Genetic basis for variation in plasma IL-18 levels in persons with chronic hepatitis C virus and human immunodeficiency virus-1 infections

Inflammasomes are multi-protein complexes integrating pathogen-triggered signaling leading to the generation of pro-inflammatory cytokines, including interleukin-18 (IL-18). Hepatitis C virus (HCV) and human immunodeficiency virus-1 (HIV) infections are associated with elevated IL-18, suggesting inflammasome activation. However, there is marked person-to-person variation in the inflammasome response to HCV and HIV. We hypothesized that host genetics may explain this variation. To test this, we analyzed the associations of plasma IL-18 levels and polymorphisms in 10 genes in the inflammasome cascade. 1538 participants with active HIV and/or HCV infection in 3 ancestry groups are included. Samples were genotyped using the Illumina Omni 1-quad and Omni 2.5 arrays. Linear regression analyses were performed to test the association of variants with logIL-18 including HCV and HIV infection status and HIV-RNA, in each ancestry group and then meta-analyzed. Eleven highly correlated SNPs (r2=0.98-1) in the IL18-BCO2 region were significantly associated with logIL-18; Each T allele of rs80011693 confers a decrease of 0.06 log pg/mL of IL-18 after adjusting for covariates (rs80011693; rs111311302 β=-0.06, P-value=2.7×10^-4). In conclusion, genetic variation in IL18 is associated with IL-18 production in response to HIV and HCV infection and may explain variability in the inflammatory outcomes of chronic viral infections.

Antiviral activities in human saliva

In this review, the authors survey the large number of antibacterial and antiviral proteins present in human saliva. Of interest, most of these antibacterial proteins display antiviral activity, typically against specific viral pathogens. The review focuses on one protein that interacts with both bacteria and viruses-gp340, originally referred to as salivary agglutinin. In the oral cavity, soluble gp340 binds to and aggregates a variety of bacteria, and this is thought to increase bacterial clearance from the mouth. However, when bound to the tooth surface, gp340 promotes bacterial adherence. In the oral cavity, most gp340 is found soluble in saliva and can function as a specific inhibitor of infectivity of HIV-1 and influenza A. In contrast, in the female reproductive track, most gp340 is bound to the cell surface, where it can promote HIV-1 infection.

Anatomic site variability in rat skeletal uptake and desorption of fluorescently labeled bisphosphonate

OBJECTIVES

Bisphosphonates commonly used to treat osteoporosis, Paget's disease, multiple myeloma, hypercalcemia of malignancy and osteolytic lesions of cancer metastasis have been associated with bisphosphonate-associated jaw osteonecrosis (BJON). The underlying pathogenesis of BJON is unclear, but disproportionate bisphosphonate concentration in the jaw has been proposed as one potential etiological factor. This study tested the hypothesis that skeletal biodistribution of intravenous bisphosphonate is anatomic site-dependent in a rat model system.

MATERIALS AND METHODS

Fluorescently labeled pamidronate was injected intravenously in athymic rats of equal weights followed by in vivo whole body fluorimetry, ex vivo optical imaging of oral, axial, and appendicular bones and ethylenediaminetetraacetic acid bone decalcification to assess hydroxyapatite-bound bisphosphonate.

RESULTS

Bisphosphonate uptake and bisphosphonate released per unit calcium were similar in oral and appendicular bones but lower than those in axial bones. Hydroxyapatite-bound bisphosphonate liberated by sequential acid decalcification was the highest in oral, relative to axial and appendicular bones (P < 0.05).

CONCLUSIONS

This study demonstrates regional differences in uptake and release of bisphosphonate from oral, axial, and appendicular bones of immune deficient rats.

The synaptic activity of HsDmc1, a human recombination protein specific to meiosis

Human Dmc1 protein, a meiosis-specific homolog of Escherichia coli RecA protein, has previously been shown to promote DNA homologous pairing and strand-exchange reactions that are qualitatively similar to those of RecA protein and Rad51. Human and yeast Rad51 proteins each form a nucleoprotein filament that is very similar to the filament formed by RecA protein. However, recent studies failed to find a similar filament made by Dmc1 but showed instead that this protein forms octameric rings and stacks of rings. These observations stimulated further efforts to elucidate the mechanism by which Dmc1 promotes the recognition of homology. Dmc1, purified to a state in which nuclease and helicase activities were undetectable, promoted homologous pairing and strand exchange as measured by fluorescence resonance energy transfer (FRET). Observations on the intermediates and products, which can be distinguished by FRET assays, provided direct evidence of a three-stranded synaptic intermediate. The effects of helix stability and mismatched base pairs on the recognition of homology revealed further that human Dmc1, like human Rad51, requires the preferential breathing of A small middle dotT base pairs for recognition of homology. We conclude that Dmc1, like human Rad51 and E. coli RecA protein, promotes homologous pairing and strand exchange by a "synaptic pathway" involving a three-stranded nucleoprotein intermediate, rather than by a "helicase pathway" involving the separation and reannealing of DNA strands.

Chlorambucil induction of HsRad51 in B-cell chronic lymphocytic leukemia

Our previous studies with B-cell chronic lymphocytic leukemia (B-CLL) have suggested that one of the mechanisms of nitrogen mustard (NM) drug resistance is increased repair of drug-induced damage. We have postulated that recombination may play a crucial role in this process. The human homologue of Rad51, (HsRad51), has homology to the RecA protein in Escherichia coli, which is implicated in recombination repair and induction of DNA repair enzymes. In this report, we have examined the expression and distribution of HsRad51 protein in lymphocytes from patients with B-CLL to see whether the expression of HsRad51 is associated with NM damage to the malignant B lymphocytes, specifically chlorambucil (CLB), which is the standard alkylating agent used to treat patients with B-CLL. We have analyzed the intracellular distribution of HsRad51 protein in these lymphocytes before and after treatment with CLB by immunofluorescence. In vitro CLB treatment induces Rad51 expression, as measured by increased immunopositive staining in all CLL samples. In the CLB-resistant CLL lymphocytes, there was a linear correlation between induction of Rad51 protein at 5.4 microM CLB and the in vitro LD50 dose of CLB. Surprisingly, although it has been reported that Rad51 is induced in S phase and only 10% of cells from cell lines expressed positive immunostaining for Rad51, our CLL lymphocytes, which were not subjected to in vitro drug exposure, were 90% positive for Rad51, despite their nonproliferative state, which suggests that there is chronic activation of the protein. Our results suggest that CLB activates HsRad51-directed recombination repair and that this process may be important in NM drug-induced cytotoxicity.

Alendronate inhibition of protein-tyrosine-phosphatase-meg1

Alendronate (4-amino-1-hydroxybutylidene-1,1-bisphosphonate) is a potent bisphosphonate that inhibits osteoclastic bone resorption and has proven effective for the treatment of osteoporosis. Its molecular mechanism of action, however, has not been defined precisely. Here we report that alendronate is a potent inhibitor of the protein-tyrosine-phosphatase-meg1 (PTPmeg1). Two substrates were employed in this study: fluorescein diphosphate and the phosphotyrosyl peptide src-pY527. With either substrate, alendronate was a slow binding inhibitor of PTPmeg1. Among the other bisphosphonates studied, alendronate was more potent and selective for PTPmeg1. The hydrolysis of fluorescein diphosphate by PTP epsilon and PTPmeg1 was sensitive to alendronate, with IC50 values of less than 1 microM; PTPsigma, however, under the same conditions, was inhibited by only 50% with 141 microM alendronate. Similarly, with the src-pY527 substrate, alendronate inhibition was also PTP dependent. Alendronate inhibited PTPmeg1 with an IC50 value of 23 microM, PTPsigma with an IC50 value of 2 microM, and did not inhibit PTP epsilon at concentrations up to 1 mM. The alendronate inhibition of these three PTPs and two substrates is consistent with the formation of a ternary complex comprised of enzyme, substrate, and inhibitor. PTP inhibition by hisphosphonates or vanadate was diminished by the metal chelating agent EDTA, or by the reducing agent dithiothreitol, suggesting that a metal ion and the oxidation of a cysteine residue are required for full inhibition. These observations show substrate- and enzyme-specific PTP inhibition by alendronate and support the possibility that a certain PTP(s) may be the molecular target for alendronate action.

Identification and analysis of fipA, a Fusobacterium nucleatum immunosuppressive factor gene

We have previously demonstrated that sonic extracts of Fusobacterium nucleatum FDC 364 were capable of inhibiting human T-cell responses to mitogens and antigens. The purified F. nucleatum immunosuppressive protein (FIP) is composed of two subunits of 44 and 48 kDa. Furthermore, FIP inhibits T-cell activation by arresting cells in the middle of the G(1) phase of the cell cycle; the data available to date suggest that FIP impairs the expression of the proliferating-cell nuclear antigen. To initiate delineation of FIP structure-function relationships, molecular cloning of the FIP gene was carried out. A DNA library of F. nucleatum FDC 364 was constructed by partial digestion of genomic DNA with Sau3A and screened for the production of FIP with polyclonal antibody. Twelve immunoreactive clones were identified. One of these clones contained a 3.1-kbp insert and was chosen for further study. Cell lysates were found to contain an immunoreactive band that comigrated with the 44-kDa subcomponent of the native FIP. Sequencing of the 3.1-kpb insert revealed the presence of three open reading frames (ORFs). One ORF extends from nucleotides 415 to 1620, encodes 402 amino acids, and is preceded by a ribosome-binding site. Deletion analysis and antibody elution analysis showed that this ORF encodes the 44-kDa subunit (FipA) of native FIP. A second ORF is situated upstream of fipA. However, Northern (RNA) analysis suggested that fipA is not transcribed as part of an operon but transcribed from its own promotor. Finally, the partially purified recombinant FipA protein was capable of impairing T-cell activation in a manner consistent with the native protein. These results indicate that the two components that form the native protein are most probably distinct gene products and suggest that the 44-kDa FipA polypeptide is sufficient to mediate the immunosuppressive activities of the native protein complex.

Calcium-binding properties of SSP-5, the Streptococcus gordonii M5 receptor for salivary agglutinin

Streptococcus gordonii M5 expresses a lectin on its surface (SSP-5) which binds to human salivary agglutinin (SAG). This interaction requires sialic acid residues of SAG and divalent cations and may mediate the colonization of oral tissues by this organism. In this report, we show that the binding of SAG to SSP-5 requires calcium and that SSP-5 is a high-affinity calcium-binding protein. SAG-mediated aggregation of S. gordonii M5 was inhibited by 1 mM EDTA, and the restoration of aggregation occurred only upon the readdition of calcium. To ascertain the level at which calcium exerts its effects, the calcium-binding properties of SSP-5 were evaluated by using a 45Ca binding assay. In addition, a kinetic analysis of calcium binding was carried out by using fura2, a fluorescent calcium-binding dye. These analyses showed that SSP-5 is a high-affinity calcium-binding protein that binds 1 mol of calcium per mol of protein and has a dissociation constant of 0.45 +/- 0.2 microM. The calcium-binding capacity of SSP-5 was also calculated independently to be 1.0 +/- 0.2 mol of Ca per mol of SSP-5 by column chromatography on Sephadex G-25 equilibrated with 10 microM 45Ca. To localize the calcium binding site of SSP-5, a series of C-terminal deletion mutants were expressed in Escherichia coli and evaluated for calcium-binding activity. Deletion of the 250 C-terminal residues of SSP-5 had little effect on calcium binding. However, deletion of residues 1168 to 1250 resulted in the loss of calcium-binding activity, suggesting that this region is important for calcium binding by SSP-5.

Flow cytometric analysis of the cytotoxic effects of Actinobacillus actinomycetemcomitans leukotoxin on human natural killer cells

The goal of this investigation was to determine if human natural killer (NK) cells were susceptible to the cytolytic effects of the Actinobacillus actinomycetemcomitans leukotoxin (LTX). Following treatment with LTX (0-200 ng/ml), NK cell activation by interleukin-2 (IL-2) was evaluated. LTX inhibited the IL-2-induced expression of both CD69 and the IL-2 receptor. Furthermore, the up-regulation of CD56 was also impaired. To determine whether the observed functional deficits were the result of cell death, NK cell viability was evaluated by flow cytometry. Changes in forward and side light scatter patterns consistent with cell death were observed within 60 min. Direct analysis of cell viability by measuring propidium iodide exclusion, however, indicated little change in the viability of LTX-treated NK cells. Electron microscopic analysis of NK cells exposed to LTX revealed early nuclear alterations characterized by hyperchromaticity, nuclear fragmentation, and condensation of nucleoplasm. However, no change in membrane integrity was initially noted. Finally, LTX caused a rapid and sustained elevation in the intracellular levels of Ca2+. These morphological and biochemical changes are consistent with the notion of programmed cell death.

Bisphosphonate action. Alendronate localization in rat bone and effects on osteoclast ultrastructure

Studies of the mode of action of the bisphosphonate alendronate showed that 1 d after the injection of 0.4 mg/kg [3H]alendronate to newborn rats, 72% of the osteoclastic surface, 2% of the bone forming, and 13% of all other surfaces were densely labeled. Silver grains were seen above the osteoclasts and no other cells. 6 d later the label was 600-1,000 microns away from the epiphyseal plate and buried inside the bone, indicating normal growth and matrix deposition on top of alendronate-containing bone. Osteoclasts from adult animals, infused with parathyroid hormone-related peptide (1-34) and treated with 0.4 mg/kg alendronate subcutaneously for 2 d, all lacked ruffled border but not clear zone. In vitro alendronate bound to bone particles with a Kd of approximately 1 mM and a capacity of 100 nmol/mg at pH 7. At pH 3.5 binding was reduced by 50%. Alendronate inhibited bone resorption by isolated chicken or rat osteoclasts when the amount on the bone surface was around 1.3 x 10(-3) fmol/microns 2, which would produce a concentration of 0.1-1 mM in the resorption space if 50% were released. At these concentrations membrane leakiness to calcium was observed. These findings suggest that alendronate binds to resorption surfaces, is locally released during acidification, the rise in concentration stops resorption and membrane ruffling, without destroying the osteoclasts.

Structure and expression of the bovine amelogenin gene

In order to define further the mechanisms responsible for tooth amelogenin heterogeneity, seven bovine amelogenin cDNAs were sequenced. On the basis of these sequences, five of the cDNAs could be grouped into one class which differed appreciably in sequence from the second group of two cDNAs. Two overlapping bovine genomic clones were then isolated and shown by sequencing to contain six exons encoding the entire consensus sequence of the class I cDNA. Southern blot analysis of DNA from male and female animals using class I or class II specific oligonucleotide probes suggested that the class I gene sequence was located on the X chromosome while the class II sequence was located on the Y chromosome. Therefore, these results also suggest that the genes on the X and Y chromosomes are both transcribed. Furthermore, the results are consistent with alternative splicing of the class I primary transcript as a potential mechanism for generating amelogenin heterogeneity.

Interaction of a noncytopathic human immunodeficiency virus type 1 (HIV-1) with target cells: efficient virus entry followed by delayed expression of its RNA and protein

Recently described noncytopathic human immunodeficiency viruses type-1 (HIV-1) form a new category within the HIV-1 family due to their unique biological properties and predominant occurrence in symptom-free individuals. To study the mechanism of noncytopathic HIV-1 infection, we compared the infectivity and life cycles of two closely related HIV-1 clones with noncytopathic (N1T-E) or cytopathic (N1T-A) properties. N1T-E virus exhibited slow kinetics of infection in T cells and monocytes. Slow infection was not due to defective virus entry, because N1T-E and N1T-A exhibited equally efficient virus-cell fusion activity and nucleocapsid internalization. Kinetic studies of N1T-E genome expression revealed low levels of viral RNA, structural proteins, and Tat protein during the first 7 days after virus entry. In contrast, cells infected with the same dose of cytopathic N1T-A virus began to express high levels of genomic RNA, structural proteins, and Tat protein within 48 hr of infection; the expression peaked on Day 5, followed by complete cell lysis. No delay in N1T-E replication, as compared to N1T-A, was observed after transfection of cloned N1T-E proviral DNA. N1T-E virus had intact Tat, Rev, and fusion functions and replicated well in chronically infected cells. These results suggest that delayed processing or expression of HIV-1 genome during the early phase of the virus replicative cycle is an important determinant in noncytopathic infection.

Ascorbic acid induces alkaline phosphatase, type X collagen, and calcium deposition in cultured chick chondrocytes

During the process of endochondral bone formation, proliferating chondrocytes give rise to hypertrophic chondrocytes, which then deposit a mineralized matrix to form calcified cartilage. Chondrocyte hypertrophy and matrix mineralization are associated with expression of type X collagen and the induction of high levels of the bone/liver/kidney isozyme of alkaline phosphatase. To determine what role vitamin C plays in these processes, chondrocytes derived from the cephalic portion of 14-day chick embryo sternae were grown in the absence or presence of exogenous ascorbic acid. Control untreated cells displayed low levels of type X collagen and alkaline phosphatase activity throughout the culture period. However, cells grown in the presence of ascorbic acid produced increasing levels of alkaline phosphatase activity and type X collagen mRNA and protein. Both alkaline phosphatase activity and type X collagen mRNA levels began to increase within 24 h of ascorbate treatment; by 9 days, the levels of both alkaline phosphatase activity and type X collagen mRNA were 15-20-fold higher than in non-ascorbate-treated cells. Ascorbate treatment also increased calcium deposition in the cell layer and decreased the levels of types II and IX collagen mRNAs; these effects lagged significantly behind the elevation of alkaline phosphatase and type X collagen. Addition of beta-glycerophosphate to the medium increased calcium deposition in the presence of ascorbate but had no effect on levels of collagen mRNAs or alkaline phosphatase. The results suggest that vitamin C may play an important role in endochondral bone formation by modulating gene expression in hypertrophic chondrocytes.

Functional significance of phosphorylation to the human immunodeficiency virus Rev protein

The human immunodeficiency virus Rev protein is posttranslationally modified by a serine kinase activity present in the nucleus of the cell. Site-directed mutagenesis was used to identify the site of phosphorylation. Changing of serine residues 92 and 99 dramatically reduced Rev phosphorylation, suggesting that at least one, if not both, of these residues is the one recognized by the Rev-specific serine kinase. Similarly, a truncated Rev protein lacking the 25 carboxy-terminal amino acids was not phosphorylated. By using two independent assays, both the serine mutant proteins and the truncated form of Rev were found to be fully functional. Thus, phosphorylation and the 25 carboxy-terminal amino acids appear to be dispensable for protein function.

Alkaline phosphatase cDNA transfected cells promote calcium and phosphate deposition

The full length cDNA of rat alkaline phosphatase (AP) was placed under the control of the SV40 early promoter. This plasmid was transfected by the calcium phosphate method into AP negative ROS 25/1 cells. Ten clones with AP specific activities ranging between 0.1-2 mumole/min/mg were isolated by cotransfection with the plasmid pSV2Neo, which renders the cells resistant to the antibiotic G418. Two clones with different AP specific activities: C (0.01 mumole/min/mg) and S (2.0 mumole/min/mg) and the osteoblastic ROS 17/2.8 cells (2.0 mumole/min/mg), were examined for their ability to mineralize. In vitro mineralization was tested by culturing cells in alpha-MEM containing 10% fetal bovine serum and 50 micrograms/ml ascorbate in the presence or absence of 10 mM beta-glycerophosphate. Mineralized deposits were observed in all cultures of the S clone and ROS 17/2.8 cells in the presence of beta-glycerophosphate, but not in C clones. Measurement of calcium and phosphorus levels in cells correlated with AP levels of transfected cells. However, extent of mineral accumulation in the transfected ROS 25/1 cells differ from the osteogenic ROS 17/2.8 cells. This finding indicates that high levels of AP may be a necessary constituent for the mineralization process together with other factors yet to be identified.

A gene encoding an SOS inhibitor is present in different conjugative plasmids

In 9 of 20 conjugative plasmids of different incompatibility groups, including F and R100 (or R6-5), coexist two sequences which are homologous, respectively, to the gene psiB, which encodes an inhibitor of SOS induction, and to the gene ssb, which encodes a single-stranded-DNA-binding protein.

Synthetic glycoprotein D-related peptides protect mice against herpes simplex virus challenge

Glycoprotein D (gD) of herpes simplex virus (HSV) protects mice from a lethal challenge by either HSV type 1 (HSV-1; oral) or HSV-2 (genital). We evaluated whether synthetic peptides representing residues 1 through 23 of gD (mature protein) can be used as a potential synthetic herpesvirus vaccine. The immunogenicity of the peptides was demonstrated by the biological reactivity of antipeptide sera in immunoprecipitation and neutralization assays. All sera which immunoprecipitated gD had neutralizing against both HSV-1 and HSV-2. The highest titers were found in animals immunized with the longest peptides. The region of residues 1 through 23 was immunogenic regardless of whether the type 1 or type 2 sequence was presented to the animal. Immunization of mice with gD or synthetic peptides conferred solid protection against a footpad challenge with HSV-2. However, the peptides were not as effective as gD in protection against an intraperitoneal challenge. The results suggested that synthetic vaccines based on gD show promise and should be more rigorously tested in a variety of animal models.

Analysis of the 3' region of the sheep elastin gene

The nucleotide sequences of a 1279-bp sheep elastin cDNA clone, pcSEL1 [Yoon et al. (1984) Biochem. Biophys. Res. Commun. 118, 261-269], and a 1230-bp sheep elastin genomic subclone, pSS1 [Davidson et al. (1984) Biochem. J. 220, 643-652], corresponding to a portion of the cDNA clone, were determined. These analyses permitted determination of the 100 amino acids at the carboxy terminus of sheep tropoelastin. A portion of this sequence showed strong homology to known sequences of pig tropoelastin, but most of the sequence had not been previously determined through protein sequencing. Novel aspects of the tropoelastin molecule which have been revealed by the present analyses are (i) the presence of an unusual sequence, KPPKP, which may contribute to crosslink formation; and (ii) the finding of cysteine within a sequence, CLGKSCGRKRK, at the putative carboxy terminus of tropoelastin. Because of the presence of these sequences, it is speculated that the carboxy-terminal region may be of importance in crosslinking tropoelastin molecules to themselves or to other matrix macromolecules. The nucleotide analyses revealed that sheep elastin mRNA contains a 974-bp untranslated sequence at the 3' end, which appears to be strongly conserved among species.

Localization of epitopes of herpes simplex virus type 1 glycoprotein D

We previously defined eight groups of monoclonal antibodies which react with distinct epitopes of herpes simplex virus glycoprotein D (gD). One of these, group VII antibody, was shown to react with a type-common continuous epitope within residues 11 to 19 of the mature glycoprotein (residues 36 to 44 of the predicted sequence of gD). In the current investigation, we have localized the sites of binding of two additional antibody groups which recognize continuous epitopes of gD. The use of truncated forms of gD as well as computer predictions of secondary structure and hydrophilicity were instrumental in locating these epitopes and choosing synthetic peptides to mimic their reactivity. Group II antibodies, which are type common, react with an epitope within residues 268 to 287 of the mature glycoprotein (residues 293 to 312 of the predicted sequence). Group V antibodies, which are gD-1 specific, react with an epitope within residues 340 to 356 of the mature protein (residues 365 to 381 of the predicted sequence). Four additional groups of monoclonal antibodies appear to react with discontinuous epitopes of gD-1, since the reactivity of these antibodies was lost when the glycoprotein was denatured by reduction and alkylation. Truncated forms of gD were used to localize these four epitopes to the first 260 amino acids of the mature protein. Competition experiments were used to assess the relative positions of binding of various pairs of monoclonal antibodies. In several cases, when one antibody was bound, there was no interference with the binding of an antibody from another group, indicating that the epitopes were distinct. However, in other cases, there was competition, indicating that these epitopes might share some common amino acids.

Antigenic variants of CVS rabies virus with altered glycosylation sites

The virion-associated glycoprotein of the CVS-11 strain of rabies virus exists in two forms, GI and GII, which differ in their carbohydrate content. The structural relationship between GI and GII is investigated in order to account for the difference in glycosylation. Partial sequence analysis and mapping of tryptic glycopeptides isolated from the parent CVS-11 GI and GII glycoprotein forms revealed that two of the three predicted glycosylation sites (at Asn-204 and Asn-319) were utilized in the GI form whereas only one of these two sites (at Asn-319) was utilized in the GII form. One predicted glycosylation site (at Asn-37) was not utilized in either species. In the variant virus, RV231-22, a single glycoprotein species was detected which corresponded in electrophoretic mobility to the GI form of the parent virus. Nucleotide sequence analysis of the variant glycoprotein gene revealed a base mutation which specifies an amino acid change six residues upstream from the predicted glycosylation site at Asn-204. This single amino acid substitution apparently results in utilization of the signal at Asn-204 in the GII form of RV231-22 virus. The amino acid substitution is discussed in relation to altered conformation. In the variant virus RV194-2 (F3), both GI and GII glycoprotein forms were present, but each revealed slower electrophoretic mobilities compared with the corresponding parent glycoprotein forms in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). An extra glycosylation site was identified in both glycoprotein forms of this variant virus.

Fine structure analysis of type-specific and type-common antigenic sites of herpes simplex virus glycoprotein D

The fine structure of the antigenic determinants of herpes simplex virus type 1 and 2 glycoprotein D (gD) was analyzed to determine whether structural differences underlie the differential immunogenicity of these glycoproteins. A region common to herpes simplex virus type 1 and 2 gD (amino acid residues 11 to 19) and two sites specific for herpes simplex virus type 2 gD (one determined by proline at position 7, the other determined by asparagine at position 21) were localized within the N-terminal 23 amino acids of gD by synthesis of peptides and comparison of their cross-reactivity with antisera raised to herpes simplex virus type 1 and 2 gD. The secondary structure of these peptides, as predicted by computer analysis, is discussed in relation to their immunogenicity.

Optimization of an hydroxyapatite adhesion assay for Streptococcus sanguis

Previous studies have compared the adhesion of [3H]thymidine-labeled Streptococcus sanguis to saliva-coated hydroxyapatite (SHA) and buffer-coated hydroxyapatite (HA) beads. Although the hypotonic buffer used in these assays was adjusted to simulate saliva, it does not necessarily provide the optimal parameters for the quantitative estimate of adhesion under in vitro conditions. Optimization is necessary to provide the maximum sensitivity of the assay for detecting the effects of various salivas as well as for quantitating the effect of environmental growth conditions on the adhesion of S. sanguis to SHA and HA. A major distinction between the adhesion of S. sanguis to SHA and HA was observed when the bacterial concentration was varied. At high cell concentrations, the number of cells adhering to SHA was twice the number adhering to HA. Such differences were not detected at low cell concentrations. The optimal pH for the adsorption to both SHA and HA was 6. Changes in the ionic strength or addition of mono- or divalent cations found in saliva had little effect on adhesion to HA. In contrast, high concentrations of monovalent cations inhibited adhesion to SHA. Anions such as carbonate, chloride, and sulfate did not have specific effects on adhesion, whereas acetate inhibited adhesion to both SHA and HA. Fluoride inhibited adhesion to both SHA and HA, suggesting an interaction between fluoride and hydroxyapatite. These results indicated that 2 mM phosphate buffer at a pH of 6 containing 5 mM KCl and 1 mM CaCl2 was the optimal buffer for studying the in vitro adhesion of S. sanguis to SHA.

Localization and synthesis of an antigenic determinant of herpes simplex virus glycoprotein D that stimulates the production of neutralizing antibody

An antigenic determinant capable of inducing type-common herpes simplex virus (HSV)-neutralizing antibodies has been located on glycoprotein D (gD) of HSV type 1 (HSV-1). A peptide of 16 amino acids corresponding to residues 8 to 23 of the mature glycoprotein (residues 33 to 48 of the predicted gD-1 sequence) was synthesized. This peptide reacted with an anti-gD monoclonal antibody (group VII) previously shown to neutralize the infectivity of HSV-1 and HSV-2. The peptide was also recognized by polyclonal antibodies prepared against purified gD-1 but was less reactive with anti-gD-2 sera. Sera from animals immunized with the synthetic peptide reacted with native gD and neutralized both HSV-1 and HSV-2.

Enhanced saliva-mediated bacterial aggregation and decreased bacterial adhesion in caries-resistant versus caries-susceptible individuals

A study of saliva-mediated aggregation and adhesion has been carried out in a group of caries-resistant (CR) and caries-susceptible (CS) individuals. The submandibular saliva of the CS group had a much greater potency, as determined by dilution, in promoting adherence to hydroxyapatite beads than did the saliva of CR group. In contrast, the CR group demonstrated a twofold enhancement of saliva-mediated aggregation compared with the CS group. These observations support the hypothesis that saliva-mediated aggregation and adherence are important factors in caries resistance.

Characteristic differences between saliva-dependent aggregation and adhesion of streptococci

Comparison of saliva-mediated aggregation of Streptococcus sanguis, Streptococcus mitis, and Streptococcus mutans and adhesion of these organisms to saliva-coated hydroxyapatite showed that there was no relationship between these two activities. Adsorption of salivary aggregating activity to bacteria appears to have little effect on the ability of the residual saliva to support adherence; conversely, adsorption of salivary adherence factors to hydroxyapatite does not affect aggregation. Although heating saliva significantly reduces bacterial aggregation, it has little or no effect on adherence. A comparison of aggregation and adhesion with serial dilutions of saliva demonstrated that adhesion could still be detected at 100 to 500-fold-lower concentrations of salivary protein that bacterial aggregation. These findings support the concept that aggregation and adherence involve two distinct mechanisms of microbial clearance in the oral cavity.

In vitro studies of dental plaque formation: adsorption of oral streptococci to hydroxyaptite

A mixture of saliva-coated hydroxyapatite beads and radioactively labeled bacteria has been employed as an in vitro model for the initial phase of dental plaque formation. Adsorption in this model can be expressed by the Langmuir adsorption isotherm, and the adherence of oral streptococci can be expressed as the product of the affinity constant (Ka) and the number of binding sites (N), KaN. With this approach, Streptococcus sanguis serotype 1 strains adhered better (KaN = [187 +/- 72] X 10(-2)) than serotype 2 strains (KaN = [97 +/- 84] X 10(-2)); a t test showed this difference to be statistically significant to the 99.99% confidence level. Strains of S. mitis, S. mutans, and S. salivarius did not appear to adhere as well. To analyze the bacterial receptors involved in adherence, competition studies in which increasing quantities of unlabeled bacteria were added to a fixed quantity (4 X 10(9) cells per ml) of 3H-labeled serotype 1, reference strain S. sanguis G9B, were performed. These studies indicated that the type 1 strains competed for the same, or closely related, binding sites. Competition studies using serotype 2 S. sanguis strains resulted in an increased binding of reference strain G9B to hydroxyapatite. Scanning electron microscopy indicated this effect was due to the formation of localized aggregations of bacteria, presumably representing the two bacterial types. The results of competition studies with S. mitis were variable, and several strains of other oral bacteria showed little or no competition.