Tetravalent dengue DNA vaccine is not immunogenic when delivered by retrograde infusion into salivary glands

Introduction and background

A tetravalent DNA vaccine for Dengue virus is under development but has not yet achieved optimal immunogenicity. Salivary glands vaccination has been reported efficacious in rodents and dogs. We report on a pilot study testing the salivary gland as a platform for a Dengue DNA vaccine in a non-human primate model.

Materials and methods

Four cynomolgus macaques were used in this study. Each macaque was pre-medicated with atropine and sedated with ketamine. Stensen’s duct papilla was cannulated with a P10 polyethylene tube, linked to a 500ul syringe. On the first two infusions, all macaques were infused with 300ul of TVDV mixed with 2 mg of zinc. For the 3rd infusion, to increase transfection into salivary tissue, two animals received 100uL TVDV mixed with 400uL polyethylenimine 1μg/ml (PEI) and the other two animals received 500uL TVDV with zinc. Antibody titers were assessed 4 weeks following the second and third infusion.

Results and conclusions

SGRI through Stensen’s duct is a well-tolerated, simple and easy to reproduce procedure. TVDV infused into macaques salivary glands elicited a significantly weaker antibody response than with different delivery methods.

Incidence rates of neurotropic-like and viscerotropic-like disease in three dengue-endemic countries: Mexico, Brazil, and Malaysia

BACKGROUND

The background incidence of viscerotropic- (VLD) and neurotropic-like disease (NLD) unrelated to immunization in dengue-endemic countries is currently unknown.

METHODS

This retrospective population-based analysis estimated crude and standardized incidences of VLD and NLD in twelve hospitals in Brazil (n = 3), Mexico (n = 3), and Malaysia (n = 6) over a 1-year period before the introduction of the tetravalent dengue vaccine. Catchment areas were estimated using publicly available population census information and administrative data. The denominator population for incidence rates was calculated, and sensitivity analyses assessed the impact of important assumptions.

RESULTS

Total cases adjudicated as definite VLD were 5, 57, and 56 in Brazil, Mexico, and Malaysia, respectively. Total cases adjudicated as definite NLD were 103, 29, and 26 in Brazil, Mexico, and Malaysia, respectively. Crude incidence rates of cases adjudicated as definite VLD in Brazil, Mexico, and Malaysia were 1.17, 2.60, and 1.48 per 100,000 person-years, respectively. Crude incidence rates of cases adjudicated as definite NLD in Brazil, Mexico, and Malaysia were 4.45, 1.32, and 0.69 per 100,000 person-years, respectively.

CONCLUSIONS

Background incidence estimates of VLD and NLD obtained in Mexico, Brazil, and Malaysia could provide context for cases occurring after the introduction of the tetravalent dengue vaccine.

Elaboration of tetravalent antibody responses against dengue viruses using a subunit vaccine comprised of a single consensus dengue envelope sequence

Dengue viruses (DENVs) are re-emerging pathogens transmitted by mosquitoes mainly in tropical and subtropical regions. Each year, they are estimated to infect 390 million people globally. The major challenge confronting dengue vaccine development is the need to induce balanced, long lasting tetravalent immune responses against four co-circulating virus serotypes (DENV-I, -II, -III, -IV), because primary infection by any one of which may predispose infected individuals to more severe diseases during a heterotypic secondary infection. Another difficulty is to select representative strains in vaccine design to provide cross-protection against most circulating virus strains. In this study, aimed at developing a tetravalent subunit vaccine with a representative single protein, we designed two vaccines (named cE80(D4) and cE80(max)) based on the consensus sequences of the ectodomain of envelope protein of 3127 DENV strains, and then expressed them in the baculovirus expression system. Both vaccines were capable of eliciting specific antibodies against all four DENV serotypes, and the predominant IgG subtype elicited by the two vaccines was IgG1. Moreover, these vaccines activated both type I and type II antigen-specific helper T cells that secreted IFN-γ and IL-4, respectively. This proof-of-concept study has set foundation for further optimization of a single protein-based tetravalent DENV vaccine.

Estimation of parameters related to vaccine efficacy and dengue transmission from two large phase III studies

BACKGROUND

A tetravalent dengue vaccine was shown to be efficacious against symptomatic dengue in two phase III efficacy studies performed in five Asian and five Latin American countries. The objective here was to estimate key parameters of a dengue transmission model using the data collected during these studies.

METHODS

Parameter estimation was based on a Sequential Monte Carlo approach and used a cohort version of the transmission model. Serotype-specific basic reproduction numbers were derived for each country. Parameters related to serotype interactions included duration of cross-protection and level of cross-enhancement characterized by differences in symptomaticity for primary, secondary and post-secondary infections. We tested several vaccine efficacy profiles and simulated the evolution of vaccine efficacy over time for the scenarios providing the best fit to the data.

RESULTS

Two reference scenarios were identified. The first included temporary cross-protection and the second combined cross-protection and cross-enhancement upon wild-type infection and following vaccination. Both scenarios were associated with differences in efficacy by serotype, higher efficacy for pre-exposed subjects and against severe dengue, increase in efficacy with doses for naïve subjects and by a more important waning of vaccine protection for subjects when naïve than when pre-exposed. Over 20 years, the median reduction of dengue risk induced by the direct protection conferred by the vaccine ranged from 24% to 47% according to country for the first scenario and from 34% to 54% for the second.

CONCLUSION

Our study is an important first step in deriving a general framework that combines disease dynamics and mechanisms of vaccine protection that could be used to assess the impact of vaccination at a population level.

Clinical evaluation strategies for a live attenuated tetravalent dengue vaccine

Butantan Institute is a public Brazilian biomedical research-manufacturer center affiliated to the São Paulo State Secretary of Health. Currently, Butantan is one of the main public producers of vaccines, antivenoms, and antitoxins in Latin America. The partnership between Butantan and the National Institutes of Health (NIH) of the United Sates has been one of the longest and most successful partnerships in the development and manufacturing of new vaccines. Recently, Butantan Institute has developed and manufactured a lyophilized tetravalent live attenuated dengue vaccine with the four dengue viruses attenuated and licensed from the Laboratory of Infectious Diseases at The National Institutes of Allergy and Infectious Diseases (LID/NIAID/NIH). The objective of this paper is to describe the clinical evaluation strategies of a live attenuated tetravalent dengue vaccine (Butantan-DV) developed and manufactured by Butantan Institute. These clinical strategies will be used to evaluate the Butantan-DV Phase III trial to support the Butantan-DV licensure for protection against any symptomatic dengue caused by any serotype in people aged 2 to 59 years.