As vectors of both parasitic and viral diseases, endemic mosquito populations are a global concern. In Africa, mosquitoes contribute to at least one million deaths each year and, here in the United States, mosquito-borne diseases are also on the rise. Strategies for mitigating transmission of these diseases require the use of insecticides but conventionally applied agents lack specificity and lose efficacy as resistance inevitably emerges. Consequently, there is an urgent need to develop new agents that are narrowly targeted, environmentally harmless and safe to humans. Traditional searches for new insecticides involve whole animal screening but, unfortunately, these approaches sample compounds on very limited scales and lack environmental safety tests early in the pipeline. Furthermore, rationale design principles commonly leveraged for drug development programs have not been routinely exploited for pesticide development.
To address these limitations, we recently conducted a pilot study to test the feasibility of an alternative discovery platform. Specifically, we examined whether cell-based screens and counterscreens could be leveraged as a surrogate to identify targeted, vector-specific toxins when tested in whole animals. Towards this goal, we designed a high throughput platform that systematically searches for compounds that are lethal to cultured mosquito cells but show negligible activity against human, rodent or other insect cell lines.
Our strategy captured a rare set of compounds that specifically killed mosquito cells and, importantly, targeted killing in culture was associated with selective toxicities in whole animal assays.
Furthermore, where tested, strains resistant to a commonly used insecticide (pyrethroid) were also susceptible. Taken together, our results demonstrate that capabilities enabled by this platform dramatically outperform whole animals screens and can expose untapped mosquito-specific vulnerabilities.
We are now capitalizing on this proof-of-concept to deliver the most potent and most selective mosquitocides obtainable from massive chemical and natural product libraries. A successful precedent here could inspire similar efforts to develop customized pesticides that target other disease vectors as well.