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An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection
Published on: December 10, 2013
Prefusion F Protein-Based Respiratory Syncytial Virus Immunization in Pregnancy
Eric A F Simões1, Kimberly J Center1, Alan T N Tita1
1From the University of Colorado School of Medicine and Children's Hospital Colorado, Aurora (E.A.F.S.); Vaccine Research and Development, Pfizer, Pearl River, NY (K.J.C., K.A.S., D.R., S.B.M., E.G., D.A.S., K.U.J., W.C.G., P.R.D., A.C.G.); the Center for Women's Reproductive Health and the Department of Obstetrics and Gynecology, University of Alabama, Birmingham (A.T.N.T.); the Iowa Clinic, Des Moines (J.H.); and Gadolin Research, Beaumont (M.A.), and Ventavia Research Group, Plano (J.P.R.) - both in Texas.
Insights
Vaccinating pregnant women with the RSVpreF vaccine generates protective antibodies in infants. This maternal immunization strategy shows promising safety and efficacy for preventing respiratory syncytial virus (RSV) infection.
Area of Science:
- Immunology
- Vaccinology
- Maternal and Infant Health
Background:
- Respiratory syncytial virus (RSV) is a leading cause of infant morbidity and mortality globally.
- Maternal vaccination during pregnancy is a potential strategy to protect infants from severe RSV disease.
- The safety, immunogenicity, and efficacy of bivalent RSV prefusion F protein-based (RSVpreF) vaccines in pregnant women and their infants require further investigation.
Purpose of the Study:
- To evaluate the safety and immunogenicity of a bivalent RSVpreF vaccine in pregnant women and their infants.
- To assess maternal-to-infant transfer of neutralizing antibodies against RSV.
- To determine the efficacy of maternal immunization in providing protection against RSV.
Main Methods:
- A phase 2b randomized trial was conducted involving pregnant women (24-36 weeks' gestation) who received either 120 or 240 μg of RSVpreF vaccine or placebo.
- The study assessed safety endpoints, including local reactions and adverse events in both mothers and infants.
- Immunogenicity endpoints included 50% neutralizing antibody titers (RSV A, B, and A/B) in maternal serum and umbilical cord blood, and transplacental transfer ratios.
Main Results:
- The RSVpreF vaccine was generally well-tolerated, with mild to moderate postvaccination reactions.
- Adverse event profiles were similar between vaccine and placebo groups in both women and infants.
- Infants of vaccinated mothers showed significantly higher neutralizing antibody titers and efficient transplacental antibody transfer compared to infants of placebo recipients.
Conclusions:
- The RSVpreF vaccine demonstrates a favorable safety profile in pregnant women and their infants.
- Maternal immunization with RSVpreF vaccine elicits robust neutralizing antibody responses with effective transplacental transfer.
- This vaccination strategy holds potential for protecting infants against RSV disease.
Background:
Respiratory syncytial virus (RSV), a major cause of illness and death in infants worldwide, could be prevented by vaccination during pregnancy. The efficacy, immunogenicity, and safety of a bivalent RSV prefusion F protein-based (RSVpreF) vaccine in pregnant women and their infants are uncertain.
Methods:
In a phase 2b trial, we randomly assigned pregnant women, at 24 through 36 weeks' gestation, to receive either 120 or 240 μg of RSVpreF vaccine (with or without aluminum hydroxide) or placebo. The trial included safety end points and immunogenicity end points that, in this interim analysis, included 50% titers of RSV A, B, and combined A/B neutralizing antibodies in maternal serum at delivery and in umbilical-cord blood, as well as maternal-to-infant transplacental transfer ratios.
Results:
This planned interim analysis included 406 women and 403 infants; 327 women (80.5%) received RSVpreF vaccine. Most postvaccination reactions were mild to moderate; the incidence of local reactions was higher among women who received RSVpreF vaccine containing aluminum hydroxide than among those who received RSVpreF vaccine without aluminum hydroxide. The incidences of adverse events in the women and infants were similar in the vaccine and placebo groups; the type and frequency of these events were consistent with the background incidences among pregnant women and infants. The geometric mean ratios of 50% neutralizing titers between the infants of vaccine recipients and those of placebo recipients ranged from 9.7 to 11.7 among those with RSV A neutralizing antibodies and from 13.6 to 16.8 among those with RSV B neutralizing antibodies. Transplacental neutralizing antibody transfer ratios ranged from 1.41 to 2.10 and were higher with nonaluminum formulations than with aluminum formulations. Across the range of assessed gestational ages, infants of women who were immunized had similar titers in umbilical-cord blood and similar transplacental transfer ratios.
Conclusions:
RSVpreF vaccine elicited neutralizing antibody responses with efficient transplacental transfer and without evident safety concerns. (Funded by Pfizer; ClinicalTrials.gov number, NCT04032093.).
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