This is a Phase 1 single center, dose-escalation study designed to evaluate the safety and immunogenicity of live, replication competent recombinant Adenovirus type 4-H5N1 Influenza Vietnam 1194 Hemagglutinin (HA) (Ad4-H5-Vtn). Determining the optimal route and dose for this recombinant platform will greatly accelerate investigations of this vector as an influenza vaccine and an HIV vaccine platform.
The primary goal of this study is to evaluate safety of ascending dosages of the Ad4-H5-Vtn vaccine following intranasal administration. A dosage will be selected to further evaluate the humoral, cellular, and mucosal immune responses against both the vector and the inserted gene. The Ad4-H5-Vtn will be initiated at 103 viral particles (vp). Once safety is established at the initial dose, a second round of testing will begin at the next ten-fold higher dose. The Ad4-H5-Vtn vaccine will be assessed in three participants at each dosage level. The maximum viral dose administered will be 108 vp.
In addition to clinical and laboratory monitoring of safety, the principal assessments will be shedding of the Ad4-H5-Vtn virus in rectal, cervicovaginal, throat, and nasal swabs, and assessment of the antibody (mucosal and systemic) response to the HA and to the Ad4 virus. Participants will remain in the NIH Special Clinical Studies Unit until they have 2 consecutive negative nasal washes or 7 days have elapsed since vaccination, whichever occurs first; they may remain on the unit longer if medically necessary. When safety has been confirmed in all 3 participants at a given dosage level, the next higher dose group is enrolled. If one grade 3 or greater toxicity (or pre-specified grade 2 toxicity, see Section 3.4) at least possibly related to the vaccine is observed, the group will be expanded at that dose. If a second at least possibly related grade 3 or greater toxicity (or pre-specified Grade 2 toxicity, see Section 3.4) is observed, the dose will be reduced one level and the group will be expanded. Up to 25 Ad4-seronegative individuals will be enrolled at the maximum tolerated dose to fully evaluate safety and immunogenicity in the protocol.
All participants will be followed for 28 days following immunization, and again at 8 and 26 weeks to evaluate any long-term toxicity and persistence of immunity. All subjects will be offered to receive a booster vaccine at the 26-week visit and be seen for follow-up visits 4 and 8 weeks following booster immunization with an additional telephone follow-up 6 months after boosting. Household and intimate contacts will also be enrolled and monitored for Adenovirus and HAI antibodies following Ad4-H5-Vtn administration only; household and intimate contacts will not be enrolled or monitored during the boost portion of the study.
We will conduct an expansion H5N1 boost phase of this study, in which all vaccinees from the initial phase of the study will be offered re-enrollment to receive a booster vaccination with an FDA-approved H5N1 inactivated monovalent influenza vaccine. We will offer enrollment in the expansion phase to all participants who received the Ad4-H5-Vtn vaccine in the initial phase, regardless of whether they also received the recombinant hemagglutinin influenza H5 vaccine boost. We will also enroll individuals who have never received an H5 influenza vaccine as controls. Participants will receive a single vaccination with the H5N1 vaccine and be seen for follow-up visits 4 and 8 weeks later for immunogenicity evaluations.