Neisseria meningitidis serogroup A capsular polysaccharide (MenA CPS) consists of (1 → 6)-2-aceta... more Neisseria meningitidis serogroup A capsular polysaccharide (MenA CPS) consists of (1 → 6)-2-acetamido-2-deoxy-α-D-mannopyranosyl phosphate repeating units, O-acetylated at position C3 or C4. Glycomimetics appear attractive to overcome the CPS intrinsic lability in physiological media, due to cleavage of the phosphodiester bridge, and to develop a stable vaccine with longer shelf life in liquid formulation. Here, we generate a series of non-acetylated carbaMenA oligomers which are proven more stable than the CPS. An octamer (DP8) inhibits the binding of a MenA specific bactericidal mAb and polyclonal serum to the CPS, and is selected for further in vivo testing. However, its CRM197 conjugate raises murine antibodies towards the non-acetylated CPS backbone, but not the natural acetylated form. Accordingly, random O-acetylation of the DP8 is performed, resulting in a structure (Ac-carbaMenA) showing improved inhibition of anti-MenA CPS antibody binding and, after conjugation to CRM197,...
Most pre-clinical studies assess vaccine effectiveness in single-pathogen infection models. This... more Most pre-clinical studies assess vaccine effectiveness in single-pathogen infection models. This is unrealistic given that humans are continuously exposed to different commensals and pathogens in sequential and mixed infections. Accordingly, complications from secondary bacterial infection are a leading cause of influenza-associated morbidity and mortality. New vaccination strategies are needed to control infections on simultaneous fronts. We compared different anti-influenza vaccines for their protective potential in a model of viral infection with bacterial superinfection. Mice were immunized with H1N1/A/California/7/2009 subunit vaccines, formulated with different adjuvants inducing either Th1- [MF59+CpG], Th2- [MF59] or Th17- [LTK63] prone immune responses, and were sequentially challenged with mouse-adapted influenza virus H1N1/A/Puerto Rico/8/1934 and Staphylococcus aureus USA300, a clonotype emerging as a leading contributor in post-influenza pneumonia in humans. Unadjuvan...
Seasonal influenza is a vaccine-preventable disease that remains a major health problem worldwide... more Seasonal influenza is a vaccine-preventable disease that remains a major health problem worldwide, especially in immunocompromised populations. The impact of influenza disease is even greater when strains drift, and influenza pandemics can result when animal-derived influenza virus strains combine with seasonal strains. In this study, we used the SAM technology and characterized the immunogenicity and efficacy of a self-amplifying mRNA expressing influenza virus hemagglutinin (HA) antigen [SAM(HA)] formulated with a novel oil-in-water cationic nanoemulsion. We demonstrated that SAM(HA) was immunogenic in ferrets and facilitated containment of viral replication in the upper respiratory tract of influenza virus-infected animals. In mice, SAM(HA) induced potent functional neutralizing antibody and cellular immune responses, characterized by HA-specific CD4 T helper 1 and CD8 cytotoxic T cells. Furthermore, mice immunized with SAM(HA) derived from the influenza A virus A/California/7/20...
Bacterial infections caused by Group A Streptococcus (GAS) are a serious health care concern that... more Bacterial infections caused by Group A Streptococcus (GAS) are a serious health care concern that currently cannot be prevented by vaccination. The GAS cell-wall polysaccharide (GAS-PS) is an attractive vaccine candidate due to its constant expression pattern on different bacterial strains and protective properties of anti-GASPS antibodies. Here we report for the first time the immunoprotective efficacy of glycoconjugates with synthetic GAS oligosaccharides as compared to those containing the native GASPS. A series of hexa-and dodecasaccharides based on the GASPS structure were prepared by chemical synthesis and conjugated to CRM 197. When tested in mice, the conjugates containing the synthetic oligosaccharides conferred levels of immunoprotection comparable to those elicited by the native conjugate. Antisera from immunized rabbits promoted phagocytosis of encapsulated GAS strains. Furthermore we discuss variables that might correlate with glycoconjugate immunogenicity and demonstrate the potential of the synthetic approach that benefits from increased antigen purity and facilitated manufacturing.
Pandemic H1N1 influenza vaccine antigens are currently being manufactured. The MF59 adjuvant has ... more Pandemic H1N1 influenza vaccine antigens are currently being manufactured. The MF59 adjuvant has an established safety profile in humans and a proven ability to increase responses to some influenza vaccines in humans. To inform initial decisions on the use of these vaccine components to protect human populations, we have immunized mice with MF59-adjuvanted or non-adjuvanted pandemic influenza vaccine. Immunizing unprimed mice with a single dose of MF59-adjuvanted vaccine elicits functional antibody titers equivalent to those associated with protection of humans from seasonal influenza. Without adjuvant, two doses are required for a robust antibody response. Unadjuvanted vaccines with 0.5 and 1 microgram of antigen elicit equivalent titers. These data support including MF59 in pandemic flu vaccines to rapidly protect young adults and children, who may have little or no previous exposure to influenza infection or immunization. 10
The effectiveness of vaccines depends on the age and immunocompetence of the vaccinee. Convention... more The effectiveness of vaccines depends on the age and immunocompetence of the vaccinee. Conventional non-adjuvanted influenza vaccines are suboptimal in the elderly and vaccines with improved ability to prevent influenza are required. The TLR4 agonist E6020, either given alone or co-delivered with MF59, was evaluated and compared to MF59 and the TLR9 agonist CpG. Its ability to enhance antibody titres and to modulate the quality of the immune response to a subunit influenza vaccine was investigated. Mice were immunized with either antigens alone, with MF59 or with the TLR agonists alone, or with a combination thereof. Serum samples were assayed for IgG antibody titres and hemagglutination inhibition (HI) titres. Th1/Th2 type responses were determined by titrating IgG subclasses in serum samples and by T-cell cytokine responses in splenocytes. MF59 was the best single adjuvant inducing HI and T-cell responses in comparison to all alternatives. The co-delivery of E6020 or CpG with MF59 did not further increase antibody titres however shifted towards a more Th1 based immune response. Combining adjuvants like E6020 and MF59 allowed a finer tuning of the immune response towards a particular Th bias, thus have significant implications for the development of improved influenza vaccines.
A competitive ELISA method is described for the measurement of total antibodies to the capsular p... more A competitive ELISA method is described for the measurement of total antibodies to the capsular polysaccharide ofHaemophilus influenzae type b (HibCPS) in human sera. The competitive method showed an excellent correlation to the radioantigen binding assay (RABA, or Farr assay) and improved correlation of sera with low titers with respect to the more conventional noncompetitive method. Overestimation of samples in the low concentration range was no longer observed with the competitive ELISA method. The free HibCPS competition allowed us to eliminate the day-to-day background variation typical of some sera; thus, only values representing the true anti-HibCPS response were determined. The use of precoated microplates, which could be stored up to 8 months, greatly improved the speed of the procedure. An overall correlation coefficient of 0.9660 was found when 407 serum samples with a wide variety of anti-HibCPS antibody levels were tested with the competitive ELISA and RABA. The regress...
In ELISA, ligand is commonly adsorbed to the plastic surface through non-covalent bonds between t... more In ELISA, ligand is commonly adsorbed to the plastic surface through non-covalent bonds between the hydrophobic regions of the ligand and the plastic surface. Thus, all the reactions occur in a heterogeneous phase, with some reactants in solution, and some immobilized. As a result, the diffusion constant of immobilized reagents is phase, aimed at speeding up ELISA procedure especially to easily adapt it to robotic systems. Conventional tests usually may take up to 5 hours. Our "rapid ELISA" approach considerably reduces this time to less than 30 minutes allowing the method to be more suitable for automation. The rapid ELISA has been set up to analyze samples coming from animal studies for vaccine development Neisseria meningitidis used to detect a wide range of antibodies raised against a wide range of antigens.
Neisseria meningitidis serogroup A capsular polysaccharide (MenA CPS) consists of (1 → 6)-2-aceta... more Neisseria meningitidis serogroup A capsular polysaccharide (MenA CPS) consists of (1 → 6)-2-acetamido-2-deoxy-α-D-mannopyranosyl phosphate repeating units, O-acetylated at position C3 or C4. Glycomimetics appear attractive to overcome the CPS intrinsic lability in physiological media, due to cleavage of the phosphodiester bridge, and to develop a stable vaccine with longer shelf life in liquid formulation. Here, we generate a series of non-acetylated carbaMenA oligomers which are proven more stable than the CPS. An octamer (DP8) inhibits the binding of a MenA specific bactericidal mAb and polyclonal serum to the CPS, and is selected for further in vivo testing. However, its CRM197 conjugate raises murine antibodies towards the non-acetylated CPS backbone, but not the natural acetylated form. Accordingly, random O-acetylation of the DP8 is performed, resulting in a structure (Ac-carbaMenA) showing improved inhibition of anti-MenA CPS antibody binding and, after conjugation to CRM197,...
Most pre-clinical studies assess vaccine effectiveness in single-pathogen infection models. This... more Most pre-clinical studies assess vaccine effectiveness in single-pathogen infection models. This is unrealistic given that humans are continuously exposed to different commensals and pathogens in sequential and mixed infections. Accordingly, complications from secondary bacterial infection are a leading cause of influenza-associated morbidity and mortality. New vaccination strategies are needed to control infections on simultaneous fronts. We compared different anti-influenza vaccines for their protective potential in a model of viral infection with bacterial superinfection. Mice were immunized with H1N1/A/California/7/2009 subunit vaccines, formulated with different adjuvants inducing either Th1- [MF59+CpG], Th2- [MF59] or Th17- [LTK63] prone immune responses, and were sequentially challenged with mouse-adapted influenza virus H1N1/A/Puerto Rico/8/1934 and Staphylococcus aureus USA300, a clonotype emerging as a leading contributor in post-influenza pneumonia in humans. Unadjuvan...
Seasonal influenza is a vaccine-preventable disease that remains a major health problem worldwide... more Seasonal influenza is a vaccine-preventable disease that remains a major health problem worldwide, especially in immunocompromised populations. The impact of influenza disease is even greater when strains drift, and influenza pandemics can result when animal-derived influenza virus strains combine with seasonal strains. In this study, we used the SAM technology and characterized the immunogenicity and efficacy of a self-amplifying mRNA expressing influenza virus hemagglutinin (HA) antigen [SAM(HA)] formulated with a novel oil-in-water cationic nanoemulsion. We demonstrated that SAM(HA) was immunogenic in ferrets and facilitated containment of viral replication in the upper respiratory tract of influenza virus-infected animals. In mice, SAM(HA) induced potent functional neutralizing antibody and cellular immune responses, characterized by HA-specific CD4 T helper 1 and CD8 cytotoxic T cells. Furthermore, mice immunized with SAM(HA) derived from the influenza A virus A/California/7/20...
Bacterial infections caused by Group A Streptococcus (GAS) are a serious health care concern that... more Bacterial infections caused by Group A Streptococcus (GAS) are a serious health care concern that currently cannot be prevented by vaccination. The GAS cell-wall polysaccharide (GAS-PS) is an attractive vaccine candidate due to its constant expression pattern on different bacterial strains and protective properties of anti-GASPS antibodies. Here we report for the first time the immunoprotective efficacy of glycoconjugates with synthetic GAS oligosaccharides as compared to those containing the native GASPS. A series of hexa-and dodecasaccharides based on the GASPS structure were prepared by chemical synthesis and conjugated to CRM 197. When tested in mice, the conjugates containing the synthetic oligosaccharides conferred levels of immunoprotection comparable to those elicited by the native conjugate. Antisera from immunized rabbits promoted phagocytosis of encapsulated GAS strains. Furthermore we discuss variables that might correlate with glycoconjugate immunogenicity and demonstrate the potential of the synthetic approach that benefits from increased antigen purity and facilitated manufacturing.
Pandemic H1N1 influenza vaccine antigens are currently being manufactured. The MF59 adjuvant has ... more Pandemic H1N1 influenza vaccine antigens are currently being manufactured. The MF59 adjuvant has an established safety profile in humans and a proven ability to increase responses to some influenza vaccines in humans. To inform initial decisions on the use of these vaccine components to protect human populations, we have immunized mice with MF59-adjuvanted or non-adjuvanted pandemic influenza vaccine. Immunizing unprimed mice with a single dose of MF59-adjuvanted vaccine elicits functional antibody titers equivalent to those associated with protection of humans from seasonal influenza. Without adjuvant, two doses are required for a robust antibody response. Unadjuvanted vaccines with 0.5 and 1 microgram of antigen elicit equivalent titers. These data support including MF59 in pandemic flu vaccines to rapidly protect young adults and children, who may have little or no previous exposure to influenza infection or immunization. 10
The effectiveness of vaccines depends on the age and immunocompetence of the vaccinee. Convention... more The effectiveness of vaccines depends on the age and immunocompetence of the vaccinee. Conventional non-adjuvanted influenza vaccines are suboptimal in the elderly and vaccines with improved ability to prevent influenza are required. The TLR4 agonist E6020, either given alone or co-delivered with MF59, was evaluated and compared to MF59 and the TLR9 agonist CpG. Its ability to enhance antibody titres and to modulate the quality of the immune response to a subunit influenza vaccine was investigated. Mice were immunized with either antigens alone, with MF59 or with the TLR agonists alone, or with a combination thereof. Serum samples were assayed for IgG antibody titres and hemagglutination inhibition (HI) titres. Th1/Th2 type responses were determined by titrating IgG subclasses in serum samples and by T-cell cytokine responses in splenocytes. MF59 was the best single adjuvant inducing HI and T-cell responses in comparison to all alternatives. The co-delivery of E6020 or CpG with MF59 did not further increase antibody titres however shifted towards a more Th1 based immune response. Combining adjuvants like E6020 and MF59 allowed a finer tuning of the immune response towards a particular Th bias, thus have significant implications for the development of improved influenza vaccines.
A competitive ELISA method is described for the measurement of total antibodies to the capsular p... more A competitive ELISA method is described for the measurement of total antibodies to the capsular polysaccharide ofHaemophilus influenzae type b (HibCPS) in human sera. The competitive method showed an excellent correlation to the radioantigen binding assay (RABA, or Farr assay) and improved correlation of sera with low titers with respect to the more conventional noncompetitive method. Overestimation of samples in the low concentration range was no longer observed with the competitive ELISA method. The free HibCPS competition allowed us to eliminate the day-to-day background variation typical of some sera; thus, only values representing the true anti-HibCPS response were determined. The use of precoated microplates, which could be stored up to 8 months, greatly improved the speed of the procedure. An overall correlation coefficient of 0.9660 was found when 407 serum samples with a wide variety of anti-HibCPS antibody levels were tested with the competitive ELISA and RABA. The regress...
In ELISA, ligand is commonly adsorbed to the plastic surface through non-covalent bonds between t... more In ELISA, ligand is commonly adsorbed to the plastic surface through non-covalent bonds between the hydrophobic regions of the ligand and the plastic surface. Thus, all the reactions occur in a heterogeneous phase, with some reactants in solution, and some immobilized. As a result, the diffusion constant of immobilized reagents is phase, aimed at speeding up ELISA procedure especially to easily adapt it to robotic systems. Conventional tests usually may take up to 5 hours. Our "rapid ELISA" approach considerably reduces this time to less than 30 minutes allowing the method to be more suitable for automation. The rapid ELISA has been set up to analyze samples coming from animal studies for vaccine development Neisseria meningitidis used to detect a wide range of antibodies raised against a wide range of antigens.
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Papers by Daniele Casini