Systemic Alanine Glyoxylate Aminotransferase mRNA Improves Glyoxylate Metabolism in a Mouse Model of Primary Hyperoxaluria Type 1.

Primary Hyperoxaluria Type 1 (PH1) is an autosomal recessive disorder of glyoxylate metabolism. Loss of alanine glyoxylate aminotransferase (AGT) function to convert intermediate metabolite glyoxylate to glycine causes the accumulation and reduction of glyoxylate to glycolate, which eventually is oxidized to oxalate. Excess oxalate in PH1 patients leads to the formation and deposition of calcium oxalate crystals in the kidney and urinary tract. Oxalate crystal deposition causes a decline in renal function, systemic oxalosis, and eventually end-stage renal disease and premature death. mRNA-based therapies are a new class of drugs that work by replacing the missing enzyme. mRNA encoding AGT has the potential to restore normal glyoxylate to glycine metabolism, thus preventing the buildup of calcium oxalate in various organs. Panels of codon-optimized AGT mRNA constructs were screened in vitro and in wild-type mice for the production of a functional AGT enzyme. Two human constructs, wild-type and engineered AGT (RHEAM), were tested in Agxt-/- mice. Repeat dosing in Agxt-/- mice resulted in a 40% reduction in urinary oxalate, suggesting therapeutic benefit. These studies suggest that mRNA encoding AGT led to increased expression and activity of the AGT enzyme in liver that translated into decrease in urinary oxalate levels. Taken together, our data indicate that AGT mRNA may have the potential to be developed into a therapeutic for PH1.

Quantitative Systems Pharmacology Model of hUGT1A1-modRNA Encoding for the UGT1A1 Enzyme to Treat Crigler-Najjar Syndrome Type 1.

Crigler-Najjar syndrome type 1 (CN1) is an autosomal recessive disease caused by a marked decrease in uridine-diphosphate-glucuronosyltransferase (UGT1A1) enzyme activity. Delivery of hUGT1A1-modRNA (a modified messenger RNA encoding for UGT1A1) as a lipid nanoparticle is anticipated to restore hepatic expression of UGT1A1, allowing normal glucuronidation and clearance of bilirubin in patients. To support translation from preclinical to clinical studies, and first-in-human studies, a quantitative systems pharmacology (QSP) model was developed. The QSP model was calibrated to plasma and liver mRNA, and total serum bilirubin in Gunn rats, an animal model of CN1. This QSP model adequately captured the observed plasma and liver biomarker behavior across a range of doses and dose regimens in Gunn rats. First-in-human dose projections made using the translated model indicated that 0.5 mg/kg Q4W dose should provide a clinically meaningful and sustained reduction of >5 mg/dL in total bilirubin levels.

Design and preclinical characterization of ALXN1210: A novel anti-C5 antibody with extended duration of action.

Eculizumab, a monoclonal antibody (mAb) directed against complement protein C5, is considered to be the current standard of care for patients with paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome. This study describes the generation and preclinical attributes of ALXN1210, a new long-acting anti-C5 mAb, obtained through select modifications to eculizumab to both largely abolish target-mediated drug disposition (TMDD) and increase recycling efficiency via the neonatal Fc receptor (FcRn). To attenuate the effect of TMDD on plasma terminal half-life (t1/2), histidine substitutions were engineered into the complementarity-determining regions of eculizumab to enhance the dissociation rate of the mAb:C5 complex in the acidic early endosome relative to the slightly basic pH of blood. Antibody variants with optimal pH-dependent binding to C5 exhibited little to no TMDD in mice in the presence of human C5. To further enhance the efficiency of FcRn-mediated recycling of the antibody, two additional substitutions were introduced to increase affinity for human FcRn. These substitutions yielded an additional doubling of the t½ of surrogate anti-mouse C5 antibodies with reduced TMDD in transgenic mice expressing the human FcRn. In conclusion, ALXN1210 is a promising new therapeutic candidate currently in clinical development for treatment of patients with PNH and atypical hemolytic uremic syndrome.

Leveraging Rational Protein Engineering to Improve mRNA Therapeutics.

Messenger RNA (mRNA) is a promising new class of therapeutics that has potential for treatment of diseases in fields such as immunology, oncology, vaccines, and inborn errors of metabolism. mRNA therapy has several advantages over DNA-based gene therapy, including the lack of the need for nuclear import and transcription, as well as limited possibility of genomic integration. One drawback of mRNA therapy, especially in cases such as metabolic disorders where repeated dosing will be necessary, is the relatively short in vivo half-life of mRNA (∼6-12 h). We hypothesize that protein engineering designed to improve translation, yielding longer-lasting protein, or modifications that would increase enzymatic activity would be helpful in alleviating this issue. In this study, we present two examples where sequence engineering improved the expression and duration, as well as enzymatic activity of target proteins in vitro. We then confirmed these findings in wild-type mice. This work shows that rational engineering of proteins can lead to improved therapies in vivo.

Efficacy of Targeted Complement Inhibition in Experimental C3 Glomerulopathy.

C3 glomerulopathy refers to renal disorders characterized by abnormal accumulation of C3 within the kidney, commonly along the glomerular basement membrane (GBM). C3 glomerulopathy is associated with complement alternative pathway dysregulation, which includes functional defects in complement regulator factor H (FH). There is no effective treatment for C3 glomerulopathy. We investigated the efficacy of a recombinant mouse protein composed of domains from complement receptor 2 (CR2) and FH (CR2-FH) in two models of C3 glomerulopathy with either preexisting or triggered C3 deposition along the GBM. FH-deficient mice spontaneously develop renal pathology associated with abnormal C3 accumulation along the GBM and secondary plasma C3 deficiency. CR2-FH partially restored plasma C3 levels in FH-deficient mice 2 hours after intravenous injection. CR2-FH specifically targeted glomerular C3 deposits, reduced the linear C3 reactivity assessed with anti-C3 and anti-C3b/iC3b/C3c antibodies, and prevented further spontaneous accumulation of C3 fragments along the GBM. Reduction in glomerular C3d and C9/C5b-9 reactivity was observed after daily administration of CR2-FH for 1 week. In a second mouse model with combined deficiency of FH and complement factor I, CR2-FH prevented de novo C3 deposition along the GBM. These data show that CR2-FH protects the GBM from both spontaneous and triggered C3 deposition in vivo and indicate that this approach should be tested in C3 glomerulopathy.

Escherichia coli isolate for studying colonization of the mouse intestine and its application to two-component signaling knockouts.

The biology of Escherichia coli in its primary niche, the animal intestinal tract, is remarkably unexplored. Studies with the streptomycin-treated mouse model have produced important insights into the metabolic requirements for Escherichia coli to colonize mice. However, we still know relatively little about the physiology of this bacterium growing in the complex environment of an intestine that is permissive for the growth of competing flora. We have developed a system for studying colonization using an E. coli strain, MP1, isolated from a mouse. MP1 is genetically tractable and does not require continuous antibiotic treatment for stable colonization. As an application of this system, we separately knocked out each two-component system response regulator in MP1 and performed competitions against the wild-type strain. We found that only three response regulators, ArcA, CpxR, and RcsB, produce strong colonization defects, suggesting that in addition to anaerobiosis, adaptation to cell envelope stress is a critical requirement for E. coli colonization of the mouse intestine. We also show that the response regulator OmpR, which had previously been hypothesized to be important for adaptation between in vivo and ex vivo environments, is not required for MP1 colonization due to the presence of a third major porin.

Role of complement activation in obliterative bronchiolitis post-lung transplantation.

Obliterative bronchiolitis (OB) post-lung transplantation involves IL-17-regulated autoimmunity to type V collagen and alloimmunity, which could be enhanced by complement activation. However, the specific role of complement activation in lung allograft pathology, IL-17 production, and OB is unknown. The current study examines the role of complement activation in OB. Complement-regulatory protein (CRP) (CD55, CD46, complement receptor 1-related protein y/CD46) expression was downregulated in human and murine OB; and C3a, a marker of complement activation, was upregulated locally. IL-17 differentially suppressed complement receptor 1-related protein y expression in airway epithelial cells in vitro. Neutralizing IL-17 recovered CRP expression in murine lung allografts and decreased local C3a production. Exogenous C3a enhanced IL-17 production from alloantigen- or autoantigen (type V collagen)-reactive lymphocytes. Systemically neutralizing C5 abrogated the development of OB, reduced acute rejection severity, lowered systemic and local levels of C3a and C5a, recovered CRP expression, and diminished systemic IL-17 and IL-6 levels. These data indicated that OB induction is in part complement dependent due to IL-17-mediated downregulation of CRPs on airway epithelium. C3a and IL-17 are part of a feed-forward loop that may enhance CRP downregulation, suggesting that complement blockade could be a therapeutic strategy for OB.

F1C fimbriae play an important role in biofilm formation and intestinal colonization by the Escherichia coli commensal strain Nissle 1917.

Bacterial biofilm formation is thought to enhance survival in natural environments and during interaction with hosts. A robust colonizer of the human gastrointestinal tract, Escherichia coli Nissle 1917, is widely employed in probiotic therapy. In this study, we performed a genetic screen to identify genes that are involved in Nissle biofilm formation. We found that F1C fimbriae are required for biofilm formation on an inert surface. In addition, these structures are also important for adherence to epithelial cells and persistence in infant mouse colonization. The data suggest a possible connection between Nissle biofilm formation and the survival of this commensal within the host. Further study of the requirements for robust biofilm formation may improve the therapeutic efficacy of Nissle 1917.

Functional and immunological characterization of a natural polymorphic variant of a heat-labile toxin (LT-I) produced by enterotoxigenic Escherichia coli (ETEC).

Heat-labile toxins (LT) encompass at least 16 natural polymorphic toxin variants expressed by wild-type enterotoxigenic Escherichia coli (ETEC) strains isolated from human beings, but only one specific form, produced by the reference ETEC H10407 strain (LT1), has been intensively studied either as a virulence-associated factor or as a mucosal/transcutaneous adjuvant. In the present study, we carried out a biological/immunological characterization of a natural LT variant (LT2) with four polymorphic sites at the A subunit (S190L, G196D, K213E, and S224T) and one at the B subunit (T75A). The results indicated that purified LT2, in comparison with LT1, displayed similar in vitro toxic activities (adenosine 3',5'-cyclic monophosphate accumulation) on mammalian cells and in vivo immunogenicity following delivery via the oral route. Nonetheless, the LT2 variant showed increased adjuvant action to ovalbumin when delivered to mice via the transcutaneous route while antibodies raised in mice immunized with LT2 displayed enhanced affinity and neutralization activity to LT1 and LT2. Taken together, the results indicate that the two most frequent LT polymorphic forms expressed by wild ETEC strains share similar biological features, but differ with regard to their immunological properties.

Capsular antigen fraction 1 and Pla modulate the susceptibility of Yersinia pestis to pulmonary antimicrobial peptides such as cathelicidin.

Inhaled Yersinia pestis produces a severe primary pneumonia known as pneumonic plague, which is contagious and highly lethal to humans and animals. In this study, we first determined the susceptibility of Y. pestis KIM6 to antimicrobial molecules of the airways. We found that (i) rat bronchoalveolar lavage fluid (rBALF) effectively killed KIM6 cells growing at 37 degrees C; (ii) the antibacterial components of rBALF were small peptides (<10 kDa) that included two cationic antimicrobial peptides (CAMPs), the rat cathelicidin rCRAMP, and beta-defensin RBD-1; (iii) the human cathelicidin LL-37 killed KIM6 cells as well as rBALF did; and (iv) the bactericidal property of LL-37 was synergistically amplified by human beta-defensin 1, another constitutively expressed pulmonary CAMP. Second, the effects of three major surface proteins of Y. pestis, namely, the capsular antigen fraction 1 (F1), the pH 6 antigen (Psa fimbriae), and the outer membrane protease Pla, on the bactericidal effect of the antimicrobial rBALF peptides was determined with corresponding deletion mutants. We showed that (i) a Y. pestis psa mutant was only slightly more susceptible to rBALF than the parental KIM6 strain, (ii) a caf (F1 gene) mutant and a caf psa mutant were resistant to rBALF or LL-37, (iii) a caf pla mutant was as susceptible to the effect of rBALF or LL-37 as KIM6 was (caf+ pla+), and (iv) only the single caf mutant (pla+), but not KIM6 or the caf pla double mutant, degraded LL-37. The activity of Pla toward LL-37 was confirmed with pla mutants carrying a single-residue substitution affecting plasminogen cleavage. Taken together, our data indicated that Pla might act as a virulence factor not only by processing plasminogen but also by inactivating CAMPs, particularly when F1 is not expressed.

Evaluation of experimental conditions for quantification of LT produced by human derived enterotoxigenic Escherichia coli strains

The heat-labile toxin (LT) is a key virulence-associated factor associated with the non-invasive secretory diarrhea caused by enterotoxigenic Escherichia coli (ETEC) strains either in humans or domestic animals. Several LT detection methods have been reported but quantification of the toxin produced by wild-type ETEC strains is usually performed by the GM1 ganglyoside enzyme-linked immunosorbent assay (GM1 ELISA). In this study we conducted the optimization of an alternative LT-quantification method, the antibody-capture ELISA (cELISA). Detailed analysis of the appropriate dilutions of capture and detecting LT-specific antibodies significantly improved the sensitivity of the method. Additionally, testing of different LT extraction techniques indicated that sonic disruption of the bacterial cells enhanced LT recovery yields, in contrast to the usual procedure based on addition of polymyxin B to the culture medium as well as extraction methods based on chloroform or Triton X-100. Moreover, the present data indicate that performance of the LT extraction method based on polymyxin B treatment can vary among wild ETEC strains.

A toxina termo-lábil (LT) é um fator de virulência associado à diarréia secretora não invasiva causada por linhagens de Escherichia coli enterotoxigênica (ETEC) em humanos ou animais domésticos. Diversos métodos de detecção de LT foram descritos na literatura, no entanto, a quantificação da toxina produzida por linhagens selvagens de ETEC é geralmente realizada por ensaio imunoenzimático com o gangliosídeo GM-1 (GM-1 ELISA). Neste estudo, conduzimos uma otimização experimental de um método alternativo de quantificação de LT, o ELISA de captura (cELISA). Análise detalhada de diluições apropriadas dos anticorpos LT específicos de captura e detecção melhorou significantemente a sensibilidade do método. Em adição, testes com diferentes técnicas de extração de LT indicaram que a ruptura das células por ultra-som, mas não o tratamento com polimixina B, clorofórmio ou Triton X-100, aumentou o rendimento da recuperação de LT. Além disto, os dados apresentados demonstram que o desempenho do método de extração de LT baseado no tratamento com polimixina B pode variar entre linhagens selvagens de ETEC.

Adjuvant requirement for successful immunization with recombinant derivatives of Plasmodium vivax merozoite surface protein-1 delivered via the intranasal route.

Recently, we generated two bacterial recombinant proteins expressing 89 amino acids of the C-terminal domain of the Plasmodium vivax merozoite surface protein-1 and the hexa-histidine tag (His6MSP1(19)). One of these recombinant proteins contained also the amino acid sequence of the universal pan allelic T-cell epitope (His6MSP1(19)-PADRE). In the present study, we evaluated the immunogenic properties of these antigens when administered via the intra-nasal route in the presence of distinct adjuvant formulations. We found that C57BL/6 mice immunized with either recombinant proteins in the presence of the adjuvants cholera toxin (CT) or the Escherichia coli heat labile toxin (LT) developed high and long lasting titers of specific serum antibodies. The induced immune responses reached maximum levels after three immunizing doses with a prevailing IgG1 subclass response. In contrast, mice immunized by intranasal route with His6MSP1(19)-PADRE in the presence of the synthetic oligonucleotides adjuvant CpG ODN 1826 developed lower antibody titers but when combined to CT, CpG addition resulted in enhanced IgG responses characterized by lower IgG1 levels. Considering the limitations of antigens formulations that can be used in humans, mucosal adjuvants can be a reliable alternative for the development of new strategies of immunization using recombinant proteins of P. vivax.

Adjuvant requirement for successful immunization with recombinant derivatives of Plasmodium vivax merozoite surface protein-1 delivered via the intranasal route

Recently, we generated two bacterial recombinant proteins expressing 89 amino acids of the C-terminal domain of the Plasmodium vivax merozoite surface protein-1 and the hexa-histidine tag (His6MSP1(19)). One of these recombinant proteins contained also the amino acid sequence of the universal pan allelic T-cell epitope (His6MSP1(19)-PADRE). In the present study, we evaluated the immunogenic properties of these antigens when administered via the intra-nasal route in the presence of distinct adjuvant formulations. We found that C57BL/6 mice immunized with either recombinant proteins in the presence of the adjuvants cholera toxin (CT) or the Escherichia coli heat labile toxin (LT) developed high and long lasting titers of specific serum antibodies. The induced immune responses reached maximum levels after three immunizing doses with a prevailing IgG1 subclass response. In contrast, mice immunized by intranasal route with His6MSP1(19)-PADRE in the presence of the synthetic oligonucleotides adjuvant CpG ODN 1826 developed lower antibody titers but when combined to CT, CpG addition resulted in enhanced IgG responses characterized by lower IgG1 levels. Considering the limitations of antigens formulations that can be used in humans, mucosal adjuvants can be a reliable alternative for the development of new strategies of immunization using recombinant proteins of P. vivax.

Adhesin-dependent binding and uptake of Salmonella enterica serovar Typhimurium by dendritic cells.

Salmonella enterica serovar Typhimurium can be internalized by immature dendritic cells (DCs). The interacting host and bacterial molecules initiating this process remain uncharacterized. The objective of this study was to investigate whether specific fimbriae are involved in the early step of binding and uptake of Salmonella by DCs. Type 1 fimbriated S. enterica serovar Typhimurium or recombinant Escherichia coli expressing the type 1 fimbriae showed a significantly greater ability to attach to murine bone-marrow-derived DCs than non-fimbriated bacteria. The FimH adhesin was required for efficient interactions with DCs, since fimbriated fimH mutants were impaired in both binding and internalization. Finally, the internalization involved a FimH-dependent process but did not require sipB, a gene essential for Salmonella-mediated invasion of mammalian epithelial cells. Collectively, these data suggest that the bacterial interaction of DCs through the type 1 fimbrial adhesin FimH is sufficient to target S. enterica serovar Typhimurium for cellular uptake.

Effects of Psa and F1 on the adhesive and invasive interactions of Yersinia pestis with human respiratory tract epithelial cells.

Yersinia pestis, the causative agent of plague, expresses the Psa fimbriae (pH 6 antigen) in vitro and in vivo. To evaluate the potential virulence properties of Psa for pneumonic plague, an Escherichia coli strain expressing Psa was engineered and shown to adhere to three types of human respiratory tract epithelial cells. Psa binding specificity was confirmed with Psa-coated polystyrene beads and by inhibition assays. Individual Y. pestis cells were found to be able to express the capsular antigen fraction 1 (F1) concomitantly with Psa on their surface when analyzed by flow cytometry. To better evaluate the separate effects of F1 and Psa on the adhesive and invasive properties of Y. pestis, isogenic Deltacaf (F1 genes), Deltapsa, and Deltacaf Deltapsa mutants were constructed and studied with the three respiratory tract epithelial cells. The Deltapsa mutant bound significantly less to all three epithelial cells compared to the parental wild-type strain and the Deltacaf and Deltacaf Deltapsa mutants, indicating that Psa acts as an adhesin for respiratory tract epithelial cells. An antiadhesive effect of F1 was clearly detectable only in the absence of Psa, underlining the dominance of the Psa+ phenotype. Both F1 and Psa inhibited the intracellular uptake of Y. pestis. Thus, F1 inhibits bacterial uptake by inhibiting bacterial adhesion to epithelial cells, whereas Psa seems to block bacterial uptake by interacting with a host receptor that doesn't direct internalization. The Deltacaf Deltapsa double mutant bound and invaded all three epithelial cell types well, revealing the presence of an undefined adhesin(s) and invasin(s).

Production and release of heat-labile toxin by wild-type human-derived enterotoxigenic Escherichia coli.

Production and release of heat-labile toxin (LT) by wild-type enterotoxigenic Escherichia coli (ETEC) strains, isolated from diarrheic and asymptomatic Brazilian children, was studied under in vitro and in vivo conditions. Based on a set of 26 genetically diverse LT(+) enterotoxigenic E. coli strains, cell-bound LT concentrations varied from 49.8 to 2415 ng mL(-1). The amounts of toxin released in culture supernatants ranged from 0% to 50% of the total synthesized toxin. The amount of LT associated with secreted membrane vesicles represented <5% of the total toxin detected in culture supernatants. ETEC strains secreting higher amounts of LT, but not those producing high intracellular levels of cell-bound toxin, elicited enhanced fluid accumulation in tied rabbit ileal loops, suggesting that the strain-specific differences in production and secretion of LT correlates with symptoms induced in vivo. However, no clear correlation was established between the ability to produce and secrete LT and the clinical symptoms of the infected individuals. The present results indicate that production and release of LT by wild-type human-derived ETEC strains are heterogeneous traits under both in vitro and in vivo growth conditions and may impact the clinical outcomes of infected individuals.