Expression of the Nontypeable Haemophilus influenzae Type IV Pilus Is Stimulated by Coculture with Host Respiratory Tract Epithelial Cells.

The type IV pilus (Tfp) of nontypeable Haemophilus influenzae (NTHI) mediates adherence, colonization, motility, and biofilm formation, and the major protein subunit, PilA, is a promising vaccine candidate. Thus, it is crucial to understand how Tfp expression is regulated within the microenvironments of the human nasopharynx, which NTHI colonizes asymptomatically, and the more distal regions of the respiratory tract where NTHI-induced diseases occur. Here, we examined the effects of coculture of NTHI with human airway epithelial cells and heme availability on Tfp expression at temperatures typical of the human nasopharynx (34°C) or warmer anatomical sites during infection (37°C). Tfp expression was estimated by pilA promoter activity, pilA gene expression, and relative abundances of PilA and pilin protein. The results revealed that at both temperatures, NTHI cocultured with airway epithelial cells demonstrated significantly greater expression of pilA, PilA/pilin protein, and likely, fully assembled Tfp than NTHI cultured on an abiotic surface. Because NTHI is a heme auxotroph, we hypothesized that availability of heme from host cells might be a signal for Tfp expression. Thereby, we cultured NTHI in iron-limited medium, and we observed that supplementation with heme significantly increased pilA promoter activity. Collectively, our data suggested that NTHI Tfp expression was stimulated by soluble factor(s) released by epithelial cells, which are present in all microenvironments of the respiratory tract. The expression of this target antigen under conditions that mimic the human airway strongly supports the rationale for the use of PilA as a vaccine immunogen to prevent NTHI-induced diseases of the respiratory tract.

The anti-biofilm and anti-virulence activities of trans-resveratrol and oxyresveratrol against uropathogenic Escherichia coli.

Uropathogenic Escherichia coli (UPEC) is the primary causative agent of urinary tract infections, which are one of the most common infectious disease types in humans. UPEC infections involve bacterial cell adhesion to bladder epithelial cells, and UPEC can also form biofilms on indwelling catheters that are often tolerant to common antibiotics. In this study, the anti-biofilm activities of t-stilbene, stilbestrol, t-resveratrol, oxyresveratrol, ε-viniferin, suffruticosol A, and vitisin A were investigated against UPEC. t-Resveratrol, oxyresveratrol, and ε-viniferin, suffruticosol A, and vitisin A significantly inhibited UPEC biofilm formation at subinhibitory concentrations (10-50 µg ml-1). These findings were supported by observations that t-resveratrol and oxyresveratrol reduced fimbriae production and the swarming motility in UPEC. Furthermore, t-resveratrol and oxyresveratrol markedly diminished the hemagglutinating ability of UPEC, and enhanced UPEC killing by human whole blood. The findings show that t-resveratrol, oxyresveratrol, and resveratrol oligomers warrant further attention as antivirulence strategies against persistent UPEC infections.

Tectorigenin reduces type IV pilus-dependent cell adherence in Clostridium perfringens.

Clostridium perfringens is an anaerobic, Gram-positive bacterium that causes a range of diseases in humans and animals around the globe. The type IV pilus (TFP) system plays a key role in the colonization and invasion of host cells, biofilm formation and gliding motility, which is vital for C. perfringens infection. Therefore, targeting TFP function may be a promising strategy for the treatment of C. perfringens infection. Here, we investigated the potential inhibitory effects of tectorigenin (TE), an isoflavone extracted from the rhizome of the Chinese herb Belamcanda chinensis (L.) DC, on gliding motility, biofilm formation, adherence to cells and antibacterial activity of C. perfringens. Tectorigenin significantly inhibited gliding motility, biofilm formation and adherence to Caco-2 cells without observable antibacterial activity against C. perfringens. In addition, we also demonstrated that the inhibitory effect of TE on TFP function appears to be partially achieved by the suppression of TFP-associated genes. These findings demonstrate that TE may have the potential to be developed as a new anti-virulence drug for C. perfringens infection, particularly for the targeting of TFP.

Phytochemicals As Uropathognic Escherichia Coli FimH Antagonist: In Vitro And In Silico Approach.

BACKGROUND: Urinary tract infection (UTI) is caused by uropathogenic Escherichia coli (UPEC). The UPEC initiate pathogenesis by expressing type 1 pili, which attach to membrane receptors on the uroepithelial cells. Inhibition of attachment can provide a valuable target for prophylaxis in symptom-free milieu. METHODS: The antibacterial efficacy of alcoholic, hydroalcoholic and aqueous extracts of four plants namely Achyranthes aspera, Andrographis paniculata, Artemissia vulgaris and Glycyrrhiza glabra was evaluated against seven isolated bacterial strains and procured E. coli (UTI89/UPEC) strain. Screening of isolated strains was based on morphological characteristics and biofilm forming ability followed by physiological and biochemical analysis. RESULTS: The hydroalcoholic extracts of G. glabra at 50 µg/ml showed an impending antioxidant (DPPH) effect of 95.65% compared to ascorbic acid. The MIC values of all the plant extracts against selected bacterial strains ranged between 125 to 1000 µg/ml. In silico molecular docking performed to make out the antiadhesive role of 115 documented phytochemicals from selected plants identified quercetin-3-glucoside, ethyl caffeate, liquiritoside, liquiritin and isoliquiritigenin as potential phytochemicals. Molecular dynamics simulation performed by PTRAJ module of Amber11 package to monitor the stability of hydrogen bond showed that quercetin-3-glucoside and ethyl caffeate are potential phytochemicals as antiadhesive forming H-bonds with the FimH protein ligand. CONCLUSIONS: Aforesaid phytochemicals demonstrate effective antibacterial activity through the anti-adhesion mechanism.

Prophylactic Efficacy of Hyperimmune Bovine Colostral Antiadhesin Antibodies Against Enterotoxigenic Escherichia coli Diarrhea: A Randomized, Double-Blind, Placebo-Controlled, Phase 1 Trial.

Background: Tip-localized adhesive proteins of bacterial fimbriae from diverse pathogens confer protection in animal models, but efficacy in humans has not been reported. Enterotoxigenic Escherichia coli (ETEC) commonly elaborate colonization factors comprising a minor tip adhesin and major stalk-forming subunit. We assessed the efficacy of antiadhesin bovine colostral IgG (bIgG) antibodies against ETEC challenge in volunteers. Methods: Adults were randomly assigned (1:1:1) to take oral hyperimmune bIgG raised against CFA/I minor pilin subunit (CfaE) tip adhesin or colonization factor I (CFA/I) fimbraie (positive control) or placebo. Two days before challenge, volunteers began a thrice-daily, 7-day course of investigational product administered in sodium bicarbonate 15 minutes after each meal. On day 3, subjects drank 1 × 109 colony-forming units of colonization factor I (CFA/I)-ETEC strain H10407 with buffer. The primary efficacy endpoint was diarrhea within 120 hours of challenge. Results: After enrollment and randomization, 31 volunteers received product, underwent ETEC challenge, and were included in the per protocol efficacy analysis. Nine of 11 placebos developed diarrhea, 7 experiencing moderate to severe disease. Protective efficacy of 63% (P = .03) and 88% (P = .002) was observed in the antiadhesin bIgG and positive control groups, respectively. Conclusions: Oral administration of anti-CFA/I minor pilin subunit (CfaE) antibodies conferred significant protection against ETEC, providing the first clinical evidence that fimbrial tip adhesins function as protective antigens.

Role of Fimbriae, Flagella and Cellulose on the Attachment of Salmonella Typhimurium ATCC 14028 to Plant Cell Wall Models.

Cases of foodborne disease caused by Salmonella are frequently associated with the consumption of minimally processed produce. Bacterial cell surface components are known to be important for the attachment of bacterial pathogens to fresh produce. The role of these extracellular structures in Salmonella attachment to plant cell walls has not been investigated in detail. We investigated the role of flagella, fimbriae and cellulose on the attachment of Salmonella Typhimurium ATCC 14028 and a range of isogenic deletion mutants (ΔfliC fljB, ΔbcsA, ΔcsgA, ΔcsgA bcsA and ΔcsgD) to bacterial cellulose (BC)-based plant cell wall models [BC-Pectin (BCP), BC-Xyloglucan (BCX) and BC-Pectin-Xyloglucan (BCPX)] after growth at different temperatures (28°C and 37°C). We found that all three cell surface components were produced at 28°C but only the flagella was produced at 37°C. Flagella appeared to be most important for attachment (reduction of up to 1.5 log CFU/cm2) although both cellulose and fimbriae also aided in attachment. The csgD deletion mutant, which lacks both cellulose and fimbriae, showed significantly higher attachment as compared to wild type cells at 37°C. This may be due to the increased expression of flagella-related genes which are also indirectly regulated by the csgD gene. Our study suggests that bacterial attachment to plant cell walls is a complex process involving many factors. Although flagella, cellulose and fimbriae all aid in attachment, these structures are not the only mechanism as no strain was completely defective in its attachment.

Thermally activated charge transport in microbial protein nanowires.

The bacterium Geobacter sulfurreducens requires the expression of conductive protein filaments or pili to respire extracellular electron acceptors such as iron oxides and uranium and to wire electroactive biofilms, but the contribution of the protein fiber to charge transport has remained elusive. Here we demonstrate efficient long-range charge transport along individual pili purified free of metal and redox organic cofactors at rates high enough to satisfy the respiratory rates of the cell. Carrier characteristics were within the orders reported for organic semiconductors (mobility) and inorganic nanowires (concentration), and resistivity was within the lower ranges reported for moderately doped silicon nanowires. However, the pilus conductance and the carrier mobility decreased when one of the tyrosines of the predicted axial multistep hopping path was replaced with an alanine. Furthermore, low temperature scanning tunneling microscopy demonstrated the thermal dependence of the differential conductance at the low voltages that operate in biological systems. The results thus provide evidence for thermally activated multistep hopping as the mechanism that allows Geobacter pili to function as protein nanowires between the cell and extracellular electron acceptors.

Asymptomatic Bacteriuria in Noncatheterized Adults.

Asymptomatic bacteriuria (ASB) is a common finding and frequently detected in premenopausal nonpregnant women, institutionalized patients, patients with diabetes mellitus, and the ambulatory elderly population. Despite clear recommendations regarding diagnosis and management of ASB in these populations from the Infectious Diseases Society of America (IDSA), there remains an alarming rate of antimicrobial overuse. This article reviews definitions of ASB, epidemiology of ASB, literature surrounding ASB in diabetic patients, risk factors of ASB, microbiologic data regarding bacterial virulence, use of ASB strains for treatment of symptomatic urinary tract infection, and approaches to addressing translational barriers to implementing IDSA recommendations regarding diagnosis and management of ASB.

[Sodium houttuyfonate inhibits virulence related motility of Pseudomonas aeruginosa].

Sodium houttuyfonate (SH) is a derivative of effective component of a Chinese material medica, Houttuynia cordata, which is applied in anti-infection of microorganism. But, the antimicrobial mechanisms of SH still remain unclear. Here, we firstly discovered that SH effectively inhibits the three types of virulence related motility of.Pseudomonas aeruginosa, i.e., swimming, twitching and swarming. The plate assay results showed that the inhibitory action of SH against swimming and twitching in 24 h and swarming in 48 h is dose-dependent; and bacteria nearly lost all of the motile activities under the concentration of 1 x minimum inhibitory concentration (MIC) (512 mg x L(-1) same as azithromycin positive group (1 x MIC, 16 mg x L(-1)). Furthermore, we found that the expression of structural gene flgB and pilG is down-regulated by SH, which implies that inhibitory mechanism of SH against motility of P. aeruginosa may be due to the inhibition of flagella and pili bioformation of P. aeruginosa by SR Therefore, our presented results firstly demonstrate that SH effectively inhibits the motility activities of P. aeruginosa, and suggest that SH could be a promising antipseudomonas agents in clinic.

Expression and functional characterization of the Agrobacterium VirB2 amino acid substitution variants in T-pilus biogenesis, virulence, and transient transformation efficiency.

Agrobacterium tumefaciens is a phytopathogenic bacterium that causes crown gall disease by transferring transferred DNA (T-DNA) into the plant genome. The translocation process is mediated by the type IV secretion system (T4SS) consisting of the VirD4 coupling protein and 11 VirB proteins (VirB1 to VirB11). All VirB proteins are required for the production of T-pilus, which consists of processed VirB2 (T-pilin) and VirB5 as major and minor subunits, respectively. VirB2 is an essential component of T4SS, but the roles of VirB2 and the assembled T-pilus in Agrobacterium virulence and the T-DNA transfer process remain unknown. Here, we generated 34 VirB2 amino acid substitution variants to study the functions of VirB2 involved in VirB2 stability, extracellular VirB2/T-pilus production and virulence of A. tumefaciens. From the capacity for extracellular VirB2 production (ExB2+ or ExB2-) and tumorigenesis on tomato stems (Vir+ or Vir-), the mutants could be classified into three groups: ExB2-/Vir-, ExB2-/Vir+, and ExB2+/Vir+. We also confirmed by electron microscopy that five ExB2-/Vir+ mutants exhibited a wild-type level of virulence with their deficiency in T-pilus formation. Interestingly, although the five T-pilus-/Vir+ uncoupling mutants retained a wild-type level of tumorigenesis efficiency on tomato stems and/or potato tuber discs, their transient transformation efficiency in Arabidopsis seedlings was highly attenuated. In conclusion, we have provided evidence for a role of T-pilus in Agrobacterium transformation process and have identified the domains and amino acid residues critical for VirB2 stability, T-pilus biogenesis, tumorigenesis, and transient transformation efficiency.

New type IV pili-related genes involved in early stages of Ralstonia solanacearum potato infection.

This study provides insights into the pathogenesis of Ralstonia solanacearum, in particular with regards to strains belonging to phylotype IIB, sequevar 1 (IIB-1) and their interaction with potato, its natural host. We performed a comparative genomic analysis among IIB-1 R. solanacearum strains with different levels of virulence in order to identify candidate virulence genes. With this approach, we identified a 33.7-kb deletion in a strain showing reduced virulence on potato. This region contains a cluster of six genes putatively involved in type IV pili (Tfp) biogenesis. Functional analysis suggests that these proteins contribute to several Tfp-related functions such as twitching motility and biofilm formation. In addition, this genetic cluster was found to contribute to early bacterial wilt pathogenesis and colonization fitness of potato roots.

Screening of extracts from natural feed ingredients for their ability to reduce enterotoxigenic Escherichia coli (ETEC) K88 adhesion to porcine intestinal epithelial cell-line IPEC-J2.

Enterotoxigenic Escherichia coli (ETEC) K88 is the most prevalent enteropathogen in weaned piglets, with the ability to express fimbria F4 and specifically attach to intestinal receptors in the young piglet. The prevention of ETEC K88 adhesion to the epithelium by interfering in this fimbria-receptor recognition provides an alternative approach to prevent the initial stage of disease. The aim of this study is to screen, among different feed ingredients (FI), their ability to reduce ETEC K88 attachment to the porcine intestinal epithelial cell-line (IPEC-J2). The selected FI consisted of products of a vegetable or dairy origin, and microbial by-products, which could be suitable to be included in piglet's diet. Incubation of a mixture of each FI extract with the bacteria on IPEC-J2 monolayer was allowed. After washing with PBS to remove the non-adhered bacteria, the culture medium was added to grow the adhered bacteria and, simultaneously, to keep the cells alive. Then, the bacterial growth was monitored in a spectrophotometer reader for 12h. Casein glycomacropeptide (CGMP), locust bean (LB), exopolysaccharide (EPS) and wheat bran (WB) reduced the number of attached ETEC K88 to IPEC-J2, but no anti-adhesive effect was found for soybean hulls, sugar-beet pulp, locust gum, fructooligosaccharides, inulin, mushroom, mannanoligosaccharides or the fermented product from Aspergillus oryzae. The lineal analysis of dose responses demonstrated lineal activity (P<0.0001) for CGMP, LB, EPS and WB. These in vitro results suggest CGMP, LB, EPS and WB as good candidates to be included in piglet's diet with supported functional activity against colibacillosis.

U(VI) reduction by diverse outer surface c-type cytochromes of Geobacter sulfurreducens.

Early studies with Geobacter sulfurreducens suggested that outer-surface c-type cytochromes might play a role in U(VI) reduction, but it has recently been suggested that there is substantial U(VI) reduction at the surface of the electrically conductive pili known as microbial nanowires. This phenomenon was further investigated. A strain of G. sulfurreducens, known as Aro-5, which produces pili with substantially reduced conductivity reduced U(VI) nearly as well as the wild type, as did a strain in which the gene for PilA, the structural pilin protein, was deleted. In order to reduce rates of U(VI) reduction to levels less than 20% of the wild-type rates, it was necessary to delete the genes for the five most abundant outer surface c-type cytochromes of G. sulfurreducens. X-ray absorption near-edge structure spectroscopy demonstrated that whereas 83% ± 10% of the uranium associated with wild-type cells correspond to U(IV) after 4 h of incubation, with the quintuple mutant, 89% ± 10% of uranium was U(VI). Transmission electron microscopy and X-ray energy dispersion spectroscopy revealed that wild-type cells did not precipitate uranium along pili as previously reported, but U(IV) was precipitated at the outer cell surface. These findings are consistent with those of previous studies, which have suggested that G. sulfurreducens requires outer-surface c-type cytochromes but not pili for the reduction of soluble extracellular electron acceptors.

Electron transfer at the cell-uranium interface in Geobacter spp.

The in situ stimulation of Fe(III) oxide reduction in the subsurface stimulates the growth of Geobacter spp. and the precipitation of U(VI) from groundwater. As with Fe(III) oxide reduction, the reduction of uranium by Geobacter spp. requires the expression of their conductive pili. The pili bind the soluble uranium and catalyse its extracellular reductive precipitation along the pili filaments as a mononuclear U(IV) complexed by carbon-containing ligands. Although most of the uranium is immobilized by the pili, some uranium deposits are also observed in discreet regions of the outer membrane, consistent with the participation of redox-active foci, presumably c-type cytochromes, in the extracellular reduction of uranium. It is unlikely that cytochromes released from the outer membrane could associate with the pili and contribute to the catalysis, because scanning tunnelling microscopy spectroscopy did not reveal any haem-specific electronic features in the pili, but, rather, showed topographic and electronic features intrinsic to the pilus shaft. Pili not only enhance the rate and extent of uranium reduction per cell, but also prevent the uranium from traversing the outer membrane and mineralizing the cell envelope. As a result, pili expression preserves the essential respiratory activities of the cell envelope and the cell's viability. Hence the results support a model in which the conductive pili function as the primary mechanism for the reduction of uranium and cellular protection in Geobacter spp.

Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism.

The in situ stimulation of Fe(III) oxide reduction by Geobacter bacteria leads to the concomitant precipitation of hexavalent uranium [U(VI)] from groundwater. Despite its promise for the bioremediation of uranium contaminants, the biological mechanism behind this reaction remains elusive. Because Fe(III) oxide reduction requires the expression of Geobacter's conductive pili, we evaluated their contribution to uranium reduction in Geobacter sulfurreducens grown under pili-inducing or noninducing conditions. A pilin-deficient mutant and a genetically complemented strain with reduced outer membrane c-cytochrome content were used as controls. Pili expression significantly enhanced the rate and extent of uranium immobilization per cell and prevented periplasmic mineralization. As a result, pili expression also preserved the vital respiratory activities of the cell envelope and the cell's viability. Uranium preferentially precipitated along the pili and, to a lesser extent, on outer membrane redox-active foci. In contrast, the pilus-defective strains had different degrees of periplasmic mineralization matching well with their outer membrane c-cytochrome content. X-ray absorption spectroscopy analyses demonstrated the extracellular reduction of U(VI) by the pili to mononuclear tetravalent uranium U(IV) complexed by carbon-containing ligands, consistent with a biological reduction. In contrast, the U(IV) in the pilin-deficient mutant cells also required an additional phosphorous ligand, in agreement with the predominantly periplasmic mineralization of uranium observed in this strain. These findings demonstrate a previously unrecognized role for Geobacter conductive pili in the extracellular reduction of uranium, and highlight its essential function as a catalytic and protective cellular mechanism that is of interest for the bioremediation of uranium-contaminated groundwater.

Histone H1 proteins act as receptors for the 987P fimbriae of enterotoxigenic Escherichia coli.

The tip adhesin FasG of the 987P fimbriae of enterotoxigenic Escherichia coli mediates two distinct adhesive interactions with brush border molecules of the intestinal epithelial cells of neonatal piglets. First, FasG attaches strongly to sulfatide with hydroxylated fatty acyl chains. This interaction involves lysine 117 and other lysine residues of FasG. Second, FasG recognizes specific intestinal brush border proteins that migrate on a sodium-dodecyl sulfate-polyacrylamide gel like a distinct set of 32-35-kDa proteins, as shown by ligand blotting assays. The protein sequence of high performance liquid chromatography-purified tryptic fragments of the major protein band matched sequences of human and murine histone H1 proteins. Porcine histone H1 proteins isolated from piglet intestinal epithelial cells demonstrated the same SDS-PAGE migration pattern and 987P binding properties as the 987P-specific protein receptors from porcine intestinal brush borders. Binding was dose-dependent and shown to be specific in adhesion inhibition and gel migration shift assays. Moreover, mapping of the histone H1 binding domain suggested that it is located in their lysine-rich C-terminal domains. Histone H1 molecules were visualized on the microvilli of intestinal epithelial cells by immunohistochemistry and electron microscopy. Taken together these results indicated that the intestinal protein receptors for 987P are histone H1 proteins. It is suggested that histones are released into the intestinal lumen by the high turnover of the intestinal epithelium. Their strong cationic properties can explain their association with the negatively charged brush border surfaces. There, the histone H1 molecules stabilize the sulfatide-fimbriae interaction by simultaneously binding to the membrane and to 987P.

Glycolipid depletion in antimicrobial therapy.

Mucosal pathogens target sites of infection through specific adherence to host glycoconjugate receptors. As a consequence, depletion of such receptors from the cell surface may be expected to inhibit attachment, impair bacterial colonization and reduce the activation of mucosal inflammation. We have used the glucose analogue and glycosphingolipid (GSL) biosynthesis inhibitor N-butyldeoxynojirimycin (NB-DNJ) to deplete human uroepithelial cells and the murine urinary tract mucosa of receptors for P-fimbriated Escherichia coli. NB-DNJ blocks the ceramide-specific glucosyltransferase, which catalyses the formation of glucosyl ceramide (GlcCer), the precursor for GSLs. The inhibitor was shown to decrease the GSL content in a dose-dependent way, and depletion markedly inhibited P-fimbriated bacterial attachment in vitro. NB-DNJ-fed C3H/HeN mice were depleted of GSLs in vivo and showed reduced susceptibility to experimental urinary tract infection with P-fimbriated E. coli. The mucosal inflammatory response was impaired, as shown by reduced chemokine secretion and lower neutrophil recruitment, and the bacteria colonized the urinary tract less efficiently than in normal mice. These results confirmed the role of P fimbriae-mediated adherence for colonization and inflammation and point to an interesting alternative to antibiotic treatment for urinary tract infection.

S-fimbriae from Escherichia coli bind to soluble glycoproteins from human milk.

BACKGROUND: Escherichia coli (E. coli) strains, expressing S-fimbriae, belong to the most common gram-negative pathogens that cause sepsis and meningitis in neonates. The attachment of S-fimbriae to the cell surface is mediated by membrane glycoconjugates, which often carry N-acetylneuraminic acid. METHODS: Binding studies were performed with glycoproteins from the whey fraction of human milk to investigate whether they exert a potential inhibitory effect on bacterial adhesion. Whey glycoproteins were separated according to their molecular weight by fast protein liquid chromatography gel filtration. After sodium dodecyl sulfate-polyacrylamide gel electrophoresis, proteins were transferred to nitrocellulose membranes and incubated with isolated S-fimbriae from recombinant E. coli strain HB 101 (pANN 801-4). RESULTS: S-fimbriae recognized four whey proteins with a molecular mass of more than 200 kDa, 170 to 150 kDa, and 80 kDa. Their glycosylation pattern was investigated using the lectins Sambucus nigra, Maackia amurensis, Galanthus nivalis, and Arachis hypogaea. Thus the presence of N- and O-glycans in these proteins was confirmed. The preferential binding to N-acetylneuraminic acid containing glycoproteins was demonstrated by a complete abolishment of these reactions by incubation with acidic lactose-derived oligosaccharides. However, the cleavage of N-acetylneuraminic acid from glycoproteins by mild acid hydrolysis revealed a second binding site for S-fimbriae on milk proteins of a similar molecular weight range. Terminal galactose in human milk glycoconjugates were thought to react with S-fimbriae as well. CONCLUSION: These data further support the opinion that glycoproteins from human milk are potential receptor analogues for certain bacteria that may prevent microbial adhesion to the epithelial cell surface.

Effect of adjuvants on antibody responses of sheep immunised with recombinant pili from Dichelobacter nodosus.

OBJECTIVE: To compare the effects of two oil emulsion adjuvants (incomplete Freunds adjuvant and a proprietary oil adjuvant), DEAE-dextran, L-tyrosine particles and Quil A on the humoral immune responses of sheep immunised with recombinant pili of Dichelobacter Nodosus (strain A). PROCEDURE: Antibody titres were studied for up to 32 weeks and were measured by bacterial agglutination and ELISA. The relative avidity of antibodies for pili was determined and the incidence and severity of adverse reactions at the site of injection of vaccines were recorded. RESULTS: The oil emulsion adjuvants and Quil A were more effective than either DEAE-dextran or L-tyrosine at stimulating antibodies in sheep. The incidence and severity of adverse reactions was lower in sheep which received vaccines containing either Quil A or DEAE-dextran than in sheep which received vaccines containing oil emulsion adjuvants. L-tyrosine had no adverse effects. CONCLUSION: Quil A was as effective as oil adjuvants at stimulating high levels of antibodies against recombinant pili in sheep and had the significant advantage of being less irritant after subcutaneous injection.