4.2 Plant-Made Antibodies and Immunotherapy of Infectious
Diseases
Numerous mAbs have shown the potential to treat infectious diseases targeting
microbial infections by directly interacting with key epitopes and/or harnessing the
immune response.
Among anti-infectious mAbs, the human mAb 2G12, recognizing a distinctive
neutralizing epitope on the GP120 envelope protein of HIV-1, has a potent and broad
HIV-1-neutralizing activity in vitro and in vivo (Hessell et al. 2009). Due to these
properties, mAb 2G12 has been chosen by Pharma-Planta Consortium (http://www.
pharma-planta.net) as the best candidate to be produced in plants under GMP
conditions for the first in-human, double-blind, placebo-controlled, randomized,
dose-escalation, phase I clinical trial (Ma et al. 2015). This mAb, representing a
significant milestone in the commercial development of plant-derived biologics, has
been produced by several expression systems and transgenic hosts (i.e. tobacco,
maize and Arabidopsis) as well as in plant cell systems. However, the production of
this mAb in transient expression systems was far superior to that obtained by stable
transgenics in terms of yield and speed of expression. In particular, the highest yield
of purified mAb (105 mg/kg fresh weight tissue) was obtained through the CPMVHT system and retention in the ER (Sainsbury et al. 2010). In addition, binding and
neutralization properties of plant-produced 2G12 with the “humanized” N-glycans
were equivalent to that of the original mAb derived from CHO cells, being even
more effective in virus neutralization.
Finally, a sIgA version of 2G12 has been produced in both transgenic N. tabacum
and transiently transformed N. benthamiana (Paul et al. 2014) demonstrating effective aggregation of HIV virions and enhanced stability in mucosal secretions, when
compared to the cognate IgG format.
A further antiviral mAb expressed in plants is the Hu-E16, a humanized mAb
that binds an epitope on the envelope protein (domain III of GP-E) of West Nile
virus (WNV) (Oliphant et al. 2005). Using both the MagnICON system and a
geminivirus-based vector, codon-optimized HC and LC encoding sequences, high
level of production ($260/800 and mg per kilogram of fresh weight) has been
achieved in N. benthamiana and lettuce (Lai et al. 2010, 2012).
Further efforts have been made to improve Hu-E16 mAb efficacy, engineering
diverse modified formats to be transiently expressed in both wild-type and glycoengineered XT/FT N. benthamiana (He et al. 2014; Lai et al. 2014). Overall data
demonstrate that plant-made Hu-E16 show in mice a strong neutralizing activity and
induced pre- and post-exposure protection, equivalently to what has been observed
with Hu-E16 derived from mammalian cell, possibly transforming this preclinical
candidate into a cost-effective therapeutic of medical and veterinary significance
against WNV.
Most current experimental therapies against Ebola virus (EBOV) are addressed to
the principal virulence factor GP, a transmembrane protein triggering virus host cell
entry and exerting cytopathic effects in infected cells (Lee et al. 2008; Simmons et al.
2002) while inducing protective antibodies (Wilson et al. 2000). At the moment,
Engineering Plants for the Future: Farming with Value-Added Harvest
87
Diseases
Numerous mAbs have shown the potential to treat infectious diseases targeting
microbial infections by directly interacting with key epitopes and/or harnessing the
immune response.
Among anti-infectious mAbs, the human mAb 2G12, recognizing a distinctive
neutralizing epitope on the GP120 envelope protein of HIV-1, has a potent and broad
HIV-1-neutralizing activity in vitro and in vivo (Hessell et al. 2009). Due to these
properties, mAb 2G12 has been chosen by Pharma-Planta Consortium (http://www.
pharma-planta.net) as the best candidate to be produced in plants under GMP
conditions for the first in-human, double-blind, placebo-controlled, randomized,
dose-escalation, phase I clinical trial (Ma et al. 2015). This mAb, representing a
significant milestone in the commercial development of plant-derived biologics, has
been produced by several expression systems and transgenic hosts (i.e. tobacco,
maize and Arabidopsis) as well as in plant cell systems. However, the production of
this mAb in transient expression systems was far superior to that obtained by stable
transgenics in terms of yield and speed of expression. In particular, the highest yield
of purified mAb (105 mg/kg fresh weight tissue) was obtained through the CPMVHT system and retention in the ER (Sainsbury et al. 2010). In addition, binding and
neutralization properties of plant-produced 2G12 with the “humanized” N-glycans
were equivalent to that of the original mAb derived from CHO cells, being even
more effective in virus neutralization.
Finally, a sIgA version of 2G12 has been produced in both transgenic N. tabacum
and transiently transformed N. benthamiana (Paul et al. 2014) demonstrating effective aggregation of HIV virions and enhanced stability in mucosal secretions, when
compared to the cognate IgG format.
A further antiviral mAb expressed in plants is the Hu-E16, a humanized mAb
that binds an epitope on the envelope protein (domain III of GP-E) of West Nile
virus (WNV) (Oliphant et al. 2005). Using both the MagnICON system and a
geminivirus-based vector, codon-optimized HC and LC encoding sequences, high
level of production ($260/800 and mg per kilogram of fresh weight) has been
achieved in N. benthamiana and lettuce (Lai et al. 2010, 2012).
Further efforts have been made to improve Hu-E16 mAb efficacy, engineering
diverse modified formats to be transiently expressed in both wild-type and glycoengineered XT/FT N. benthamiana (He et al. 2014; Lai et al. 2014). Overall data
demonstrate that plant-made Hu-E16 show in mice a strong neutralizing activity and
induced pre- and post-exposure protection, equivalently to what has been observed
with Hu-E16 derived from mammalian cell, possibly transforming this preclinical
candidate into a cost-effective therapeutic of medical and veterinary significance
against WNV.
Most current experimental therapies against Ebola virus (EBOV) are addressed to
the principal virulence factor GP, a transmembrane protein triggering virus host cell
entry and exerting cytopathic effects in infected cells (Lee et al. 2008; Simmons et al.
2002) while inducing protective antibodies (Wilson et al. 2000). At the moment,
Engineering Plants for the Future: Farming with Value-Added Harvest
87