A genetically modified rabies vaccine (ERAGS) induces protective immunity in dogs and cattle

Whole-Cell Vaccine Preparation: Options and Perspectives

Vaccines are biological preparations to elicit a specific immune response in individuals against the targetted microorganisms. The use of vaccines has caused the near eradication of many critical diseases and has had an everlasting impact on public health at a relatively low cost. Most of the vaccines developed today are based on techniques which were developed a long time ago. In the beginning, vaccines were prepared from tissue fluids obtained from infected animals or people, but at present, the scenario has changed with the development of vaccines from live or killed whole microorganisms and toxins or using genetic engineering approaches. Considerable efforts have been made in vaccine development, but there are still many diseases that need attention, and new technologies are being developed in vaccinology to combat them. In this chapter, we discuss different approaches for vaccine development, including the properties and preparation of whole-cell vaccines.

Generation of a recombinant rabies virus expressing green fluorescent protein for a virus neutralization antibody assay

BACKGROUND

Fluorescent antibody virus neutralization (FAVN) test is a standard assay for quantifying rabies virus-neutralizing antibody (VNA) in serum. However, a safer rabies virus (RABV) should be used in the FAVN assay. There is a need for a new method that is economical and time-saving by eliminating the immunostaining step.

OBJECTIVES

We aimed to improve the traditional FAVN method by rescuing and characterizing a new recombinant RABV expressing green fluorescent protein (GFP).

METHODS

A new recombinant RABV expressing GFP designated as ERAGS-GFP was rescued using a reverse genetic system. Immuno-fluorescence assay, peroxidase-linked assay, electron microscopy and reverse transcription polymerase chain reaction were performed to confirm the recombinant ERAGS-GFP virus as a RABV expressing the GFP gene. The safety of ERAGS-GFP was evaluated in 4-week-old mice. The rabies VNA titers were measured and compared with conventional FAVN and FAVN-GFP tests using VERO cells.

RESULTS

The virus propagated in VERO cells was confirmed as RABV expressing GFP. The ERAGS-GFP showed the highest titer (10^8.0 TCID₅₀/mL) in VERO cells at 5 days post-inoculation, and GFP expression persisted until passage 30. The body weight of 4-week-old mice inoculated intracranially with ERAGS-GFP continued to increase and the survival rate was 100%. In 62 dog sera, the FAVN-GFP result was significantly correlated with that of conventional FAVN (r = 0.95).

CONCLUSIONS

We constructed ERAGS-GFP, which could replace the challenge virus standard-11 strain used in FAVN test.

Strategies to maintain Korea's animal rabies non-occurrence status

Endemic animal rabies causes >99% of all human rabies cases; elimination of animal rabies reduces the rate of human infections. The most recent animal rabies cases in the Gangwon and Gyeonggi provinces of Korea occurred in November 2012 and February 2013, respectively. Here we explore ways to ensure that Korea remains animal rabies non-occurrence. The government must prevent rabies recurrence by vaccinating dogs, distributing bait vaccine in regions with a high rabies risk, performing laboratory-based surveillance, preventing the flow of rabies-suspect animals from neighboring countries, and enhancing border quarantine. As has already been shown in several developed countries, careful and ongoing rabies control will allow Korea to remain animal rabies-free.