Technical Abstract: Peptide hydrogels are considered injectable materials for drug delivery and tissue engineering applications. Most published hydrogel-forming sequences contain either alternating-charged and noncharged residues or amphiphilic blocks. Here, we report a self-assembling peptide, h9e (FLIVIGSIIGPGGDGPGGD), designed by rationally combining two native sequences from an elastic segment of spider silk and a trans-membrane segment of human muscle L-type calcium channel. The turning segment GSII of h9e promoted hydrogel formation in both Ca2+ solution and acidic pH conditions at water content greater than 99.5%. Although h9e Ca2+ hydrogel and h9e acidic hydrogel have the same sequence, they have distinct physical properties. The shear-thinning, rapid-strength-recovering h9e Ca2+ hydrogel was used as an H1N1 influenza vaccine adjuvant. The h9e adjuvant was biologically safe and improved immune response by _70% compared with an oil-based commercial adjuvant.