Combined Conjugate Vaccines: Enhanced Immunogenicity with the N19 Polyepitope as a Carrier Protein

Abstract

The N19 polyepitope, consisting of a sequential string of universal human CD4؉ -T-cell epitopes, was tested as a carrier protein in a formulation of combined glycoconjugate vaccines containing the capsular polysaccharides (PSs) of Neisseria meningitidis serogroups A, C, W-135, and Y. Good antibody responses to all four polysaccharides were induced by one single immunization of mice with N19-based conjugates. Two immunizations with N19 conjugates elicited anti-MenACWY antibody titers comparable to those induced after three doses of glycoconjugates containing CRM197 as carrier protein. Compared to cross-reacting material (CRM)-based constructs, lower amounts of N19-MenACWY conjugates still induced high bactericidal titers to all four PSs. Moreover, N19-MenACWY-conjugated constructs induced faster and higher antibody avidity maturation against meningococcal C PS than CRM-based conjugates. Very importantly, N19-specific antibodies did not cross-react with the parent protein from which N19 epitopes were derived, e.g., tetanus toxoid and influenza virus hemagglutinin. Finally, T helper epitopes of the N19 carrier protein were effectively generated both in vivo (after immunization with the N19 itself) and in vitro (after restimulation of epitope-specific spleen cells). Taken together, these data show that the N19 polyepitope represents a strong and valid option for the generation of improved or new combined glycoconjugate vaccines.

Preclinical studies on new proteins as carrier for glycoconjugate vaccines

“…rEPA is also used as a carrier for glycoconjugate vaccines directly synthesized in Escherichia coli against Shigella dysenteriae type 1 [21]. A rationally designed recombinant protein containing strings of promiscuous human CD4+ T-cell epitopes derived from various pathogens including tetanus, influenza virus, Plasmodium falciparum and hepatitis B virus, proved to be a very good carrier for Hib and meningococcal oligosaccharides [22][23][24]. Endeavors to develop carrier proteins which might also provide protection against a target pathogen, have recently broadened to include candidates from diverse vaccine categories [25][26][27][28][29][30].…”

Pulmonary Immunization of Guinea Pigs with Diphtheria CRM-197 Antigen as Nanoparticle Aggregate Dry Powders Enhance Local and Systemic Immune Responses

“…Neutralizing antibodies are thus protective responses that mimic responses to a natural infection. Vaccines based on CrmAg induce the production of anti-CrmAg antibodies; these antibodies also recognize diphtheria toxin as the CrmAg differs from the native toxin by only one amino acid (31).…”

Meningococcal vaccine evolution

“…Per ovviare a tali limiti, recentemente sono stati sviluppati vaccini costituiti da unità polisaccaridiche coniugate a una proteina carrier (tossoide tetanico, tossoide difterico, materiale cross-reattivo difterico (CRM197)) [17].…”

“…La presentazione del complesso antigenico induce, a differenza dei vaccini polisaccaridici, la produzione di elevati livelli anticorpali, un'elevata avidità anticorpale e aumenta l'attività battericida sierica. Inoltre è responsabile della formazione di popolazioni stabili di linfociti B tipo memory, fornendo una risposta anamnestica (effetto booster), in caso di ri-esposizione [17,18].…”