Phase I clinical evaluation of rDEN4Delta30-200,201: a live attenuated dengue 4 vaccine candidate designed for decreased hepatotoxicity.

The rDEN4Delta30-200,201 is a live attenuated DENV-4 vaccine candidate specifically designed to further attenuate the rDEN4Delta30 parent virus. In the present study, 28 healthy adult volunteers were randomized to receive either 10(5) plaque-forming unit (PFU) of vaccine (20) or placebo (8) as a single subcutaneous injection. Volunteers were evaluated for safety every other day for 16 days. Serum neutralizing antibody titer against DEN4 was determined at study day 28, 42, and 180. The vaccine infected all vaccinees and was well tolerated without inducing alanine aminotransferase (ALT) elevations. Although virus was not recovered from the serum of any vaccinee, moderate levels of neutralizing antibody were induced in all volunteers. Thus the restricted replication of rDEN4Delta30-200,201 previously documented in animal models was confirmed in humans. The rDEN4Delta30-200,201 is a promising candidate and can be considered for inclusion in a tetravalent dengue virus (DENV) vaccine.

rDEN2/4Delta30(ME), a live attenuated chimeric dengue serotype 2 vaccine is safe and highly immunogenic in healthy dengue-naïve adults.

rDEN2/4Delta30(ME) is an attenuated chimeric dengue virus in which the prM and E structural proteins of the DEN4 candidate vaccine rDEN4Delta30 have been replaced by those of the prototypic DEN2 NGC virus. rDEN2/4Delta30(ME) was evaluated at a dose of 1,000 PFU in 20 healthy dengue-naïve adult volunteers. Eight volunteers received placebo. Volunteers were monitored closely for adverse events and serum was collected for determination of the level and duration of viremia and neutralizing antibody response. The vaccine was well tolerated by all volunteers. The most common adverse events observed were a transient asymptomatic rash and mild neutropenia. All vaccines seroconverted to DEN2 and maintained significant antibody titers throughout the six-month trial duration. Eleven vaccinees had vaccine virus recovered from the blood during the study. RNA derived from virus isolates obtained from viremic volunteers was sequenced for confirmation of retention of the Delta30 mutation in the 3' UTR. The Delta30 mutation remained unchanged in each isolate, confirming the stability of the Delta30 mutation. Further evaluation of this vaccine in a tetravalent formulation is warranted.

The live attenuated dengue serotype 1 vaccine rDEN1Delta30 is safe and highly immunogenic in healthy adult volunteers.

BACKGROUND: The live attenuated DEN1 vaccine candidate virus rDEN1Delta30 has been evaluated in preclinical animal models and found to be attenuated and immunogenic. These promising preclinical studies have identified rDEN1Delta30 as a candidate DEN1 vaccine virus for further testing in a human Phase I clinical trial. METHODS: rDEN1Delta30 at a dose of 10(3) pfu was administered as a single inoculation to twenty healthy adult volunteers. Eight additional volunteers received placebo. Volunteers were monitored closely for adverse events and serum was collected on study days 0, 28, 42 and 180 for determination of neutralizing antibody titer. RESULTS: The vaccine was well tolerated by the vaccinees. The most common adverse events observed were a transient asymptomatic rash in 40% of vaccinees and a mild neutropenia in 45% of vaccinees. No vaccinee developed a dengue-like illness. The vaccine was highly infectious and immunogenic with 95% of vaccinees developing a > or =4-fold rise in serum neutralizing antibody titer against DEN1 that persisted throughout the six month duration of the trial. CONCLUSIONS: The rDEN1Delta30 vaccine is safe and induced a potent and durable antibody response against DEN1. It is a promising vaccine candidate for inclusion in a tetravalent dengue vaccine formulation.