An evaluation of an indirect Enzyme-linked immunosorbent assay and SDS-PAGE, western blot transfer techniques to detect rabies virus antibodies in canine sera

Abstract

An indirect Enzyme-linked immunosorbent assay (ELISA) was developed to screen dog serum for antirabies antibodies after vaccination and after exposure to a live rabies street virus. All ELISA results were compared to Rapid Fluorescent Focus Inhibition Test (RFFIT) as a control method. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), western blot technology was investigated as a possible alternative to post mortem examination to diagnose rabies infections. Two groups of dogs were used as test animals. The first group was the vaccine control group. This group of dogs was given a series of intramuscular inoculations of killed rabies vaccine. The second test group was the street virus control dogs. These dogs were given a lethal dose of Mexican dog strain live rabies virus. If the animal survived the challenge and lived for 60 days it was euthanized. All dogs with prodromal signs of rabies were fluorescent antibody (FA) positive. Three different conjugates were tested to determine whether IgG and IgM class antibodies could be differentiated. There was 97.8% correlation with the RFFIT using the IgG (gamma chain specific) conjugate and 88% correlation using the IgG (H&L chain) conjugate. Sero-conversion in dogs was studied for the first time using ELISA and results indicate that the dogs showed a response at 7 days with a vaccine stimulation and at 5 days with a street virus stimulation. The SDS-PAGE, western blot technique was done for the first time using rabies virus and dog antiserum to determine the type of antibodies that were produced in response to a vaccination or challenge with rabies street virus. The antiserum from a street virus infected dog was more reactive with the homologous antigens than it was with the heterologous vaccine virus. The present research has shown that the indirect ELISA can be used to screen dog serum for antirabies antibodies. The ELISA can be used to detect antibodies from street virus infections and is more sensitive in detecting the antibodies than the RFFIT. The SDS-PAGE, western blots can be used to differentiate the antibody response to vaccine virus and to street virus.