Prevention of the anti-factor VIII memory B-cell response by inhibition of Bruton tyrosine kinase in experimental hemophilia A

Hemophilia A is a rare hemorrhagic disorder caused by the lack of functional pro-coagulant factor VIII. Factor VIII replacement therapy in patients with severe hemophilia A results in the development of inhibitory anti-factor VIII IgG in up to 30% of cases. To date, immune tolerance induction, with daily injection of large amounts of factor VIII, is the only strategy to eradicate factor VIII inhibitors. This strategy is, however, efficient in only 60-80% of patients. We investigated whether blocking B-cell receptor signaling upon inhibition of Bruton tyrosine kinase prevents anti-factor VIII immune responses in a mouse model of severe hemophilia A. Factor VIII-naïve and factor VIII-sensitized factor VIII-deficient mice were fed with the selective inhibitor of Bruton tyrosine kinase, (R)-5-amino-1-(1-cyanopiperidin-3-yl)-3-(4-[2,4-difluorophenoxyl] phenyl)-1H pyrazole-4-carboxamide (PF-06250112), to inhibit B-cell receptor signaling prior to challenge with exogenous factor VIII. The consequences on the anti-factor VIII immune response were studied. Inhibition of Bruton tyrosine kinase during the primary anti-factor VIII immune response in factor VIII-naïve mice did not prevent the development of inhibitory anti-factor VIII IgG. In contrast, the anti-factor VIII memory B-cell response was consistently reduced upon treatment of factor VIII-sensitized mice with the Bruton tyrosine kinase inhibitor. The Bruton tyrosine kinase inhibitor reduced the differentiation of memory B cells ex vivo and in vivo following adoptive transfer to factor VIII-naïve animals. Taken together, our data identify inhibition of Bruton tyrosine kinase using PF-06250112 as a strategy to limit the reactivation of factor VIII-specific memory B cells upon re-challenge with therapeutic factor VIII.

Complement C3 is a novel modulator of the anti-factor VIII immune response

Development of neutralizing antibodies against therapeutic Factor VIII (FVIII) is the most serious complication of the treatment of hemophilia A. There is growing evidence to show the multifactorial origin of the anti-FVIII immune response, combining both genetic and environmental factors. While a role for the complement system on innate as well as adaptive immunity has been documented, the implication of complement activation on the onset of the anti-FVIII immune response is unknown. Here, using in vitro assays for FVIII endocytosis by human monocyte-derived dendritic cells and presentation to T cells, as well as in vivo complement depletion in FVIII-deficient mice, we show a novel role for complement C3 in enhancing the immune response against therapeutic FVIII. In vitro, complement C3 and its cleavage product C3b enhanced FVIII endocytosis by dendritic cells and presentation to a FVIII-specific CD4⁺ T-cell hybridoma. The C1 domain of FVIII had previously been shown to play an important role in FVIII endocytosis, and alanine substitutions of the K2092, F2093 and R2090 C1 residues drastically reduce FVIII uptake in vitro. Interestingly, complement activation rescued the endocytosis of the FVIII C1 domain triple mutant. In a mouse model of severe hemophilia A, transient complement C3 depletion by humanized cobra venom factor, which does not generate anaphylatoxin C5a, significantly reduced the primary anti-FVIII immune response, but did not affect anti-FVIII recall immune responses. Taken together, our results suggest an important adjuvant role for the complement cascade in the initiation of the immune response to therapeutic FVIII.

The ADAMTS131239-1253 peptide is a dominant HLA-DR1-restricted CD4+ T-cell epitope

Acquired thrombotic thrombocytopenic purpura is a rare and severe disease characterized by auto-antibodies directed against “A Disintegrin And Metalloproteinase with Thrombospondin type 1 repeats, 13^th member" (ADAMTS13), a plasma protein involved in hemostasis. Involvement of CD4⁺ T cells in the pathogenesis of the disease is suggested by the IgG isotype of the antibodies. However, the nature of the CD4⁺ T-cell epitopes remains poorly characterized. Here, we determined the HLA-DR-restricted CD4⁺ T-cell epitopes of ADAMTS13. Candidate T-cell epitopes were predicted in silico and binding affinities were confirmed in competitive enzyme-linked immunosorbent assays. ADAMTS13-reactive CD4⁺ T-cell hybridomas were generated following immunization of HLA-DR1 transgenic mice (Sure-L1 strain) and used to screen the candidate epitopes. We identified the ADAMTS13^1239–1253 peptide as the single immunodominant HLA-DR1-restricted CD4⁺ T-cell epitope. This peptide is located in the CUB2 domain of ADAMTS13. It was processed by dendritic cells, stimulated CD4⁺ T cells from Sure-L1 mice and was recognized by CD4⁺ T cells from an HLA-DR1-positive patient with acute thrombotic thrombocytopenic purpura. Interestingly, the ADAMTS13^1239–1253 peptide demonstrated promiscuity towards HLA-DR11 and HLA-DR15. Our work paves the way towards the characterization of the ADAMTS13-specific CD4⁺ T-cell response in patients with thrombotic thrombocytopenic purpura using ADAMTS13^1239–1253-loaded HLA-DR tetramers.

The C1 and C2 domains of blood coagulation factor VIII mediate its endocytosis by dendritic cells

The development of inhibitory antibodies to therapeutic factor VIII is the major complication of replacement therapy in patients with hemophilia A. The first step in the initiation of the anti-factor VIII immune response is factor VIII interaction with receptor(s) on antigen-presenting cells, followed by endocytosis and presentation to naïve CD4⁺ T cells. Recent studies indicate a role for the C1 domain in factor VIII uptake. We investigated whether charged residues in the C2 domain participate in immunogenic factor VIII uptake. Co-incubation of factor VIII with BO2C11, a monoclonal C2-specific immunoglobulin G, reduced factor VIII endocytosis by dendritic cells and presentation to CD4⁺ T cells, and diminished factor VIII immunogenicity in factor VIII-deficient mice. The mutation of basic residues within the BO2C11 epitope of C2 replicated reduced in vitro immunogenic uptake, but failed to prevent factor VIII immunogenicity in mice. BO2C11 prevents factor VIII binding to von Willebrand factor, thus potentially biasing factor VIII immunogenicity by perturbing its half-life. Interestingly, a factor VIII^Y1680C mutant, that does not bind von Willebrand factor, demonstrated unaltered endocytosis by dendritic cells as well as immunogenicity in factor VIII-deficient mice. Co-incubation of factor VIII^Y1680C with BO2C11, however, resulted in decreased factor VIII immunogenicity in vivo In addition, a previously described triple C1 mutant showed decreased uptake in vitro, and reduced immunogenicity in vivo, but only in the absence of endogenous von Willebrand factor. Taken together, the results indicate that residues in the C1 and/or C2 domains of factor VIII are implicated in immunogenic factor VIII uptake, at least in vitro Conversely, in vivo, the binding to endogenous von Willebrand factor masks the reducing effect of mutations in the C domains on factor VIII immunogenicity.

[Results of measuring neutron dose inside the Russian segment of the International Space Station using bubble detectors in experiment Matreshka-R]

Distribution of neutron equivalent dose both inside and outside the spherical phantom (experiment Matryeshka-R) was determined with the help of dedicated research equipment "Bubble-dosimeter". Equipment is built up from an automatic bubbles counter and 8 bubble detectors of neutrons with energy ranging from approximately 200 keV to 15 MeV. Measurements inside the ISS were made in several 7-day sessions in the period from April 2006 till October 2007 (ISS increments 13-15). According to the bubble detectors on the outside of the phantom, ambient neutron dose H*(10) was equal to 0.1 mSv/d or approximately 20% of the dose from charged particles inside the ISS. In the tissue-equivalent phantom, neutron dose was 1.2 +/- 0.2 times less as compared with the phantom surface which characterized the degree of dose attenuation in cosmonaut's body.

Surfing-related ocular injuries

PURPOSE

This report evaluates the clinical characteristics of surfing-related ocular trauma to learn the nature of such injuries and propose possible preventive measures.

METHODS

The authors reviewed 11 cases of surfing-related eye injuries caused by direct trauma from the surfboard, studying their mechanism of injury, the associated ocular complications, and the anatomic and visual outcomes of surgical repair.

RESULTS

Surfing-related ocular injuries occurred exclusively in young males (mean age, 24.8 years; range, 14-37 years). The mechanism of injury most frequently responsible was impact with the sharp nose of the surfboard following a fall. Serious posterior segment complications were observed in all 11 patients, with nine patients suffering ruptured globes. Despite immediate medical attention, five patients did not recover ambulatory levels of visual acuity (>5/200).

CONCLUSIONS

Surfing-related ocular trauma presenting to the retinal specialist typically leaves the patient with a permanent visual disability. Important factors contributing to these high-velocity injuries include the sharply pointed nose of the surfboard and the leash keeping the surfer in close proximity to the board following a fall. A simple modification in surfboard design such as blunting the sharp nose of the surfboard, or appropriate protective guards fitted over the surfboard nose, should lessen the severity of such injuries.

Efficacy of trovafloxacin, a new quinolone antibiotic, in experimental staphylococcal endocarditis due to oxacillin-resistant strains

Therapeutic options for severe infections caused by strains of oxacillin-resistant Staphylococcus aureus (ORSA) and coagulase-negative staphylococci (ORSE) are very limited. With the increasing resistance of such strains to aminoglycosides, rifampin, and currently available quinolone agents, as well as the recent documentation of increasing resistance of ORSA to vancomycin (VANCO), new treatment alternatives are imperative. The in vivo efficacy of trovafloxacin (TROVA), a new quinolone agent with excellent antistaphylococcal activity in vitro, against experimental endocarditis (IE) due to beta-lactamase-producing ORSA and ORSE strains (ORSA and ORSE IE) was evaluated. TROVA (25 mg/kg of body weight intravenously [i.v.] twice daily [b.i.d]) was compared to VANCO (20 mg/kg i.v. b.i.d.) and two regimens of ampicillin-sulbactam (AMP-SUL; 200 mg/kg intramuscularly [i.m.] three times a day [t.i.d.] and 20 mg/kg i.m. b.i.d.), with all agents given for 3 or 6 days. AMP-SUL was included as a comparative treatment regimen because of its proven efficacy against experimental ORSA and ORSE IE. For both ORSA and ORSE IE, TROVA, AMP-SUL, and VANCO each reduced staphylococcal densities in vegetations compared to untreated controls (P < 0.01). For ORSA IE, TROVA was the most rapidly bactericidal agent--although not to a statistically significant degree--correlating with its superior bactericidal effect in vitro compared to those of VANCO and AMP-SUL.

Ampicillin-sulbactam is effective in prevention and therapy of experimental endocarditis caused by beta-lactamase-producing coagulase-negative staphylococci

Optimal strategies for the prophylaxis and therapy of endocarditis caused by oxacillin-resistant, coagulase-negative staphylococci in patients with native or prosthetic valvular heart disease are not well defined. We compared the in vivo efficacies of ampicillin-sulbactam-based regimens with those of vancomycin-based oxacillin-resistant, beta-lactamase-producing coagulase-negative staphylococcal isolate (Staphylococcus haemolyticus SE220). Ampicillin-sulbactam (100 and 20 mg/kg of body weight, respectively, given intramuscularly in a two-dose regimen) was equivalent to vancomycin (30 mg/kg given intravenously in a two-dose regimen) in its prophylactic efficacy against the coagulase-negative staphylococcal strain (93 and 80%, respectively). The combination of ampicillin-sulbactam plus either rifampin or vancomycin did not enhance the prophylactic efficacy compared with that of ampicillin-sulbactam or vancomycin alone. In the therapy of established aortic valve endocarditis in rabbits caused by this same coagulase-negative staphylococcal strain, animals received 7-day ampicillin-sulbactam-based or vancomycin-based regimens with or without rifampin. All treatment regimens were effective at lowering intravegetation coagulase-negative staphylococcal densities and rendering vegetations culture negative compared with the coagulase-negative staphylococcal densities and vegetations of untreated controls, with ampicillin-sulbactam in combination with rifampin or vancomycin being the most active regimen. However, only the regimen of ampicillin-sulbactam in combination with vancomycin effectively prevented relapse of endocarditis posttherapy after a 5-day antibiotic-free period. For animals receiving rifampin-containing regimens, relapses of endocarditis were associated with the in vivo development of rifampin resistance among coagulase-negative staphylococcal isolates in the vegetation. Ampicillin-sulbactam was highly effective in the prevention of experimental endocarditis caused by a beta-lactamase-producing, oxacillin-resistant coagulase-negative staphylococcal strain. Ampicillin-sulbactam was also efficacious for the therapy of coagulase-negative staphylococcal endocarditis, especially when it was combined with vancomycin to prevent posttherapeutic relapses.

Diagnosing oral diseases that affect the eyes

Dentists can often help diagnose diseases that affect the eyes. This article discusses the diseases and iatrogenic dental conditions where ophthalmic and oral findings play a key role in diagnosis and treatment.

Retinopathy of prematurity: incidence and severity in Hawaii

Because survival of low birth-weight infants requiring intensive care has improved recently, particularly since the advent of exogenous surfactant therapy, we reviewed our experience at Kapiolani Medical Center for Women and Children (KMCWC) from 1989 to 1991 to determine if the incidence of retinopathy of prematurity (ROP), a serious long-term complication, had also increased. During this 3-year period, threshold disease, the ROP stage in which cryosurgery is recommended, occurred only in infants < or = 1000 grams. Seventy-four infants < or = 1000 grams were diagnosed with ROP of any stage. Sixteen eyes (9 infants) reached threshold; 14 were treated with cryosurgery. Six of these eyes have useful vision on follow up; 8 do not. Exogenous surfactant therapy had no significant effect on ROP incidence or severity in our series. Although ROP incidence did not increase during this review period, it remains a serious problem in high-risk premature infants in our Newborn Intensive Care Unit.

Registration of myometrial activity using multiple site electromyography in cyclic mares

A method for interpreting and analysing electromyographic (EMG) data of myometrial electrical activity was established. This method was used to study EMG activity in the uterus during the various stages of the oestrus cycle in mares. Recordings were analysed from four pairs of electrodes that were surgically implanted in the myometrium of four reproductively sound mares. The electrodes were placed at the tip, middle and base of the left horn and in the uterine body. Electrical activity was monitored by a polygraph. Data were transformed to a digitized form and statistically analysed. Myometrial electrical activity during oestrus and dioestrus was analysed for frequency (number of activity bursts per hour), duration (time elapsed from the start to the end of a burst) and intensity (peaks per minute). In addition, the degrees of synchronous activity among all of the monitored sites of the uterus were compared. The minimal amount of time of EMG recordings that allowed meaningful statistical analyses was determined to be 3.5 h during oestrus and 7 h during dioestrus. Variations in intensity of electrical activity were seen between the sites of implanted electrodes (P < 0.001). Electrical activity was highest in the middle of the horn and lowest in the uterine body. The frequency of activity bursts was the same during oestrus and dioestrus (4.35 +/- 0.22 and 4.44 +/- 0.20, respectively). The duration and intensity of uterine electrical activity depended on the stage of the oestrous cycle. The mean duration of uterine activity burst during dioestrus was significantly (P < 0.005) shorter during oestrus (3.32 +/- 0.18 min) than during dioestrus (5.7 +/- 0.39 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple site electromyography recordings of uterine activity following an intrauterine bacterial challenge in mares susceptible and resistant to chronic uterine infection

The electrical myometrial activity of three mares with a documented increased susceptibility to chronic uterine infection (CUI) and three mares considered to be resistant to CUI was investigated. Electrodes were surgically implanted in the myometrium of the mares and electrical activity was monitored by a Grass polygraph. Oestrus was determined by transrectal ultrasonography of the reproductive tract and teasing of the mares with a stallion. Findings were confirmed by blood progesterone concentrations < 0.1 ng ml-1. At the third day of oestrus or when a follicle > 35 mm was detected, the uterus was infused with a genital strain of 5 x 10(6) Streptococcus zooepidemicus. Myometrial electrical activity was monitored for 1-4 h before the bacterial infusion and continued until a visual stabilization of the activity occurred. No statistically significant differences in electrical myometrial activity were detected between susceptible and resistant mares before the infusion of bacteria into the uterus. A visible increase in myometrial electrical activity was seen in all mares following the bacterial infusion. However, the myometrial response of susceptible and resistant mares was different. Resistant mares demonstrated a greater myometrial activity (P < 0.001) than did susceptible mares. These differences were observed in frequency (P < 0.005) as well as duration (P < 0.001) and intensity (P < 0.001) of the uterine activity. Differences were most marked between 10 and 20 h after the intrauterine inoculation of bacteria. It was concluded from this study that myometrial activity is an important part of the uterine defence mechanism in mares.(ABSTRACT TRUNCATED AT 250 WORDS)

Anxiety and unrealistic optimism

Substantial evidence suggest that people tend to be unrealistically optimistic that positive events will happen to them and that negative events will not. However, recent research indicates that under certain conditions they may be unrealistically pessimistic. Variations in the levels of optimism and pessimism experienced towards events are generally given cognitive explanations. A relation between optimism and pessimism and anxiety, a variable related to emotion as well as cognition, was investigated in the present study. An inverse correlation was found between how anxious female students in England felt about certain negative events and how unrealistically optimistic they were about the occurrence of those events. It was concluded that the degree of anxiety experienced toward a negative event may affect the level of unrealistic optimism or pessimism toward it.