PEPscreen® used in vaccine development for Mycobacterium tuberculosis

(1) Roupie, V. et al. (2008). Immunogenicity and protective efficacy of DNA vaccines encoding MAP0586c and MAP4308c of Mycobacterium avium subsp. paratuberculosis secretome. Vaccine. 26(37): 4783-4794. [PubMedID: 18652866]

(2) Romano and Rindi, et al. (2008). Immunogenicity and protective efficacy of tuberculosis subunit vaccines expressing PPE44 (Rv2770c). Vaccine. 26(48): 6053-6063. [PubMedID: 18822333]

Mycobacterium avium subsp. paratuberculosis (MAP) protein is an etiological agent in chronic enteritis in ruminants, causing widespread disease. Development of a vaccine would aid some of the financial losses suffered by the livestock industry as a result of this disease. Roupie et al.(1), generated a PEPscreen® custom peptide library to screen overlapping peptides from two candidate antigens from the MAP protein (MAP0586c and MAP4308c) to identify immunodominant T cell epitopes that could be used as a potential vaccine.

Splenocytes from Balb/c and C57BL/6 mice immunized with plasmid DNA vaccines to the two MAP antigens were stimulated in vitro with PEPscreen® peptides and the levels of IL-2 and IFN gamma that were produced were measured by sandwich ELISA. For both antigens, stronger IL-2 and IFN gamma responses were seen for Balb/c mice than for C57BL/6. The results identified novel immunodominant T cell epitopes for the MAP0586c protein in MAP infected mice, but concluded that the weaker responses observed with the MAP4308c protein indicates that it is not an immunodominant T cell antigen in MAP infected mice.

In a further study by the same group, Romano et al.(2) used a PEPscreen® peptide library as part of their research into new potential subunit vaccines against tuberculosis (TB) in humans. An overlapping library for the PPE44 protein family of M. tubercuolosis was synthesized. There is little functional information currently available about the PPE proteins, but they are known to elicit strong immune responses in TB infected humans and mice. This study sought to map the specific responding peptides. As with the study by Roupie et al., splenocytes from vaccinated and infected mice were stimulated with the overlapping PPE44 peptides and IL-2 and IFN gamma production was measured by ELISA. These experiments identified a strong potential CD4+ T cell epitope in the first 20 amino acids at the N-terminus of the protein. This appears to be a conserved area in a number of proteins in the PPE sub-family that elicit strong CD4 responses, which could be included in new subunit TB vaccines.