Use of microarray hybridization to identify Brugia genes involved in mosquito infectivity

Brugia malayi and Brugia pahangi microfilariae (mf) require a maturation period of at least 5 days in the mammalian host to successfully infect laboratory mosquitoes. This maturation process coincides with changes in the surface composition of mf that likely are associated with changes in gene expression. To test this hypothesis, we verified the differential infectivity of immature (≤3 day) and mature (>30 day) Brugia mf for black-eyed Liverpool strain of Aedes aegypti and then assessed transcriptome changes associated with microfilarial maturation by competitively hybridizing microfilarial cDNAs to the B. malayi oligonucleotide microarray. We identified transcripts differentially abundant in immature (94 in B. pahangi and 29 in B. malayi) and mature (64 in B. pahangi and 14 in B. malayi) mf. In each case, >40% of Brugia transcripts shared no similarity to known genes or were similar to genes with unknown function; the remaining transcripts were categorized by putative function based on sequence similarity to known genes/proteins. Microfilarial maturation was not associated with demonstrable changes in the abundance of transmembrane or secreted proteins; however, immature mf expressed more transcripts associated with immune modulation, neurotransmission, transcription, and cellular cytoskeleton elements, while mature mf displayed increased transcripts potentially encoding hypodermal/muscle and surface molecules, e.g., cuticular collagens and sheath components. The results of the homologous B. malayi microarray hybridization were validated by quantitative reverse transcriptase polymerase chain reaction. These findings preliminarily lend support to the underlying hypothesis that changes in microfilarial gene expression drive maturation-associated changes that influence the parasite to develop in compatible vectors.