Abstract: The invention is related to peptide constructs, i.e., polypeptides obtained by linking together two or more peptides based on or derived from different molecules, which are useful in the treatment or prevention of influenza virus and other infectious diseases. Compositions containing the same, methods for producing the same, and methods for using the same are also disclosed, wherein the peptide constructs have the formula P1-x-P2, where P2 is a peptide associated with an infectious agent and P1 is a peptide that will bind to a class of immune cells, such as dendritic cells. The peptide construct can cause the maturation of immature dendritic cells to a more mature state. The peptide construct or the more mature dendritic cell can be administered to a subject to modulate or initiate an immune response against an infectious agent.