A compound comprising one or more polysaccharide moieties each independently represented by the formula β(1→4)-[GlcNH—R]n-2,5-anhydromannose, wherein n is a positive integer from 3 to 500, and R is H or an acyl group, is described. The compound can be manufactured by (a) reacting chitosan with an acylating agent sufficient to partially N-acylate the chitosan, yielding a modified chitin/chitosan mixed polymer； and (b) reacting the modified chitin/chitosan mixed polymer with a deaminating agent to cleave the mixed polymer at the unacylated chitosan moieties. The compound can be used to immunize against fungal infection. Antibodies specific to the compound, and the use of such antibodies to protect against fungal infection are also described.
