Table 2.

Main antigens recently expressed as viral virus-like particles (VLPs).

VLP Antigen/Virus	Plant Host	Transformation Method and Yields	Immunization Scheme	Findings	Reference
D antigen (PV3)/Poliovirus	N. benthamiana	Transient expression by transformation with A. tumefaciens method. Yields: 60 mg/kg of infiltrated plant tissue.	Mice received one or two intraperitoneal injections of 0.5 human doses of purified VLPs and were challenged with poliovirus.	VLPs in one and two doses induced similar levels of neutralizing antibodies and protection against a viral challenge.	[45]
CP/PCV-2	N. benthamiana	Transient expression by transformation with A. tumefaciens method. Yields: 6.5 mg/kg of leaf wet weight.	Mice received 3 subcutaneous injections of 10–20 μg VLPs.	VLPs induced specific antibodies for PCV-2 at 42 days post-immunization.	[53]
H1, H5/Influenza virus	N. benthamiana	Transient expression by transformation with A. tumefaciens method. Yields: not reported.	Not applied	VLPs mimic the structure and initial virus-APC interaction of influenza virions.	[54]
H1, H5/Influenza virus	N. benthamiana	Transient expression by transformation with A. tumefaciens method. Yields: not reported.	Not applied	VLPs were structurally similar and stable for at least one year at 4 °C, interacted with and activated APCs analogous to influenza virions	[55]
VP2,VP3,VP5,VP7/African horse sickness virus (AHSV)	N. benthamiana	Transient expression by transformation with A. tumefaciens method. Yields: Not reported	Intramuscular immunization of horses with 200 μg or 100 μg total VLPs protein plus Pet Gel A adjuvant	All immunized horses showed specific antibodies after the second dose. However, those that received the highest dose had higher neutralizing titers.	[56]
VP6/(RVs) GI.4,GII.4-2006a/(NoVs)	N. benthamiana	Transient expression by transformation with A. tumefaciens method. Yields: Not reported	Mice received intradermally 0.3 µg three times or 1 µg of GI.4 and GII.4-2006a VLPs combined with 10 µg of VP6.	VP6 had an adjuvant effect in the production of antibodies against NoV VLPs.	[57]
VP0, VP1, VP3/FMD	N. benthamiana	Transformation with A. tumefaciens method. Yields: ∼0.030 μg/g of fresh leaf material.	Mice were immunized subcutaneously four times with 5 μg VLPs plus Montanide ISA 50 V 2 (Seppic) adjuvant.	→The VLPs produced in plants were assembled without the need for the 3C protease precursor, in comparison with those expressed in other platforms, such as mammalian and insect cells. →VLPs were significantly immunogenic in mice.	[44]

Abbreviations; VLP: virus-like particles; APC: antigen-presenting cells; FMD: Foot-and-mouth disease; RV: rotaviruses; NoVs: noroviruses; AHSV: African horse sickness virus; H1: hemagglutinin (A/California/07/2009 (H1N1)); H5: hemagglutinin (A/Indonesia/05/2005 (H5N1)); PCV-2: Porcine circovirus type 2; CP: capsid protein.