Gene regulation in response to host sex and infection route in <i>Brugia pahangi</i> with new genome annotation

Male rodents are almost exclusively used for experimental maintenance of filarial nematodes because they have higher susceptibility to parasitism than female rodents. This study investigates the effects that rodent host sex has on the worm transcriptome for subcutaneous (SQ) infections and intraperitoneal (IP) infections. Significantly more adult worms were recovered from IP-infected gerbils (median = 78 worms/infected animal) relative to SQ-infected gerbils (median = 2 worms/infected animal). Microfilaria production in male gerbils infected via the SQ route (mean = 6.62 microfilariae (mf)/20 µL, median = 5.65 mf/20 µL) was significantly greater than in female gerbils (mean = 0.43 mf/20 µL, median = 0 mf/20 µL). Male gerbils were also significantly more susceptible to SQ infection than females with a prevalence of 90% (n = 20) in males vs 27% (n = 29) in female gerbils. There was no significant difference in the number of adult worms recovered between male and female gerbils for either infection route. No statistically significant gene expression differences were observed in comparisons of worms of the same life stage/sex from male and female gerbils. In subcutaneously infected gerbils, the identification of differentially expressed genes was likely precluded by the markedly different transcript profiles between replicates. However, the transcriptional profiles for IP-infected gerbils were homogenous suggesting that the host sex does not alter nematode gene expression in the life stages examined from the IP model. The lack of impact of host sex on the transcriptome of worms isolated from IP-infected gerbils reinforces the use of male gerbils as the primary rearing host for these parasites. Genome annotation of B. pahangi is reported as it was required for this differential expression analysis.