Silencing of a putatively immune-related lipocalin-like gene in Amblyomma americanum

The number and diversity of tick-borne diseases in the United States have been on the rise in recent years. Among pathogens transmitted by ticks, bacteria form the majority. However, a complete understanding of how the tick immune system is defeated by pathogens is still being developed. We investigated a putatively immune-related lipocalin-like gene in Amblyomma americanum. Lipocalins are an extremely diverse group of proteins, serving numerous roles in arthropod physiology, including immune response. Previously, we showed that the lipocalin-like gene was only expressed during infection. In this study, we furthered the evaluation of its potential immune function. We expanded expression analysis to screen wild-caught, uninfected nymphs and males. We also assessed the impact of this gene on the expression of five other putatively immune-related genes using RNAi. For this, ticks were infected with E. coli subsequent to lipocalin-like gene silencing and then sampled at 3-, 24-, and 48 h post-infection for analysis of gene expression by PCR. The expression profiles of lipocalin that were seen before and during infection in nymphs and males were variable. In RNAi-silenced ticks, we checked for the impact of expression in other genes. Follow-up studies clarifying the impact of the lipocalin-like gene on the expression of other genes are necessary. Identifying immune genes in vectors is a key step in understanding how these pathways are subverted during pathogen infection.