title: Anti-Group B Streptococcus Glycan-Conjugate Vaccines Using Pilus Protein GBS80 As Carrier and Antigen: Comparing Lysine and Tyrosine-directed Conjugation.
abstract: Gram-positive Streptococcus agalactiae or group B Streptococcus (GBS) is a leading cause of invasive infections in pregnant women, newborns, and elderly people. Vaccination of pregnant women represents the best strategy for prevention of neonatal disease, and GBS polysaccharide-based conjugate vaccines are currently under clinical testing. The potential of GBS pilus proteins selected by genome-based reverse vaccinology as protective antigens for anti-streptococcal vaccines has also been demonstrated. Dressing pilus proteins with surface glycan antigens could be an attractive approach to extend vaccine coverage. We have recently developed an efficient method for tyrosine-directed ligation of large glycans to proteins via copper-free azide-alkyne [3 + 2] cycloaddition. This method enables targeting of predetermined sites of the protein, ensuring that protein epitopes are preserved prior to glycan coupling and a higher consistency in glycoconjugate batches. Herein, we compared conjugates of the GBS type II polysaccharide (PSII) and the GBS80 pilus protein obtained by classic lysine random conjugation and by the recently developed tyrosine-directed ligation. PSII conjugated to CRM197, a carrier protein used for vaccines in the market, was used as a control. We found that the constructs made from PSII and GBS80 were able to elicit murine antibodies recognizing individually the glycan and protein epitopes on the bacterial surface. The generated antibodies were efficacious in mediating opsonophagocytic killing of strains expressing exclusively PSII or GBS80 proteins. The two glycoconjugates were also effective in protecting newborn mice against GBS infection following vaccination of the dams. Altogether, these results demonstrated that polysaccharide-conjugated GBS80 pilus protein functions as a carrier comparably to CRM197, while maintaining its properties of protective protein antigen. Glycoconjugation and reverse vaccinology can, therefore, be combined to design vaccines with broad coverage. This approach opens a path to a new generation of vaccines. Tyrosine-ligation allows creation of more homogeneous vaccines, correlation of the immune response to defined connectivity points, and fine-tuning of the conjugation site in glycan-protein conjugates.
authors.forename: Alberto
authors.initials: A
authors.lastname: Nilo
authors.forename: Laura
authors.initials: L
authors.lastname: Morelli
authors.forename: Irene
authors.initials: I
authors.lastname: Passalacqua
authors.forename: Barbara
authors.initials: B
authors.lastname: Brogioni
authors.affiliation: ‡Novartis Institutes for BioMedical Research, 100 Technology Square, Cambridge, Massachusetts 02139, United States.
authors.forename: Martin
authors.initials: M
authors.lastname: Allan
authors.forename: Filippo
authors.initials: F
authors.lastname: Carboni
authors.forename: Alfredo
authors.initials: A
authors.lastname: Pezzicoli
authors.forename: Francesca
authors.initials: F
authors.lastname: Zerbini
authors.forename: Domenico
authors.initials: D
authors.lastname: Maione
authors.forename: Monica
authors.initials: M
authors.lastname: Fabbrini
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Romano
authors.affiliation: ‡Novartis Institutes for BioMedical Research, 100 Technology Square, Cambridge, Massachusetts 02139, United States.
authors.forename: Qi-Ying
authors.initials: QY
authors.lastname: Hu
authors.forename: Immaculada
authors.initials: I
authors.lastname: Margarit
authors.forename: Francesco
authors.initials: F
authors.lastname: Berti
authors.forename: Roberto
authors.initials: R
authors.lastname: Adamo
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry / Q000276:immunology / Q000627:therapeutic use*; D016667:Bacterial Capsules / Q000737:chemistry / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology / Q000627:therapeutic use*; D002460:Cell Line; D005260:Female; D010861:Fimbriae, Bacterial / Q000737:chemistry / Q000276:immunology; D006001:Glycoconjugates / Q000737:chemistry / Q000276:immunology / Q000627:therapeutic use*; D006801:Humans; D008239:Lysine / Q000737:chemistry / Q000276:immunology; D051379:Mice; D013290:Streptococcal Infections / Q000276:immunology / Q000517:prevention & control*; D022541:Streptococcal Vaccines / Q000737:chemistry / Q000276:immunology / Q000627:therapeutic use*; D013292:Streptococcus agalactiae / Q000276:immunology*; D014443:Tyrosine / Q000737:chemistry / Q000276:immunology; D014611:Vaccination; D018074:Vaccines, Conjugate / Q000737:chemistry / Q000276:immunology / Q000627:therapeutic use*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D006001:Glycoconjugates; D022541:Streptococcal Vaccines; D018074:Vaccines, Conjugate; C038687:capsular polysaccharide, streptococcal group B type II; D014443:Tyrosine; D008239:Lysine