The intrinsic peritrophic matrix protein peritrophin-95 from larvae of Lucilia cuprina is synthesised in the cardia and regurgitated or excreted as a highly immunogenic protein.

The intrinsic peritrophic matrix glycoprotein, peritrophin-95, from the midgut of larvae of Lucilia cuprina can only be solubilized from the matrix using strong denaturants. This suggests that the protein has a structural role in the matrix. Consistent with this is the finding that immuno-gold and immuno-fluorescence localizations of the protein showed a uniform distribution within the peritrophic matrix. RT-PCR demonstrated that expression of peritrophin-95 mRNA was restricted to the larval cardia, a small organ located in the anterior midgut from which the type 2 peritrophic matrix originates. Immuno-blots and ELISAs demonstrated that the sera from sheep infested naturally or artificially with these larvae recognised peritrophin-95. This indicates that peritrophin-95 stimulates the ovine immune system during larval infestation even though the protein is firmly attached to the peritrophic matrix in the larval midgut and seemingly "concealed" from the ovine immune surveillance system. Analyses of larval regurgitated or excreted material by immuno-blots, immuno-affinity purification and amino-terminal sequencing demonstrated the presence of soluble monomeric peritrophin-95. These results indicate that peritrophin-95, a candidate vaccine antigen for use in sheep is not a "concealed" antigen as previously thought. The presence of soluble peritrophin-95 in the regurgitated/excreted material from larvae suggests that this protein may be involved in a maturation phase of peritrophic matrix production, a by-product of which is the excretion or regurgitation of soluble peritrophin-95.