Genetic Vaccination againstCoccidioides immitis: Comparison of Vaccine Efficacy of Recombinant Antigen 2 and Antigen 2 cDNA

Abstract

Previous studies from our laboratory established that C-ASWS, an alkali-soluble, water-soluble extract from cell walls ofCoccidioides immitis, protects mice against lethal challenge with this fungus. The C-ASWS extract contains a glycosylated protein, designated antigen 2 (Ag2), and a polysaccharide antigen. We recently cloned Ag2 cDNA and showed that the recombinant fusion protein elicited strong delayed-type hypersensitivity responses in immunized mice. This investigation was undertaken to determine if the recombinant Ag2 protein, expressed as an Ag2-glutathione S-transferase (GST) fusion protein, or Ag2 cDNA would protect mice against lethal challenge with C. immitis. The recombinant Ag2-GST protein protected BALB/c mice against intraperitoneal challenge with 250 arthroconidia, as assessed by a decrease in fungal CFU in tissues. The Ag2-GST-immunized mice did not show, however, an increased survival during a 30-day period postinfection. By contrast, immunization of mice with Ag2 cDNA ligated into the pVR1012 plasmid engendered protection against intraperitoneal challenge with 2,500 arthroconidia and against pulmonary challenge with 50 arthroconidia. Vaccine efficacy paralleled the development of delayed-type hypersensitivity responses to C. immitis antigen. Whereas mice vaccinated with the recombinant Ag2-GST protein did not mount footpad hypersensitivity to C-ASWS or the recombinant Ag2-GST protein, mice vaccinated with the pVR1012-Ag2 construct mounted a strong footpad hypersensitivity and their spleen cells secreted gamma interferon upon in vitro stimulation with the Ag2-containing C-ASWS extract. This is the first investigation to show that genetic immunization can protect against lethal challenge withC. immitis.

Coadministration of Interleukin 12 Expression Vector with Antigen 2 cDNA Enhances Induction of Protective Immunity againstCoccidioides immitis

“…1. Consistent with our earlier investigation (20), mice vaccinated with Ag2 cDNA showed a significant reduction in the fungal load in their lungs (P Ͻ 0.0001), livers (P Ͻ 0.0001), and spleens (P Ͻ 0.0001) compared to mice vaccinated with the pVR1012 vector alone. Mice vaccinated with both IL-12 cDNA and Ag2 cDNA were even more protected.…”

“…Investigations by us (26) and others (25,33) showed that the protective component resided in the cell walls and that cell wall extracts, enriched in antigen 2 (Ag2), induced protection against challenge with C. immitis. We recently cloned the gene that encodes Ag2 (47,48) and showed that immunization of mice with the Ag2 gene induced protection against intraperitoneal challenge with 2,500 arthroconidia of C. immitis (20). Our results were corroborated in a recent study by Abuodeh et al (1), who reported on the protective capacity of a gene which encodes a proline-rich antigen.…”

Experimental Animal Models of Coccidioidomycosis

“…68 With advances in laboratory technology, vaccine preparations for prevention of coccidioidomycosis have focused on subcellular and more recently to specifically cloned antigens, as well as improved ways to present the antigens, the use of engineered chimeric proteins and different adjuvants, many of which have shown some protective activity. 34,56,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83] These studies have primarily used mouse models of infection and have been performed by pretreatment of the mice with the vaccine preparation, usually multiple doses given subcutaneously, intramuscularly, or intraperitoneally, and challenged by intraperitoneal or pulmonary route 2 to 4 weeks later. Evaluation of protection is then based on prolonged survival and in some studies on the number of CFUs of Coccidioides remaining in the target organs (e.g., lungs).…”

Safety, Antigenicity, and Efficacy of a Recombinant Coccidioidomycosis Vaccine in Cynomolgus Macaques (Macaca fascicularis)

“…The recombinant protein was shown to elicit a protective response when used as a vaccine in the mouse model. [6][7][8][9][10] A truncated Ag2/PRA construct containing only amino acids 1-106 (Ag2/PRA106) was found to retain the efficacy of the full-length protein. A second recombinant antigen, the Coccidioides-specific antigen (CSA) was protective against intraperitoneal (IP) infection but less effective against intranasal (IN) challenge.…”