Long-term safety and vaccine-induced seropositivity in healthy volunteers from HIV vaccine trials.

BACKGROUND: The ANRS COV1-COHVAC cohort was a long-term safety cohort of healthy volunteers who received preventive HIV-vaccine candidates in 17 phase I/II clinical trials. METHODS: Data collected from the first vaccine candidate administration and annually after inclusion in the cohort included grade 3/4 adverse events and all grade adverse events suggestive of neurological, ophthalmological and immune disorders, self-administered questionnaires on behaviors and HIV ELISA results. Age-and-sex-standardized mortality ratios (SMRs) were calculated with respect to the French population. The cohort was early terminated in 2016 due to the absence of safety signal. RESULTS: Of 496 volunteers, 488 were included: 355 in the 7-year prospective follow-up and 133 in the retrospective data collection only. The total follow-up after the first vaccination was 4934 person-years (median: 10 years) and 270 (76%) volunteers completed their follow-up. No relevant adverse event possibly related to the vaccine was reported. Breast cancer incidence and woman mortality did not differ from those of the French general population (standardized incidence ratio = 1.47, P = 0.45 and SMR = 0.65, P = 0.28, respectively) while man mortality was significantly lower (SMR = 0.26, P = 0.0003). At the last visit, 21/29 (72%) volunteers who received the recombinant HIV gp160 protein still showed vaccine-induced seropositivity after a median follow-up of 23 years. Only a few volunteers reported risky sexual practices (men: 20/192, women: 2/162). CONCLUSION: Volunteers showed a sustained high commitment. No long-term safety alert was identified during the postvaccine follow-up. Participating in vaccine trials did not increase risky behaviors for HIV infection. Vaccine-induced seropositivity may persist for more than 23 years after receiving rgp160.

Accelerating clinical development of HIV vaccine strategies: methodological challenges and considerations in constructing an optimised multi-arm phase I/II trial design.

BACKGROUND: Many candidate vaccine strategies against human immunodeficiency virus (HIV) infection are under study, but their clinical development is lengthy and iterative. To accelerate HIV vaccine development optimised trial designs are needed. We propose a randomised multi-arm phase I/II design for early stage development of several vaccine strategies, aiming at rapidly discarding those that are unsafe or non-immunogenic. METHODS: We explored early stage designs to evaluate both the safety and the immunogenicity of four heterologous prime-boost HIV vaccine strategies in parallel. One of the vaccines used as a prime and boost in the different strategies (vaccine 1) has yet to be tested in humans, thus requiring a phase I safety evaluation. However, its toxicity risk is considered minimal based on data from similar vaccines. We newly adapted a randomised phase II trial by integrating an early safety decision rule, emulating that of a phase I study. We evaluated the operating characteristics of the proposed design in simulation studies with either a fixed-sample frequentist or a continuous Bayesian safety decision rule and projected timelines for the trial. RESULTS: We propose a randomised four-arm phase I/II design with two independent binary endpoints for safety and immunogenicity. Immunogenicity evaluation at trial end is based on a single-stage Fleming design per arm, comparing the observed proportion of responders in an immunogenicity screening assay to an unacceptably low proportion, without direct comparisons between arms. Randomisation limits heterogeneity in volunteer characteristics between arms. To avoid exposure of additional participants to an unsafe vaccine during the vaccine boost phase, an early safety decision rule is imposed on the arm starting with vaccine 1 injections. In simulations of the design with either decision rule, the risks of erroneous conclusions were controlled <15%. Flexibility in trial conduct is greater with the continuous Bayesian rule. A 12-month gain in timelines is expected by this optimised design. Other existing designs such as bivariate or seamless phase I/II designs did not offer a clear-cut alternative. CONCLUSIONS: By combining phase I and phase II evaluations in a multi-arm trial, the proposed optimised design allows for accelerating early stage clinical development of HIV vaccine strategies.

Combined vaccination of live 1B Chlamydophila abortus and killed phase I Coxiella burnetii vaccine does not destroy protection against chlamydiosis in a mouse model.

Q fever and chlamydiosis often affect ovine and caprine flocks simultaneously or successively. Combination vaccines effective against these 2 diseases would be of great value in veterinary medicine. Unfortunately, the current effective vaccines are a live vaccine for chlamydiosis and killed vaccine for Q fever. Vaccination of mice with live chlamydiosis vaccine 1B and killed phase I vaccine against Q fever at 2 points on the back at the same time produced good protection against chlamydial abortion. This suggests that it may be possible to vaccinate ewes and goats against chlamydiosis and Q fever simultaneously.

Abortive potency of Chlamydophila abortus in pregnant mice is not directly correlated with placental and fetal colonization levels.

Abortion, placental and fetal colonization, and levels of gamma interferon were analyzed for four Chlamydophila abortus strains presenting antigenic variations in a mouse model. Expression of virulence of these strains varied and indicated that abortion was not directly related to the number of bacteria in the placenta, and thus, other factors may have an important role in activating the abortion process.