A dense ring of the trans-Neptunian object Quaoar outside its Roche limit

Planetary rings are observed not only around giant planets1, but also around small bodies such as the Centaur Chariklo2 and the dwarf planet Haumea3. Up to now, all known dense rings were located close enough to their parent bodies, being inside the Roche limit, where tidal forces prevent material with reasonable densities from aggregating into a satellite. Here we report observations of an inhomogeneous ring around the trans-Neptunian body (50000) Quaoar. This trans-Neptunian object has an estimated radius4 of 555 km and possesses a roughly 80-km satellite5 (Weywot) that orbits at 24 Quaoar radii6,7. The detected ring orbits at 7.4 radii from the central body, which is well outside Quaoar's classical Roche limit, thus indicating that this limit does not always determine where ring material can survive. Our local collisional simulations show that elastic collisions, based on laboratory experiments8, can maintain a ring far away from the body. Moreover, Quaoar's ring orbits close to the 1/3 spin-orbit resonance9 with Quaoar, a property shared by Chariklo's2,10,11 and Haumea's3 rings, suggesting that this resonance plays a key role in ring confinement for small bodies.

Semisynthetic Glycoconjugate Vaccine Candidates against Escherichia coli O25B Induce Functional IgG Antibodies in Mice

Extraintestinal pathogenic Escherichia coli (ExPEC) is a major health concern due to emerging antibiotic resistance. Along with O1A, O2, and O6A, E. coli O25B is a major serotype within the ExPEC group, which expresses a unique O-antigen. Clinical studies with a glycoconjugate vaccine of the above-mentioned O-types revealed O25B as the least immunogenic component, inducing relatively weak IgG titers. To evaluate the immunological properties of semisynthetic glycoconjugate vaccine candidates against E. coli O25B, we here report the chemical synthesis of an initial set of five O25B glycan antigens differing in length, from one to three repeat units, and frameshifts of the repeat unit. The oligosaccharide antigens were conjugated to the carrier protein CRM₁₉₇. The resulting semisynthetic glycoconjugates induced functional IgG antibodies in mice with opsonophagocytic activity against E. coli O25B. Three of the oligosaccharide-CRM₁₉₇ conjugates elicited functional IgGs in the same order of magnitude as a conventional CRM₁₉₇ glycoconjugate prepared with native O25B O-antigen and therefore represent promising vaccine candidates for further investigation. Binding studies with two monoclonal antibodies (mAbs) revealed nanomolar anti-O25B IgG responses with nanomolar K _D values and with varying binding epitopes. The immunogenicity and mAb binding data now allow for the rational design of additional synthetic antigens for future preclinical studies, with expected further improvements in the functional antibody responses. Moreover, acetylation of a rhamnose residue was shown to be likely dispensable for immunogenicity, as a deacylated antigen was able to elicit strong functional IgG responses. Our findings strongly support the feasibility of a semisynthetic glycoconjugate vaccine against E. coli O25B.

A semisynthetic glycoconjugate provides expanded cross-serotype protection against Streptococcus pneumoniae

Streptococcus pneumoniae (S. pneumoniae)infections are the leading cause of child mortality globally. Currentvaccines fail to induceaprotective immune response towards a conserved part of the pathogen,resulting in newserotypescausing disease. Therefore, new vaccinestrategies are urgently needed.Described is atwo-pronged approach combiningS. pneumoniaeproteins, pneumolysin (Ply) and pneumococcal surface protein A (PspA),with aprecisely defined synthetic oligosaccharide,wherebythe carrier protein actsas a serotype-independent antigen to provideadditional protection. Proof of concept in mice and swine modelsrevealed thatthe conjugatesinhibited colonization of the nasopharynx, decreased the bacterial load and reduced disease severity in the bacteria challenge model. Immunization of piglets provided the first evidence for the immunogenicity and protective potential of synthetic glycoconjugate vaccine in a large animal model.Acombination of synthetic oligosaccharides with proteins from the target pathogen opens the path to create broadly cross-protective ("universal") pneumococcal vaccines.

Sequential Linkage of Carbohydrate Antigens to Mimic Capsular Polysaccharides: Toward Semisynthetic Glycoconjugate Vaccine Candidates against Streptococcus pneumoniae Serotype 14

Vaccines based on isolated polysaccharides successfully protect humans from bacterial pathogens such as Streptococcus pneumoniae. Because polysaccharide production and isolation can be technically challenging, glycoconjugates containing synthetic antigens are an attractive alternative. Typically, the shortest possible oligosaccharide antigen is preferable as syntheses of longer structures are more difficult and time-consuming. Combining several protective epitopes or polysaccharide repeating units as blocks by bonds other than glycosidic linkages would greatly reduce the synthetic effort if the immunological response to the polysaccharide could be retained. To explore this concept, we bridged the well-understood and immunologically potent RU of S. pneumoniae serotype 14 (ST14) with an aliphatic spacer and conjugated it to the carrier protein CRM197. Mice immunized with the spacer-bridged glycan conjugates produced high levels of specific antibodies after just one or two vaccine doses, while the tetrasaccharide repeating unit alone required three doses. The antibodies recognized specifically ST14 CPS, while no significant antibody levels were raised against the spacer or unrelated CPS. Synthetic vaccines generated antibodies with opsonic activity. Mimicking polysaccharides by coupling repeating unit antigens via an aliphatic spacer may prove useful also for the development of other glycoconjugate vaccine candidates, thereby reducing the synthetic complexity while enhancing a faster immune response.

Synthesis of Streptococcus pneumoniae serotype 9V oligosaccharide antigens

Streptococcus pneumoniae (SP) bacteria cause serious invasive diseases. SP bacteria are covered by a capsular polysaccharide (CPS) that is a virulence factor and the basis for SP polysaccharide and glycoconjugate vaccines. The serotype 9V is part of the currently marketed conjugate vaccine and contains an acetate modification. To better understand the importance of glycan modifications in general and acetylation in particular, defined oligosaccharide antigens are needed for serological and immunological studies. Here, we demonstrate a convergent [2 + 3] synthetic strategy to prepare the pentasaccharide repeating unit of 9V with and without an acetate group at the C-6 position of mannosamine.

Chimeric oligosaccharide conjugate induces opsonic antibodies against Streptococcus pneumoniae serotypes 19A and 19F

Streptococcus pneumoniae 19A (ST19A) and 19F (ST19F) are among the prevalent serotypes causing pneumococcal disease worldwide even after introduction of a 13-valent pneumococcal conjugate vaccine (PCV13). Synthetic glycoconjugate vaccines have defined chemical structures rather than isolated polysaccharide mixtures utilized in marketed vaccines. Ideally, a minimal number of synthetic antigens would cover as many bacterial serotypes to lower cost of goods and minimize the response to carrier proteins. To demonstrate that a chimeric oligosaccharide antigen can induce a protective immune response against multiple serotypes, we synthesized a chimeric antigen (ST19AF) that is comprised of a repeating unit of ST19A and ST19F capsular polysaccharide each. Synthetic glycan epitopes representing only ST19A, and ST19F were prepared for comparison. Semisynthetic glycoconjugates containing chimeric antigen ST19AF induced high antibody titers able to recognize native CPS from ST19A and ST19F in rabbits. The antibodies were able to kill both strains of pneumococci. Chimeric antigens are an attractive means to induce an immune response against multiple bacterial serotypes.

Chimeric antigens are an attractive means to induce an immune response against multiple bacterial serotypes. The chimeric semisynthetic glycoconjugate ST19AF induced antibodies with opsonic activity able to kill ST19A and ST19F bacteria in rabbits.

Thermodynamic and Structural Behavior of α-Galactosylceramide and C6-Functionalized α-GalCer in 2D Layers at the Air-Liquid Interface

α-Galactosylceramide (α-GalCer; KRN7000) is a ligand for the glycoprotein CD1d that presents lipid antigens to natural killer T cells. Therefore, KRN7000 as well as some modified versions thereof have been widely investigated as part of novel immunotherapies. To examine the impact of structural modification, we investigated KRN7000 and C6-modified KRN7000 at the air-liquid interface using monolayer isotherms, BAM, IRRAS, GIXD, and TRXF. The amino group has no influence on the highly ordered sub-gel structures found at lateral pressures relevant for biological membranes. Neither lateral compression nor the protonation state of the amino group has a measurable effect on the lattice structure, which is defined by strong and rigid intermolecular hydrogen bonds. However, the first-order phase transition found for the C6-functionalized α-GalCer is connected with an extraordinary surface-inhibited nucleation. Our study demonstrates that KRN7000 can be functionalized at C6 without significantly changing the structural properties.

Synthesis, Liposomal Formulation, and Immunological Evaluation of a Minimalistic Carbohydrate-α-GalCer Vaccine Candidate

Fully synthetic glycan-based vaccines hold great potential as preventive and therapeutic vaccines against infectious diseases as well as cancer. Here, we present a two-component platform based on the facile conjugation of carbohydrate antigens to α-galactosylceramide (α-GalCer) to yield fully synthetic vaccine candidates. Formulation of the cancer-associated Tn antigen glycolipid model vaccine candidate into liposomes of different sizes and subsequent immunization of mice generated specific, high-affinity antibodies against the carbohydrate antigen with characteristics of T cell-dependent immunity. Liposome formulation elicited more reproducible glycan immunity than a conventional glycoconjugate vaccine bearing the same glycan antigen did. Further evaluation of the immune response revealed that the size of the liposomes influenced the glycan antibody responses toward either a cellular (Th1) or a humoral (Th2) immune phenotype. The glycolipid vaccine platform affords strong and robust antiglycan antibody responses in vivo without the need for an external adjuvant.

Development of an Efficacious, Semisynthetic Glycoconjugate Vaccine Candidate against Streptococcus pneumoniae Serotype 1

Infections with Streptococcus pneumoniae are a major health burden. Glycoconjugate vaccines based on capsular polysaccharides (CPSs) successfully protect from infection, but not all pneumococcal serotypes are covered with equal potency. Marketed glycoconjugate vaccines induce low levels of functional antibodies against the highly invasive serotype 1 (ST1), presumably due to the obscuring of protective epitopes during chemical activation and conjugation to carrier proteins. Synthetic oligosaccharide antigens can be designed to carry linkers for site-selective protein conjugation while keeping protective epitopes intact. Here, we developed an efficacious semisynthetic ST1 glycoconjugate vaccine candidate. A panel of synthetic oligosaccharides served to reveal a critical role of the rare aminosugar, 2-acetamido-4-amino-2,4,6-trideoxy-d-galactose (d-AAT), for ST1 immune recognition. A monovalent ST1 trisaccharide carrying d-AAT at the nonreducing end induced a strong antibacterial immune response in rabbits and outperformed the ST1 component of the multivalent blockbuster vaccine Prevenar 13, paving the way for a more efficacious vaccine.

Identification of the Minimal Glycotope of Streptococcus pneumoniae 7F Capsular Polysaccharide using Synthetic Oligosaccharides

Streptococcus pneumoniae causes life-threatening diseases including meningitis, pneumonia and sepsis. Existing glycoconjugate vaccines based on purified capsular polysaccharides are widely used and help to prevent millions of deaths every year. Herein, the total syntheses of oligosaccharides resembling portions of the S. pneumoniae serotype 7F (ST7F) capsular polysaccharide repeating unit are reported. To define minimal glycan epitopes, glycan microarrays containing the synthetic oligosaccharides were used to screen human reference serum and revealed that both side chains of the ST7F play a key role in antigen recognition. The identification of protective minimal epitopes is vital to design efficient semi- and fully-synthetic glycoconjugate vaccines.

Total Synthesis of a Densely Functionalized Plesiomonas shigelloides Serotype 51 Aminoglycoside Trisaccharide Antigen

Plesiomonas shigelloides, a pathogen responsible for frequent outbreaks of severe travelers' diarrhea, causes grave extraintestinal infections. Sepsis and meningitis due to P. shigelloides are associated with a high mortality rate as antibiotic resistance increases and vaccines are not available. Carbohydrate antigens expressed by pathogens are often structurally unique and are targets for developing vaccines and diagnostics. Here, we report a total synthesis of the highly functionalized trisaccharide repeating unit 2 from P. shigelloides serotype 51 from three monosaccharides. A judicious choice of building blocks and reaction conditions allowed for the four amino groups adorning the sugar rings to be installed with two N-acetyl (Ac) groups, rare acetamidino (Am), and d-3-hydroxybutyryl (Hb) groups. The strategy for the differentiation of amino groups in trisaccharide 2 will serve well for the syntheses of other complex glycans.

A semisynthetic Streptococcus pneumoniae serotype 8 glycoconjugate vaccine

Glycoconjugate vaccines based on capsular polysaccharides (CPSs) of pathogenic bacteria such as Streptococcus pneumoniae successfully protect from disease but suffer from incomplete coverage, are troublesome to manufacture from isolated CPSs, and lack efficacy against certain serotypes. Defined, synthetic oligosaccharides are an attractive alternative to isolated CPSs but require the identification of immunogenic and protective oligosaccharide antigens. We describe a medicinal chemistry strategy based on a combination of automated glycan assembly (AGA), glycan microarray-based monoclonal antibody (mAb) reverse engineering, and immunological evaluation in vivo to uncover a protective glycan epitope (glycotope) for S. pneumoniae serotype 8 (ST8). All four tetrasaccharide frameshifts of ST8 CPS were prepared by AGA and used in glycan microarray experiments to identify the glycotopes recognized by antibodies against ST8. One tetrasaccharide frameshift that was preferentially recognized by a protective, CPS-directed mAb was conjugated to the carrier protein CRM197. Immunization of mice with this semisynthetic glycoconjugate followed by generation and characterization of a protective mAb identified protective and nonprotective glycotopes. Immunization of rabbits with semisynthetic ST8 glycoconjugates containing protective glycotopes induced an antibacterial immune response. Coformulation of ST8 glycoconjugates with the marketed 13-valent glycoconjugate vaccine Prevnar 13 yielded a potent 14-valent S. pneumoniae vaccine. Our strategy presents a facile approach to develop efficient semisynthetic glycoconjugate vaccines.

A modular synthetic route to size-defined immunogenic Haemophilus influenzae b antigens is key to the identification of an octasaccharide lead vaccine candidate

A Haemophilus influenzae b vaccine lead antigen was identified by the immunological evaluation of chemically precisely defined capsular polysaccharide repeating unit oligosaccharides.

The first glycoconjugate vaccine using isolated glycans was licensed to protect children from Haemophilus influenzae serotype b (Hib) infections. Subsequently, the first semisynthetic glycoconjugate vaccine using a mixture of antigens derived by polymerization targeted the same pathogen. Still, a detailed understanding concerning the correlation between oligosaccharide chain length and the immune response towards the polyribosyl-ribitol-phosphate (PRP) capsular polysaccharide that surrounds Hib remains elusive. The design of semisynthetic and synthetic Hib vaccines critically depends on the identification of the minimally protective epitope. Here, we demonstrate that an octasaccharide antigen containing four repeating disaccharide units resembles PRP polysaccharide in terms of immunogenicity and recognition by anti-Hib antibodies. Key to this discovery was the development of a modular synthesis that enabled access to oligosaccharides up to decamers. Glycan arrays containing the synthetic oligosaccharides were used to analyze anti-PRP sera for antibodies. Conjugates of the synthetic antigens and the carrier protein CRM197, which is used in licensed vaccines, were employed in immunization studies in rabbits.

A Semi-Synthetic Glycoconjugate Vaccine Candidate for Carbapenem-Resistant Klebsiella pneumoniae

Hospital-acquired infections are an increasingly serious health concern. Infections caused by carpabenem-resistant Klebsiella pneumoniae (CR-Kp) are especially problematic, with a 50 % average survival rate. CR-Kp are isolated from patients with ever greater frequency, 7 % within the EU but 62 % in Greece. At a time when antibiotics are becoming less effective, no vaccines to protect from this severe bacterial infection exist. Herein, we describe the convergent [3+3] synthesis of the hexasaccharide repeating unit from its capsular polysaccharide and related sequences. Immunization with the synthetic hexasaccharide 1 glycoconjugate resulted in high titers of cross-reactive antibodies against CR-Kp CPS in mice and rabbits. Whole-cell ELISA was used to establish the surface staining of CR-Kp strains. The antibodies raised were found to promote phagocytosis. Thus, this semi-synthetic glycoconjugate is a lead for the development of a vaccine against a rapidly progressing, deadly bacterium.

A Streptococcus pneumoniae Type 2 Oligosaccharide Glycoconjugate Elicits Opsonic Antibodies and Is Protective in an Animal Model of Invasive Pneumococcal Disease

Invasive pneumococcal diseases (IPDs) remain the leading cause of vaccine-preventable childhood death, even though highly effective pneumococcal conjugate vaccines (PCVs) are used in national immunization programs in many developing countries. Licensed PCVs currently cover only 13 of the over 90 serotypes of Streptococcus pneumoniae (Sp), so nonvaccine serotypes are a major obstacle to the effective control of IPD. Sp serotype 2 (ST2) is such a nonvaccine serotype that is the main cause of IPD in many countries, including Nepal, Bangladesh, and Guatemala. Glycoconjugate vaccines based on synthetic oligosaccharides instead of isolated polysaccharides offer an attractive alternative to the traditional process for PCV development. To prevent the IPDs caused by ST2, we identified an effective ST2 neoglycoconjugate vaccine candidate that was identified using a medicinal chemistry approach. Glycan microarrays containing a series of synthetic glycans resembling portions of the ST2 capsular polysaccharide (CPS) repeating unit were used to screen human and rabbit sera and identify epitope hits. Synthetic hexasaccharide 2, resembling one repeating unit (RU) of ST2 CPS, emerged as a hit from the glycan array screens. Vaccination with neoglycoconjugates consisting of hexasaccharide 2 coupled to carrier protein CRM197 stimulates a T-cell-dependent B-cell response that induced CPS-specific opsonic antibodies in mice, resulting in killing of encapsulated bacteria by phagocytic activity. Subcutaneous immunization with neoglycoconjugate protected mice from transnasal challenge with the highly virulent ST2 strain NCTC 7466 by reducing the bacterial load in lung tissue and blood.

1,3-Dibromo-5,5-dimethylhydantoin as promoter for glycosylations using thioglycosides

1,3-Dibromo-5,5-dimethylhydantoin (DBDMH), an inexpensive, non-toxic and stable reagent, is a competent activator of thioglycosides for glycosidic bond formation. Excellent yields were obtained when triflic acid (TfOH) or trimethylsilyl trifluoromethanesulfonate (TMSOTf) were employed as co-promoters in solution or automated glycan assembly on solid phase.

Total synthesis of a Streptococcus pneumoniae serotype 12F CPS repeating unit hexasaccharide

The Gram-positive bacterium Streptococcus pneumoniae causes severe disease globally. Vaccines that prevent S. pneumoniae infections induce antibodies against epitopes within the bacterial capsular polysaccharide (CPS). A better immunological understanding of the epitopes that protect from bacterial infection requires defined oligosaccharides obtained by total synthesis. The key to the synthesis of the S. pneumoniae serotype 12F CPS hexasaccharide repeating unit that is not contained in currently used glycoconjugate vaccines is the assembly of the trisaccharide β-D-GalpNAc-(1→4)-[α-D-Glcp-(1→3)]-β-D-ManpNAcA, in which the branching points are equipped with orthogonal protecting groups. A linear approach relying on the sequential assembly of monosaccharide building blocks proved superior to a convergent [3 + 3] strategy that was not successful due to steric constraints. The synthetic hexasaccharide is the starting point for further immunological investigations.

Synthetic Lipoteichoic Acid Glycans Are Potential Vaccine Candidates to Protect from Clostridium difficile Infections

Infections with Clostridium difficile increasingly cause morbidity and mortality worldwide. Bacterial surface glycans including lipoteichoic acid (LTA) were identified as auspicious vaccine antigens to prevent colonization. Here, we report on the potential of synthetic LTA glycans as vaccine candidates. We identified LTA-specific antibodies in the blood of C. difficile patients. Therefore, we evaluated the immunogenicity of a semi-synthetic LTA-CRM₁₉₇ glycoconjugate. The conjugate elicited LTA-specific antibodies in mice that recognized natural LTA epitopes on the surface of C. difficile bacteria and inhibited intestinal colonization of C. difficile in mice in vivo. Our findings underscore the promise of synthetic LTA glycans as C. difficile vaccine candidates.

Automated glycan assembly of a S. pneumoniae serotype 3 CPS antigen

Vaccines against S. pneumoniae, one of the most prevalent bacterial infections causing severe disease, rely on isolated capsular polysaccharide (CPS) that are conjugated to proteins. Such isolates contain a heterogeneous oligosaccharide mixture of different chain lengths and frame shifts. Access to defined synthetic S. pneumoniae CPS structures is desirable. Known syntheses of S. pneumoniae serotype 3 CPS rely on a time-consuming and low-yielding late-stage oxidation step, or use disaccharide building blocks which limits variability. Herein, we report the first iterative automated glycan assembly (AGA) of a conjugation-ready S. pneumoniae serotype 3 CPS trisaccharide. This oligosaccharide was assembled using a novel glucuronic acid building block to circumvent the need for a late-stage oxidation. The introduction of a washing step with the activator prior to each glycosylation cycle greatly increased the yields by neutralizing any residual base from deprotection steps in the synthetic cycle. This process improvement is applicable to AGA of many other oligosaccharides.

Deciphering Antigenic Determinants of Streptococcus pneumoniae Serotype 4 Capsular Polysaccharide using Synthetic Oligosaccharides

Streptococcus pneumoniae is a major cause of mortality and morbidity worldwide. More than 90 S. pneumoniae serotypes are distinguished based on the structure of their primary targets to the human immune system, the capsular polysaccharides (CPSs). The CPS of the prevalent serotype 4 (ST4) is composed of tetrasaccharide repeating units and is included in existing pneumococcal vaccines. Still, the structural antigenic determinants that are essential for protective immunity, including the role of the rare and labile cyclic trans-(2,3) pyruvate ketal modification, remain largely unknown. Molecular insights will support the design of synthetic subunit oligosaccharide vaccines. Here, we identified the key antigenic determinants of ST4 CPS with the help of pyruvated and nonpyruvated synthetic repeating unit glycans. Glycan arrays revealed oligosaccharide antigens recognized by antibodies in the human reference serum. Selected depyruvated ST4 oligosaccharides were used to formulate neoglycoconjugates and immunologically evaluated in mice. These oligosaccharides were highly immunogenic, but the resulting antiglycan antibodies showed only limited binding to the natural CPS present on the bacterial surface. Glycan array and surface plasmon resonance analysis of murine polyclonal serum antibodies as well as monoclonal antibodies revealed that terminal sugars are important in directing the immune responses. The pyruvate modification on the oligosaccharide is needed for cross-reactivity with the native CPS. These findings are an important step toward the design of oligosaccharide-based vaccines against S. pneumoniae ST4.

The rainy season increases the abundance and richness of the aquatic insect community in a Neotropical reservoir

Alterations in aquatic systems and changes in water levels, whether due to rains or dam-mediated control can cause changes in community structure, forcing the community to readjust to the new environment. This study tested the hypothesis that there is an increase in the richness and abundance of aquatic insects during the rainy season in the Serra da Mesa Reservoir, with the premise that increasing the reservoir level provides greater external material input and habitat diversity, and, therefore, conditions that promote colonization by more species. We used the paired t test to test the differences in richness, beta diversity, and abundance, and a Non-metric Multidimensional Scaling (NMDS) was performed to identify patterns in the community under study. Additionally, Pearson correlations were analyzed between the richness, abundance, and beta diversity and the level of the reservoir. We collected 35,028 aquatic insect larvae (9,513 in dry period and 25,515 in the rainy season), predominantly of the Chironomidae family, followed by orders Ephemeroptera, Trichoptera, and Odonata. Among the 33 families collected, only 12 occurred in the dry season, while all occurred in the rainy season. These families are common in lentic environments, and the dominance of Chironomidae was associated with its fast colonization, their behavior of living at high densities and the great tolerance to low levels of oxygen in the environment. The hypothesis was confirmed, as the richness, beta diversity, and abundance were positively affected by the increase in water levels due to the rainy season, which most likely led to greater external material input, greater heterogeneity of habitat, and better conditions for colonization by several families.

Flexural strength of composites: influences of polyethylene fiber reinforcement and type of composite

MAIN PROBLEM

The microfill veneering of hybrid composite restorations has been indicated to improve esthetics. Also, polyethylene fiber reinforcement has been proposed for use in composite restorations in high-stress clinical situations. However, minimal information in the literature addresses the influence of such combinations on the resistance to fracture. The purpose of this study was to investigate the flexural strength of two composites, a microfill and a hybrid, the effect of their combination, and the influence of polyethylene fiber reinforcement.

MATERIALS AND METHODS

Twenty-eight specimens were prepared using a standard metallic mold (20x2x2 mm) and divided into groups of seven each: Filtek Z-250 (3M ESPE, St. Paul, Minn., USA) (group I), Filtek A-110 (3M ESPE) (group II), Filtek Z-250 combined with Filtek A-110 (group III), and Filtek Z-250 combined with polyethylene fiber (Ribbond, Seattle, Wash., USA) (group IV). The specimens were stress-loaded to fracture in a three-point bending device according to International Standardization Organization (ISO) 4049.

RESULTS

Data were analyzed using analysis of variance and Tukey's test at a 0.05 level of significance. No statistically significant differences were observed between groups I and IV. Group II, however, exhibited statistically lower resistance to fracture than the other groups. Group III presented intermediate results, showing statistically higher fracture resistance than group II but lower than group I.

CONCLUSIONS

With the methodology employed, microfill composite presented the lowest flexural strength, but its association with hybrid composite increased the resistance to fracture. The combination of polyethylene fiber and hybrid composite did not present higher flexural strength than hybrid composite alone.

[Monitoring AIDS patients for the development of cytomegalovirus (CMV) disease using multiplex PCR]

The human cytomegalovirus is an important pathogen in patients infected with the human immunodeficiency virus (HIV). The CMV viral load seems to be predictor of the development of the CMV disease in these patients. We used a multiplex PCR protocol that also provides quantitative information in those samples from which a single band is amplified and contains fewer viral genomes than those from which both targets are amplified. Monthly blood samples were collected from 270 AIDS patients. From twenty patients, two CMV targets were amplified three or more consecutive times and these patients developed CMV related disease during the study. In contrast, patients who did not result positive for both viral targets, for three or more consecutive times, or who had alternating positive and negative samples during the follow up did not present CMV related disease. The results suggest that the PCR multiplex can be used for the identification of HIV positive patients with higher risk of development of CMV disease.

Blood stained cerebrospinal fluid responsible for false positive reactions of latex particle agglutination tests

The accuracy of the latex particle agglutination test (LPAT) was assessed in blood stained cerebrospinal fluid (CSF) specimens from 166 paediatric patients, aged from three months to 13 years. A commercial LPAT kit was used to detect Haemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis A, B, and C soluble antigens. Culture of CSF specimens was used as the standard and all laboratory procedures were performed blind. The mean CSF erythrocyte count was 66,406 cells/mm3 in the cases and 11,560 cells/mm3 in the controls. The sensitivity and the specificity of LPAT were 83.8 and 94.0%, respectively, suggesting that LPAT is a useful diagnostic tool even in blood stained CSF specimens.