Laboratory and field assays are essential for the evaluation of efficacy of transmission-blocking vaccines (TBVs) and for rational decision-making. However, determining the minimum level of TBV efficacy necessary to reduce transmission and subsequently eliminate malaria is difficult. Assessment of TBV efficacy is compounded by large variability between laboratory and field assays.
In addition, reduced mosquito infection, observed in the absence of a complete blocking effect, is unlikely to translate into a similar level of reduction at the population level in the field. Given these factors, MVI is supporting work in two targeted areas. MVI is investing in efforts to bridge field and laboratory assays to better understand the TBV efficacy levels required to achieve elimination in different transmission settings. In addition, MVI is supporting a laboratory-based effort for predicting TBV efficacy. This “Population Transmission Assay” uses the mouse model, developed by Robert Sinden at Imperial College London, and this may be used to provide information on the appropriate target efficacy necessary to reduce transmission in different malaria endemicities and guide TBV product development. A current study involves five successive rounds of mouse-to-mosquito-to-mouse infections with P. berghei within the context of several simulated transmission levels. The study also involves treatment of mice by administration of a transmission-blocking drug [Atovaquone (ATV)] or monoclonal antibodies (mAbs) against sexual stages or sporozoites via passive transfer to assess the potential for transmission interruption in subsequent cycles.