In silico and two-hybrid functional characterization of the Rhipicephalus microplus (Canestrini, 1888) vaccine antigen Bm86

Abstract

Ticks are considered economically significant parasitic vectors in the livestock industry globally. Vector directed vaccines are a promising method of tick control. To date only one protective antigen, Bm86, has been commercialised; however, it has variable efficacy across regions and, despite a previous study which proposed a possible role for Bm86 in Phospholipase C signalling (PLC), its biological role is unclear. Antigen 1, a new vaccine candidate, has been identified to interact with Bm86, but the region of protein interaction with Bm86 is unknown. This study assembled transcriptomes of the larval, nymph, and adult gut, ovary and salivary gland via de novo RNA sequence assembly to identify PLC pathway components, Bm86 and Antigen 1 in South African Rhipicephalus microplus. G proteins, namely, Gαi/o/s/q as well as a Gγ and Gβ subunits and PLCβ, γ, δ, η and ε, were identified. This is the first study to identify these proteins expressed in R. microplus. Furthermore, regions of sequence variation in the South African Bm86 and Antigen 1 in various life stages and tissues of R. microplus ticks were analysed. Also, the study used a yeast-two-hybrid model to study the region of Antigen 1 interaction with Bm86 and found it to be the N-terminal region of Antigen 1. These findings are particularly important in the design of tick control strategies such as vaccine and acaricide development; providing insight into the mechanism of two vaccine antigens as well as identifying various potential novel drug targets in the biology of R. microplus.