Induction of the mucosal immune response

Immunological activities associated with milk

Milk contains a multitude of components that can, or may, provide immune protection to the suckling offspring and that also may promote development of neonatal immune competence. In addition, these specialized factors are essential for the protection of the mammary gland, the offspring's food source, from pathogen colonization and lactation failure. Breast milk also facilitates the establishment of a gut flora that inhibits colonization by many pathogens and stimulates the growth of beneficial microorganisms. Maternal immunity can be transferred to the infant via antibodies, primarily of the sIgA type in humans, as well as by leukocytes including effector and memory T lymphocytes. In this way, protection is provided passively against the pathogens to which the mother has been exposed. Currently, there is much interest in determining the protective efficacy of oral supplementation with immunoglobulins from the milk of lactating animals hyperimmunized against specific pathogens. An array of immunostimulatory components in milk, notably cytokines, may be protected against intestinal proteolysis, thereby providing the offspring with a prepackaged immune response system. These components may help to boost the infant's immature immune system. At the same time, anti-inflammatory factors in breast milk help to modulate cytokine responses to infection, thereby facilitating defense while minimizing tissue damage such as that which occurs in infants with necrotizing enterocolitis. Undoubtedly, the many components constituting the repertoire of immune and immunomodulating agents in milk interact synergistically to protect both the mammary gland and the offspring from invading pathogenic microorganisms.

Lipid matrix-based vaccines for mucosal and systemic immunization

For more than a decade our laboratories have been combining concepts in biochemistry, virology, and immunology in order to develop a conceptual basis for vaccine design. Our long-term goals have been to construct simple and well-defined immunogens that would stimulate specific immune responses in vivo. Using this approach, we hypothesized that it should be possible to define the structural and biochemical parameters of an immunogen that are necessary and sufficient to stimulate designated effector arms of the immune system. Through the use of covalently coupled peptide complexes, we have been able to define minimal requirements for the induction of humoral immune responses (Mannino et al., 1992). This represents a significant advance in eliciting an immune response to peptides, because it requires only peptides and phospholipids in the absence of additional adjuvants. It is different from the previous use of peptides and liposomes since here the peptides are covalently linked to a hydrophobic anchor and integrated into the phospholipid complex, rather than passively adsorbed or encapsulated. The presentation of peptide as part of a peptide-phospholipid complex (in contrast to encapsulation or nonspecific absorption) may be more similar to the natural presentation of an epitope in the context of an in vivo antigenic challenge. This technology also allows us to incorporate B and Th epitopes in a number of forms--as a single peptide, as two peptides in the same liposome, or as a peptide with viral glycoproteins in the same liposome. These data also demonstrate that Th epitopes do not have to be covalently linked to the B-cell epitope in order to provide help for that epitope. The implications of the data reported here are significant for both basic science and applied technologies. In basic science, the peptide-phospholipid complexes are potentially useful for analyzing the cooperative effects of B- and T-cell epitopes in the in vivo immune response. Since the peptide-phospholipid complexes are totally synthetic and highly immunogenic, they may be constructed in any formulation required to answer questions on the roles of B and T cells in promoting an immune response. Furthermore, since the number of antigenic sites is limited only by the number of peptides included in the peptide-phospholipid complexes, these constructs may be useful in producing antisera or monoclonal antibodies to weakly antigenic regions of a large protein, since the lack of antigenic competition should enhance the immunogenicity of these regions. Clinically, this technology will expand the potential for subunit vaccines.(ABSTRACT TRUNCATED AT 400 WORDS)