Computerized detection of masses from digitized mammograms: comparison of single-image segmentation and bilateral-image subtraction

RATIONALE AND OBJECTIVES

Two methods--single-image segmentation and bilateral-image subtraction--have been used commonly as the first stage in computer-aided detection (CAD) schemes to detect masses on digitized mammograms. In the current study, we investigated and compared the advantages and disadvantages of the two methods in achieving a high sensitivity for mass detection.

METHODS

Two CAD schemes were tested. One used Gaussian filtering based on single-image segmentation, and the other used bilateral-image subtraction based on left-right image pairs to identify suspicious mass regions. A clinical database that contained 152 verified mass cases was used to compare the two approaches.

RESULTS

The single-image segmentation method yielded 100% sensitivity and had a somewhat higher number of initial suspicious regions. The bilateral-image subtraction method missed several true-positive regions at the initial phase. Each approach achieved more than 90% sensitivity at a false-positive rate of approximately 0.8 per image.

CONCLUSION

Optimal initial image segmentation schemes may depend on the complete detection and classification method used. Single-image segmentation methods may perform comparably with bilateral-image segmentation schemes, and these techniques appear to be more versatile and easily adaptable to future clinical CAD applications.

In situ studies of the primary immune response to (4-hydroxy-3-nitrophenyl)acetyl. IV. Affinity-dependent, antigen-driven B cell apoptosis in germinal centers as a mechanism for maintaining self-tolerance

Germinal centers (GCs) are the sites of antigen-driven V(D)J gene hypermutation and selection necessary for the generation of high affinity memory B lymphocytes. Despite the antigen dependence of this reaction, injection of soluble antigen during an established primary immune response induces massive apoptotic death in GC B cells, but not in clonally related populations of nonfollicular B lymphoblasts and plasmacytes. Cell death in GCs occurs predominantly among light zone centrocytes, is antigen specific, and peaks within 4-8 h after injection. Antigen-induced programmed death does not involve cellular interactions mediated by CD40 ligand (CD40L) or Fas; disruption of GCs by antibody specific for CD40L was not driven by apoptosis and C57BL/6.lpr mice, though unable to express the Fas death trigger, remained fully susceptible to soluble antigen. Single injections of antigen did not significantly decrease GC numbers or average size, but repeated injections during an 18-h period resulted in fewer and substantially smaller GCs. As cell loss appeared most extensive in the light zone, decreased GC cellularity after prolonged exposure to soluble antigen implies that the Ig- centroblasts of the dark zone may require replenishment from light zone cells that have survived antigenic selection. GC cell death is avidity-dependent; oligovalent antigen induced relatively little apoptosis and GC B cells that survived long exposures to multivalent antigen expressed atypical VDJ rearrangements unlikely to encode high affinity antibody. Antigen-induced apoptotic death in GCs may represent a mechanism for the peripheral deletion of autoreactive B cell mutants much as the combinatorial repertoire of immature B lymphocytes is censored in the bone marrow.

Computerized detection of masses in digitized mammograms using single-image segmentation and a multilayer topographic feature analysis

RATIONALE AND OBJECTIVES

We developed and evaluated a computer-aided detection (CAD) scheme for masses in digitized mammograms.

METHODS

A multistep CAD scheme was developed and tested. The method uses a technique of single-image segmentation with Gaussian bandpass filtering to yield a high sensitivity for mass detection. A rule-based multilayer topographic feature analysis method is then used to classify suspected regions. A set of 260 cases, including 162 verified masses, was divided into two subsets; one set was used to set the rule-based classification and one was used to test the performance of the scheme.

RESULTS

In a preliminary clinical study, the implemented detection scheme yielded 98% sensitivity with a false-positive detection rate of less than one false-positive region per image.

CONCLUSION

Single-image segmentation methods seem to have high sensitivity in selecting true-positive mass regions in the first stage of a CAD scheme. A multilayer topographic image feature analysis method in the second stage of a CAD scheme has the potential to significantly reduce the false-positive detection rate.

Therapeutic potentiation of the immune system by costimulatory Schiff-base-forming drugs

Immune responses are orchestrated by CD4 T lymphocytes, which receive a cognitive signal when clonally distributed receptors are occupied by major histocompatibility complex (MHC) class II-bound peptides on antigen-presenting cells (APCs). The APCs provide costimulatory signals, through macromolecules such as CD80, that regulate outcomes in terms of T-cell activation or anergy. We have studied essential complementary chemical events in the form of Schiff base formation between carbonyls and amines that are constitutively expressed on presenting cell and T-cell surfaces and provide a new target for manipulation of immune responses. Here we show that small Schiff base-forming molecules can substitute for the physiological donor of carbonyl groups and provide a costimulatory signal to CD4 Th-cells through a mechanism that activates clofilium-sensitive K+ and Na+ transport. One such molecule, tucaresol, enhances CD4 Th-cell responses, selectively favouring a Th1-type profile of cytokine production. In vivo tucaresol potently enhances CD4 Th-cell priming and CD8 cytotoxic T-cell priming to viral antigens, and has substantial therapeutic activity in murine models of disease.

Computer-aided detection of clustered microcalcifications in digitized mammograms

RATIONALE AND OBJECTIVES

We investigated a computer-aided detection (CAD) scheme for clustered microcalcifications in digitized mammograms.

METHODS

A multistage CAD scheme was developed and tested. To increase sensitivity, the scheme uses a Gaussian band-pass filter and nonlinear threshold. A multistage local minimum searching routine and a multilayer topographic feature analysis are used to reduce the false-positive detection rate. One hundred ten digitized mammograms were used in this preliminary test, with 55 images containing one or two verified microcalcification clusters.

RESULTS

The CAD scheme achieved 100% sensitivity and had an average false-positive detection rate of 0.18 per image.

CONCLUSION

The CAD scheme performs as well as many published schemes and has some unique advantages to further improve detection sensitivity and specificity of future CAD schemes.

Cellular interaction in germinal centers. Roles of CD40 ligand and B7-2 in established germinal centers

Costimulatory interactions between T and B lymphocytes are crucial for T cell activation and B cell proliferation and differentiation. We have compared the roles of CD40L and B7-2 in the initiation and maturation of humoral immunity by administering anti-CD40 ligand (L) or anti-B7-2 Ab during the early (days -1 to 3) or late (days 6-10) phases of primary responses to thymus-dependent (Td) and -independent (Ti) Ags. Germinal center (GC) formation in response to a Td Ag was inhibited completely by the early administration of anti-CD40L or anti-B7-2 Abs. Later in the response, established GCs remained sensitive to anti-CD40L but were resistant to treatment with anti-B7-2. However, Ig hypermutation was reduced dramatically in GCs of anti-B7-2-treated mice and humoral memory was impaired. Early administration of anti-CD40L reduced serum Ab levels to approximately 10% of controls, whereas early treatment with anti-B7-2 reduced Ab production by only 50%. Later treatments with either Ab had no effect on Ab production. Response to a type II Ti Ag was more resistant than Td responses to interruption of costimulatory interactions. Our findings suggest that the costimulatory roles of CD40:CD40L and B7-2:CD28/CTLA-4 differ in the GC; administration of anti-CD40L abrogates an established GC reaction, whereas Ab to B7-2 suppresses Ig hypermutation and entry into the B cell memory compartment. Once B cells have entered the differentiation pathway to Ab production, neither CD40L nor B7-2 is necessary for their continued differentiation and persistence.

Cellular interaction in germinal centers. Roles of CD40 ligand and B7-2 in established germinal centers

Costimulatory interactions between T and B lymphocytes are crucial for T cell activation and B cell proliferation and differentiation. We have compared the roles of CD40L and B7-2 in the initiation and maturation of humoral immunity by administering anti-CD40 ligand (L) or anti-B7-2 Ab during the early (days -1 to 3) or late (days 6-10) phases of primary responses to thymus-dependent (Td) and -independent (Ti) Ags. Germinal center (GC) formation in response to a Td Ag was inhibited completely by the early administration of anti-CD40L or anti-B7-2 Abs. Later in the response, established GCs remained sensitive to anti-CD40L but were resistant to treatment with anti-B7-2. However, Ig hypermutation was reduced dramatically in GCs of anti-B7-2-treated mice and humoral memory was impaired. Early administration of anti-CD40L reduced serum Ab levels to approximately 10% of controls, whereas early treatment with anti-B7-2 reduced Ab production by only 50%. Later treatments with either Ab had no effect on Ab production. Response to a type II Ti Ag was more resistant than Td responses to interruption of costimulatory interactions. Our findings suggest that the costimulatory roles of CD40:CD40L and B7-2:CD28/CTLA-4 differ in the GC; administration of anti-CD40L abrogates an established GC reaction, whereas Ab to B7-2 suppresses Ig hypermutation and entry into the B cell memory compartment. Once B cells have entered the differentiation pathway to Ab production, neither CD40L nor B7-2 is necessary for their continued differentiation and persistence.

Construction and high expression of retroviral vector with human clotting factor IX cDNA in vitro

The construction of the high titer and highly expressed safety retroviral vector carrying human clotting factor IX cDNA is reported. Retroviral vectors LNCIX, LIXSN and LCIXSN, driven by hCMV, LTR and hCMV combined with LTR promoter respectively, were constructed, based on the retroviral vector LNL6, and transferred into packaging cell line PA317 with electroporation. Human clotting factor IX was detected in the cultured cells transduced with LNCIX and LIXSN but not in the cells transduced with LCIXSN. The viral titer of PA317/LNCIX was 800,000 CFU per mL. With ELISA detection, it was found that the cells transduced with this vector can express human clotting factor IX at the level of 3.3 micrograms per 10(6) cells in 24 h in human fibrosarcoma cells HT-1080 and 2.5 micrograms per 10(6) cells in 24 h in hemophilia B patients' skin fibroblast HSF cells, and more than 80% of them were biologically active. The viral titer and expression of human FIX were increased, and the construction of retroviral vector backbone was improved and the safety was guaranteed as compared to those vectors used previously. These vectors may produce a sufficient quantity of factor IX proteins to cause the phenotypic modification for hemophilia B patients.

Galactose oxidation as a potent vaccine adjuvant strategy. Efficacy in murine models and in protection against a bovine parasitic infection

Potent immunological adjuvants are urgently required to complement subunit protein and peptide vaccines in prophylactic and therapeutic vaccination. Carbonyl-amino condensations, which are essential to the inductive interaction between antigen-presenting cells and T-helper cells, were tested as a target for the enhancement or immune responses to vaccine antigens. Enzymic oxidation of cell surface galactose by the novel adjuvant NAGO, to increase amine-reactive carbonyl groups on lymphocytes and antigen-presenting cells, provided a potent noninflammatory method of enhancing the immunogenicity of viral, bacterial, and protozoal subunit vaccines in mice. In pilot protection studies with a glutathione-S-transferase vaccine against bovine Fasciola hepatica, a formulation containing NAGO as sole adjuvant agent proved very effective in inducing protection. In terms of protection in individual animals, NAGO alone was better than Quil A emulsified in squalene Montanide (five of eight animals were protected better than 80% by NAGO; four of eight animals were protected better than 93% by NAGO; two of eight animals were protected better than 80% by QA/SM). QA/SM (69% mean protection) was, however, more consistent overall than NAGO (65% mean protection). NAGO proved more effective in murine models when combined with muramyl dipeptide, but this combination has yet to be tested in protection studies.

Effect of cortisol on energy expenditure and amino acid metabolism in humans

Hydrocortisone was infused overnight into nine normal healthy adults on three occasions at 0, 80, and 200 micrograms.kg-1.h-1, producing plasma cortisol concentrations of 10.6 +/- 1.2, 34.0 +/- 2.0, and 64.9 +/- 4.3 micrograms/dl, respectively. L-[1-13C]leucine, L-[phenyl-2H5]phenylalanine, and L-[2-15N]glutamine were infused during the last 7 h of hypercortisolemia to measure amino acid kinetics. During the last 3.5 h, somatostatin, glucagon, and insulin were infused to reduce the cortisol-induced elevation in plasma insulin to basal. Hypercortisolemia increased plasma glucose, free fatty acid (FFA), and insulin concentrations. Institution of the somatostatin clamp returned insulin to basal but increased glucose and FFA. Acute hypercortisolemia increased protein breakdown 5-20%, as measured by increases in leucine and phenylalanine appearance rates. Normalizing insulin during hypercortisolemia did not alter phenylalanine flux but enhanced leucine appearance rate, the latter result indicating that insulin was affecting leucine metabolism during hypercortisolemia. The fraction of the leucine flux that was oxidized was not significantly increased with hypercortisolemia, but disposal by the nonoxidative route of leucine uptake for protein synthesis was increased. Hypercortisolemia increased cycling of amino acids by increasing protein breakdown and synthesis, but the increase in this process could have increased resting energy expenditure (REE) only 1-2%. Hypercortisolemia increased glutamine flux in a dose-dependent fashion through an increase in de novo synthesis, which presumably reflects increased release from skeletal muscle. Hypercortisolemia increased REE 9-15% at the 80 and 200 micrograms.kg-1.h-1 infusion rates. Respiratory quotient did not rise with cortisol infusion but tended to decrease, suggesting that the increase in REE was fueled by increased oxidation of fat. These data demonstrate that hypercortisolemia increases metabolic rate and may be in part responsible for the hypermetabolic state in injury.

Structurally related but functionally distinct yeast Sm D core small nuclear ribonucleoprotein particle proteins

Spliceosome assembly during pre-mRNA splicing requires the correct positioning of the U1, U2, U4/U6, and U5 small nuclear ribonucleoprotein particles (snRNPs) on the precursor mRNA. The structure and integrity of these snRNPs are maintained in part by the association of the snRNAs with core snRNP (Sm) proteins. The Sm proteins also play a pivotal role in metazoan snRNP biogenesis. We have characterized a Saccharomyces cerevisiae gene, SMD3, that encodes the core snRNP protein Smd3. The Smd3 protein is required for pre-mRNA splicing in vivo. Depletion of this protein from yeast cells affects the levels of U snRNAs and their cap modification, indicating that Smd3 is required for snRNP biogenesis. Smd3 is structurally and functionally distinct from the previously described yeast core polypeptide Smd1. Although Smd3 and Smd1 are both associated with the spliceosomal snRNPs, overexpression of one cannot compensate for the loss of the other. Thus, these two proteins have distinct functions. A pool of Smd3 exists in the yeast cytoplasm. This is consistent with the possibility that snRNP assembly in S. cerevisiae, as in metazoans, is initiated in the cytoplasm from a pool of RNA-free core snRNP protein complexes.

Locus-specific somatic hypermutation in germinal centre T cells

Somatic hypermutation and affinity-driven selection of active immunoglobulin genes occur in germinal centres (GCs), resulting in the generation of high-affinity memory B cells. In contrast, T lymphocytes do not require the germinal centre microenvironment to establish memory and the T-cell antigen receptor (TCR) genes, though homologous to immunoglobulin genes, are believed to be incapable of hypermutation. Here we present direct evidence that the small population of antigen-specific T cells that are recruited into splenic GCs acquire mutations in the variable region of genes encoding TCR alpha-chains (V alpha) but not those of beta-chains. These locus-specific mutations reach frequencies comparable to mutated immunoglobulin VH exons recovered from the same site and exhibit similar substitution biases and DNA strand polarity. T cells bearing identical mutations appear in multiple GCs, raising the possibility that some cells bearing mutant TCRs may re-enter the peripheral lymphocyte pool.

Fractal analysis of trabecular patterns in projection radiographs. An assessment

RATIONALE AND OBJECTIVES

Fractal analysis of digitized images has been investigated in recent years as a potential measure of structural bone strength. Several technical issues associated with such measurements are assessed.

METHODS

In a series of experiments using a hand phantom, the effects of system noise and modulation transfer function on fractal dimension were explored. The authors evaluated a method for correcting the estimated power spectrum using a step-wedge image exposed and digitized under identical conditions as a reference.

RESULTS

System noise and modulation transfer function significantly affect estimated fractal dimension in bony regions computed from conventional radiographs.

CONCLUSIONS

Before conventional radiographs are used for fractal analysis in the clinical environment, many of the technical problems associated with this methodology must be addressed.

Lysophosphatidylcholine increases vascular superoxide anion production via protein kinase C activation

We tested the hypothesis that lysophosphatidylcholine (lyso-PC) could activate protein kinase C in intact vascular segments and sought to examine some of the physiological consequences of this activation. In segments of rabbit aorta, the patterns of protein phosphorylation determined by two-dimensional electrophoresis stimulated by lyso-PC and 12-O-tetradecanoylphorbol 13-acetate (TPA) were similar. Activation of protein kinase C can stimulate superoxide anion (O2-) production in other tissues, and we found that lyso-PC-treated rabbit aortas produced twofold more O2- than control vessels. Calphostin C, a potent and specific inhibitor of protein kinase C, attenuated O2- production in lyso-PC-treated vessels but had no effect in control vessels. The effect of lyso-PC on O2- production was mimicked by TPA. In separate bioassay studies, release of the endothelium-derived vascular relaxing factor (EDRF) quantified by the response of detector vessels was markedly impaired after exposure of donor rabbit aortic segments to lyso-PC. After incubation with calphostin C, EDRF release in response to acetylcholine from lyso-PC-treated donor vessels was restored significantly. Thus, lyso-PC can activate protein kinase C in intact vessels, leading to an increase in O2- production. Activation of protein kinase C by lyso-PC may also play a role in altering the release of EDRF in response to acetylcholine. Increased O2- production in response to lyso-PC may have important consequences in the atherogenic process.

Human leukemia K562 cell mutant (K562/OA200) selected for resistance to okadaic acid (protein phosphatase inhibitor) lacks protein kinase C-epsilon, exhibits multidrug resistance phenotype, and expresses drug pump P-glycoprotein

A human leukemia K562 cell mutant (K562/OA200) selected for resistance to okadaic acid (OA), an inhibitor of protein phosphatases 1 and 2A (PP1/PP2A), has been established. In wild type cells, the cytotoxicity of OA was associated with mitotic arrest and concentration- and time-dependent DNA fragmentation, a hallmark of apoptosis. The mutant was 100-fold more resistant to OA in terms of effects on these parameters. Although the synthesis of several proteins was altered, enzyme assay and immunoblot analysis indicated that the levels of PP1 and PP2A were unchanged in the mutant. Protein kinase C (PKC) assays and immunoblot analysis of calcium-dependent (cPKC) and calcium-independent (nPKC) isoforms revealed that nPKC-epsilon was strikingly absent in the mutant, which otherwise expressed in comparable amounts all other isotypes (cPKC-alpha, cPKC-beta, and nPKC-zeta) also present in the wild type. Northern blot analysis confirmed an absence of PKC-epsilon mRNA in the mutant cells. The OA200 cells were cross-resistant not only to another PP1/PP2A inhibitor, calyculin A, but also to structurally unrelated anticancer drugs (such as vinblastine and taxol) and furthermore, overexpressed the verapamil-sensitive drug pump P-glycoprotein at both the protein and mRNA levels. The mutant, however, was not cross-resistant to several PKC inhibitors tested including cardiotoxin, mastoparan, staurosporine, and an alkylphospholipid. Cardiotoxin, at a subtoxic concentration, enhanced by 6-fold vinblastine cytotoxicity in OA200 cells. These findings indicate that the multidrug resistance phenotype can be induced by cytotoxic agents other than conventional anticancer drugs, show that the development of multidrug resistance is not necessarily associated with increased cPKC activity, and identify certain PKC inhibitors that have potential as resistance modulators.

The E1 sequence of bovine adenovirus type 3 and complementation of human adenovirus type 5 E1A function in bovine cells

The bovine adenovirus type 3 (BAV3) genome was sequenced from the left end to the HindIII site at 11%. This region comprises the entire E1 transcription unit including the open reading frames (ORF) for proteins homologous to the E1A, E1B proteins and protein IX of human adenovirus type 5 (Ad5). A portion of the BAV3 E1A protein showed significant homology with conserved region 3 (CR3), the principal transactivation region of Ad5 E1A. The BAV3 E1A protein also contains a consensus sequence known to be important for interaction with the cellular Rb protein but lacks most of the sequence corresponding to the second exon of Ad5 E1A. Promoter sequences for BAV3 E1B were not defined though the relevant region contains a 35-base pair repeat sequence. Two ORFs define the BAV3 E1B coding unit; one with regions homologous to sequences within the Ad5 E1B 19k protein, and an overlapping ORF with significant homology to the Ad5 E1B 55k protein. The encoded BAV3 E1B proteins of 157 and 420 amino acid residues (R) have predicted unmodified molecular weights of 17,393 and 46,734 respectively. Immediately following the E1B coding region there is a transcription unit containing an SP1 binding site and TATA box followed by an ORF which encodes a protein of 125R and predicted molecular weight of 13,706 with homology to protein IX of Ad5. Five concensus poly A addition sites are located in the 350 base pairs immediately following the protein IX coding region. The homology of sequences in the Ad5 E1A CR3 region and the corresponding BAV3 protein suggested that the BAV3 protein could transactivate certain Ad5 genes normally transactivated by the Ad5 E1A product. Evidence for this hypothesis was obtained in studies in which bovine cells in culture were coinfected with BAV3 and a human adenovirus type 5 (Ad5) recombinant viral vector lacking the E1A region and having a lacZ reporter gene within the E3 region dependent on E1A for its expression. Coinfection resulted in the induction of beta-galactosidase activity and the increased expression of other Ad5 early (E2A 72k) and late (hexon) proteins.

Feature information extraction from dynamic biospeckle

Dynamic biospeckle can be obtained from cultures of motile microorganisms by use of a hybrid opto-electronic system, and it carries feature information about the cultures. On the basis of theoretical analysis and experimental results we describe and discuss two techniques that process the signals derived from dynamic biospeckle. Experimental results on detection of space-time autocorrelation and analysis of histograms of subtraction between two speckle patterns are demonstrated. After extracting dynamic and statistical characteristics of the cultures of motile microorganisms, we show that with these techniques, real-time and insitu culture vitality monitoring and automatic culture identifications are possible.

Stage I clinical trial of gene therapy for hemophilia B

This paper describes the first human gene therapy trial for hemophilia B. Retroviruses were used to introduce human factor IX into autologous, primary human skin fibroblasts from the patients. Recombinant retroviral vector containing human FIX cDNA driven by viral LTR promoter (XL-IX) and double-copy retroviral vector driven by human cytomegalovirus enhancer-promoter (N2CMV-IX) were constructed. After the safety assessment, including soft-agar test, cell morphology observation, analysis of endotoxin, chromosome karyotype, allergic reaction test, nude mice test, routine pathological test, electromicroscopic analysis, and virus detection by PCR, etc., the engineered cells were pooled and embedded in collagen mixture, autologously injected into the patients respectively. The concentration of human FIX protein of Patient 1 increased from 71 ng/ml to 220 ng/ml, with a maximum level of 245 ng/ml. The expression of FIX has lasted for 6 months at the time of writing. The clotting activity also increased from 2.9% to 6.3%, his clinical symptoms have been alleviated obviously. The secretion rate of FIX for Patient 2 increased from 130 to 250 ng/ml, maintained at the level of 220 ng/ml for 5.5 months at the time of writing, but the clotting activity has not been increased steadily. There is no deleterious effect to be found in the two patients since the ex-vivo cells were implanted. The two patients are now under follow-up investigation. We suggested that retrovirus-mediated transfer of genes into skin fibroblasts, to be embedded in collagen and subcutaneously injected into patients, is a simple and effective approach for the gene therapy for hemophilia B.

[Effect of improving memory and inhibiting acetylcholinesterase activity by invigorating-qi and warming-yang recipe]

Invigorating-Qi and Warming-Yang (IQWY) had a good curative effect to some senile diseases such as senile dementia, senile hypomnesia etc. This experiment was designed for probing into the therapeutical mechanism of IQWY recipe. BALB/C pure bred mice were divided into five groups. Group I was taken per os of invigorating Qi (IQ), Group II warming Yang (WY), Group III IQWY drugs, Group IV was dysmnesia model, and Group V blank control group injected with normal saline only. All groups except Group V were injected scopolamine (5mg/kg) intraperitoneally to induce dysmnesia model after medication. IQ drug consisted of Codonopsis pilosula, Astragalus membranaceus, Poria cocos, and Glycyrrhiza uralensis, WY drug of Cynomorium songoricum, Epimedium brevicornum and Cuscuta chinensis, while IQWY recipe consisted of both IQ and WY drugs. The results showed that IQ, WY and IQWY had an evident antagonistic action to Scopolamine induced dysmnesia mice, and could improve their memory. The erroneous times of the animal's reaction in Group I, II and III were less than those in Group IV, P < 0.05 or P < 0.01. Acetylcholinesterase (AchE) activity in the mice could be inhibited by IQ, WY and IQWY also. The activity in Group I, II and III was less than that in Group IV and V, P < 0.05 or P < 0.01. The therapeutic mechanism of IQWY was in connection with its effect to M-cholinergic transmitters of central nervous system.

Immunogenicity in mice of tandem repeats of an epitope from herpes simplex gD protein when expressed by recombinant adenovirus vectors

The antigenic and immunogenic potential was examined of human adenovirus type 5 (Ad) recombinants carrying and expressing from one to four tandem repeats of a linear neutralizing epitope from the gD protein of herpes simplex virus type 1 (HSV-1) as a fusion with the beta-galactosidase protein. The fusion proteins produced by these Ad vectors in infected cell culture reacted with a herpes simplex virus (HSV) epitope-specific monoclonal antibody to a degree dependent on the number of epitope repeats in the protein. Mice immunized by intraperitoneal injection of the Ad vectors developed an anti-HSV immune response as measured by ELISA and by HSV-1 neutralization assays. The mean antibody titre induced by a single injection of the Ad vector increased with the number of epitope repeats expressed by the recombinant. Any animal that had developed a serum-neutralizing titre of at least 1:80 survived challenge with a normally lethal dose of HSV-2 administered by the intraperitoneal route. Recombinant vectors expressing four repeats of the HSV epitope were as effective in antibody induction and protection as an adenovirus vector carrying and expressing the entire HSV gD protein. These results suggest that the expression of tandem repeats of appropriate epitopic sequences by adenovirus vectors may provide a safe and effective method of immunizing against HSV infection.

Sites of B-cell activation in vivo

Novel techniques have made possible in situ analyses of the lymphocyte populations responding to antigen. In the spleen, antigen-specific T and B cells are first observed in the periarteriolar lymphoid sheath. Following conjugate formation between specific T and B lymphocytes, B-cell proliferation and differentiation takes place in two distinct sites, the periarteriolar lymphoid sheath-associated foci and germinal centers.