Remi Forrat

Live Attenuated Chimeric Yellow Fever Dengue Type 2 (ChimeriVax™-DEN2) Vaccine: Phase I Clinical Trial for Safety and Immunogenicity: Effect of Yellow Fever Pre-immunity in Induction of Cross Neutralizing Antibody Responses to All

A randomized double-blind Phase I Trial was conducted to evaluate safety, tolerability, and immunogenicity of a yellow fever (YF)-dengue 2 (DEN2) chimera (ChimeriVax™-DEN2) in comparison to that of YF vaccine (YF-VAX®). Forty-two healthy YF naïve adults randomly received a single dose of either ChimeriVax™-DEN2 (high dose, 5 log plaque forming units [PFU] or low dose, 3 log PFU) or YF-VAXâ by the subcutaneous route (SC). To determine the effect of YF pre-immunity on the ChimeriVaxTM-DEN2 vaccine, 14 subjects previously vaccinated against YF received a high dose of ChimeriVax™-DEN2 as an open-label vaccine. Most adverse events were similar to YF-VAX® and of mild to moderate intensity, with no serious side-effects. One hundred percent and 92.3% of YF naïve subjects inoculated with 5.0 and 3.0 log10 PFU of ChimeriVaxTM-DEN2, respectively, seroconverted to wt DEN2 (strain 16681); 92% of subjects inoculated with YF-VAX® seroconverted to YF 17D virus but none of YF naïve subjects inoculated with ChimeriVax-DEN2 seroconverted to YF 17D virus. Low seroconversion rates to heterologous DEN serotypes 1, 3, and 4 were observed in YF naïve subjects inoculated with either ChimeriVax™-DEN2 or YF-VAX®. In contrast, 100% of YF immune subjects inoculated with ChimeriVax™-DEN2 seroconverted to all 4 DEN serotypes. Surprisingly, levels of neutralizing antibodies to DEN 1, 2, and 3 viruses in YF immune subjects persisted after 1 year. These data demonstrated that 1) the safety and immunogenicity profile of the ChimeriVax™-DEN2 vaccine is consistent with that of YF-VAX®, and 2) pre-immunity to YF virus does not interfere with ChimeriVaxTM-DEN2 immunization, but induces a long lasting and cross neutralizing antibody response to all 4 DEN serotypes. The latter observation can have practical implications toward development of a dengue vaccine.

A Novel Tetravalent Dengue Vaccine Is Well Tolerated and Immunogenic against All 4 Serotypes in Flavivirus-Naive Adults

BACKGROUND. Sanofi Pasteur has developed a tetravalent dengue vaccine (TDV) against the worlds most common arbovirus infection. METHODS. We assessed the safety and immunogenicity of the TDV in healthy adults randomized into 2 groups. Group 1 received 3 TDV injections at months 0, 4, and 12-15; group 2 received saline placebo at month 0 and then 2 TDV injections at months 4 and 12-15. Adverse events were recorded, and biological parameters and viremia levels were measured. Neutralizing antibodies against 4 World Health Organization (WHO) reference strains were measured before and after vaccinations. RESULTS. A total of 33 participants were enrolled in each group. Demographic characteristics were comparable. No vaccine-related serious adverse event was reported. The most common systemic reactions were headache, malaise, and myalgia. Low viremia levels were detected, mainly of serotype 4. Immune response increased with successive vaccine doses. All participants seroconverted against all 4 serotypes after receiving 3 doses at 0, 4, and 12-15-months, and almost all seroconverted after 2 doses given 8-11 months apart. CONCLUSIONS. Sanofi Pasteurs TDV was well tolerated and induced full seroconversion against all WHO reference strain serotypes after 3 doses.

Live-attenuated, tetravalent dengue vaccine in children, adolescents and adults in a dengue endemic country: Randomized controlled phase I trial in the Philippines

A recombinant live attenuated tetravalent dengue vaccine (TDV) is safe and immunogenic in adults and children in dengue-naïve populations. Data are needed in dengue endemic populations. In a phase I, randomized, controlled, blind-observer study in the Philippines, groups of participants aged 2-5, 6-11, 12-17, and 18-45 years received either three TDV vaccinations at months 0, 3.5, and 12 (TDV-TDV-TDV group) or licensed typhoid vaccination at month 0 and TDV at months 3.5 and 12 (TyVi-TDV-TDV group) and were followed for safety (including biological safety and vaccine virus viremia) and immunogenicity. No serious adverse vaccine related events and no significant trends in biological safety parameters were reported. Injection site pain, headache, malaise, myalgia, fever, and asthenia were reported most frequently, as mild to moderate in most cases and transient. Reactogenicity did not increase with successive vaccinations and was no higher in children than in adults and adolescents. Low levels of vaccinal viremia were detected in both groups after each TDV vaccination. After three TDV vaccinations, the seropositivity rates against serotypes 1-4 were: 91%, 100%, 96%, 100%, respectively, in 2-5 year-olds; 88%, 96% 96%, 92% in 6-11 year-olds; 88%, 83%, 92%, 96% in adolescents; and 100% for all serotypes in adults. A similar response was observed after two doses for the TyVi-TDV-TDV group. The safety profile of TDV in a flavivirus endemic population was consistent with previous reports from flavivirus naïve populations. A vaccine regimen of either three TDV vaccinations administered over a year or two TDV vaccinations given more than 8 months apart resulted in a balanced antibody response to all four dengue serotypes in this flavivirus-exposed population, including children.

Live-attenuated Tetravalent Dengue Vaccine in Dengue-naïve Children, Adolescents, and Adults in Mexico City: Randomized Controlled Phase 1 Trial of Safety and Immunogenicity.

Background: Preliminary results in healthy, young US adults showed that a tetravalent, live-attenuated dengue vaccine (TDV) was safe and immunogenic, but no data are available in children. Methods: In a multicenter, randomized, controlled, observer-blinded study in the city of Mexico, children aged 2 to 5, 6 to 11, and 12 to 17 years (36 children per age group), and adults (n = 18) aged <45 years received the following: 3 injections of TDV at months 0, 3.5, and 12 (TDV-TDV-TDV), or 1 injection of yellow fever vaccine (YF) at month 0, and 2 injections of TDV at months 3.5 and 12 (YF-TDV-TDV). Adverse events and biologic safety (biochemistry and hematology) were documented. Plaque reduction neutralization test (PRNT50) antibody titers against the TDV parental viruses were measured 28 days after vaccination. Seropositivity was defined as antibody titers ≥10 1/dil. Results: No vaccine-related serious adverse events, other significant clinical adverse events, or clinically significant trends in biologic safety were observed. Reactogenicity did not increase with successive TDV injections, and mild-to-moderate injection site pain, headache, myalgia, and malaise were most commonly reported (14%–40% after each vaccination). After 3 TDV vaccinations, the seropositivity rate against each dengue serotype was in the range 77% to 92%, compared with 85% to 94% after completion of the YF-TDV-TDV regimen. Of the 2- to 11-year-old participants, 95% were seropositive against ≥3 serotypes after 3 vaccinations. Conclusions: A 3-dose TDV regimen had a favorable safety profile in children and adults and elicited neutralizing antibody responses against all 4 serotypes. These findings support the continued development of this vaccine.

Priming Effect of Dengue and Yellow Fever Vaccination on the Immunogenicity, Infectivity, and Safety of a Tetravalent Dengue Vaccine in Humans

A dengue vaccine effective against all four serotypes is urgently needed. However, safety and immunogenicity could be affected by prior exposure to flaviviruses. This open, controlled, phase IIa study was conducted in 35 healthy adults who had received monovalent, live attenuated Vero cell-derived dengue vaccine against dengue virus 1 (VDV1) or 2 (VDV2) or yellow fever (YF) vaccine 1 year before or who were flavivirus-naïve. All participants received one subcutaneous injection of tetravalent dengue vaccine (TDV) and were followed for 180 days. Previous vaccination did not increase reactogenicity, laboratory abnormalities, or incidence of vaccine viremia, but it did increase the neutralizing antibody response to dengue virus that persisted at day 180. There was no increase in YF antibodies in participants previously immunized with YF vaccine. Prior exposure to YF or monovalent dengue vaccines had no adverse effects on the safety or incidence of viremia associated with this TDV, but it increased immunogenicity.

Safety and Immunogenicity of Recombinant, Live Attenuated Tetravalent Dengue Vaccine (CYD- TDV) in Healthy Vietnamese Adults and Children

Background: Dengue viruses (DENV1-4) are estimated to infect 50-100 million individuals per year worldwide including an estimated 500,000 people with severe dengue who require hospitalization every year. The live, attenuated, tetravalent dengue vaccine (CYD-TDV) candidate, containing four recombinant dengue viruses (CYD1- 4), is in clinical phase III. Methods: In an observer-blind, phase II trial in Long Xuyen, Vietnam, 180 children and adults (range: 2-45 years) were randomized 2:1 to receive 3 CYD-TDV vaccinations at months (M) 0, 6 and 12 or meningococcal polysaccharide A+C at M0, placebo at M6, and typhoid Vi polysaccharide at M12. Serum antibody responses against the CYD1-4 parental wild-type dengue viruses were assessed using plaque-reduction neutralization test (PRNT50). Safety and reactogenicity were assessed using conventional methods. Febrile episodes lasting ≥ 48 h with suspicion of dengue (passive surveillance) were virologically confirmed. (ClinicalTrials.gov: NCT00875524). Results: At baseline 139(77%) were seropositive (titer ≥ 10 l/dil) against dengue or Japanese encephalitis; 36% were seropositive to all four dengue serotypes. After the first CYD-TDV vaccination, 53% were seropositive to all four serotypes, increasing to 72% and 92% after the second and third vaccinations. In the control group seropositivity against all four dengue serotypes was 28% at baseline and slightly increased at 36% after the third injection 13 months later. After the third CYD-TDV vaccination, 96% were seropositive to at least 3 serotypes, and geometric mean titers against DENV1-4 were respectively 129, 216, 169, and 146. Six serious adverse events (SAEs), unrelated to vaccination, were reported including 2 virologically-confirmed dengue cases after the second vaccination in the control group. Reactogenicity of CYD-TDV decreased after each vaccination, was slightly higher than placebo, but not higher than either active control. Conclusions: Safety and reactogenicity of CYD-TDV were satisfactory and consistent with results from phase I and other phase II studies. Three doses of CYD-TDV induced a balanced neutralizing antibody response against the four dengue serotypes in children and adults living in a dengue endemic country.

Assessment of bivalent and tetravalent dengue vaccine formulations in flavivirus-naïve adults in Mexico.

Several ChimeriVax-Dengue (CYD)-based vaccination strategies were investigated as potential alternatives to vaccination with tetravalent CYD vaccine (CYD-TDV) in this phase IIa trial conducted in 2008–9 in 150 healthy adults. Participants were randomized and vaccinated on D0 and D105 (± 15 days). One group received bivalent CYD vaccine against serotypes 1 and 3 (CYD-1;3) on day 0 and CYD-2;4 on day 105 (±15 days). Two groups received an injection at each timepoint of a tetravalent blend of CYD-1;3;4 and a VERO cell derived, live attenuated vaccine against serotype 2 (VDV-2), or the reference CYD-TDV. A fourth group received Japanese encephalitis (JE) vaccine on days -14, -7 and 0, followed by CYD-TDV on day 105. Viraemia was infrequent in all groups. CYD-4 viraemia was most frequent after tetravalent vaccination, while CYD-3 viraemia was most frequent after the first bivalent vaccination. Immunogenicity as assessed by 50% plaque reduction neutralisation test on D28 was comparable after the first injection of either tetravalent vaccine, and increased after the second injection, particularly with the blended CYD-1;3;4/ VDV-2 vaccine. In the bivalent vaccine group, immune response against serotype 3 was highest and the second injection elicited a low immune response against CYD 2 and 4. Immune responses after the first injection of CYD-TDV in the JE-primed group were in general higher than after the first injection in the other groups. All tested regimens were well tolerated without marked differences between groups. Bivalent vaccination showed no advantage in terms of immunogenicity. Clinical trial registration number: NCT00740155

Evaluation of the safety and pharmacokinetic profile of a new, pasteurized, human tetanus immunoglobulin administered as sham, postexposure prophylaxis of tetanus

ABSTRACT In a monocentric, double-blind, randomized trial, we examined the safety and pharmacokinetic profile of a new, pasteurized, human tetanus immunoglobulin (P-HTIG). As part of the purification process, P-HTIG has undergone a heat treatment step (10 h at 60°C) and the removal of Merthiolate. Forty-eight adults with a history of tetanus vaccination were randomized into four groups (n = 12 per group) to receive one of two different batches of this P-HTIG simultaneously with either tetanus-diphtheria (Td) vaccine (sham, postexposure prophylaxis of tetanus) or placebo. Local reactions at the injection site were followed for the first 3 days after injection, and systemic reactions were followed during the entire study period, i.e., up to 42 days posttreatment. Blood samples for tetanus antibody titer determination (enzyme-linked immunosorbent assay method) were drawn prior to treatment on day 0 and on days 1, 2, 3, 7, 14, 21, 28, 35, and 42. A normalization of tetanus antibody titers (subtraction of the day 0 value for each subject at each time period) was performed to assess the additive effect of P-HTIG on tetanus antibody titers. The pharmacokinetic parameters were determined by both a compartmental analysis (modelization) and a noncompartmental analysis. No severe adverse reactions were reported. The rate of local reactions at the P-HTIG injection site was 27%. All local reactions were mild and resolved within 2 days. In contrast, local reactions at the vaccine injection site were seen in 79% of the subjects. The rate of systemic reactions was similar in the P-HTIG plus Td vaccine group (33%) and in the P-HTIG plus placebo group (21%), and all these reactions were mild. In the P-HTIG plus placebo group, tetanus antibody titers rose to a maximum of 0.313 ± 2.49 IU/ml after 4.4 days; in the P-HTIG plus Td vaccine group, a maximum concentration of 15.2 ± 2.42 IU/ml was reached 19 days postinjection. In both groups, 100% of the patients had seroprotective levels of tetanus antibodies (≥0.01 IU/ml) 2 days following treatment. An anamnestic response to Td vaccine appeared 7 days postimmunization. In conclusion, P-HTIG has a good safety and pharmacokinetic profile. Our results confirm that immunoglobulin should be associated with vaccine in the treatment of tetanus-prone wounds.