Immunization with pTyIrHA

It has been shown that pHKHA provides immunity against both HK97 and an antigenic variant CkHK97, but can a DNA vaccine encoding the HA of an antigenic variant provide protection against HK97?

Methods

Mice were immunized with pTyIrHA via gene gun delivery of DNA: the plasmid DNA was affixed to 2.6mm gold beads, the DNA-coated gold particles (1mg) were then delivered into shaved abdominal areas of mice using a helium pulse gene gun. After 4 weeks, the mice were given a booster of the same dose. Ten days after receiving the boosters, the mice were challenged with 10-100mL 50% lethal doses (LD₅₀) of either HK97 or CkHK97, intranasally. The mice were observed daily for clinical signs, weight loss and mortality. On the fifth day postinfection, samples were taken for virus replication. (Serum samples were collected prebooster, prechallenge, and 10 days postchallenge for antibody analyses)

Results

Table 2. Protection against lethal H5N1 virus challenge induced from DNA encoding HA from TyIr83

Questions to Ponder

• Did pTyIrHA provide total immunity against HK97? yes incorrect: Although the vaccine prevented death from HK97, the mice did show signs of infection after challenge and had significant amounts of virus in their lungs. However, in immunized mice, there was no replication of the virus in the brain. These mice also lost 10% of their body weight by day 5 postchallenge (when compared to controls this is not significant) no Correct! The virus was able to infect mice, however the effects of infection were minimal (see 'yes' answer)
• Why was it important to demonstrate the ability to provide immunity to HK97 using DNA encoding HA from an antigenic variant strain? answer An emerging pandemic may not allow time for making a DNA vaccine that encodes the genetically matched HA. pTyIrHA was used to determine whether immunization with an antigenic variant could offer sufficient protection until a genetically matched HA DNA vaccine could be produced.

return to list of experiments