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Neonatal and infantile immune responses to encapsulated bacteria and conjugate vaccines

Peter Klein Klouwenberg1, Louis Bont

  • 1Department of Pediatric Infectious Diseases and Immunology, Wilhelmina Children's Hospital, University Medical Centre, Room KE4.133.1, PO Box 85090, 3508 AB Utrecht, The Netherlands.

Clinical & Developmental Immunology
|October 1, 2008
PubMed

Insights

Infant immune responses to encapsulated bacteria are poor because polysaccharides are thymus-independent (TI)-2 antigens. Conjugating these polysaccharides to carrier proteins converts them to thymus-dependent (TD) antigens, improving infant immunity and vaccine efficacy.

Area of Science:

  • Immunology
  • Pediatrics
  • Vaccinology

Background:

  • Encapsulated bacteria cause significant infant mortality.
  • Bacterial surface polysaccharides are key virulence factors, but poorly immunogenic in infants.
  • Most bacterial polysaccharides are thymus-independent (TI)-2 antigens, eliciting inadequate responses in neonates.

Purpose of the Study:

  • To discuss mechanisms of infant unresponsiveness to TI-2 antigens.
  • To explore strategies for overcoming inadequate infant immune responses to encapsulated bacteria.
  • To review current vaccine development approaches for infant protection.

Main Methods:

  • Discussion of immunological mechanisms underlying infant hypo-responsiveness.
  • Review of polysaccharide-protein conjugation as a strategy to enhance immunogenicity.
  • Analysis of the efficacy of conjugated vaccines in preventing invasive bacterial diseases in infants.

Main Results:

  • Infants exhibit inadequate immune responses to thymus-independent (TI)-2 antigens like bacterial polysaccharides.
  • Conjugating polysaccharides to carrier proteins transforms them into thymus-dependent (TD) antigens.
  • This transformation elicits robust immune responses and immunological memory in infants.

Conclusions:

  • Polysaccharide-protein conjugate vaccines are effective against common invasive diseases in neonates and children.
  • Conjugation is a critical strategy to overcome infant immunodeficiency to encapsulated bacteria.
  • Further vaccine development is exploring novel approaches to enhance infant protection.

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