Clinical Trial: CVD 909 Vi Prime Boost Study

Study Status: Completed
Recruit Status: Completed
Study Type: Interventional

Official Title: Phase I Randomized, Double-Blind, Heterologous Prime-Boost Study of the Safety and Immunogenicity of Vi Polysaccharide Typhoid Vaccine After Priming by Live Attenuated Oral Vi+ Salmonella Typhi Strain

Brief Summary: The purpose of this research study is to see if giving a typhoid vaccine by mouth (an experimental vaccine, CVD 909) before giving a vaccine shot (Typhim Vi) will result in a better immune response than giving Typhim Vi vaccine by itself. Another purpose is to see whether CVD 909 is safe. Typhim Vi has been shown to be safe and effective in preventing typhoid fever in older children and adults, but it does not work in children under age 2. Scientists at the University of Maryland think that young children could respond to Typhim Vi if they were given a dose of the other typhoid vaccine by mouth before they are given the Typhim Vi shot. Twenty-eight healthy adult volunteers, ages 18-40 years, will take part in this study. Study participation will last for up to 63 weeks, but most of the study visits will be in the first 6 weeks. Blood samples will be collected approximately 13 times. Four stool samples will be collected. Some volunteers may be followed for an additional 4 years.

Detailed Summary: This is a phase I, randomized, double-blind, heterologous prime-boost study of the safety and immunogenicity of Vi polysaccharide typhoid vaccine after priming by live, attenuated oral Vi+ Salmonella Typhi strain CVD 909. The primary study objective is to determine the phase 1 safety of the prime-boost regimen of priming with CVD 909, a live attenuated Vi+ S. Typhi strain, followed by boosting with licensed parenteral Vi polysaccharide vaccine in healthy adult volunteers. The secondary objective is to compare the immunogenicity of licensed parenteral Vi polysaccharide vaccine in volunteers primed with a single oral dose of CVD 909 and in volunteers who are not primed with the oral vaccine. The outcome measures of interest are the seroconversion rate and titer of serum IgG anti-Vi antibodies, the timing of development and longevity of serum anti-Vi antibodies, the subclasses and avidity of antibodies developed, and the memory B and T cell responses elicited. The following immunologic outcome measures will be sought: rate and timing of seroconversion in each study arm after receiving Vi polysaccharide and analysis of immunoglobulin subclasses and avidity. This will assess the presence of priming and the rapidity of the anamnestic response. A successful priming would accelerate the response to the boost (Day 7 after Vi vaccine), and this response is expected to be more balanced, inducing both Th1/Th2-type immunity evidenced by the induction of both IgG1 and IgG2; geometric mean titer (GMT) of serum IgG anti-Vi antibodies on Days 7, 14, 21, and 35 post-Vi (Days 28, 35, 42, and 84 of the study). This will assess magnitude of response (another measure of priming); GMT of serum IgG Vi antibody in each study arm at multiple later time points up to 1 year after receiving parenteral Vi (week 55 of the study). This will assess the quality and duration of the antibodies; and peripheral blood mononuclear cells will be collected to measure cytokine production and cytotoxic T lymp
Sponsor: National Institute of Allergy and Infectious Diseases (NIAID)

Current Primary Outcome: Safety: determined by symptom diaries, interim medical histories obtained by interview, by blood and stool cultures, and by clinical laboratory tests. [ Time Frame: During the 1st 14 days after ingestion of CVD 909 vaccine or placebo, during the 3 days after receiving parenteral Typhim Vi vaccine at Day 24, and interim medical history for safety at Day 42. ]

Original Primary Outcome:

Current Secondary Outcome:

  • Immunogenicity: assessed by specific antibody secreting cell assays. [ Time Frame: Days 0 and 10 after oral administration of CVD 909 and Days 0 and 7 after administration of parenteral Vi. ]
  • The timing of development and longevity of serum anti-Vi antibodies. [ Time Frame: Days 0 and 10 after oral administration of CVD 909 and Days 0 and 7 after administration of parenteral Vi. ]
  • The subclasses and avidity of antibodies developed. [ Time Frame: Days 0 and 10 after oral administration of CVD 909 and Days 0 and 7 after administration of parenteral Vi. ]
  • Seroconversion rate and titer of serum IgG anti-Vi antibodies. [ Time Frame: Days 0, 10, 14+/-2, 21+/-2, 28+/-2, 35+/-2, 42+/-2, and 84+/-7 and at 29+/-2 weeks and 55+/- 4 weeks, and every 6 months for 4 years for volunteers who remain seropositive at week 55 and agree to continue participation in the study. ]


Original Secondary Outcome:

Information By: National Institute of Allergy and Infectious Diseases (NIAID)

Dates:
Date Received: May 12, 2006
Date Started: February 2006
Date Completion:
Last Updated: May 8, 2014
Last Verified: February 2010