Self heat-shock protein (hsp60) peptide serves in a conjugate vaccine against a lethal pneumococcal infection

Healthy persons manifest a high frequency of T cells reactive to epitopes of the self 60-kDa heat-shock protein (hsp60) molecule. It was reasoned that a self hsp60 peptide, p458m, might provide T cell help for a response to the T independent capsular polysaccharide of Streptococcus pneumoniae type 4 (PS4). The conjugate vaccine (PS4-p458m) induced resistance to challenge with >300,000 times the minimal lethal dose of pneumococci. PS4 conjugated to other immunogenic carriers (tetanus toxoid, a pneumolysin peptide, and others) or a commercial pneumococcal vaccine were far less effective. The effectiveness of the PS4-p458m conjugate was associated with an increased IgG1 antibody response to PS4, with long-term memory, and with T cell responses to the p458m peptide. Thus, T cell reactivity to a self epitope in a conjugate vaccine can be mobilized to induce help for resistance to a lethal infection.