = 9), III1 (n = 9)] and three others have a HbA1c level more than 7.5% [I2 (n = 22), II2 (n = 26), III2 (n = 18)]. The most important result concerns the thixotropy index xi t, which reflects the dynamic property of red blood cell (RBC) disaggregability under shear. Strong correlations between this parameter and HbA1c level are found for groups I (r = -0.53, p < 0.001) and III (r = -0.68, p < 0.001), providing evidence of a RBC disaggregability disorder for a poor glycemic control of diabetes. In contrast, such a correlation is not pointed out for the group II. As the value for xi t is not statistically different for groups II1 and II2 and is close to the normal value in both groups, the existence of a rheological protection against the retinopathy could be involved.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemorheological improvement after Daflon 500 mg treatment in diabetes.

Rheological disorders, such as blood hyperviscosity, red blood cell (RBC) hyperaggregation or hypodeformability, may be responsible for vascular complications in diabetes. As pointed out by many reports, flavonoids are known to act on RBC rheology in relation with venous thrombosis. These disorders were evaluated by viscometry in order to follow the hemorheological impact of a flavonoid (Daflon 500 mg). Hemorheological effects of Daflon 500 mg, 6 tablets per day for 28 days, were tested in 18 diabetic patients by viscometric measurements carried out on 2 ml blood sample withdrawn on EDTA. Measurements, before and after treatment, were compared with usual statistical tests. The following results were obtained: (1) a decrease of blood viscosity, more pronounced at low shear rate; (2) a better RBC disaggregability process under shear. Therefore, the main conclusion was that the hemorheological improvement, observed after Daflon 500 mg treatment, due to a decrease of RBC aggregation, can induce a decrease of blood flow resistance and a reduction in stasis and resulting ischemia.

Activity of Daflon 500 mg on the hemorheological disorders in diabetes.

A rheological study was performed on blood samples from 10 insulin-treated diabetics with retinopathy. As part of their treatment, they all received 4 tablets of Daflon 500 mg per day for 30 days. Three complementary rheological criteria were used to characterize blood samples: 1) viscometry, using a Couette viscometer, which produces data on viscosity, shear-thinning, viscoelasticity and tixotropy of blood, 2) aggregametry, using an apparatus based on light reflectometry, using a filtrometer based on the deformations red cells undergo as they pass through narrow pores which produces information on red cell deformability. The main results were: a better red blood cell disaggregability, a decrease in red blood cell aggregation and no change in red blood cell deformability.

Size determination of red blood cell aggregates induced by dextran using ultrasound backscattering phenomenon.

Different methods are commonly used to study the red blood cell aggregation phenomenon. The major interest of the ultrasonic method presently discussed is to assess the mean size of red blood cell (RBC) aggregates by measuring ultrasonic intensity backscattered by blood. Applying Rayleigh theory of sound to blood medium, one can show that the scattered ultrasonic intensity is proportional to the 6th power of the size of the RBC aggregates. The ultrasonic method is used to evaluate the mean size of RBC aggregates induced by dextrans. RBCs are suspended at various hematocrits H, in solution of dextrans of different molecular weights M and at different weight concentrations Cw. Results are presented by using the ultrasonic backscattering coefficient chi which is a relevant quantity in a scattering experiment. For suspensions of RBCs aggregated with dextran of molecular weight 70,000 dalton (dextran 70) at concentration Cw = 40 g/l, variations of chi as a function of H are similar to those obtained for normal blood. At a fixed hematocrit, variation of chi versus Cw for dextran 70 exhibits a maximum at 40 g/l. In the case of RBCs suspended at hematocrit 20% and aggregated with dextrans of molecular weight M, 70,000 less than or equal to M less than or equal to 2,000,000, the variations of chi versus molar concentration Cm are similar to those of the microscopic aggregation index defined by Chien (1). Finally, a statistical model of the blood structure previously described (2) is applied to evaluate the mean size of the aggregates. According to this model, the mean size of aggregates is independent of hematocrit for H less than or equal to 40% and independent of the molecular weight of dextran for M greater than or equal to 150,000 dalton.

Theoretical and experimental study of the time dependent flow of red blood cell suspension through narrow pores.

The Hemorheometer has been adapted to allow the recording of the flow rate during the filtration process. For newtonian fluids, the flow rate variation versus time through the pores is well approximated by Poiseuille's law. For dilute red blood cell suspensions, the same analysis can be applied by introducing the concept of "apparent filtration viscosity" which is higher than the usual viscosity measured by Couette viscometry. The apparent filtration viscosity parameter is related to the deformations undergone by red blood cells as they pass through the narrow pores. Apparent filtration viscosity can be used to obtain a precise determination of the erythrocyte deformability. Measurements performed, for a given blood sample, with pores of different diameters (5 microns, 8 microns and 12 microns) show that the error on the value of apparent filtration viscosity is less than 3%. As a result, the sensitivity of the filtration method allows to discriminate among normal blood samples. High concentrations of erythrocytes or leucocytes are found to modify the apparent filtration viscosity. These factors are apparent in the recorded filtration curves. Their effects on filtration measurements can be easily estimated.

Aggregation of red blood cells studied by ultrasound backscattering.

The erythrocyte aggregation phenomenon is an important factor in capillary circulation. This phenomenon can be evaluated by a number of methods (microscopic observations, viscometry, light measurements) which cannot be applied simply to in vivo measurements. In contrast, ultrasound which propagates through soft tissues allows measurement of the mechanical properties of red blood cell (RBC) suspensions which depend on the aggregation phenomenon. We devised an apparatus in order to measure in vitro the ultrasonic backscattering intensity of RBC suspensions. First, with latex particles of different sizes, the ultrasonic backscattering coefficient has been measured in order to evaluate the apparatus response. Then, the ultrasonic backscattering coefficient of different aggregated erythrocyte suspensions has been measured and correlated with the erythrocyte sedimentation rate. Finally, the size of RBC aggregates of different suspensions has been evaluated.