Ixodes scapularis is the specific arthropod vector for a number of globally prevalent
infections, including
Lyme disease caused by the bacterium Borrelia burgdorferi. A feeding-induced and acellular epithelial barrier, known as the peritrophic membrane (PM) is detectable in I. scapularis. However, whether or how the PM influences the persistence of major tick-borne pathogens, such as B. burgdorferi, remains largely unknown. Mass spectrometry-based
proteome analyses of isolated PM from fed ticks revealed that the membrane contains a few detectable
proteins, including a predominant and immunogenic 60 kDa
protein with homology to arthropod
chitin deacetylase (CDA), herein termed I. scapularis CDA-like
protein or IsCDA. Although IsCDA is primarily expressed in the gut and induced early during tick feeding, its silencing via RNA interference failed to influence either the occurrence of the PM or spirochete persistence, suggesting a redundant role of IsCDA in tick biology and host-pathogen interaction. However, treatment of ticks with
antibodies against IsCDA, one of the most predominant
protein components of PM, affected B. burgdorferi survival, significantly augmenting pathogen levels within ticks but without influencing the levels of total gut bacteria. These studies suggested a preferential role of tick PM in limiting persistence of B. burgdorferi within the vector. Further understanding of the mechanisms by which vector components contribute to pathogen survival may help the development of new strategies to interfere with the
infection.