Vaccination with staphylococcal protein A protects mice against systemic complications of skin infection recurrences

Skin and soft tissue infections (SSTIs) are the most common diseases caused by Staphylococcus aureus (S. aureus), which can progress to threatening conditions due to recurrences and systemic complications. Staphylococcal protein A (SpA) is an immunomodulator antigen of S. aureus, which allows bacterial evasion from the immune system by interfering with different types of immune responses to pathogen antigens. Immunization with SpA could potentially unmask the pathogen to the immune system, leading to the production of antibodies that can protect from a second encounter with S. aureus, as it occurs in skin infection recurrences. Here, we describe a study in which mice are immunized with a mutated form of SpA mixed with the Adjuvant System 01 (SpAmut/AS01) before a primary S. aureus skin infection. Although mice are not protected from the infection under these conditions, they are able to mount a broader pathogen-specific functional immune response that results in protection against systemic dissemination of bacteria following an S. aureus second infection (recurrence). We show that this "hidden effect" of SpA can be partially explained by higher functionality of induced anti-SpA antibodies, which promotes better phagocytic activity. Moreover, a broader and stronger humoral response is elicited against several S. aureus antigens that during an infection are masked by SpA activity, which could prevent S. aureus spreading from the skin through the blood.

Structure, dynamics and immunogenicity of a catalytically inactive CXC chemokine-degrading protease SpyCEP from Streptococcus pyogenes

Over 18 million disease cases and half a million deaths worldwide are estimated to be caused annually by Group A Streptococcus. A vaccine to prevent GAS disease is urgently needed. SpyCEP (Streptococcus pyogenes Cell-Envelope Proteinase) is a surface-exposed serine protease that inactivates chemokines, impairing neutrophil recruitment and bacterial clearance, and has shown promising immunogenicity in preclinical models. Although SpyCEP structure has been partially characterized, a more complete and higher resolution understanding of its antigenic features would be desirable prior to large scale manufacturing. To address these gaps and facilitate development of this globally important vaccine, we performed immunogenicity studies with a safety-engineered SpyCEP mutant, and comprehensively characterized its structure by combining X-ray crystallography, NMR spectroscopy and molecular dynamics simulations. We found that the catalytically-inactive SpyCEP antigen conferred protection similar to wild-type SpyCEP in a mouse infection model. Further, a new higher-resolution crystal structure of the inactive SpyCEP mutant provided new insights into this large chemokine protease comprising nine domains derived from two non-covalently linked fragments. NMR spectroscopy and molecular simulation analyses revealed conformational flexibility that is likely important for optimal substrate recognition and overall function. These combined immunogenicity and structural data demonstrate that the full-length SpyCEP inactive mutant is a strong candidate human vaccine antigen. These findings show how a multi-disciplinary study was used to overcome obstacles in the development of a GAS vaccine, an approach applicable to other future vaccine programs. Moreover, the information provided may also facilitate the structure-based discovery of small-molecule therapeutics targeting SpyCEP protease inhibition.

Outer Membrane Vesicles (OMV)-based and Proteomics-driven Antigen Selection Identifies Novel Factors Contributing to Bordetella pertussis Adhesion to Epithelial Cells

Despite high vaccination coverage world-wide, whooping cough, a highly contagious disease caused by Bordetella pertussis, is recently increasing in occurrence suggesting that novel vaccine formulations targeted at the prevention of colonization and transmission should be investigated. To identify new candidates for inclusion in the acellular formulation, we used spontaneously released outer membrane vesicles (OMV)1 as a potential source of key adhesins. The enrichment of Bvg+ OMV with adhesins and the ability of anti-OMV serum to inhibit the adhesion of B. pertussis to lung epithelial cells in vitro were demonstrated. We employed a proteomic approach to identify the differentially expressed proteins in OMV purified from bacteria in the Bvg+ and Bvg- virulence phases, thus comparing the outer membrane protein pattern of this pathogen in its virulent or avirulent state. Six of the most abundant outer membrane proteins were selected as candidates to be evaluated for their adhesive properties and vaccine potential. We generated E. coli strains singularly expressing the selected proteins and assessed their ability to adhere to lung epithelial cells in vitro Four out of the selected proteins conferred adhesive ability to E. coli Three of the candidates were specifically detected by anti-OMV mouse serum suggesting that these proteins are immunogenic antigens able to elicit an antibody response when displayed on the OMV. Anti-OMV serum was able to inhibit only BrkA-expressing E. coli adhesion to lung epithelial cells. Finally, stand-alone immunization of mice with recombinant BrkA resulted in significant protection against infection of the lower respiratory tract after challenge with B. pertussis Taken together, these data support the inclusion of BrkA and possibly further adhesins to the current acellular pertussis vaccines to improve the impact of vaccination on the bacterial clearance.

Development of a Click Beetle Luciferase Reporter System for Enhanced Bioluminescence Imaging of Listeria monocytogenes: Analysis in Cell Culture and Murine Infection Models

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is widely used as a model organism for the analysis of infection biology. In this context, there is a current need to develop improved reporters for enhanced bioluminescence imaging (BLI) of the pathogen in infection models. We have developed a click beetle red luciferase (CBR-luc) based vector (pPL2CBR^opt) expressing codon optimized CBR-luc under the control of a highly expressed Listerial promoter (P_HELP) for L. monocytogenes and have compared this to a lux-based system expressing bacterial luciferase for BLI of the pathogen using in vitro growth experiments and in vivo models. The CBR-luc plasmid stably integrates into the L. monocytogenes chromosome and can be used to label field isolates and laboratory strains of the pathogen. Growth experiments revealed that CBR-luc labeled L. monocytogenes emits a bright signal in exponential phase that is maintained during stationary phase. In contrast, lux-labeled bacteria produced a light signal that peaked during exponential phase and was significantly reduced during stationary phase. Light from CBR-luc labeled bacteria was more efficient than the signal from lux-labeled bacteria in penetrating an artificial tissue depth assay system. A cell invasion assay using C2Bbe1 cells and a systemic murine infection model revealed that CBR-luc is suited to BLI approaches and demonstrated enhanced sensitivity relative to lux in the context of Listeria infection models. Overall, we demonstrate that this novel CBR reporter system provides efficient, red-shifted light production relative to lux and may have significant applications in the analysis of L. monocytogenes pathogenesis.

Immunogenicity and protective efficacy induced by self-amplifying mRNA vaccines encoding bacterial antigens

Nucleic acid vaccines represent an attractive approach to vaccination, combining the positive attributes of both viral vectors and live-attenuated vaccines, without the inherent limitations of each technology. We have developed a novel technology, the Self-Amplifying mRNA (SAM) platform, which is based on the synthesis of self-amplifying mRNA formulated and delivered as a vaccine. SAM vaccines have been shown to stimulate robust innate and adaptive immune responses in small animals and non-human primates against a variety of viral antigens, thus representing a safe and versatile tool against viral infections. To assess whether the SAM technology could be used for a broader range of targets, we investigated the immunogenicity and efficacy of SAM vaccines expressing antigens from Group A (GAS) and Group B (GBS) Streptococci, as models of bacterial pathogens. Two prototype bacterial antigens (the double-mutated GAS Streptolysin-O (SLOdm) and the GBS pilus 2a backbone protein (BP-2a)) were successfully expressed by SAM vectors. Mice immunized with both vaccines produced significant amounts of fully functional serum antibodies. The antibody responses generated by SAM vaccines were capable of conferring consistent protection in murine models of GAS and GBS infections. Inclusion of a eukaryotic secretion signal or boosting with the recombinant protein resulted in higher specific-antibody levels and protection. Our results support the concept of using SAM vaccines as potential solution for a wide range of both viral and bacterial pathogens, due to the versatility of the manufacturing processes and the broad spectrum of elicited protective immune response.

One Dose of Staphylococcus aureus 4C-Staph Vaccine Formulated with a Novel TLR7-Dependent Adjuvant Rapidly Protects Mice through Antibodies, Effector CD4+ T Cells, and IL-17A

A rapidly acting, single dose vaccine against Staphylococcus aureus would be highly beneficial for patients scheduled for major surgeries or in intensive care units. Here we show that one immunization with a multicomponent S. aureus candidate vaccine, 4C-Staph, formulated with a novel TLR7-dependent adjuvant, T7-alum, readily protected mice from death and from bacterial dissemination, both in kidney abscess and peritonitis models, outperforming alum-formulated vaccine. This increased efficacy was paralleled by higher vaccine-specific and α-hemolysin-neutralizing antibody titers and Th1/Th17 cell responses. Antibodies played a crucial protective role, as shown by the lack of protection of 4C-Staph/T7-alum vaccine in B-cell-deficient mice and by serum transfer experiments. Depletion of effector CD4⁺ T cells not only reduced survival but also increased S. aureus load in kidneys of mice immunized with 4C-Staph/T7-alum. The role of IL-17A in the control of bacterial dissemination in 4C-Staph/T7-alum vaccinated mice was indicated by in vivo neutralization experiments. We conclude that single dose 4C-Staph/T7-alum vaccine promptly and efficiently protected mice against S. aureus through the combined actions of antibodies, CD4⁺ effector T cells, and IL-17A. These data suggest that inclusion of an adjuvant that induces not only fast antibody responses but also IL-17-producing cell-mediated effector responses could efficaciously protect patients scheduled for major surgeries or in intensive care units.

MF59- and Al(OH)3-Adjuvanted Staphylococcus aureus (4C-Staph) Vaccines Induce Sustained Protective Humoral and Cellular Immune Responses, with a Critical Role for Effector CD4 T Cells at Low Antibody Titers

Staphylococcus aureus (S. aureus) is an important opportunistic pathogen that may cause invasive life-threatening infections, like sepsis and pneumonia. Due to the increasing antibiotic resistance, the development of an effective vaccine against S. aureus is needed. Although a correlate of protection against staphylococcal diseases is not yet established, several findings suggest that both antibodies and CD4 T cells might contribute to optimal immunity. In this study, we show that adjuvanting a multivalent vaccine (4C-Staph) with MF59, an oil-in-water emulsion licensed in human vaccines, further potentiated antigen-specific IgG titers and CD4 T-cell responses compared to alum and conferred protection in the peritonitis model of S. aureus infection. Moreover, we showed that MF59- and alum-adjuvanted 4C-Staph vaccines induced persistent antigen-specific humoral and T-cell responses, and protected mice from infection up to 4 months after immunization. Furthermore, 4C-Staph formulated with MF59 was used to investigate which immune compartment is involved in vaccine-induced protection. Using CD4 T cell-depleted mice or B cell-deficient mice, we demonstrated that both T and B-cell responses contributed to 4C-Staph vaccine-mediated protective immunity. However, the role of CD4 T cells seemed more evident in the presence of low-antibody responses. This study provides preclinical data further supporting the use of the adjuvanted 4C-Staph vaccines against S. aureus diseases, and provides critical insights on the correlates of protective immunity necessary to combat this pathogen.

Antibody-mediated immunity induced by engineered Escherichia coli OMVs carrying heterologous antigens in their lumen

Background

Outer membrane vesicles (OMVs) from Gram-negative bacteria are gaining increasing attention as vaccine platform for their built-in adjuvanticity and for their potential use as carriers of heterologous antigens. These 2 properties offer the opportunity to make highly effective, easy to produce multi-valent vaccines. OMVs can be loaded with foreign antigens by targeting protein expression either to the outer membrane or to the periplasm of the OMV-producing strain. Periplasmic expression is simple and relatively efficient but leads to the accumulation of recombinant antigens in the lumen of OMVs and the ability of OMVs carrying internalized antigens to induce antigen-specific antibody responses has been only marginally investigated and is considered to be sub-optimal.

Methods

We have systematically analyzed in qualitative and quantitative terms antibody responses induced by OMVs carrying different heterologous antigens in their lumen. Group A Streptococcus (GAS) Slo, SpyCEP, Spy0269 and Group B Streptococcus (GBS) SAM_1372 were fused to the OmpA leader sequence for secretion and expressed in Escherichia coli. OMVs from the recombinant strains were purified and tested for immunogenicity and protective activity.

Results

All proteins were incorporated into the OMVs lumen in their native conformation. Upon mice immunization, OMVs induced high functional antibody titers against the recombinant proteins. Furthermore, immunization with Slo-OMVs and SpyCEP-OMVs protected mice against GAS lethal challenge.

Conclusions

The efficiency of antigen delivery to the vesicular lumen via periplasmic expression, and the surprisingly high immunogenicity and protective activity of OMVs carrying internalized recombinant antigens further strengthens the potential of OMVs as vaccine platform.

SpyAD, a moonlighting protein of group A Streptococcus contributing to bacterial division and host cell adhesion

Group A streptococcus (GAS) is a human pathogen causing a wide repertoire of mild and severe diseases for which no vaccine is yet available. We recently reported the identification of three protein antigens that in combination conferred wide protection against GAS infection in mice. Here we focused our attention on the characterization of one of these three antigens, Spy0269, a highly conserved, surface-exposed, and immunogenic protein of unknown function. Deletion of the spy0269 gene in a GAS M1 isolate resulted in very long bacterial chains, which is indicative of an impaired capacity of the knockout mutant to properly divide. Confocal microscopy and immunoprecipitation experiments demonstrated that the protein was mainly localized at the cell septum and could interact in vitro with the cell division protein FtsZ, leading us to hypothesize that Spy0269 is a member of the GAS divisome machinery. Predicted structural domains and sequence homologies with known streptococcal adhesins suggested that this antigen could also play a role in mediating GAS interaction with host cells. This hypothesis was confirmed by showing that recombinant Spy0269 could bind to mammalian epithelial cells in vitro and that Lactococcus lactis expressing Spy0269 on its cell surface could adhere to mammalian cells in vitro and to mice nasal mucosa in vivo. On the basis of these data, we believe that Spy0269 is involved both in bacterial cell division and in adhesion to host cells and we propose to rename this multifunctional moonlighting protein as SpyAD (Streptococcus pyogenes Adhesion and Division protein).

SslE elicits functional antibodies that impair in vitro mucinase activity and in vivo colonization by both intestinal and extraintestinal Escherichia coli strains

SslE, the Secreted and surface-associated lipoprotein from Escherichia coli, has recently been associated to the M60-like extracellular zinc-metalloprotease sub-family which is implicated in glycan recognition and processing. SslE can be divided into two main variants and we recently proposed it as a potential vaccine candidate. By applying a number of in vitro bioassays and comparing wild type, knockout mutant and complemented strains, we have now demonstrated that SslE specifically contributes to degradation of mucin substrates, typically present in the intestine and bladder. Mutation of the zinc metallopeptidase motif of SslE dramatically impaired E. coli mucinase activity, confirming the specificity of the phenotype observed. Moreover, antibodies raised against variant I SslE, cloned from strain IHE3034 (SslE_IHE3034), are able to inhibit translocation of E. coli strains expressing different variants through a mucin-based matrix, suggesting that SslE induces cross-reactive functional antibodies that affect the metallopeptidase activity. To test this hypothesis, we used well-established animal models and demonstrated that immunization with SslE_IHE3034 significantly reduced gut, kidney and spleen colonization by strains producing variant II SslE and belonging to different pathotypes. Taken together, these data strongly support the importance of SslE in E. coli colonization of mucosal surfaces and reinforce the use of this antigen as a component of a broadly protective vaccine against pathogenic E. coli species.

Escherichia coli are the predominant facultative anaerobe of the human colonic flora. Although intestinal and extraintestinal pathogenic E. coli are phylogenetically and epidemiologically distinct, we recently proposed a number of protective antigens conserved in most E. coli pathotypes. In this study, we have elucidated the function of the most promising of these antigens, SslE, which is characterized by the presence of a M60-like domain representative of a new extracellular zinc-metalloprotease sub-family. In particular, in vitro analysis of the ability of an sslE knockout mutant strain to transverse an agar-based mucin matrix revealed that SslE is essential to E. coli mucinase activity. Evidence showing that SslE induces functional antibodies, preventing both in vitro mucin degradation but also in vivo gut, kidney and spleen colonization, further support the hypothesis that SslE may facilitate E. coli colonization by favoring the penetration of the sterile inner mucus layer leading to interaction with host cells. Finally, the ability of SslE to also induce protective immunity against sepsis, linked to its presence among different pathotypes, supports the use of such an antigen as a broadly protective E. coli vaccine candidate.

Multi high-throughput approach for highly selective identification of vaccine candidates: the Group A Streptococcus case

We propose an experimental strategy for highly accurate selection of candidates for bacterial vaccines without using in vitro and/or in vivo protection assays. Starting from the observation that efficacious vaccines are constituted by conserved, surface-associated and/or secreted components, the strategy contemplates the parallel application of three high throughput technologies, i.e. mass spectrometry-based proteomics, protein array, and flow-cytometry analysis, to identify this category of proteins, and is based on the assumption that the antigens identified by all three technologies are the protective ones. When we tested this strategy for Group A Streptococcus, we selected a total of 40 proteins, of which only six identified by all three approaches. When the 40 proteins were tested in a mouse model, only six were found to be protective and five of these belonged to the group of antigens in common to the three technologies. Finally, a combination of three protective antigens conferred broad protection against a panel of four different Group A Streptococcus strains. This approach may find general application as an accelerated and highly accurate path to bacterial vaccine discovery.

Scavenger receptor gp340 aggregates group A streptococci by binding pili

Group A streptococci (GAS) are the most frequent cause of bacterial pharyngitis. The first obstacle to GAS colonization of the pharynx is saliva. As well as forming a physical barrier, saliva contains components of innate and acquired immunity. Previous work has shown that saliva induces bacterial aggregation, which may serve as a clearance mechanism. As the aggregation of some oral streptococci in saliva is mediated by long proteinaceous appendages, we hypothesized that pili of GAS might behave similarly. Wild-type GAS M1 strain SF370 aggregated in saliva, while pilus-defective mutants did not. Similarly, heterologous expression of diverse GAS pili on the surface of Lactococcus lactis induced aggregation in saliva, while control strains were unaffected. Further studies revealed that aggregating bacteria bound salivary component gp340. Purified gp340 aggregated wild-type GAS and L. lactis expressing GAS pili, but not control strains. GAS pilus-defective mutants were abrogated in gp340 binding and aggregation. Furthermore, gp340-mediated aggregation reduced bacterial adhesion to human epithelial cells, suggesting a role in host defence.

Streptococcus pyogenes pili promote pharyngeal cell adhesion and biofilm formation

Group A Streptococcus (GAS, Streptococcus pyogenes) is a Gram-positive human pathogen responsible for several acute diseases and autoimmune sequelae that account for half a million deaths worldwide every year. GAS infections require the capacity of the pathogen to adhere to host tissues and assemble in cell aggregates. Furthermore, a role for biofilms in GAS pathogenesis has recently been proposed. Here we investigated the role of GAS pili in biofilm formation. We demonstrated that GAS pilus-negative mutants, in which the genes encoding either the pilus backbone structural protein or the sortase C1 have been deleted, showed an impaired capacity to attach to a pharyngeal cell line. The same mutants were much less efficient in forming cellular aggregates in liquid culture and microcolonies on human cells. Furthermore, mutant strains were incapable of producing the typical three-dimensional layer with bacterial microcolonies embedded in a carbohydrate polymeric matrix. Complemented mutants had an adhesion and aggregation phenotype similar to the wild-type strain. Finally, in vivo expression of pili was indirectly confirmed by demonstrating that most of the sera from human patients affected by GAS-mediated pharyngitis recognized recombinant pili proteins. These data support the role of pili in GAS adherence and colonization and suggest a general role of pili in all pathogenic streptococci.

Characterization and identification of vaccine candidate proteins through analysis of the group A Streptococcus surface proteome

We describe a proteomic approach for identifying bacterial surface-exposed proteins quickly and reliably for their use as vaccine candidates. Whole cells are treated with proteases to selectively digest protruding proteins that are subsequently identified by mass spectrometry analysis of the released peptides. When applied to the sequenced M1_SF370 group A Streptococcus strain, 68 PSORT-predicted surface-associated proteins were identified, including most of the protective antigens described in the literature. The number of surface-exposed proteins varied from strain to strain, most likely as a consequence of different capsule content. The surface-exposed proteins of the highly virulent M23_DSM2071 strain included 17 proteins, 15 in common with M1_SF370. When 14 of the 17 proteins were expressed in E. coli and tested in the mouse for their capacity to confer protection against a lethal dose of M23_DSM2071, one new protective antigen (Spy0416) was identified. This strategy overcomes the difficulties so far encountered in surface protein characterization and has great potential in vaccine discovery.

Group A Streptococcus produce pilus-like structures containing protective antigens and Lancefield T antigens

Although pili have long been recognized in Gram-negative pathogens as important virulence factors involved in adhesion and invasion, very little is known about extended surface organelles in Gram-positive pathogens. Here we report that Group A Streptococcus (GAS), a Gram-positive human-specific pathogen that causes pharyngitis, impetigo, invasive disease, necrotizing fasciitis, and autoimmune sequelae has long, surface-exposed, pilus-like structures composed of members of a family of extracellular matrix-binding proteins. We describe four variant pili and show that each is recognized by a specific serum of the Lancefield T-typing system, which has been used for over five decades to characterize GAS isolates. Furthermore, we show that immunization of mice with a combination of recombinant pilus proteins confers protection against mucosal challenge with virulent GAS bacteria. The data indicate that induction of a protective immune response against these structures may be a useful strategy for development of a vaccine against disease caused by GAS infection.

Chlamydia pneumoniae genome sequence analysis and identification of HLA-A2-restricted CD8+ T cell epitopes recognized by infection-primed T cells

In the present study, we performed in silico analysis of Chlamydia pneumoniae genome sequence to identify human HLA-A2-restricted T cell epitopes. Thirty-one Chlamydia-specific protein antigens were selected and peptides were derived thereof using an HLA-A2 epitope predictive algorithm. Firstly, we tested binding of 55 selected 9mer peptides to HLA-A2 in vitro. Next, infection of HLA-A2 transgenic mice with C. pneumoniae elementary bodies and assessment of effector CD8+ T cells allowed us to identify which of the epitopes binding to HLA-A2 in vitro were recognized by C. pneumoniae infection-primed CD8+ T cells. Finally, we could confirm that CD8+ T cells in association with HLA-A2 recognized the most reactive peptides when the corresponding full-length genes were used to DNA-immunize HLA-A2 transgenic mice. By using this approach, a novel HLA-A2-restricted epitope in the outer membrane protein A (OmpA) of C. pneumoniae was identified, which proved to mediate specific lysis of peptide-loaded target cells.

Effect of twelve-months therapy with oral ambroxol in preventing exacerbations in patients with COPD. Double-blind, randomized, multicenter, placebo-controlled study (the AMETHIST Trial)

The objective of this prospective, randomized, double-blind, placebo-controlled, multicenter parallel-group study was to evaluate the effect of long-term ambroxol treatment in preventing exacerbations of chronic obstructive pulmonary disease (COPD). Two hundred and forty-two outpatients with COPD defined by ATS criteria with value of FEV1 between > or =60 and 80% of predicted and history of one or more exacerbations in the previous year were recruited by 26 Respiratory Medicine Centers in Italy and treated for 1 year with one ambroxol retard capsule of 75 mg twice daily or placebo. The percentage of patients free from exacerbation at 6 months was 63% with ambroxol and 60% with placebo (p=0.366) and at 12 months 56% with ambroxol and 53% with placebo (p=0.363). In a subset of 45 patients with more severe baseline symptoms, ambroxol therapy was associated with a significant higher percentage of patients free from exacerbation compared to placebo: 63 vs. 38% (p=0.038). In conclusion, we did not find a significant difference between long-term ambroxol therapy and placebo, in preventing exacerbations in patients with COPD. In patients with more severe respiratory symptoms at baseline, however, we observed a significant difference in the cumulative exacerbation-free persistence between ambroxol and placebo, suggesting that long-term muco-regulatory therapy with ambroxol could be useful in highly symptomatic patients with COPD.

Efficacy and safety of oxitropium bromide, theophylline and their combination in COPD patients: a double-blind, randomized, multicentre study (BREATH Trial)

We compare the efficacy including spirometry, peak expiratory flow (PEFR) and quality of life and safety of an 8-week treatment with inhaled oxitropium, theophylline or their combination in patients with mild-to-severe chronic obstructive pulmonary disease (COPD). We conducted a multicentre, double-blind, double-dummy randomized, parallel-group study at 29 Italian outpatients clinics. A group of 236 patients with mild-to-severe COPD (baseline FEV1 < or = 70% of predicted value) were recruited. Treatments were as follows: Inhaled oxitropium bromide 200 microg (N=75), sustained-release oral theophylline 300 mg (N=81) or their combination (N=80), taken twice daily. Spirometry (FEV1 and FVC) was evaluated every 4 weeks, and morning and evening PEFR (before and 2-4 h after drug intake) was measured daily. Symptoms, cough and dysponea, were recorded daily. Health status was evaluated at baseline and week 8 using the disease specific St George' Respiratory Questionnaire (SGRQ). Any adverse event occurring during the treatment period was recorded on a diary card. FEV1 and FVC improved in all the groups at 4 and 8 weeks, but the difference between treatment groups did not reach statistically significant levels. Differences between groups in pre-dosing morning and evening PEFR were not significant. Post-dosing morning and evening PEFR were increased and the largest increase was seen in patients treated with both drugs. However, differences between groups was significant only for evening values (P=0.008). The proportion of patients who experienced a decrease in symptoms was high in all groups but no differences among groups were observed. SGRQ total scores decreased in all treatment groups after 8 weeks, particularly in the oxitropium and combination groups. Clinically significant change (> or = 4 units) was only observed in patients treated with oxitropium bromide whether with or without theophylline. Adverse events related to treatments were higher in the group treated with theophylline alone (P < 0.02). We conclude that inhaled oxitropium bromide alone was associated with an improvement in FEV1, PEFR and symptoms in patients with COPD that was not statistically different from that of oral theophylline alone or of the combination of both drugs. Oxitropium bromide in combination with theophylline provided a greater improvement in evening post-dosing PEFR. Oxitropium bromide alone or in combination with theophylline improved the quality of life better than theophylline alone.

Yeast coexpression of human papillomavirus types 6 and 16 capsid proteins

The L1 and L2 capsid proteins of animal and human papillomaviruses (HPVs) can self-assemble into virus-like particles (VLPs) that closely resemble native virions. The use of different animal models shows that VLPs can be very efficient at inducing a protective immune response. However, studies with infectious HPV virions and VLPs of different HPV types indicate that the immune response is predominantly type-specific. We have generated a diploid yeast strain that coexpresses the L1 and L2 capsid proteins of both HPV-6b and HPV-16, and we have purified fully assembled VLPs banding in a cesium chloride gradient at the expected density of 1.29-1.3 mg/ml. Experimental evidence strongly indicated that the four proteins coassembled into VLPs. Western blot analysis, using anti-HPV-6 and anti-HPV-16 L1-specific monoclonal antibodies and type-specific L2 antisera, demonstrated that all four proteins copurified. Most importantly, immunoprecipitation experiments, carried out using type-specific anti-L1 monoclonals and either total yeast cell extracts or purified VLPs, confirmed the interaction and the formation of covalent disulfide bonds between the two L1 proteins. Finally, HPV-6/16 VLPs administered to mice induced conformational antibodies against both L1 protein types. These results suggest that coexpression of different capsid proteins may provide new tools for the induction of antibodies directed against multiple HPV types.

Thymic hyperplasia and lung carcinomas in a line of mice transgenic for keratin 5-driven HPV16 E6/E7 oncogenes

Human Papillomavirus type 16 (HPV-16) is the cause of both benign lesions and ano-genital cancers. In HPV-associated cancers the transforming properties of the expressed viral E6 and E7 proteins have been revealed by a number of different assays. We have generated transgenic mice expressing HPV-16 E6/E7 genes under the control of the murine keratin 5 gene promoter, which should confer cell-type specific expression in the basal cells of squamous stratified epithelia. Transgenic mice developed thymic hyperplasia and lung neoplasia with 100% frequency, the thymus showing a size increase at 2 months and reaching the maximum dimension at 6 months, when lung carcinomas appeared. After this time the size of hyperplastic thymi decreased, while malignant formations invaded the mediastinal area. Hepatic metastasis could be also observed in some of the animals at the autopsy and death invariably occurred around 10-11 months of age.

The comparison of the effect of LTR72 and MF59 adjuvants on mouse humoral response to intranasal immunisation with human papillomavirus type 6b (HPV-6b) virus-like particles

Infections with genital human papillomaviruses (HPV) are likely to be neutralised more efficiently if a mucosal immune response can be elicited at the viral entry site. Local IgA antibodies are highly induced when antigens are co-administered with mucosal adjuvants, such as cholera toxin (CT) and Escherichia coli heat labile enterotoxin (LT) which, however, are not expected to have wide application because of their pronounced toxicity. We have immunised mice intranasally with HPV-6b virus-like particles (VLPs) and a genetically modified LT-derived molecule with only residual toxicity, LTR72, and compared the humoral responses with those obtained following systemic immunisation with VLPs and the MF59 adjuvant. Titration of anti-HPV antibodies in sera and vaginal secretions established that LTR72 was able to elicit higher serum and mucosal IgA titers, in addition to IgG serum levels, comparable to those obtained by parenteral immunisation. These results confirm the potential of toxin-derived adjuvants and extend their use in combination with HPV antigens.

Evaluation of hepatitis C virus glycoprotein E2 for vaccine design: an endoplasmic reticulum-retained recombinant protein is superior to secreted recombinant protein and DNA-based vaccine candidates

Hepatitis C virus (HCV) is the leading causative agent of blood-borne chronic hepatitis and is the target of intensive vaccine research. The virus genome encodes a number of structural and nonstructural antigens which could be used in a subunit vaccine. The HCV envelope glycoprotein E2 has recently been shown to bind CD81 on human cells and therefore is a prime candidate for inclusion in any such vaccine. The experiments presented here assessed the optimal form of HCV E2 antigen from the perspective of antibody generation. The quality of recombinant E2 protein was evaluated by both the capacity to bind its putative receptor CD81 on human cells and the ability to elicit antibodies that inhibited this binding (NOB antibodies). We show that truncated E2 proteins expressed in mammalian cells bind with high efficiency to human cells and elicit NOB antibodies in guinea pigs only when purified from the core-glycosylated intracellular fraction, whereas the complex-glycosylated secreted fraction does not bind and elicits no NOB antibodies. We also show that carbohydrate moieties are not necessary for E2 binding to human cells and that only the monomeric nonaggregated fraction can bind to CD81. Moreover, comparing recombinant intracellular E2 protein to several E2-encoding DNA vaccines in mice, we found that protein immunization is superior to DNA in both the quantity and quality of the antibody response elicited. Together, our data suggest that to elicit antibodies aimed at blocking HCV binding to CD81 on human cells, the antigen of choice is a mammalian cell-expressed, monomeric E2 protein purified from the intracellular fraction.

Intravenous itasetron: establishing the effective dose range for the prophylactic control of acute emesis in cancer patients undergoing high-dose cisplatin chemotherapy

Nausea and vomiting induced by chemotherapy are a major cause of distress to patients and reduce compliance with potentially beneficial treatment. Itasetron hydrochloride is a new 5-hydroxytryptamine3 (5-HT3) antagonist with potent antiemetic properties. It is more potent than ondansetron in animal models and in early clinical studies it demonstrates a long half-life and does not undergo hepatic biotransformation before elimination. The aim of this open, uncontrolled study was to establish the effective dose range of itasetron hydrochloride given intravenously (i.v.) to patients due to receive high-dose cisplatin chemotherapy (50-120 mg/m2) for the first time. Thirty-nine patients were enrolled in the trial and received a single i.v. infusion of itasetron hydrochloride at a dose of 17-280 microg/kg body weight before commencing the cisplatin infusion (median dose 90-110 mg/m2). Antiemetic protection was demonstrated by doses in the range of 35-280 microg/kg. The 17 microg/kg dose was not effective. Treatment failure (>5 emetic episodes/24 hours) was reported in only six (16%) of the 38 evaluable patients over all treatment groups. Adverse events were generally mild or moderate and of a similar type and incidence to those of current 5-HT3 antagonists. Physicians' and patients' assessments of efficacy and tolerability of itasetron hydrochloride were similar, the majority rating the treatment as 'good' or 'very good'. In conclusion, itasetron hydrochloride is effective in the dose range 35-280 microg/kg in preventing cisplatin-induced emesis. Taken together with results from a larger dose-finding study, a dose corresponding to 35 microg/kg (equivalent to 2.5 mg itasetron, calculated as free base) has been pursued in Phase III studies with the i.v. formulation.

Twenty-four-hour intragastric acidity following early evening or bedtime administration of roxatidine in duodenal ulcer patients

AIM

To assess the usefulness of early evening administration of roxatidine 150 mg as an alternative to the traditional bedtime regimen.

METHODS

Twenty-four patients with healed duodenal ulcer were dosed according to a balanced incomplete-block design, with two of the following regimens: placebo, roxatidine 150 mg at 07.30 h (early evening) or roxatidine 150 mg at 22.00 h (bedtime). Twenty-four-hour intragastric pH-metry was started at 18.00 h on the first day of dosing. Median pH was determined for the 24-h period, and for the following time intervals: 20.00-00.00 h, 00.00-08.00 h and 08.00-18.00 h. Percentage time in the 24-h period with pH greater than 4.0 was also calculated.

RESULTS

The two roxatidine regimens proved significantly superior to the placebo, decreasing 24-h acidity for all the time intervals, except the 20.00-00.00 h period, when mean intragastric pH with the early evening regimen (4.5 +/- 1.1) proved significantly higher than after placebo (2.2 +/- 1.0) or when roxatidine was taken at bedtime (2.4 +/- 1.1).

CONCLUSION

Early evening administration of roxatidine may afford satisfactory control of 24-h acidity, offering a useful alternative to conventional bedtime administration.

A nuclear protein, synthesized in growth-arrested human hepatoblastoma cells, is a novel member of the short-chain alcohol dehydrogenase family

We have described a protein (Hep27) [Donadel, G., Garzelli, C., Frank, R. & Gabrielli, F. (1991) Eur. J. Biochem. 195, 723-729] which is synthesized and accumulated in the nucleus of human hepatoblastoma (HepG2) cells, following growth arrest induced by butyrate treatment. The synthesis of Hep27 is inhibited in cells that, released from the butyrate block, have resumed DNA synthesis. This report describes the cloning and the characterization of the cDNA coding for the Hep27 protein. The translation of the Hep27 cDNA predicts an amino acid sequence that can be aligned with those of the known short-chain alcohol dehydrogenase enzymes (SCAD) family. Both the recognition of enzymic functional domains and the similarity with the SCAD family of proteins of several amino acid blocks throughout the molecule, strongly suggest that this protein is a new member of the SCAD family. In agreement with its nuclear localization Hep27 has a region similar to the bipartite nuclear-targeting sequence. The study of Hep27 mRNA expression and protein synthesis suggests the existence of a regulation at the post-transcriptional level. The possible nuclear role of the Hep27 protein is discussed.

Double-blind randomized, multicenter study comparing aluminium phosphate gel with rantitidine in the short-term treatment of duodenal ulcer

The efficacy and safety of aluminium phosphate and ranitidine in the short-term treatment of duodenal ulcer were compared in a multicenter, randomized, double-blind study. A total of 304 patients with endoscopically proven active duodenal ulcer were recruited: 153 received 11 g of aluminium phosphate gel five times a day (equivalent to a daily acid buffering capacity of 182 mEq/HC1) and 151 rantitidine 300 mg once daily for 6 weeks. At the end of the treatment period, 74 out of 113 patients (65%) treated with aluminium phosphate and 84 out of 105 patients (80%) treated with rantitidine showed ulcer healing at endoscopy (p = 0.02). Ulcer symptoms, identified as frequency and intensity of daytime and nocturnal epigastric pain, were significantly reduced by both treatments, but rantitidine proved more effective than aluminium phosphate in reducing the frequency of daytime pain (p < 0.01) and its severity (p < 0.01); in contrast, no significant differences were found with regard to frequency and severity of nocturnal pain. The incidence of unwanted effects was significantly higher in the aluminium phosphate group. The main adverse event observed was constipation which, however, was hardly ever severe enough to warrant discontinuing treatment.

Characterization of a functional NF-kappa B site in the human interleukin 1 beta promoter: evidence for a positive autoregulatory loop

The -300 region of the interleukin 1 beta (IL-1 beta) promoter contains a functional NF-kappa B binding site composed of the decamer sequence 5'-GGGAAAATCC-3'. Probes representing the -300 region or the NF-kappa B site alone interacted with NF-kappa B proteins present in phorbol myristate acetate-, lipopolysaccharide-, or Sendai virus-induced myeloid cell extracts as well as recombinant NFKB1 (p50) and RelA (p65); furthermore, NF-kappa B protein-DNA complex formation was dissociated in vitro by the addition of recombinant I kappa B alpha. Mutation of the NF-kappa B site in the context of the IL-1 beta promoter reduced the responsiveness of the IL-1 beta promoter to various inducers, including phorbol ester, Sendai virus, poly(rI-rC), and IL-1 beta. A 4.4-kb IL-1 beta promoter fragment linked to a chloramphenicol acetyltransferase reporter gene was also preferentially inducible by coexpression of individual NF-kappa B subunits compared with a mutated IL-1 beta promoter fragment. When multiple copies of the IL-1 beta NF-kappa B site were linked to an enhancerless simian virus 40 promoter, this element was able to mediate phorbol ester- or lipopolysaccharide-inducible gene expression. In cotransfection experiments, RelA (p65) and c-Rel (p85) were identified as the main subunits responsible for the activation of the IL-1 beta NF-kappa B site; also, combinations of NFKB1 (p50) and RelA (p65) or c-Rel and RelA were strong transcriptional activators of reporter gene activity. The presence of a functional NF-kappa B binding site in the IL-1 beta promoter suggests that IL-1 positively autoregulates its own synthesis, since IL-1 is a strong inducer of NF-kappa B binding activity. Thus, the IL-1 beta gene may be considered as an important additional member of the family of cytokine genes regulated in part by the NF-kappa B/rel family of transcription factors.

Loop substitution as a tool to identify active sites of interleukin-1 beta

By computer analysis of the amino acid sequence of human interleukin-1 beta (IL-1 beta) and of the human type I IL-1 receptor (IL-1RI), we have identified two hydropathically complementary peptides (Fassina, G., Roller, P. P., Olson, A. D., Thorgeirsson, S. S., and Omichinski, J. G. (1989) J. Biol. Chem. 264, 11252-11257) capable of binding to each other. The sequence of the IL-1 beta peptide corresponds to that of residues 88-99 (loop 7 of the crystal structure of mature IL-1 beta) of mature IL-1 beta, one of the exposed and highly charged regions of the molecule. The substitution of this loop with an amino acid sequence of the same length but different hydropathic profile generates a mutant with drastically reduced binding activity to IL-1RI. In contrast, the binding affinity to the type II IL-1R (IL-1RII) is the same as that of wild type IL-1 beta. The results show that 1) loop 7 is part of the binding site of IL-1 beta to IL-1RI, but not to IL-1RII. 2) The structure of the mutant protein is not grossly altered except locally at the position of the substituted loop. 3) The substitution of amino acids by site-directed mutagenesis of the loop 7 region generates mutants with binding affinity constants slightly lower than that of wild type IL-1 beta and not comparable to that of the loop substitution analogue. 4. All mutants analyzed, including the loop substitutions, are biologically active, confirming the structural integrity of the proteins. We propose a binding site in which the cooperation of several low energy bonds extended over a wide area results in a high affinity complex between IL-1 and the type I receptor.

Operative arthroscopy of the ankle

The long-term results of 30 operative arthroscopies of the ankle performed from 1983 to 1989 are the basis of this study. The most frequent lesions are synovitis and osteochondral defects of the talus. The treatment consists of lavage, synovial debridement, osteochondral debridement, and the removal of loose bodies. Of the 30 cases, 86.7% obtained excellent or good results and 88% of the athletes returned to their sport.

An inducible enhancer controls the expression of the human interleukin 1 beta gene

This paper describes regulatory sequences responsible for the control of human interleukin 1 beta gene expression in cells of the monocytic lineage. Hybrid plasmids containing different regions of the interleukin 1 beta gene and the bacterial chloramphenicol acetyltransferase gene were transfected into human monocytic THP-1 or U937 cells. After treatment with 12-O-tetradecanoylphorbol-13-acetate, which triggers cell differentiation, we have identified an enhancer sequence which mediates the induction of gene activity by 12-O-tetradecanoylphorbol-13-acetate. The enhancer, approximately 180 base pairs long, is located between positions -2982 and -2795 upstream from the transcriptional start site. Further analysis has shown that 132 base pairs immediately upstream from the start site of transcription are sufficient to promote constitutive expression of the gene. Additional promoter elements, located within the first intron, maximize the level of gene expression. Although activated monocytes and macrophages are the main producers of interleukin 1 beta, both the enhancer and the constitutive promoter can function in monocytic cells as well as in nonmonocytic HeLa cells.

Longterm treatment of irritable bowel syndrome with cimetropium bromide: a double blind placebo controlled clinical trial

The aim of this study was to evaluate the efficacy of cimetropium bromide, a new antimuscarinic compound, in relieving symptoms of patients with irritable bowel syndrome over a three month period. Seventy consecutive outpatients were given cimetropium (50 mg tid) or placebo according to a double blind, randomised, parallel groups design. Symptoms were evaluated initially and at monthly intervals up to the end of the study period. One patient receiving placebo withdrew because of treatment failure. Pain score decreased by 40, 66, 85% in the cimetropium group, at the end of the first, second and third months respectively, compared with 26, 32 and 52% reductions among controls (p = 0.0005). At the end of treatment there was a 86% reduction in the number of abdominal pain episodes per day in the cimetropium group compared with 50% in the placebo group (p = 0.001). Constipation and diarrhoea scores decreased by 59 and 49% in the cimetropium treated patients, compared with 37 and 39% in controls, the differences between being not significant. At the end of the study 89% of the patients treated with cimetropium considered themselves as globally improved as opposed to 69% in the placebo group (p = 0.039). The corresponding 95% confidence intervals for the differences between the proportion of improved patients in the two groups were from 11% to 29%. Six patients taking cimetropium complained of slight dry mouth. The results of this study showed that cimetropium bromide is effective in relieving pain in patients with irritable bowel syndrome.

Treatment of chronic erosive gastritis: a double-blind trial of pirenzepine and cimetidine

In a double-blind study, 59 patients with chronic erosive gastritis received 50 mg of pirenzepine twice daily and 55 patients received 400 mg of cimetidine twice daily for six weeks. In both groups, days of pain, of heartburn, and of nausea per week were significantly reduced during treatment (P less than 0.01). After six weeks, 64% of the pirenzepine group and 62% of the cimetidine group were free of symptoms and endoscopy revealed healing of lesions in 78% and 80%, respectively. Differences between groups were not significant.

[Effect of cimetropium bromide in the treatment of colic in the first 3 months of life. Randomized study]

20% of unweaned children aged below three months suffer from so-called gaseous colic. The effectiveness and tolerance of an antimuscarinic drug with high spasmolytic activity on the smooth visceral musculature, cimetropium bromide, has been evaluated, excluding cases of intolerance to cow's milk and other pathologies. 40 random patients of both sexes of average age 4.4 weeks (symptoms lasting for one week with crying fits lasting for more than 90 minutes consecutively, on at least 3 days a week) split into two groups of 20 patients each were studied.

TREATMENT

A) 1.2 mg/kg 1 hour before bottle; B) 2.0 mg/kg 1 hour before bottle. Speedy reduction in the number of crying episodes (Group A: from 2.8 +/- 0.3 to 0.1 +/- 0.1; Group B: from 2.8 +/- 0.4 to 0.6 +/- 0.4; differences n.s.) and in their duration (Group A: 99 min +/- 10 min to 5 min +/- 3 min; Group B: from 121 min +/- 11 min to 15 min +/- 9 min; differences n.s.). The pharmacological treatment was considered: Group A: very good in 75% of cases; Group B: very good in 70% of cases. In Group B 4 episodes of stypsis occurred and these resolved immediately upon suspension of the drug. Given the equal effectiveness and better tolerance, the use of cimetropium bromide is recommended at the lower dosage.

Hepatic lipid peroxidation and aldehyde dehydrogenase activity in alcoholic and non alcoholic liver disease

It has been suggested that lipid peroxidation plays a role in the pathogenesis of chronic alcoholic liver disease (CALD). However, whether or not CALD differs from chronic non alcoholic liver disease (CLD) in lipid peroxidation, is still questionable. Thirty-eight patients affected by CALD and CLD who were matched for age, sex, nutrition and liver function tests (LFTs) and 17 controls (C) took part in this study. The following tests were performed: serum and liver malondialdehyde (MDA) determination by the TBA test, liver total glutathione (GSH) estimate, mitochondrial (ALDH2) and cytosolic (ALDH1) aldehyde dehydrogenase activity determinations. Patients who showed signs of malnutrition were excluded from this study. Serum and hepatic TBA-reactive substances resulted in a slight increase in chronic liver patients compared to controls but did not show any difference between CALD and CLD groups. Liver total glutathione did not show any change. Hepatic ALDH2 activity was significantly (P less than 0.01) higher in CALD than in CLD and control patients whereas ALDH1 did not show any difference. These results suggest that the increased lipid peroxidation in CALD and in CLD is probably secondary to liver damage rather than being the pathogenic factor.

Human interleukin-1 beta gene

We report the nucleotide sequence of the human chromosomal gene which encodes the interleukin-1 beta protein (IL-1 beta). The gene spans a region of 7.5 kb and the coding part is divided into seven exons. Comparison with the homologous mouse gene reveals that the structural organization is conserved through evolution. In addition to this, human and murine IL-1 beta genes show extensive sequence homology within the intervening sequences.

A new restriction fragment length polymorphism in the haptoglobin gene region

Direct gene analysis of the haptoglobin gene region was carried out by Southern blotting using an Hp cDNA as probe. Two types of polymorphism were observed: one due to intragenic duplication, is characterized by a constant fragment length difference of 1700bp observed with several enzymes and by complete correspondence with the protein molecular weight polymorphism; the second type, due to point mutation, was represented by two additional restriction sites for Eco RI and Pst I, with a frequency comparable to that of other genes. These two mutations segregated together in families, suggesting that the recently described Hp related gene is closely linked to the Hp gene. Moreover, they were completely associated with each other. The evolutionary significance of this finding is discussed.

The genome of Bacillus subtilis phage SPP1: structure of an early promoter

The strongest of five 'early' promoters of Bacillus subtilis phage SPP1 was localized in a DNA restriction fragment by analysis of RNA polymerase binding and R-loop formation. The nucleotide sequence of the promoter region was established. The signal structures identified were similar to those recognized by the sigma 55 RNA polymerase of B. subtilis. The promoter precedes an open reading frame with 51 codons. A protein with the Mr predicted from the nucleotide sequence was identified in minicells.

Structure and expression of the human haptoglobin locus

Human genomic clones of the haptoglobin Hp1F and the "haptoglobin related' gene (Hpr) have been isolated. The two genes are adjacent, spanning a region of approximately 21 kb. A comparison of their coding sequences shows that Hpr differs from Hp1F at 28 codons. Northern blot and primer elongation analyses with human liver RNA show that the haptoglobin gene Hp1F appears to be transcribed some 1000-fold less in fetal than in adult liver. In adult liver the amount of Hpr mRNA is at the lower limit of detection, therefore the extent of its expression is at most less than 1000-fold that of the Hp1F gene. No Hpr mRNA can be detected in fetal liver.

Cloning and sequencing of a full length cDNA coding for a human apoferritin H chain: evidence for a multigene family

We have cloned a segment of cDNA from human liver coding for an apoferritin subunit, probably an H chain. Sequence comparison with the available protein sequence shows that our clone corresponds to a ferritin subunit present as a minor species in human spleen and placenta, but as major species in HeLa cells. Northern blot analysis shows the existence of only one band of similar size in human liver, HeLa cells, Daudi lymphoma and Hep3B hepatoma cell lines. In contrast, Southern blot analysis provides evidence for a multigene family.

Cloning and sequencing of a full length cDNA coding for human retinol-binding protein

We have isolated and sequenced a cDNA clone coding for human Retinol Binding Protein. The sequence indicates that Retinol Binding Protein is synthesized as a single polypeptide chain precursor which is then matured to the secreted protein by removal of a leader peptide. Southern and Northern blot analysis suggest that the gene is present in one or few copies per haploid genome and is transcribed in a single mRNA species.

Sequence of human haptoglobin cDNA: evidence that the alpha and beta subunits are coded by the same mRNA

We have isolated and sequenced a cDNA clone coding for human haptoglobin. Our sequence shows that haptoglobin is very likely synthesized as a single polypeptide chain which is then cleaved at an Arg residue to generate its two characteristic alpha and beta subunit. Southern blot analysis suggests that there are at least two copies of the haptoglobin gene per haploid genome.

Plasmid transformation in Bacillus subtilis. The significance of partial homology between plasmid and recipient cell DNAs

A series of hybrid plasmids consisting of pC194 or pUB112 and B. subtilis DNA were constructed. In contrast to plasmid pC194, purified monomeric forms of such plasmids were active in transformation, provided the recipient cells were recombination proficient. Similarly the monomers of pC194 derived plasmids, containing bacteriophage phi 105 DNA were able to transform phi 105 lysogenic but not nonlysogenic cells. From the results it is concluded that the presence of DNA/DNA homology between chromosomal DNA of the recipient cell and part of the hybrid plasmids used is a sufficient condition to endow monomeric plasmids with transforming activity.

Plasmid transformation in Bacillus subtilis. Alterations introduced into the recipient-homologous DNA of hybrid plasmids can be corrected in transformation

Various alterations (deletions, additions, inversions) were introduced into portions of pC194/B. subtilis or pC194/phi 105 hybrid plasmid molecules which are homologous to the DNA of recipients in transformation. These plasmids are stably maintained in transformations of recombination deficient cells. In transformations of recombination proficient cells, they can be corrected to those plasmid forms into which the alterations were originally introduced. This correction is most pronounced when transformations are performed with monomeric ccc forms of hybrid plasmids. It is suggested that correction is a consequence of mismatch repair occurring in the synapsis of homologous portions of plasmid and resident DNAs.