Rapid clearance of Borrelia burgdorferi from the blood circulation

Abstract

Background: Borrelia burgdorferi is a tick-borne spirochete that causes Lyme borreliosis (LB). After an initial tick bite, it spreads from the deposition site in the dermis to distant tissues of the host. It is generally believed that this spirochete disseminates via the hematogenous route. Borrelia persica causes relapsing fever and is able to replicate in the blood stream. Currently the exact dissemination pathway of LB pathogens in the host is not known and controversially discussed. Methods: In this study, we established a strict intravenous infection murine model using host-adapted spirochetes. Survival capacity and infectivity of host-adapted B. burgdorferi sensu stricto (Bbss) were compared to those of B. persica (Bp) after either intradermal (ID) injection into the dorsal skin of immunocompetent mice or strict intravenous (IV) inoculation via the jugular vein. By in vitro culture and PCR, viable spirochetes and their DNA load in peripheral blood were periodically monitored during a 49/50-day course post-injection, as well as in various tissue samples collected at day 49/50. Specific antibodies in individual plasma/serum samples were detected with serological methods. Results: Regardless of ID or IV injection, DNA of Bp was present in blood samples up to day 24 post-challenge, while no Bbss was detectable in the blood circulation during the complete observation period. In contrast to the brain tropism of Bp, Bbss spirochetes were found in ear, skin, joint, bladder, and heart tissue samples of only ID-inoculated mice. All tested tissues collected from IV-challenged mice were negative for traces of Bbss. ELISA testing of serum samples showed that Bp induced gradually increasing antibody levels after ID or IV inoculation, while Bbss did so only after ID injection but not after IV inoculation. Conclusions: This study allows us to draw the following conclusions: (i) Bp survives in the blood and disseminates to the host's brain via the hematogenous route; and (ii) Bbss, in contrast, is cleared rapidly from the blood stream and is a tissue-bound spirochete.

Targeting Multicopy Prophage Genes for the Increased Detection of Borrelia burgdorferi Sensu Lato (s.l.), the Causative Agents of Lyme Disease, in Blood

“…In this study, we confirmed that Borrelia prophages can escape from the bacterial host cell in a spontaneous manner. Taking advantage of the multicopy and free movement of Borrelia prophages, the approach to target prophages instead of bacteria will bypass the cryptic and tissue-bound feature that typifies human Borrelia infections ( Liang et al, 2020 ). Thus, we have a greater chance of detecting the prophages in blood even when the bacteria may not be present or present in extremely low numbers.…”

“…Our spontaneous induction data led us to predict that the prophage-based Ter-qPCR would generate a much stronger Borrelia signal than bacteria-based qPCR, because LD Borrelia species are tissue bound and thus can only circulate in blood transiently and in very low numbers ( Liang et al, 2020 ). In contrast, under the scenario of induction, prophages are released into bloodstream, and thus can be a ‘marker’ indicating the presence of Borrelia , even though Borrelia cells can be hiding and not circulating in the blood.…”

“…The reasons behind the poor sensitivity of the current PCR methods in Lyme detection are twofold; first, the current PCRs target Borrelia genomic DNA regions that have only one copy in each bacterium, such as the bacterial 16S rRNA gene, RecA gene, and the 5S-23S intergenic regions ( Brettschneider et al, 1998 ; Liveris et al, 2012 ; Waddell et al, 2016 ; Lohr et al, 2018 ; Schutzer et al, 2019 ). Second, at least some Borrelia species are ‘tissue-bound’ and are only transiently found circulating in the blood ( Liang et al, 2020 ).…”

Targeting multicopy prophage genes for the differential diagnosis of Lyme disease

“…The reasons behind the poor sensitivity of the current PCR methods in Lyme diagnosis are twofold; first, the current PCRs target Borrelia genomic DNA regions that have only one copy in each bacterium, such as the bacterial 16S rRNA gene, RecA gene, and the 5S-23S intergenic regions 15,16,25-27 . Second, at least some Borrelia species are ‘tissue-bound’ and are only transiently found circulating in the blood 28 .…”

“…In this study, we confirmed that Borrelia prophages can escape from the bacterial host cell in a spontaneous manner. Taking advantage of the multicopy and free movement of Borrelia prophages, the approach to target prophages instead of bacteria will bypass the cryptic and tissue-bound feature that typifies human Borrelia infections 28 . Thus, we have a greater chance of detecting the prophages in blood even when the bacteria may not be present or present in extremely low numbers.…”