Weak Responders Research Articles

Long-term control of simian immunodeficiency virus (SIV) in cynomolgus macaques not associated with efficient SIV-specific CD8+ T-cell responses.

The spontaneous control of human and simian immunodeficiency viruses (HIV/SIV) is typically associated with specific major histocompatibility complex (MHC) class I alleles and efficient CD8(+) T-cell responses, but many controllers maintain viral control despite a nonprotective MHC background and weak CD8(+) T-cell responses. Therefore, the contribution of this response to maintaining long-term viral control remains unclear. To address this question, we transiently depleted CD8(+) T cells from five SIV-infected cynomolgus macaques with long-term viral control and weak CD8(+) T-cell responses. Among them, only one carried the protective MHC allele H6. After depletion, four of five controllers experienced a transient rebound of viremia. The return to undetectable viremia was accompanied by only modest expansion of SIV-specific CD8(+) T cells that lacked efficient SIV suppression capacity ex vivo. In contrast, the depletion was associated with homeostatic activation/expansion of CD4(+) T cells that correlated with viral rebound. In one macaque, viremia remained undetectable despite efficient CD8(+) cell depletion and inducible SIV replication from its CD4(+) T cells in vitro. Altogether, our results suggest that CD8(+) T cells are not unique contributors to the long-term maintenance of low viremia in this SIV controller model and that other mechanisms, such as weak viral reservoirs or control of activation, may be important players in control. Spontaneous control of HIV-1 to undetectable levels is associated with efficient anti-HIV CD8(+) T-cell responses. However, in some cases, this response fades over time, although viral control is maintained, and many HIV controllers (weak responders) have very low frequencies of HIV-specific CD8(+) T cells. In these cases, the importance of CD8 T cells in the maintenance of HIV-1 control is questionable. We developed a nonhuman primate model of durable SIV control with an immune profile resembling that of weak responders. Transient depletion of CD8(+) cells induced a rise in the viral load. However, viremia was correlated with CD4(+) T-cell activation subsequent to CD8(+) cell depletion. Regain of viral control to predepletion levels was not associated with restoration of the anti-SIV capacities of CD8(+) T cells. Our results suggest that CD8(+) T cells may not be involved in maintenance of viral control in weak responders and highlight the fact that additional mechanisms should not be underestimated.

Abstract 20243: Differential Uptake of Omega-3 Polyunsaturated Fatty Acids in Trial Subjects Could Explain Variability of the Trials’ Outcome

Background: A relationship of regular fish consumption with lowered incidence of cardiovascular disease (CVD) has been appreciated for decades. However, preparations from fish oils, showed mixed results in recent meta-analyses and have raised some doubts on the efficacy of omega-3 polyunsaturated fatty acids (ω-3 PUFA) for management of CVD. Some of these reports suffer from inclusion of studies with ill-defined patient populations, varying PUFA doses, purity, and formulation, while others have patients on drug milieu or have employed placebo that could have undermine the trial outcome. Very few studies have determined ω-3 PUFA levels pre & post treatment. In this report, we are the first to describe heterogeneity of Omega 3 uptake among trial subjects that could have contributed to the inconsistencies of results. Methods: In VASCAZEN-REVEAL trials, 54 subjects with normal to high blood triglycerides levels (TG 90-500mg/dl) and with ω-3 PUFA deficiency (Omega-Score™, OS, blood levels of eicosapentaenoic (EPA)+docosahexaenoic (DHA) +docosapentaenoic acid (DPA) of <6.1% of total blood fatty acids) were provided 4g/day of 6:1 EPA/DHA formulation (>90% purity) for 8 weeks. Changes in the OS levels pre-and post treatment along with individual fatty acids including arachidonic (AA) were determined and desaturation enzymes activities were calculated. Results: Based upon post-treatment increases in the blood levels of OS, weak (WR), intermediate (IR) and strong (SR) responders were identified. Conclusion: This is the first report to show differential effect of Omega-3 on trial subjects and warrants caution in the interpretation of trial data without identifying the responders.

Individual and environmental contributions to treatment outcomes following a neuroplasticity-principled speech treatment (LSVT LOUD) in children with dysarthria secondary to cerebral palsy: A case study review

This study describes the use of a neuroplasticity-principled speech treatment approach (LSVT®LOUD) with children who have dysarthria secondary to cerebral palsy. To date, the authors have treated 25 children with mild-to-severe dysarthria, a continuum of gross and fine motor functions, and variable cognitive abilities. From this data set, two case studies are presented that represent as weak or strong responders to LSVT LOUD. These case studies demonstrate how individual and environmental features may impact immediate and lasting responses to treatment. Principles that drive activity-dependent neuroplasticity are embedded in LSVT LOUD and may contribute to positive therapeutic and acoustic outcomes. However, examination of the response patterns indicated that intensity (within and across treatment sessions) is necessary but not sufficient for change. Weak responders may require a longer treatment phase, better timing (e.g., developmentally, socially), and a more prominent desire to communicate successfully during daily activities. Strong responders appear to benefit from the intensity and saliency of treatment as well as from intrinsic and extrinsic rewards for using the trained skills for everyday communication. Finally, possibilities are presented for technological solutions designed to promote accessibility to the intensive task repetition and maintenance required to drive lasting changes.

Partial dysfunction of Treg activation in sickle cell disease.

Sickle cell disease (SCD) is a chronic inflammatory disease associated with multiple organ damage, chronic anemia, and infections. SCD patients have a high rate of alloimmunization against red blood cells (RBCs) following transfusion and may develop autoimmune diseases. Studies in mouse models have suggested that regulatory T cells (Treg) play a role in alloimmunization against RBC antigens. We characterized the phenotype and function of the Treg cell population in a homogeneous cohort of transfused SCD patients. We found that the distribution of Treg subpopulations differed significantly between SCD patients and healthy blood donors. SCD patients have a particular Treg phenotype, with strong CTLA-4 and CD39 expression and weak HLA-DR and CCR7 expression. Finally, we show that this particular phenotype is related to SCD rather than alloimmunization status. Indeed, we observed no difference in Treg phenotype or function in vitro using autologous feeder cells between strong and weak responders to alloimmunization.

Strong and weak plasma response to dietary carotenoids identified by cluster analysis and linked to beta-carotene 15,15'-monooxygenase 1 single nucleotide polymorphisms

The mechanisms as well the genetics underlying the bioavailability and metabolism of carotenoids in humans remain unclear. To begin to address these questions, we used cluster analysis to examine individual temporal responses of plasma carotenoids from a controlled-diet study of subjects who consumed carotenoid-rich beverages. Treatments, given daily for 3 weeks, were watermelon juice at two levels (20-mg lycopene, 2.5-mg β-carotene, n=23 and 40-mg lycopene, 5-mg β-carotene, n=12) and tomato juice (18-mg lycopene, 0.6-mg β-carotene, n=10). Cluster analysis revealed distinct groups of subjects differing in the temporal response of plasma carotenoids and provided the basis for classifying subjects as strong responders or weak responders for β-carotene, lycopene, phytoene and phytofluene. Individuals who were strong or weak responders for one carotenoid were not necessarily strong or weak responders for another carotenoid. Furthermore, individual responsiveness was associated with genetic variants of the carotenoid metabolizing enzyme β-carotene 15,15'-monooxygenase 1. These results support the concept that individuals absorb or metabolize carotenoids differently across time and suggest that bioavailability of carotenoids may involve specific genetic variants of β-carotene 15,15'-monooxygenase 1.

Immune Response to Hepatitis B Vaccine in Health-Care Workers

Health care workers (HCWs) constitute a high-risk population of HBV infection. There are limited data on the efficacy of vaccination in HCWs in Egypt. The aim of this study was to evaluate the immune response to hepatitis B recombinant vaccine in HCWs in our hospital. Methods: 100 HCWs who completed three doses of intramuscular immunization with recombinant DNA hepatitis B vaccine (Engerix-B) at different time periods during the last 5 years were examined for hepatitis B surface antigen (HBs Ag), anti hepatitis B surface antibodies (anti HBs Abs) and hepatitis B core antibodies (HBc Abs). Results: 96% of HCWs showed seroconversion (anti HBs ≥ 10 IU/L); 92% good responders (anti HBs > 100 IU/L) and 4% weak responders (anti HBs = 10-100 IU/L). The HBsAg and HBc Ab were never detected among the entire responders. Younger age had higher anti HBs titer than older HCWs. The non responders were 4%; two of them had evidence of chronic hepatitis B infection. Conclusion: Vaccination against HBV in HCWs in Egypt is cost effective and achieved good response rate. Screening for Hepatitis B infection before vaccination should be considered to detect those with undiagnosed infection.

Immune Response to Hepatitis B Vaccine in Health-Care Workers

Health care workers (HCWs) constitute a high-risk population of HBV infection. There are limited data on the efficacy of vaccination in HCWs in Egypt. The aim of this study was to evaluate the immune response to hepatitis B recombinant vaccine in HCWs in our hospital. Methods: 100 HCWs who completed three doses of intramuscular immunization with recombinant DNA hepatitis B vaccine (Engerix-B) at different time periods during the last 5 years were examined for hepatitis B surface antigen (HBs Ag), anti hepatitis B surface antibodies (anti HBs Abs) and hepatitis B core antibodies (HBc Abs). Results: 96% of HCWs showed seroconversion (anti HBs ≥ 10 IU/L); 92% good responders (anti HBs > 100 IU/L) and 4% weak responders (anti HBs = 10-100 IU/L). The HBsAg and HBc Ab were never detected among the entire responders. Younger age had higher anti HBs titer than older HCWs. The non responders were 4%; two of them had evidence of chronic hepatitis B infection. Conclusion: Vaccination against HBV in HCWs in Egypt is cost effective and achieved good response rate. Screening for Hepatitis B infection before vaccination should be considered to detect those with undiagnosed infection.

Sequential ADP-stimulated light transmission and multiple electrode aggregometry in patients taking aspirin and clopidogrel after non ST-elevation myocardial infarction

Background. Fast platelet function tests can identify weak clopidogrel responders, but data on variability over time in clopidogrel responsiveness in several clinical settings are lacking. We wanted to explore long-term variability of multiple electrode aggregometry (MEA) measurements and the agreement between MEA and light transmission aggregometry (LTA) in patients with non-ST elevation myocardial infarction (NSTEMI) treated with aspirin and clopidogrel. Methods. Parallel MEA and LTA were performed at baseline and after 6 and 12 weeks in 31 patients treated with percutaneous coronary intervention after NSTEMI. Adenosine diphosphate (ADP) concentrations 2 μM, 6.5 μM and 10 μM were used. Parallel testings in both arterial and venous blood were performed at baseline. MEA and LTA cut-off levels were applied to discriminate aggregation values suggesting presence or absence of high platelet reactivity (HPR). Results. Arterial and venous MEA and LTA aggregation were similar. Within-subject variability in both MEA and LTA aggregation throughout the study was moderate. According to MEA, eight patients had HPR at baseline (MEA aggregation > 47 U). Defining > 47% as the LTA aggregation HPR cut-off level, the same number of patients (eight) had HPR according to LTA. Of the 93 MEA/LTA observations 81 (87.1%) gave the same HPR classification. MEA vs. LTA agreement at baseline was slightly inferior to that obtained after 12 weeks. Conclusions. MEA and LTA aggregation in arterial and venous blood seem similar. Within-subject variability over time was moderate, and the agreement between LTA and MEA was good, and stable in most patients.

SU-E-J-186: CT Textures Can be Predictive for Tumor Shrinkage.

To determine if NSCLC GTV CT textures can be predictive for tumor shrinkage after proton therapy with concurrent chemotherapy. Simulation and weekly 4DCTs were obtained from 25 patients with locally advanced NSCLC treated by proton therapy at a 74 Gy dose level with concurrent chemotherapy. In-house deformable image registration software based on the demons algorithm propagated the physician-generated planning GTV onto each weekly image set. GTV soft tissue volumes were then extracted from CT images by in-house software which pruned out voxels below a cutoff HU threshold. Patients whose normalized end-treatment pruned GTV was less than the group median were classified as 'strong responders.'The remaining patients were classified as 'weak responders.' For each pruned GTV, the MaZda texture analysis software generated quantitative 3D texture features based on the image histogram, absolute gradient, co-occurrence matrix, and run-length matrix. Using the Fisher coefficient, a subset of these texture features that were relevant to distinguishing the two response groups was obtained. In-house software and MaZda were then used to perform neural network data classification with leave-one-out cross-validation based on this texture feature subset. The true positive rate (TPR), false positive rate (FPR), classification accuracy, and one-sided p-values were recorded. Six classification models were tested. Each model had a unique combination of feature extraction and analysis parameters. Taking 'strong responders' to be the 'positive' class, the average TPR was 0.66 (0.60 - 0.75), the average FPR was 0.36 (0.31 - 0.40), the average classification accuracy was 64.8% (60.0% - 68.0%), and the average one-sided p-value was 0.118 (0.055 - 0.215). There is some evidence showing that NSCLC GTV CT textures can be predictive for tumor shrinkage after proton therapy. Further work should be done to include more patients, texture metrics, and data analysis techniques. The presenting author receives funding support from a Hertz Foundation Applied Science Fellowship.

Changes in the body condition scores of Nigerian West African Dwarf sheep experimentally infected with mixed infections of Haemonchus contortus and Trichostrongylus colubriformis

Weekly changes in body condition scores and body weights were determined in West African Dwarf sheep following trickle exposure to weekly escalating mixed infections with Haemonchus contortus and Trichostrongylus colubriformis starting with single doses of 500 infective larvae (L3) at wk1, 1000 L3 at wk2, 2000 L3 at wk3 and 4000 L3 at wk4. Thirty-three animals were randomly assigned to two groups namely, Group 1 (n=27) and Group 2 (n=6). Group 1 animals were used for experimental infections and Group 2 animals served as uninfected controls. Body condition scores (BCS), body weights (BW), faecal egg counts (FEC) per gram of faeces and worm burden (Wb) were determined using standard procedures. Lambs in group 1 with epg≤1000 were classified as strong responders (n=16), those with epg between 1000 and 10,000 as intermediate (n=5) and lambs with epg>10,000 on any sampling day were classified as weak responders (n=6). Based on this classification, the mean epg of lambs classified as strong responders was significantly lower (P<0.001) than the epg of lambs classified as weak responders. The body condition scores and body weights of the strong responder lambs were comparable with those of the uninfected control and they were significantly higher than those of the weak and intermediate responders from wk5 till the end of the experiment. There was an inverse and significant relationship between the average BCS of days 56 and 59 and the average FEC of days 56 and 59 (rs=−572; P=0.017; n=27) as well as with Wb (rs=−531; P=0.028; n=27). We concluded that changes in the body scores are good indicators of the intensity of gastrointestinal nematode infection in the Nigerian WAD sheep.

Abstract P266: Molecular Markers of Endothelial Sensitivity to TNFα

TNF alpha mediated inflammation has been correlated with cardiovascular diseases. Significant interindividual variability to anti-TNF biologicals has been demonstrated in clinical trials. The objective of this study is to unravel the molecular markers of sensitivity to TNF which could be used as predictors of therapeutic efficacy or disease progression. We have isolated and tested a set of 20 HUVECs for their sensitivity to TNF as determined by up-regulation of pro-inflammatory genes such as the Intracellular Adhesion Molecule 1 (ICAM1) and the NADPH oxidase subunit 4 (NOX4). We found that 75% of HUVECs (15/20) responded strongly to TNF compared to the remaining 25% (5/20, p&lt;0.01). Further studies on the TNF signaling pathway indicated that there was a positive correlation between strong response to TNF and higher basal mRNA and protein levels of the mitogen activated protein 3 kinase 1 (MAP3K1 or MEKK1). No further correlations where observed with other signaling components (i.e., TNF receptors, TRAFs, and other MAP3Ks, MAP2Ks or MAPKs). Strong responders also showed 1) increased upregulation of TNFR1 and TRAF5 protein and mRNA levels, 2) higher phosphorylation of JNK and p38 MAPKs and 3) stronger AP1-driven transcription as shown by luciferase assays. Weak responders showed increased TNF-dependent down-regulation of the TNF receptor 1 and of the MAP3K5 (aka Apoptosis-Signaling Kinase 1, ASK1) and TNF-mediated upregulation of the TNF receptor 2 compared to strong responders. Promoter and mRNA stability studies revealed that differences between strong and weak responders in MAP3K1 and MAP3K5 regulation occurs at the transcriptional level. Studies of promoter polymorphisms are undergoing. We conclude that MAP3K1 and MAP3K5 are novel molecular markers of endothelial sensitivity to TNF and future studies on these genes could reveal novel genetic markers for translational research.

Immunogenicity of hepatitis B vaccine among hemodialysis patients: Effect of revaccination of non-responders and duration of protection

Hepatitis B vaccination is recommended for patients on hemodialysis, however, seroprotection after a primary vaccine series is suboptimum. Limited data are available on the effect of revaccination of non-responders and on persistence of immunity in this population. Hepatitis B vaccine (40 μg/dose) was given to 77 susceptible patients on hemodialysis (0, 1, and 6 month schedule). Levels of hepatitis B surface antibody (anti-HBs) were tested ≥ 28 days after the third dose was administered, and non-responders revaccinated with an additional 3-dose series. Vaccine responders (anti-HBs ≥10 mIU/mL) were re-tested every 6 months and booster doses given as needed. Kaplan-Meier survival curve was used to estimate the probability of maintaining protective antibody level. Cox-proportional hazards models were used to assess the association between time to loss of protective antibody levels and certain explanatory variables. Overall primary vaccine-induced response was 79.2% (95% CI 68.2%, 87.3%), including 49/77 (63.6%; 95% CI 51.8%, 74.7%) patients who received the initial primary hepatitis B vaccine series and 12/21 (57.1%; 95% CI 34.4%, 77.4%) non-responders who were revaccinated with an additional series. Among weak responders (anti-HBs level 10.0-99.9 mIU/mL), protective antibody levels persisted in 44% for 12 months post-vaccination; whereas among strong responders (anti-HBs level ≥100 mIU/mL), protective antibody levels persisted in 92% for 12 months, and 68% for 24 months post-vaccination. A weak post-vaccination response increased the risk of losing protective antibody levels (adjusted hazard ratio, 9.7; 95% confidence interval, 3.5-28.5; p<0.0001). Revaccinating patients undergoing hemodialysis who do not respond to a primary vaccine series substantially increases the pool of protected patients. The threshold for defining hepatitis B vaccine-induced immunity should be revisited in this patient population to maximize the duration of protection.

Antibody response following Hepatitis B vaccination in peritoneal dialysis patients: does normalized urea clearance matter?

OBJECTIVES:Data on the factors that contribute to the antibody response to hepatitis B virus vaccination in peritoneal dialysis patients are scarce. The current study was conducted on a group of peritoneal dialysis patients to learn how the response to hepatitis B virus vaccination varies according to the patient's clearance of urea normalized to total body water (Kt/V).METHODS:A convenience sample of 33 peritoneal dialysis patients (13 women and 20 men, with a mean age of 49±12 years) was administered double doses (20 µg IM in each deltoid muscle) of recombinant hepatitis B vaccine at 0, 1, 2, and 6 months. Response to immunization was measured at one to three months after the final dose of vaccine. The subjects were divided into groups according to the level of antibodies to hepatitis B surface antigen (anti-HBs), including non-responders (<10 IU/L), weak responders (10-100 IU/L), and good responders (>100 IU/L).RESULTS:Among non-responders, weak responders, and good responders, significant differences were found in age (54±12 vs. 56±9 vs. 45±12 years, respectively; p = 0.049) and recombinant human erythropoietin use (20 vs. 29 vs. 76%, respectively; p = 0.016). No significant differences in weekly total Kt/V (p = 0.704), weekly peritoneal Kt/V (p = 0.064) and residual glomerular filtration rate (p = 0.355) were found across the three groups.CONCLUSIONS:Delivered clearance measured by weekly peritoneal Kt/V and total clearance measured by weekly total Kt/V did not predict the response to hepatitis B virus vaccination in patients on peritoneal dialysis.

Good response to HBsAg vaccine in dialysis patients is associated with high CD4+/CD8+ ratio

Chronic renal failure is accompanied by various abnormalities of innate and acquired, cellular and humoral immunity. We aimed to investigate whether positive Candida skin test results, CD4+ and CD8+, before the first dose of vaccination could be a predictor for antibody response to hepatitis B vaccination and the relation of these parameters with hepatitis B antibody levels 1 month after the last dose of vaccination. The present study was carried out in 57 dialysis patients. All patients received recombinant hepatitis B vaccine (40 μg) given intramuscularly in the deltoid muscle in a four-dose schedule at 0, 1, 2, and 6 months. Candida skin test and lymphocyte subsets (CD4+ and CD8+) were determined before the first dose of vaccination and 1 month after the fourth inoculation of hepatitis B vaccine. Ten patients (17.5%) were non-responders (HBsAb < 10 IU/L), while 47 patients (82.5%) were responders (HBsAb ≥ 10 IU/L). However, 29 patients (50.9%) were weak responders (HBsAb:10-100 IU/L), 18 patients (31.6%) good responders (HBsAb > 100 IU/L), which was determined 1 month after the fourth dose of vaccination. Thirty-nine patients (68.4%) and 44 patients (77.2%) were anergic to Candida skin test before the first dose and 1 month after fourth inoculation of hepatitis B vaccine, respectively. There was no relationship between Candida skin test and response to hepatitis B vaccination. Mean age was lower, and CD4+/CD8+ ratio measured both before and after vaccination was higher in good responders compared with that of weak responders and that of non-responders. Females were better responders than males. High skin test anergy rate and low seroconversion rate after hepatitis B vaccination are important problems in patients on dialysis. Females, younger patients, and patients with higher CD4+/CD8+ ratio have better HBsAb antibody response to hepatitis B vaccination.

179. PURIFICATION AND CHARACTERISATION OF MOUSE TESTICULAR MACROPHAGES: GENE EXPRESSION RESPONSE TO LIPOPOLYSACCHARIDE ACTIVATION INDICATES AN IMMUNOSUPPRESSIVE PHENOTYPE

Studies on rat testicular macrophages (TMs) have indicated that these cells play an important role in testis function by supporting the immunosuppressive environment that protects developing germ cells and by responding to pathogens. By comparison, mouse TMs are essentially uncharacterised due to difficulties in isolating sufficient cells for study. We have established a technique for isolating 95% pure TMs from adult mice by differential adherence. Mouse TMs were cultured for 3h with saline, 10 or 100 ng/mL lipopolysaccharide (LPS) and compared with resident peritoneal macrophages (PMs) and bone marrow-derived macrophages (BMMs). Expression of inflammatory regulators was determined using real-time Q-PCR and AgilentTM microarray analysis. Microarray analysis indicated that each macrophage type displayed very distinct gene expression profiles. There were 526 genes uniquely expressed in TMs at basal levels compared with the other macrophages and 268 genes uniquely expressed by TMs after LPS treatment. Q-PCR determined that LPS induced expression of the anti-inflammatory cytokine interleukin (IL)-10 in each of the macrophage types, with BMMs the strongest responders. LPS stimulated IL-10 mRNA approximately 100-fold in TMs, but only 20-fold in PMs. The anti-inflammatory transforming growth factor-β1 was not significantly induced at this time-point in any macrophage type. In terms of pro-inflammatory mediators, the TM response to LPS was always lower compared to the BMMs. Compared to PMs, the responses of TMs were similar for the hallmark pro-inflammatory cytokine tumour necrosis factor- a, but 40% less for IL-1β. TMs were also deficient in production of IL-6 and cyclooxygenase-2 and IL-12. TMs were therefore relatively strong responders to LPS in terms of IL-10, but weak responders in terms of pro-inflammatory mediators, indicating an immunosuppressive phenotype. The isolation and gene measurement methods established in this study will allow us to use knockout and transgenic mouse models to determine the role for TMs in testicular inflammation/fibrosis models.

Assessment of the anti-Naja haje antibodies elicited in a low dose multi-site immunization protocol

The horse antibodies to Naja haje (Nh) elicited in a low dose multi-site immunization protocol were investigated from binding perspective in the context of antivenom maturation. We found that, this protocol evoked the production of lethality neutralizing avid antibodies in the first round of immunization which increases over the successive immunization rounds. The changes and the relative changes in the antibody parameters of each horse were taken as a measure for the efficacy of its immune system to respond by gaining and magnifying the antivenom parameters. While the avidity increases over the successive immunization rounds towards a maturation ceiling, the avidity gain and relative gain decreases. While the ED 50 gain increases over the immunization rounds, the relative ED 50 gain of the strong responder horse-1 is steadier than for the weak responders horse-2 and horse-3. The profiles for the gain and the relative gain of ELISA titers by three horses are pronouncedly different, reflecting great variations in the immune response by the individual animals. A late antigen dependent avidity pulse was detected after the last dose of the second immunization period, demonstrating that antibody maturation continues during the rest periods. The avidity pulse appears as an increase in avidity which returns to a base level within four weeks. These results indicted that maturation of antibodies to lethality neutralization relevant venom epitopes rather than maturation of antivenoms is the most important potency determining factor. Eventually, a main advantage of the low dose multi-site immunization protocol is the production of highly avid antibodies at the primary immunizations which is mostly crucial for the production of highly potent antivenoms.

Persistence of Hepatitis B Vaccine Immunity in Hemodialysis Patients

Although the efficacy of hepatitis B vaccines in patients undergoing chronic hemodialysis (HD) treatment has been documented, the persistence of immunity in this population remains largely unknown. In this study we evaluated the persistence of hepatitis B vaccine immunity in HD patients. We followed 37 hepatitis B vaccinated HD patients (following a four-dose vaccination schedule of 40 mug injections intramuscularly in the deltoid muscle at 0, 1, 2, and 6 months) for up to one year to evaluate the persistence of immunity (as indicated by serum levels of hepatitis B surface antibody (anti-HBs) equal to or higher than 10 IU/L). One year after vaccination, 18.9% of patients had lost their anti-HBs (transient responders), while 81.1% still had detectable antibodies in the serum (persistent responders). From 81.1% of persistent responders 11.5% and 88.5% were weak and high responders, respectively. There was no significant difference between persistent and transient responders regarding age, sex, or nutritional factors. We did not find any factors that related to maintaining protective levels of anti-HBs in HD patients. It seems that an antibody titer above 100 IU/L following vaccination is necessary in order to maintain that level of antibody one year later.

Efficacy and long-term immunogenicity of hepatitis B vaccine in haemodialysis patients

Hepatitis B vaccine is effective in protection against hepatitis B virus (HBV) infection in haemodialysis (HD) patients, but the antibody response is variable in this population and the persistence of immunity in them remains largely unknown. In this study we aimed to evaluate the efficacy and long-term immunogenicity of hepatitis B vaccine in HD patients. In this study, we initially offered HBV vaccination as double dose, four vaccine series schedule (40 microg injections intramuscularly in the deltoid muscle at 0, 1, 2 and 6 months) to 54 HD patients who were negative for hepatitis B core antibody and did not receive any dose of HBV vaccine previously. Serum levels of hepatitis B surface antibody (anti-HBs) tested 1-2 months after completion of vaccination. Then we follow the patients up to 1 year after primary vaccination to evaluate the persistence of immunity (as indicated by serum levels of anti-HBs higher than or equal to 10 IU/l). After primary vaccination, 87% of patients developed anti-HBs levels above 10 IU/l. 27.8% and 59.2% of them were weak responders and high responders respectively. 13% of patients were non-responders. After 1-year follow-up, 18.18% of responders had lost their anti-HBs (transient responders). All of them were initially in weak responders group and had lower anti-HBs levels. We found an average percentage of seroconversion after primary HBV vaccination in HD patients. Our study also supported this fact that an antibody titre above 100 IU/l following primary vaccination is necessary to maintain that level of antibody 1 year later.

Inbred or outbred? An evaluation of the functional allogenicity of farm sheep used in cardiac valve studies

Cryopreserved allograft cardiovascular tissue elicits a strong cellular and humoral response in recipients; this may accelerate the deterioration of the allograft and complicate future heart transplantation. Juvenile sheep are the standard model for in vivo valve research and have been used to investigate the allogeneic immune response to cardiac valve and vascular tissue transplantation. Studies to date have not considered the extent of allogenicity of sheep used in transplantation studies. Functional allogenicity was assessed by standard one-way mixed lymphocyte reaction assay using peripheral blood mononuclear cells. Responder cells were stimulated with irradiated stimulator cells and cultured at 37 degrees C in 95% air and 5% carbon dioxide for 3, 4, 5, and 6 days. Cultures were pulsed with tritiated thymidine for 24 hours and harvested onto filtermats. The allogeneic response, measured as counts per minute, demonstrated a bimodal distribution. Fifty-nine (36.9%) of 160 pairs fell within the first peak (counts per minute < 10,000) and were defined as weak responders. The remaining 101 (63.1%) of 160 pairs of animals demonstrated a strong allogeneic response (counts per minute > or = 10,000) that followed a normal distribution. More than 1 in 3 pairs of sheep is too closely related to elicit an immune response when cross-reacted. This finding may alter the interpretation of studies that base their findings on allogeneic transplantations in sheep without ascertaining the genetic similarities of the animals. Valve transplantation studies in a sheep model should assess the extent of allogenicity of donor and recipient sheep.

Nonresponse to adefovir: Host or virus dependent?

1 d The introduction of adefovir as a drug against lamivuine resistant hepatitis B virus initially raised considerable ope, but reports of subsequent studies have presented conicting results. While recent publications (Zeng et al., 2006; ampertico et al., 2005; Hadziyannis and Papatheodoridis, 006) still confirm a high response rate and no or very litle resistance others report treatment failures in up to 50% as ummarized by Wong and Lok most recently (Wong and Lok, 006). The reasons for these failures appear diverse. Selecion of resistant virus variants with mutations rtA181V/T or tN236T occurs in up to 29% after 5 years (Wong and Lok, 006) or in 31.5% in even shorter periods (Osiowy et al., 006). Probably as important as acquired resistance is priary nonresponse to adefovir. We have recently described n HBV variant, which existed in three nonresponders even efore adefovir treatment. The associated mutation rtI233V equired a 6–10 times higher adefovir concentration for 50% nhibition of replication in vitro than the wild type (Schildgen t al., 2006). This variant occurs in ca. 2% of the patients orldwide (Schildgen et al., 2006; Chang and Lai, 2006). owever, van Bommel et al. reported in the August issue of EPATOLOGY that nonor weak responders to adefovir are uch more frequent (20/127) and they all carried either wild ype virus or lamivudine resistant variants without adefovir esistance markers (van Bommel et al., 2006). In our small ollection of five adefovir treatment failures in HIV negative atients, we observed only one case of infection without the nown adefovir resistance-inducing mutations. A 22-yearld female patient with a HBeAg positive chronic hepatitis B