bptA(bbe16) is essential for the persistence of the Lyme disease spirochete,Borrelia burgdorferi, in its natural tick vector

Abstract

Borrelia burgdorferi (Bb), the agent of Lyme disease, is a zoonotic spirochetal bacterium that depends on arthropod (Ixodes ticks) and mammalian (rodent) hosts for its persistence in nature. The quest to identify borrelial genes responsible for Bb's parasitic dependence on these two diverse hosts has been hampered by limitations in the ability to genetically manipulate virulent strains of Bb. Despite this constraint, we report herein the inactivation and genetic complementation of a linear plasmid-25-encoded gene (bbe16) to assess its role in the virulence, pathogenesis, and survival of Bb during its natural life cycle. bbe16 was found to potentiate the virulence of Bb in the murine model of Lyme borreliosis and was essential for the persistence of Bb in Ixodes scapularis ticks. As such, we have renamed bbe16 a gene encoding borrelial persistence in ticks (bpt)A. Although protease accessibility experiments suggested that BptA as a putative lipoprotein is surface-exposed on the outer membrane of Bb, the molecular mechanism(s) by which BptA promotes Bb persistence within its tick vector remains to be elucidated. BptA also was shown to be highly conserved (>88% similarity and >74% identity at the deduced amino acid levels) in all Bb sensu lato strains tested, suggesting that BptA may be widely used by Lyme borreliosis spirochetes for persistence in nature. Given Bb's absolute dependence on and intimate association with its arthropod and mammalian hosts, BptA should be considered a virulence factor critical for Bb's overall parasitic strategy.

A manganese transporter, BB0219 (BmtA), is required for virulence by the Lyme disease spirochete, Borrelia burgdorferi

“…Similarly, Mn, possibly via the Mn-dependent Fur homolog BosR (23,33,37,38) Our study has demonstrated that the Lyme disease spirochete requires BmtA's Mn-associated transport function(s) to maintain its infectious cycle in nature. To date, only relatively few virulence factors, including OspC, DbpB/A, OspA/B, PncA, and BptA, have been identified in Bb, and the functions of most of these proteins remain obscure (4,5,(7)(8)(9)(10). In this regard, our identification of BmtA as a novel virulence factor in Bb provides further insights into molecular mechanisms that contribute to Bb's survival in nature and may lead to new strategies to interrupt the spirochete life cycle.…”

“…In recent years, extensive efforts have been directed toward elucidating the mechanisms by which Bb cycles, adapts, and sustains itself in these diverse niches. It is now well established that outer surface (lipo)protein C (OspC), OspA/B, decorin-binding protein B/A (DbpB/A), PncA, and BptA are required by Bb for efficient infection of ticks or mammalian hosts (4)(5)(6)(7)(8)(9)(10). It is also generally accepted that the recently discovered Rrp2-RpoN ( 54 )-RpoS ( S ) regulatory pathway plays prominently in Bb's virulence expression (11)(12)(13)(14).…”

Biology of Infection with Borrelia burgdorferi

“…Subsequent studies suggest that OspA is an adhesin, important for retaining spirochetes in the tick midgut until feeding [161][162][163]. OspB, another potential midgut adhesin [164], BptA, a lipoprotein of unknown function, and the product of the BB0690 gene, which is probably involved in resistance to oxidative stress [165], also appear to contribute to bacterial survival in ticks [166][167][168]. The RpoN-RpoS regulatory cascade appears to be required for migration of spirochetes to the salivary glands during transmission, but not for survival within the tick environment [153].…”

BB0238, a Presumed Tetratricopeptide Repeat-Containing Protein, Is Required during Borrelia burgdorferi Mammalian Infection

“…For IFA with permeabilized (fixed) cells, bacteria were prepared as described by Revel et al (7). Bb297 or Bb⌬bb0238 spirochetes were collected at mid-logarithmic growth phase, washed with PBS-MgCl 2 , and resuspended in PBS-MgCl 2 to 1.5 ϫ 10 7 spirochetes/ml.…”

“…These hypothetical proteins are particularly interesting because they represent a group of borrelial proteins that might contribute to vector and/or mammalian colonization and, ultimately, may provide insight into molecular mechanisms contributing to host/vectorpathogen interactions. Although studying genes with unknown functions represents a challenge, a number of these unique B. burgdorferi proteins (i.e., BptA, BB0323, BBA52, BBA57, BBA62, and BBA64) are now known to play roles at different stages of the spirochete's enzootic cycle (7)(8)(9)(10)(11)(12). Elucidation of the roles of individual hypothetical proteins in B. burgdorferi and identification of those necessary for mammalian infection would potentially provide new avenues of intervention or therapeutic targets.…”