Biomedical subjects

J Zheng

Publications and source records attributed to J Zheng.

At least 73 records · Page 4Linked to original sources

PubMed2001

Proteomic analysis of human skin fibroblasts grown on titanium: novel approach to study molecular biocompatibility.

Despite the growing use of titanium as an implant material, there is a lack of consensus on what constitutes the molecular basis of its biocompatibility. In the present study we compared the response of skin fibroblasts to two different growth supporting surfaces: commercially pure titanium (cpTi) and tissue culture polystyrene (TCPS). Proteins from extracts of whole cells and adsorbed serum were separated and identified by 2-dimensional gel electrophoresis. In all, 40 proteins (46 spots) were identified by matrix-assisted laser desorption/ionization and mass spectrometry, database searching, immunoblotting, running a standard, or a combination of these techniques. Many of the proteins collected from the two surfaces were found to derive from the serum used in the culture medium. The surface properties of titanium appeared to promote the formation of a more concentrated carpet of serum proteins. Several proteins from bovine or human serum, such as albumin, alpha2-HS-glycoprotein, alpha-fetoprotein, plasminogen, thrombospondin 1, and serotransferrin, along with a few unidentified serum components, were found to adsorb onto cpTi in comparatively high concentrations. The adsorption of serum proteins did not appear to be selective on either substrate. We found that among the major cellular proteins, fibronectin and a cytoskeletal protein (non-muscle myosin heavy chain type A) were expressed at lower levels by fibroblasts grown on cpTi compared to TCPS. By analyzing the changes in the entire proteome of cells in response to different growth substrates, we may gain a better understanding of the molecular basis of biocompatibility.

Animals↗

PubMed2001

Coronary artery imaging: 3D segmented k-space data acquisition with multiple breath-holds and real-time slab following.

The purpose of this work was to develop a multiple-breath-hold (BH) imaging method for coronary arteries in which a segment of k-space is acquired in each BH. The goal was to increase the resolution, or the signal-to-noise ratio (SNR) and coverage, of three-dimensional-(3D)-BH volume-targeted scanning (VCATS). To correct for slab position differences, a real-time slab following technique using navigator echoes for motion detection was used. Sixteen normal volunteers were imaged to compare the method with a single-BH scan. Results showed that higher resolution, or larger coverage and higher SNR, were achieved by the multiple-BH method without respiratory motion artifacts. In conclusion, 3D segmented k-space data acquisition with multiple-BHs and real-time slab following is a promising approach for extending the capabilities of VCATS further.

Adult↗

PubMed2001

Coronary artery imaging using contrast-enhanced 3D segmented EPI.

The purpose of the work was to evaluate the effectiveness of extracellular contrast media in improving MR coronary angiography using breath-hold segmented echo-planar imaging (SEPI). Two protocols were designed to optimize the inversion recovery-prepared contrast-enhanced SEPI method. In 15 healthy volunteers, significant improvements in signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, and length of visualization were observed post-contrast. The method with two targeted scans to cover the left and right arteries, respectively, following separate 20-mL contrast injections, was found to yield thinner slices and longer right coronary artery (RCA) visualization than a single scan following a 40-mL contrast injection without compromising SNR and CNR. In conclusion, extracellular contrast media substantially improves the delineation of coronary arteries with SEPI. J. Magn. Reson. Imaging 2001;13:676-681.

Adult↗

PubMed2001

Contrast-enhanced coronary MR angiography: relationship between coronary artery delineation and blood T1.

Contrast-enhanced coronary angiography has become an important technique for magnetic resonance (MR) coronary artery imaging. However, the relationship between the quality of the coronary artery images and blood T1 has not yet been fully explored. In this paper, we assessed this relationship in an animal model by using a prototypical blood pool agent. With accumulated injections of this agent, the blood T1 would be maintained at different levels. The measured blood T1 values in vivo were 147 +/- 3, 82 +/- 6, 48 +/- 4, 40 +/- 3, and 30 +/- 8 msec (N = 7). Fixed and variable flip angle schemes were used in coronary artery imaging. The signal to noise ratios (SNR) of coronary arteries were measured and the image quality was assessed. It was found that blood T1 less than 80 msec might be desired. No statistically significant difference was observed between two flip angle schemes. There was better vessel definition using variable flip angle at blood T1 lower than 50 msec. Understanding this relationship may be beneficial to optimizing image protocol and/or design of blood pool contrast agents for contrast-enhanced coronary angiography.

Animals↗

PubMed2001

Three-dimensional MR pulmonary perfusion imaging and angiography with an injection of a new blood pool contrast agent B-22956/1.

Initial evaluation of a new blood pool agent, B-22956/1, for pulmonary imaging was performed in five domestic pigs with artificial embolism. Pre-embolism 3D pulmonary perfusion images were first acquired by injecting an extravascular agent, gadoteridol. The pulmonary arteries of the pigs were then occluded by the artificial emboli. Post-embolism perfusion scans were subsequently performed by injecting B-22956/1. Additional post-embolism high-spatial-resolution angiograms were also acquired. Parenchyma perfusion deficits were well depicted in the post-embolism perfusion maps. The post-embolism angiography clearly revealed the location and extent of the filling defects in the pulmonary vessels. Signal intensities of perfusion maps on the normal parenchyma were significantly improved (30%) by using B-22956/1, in comparison with perfusion images using gadoteridol (P < 0.01). Many pulmonary angiograms with approximately equal contrast could be obtained even at 22 minutes after the injection of B-22956/1. Our initial results indicate that blood pool agent B-22956/1 may provide opportunities for whole-lung-coverage perfusion mapping and additional high-resolution target angiograms after a single injection.

Animals↗

PubMed2001

Assessment of regional differences in myocardial blood flow using T2-weighted 3D BOLD imaging.

The feasibility of detecting regional differences in myocardial blood flow based on the blood oxygen level-dependent (BOLD) effect was evaluated in vivo in dogs (N = 9) using a 3D T2-prepared segmented gradient-echo sequence at 1.5 T. Regional differences in myocardial blood flow were created by administering adenosine through a catheter placed in the left circumflex coronary artery (LCX). The difference in the R2 (1/T2) relaxation rate between the left ventricular myocardial region supplied by the LCX and regions supplied by the left anterior descending coronary artery (LAD) or septal artery during adenosine administration was correlated to the corresponding regional myocardial blood flow difference determined using fluorescent microspheres. A correlation coefficient of 0.80 was found between the MR BOLD measurements and the myocardial flow assessment. Our results show that the sequence used in this study allows fast 3D BOLD imaging of the heart, and is a promising technique for detecting regional myocardial perfusion differences.

Animals↗

PubMed2001

HIV-1 infected and immune competent mononuclear phagocytes induce quantitative alterations in neuronal dendritic arbor: relevance for HIV-1-associated dementia.

Neuronal loss, alterations in dendritic arbor, and decreased synaptic density, in infected brain tissue, are neuropathological signatures of HIV-1-associated dementia (HAD). Brain mononuclear phagocyte (MP) (macrophage and microglia) secretory products can effect neuronal compromise, although the underlying mechanism(s) remain incompletely defined. To these ends, we quantitatively assessed the effects of virus-infected and/or immune activated MP secretory products on multiple aspects of neuronal morphology. Rat cortical and hippocampal neurons were exposed to secretory products from HIV-1-infected and lipopolysaccharide (LPS)-activated human monocyte-derived macrophage (MDM). Our assays for alterations in neuronal dendritic arbor and cell loss included the quantification of neurofilament (NF), neuron-specific enolase (NSE), and MAP-2 by ELISA and cellular morphology. MDM conditioned media (MCM) enhanced neuronal survival. HIV-1 infection or activation by LPS had modest neurotoxic effects. In contrast, the combination of HIV-1 infection and activation of MDM produced significant neurotoxicity. Such MDM products altered dendritic arbor, decreased synaptic density, and increased LDH release. Comparable neurotrophic/toxic responses were observed when neurons were exposed to MCM collected from 12 separate human donors. Similar responses were observed with MCM from human fetal microglia, further supporting the role of HIV-1-infected and immune-activated brain MP in the overall neurotoxic responses. This work provides quantitative measures of neuronal damage by which virus infected and activated MP can elicit neuronal injury in HAD.

Journal Article↗

PubMed2001

HIV-1 infected immune competent mononuclear phagocytes influence the pathways to neuronal demise.

Secretory products from HIV-1-infected immune-competent mononuclear phagocytes (MP) damage neuronal dendritic arbor (Zheng et al., 2001). The mechanism behind neuronal injury and whether it is species and/or viral strain dependent is not fully understood. To these ends, we investigated whether HIV-1-infected and lipopolysaccharide (LPS)-activated MDM elicit neuronal injury in primary human neurons. Neuronal damage was compared to that seen in rat neurons. Utilizing a spectrum of HIV-1 strains to infect human monocyte-derived macrophages (MDM), productive viral replication proved necessary, but not sufficient, for neuronal injury. Neuronal demise was induced by virion-free HIV-1-infected and immune-activated MDM culture supernatants. Maximal alterations in glutamate mediated neuronal signaling, resulted from exposure to secretory products from HIV-1-infected and immune-activated MDM. Apoptosis was the predominant mechanism of cell death induced by HIV-1-infected and LPS-treated MDM. Importantly, neuronal injury and increases in calcium influx mediated by HIV-1-infected and immune-activated MDM culture supernatants was partially blocked by the N-methyl D-aspartate (NMDA) receptor antagonist, MK 801. These data support a primary role for immune-activation in MP neurotoxic activities. The upregulation of NMDA receptor sensitive soluble factors and neuronal apoptosis by HIV-1-infected and immune-activated MDM provide unique insights into links between soluble factors, produced as a consequence of MP immunity, and neuronal demise in HAD.

Journal Article↗

PubMed2001

Pharmacokinetics of thrombin-like enzyme from venom of Agkistrodon halys ussuriensis Emelianov determined by ELISA in the rat.

A thrombin-like enzyme (TLE) was separated and purified from the venom of a northeast Chinese snake Agkistrodon halys ussuriensis Emelianov. Experiments were performed in rats to determine the pharmacokinetic parameters following an intravenous (i.v.) or a subcutaneous (s.c.) injection of the thrombin-like enzyme. The plasma levels of TLE were estimated by enzyme-linked immunosorbent assay. The method exhibited high reproducibility and accuracy in correlating optical densities with TLE concentrations (0.2-30 ng ml(-1), r=0.99). The plasma concentration-time course after i.v. administration of 50 microg kg(-1) TLE was well fitted by a two-compartment open model. The half-life of the alpha-phase was 18.0+/-3.2 min, and that of the beta-phase 3.9+/-0.7h. The apparent volume of distribution was 1.8+/-0.5l kg(-1), and clearance was 5.4+/-0.5 ml min(-1) kg(-1). When the TLE was injected s.c. at a dose of 0.75 mg kg(-1), the changes in plasma concentration were best described by a two-compartment model with a first-order absorption. The maximal plasma level of 51+/-2.7 ng ml(-1) was reached at 5.2+/-0.5h. The absorption rate constant was 0.3+/-0.03 h(-1). The area under the plasma concentration-time curve (AUC) was 2.8+/-0.8 microg h(-1) ml(-1).

Agkistrodon↗

PubMed2001

ATP stimulated cyclic AMP formation in bovine chromaffin cells is enhanced by neuropeptide Y.

ATP increases cAMP formation in bovine chromaffin cells, EC(50) = 7.1 x 10(-6) M. NPY, EC(50) = 4.1 x 10(-8) M, increases the efficacy of ATP (1.5-2 fold). Inclusion of the selective Y1 receptor antagonist 1229U91 produced a decrease in NPY potency (EC(50) = 2.7 x 10(-7) M). PTX pretreatment did not abolish either the effect of ATP nor the enhancement by NPY. NPY could also enhance the ability of angiotensin and bradykinin to increase cAMP formation. The selective phospholipase C inhibitor, U73122, and the selective protein kinase C inhibitors, bisindolylmaleimide I and RO-31-8425, were effective inhibitors of the enhancing effect of NPY.

Adenosine Triphosphate↗

PubMed2001

Electrically evoked otoacoustic emissions from apical and basal perilymphatic electrode positions in the guinea pig cochlea.

Stimulation of the cochlea with sinusoidal current results in the production of an otoacoustic emission at the primary frequency of the stimulus current. In this study we test the hypothesis that the wide frequency response from round window (RW) stimulation is due to the involvement of a relatively large spatial segment of the organ of Corti. Tonotopically organized group delays would be evident from perilymphatic electrode locations that restrict the spatial extent of hair cell stimulation. Monopolar and bipolar-paired stimulus electrodes were placed in perilymphatic areas of the first or third cochlear turns and the electrically evoked otoacoustic emissions (EEOAE) produced by these electrodes were compared to that from the RW monopolar electrode in the anesthetized guinea pig. Current stimuli of 35 microA RMS were swept across the frequency range between 60 Hz and 100 kHz. The EEOAE was measured using a microphone coupled to the ear canal. It was found that the bandwidth of EEOAEs from RW stimulation extended to at least 40 kHz and was a relatively insensitive to electrode location on the RW. The group delay of the EEOAE from stimulation at the RW membrane (corrected to stapes motion) was about 53 micros. First and third turn stimulations from electrode placements in perilymph near the bony wall of cochlea yielded narrower band EEOAE magnitude spectra but which had the same short group delays as for RW stimulation. A confined current (from a bipolar electrode pair) applied close to the basilar membrane (BM) in the first turn produced the narrowest frequency-band magnitude emissions and a mean corrected group delay of 176 micros for a location approximately 3 mm from the high frequency end of the BM (corresponding to about the 18 kHz best frequency location). Bipolar electrodes in the third turn scala tympani produced low pass EEOAE magnitude functions with corrected group delays ranging between approximately 0.3 and 1 ms. The average phase slopes did not change with altered cochlear sensitivity and postmortem. These data indicate that the EEOAE from RW stimulation is the summed response from a wide-tonotopic distribution of outer hair cells. A preliminary model study indicates that short time delayed emissions are the result of a large spatial distribution of current applied to perilymphatic locations possibly giving rise to "wave-fixed" emissions.

Animals↗

PubMed2001

Quinine-induced alterations of electrically evoked otoacoustic emissions and cochlear potentials in guinea pigs.

Quinine is a well-known ototoxic drug which may affect portions of the auditory system with different biochemical effects, causing reversible hearing loss and tinnitus. Recent investigations indicate that quinine at high concentrations can act directly on cochlear outer hair cells to affect their motility and the mechanical response of the basilar membrane. This study aimed to investigate the effect of quinine on the electromotility of outer hair cells in vivo by means of measuring the electrically evoked otoacoustic emissions (EEOAEs), and the relationship between EEOAE and hearing sensitivity alterations in guinea pigs. Quinine was infused into the scala tympani with concentrations between 0.05 and 5 mM. An alternating current (35 microA RMS) swept from 400 Hz to 40 kHz was applied to the round window to evoke the EEOAE. The compound action potential (CAP), cochlear microphonic (CM) and summating potential (SP) were also measured. Results show that quinine affects the EEOAE in a dose-dependent manner and that its effects are reversible. Two aspects of the EEOAE were affected by quinine, depending on concentration: (1) the 'fine structure' only for concentrations below 0.1 mM and (2) the overall amplitude and the 'fine structure' for concentrations above 0.1 mM. At 5 mM the fine structure was completely absent and the mean amplitude of the EEOAE greatly decreased. Multiple component analysis shows the short delay component of the EEOAE is related to the mean value of the amplitude spectrum while the long delay component is related to the fine structure. The alterations of the EEOAE are roughly comparable to that of the cochlear potentials. A 'threshold concentration' for quinine's effects was found at 25 microM. CAP was significantly affected at 25 microM while EEOAE, CM and SP were not. Enhancement of the EEOAE amplitude was noticed in five out of 20 animals in the current study. The enhancement appears only related to the EEOAE mean level or short delay component. The results suggest that quinine can affect in vivo electromotility of outer hair cells at low concentration and therefore change the cochlear amplifier performance via an effect on electro-mechanical transduction. Its effects on the cochlear spiral ganglion neurons and/or their presynaptic process are also suggested, and these are speculated to be the primary sites for quinine's effects on the auditory system.

Action Potentials↗

PubMed2001

Development of acetylcholine receptors in cultured outer hair cells.

Efferents, originating in the superior olivary complex, preferentially synapse with cochlear outer hair cells (OHCs), with acetylcholine (ACh) as their primary neurotransmitter. The OHC ACh receptors (AChRs), which have unusual pharmacology, have been cloned and identified as a new subunit (alpha9) of the nicotinic AChR family. The expression of alpha9 AChRs is first detected before birth and peaks between 6 and 10 days after birth (DAB) in developing mice and rats, while functional maturation of the receptor, as determined by measuring the ACh-induced currents, takes place between 6 and 12 DAB. In this study we attempted to examine the development of AChRs in OHCs grown in explanted cultures, deprived of efferent innervation. ACh-induced currents were used as an assay. Reverse transcription-PCR analysis was also performed to detect the expression of alpha9 subunit from cultured OHCs. PCR study indicates that mRNA of the alpha9 subunit was expressed in primary cochlear cultures, similar to that seen in the cochleae of developing animals. Measurement of whole-cell currents showed that ACh-induced outward current was first detected around 5 days in a fraction of cultured OHCs. The number of responsive cells increased between 5 and 12 days in culture. The size of ACh-induced currents also increased during this period. These results suggest that the development of AChRs in cultured OHCs is not affected by removal of efferent innervation.

Acetylcholine↗

PubMed2001

Four new triterpenoid saponins from Conyza blinii.

Three new bisdesmosidic saponins named conyzasaponins A, B, and C (1-3) and one new monodesmosidic saponin, conyzasaponin G (4), were isolated from the aerial parts of Conyza blinii. Their structures were elucidated on the basis of extensive NMR (DEPT, DQF-COSY, HOHAHA, HMQC, HMBC, and NOESY) and MS studies. Compounds 1-3 share a common prosapogenin, bayogenin 3-O-beta-D-xylopyranosyl-(1-->3)-beta-D-glucopyranoside, which is identical with conyzasaponin G (4), and differ in the structures of the ester-linked sugar moieties at C-28. Conyzasaponin A (1) is the 28-O-beta-D-apiofuranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl ester, conyzasaponin B (2), the 28-O-beta-D-apiofurano- syl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->3)]-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl ester, and conyzasaponin C (3), the 28-O-alpha-L-rhamnopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-[beta-D-apiofuranosyl-(1-->3)]-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl ester of the prosapogenin, respectively.

Carbohydrate Sequence↗

PubMed2001

Integrated pest management of two-spotted mite Tetranychus urticae on greenhouse roses using petroleum spray oil and the predatory mite Phytoseiulus persimilis.

From 1995 to 1999, four experiments were conducted on greenhouse roses to assess the effectiveness of the nC24 petroleum spray oil (PSO), D-C-Tron Plus, against two-spotted mite, Tetranychus urticae Koch (Acarina: Tetranychidae), and to determine how the oil could be most efficiently and effectively used in combination with the predatory mite Phytoseiulus persimilis Athias-Henriot (Acarina: Phytoseiidae) in an integrated pest management program. The results showed that 0.5% PSO applied fortnightly to roses gave excellent protection from T urticae infestation when the mite population was not already established. However, PSO applied after roses were infested with T. urticae above the economic threshold only stabilised populations without reducing them below that threshold. Populations of P. persimilis in the upper and lower canopies were unchanged after two sprays of PSO at 7-day intervals, and application of PSO to the upper canopy was as effective in controlling T. urticae in the presence of P persimilis as spraying the entire plant. Combining PSO with P. persimilis gave better control of T. urticae than using P. persimilis alone. The most cost-effective use of PSO in the presence of P. persimilis is, therefore, to apply spray only to the upper canopy. This will not affect control of powdery mildew with PSO. Comparison of a control program for T urticae based on the monitored use of synthetic miticides with that based on calendar application of PSO revealed that both gave equally effective control. The benefits of combining PSO and P. persimilis in an integrated pest management program for T. urticae on roses over a program based on synthetic fungicides are discussed.

Animals↗

PubMed2001

An in-frame deletion in the alpha(2C) adrenergic receptor is common in African--Americans.

alpha(2) adrenergic receptors are activated by adrenaline and noradrenaline, and three subtypes (ie, A, B, C) have differential affinities for antagonists and medications. The alpha(2c) adrenergic receptor (ADRA2C), located on chromosome 4p16.3, is a candidate gene for schizophrenia because it binds clozapine, an atypical neuroleptic useful for treatment-resistant schizophrenia. In addition, ADRA2C binds clonidine which is prescribed for three psychiatric diseases. This report communicates the findings of the genetic scanning of this gene of very tough GC content. The complete coding sequences and splice junctions were scanned with [DOVAM]-S in 104 schizophrenics, and pilot probes of patients with alcoholism (41 patients), cocaine abuse (25 patients), puerperal psychosis (30 patients), attention deficient/hyperactivity disorder (25 patients) and autism (25 patients). Six sequence variants were found, including five silent polymorphisms (allele frequencies 0.6--25%) and an in-frame deletion of a homologous repeat at nucleotides 967--978 (ie, TIDRU(1)). Genotyping of the normal two repeat unit of the Third Intracytoplasmic Domain Repeat Unit (TIDRU(2)) and the deleted variant (TIDRU(1)) revealed that TIDRU(1) had allelic frequencies of 39% (11/28) and 3.5% (6/172) in African-American and Caucasian schizophrenics, respectively, and it occurred with equal frequency in controls (44%, 31/70 and 3.0%, 6/198). TIDRU(1) occurs at a location similar to the third intracytoplasmic 48-nucleotide repeat unit in the DRD4 that is associated with ADHD. Although these data do not suggest an association of TIDRU(1) with schizophrenia, additional studies are needed to see whether TIDRU(1) confers a clinical phenotype.

Black People↗

PubMed2001

A comparison of adapalene gel 0.1% vs. tretinoin gel 0.025% in the treatment of acne vulgaris in China.

AIM: To compare the efficacy, safety and tolerability of adapalene gel 0.1% vs. tretinoingel 0.025% in a Chinese patient population. BACKGROUND: Although acne vulgaris is a common problem among Asians and Asian-Americans, little has been published on the specific manifestations, sequelae, and treatment-responsiveness of this disorder in Asian skin types. Since Asian skin types tend to be more highly pigmented than those of white people of European descent, many Asians share the predisposition toward postinflammatory hyperpigmentation seen in Africans, African-Americans and other dark-skinned peoples. It is generally assumed that the efficacy and safety of topical retinoids is the same in Asians as in white people. Tretinoin has been available in China for decades; adapalene became available in 1998. METHODS: A total of 150 patients with grade II-III acne vulgaris seen at three dermatology clinics were randomized to 8 weeks of daily treatment with either adapalene gel 0.1% or tretinoin gel 0.025%. Counts of total lesions, inflammatory lesions and non-inflammatory lesions were made at baseline and again at treatment weeks 2, 4, 6 and 8. Global assessment ratings, based on percent lesion reduction from baseline were also made. Erythema, burning, pruritus, scaling and dryness were rated on a 0-3 severity scale. RESULTS: A total of 139 patients completed the efficacy evaluation, and 144 patients completed the safety evaluation. Both adapalene and tretinoin produce dramatic reductions in total, inflammatory and non-inflammatory lesion counts, in the range of 69-74% on average. More than 70% of patients in both groups had complete clearance or marked improvement. In general, irritation was mild, but was both more common and more severe in the tretinoin group vs. the adapalene group. No systemic side effects were seen. CONCLUSIONS: Adapalene offers comparable efficacy to tretinoin, but is less irritating. It represents a good alternative for the treatment of mild to moderate acne vulgaris in Chinese patients.

Acne Vulgaris↗

PubMed2001

Characterization of a novel hepatitis B virus mutant: demonstration of mutation-induced hepatitis B virus surface antigen group specific "a" determinant conformation change and its application in diagnostic assays.

We report and characterize a novel mutant of the hepatitis B virus surface antigen (HBsAg). The mutant was isolated from a symptomatic patient who was found to be persistently positive for both HBsAg and anti-hepatitis B surface antibody (anti-HBs) and a long-lasting anti-HBc (core) IgM. Due to the unusual immune serological profile, polymerase chain reaction and sequencing were performed and revealed a genotype D mutant HBV (LBN). Aligned with known HBsAg sequences from GenBank, the LBN variant matched to consensus subtype ayw2 and revealed five mutation positions. Interestingly, none of the mutations was found within the group-specific "a" determinant region (124-147) and, specifically, two of the five mutations, T118K and P120Q, were located only a few amino acids adjacent to the 124-147 region. Using a panel of six monoclonal antibodies and vaccine raised human neutralizing antibodies, the recombinant wild-type HBsAg and the novel variant LBN HBsAg were investigated for their immunological reactivity. Vaccine raised human anti-HBs showed less reactivity to the variant LBN HBsAg than to wild-type HBsAg in enzyme immune assays. Furthermore, our observations demonstrate the influence of adjacent residues on the group-specific "a" determinant structural configuration; this resulted in severe antigenic changes of the immunodominant region as well as in the subtype serology. The importance of the variant LBN lies in the observation that mutations close to the "a" determinant can change the immunodominant region structure and therefore alter the group specific determinant antigenicity even though no mutations are present within this region. Hence, the classical definition of the "a" determinant cluster may need to be extended to cover a broader region to include the requirement of adjacent amino acids to support its conformation. In conclusion, by understanding the HBsAg major immunodominant region structure and by using a combination of antibodies with specificity covering all key mutation locations, maximal anti-HBs-based protection, and highly sensitive diagnostic assays can be achieved.

Adult↗