Potentials and limitations of protein vaccines in infants

Immunization of infants represents a difficult challenge since immune responses in infants differ qualitatively from those of adults (immature immune and bias towards Th2 rather than a Th1 immune responses). While protein vaccines are immunogenic in infants earlier than polysaccharides in the very first months of life, requiring repeated administration. Protein vaccines such as diphtheria and tetanus toxoids and hepatitis B antigens are safe and immunogenic in infants, able to induce long-lasting memory, and effective. HB vaccines are the first vaccines administered at birth against a sexually transmitted disease and that prevent cancer. These success stories must however be tempered by the existence of immunologic interferences that may occur when combining vaccines in a single injection. Moreover, very little is known whether inappropriate protein conformation and glycosylation play roles in the impairment of the functional immunogenicity of protein vaccines in infants. Although much is known about how to produce and purify proteins, we know much less about how protein characteristics are related to functional immunogenicity.