Immunization against rabies with plant-derived antigen

Abstract

We previously demonstrated that recombinant plant virus particles containing a chimeric peptide representing two rabies virus epitopes stimulate virus neutralizing antibody synthesis in immunized mice. We show here that mice immunized intraperitoneally or orally (by gastric intubation or by feeding on virus-infected spinach leaves) with engineered plant virus particles containing rabies antigen mount a local and systemic immune response. After the third dose of antigen, given intraperitoneally, 40% of the mice were protected against challenge infection with a lethal dose of rabies virus. Oral administration of the antigen stimulated serum IgG and IgA synthesis and ameliorated the clinical signs caused by intranasal infection with an attenuated rabies virus strain.

Figure 1

Rabies virus-specific serum antibody (IgG) response of mice immunized i.p. with CPDrg24. Serum antibody responses were measured by ELISA on plates coated with ERA strain rabies virus. Bars represent mean values obtained using preimmune and sera after each inoculation of antigen. A serum dilution of 1:160 was used. CPDrg24–1, -2, and -3 indicate the serum antibody response observed after the first, second, and third immunizations, respectively. A/TMV-1, -2, and -3 represent rabies-specific serum antibody responses from control-immunized mice (AIMV plus TMV).

Figure 2

Rabies- and AIMV-specific serum antibody (IgG and IgA) response of mice immunized with CPDrg24 orally by gastric intubation. Rabies-specific and AIMV-specific serum antibody responses were measured by ELISA on plates coated with a synthetic peptide resembling the linear epitope (G5–24) of rabies virus glycoprotein and on plates coated with the AIMV CP, respectively. Data represent averages obtained using preimmune and sera after the last (fourth) administration of antigen. (A and B) Serum IgG and IgA response specific for the rabies, respectively; (C and D) Serum IgG and IgA response specific for the carrier molecule AIMV CP.

Figure 3

Rabies virus-specific IgA response in supernatants of fecal pellets from mice immunized with CPDrg24 orally by (A) gastric intubation or (B) by feeding on fresh spinach leaves. Rabies-specific antibody responses were measured by ELISA on plates coated with synthetic peptide resembling the linear epitope of rabies virus glycoprotein. Data represent mean values obtained using preimmune and supernatants of fecal pellets after the last (fourth) administration of the antigen.

Figure 4

Weight loss in mice immunized orally with CPDrg24 and challenged with CVS-F3 strain rabies virus. Data represent mean percent daily weight loss in mice (10 per group) immunized with CPDrg24 or control (A/TMV). Percent daily weight loss of mice immunized by (A) gastric intubation and (B) by feeding on spinach leaves.