Immunity in neonates.

Area of Science:

• Immunology
• Vaccinology

Background:

• Newborns possess an immature immune system, leading to weak, Th2-polarized immunity, which increases susceptibility to endemic infections.
• Maternal antibodies, while protective initially, can interfere with active immunization in newborns.
• The Th2 bias in newborns is influenced by maternal factors like progesterone and cytokines at the maternal-fetal interface.

Purpose of the Study:

• To investigate methods for overcoming the Th2 immune bias in newborns to enable effective vaccination.
• To explore the potential of adjuvants in modulating neonatal immune responses for enhanced vaccine efficacy.

Main Methods:

• Utilizing Sendai virus envelope proteins as model antigens in 2-day-old mice.
• Administering Th1 or Th2 adjuvants to prime neonatal immune responses.
• Assessing the long-term effects of priming and subsequent boosts.
• Evaluating adjuvant effects on immune responses in immunologically mature mice (6 weeks old).
• Examining the efficacy of Th1-driving adjuvants in various animal species (dog, sheep, horse, seal).

Main Results:

• Neonatal priming with specific adjuvants induced either Th1 or Th2 responses, with long-lasting effects when followed by boosts.
• Adjuvants could modulate immune priming effects even when administered to immunologically mature animals.
• Th1-driving adjuvants demonstrated efficacy in inducing immune responses and protection in newborns where conventional vaccines failed across multiple species.

Conclusions:

• The Th2 bias present around birth can be successfully overcome through targeted immunological interventions.
• Appropriate adjuvant selection is crucial for directing neonatal immune responses towards effective vaccination.
• These findings suggest a promising strategy for improving vaccine efficacy and protecting newborns and young animals against infectious diseases.