Anaplasma phagocytophilum induces Ixodes scapularis ticks to express an antifreeze glycoprotein gene that enhances their survival in the cold
Girish Neelakanta, … , John F. Anderson, Erol Fikrig
Girish Neelakanta, … , John F. Anderson, Erol Fikrig
Published August 25, 2010
Citation Information: J Clin Invest. 2010;120(9):3179-3190. https://doi.org/10.1172/JCI42868.
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Research Article

Anaplasma phagocytophilum induces Ixodes scapularis ticks to express an antifreeze glycoprotein gene that enhances their survival in the cold

Abstract

In the United States, Ixodes scapularis ticks overwinter in the Northeast and Upper Midwest and transmit the agent of human granulocytic anaplasmosis, Anaplasma phagocytophilum, among other pathogens. We now show that the presence of A. phagocytophilum in I. scapularis ticks increases their ability to survive in the cold. We identified an I. scapularis antifreeze glycoprotein, designated IAFGP, and demonstrated via RNAi knockdown studies the importance of IAFGP for the survival of I. scapularis ticks in a cold environment. Transfection studies also show that IAFGP increased the viability of yeast cells subjected to cold temperature. Remarkably, A. phagocytophilum induced the expression of iafgp, thereby increasing the cold tolerance and survival of I. scapularis. These data define a molecular basis for symbiosis between a human pathogenic bacterium and its arthropod vector and delineate what we believe to be a new pathway that may be targeted to alter the life cycle of this microbe and its invertebrate host.

Authors

Girish Neelakanta, Hameeda Sultana, Durland Fish, John F. Anderson, Erol Fikrig

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Figure 6

A. phagocytophilum infection and induction of iafgp expression enhances cold tolerance in tick cells.

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A. phagocytophilum infection and induction of iafgp expression enhances...
(A) QRT-PCR showing the levels of iafgp transcripts in tick cells incubated at different temperatures (28°C, 4°C, 0°C, –5°C). (B) QRT-PCR showing the level of iafgp transcripts in uninfected (white bar) and A. phagocytophilum–infected (black bar) tick cells at 48 hours after infection. Results from 3 independent experiments are shown. Error bars indicate + SD from the mean. The level of iafgp transcripts was normalized to tick beta-actin. (C) Immunofluorescence images of tick cells stained with FM4-64 dye showing increased membrane disruption in uninfected cells in comparison with A. phagocytophilum–infected cells after cold shock at –20°C for 10 minutes. Uninfected and A. phagocytophilum–infected tick cells incubated at 28°C served as experimental controls. Representative images from 3 independent experiments are shown. Original magnification, ×65. Scale bar: 20 μM. (D) Quantitative assessment of the number of membrane-disrupted cells in uninfected (white circles) and A. phagocytophilum–infected (black circles) tick cells after cold shock at –20°C for 10 minutes is shown. Each circle represents 1 microscopic field. Statistics were performed using Student’s t test and the P values are shown. Horizontal lines in the graph indicate average of the readings from independent microscopic observations.