Avidity of pertussis toxin antibodies following vaccination with genetically versus chemically detoxified pertussis toxin-containing vaccines during pregnancy
Both the quantity and quality of circulating anti-pertussis toxin antibodies are important for protection against severe pertussis. We compared the avidity of PT-IgG antibodies in pregnant women and their infants following vaccination during pregnancy with pertussis vaccines containing genetically-detoxified pertussis toxin (PTgen) or chemically-detoxified PT (PTchem).
Methods: We analyzed serum samples collected earlier from pregnant women (at delivery) and their infants (at birth and 2 months of age) participating in a clinical trial where pregnant women had been vaccinated during pregnancy with recombinant acellular pertussis vaccine containing 1 µg PTgen (standalone, ap1gen, [n=37], or combined to tetanus and diphtheria, Tdap1gen [n=34]), 2 µg PTgen (Tdap2gen, n=35), or 5 µg PTgen (TdaP5gen, n=34), or acellular pertussis vaccine containing 8 µg PTchem (Tdap8chem, n=35). Avidity was assessed by adding increasing concentrations (0.25, 0.5, 1, 1.5, 2, and 3 M) of NH4SCN as a bond-breaking agent and measuring PT-IgG levels by ELISA.
Findings: Compared with Tdap8chem, TdaP5gen vaccination was associated with significantly higher total absolute avidity (p<0.001) and medium-high to very-high avidity PT-IgG levels (p≤0.02) in mothers at delivery, infants at birth and infants at 2 months of age. Avidity was comparable to Tdap8chem after vaccination with the low-dose PTgen formulations (ap1gen, Tdap1gen or Tdap2gen). There were no differences for vaccination during the 2nd or 3rd trimester of pregnancy.
Interpretation: Compared with chemically detoxified vaccines, vaccination during pregnancy with recombinant genetically detoxified acellular pertussis vaccine at lower PT concentration provides infants with at least similar or higher quality PT-IgG antibodies. Consequently, recombinant pertussis vaccines may offer comparable or better protection against pertussis.
Keywords: avidity; genetically inactivated; maternal immunization; pertussis; pertussis toxin; recombinant vaccine; vaccination during pregnancy.
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