Metabolic, Humoral, and CellularResponses in Adult VolunteersImmunized with the GeneticallyInactivated PertussisToxin Mutant PT 9K/129G

Summary PT 9K/129G, anontoxicmutantofpertussis toxin(PT)obtainedby geneticmanipulation,has beenshown inanimalmodelstobe apromisingcandidatefornew vaccinesagainstwhooping cough.To assessthesafetyand theimmunogenicityofPT-9K/129G inhumans,apilotstudy hasbeenperformedinadultvolunteers .The proteinwas foundtobe safe,capableofinducing hightiters oftoxin-neutralizing antibodies, andcapableofgeneratingimmunologicalmemory . Infact,vaccination causedanincreaseofcell-mediated responsetoPT,PT 9K/129G, S1subunit, andB oligomer,indicatingthatmemory T cellsareinducedby thevaccine.SincePT-9K/129G ismitogenicforT lymphocytesinvitro,itwas investigated whetherthisactivity isalsopresent invivo.No variation was observedintheproportionofT cells(CD3'), T helpercells(CD4+), and cytotoxicT cells(CD8+), aswellasin thatof otherlymphoid populations, by FACS analysis .Interestingly, no thoroughcorrelation wasfoundbetweenhumoralandcellular responses . Inonecase,averyhighcellular responsewaspresentinabsenceofdetectable antibodies, suggesting thattheantibodyresponse,which istheonlyparametermeasuredinmost clinical trials, may not givea completepictureoftheresponseinducedby a vaccine.