Factors Triggering Plasmodium Development Following Anopheles Salivary Gland Invasion

Malaria parasites undergo a sequential series of developmental changes as they traverse and invade various tissues of both vertebrate and invertebrate hosts. These developmental changes are reflected in the parasites??? morphology, infectivity, gene expression patterns, as well as levels. Midgut and hemolymph sporozoites are completely different from those of salivary gland ones in that they are less capable for infecting their hosts and are less motile. The mosquito factors triggering those developmental changes during, and post salivary gland invasion are largely unknown. To identify and characterise mosquito factors that trigger those essential developmental changes in Plasmodium berghei and strengthen sporozoite development to infect their mammalian host, a UIS4:mCherry-containing line of P. berghei (PbANKA-Cherry-2204c1) that only has visible mCherry expression following salivary gland invasion, was treated in vitro with adult female mosquito tissue homogenates. The data obtained from using female Anopheles stephensi salivary gland homogenate shows the expression of mCherry protein as red fluorescence in about 70% of treated sporozoites in vitro. Anopheles stephensi midgut homogenate (non-specific tissue), and Aedes aegyptie salivary gland homogenate (non-vector salivary gland) were used as well as UIS4, UIS7, and mCherry genes expression were compared with midgut sporozoites. Treated sporozoites have a transcription profile of the tested genes like that of salivary gland sporozoites. Although the variables causing Plasmodium development following mosquito salivary gland invasion may not be influenced by mosquito species, it does show tissue specificity. As a result, the salivary gland's function as a gateway and invasion is the most crucial and specific phase in disease transmission.