Ixodes scapularis: Effects of repeated infestations with pathogen-free nymphs on macrophage and T lymphocyte cytokine responses of BALB/c and C3H/HeNmice

Ixodes scapularis is the principal vector in the United States of Borrelia burgdorferi, the causative agent of Lyme borreliosis, the human granulocyti c ehrichiosis agent, and Babesia microti. Infestation with I. scapularis ny mphs has previously been shown to modulate host T lymphocyte cytokine produ ction. Tick-induced host immunomodulation is increasingly recognized as a c ontributing factor in successful transmission and/or establishment of tick- borne pathogens. This study was conducted to determine the effects of repea ted infestations with pathogen-free I. scapularis nymphs on the production of the macrophage cytokines interleukin (IL)-1 beta and tumor necrosis fact or-ct and the T lymphocyte cytokines IL-2, IL-4, n-10, and interferon-gamma in both BALB/c and C3H/HeN mice. The pattern of T lymphocyte cytokine prod uction was evaluated to determine if repeated tick infestation polarizes th e immune response toward a Th-1 or Th-2 cytokine profile. Female BALB/c and C3H/HeN mice were infested one to four times with pathogen-free I. scapula ris nymphs, with a 14-day tick-free period between each exposure. After eac h infestation, tick biology parameters were measured and macrophage and T l ymphocyte cytokine production was assessed. Elaboration of T lymphocyte and macrophage cytokines was quantitated by antigen capture enzyme-linked immu nosorbent assay. Acquired resistance to I. scapularis feeding was not devel oped by either mouse strain. Significant differences in cytokine production were observed between infested and noninfested mice, as well as between th e two mouse strains, following tick infestation. Infestation of both strain s with pathogen-free I. scapularis results in a polarization of the host im mune response toward a Th-2, anti-inflammatory pattern, with a correspondin g suppression of Th-l responses, (C) 1999 Academic Press.