The cross-talk between spirochetal lipoproteins and immunity 2015-09-15

Spirochetal diseases such as syphilis, Lyme disease, and leptospirosis are major threats
to public health. However, the immunopathogenesis of these diseases has not been fully
elucidated. Spirochetes interact with the host through various structural components such
as lipopolysaccharides (LPS), surface lipoproteins, and glycolipids. Although spirochetal
antigens such as LPS and glycolipids may contribute to the inflammatory response during
spirochetal infections, spirochetes such as Treponema pallidum and Borrelia burgdorferi
lack LPS. Lipoproteins are most abundant proteins that are expressed in all spirochetes
and often determine how spirochetes interact with their environment. Lipoproteins are
pro-inflammatory, may regulate responses from both innate and adaptive immunity and
enable the spirochetes to adhere to the host or the tick midgut or to evade the immune
system. However, most of the spirochetal lipoproteins have unknown function. Herein, the
immunomodulatory effects of spirochetal lipoproteins are reviewed and are grouped into
two main categories: effects related to immune evasion and effects related to immune activation.
Understanding lipoprotein-induced immunomodulation will aid in elucidating innate
immunopathogenesis processes and subsequent adaptive mechanisms potentially relevant
to spirochetal disease vaccine development and to inflammatory events associated
with spirochetal diseases.