Characteristics of a monoclonal antibody to the thyrotropin receptor that acts as a powerful thyroid-stimulating autoantibody antagonist

Analysis of nine mouse monoclonal antibodies (mAbs) to the thyrotropin receptor (TSHR) with TSH antagonist activity showed that only one of the mAbs (RSR B2) was an effective antagonist of the human thyroid stimulating autoantibody M22. Crystals of B2 Fab were analyzed by x-ray diffraction and a crystal structure at 3.3 A resolution was obtained. The surface charge and topography of the B2 antigen binding site were markedly different from those of the thyroid-stimulating mAb M22 and these differences might contribute to the different properties of the two mAbs. B2 (but not other mouse TSHR-specific mAbs) was also an effective antagonist of thyroid stimulating autoantibody activity in 14 of 14 different sera from patients with Graves' disease. 125I-labeled B2 bound to the TSHR with high affinity (2 x 10(10) L/mol) and patient serum TSHR autoantibodies inhibited labeled B2 binding to the receptor in a similar way to inhibition of labeled TSH binding (r = 0.75; n = 20). Furthermore, labeled B2 binding was inhibited by patient serum TSHR autoantibodies with TSH antagonist activity and also by mouse and human thyroid stimulating mAbs. Overall, mAb B2 is a powerful antagonist of thyroid stimulating autoantibodies (and TSH) thus resembling closely patient serum TSH antagonist TSHR autoantibodies. Furthermore, B2 might have potentially important in vivo applications when tissues containing the TSHR (including those in the orbit) need to be made unresponsive to stimulating autoantibodies.

A multicenter in vivo proton-MRS study of HIV-associated dementia and its relationship to age

OBJECTIVE

Differences in diagnostic criteria and methods have led to mixed results regarding the metabolite pattern of HIV-associated brain injury in relation to neurocognitive impairment. Therefore, a multicenter MRS consortium was formed to evaluate the neurometabolites in HIV patients with or without cognitive impairment.

METHODS

Proton magnetic resonance spectroscopy (MRS) at short-echo time (30 ms) was assessed in the frontal white matter, basal ganglia, and parietal cortex of 100 HIV patients [61 with AIDS dementia complex (ADC) and 39 neuroasymptomatic (NAS)] and 37 seronegative (SN) controls.

RESULTS

Compared to SN, NAS had higher glial marker myoinositol-to-creatine ratio (MI/Cr) in the white matter (multivariate analyses, adjusted P=0.001), while ADC showed further increased MI/Cr in the white matter and basal ganglia (both P<0.001), and increased choline compounds (Cho)/Cr in white matter (P=0.04) and basal ganglia (P<0.001). Compared to NAS, ADC showed a reduction in the neuronal marker N-acetyl compound (NA)/Cr in the frontal white matter (P=0.007). CSF, but not plasma, viral load correlated with MI/Cr and Cho/Cr in white matter and NAA/Cr in parietal cortex. HIV infection and aging had additive effects on Cho/Cr and MI/Cr in the basal ganglia and white matter.

CONCLUSIONS

The results suggest that glial activation occurs during the NAS stages of HIV infection, whereas further inflammatory activity in the basal ganglia and neuronal injury in the white matter is associated with the development of cognitive impairment. Aging may further exacerbate brain metabolites associated with inflammation in HIV patient and thereby increase the risk for cognitive impairment.

MRSA in lower limb amputation and the role of antibiotic prophylaxis

AIM

Methicillin Resistant Staphylococcus Aureus (MRSA) colonisation is reported in 3-20% of vascular patients. Many develop infective complications. MRSA is associated with poor prognosis. Aim of the study is to assess MRSA in lower limb amputation and efficacy of antibiotic prophylaxis.

METHODS

Prospective study of lower limb amputation. MRSA screen and wound swabs were taken at operation. Antibiotic prophylaxis included teicoplanin (400 mg) 1 dose at operation.

RESULTS

Twenty-five patients underwent 33 primary amputations. At operation 15 legs (45%) were colonised with MRSA and 18 legs (58%) had active wound infection; MRSA (4) and other (14). Following surgery 3 patients died. Twenty-two legs (76%) had primary healing. Infection developed in 7 stumps (24%), MRSA (5) and Pseudomonas (2). Stump infection increased time to wound healing (p<0.0001). MRSA stump infection increased revision amputation (p=0.009) and duration of hospital stay (p<0.0074). MRSA wound infection at operation increased the risk of MRSA stump infection (p=0.007). Non-MRSA wound infection at operation was not associated with a worse outcome. No patient colonised with MRSA at operation developed postoperative MRSA stump infection.

CONCLUSIONS

MRSA is more prevalent that previously reported. MRSA infection has a poor prognosis. Prophylaxis may be effective for patients colonised with MRSA.

Multimodal imaging of somatosensory evoked cortical activity

Somatosensory evoked cortical activity is well investigated in both fMRI and MEG/EEG. Investigation with functional magnetic resonance spectroscopic (fMRS) imaging is relatively new and provides a means to image the metabolic activity of the brain. We for the first time combined fMRS, fMRI, MEG and EEG. This provides information about the metabolic, hemodynamic and electrical activity of the brain and also the verification of one imaging modality with the other. The dipolar source localized from the EEG/MEG data is in the vicinity of the fMRI activation site and also in the same area where lactate consumption is high as measured with fMRS imaging.

Characteristics of a human monoclonal autoantibody to the thyrotropin receptor: sequence structure and function

The properties of a human monoclonal antibody to the thyrotropin receptor (TSHR) (M22) with the characteristics of patient sera thyroid stimulating autoantibodies is described. Similar concentrations (pmol/L) of M22 Fab and porcine TSH had similar stimulating effects on cyclic adenosine monophosphate (cAMP) production in TSHR-transfected Chinese hamster ovary cells whereas higher doses of intact M22 immunoglobulin G (IgG) were required to cause the same level of stimulation. Patient sera containing TSHR autoantibodies with TSH antagonist (blocking) activity inhibited M22 Fab and IgG stimulation in a similar way to their ability to block TSH stimulation. Thyroid-stimulating monoclonal antibodies (TSmAbs) produced in mice inhibited 125I-TSH binding and 125I-M22 Fab binding to the TSHR but the mouse TSmAbs were less effective inhibitors than M22. These competition studies emphasized the close relationship between the binding sites on the TSHR for TSH, TSHR autoantibodies with TSH agonist activity, and TSHR autoantibodies with TSH antagonist activity. Recombinant M22 Fab could be produced in Escherichia coli and the recombinant and hybridoma produced Fabs were similarly active in terms of inhibition of TSH binding and cAMP stimulation. The crystal structure of M22 Fab was determined to 1.65 A resolution and is that of a standard Fab although the hypervariable region of the heavy chain protrudes further from the framework than the hypervariable region of the light chain. The M22 antigen binding site is rich in aromatic residues and its surface is dominated by acidic patches on one side and basic patches on the other in agreement with an important role for charge-charge interactions in the TSHR-autoantibody interaction.

The current role of intra-arterial thrombolysis

BACKGROUND

the role of intra arterial thrombolysis (IAT) in the management of peripheral vascular disease has come under scrutiny. This study aims to assess current usage and indications for IAT in the U.K.

METHOD

the use of IAT was assessed at our own centre and a questionnaire was sent to all centres that provide data for the U.K. "Thrombolysis Study Group".

RESULTS

there has been a steady decline in the use of IAT at our centre from a peak of 40 cases per annum to zero. Response was received from 22 of 24 centres (92%). Nineteen (86%) reported a decline in IAT use. Main reasons were concerns over lack of efficacy (74%) and complication rate (63%). Most centres would use IAT for acute limb ischaemia (86%). However, for acute thrombosis in specific indications the results varied; synthetic graft (82%), vein graft (54%), supra-inguinal graft (54%) and thrombosed popliteal artery aneurysm (54%). When asked what their commonest usage for IAT was, the results again varied; acute limb ischaemia (40%), graft thrombosis (40%), embolism post radiological intervention (12%), other (8%).

CONCLUSION

there has been a significant decrease in IAT use. Concerns exist as to efficacy and complication rate. There is no clear consensus on indications.

Human monoclonal thyroid stimulating autoantibody

A monoclonal autoantibody (MAb) with powerful thyroid stimulating activity has been produced from lymphocytes from a patient with Graves' disease. The autoantibody and its Fab fragment bind to the thyroid stimulating hormone (TSH) receptor (TSHR) with high affinity, inhibit labelled TSH binding to the receptor and stimulate cyclic AMP production in Chinese hamster ovary cells transfected with TSHR. TSHR autoantibodies with TSH agonist or antagonist activities from patients' serum samples are effective inhibitors of labelled monoclonal autoantibody binding to TSHR. Thus, the human monoclonal autoantibody has all the characteristics of serum TSHR autoantibodies. Its availability has important implications for new studies on the pathogenesis of Graves' disease.

The use of pharmacy immunization services in rural communities

Pharmacies have been recommended as alternative sites for the delivery of immunization services, especially to medically underserved adults and children in inner cities and rural areas. Currently, 35 of 50 states in the USA have legalized the administration of vaccines by pharmacists on the basis of certain training requirements and specific protocols. Since the role of pharmacists is expected to expand, it is important to assess the factors that would enable them to improve the delivery of immunization services and the acceptance of these services by communities. It is particularly important for pharmacists to have knowledge of community circumstances and be able to respond to community needs. This case study of a pharmacy immunization programme (PIP) in rural West Virginia assessed how well pharmacists were aware of community circumstances and which community factors affected the utilization of pharmacy-delivered immunizations. Our findings suggest that although pharmacists played important roles as facilitators, hosts and motivators in PIP, they overestimated the trust placed in them by community members. The convenient locations of pharmacies and the convenient times when they offered immunization services were found to be the determining factors of mothers' decisions to take their children to these places for their vaccinations. The study concludes that as the use of pharmacies as sources of immunization is expected to continue to expand, pharmacists should take these factors into consideration when they decide to offer immunizations.

Asthma in Head Start children: prevalence, risk factors, and health care utilization

PURPOSES

1. To identify the prevalence and severity of asthma in a Massachusetts Head Start program; 2. To identify associated risk factors for children with asthma; 3. To assess factors associated with health care utilization for asthma management.

METHOD

Parents of 316 Head Start children were interviewed using a close-ended survey questionnaire. Survey A was used for demographics and general health screening. Survey B documented more specific asthma information.

FINDINGS

There was a 35% prevalence rate of asthma in this preschool Head Start population. Most children had mild to moderate degrees of severity. Atopy, environmental triggers, and tobacco smoke exposure were common risk factors. Seventy-four percent of these children with asthma had used the emergency department at least once in their lifetime for asthma management. Forty-one percent had been hospitalized at least one time for asthma.

CONCLUSIONS

These findings are consistent with previous studies that support the need for asthma outreach and interventions in at-risk Head Start preschool populations.

Comparison of fMRI and PEPSI during language processing in children

The present study explored the correlation between lactate as detected by MR spectroscopy (MRS) and blood oxygenation level dependent (BOLD) responses in male children during auditory-based language tasks. All subjects (N = 8) participated in one proton echo planar spectroscopic imaging (PEPSI) and one functional magnetic resonance imaging (fMRI) session that required phonological and lexical judgments to aurally presented stimuli. Valid PEPSI data was limited in the frontal areas of the brain due to the magnetic susceptibility of the eye orbits and frontal sinuses. Findings from the remainder of the brain indicate that subjects show a significant consistency across imaging techniques in the left temporal area during the lexical task, but not in any other measurable area or during the phonological task. Magn Reson Med 45:217-225, 2001.