4.2 Multiplicity of Infection (MOI) of Baculovirus Vectors
In the IC-BEVS, the MOI of the baculovirus has a critical impact on the
rate of cell growth and viability, the production kinetics, the quantity
and quality of the recombinant protein expressed, and the harvest time
of the culture. The low and high MOI infections are characterized by
their different rate of infection (synchronous Vs. asynchronous) and the
associated difference in kinetics of protein expression. Expression of
viral vector or virus-like particles, which typically involve
co-infecting cell cultures with more than one rBV carrying the coding
sequences of individual components adds another complexity to the
production process [51], [52]. Altering the MOI of multiple
baculoviruses and their time of infection often result in altered capsid
compositions as reported by various groups[53], [54]. AAV
production using triple baculovirus co-infection strategy is also an
example of such a complex and dynamic system where primary work has
relied on multicomponent system. Initial studies by Meghrous et al.
demonstrated the effect of Bac-Rep on overall Sf9 growth behavior and
AAV vector yield using Three-Bac system and its association with
encapsidation of vector DNA, and the transducing particle units[48].
The Bac-Rep showed no notable effect on cell viability and growth
behavior irrespective of MOI used. The study focused on the
multidimensional interactive effect of multiple baculoviruses, each
expressing an essential protein of rAAV, suggested a significant effect
of Bac-Rep and Bac-Cap MOI on packaging efficiency and functional AAV
particles. A full factorial study conducted by Aucoin et al. provided an
in-depth analysis of single factor and multifactorial interaction
effects of MOI of the three baculoviruses on AAV yields [55]. This
study also suggested a self-sustaining nature of insect cell-baculovirus
infection process, where differing MOI of one baculovirus did not lead
to the drastic changes in overall AAV yield when expressed collectively
as relative proportions of total, genome containing and functional
particles.