Background: causes serious health care- and community-associated disease, requiring improved preventive measures such as vaccines. The investigational 4-antigen vaccine (SA4Ag), comprising capsular polysaccharide serotypes 5 and 8 (CP5 and CP8) conjugated to CRM, recombinant mutant clumping factor A (rClfA), and recombinant manganese transporter protein C (rP305A or rMntC), was well tolerated, inducing robust functional immune responses to all 4 antigens through 12 months postvaccination. This is a serological extension study through 36 months postvaccination.
Methods: In 2 previous studies, healthy adults received SA4Ag, SA3Ag (without rMntC), or placebo; serology was also assessed at ~24 and ~36 months postvaccination. Functional immune responses (antibody responses that facilitate killing of or neutralize virulence mechanisms) were assessed with opsonophagocytic activity killing assays (CP5 or CP8) and a fibrinogen-binding inhibition assay (ClfA). A competitive Luminex immunoassay assessed ClfA and rMntC responses. Adverse events within 48 hours of blood draw were recorded.
Results: Four hundred forty subjects (18-64 years old, 255; 65-85 years old, 185) were enrolled. At 24 and 36 months postvaccination, subjects receiving SA4Ag had substantially higher geometric mean titers (GMTs) for CP5, CP8, and ClfA vs baseline; geometric mean fold rises (GMFRs) from baseline to month 36 were 2.7-8.1. For rMntC, 36-month GMTs declined from peak levels but remained above baseline for all SA4Ag groups; GMFRs from baseline to month 36 were 1.8 and 1.5 in the younger and older cohorts, respectively.
Conclusions: Persistent functional immune responses to antigens were observed through 36 months in healthy adults.
Clinicaltrialsgov: NCT01643941 and NCT01364571.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6978999 | PMC |
http://dx.doi.org/10.1093/ofid/ofz532 | DOI Listing |
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