Further insights into the sialome switch of Amblyomma americanum adult females

The lone star tick, Amblyomma americanum, is a three-host species widely distributed across North America and a vector for multiple human pathogens. Bites from this tick is also associated with alpha-gal syndrome, underscoring its growing public health importance. Adult female ticks undergo a prolonged feeding cycle divided into preparatory, slow-feeding, and rapid-feeding phases. Tick salivary glands are essential for successful blood feeding, producing a complex mixture of molecules that modulate host hemostasis, immunity, and tissue repair. The dynamic remodeling of the salivary gland transcriptome and proteome, termed the sialome switch, is thought to support prolonged feeding and immune evasion. To investigate the molecular mechanisms underlying the sialome switch, we performed high-throughput transcriptomic profiling of salivary glands from A. americanum adult females across the feeding cycle. Unlike previous studies that described the sialome switch in A. americanum by pooling ticks according to time post-attachment, we classified individuals based on average body weight, defining seven feeding stages encompassing unfed, slow-feeding, and rapid-feeding ticks. We identified 18,704 putative coding sequences (CDS) and revealed five distinct transcriptional profiles corresponding to different feeding stages. Unsupervised clustering indicated that most CDS were stage-specifically expressed, with temporal shifts observed in different protein families, including Kunitz-type, lipocalins, metalloproteases, and evasins. The transition from unfed to the slow-feeding phase corresponded to expression of a distinct subset of CDS within the signal transduction class, suggesting potential signaling pathways responsible for regulating this dynamic process. This study provides a high-resolution view of transcriptional dynamics in A. americanum salivary glands and identifies candidate molecular pathways regulating the sialome switch. These findings advance understanding of tick feeding biology and shed light on strategies ticks use to evade host defenses during prolonged blood meals.