Chloroplast-Derived Vaccine Against Orthopoxviruses

Orthopoxviruses (OPVs) resurfaced in headlines recently because of zoonotic (transfer of disease-causing materials from animals to humans) outbreaks in the U.S. and Africa and their potential use in bioterrorism. Member of the OPV genus include the dreaded smallpox virus, monkeypox virus and myxoma virus in rabbits. These outbreaks have brought increased attention for the development of new-generation vaccines against smallpox and related viruses. Although an effective vaccine against smallpox exists, it has a wide range of contraindications. Its stockpiles are also low , since production has ceased in the 1980s. A team of researchers from Italy investigated the feasibility of producing smallpox vaccine, using the A27L immunogenic protein of vaccinia virus, in plant cells.

Manuela Rigano and colleagues specifically targeted the expression of the A27L protein in the chloroplasts. The recombinant protein accumulated to about 18 percent of the total soluble protein (or 1.7 mg/g fresh weight). According to the researchers, this is 500-fold higher than that in nuclear transformed plants. The recombinant A27L formed oligomers, suggesting correct folding and quaternary structure. It was also shown to be stable over a wide range of pH values. Serum from patients with zoonotic OPV infections recognized the chloroplast-derived A27L protein.

 The paper published by the Plant Biotechnology Journal is available at http://dx.doi.org/10.1111/j.1467-7652.2009.00425.x