Ticks as Therapy?
Ironically, the very components of tick saliva that make their bites so effective at transmitting bacteria are the ones that could prove useful as medicines, namely a protein now known as tick anticoagulant peptide (TAP) and Ixolaris, a novel recombinant tissue factor pathway inhibitor (TFPI). Based on the saliva of Ixodes scapularis, one of the types of tick that is known to transmit Lyme disease, these two substances have been shown to have potential as medicines to inhibit blood clot formation, block primary tumor growth and modulate the immune system.
Tick Saliva for Autoimmune Disease?
There are currently no medicines on the market that make use of these potentially therapeutic compounds in tick saliva but research in a glioblastoma model has proven successful in inhibiting cancerous growth and the development of blood vessels that feed the growth of such tumors (Carneiro-Lobo, et al, 2009). As immunomodulators (Maritz-Olivier, et al, 2007), the components of tick saliva could also have a range of uses in autoimmune diseases but no research has, as yet, been conducted into such a hypothesis.
Inhibition of Blood Vessel Growth from Tick Saliva
Francischetti, and colleagues, reported back in 2005 on the anticoagulant properties of tick saliva and their potential therapeutic benefits as inhibitors of angiogenesis. They found that a dose-dependent inhibition of microvascular endothelial cell (MVEC) proliferation occurred with salivary gland extracts or dilute saliva taken from the Lyme disease tick. Another tick, the cattle tick Boophilus microplus, also demonstrated such properties but a variety of ticks of other types did not have such an effect. Francischetti, et al, also found that the tick saliva from the Lyme disease tick changed the shape of the cell, shrinking cytoplasm and reducing cell to cell interactions.
How Tick Saliva Inhibits Wound Repair
The researchers found that it was these inhibitors of angiogenesis in the ticks’ saliva that inhibited wound healing and repair, thus allowing the tick to feed for several days without the wound closing up. After a bite, or any other wound, there are three common stages of healing: inflammation; proliferation; and remodelling. The process is ongoing and so these stages overlap with one another to ensure proper scaffolding is built for new tissue and that cells differentiate correctly to restore the skin or other tissue as necessary. Angiogenesis occurs during the proliferative stage of healing and involves the formation of granulation tissue through endothelial cells, fibroblast accumulation and collagen synthesis. However, angiogenesis is also involved in some diseases, such as cancer.
A Lyme Disease Silver Lining?
That a substance in ticks’ saliva has the potential to control the growth and spread of cancer may be of little consolation to those suffering from Lyme disease symptoms but it does currently appear to represent a missed opportunity for medical researchers. Some research has, however, occurred looking at the effects of a protein from tick saliva on the symptoms of myasthenia gravis in rats, with promising results (Soltys, et al, 2009). Anti-inflammatory and antihaemostatic properties of tick saliva hold considerable potential as therapeutic agents but this potential remains untapped, even if it could be considered a silver lining to the spreading tick problem in the US and Europe.
Francischetti, I.M.B., Mather, T.N., Ribeiro, J.M.C., Tick saliva is a potent inhibitor of endothelial cell proliferation and angiogenesis, Thromb Haemost. 2005 July; 94(1): 167–174.
Maritz-Olivier, C., Stutzer, C., Jongejan, F., et al., 2007. Tick anti-hemostatics: targets for future vaccines and therapeutics. Trends Parasitol. 23, 397e407.
Carneiro-Lobo, T.C., Konig, S., Machado, D.E., 2009. Ixolaris, a tissue factor inhibitor, blocks primary tumor growth and angiogenesis in a glioblastoma model. J. Thromb. Haemost. 7, 1855e1864.
Soltys J, Kusner LL, Young A, Richmonds C, Hatala D, Gong B, Shanmugavel V, Kaminski HJ. Novel complement inhibitor limits severity of experimentally myasthenia gravis. Ann Neurol. 2009;65(1):67-75.