Complement-Mediated Killing of Borrelia burgdorferi by Nonimmune Sera from Sika Deer

Abstract

Various species of cervid deer are the preferred hosts for adult, black-legged ticks (Ixodes scapularis and Ixodes pacificus) in the United States. Although frequently exposed to the agent of Lyme disease (Borrelia burgdorferi), these animals, for the most part, are incompetent as transmission reservoirs. We examined the borreliacidal activity of normal and B. burgdorferi-immune sera from sika deer (Cervus nippon) maintained in a laboratory setting and compared it to that of similar sera from reservoir-competent mice and rabbits. All normal deer sera (NDS) tested killed > 90% of B. burgdorferi cells. In contrast, normal mouse and rabbit sera killed < or = 22% of the Borrelia. Anti-B. burgdorferi antibodies could not be detected in any normal sera by indirect fluorescent antibody assay (IFA). Sera collected from deer 6 wk after exposure to B. burgdorferi by tick feeding exhibited IFA titers of 1:256, whereas sera from mice and rabbits similarly exposed had titers of > 1:1,024. Heat treatment (56 C, 30 min) of NDS reduced borreliacidal activity, with < 20% of the B. burgdorferi cells killed, suggesting complement-mediated killing. The chelators EGTA and EDTA were used to block the classical or both the classical and alternative complement pathways, respectively. Addition of 10 mM EGTA to NDS had a negligible effect on borreliacidal activity, with > 90% of the cells killed. Addition of 10 mM EDTA reduced the killing to approximately 30%, whereas the addition of Mg2+ (10 mM) restored borreliacidal activity to NDS. The addition of zymosan A, an activator of the alternative pathway, increased the survival of B. burgdorferi cells to approximately 80% in NDS. These data suggest that the alternative complement activation pathway plays a major role in the borreliacidal activity of NDS. Additionally, 10 mM EGTA had almost no effect on the killing activity of B. burgdorferi-exposed deer sera, suggesting that the classical pathway is not involved in Borrelia killing, even in sera from B. burgdorferi-exposed deer.

Complement-mediated tail degradation of Neodiplostomum seoulense cercariae

“…In schistosomes, C3-depleted sera or one of the terminal components C5 to C8 was used to confirm the above fact, but we adopted a simplified method using chelators (Nelson et al, 2000). In S. mansoni, the glycocalyx on the cercarial surface is known to be a strong activator of the alternative complement pathway (Samuelson and Caulfield, 1986), and in N. seoulense, similar mechanism seems to be related to complement-mediated cercarial tail degradation.…”

“…The chelator EDTA was used to block the classical and alternative complement pathways, and another chelator ethylene glycol-bis (β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) to block the classical complement pathway (Nelson et al, 2000). These agents were prepared as 200 mM stock solutions and stored at 4°C until use (Fine et al, 1972).…”

The importance of dogs in eco-epidemiology of Lyme borreliosis: a review

“…Furthermore, complement mediated lyses of B. garinii explains why the European rodents are insufficient reservoir for European B. garinii strains, while its resistance to pheasant complement makes clear the concept of reservoir competence ability of pheasant for the same Borrelia genospecies. In case of an incompetent reservoir sika deer active killing of Borrelia by complement takes place (Nelson et al, 2000). Similarly lysis of Borrelia regardless of genospecies correlates the incompetent reservoir nature of deer explained by Jaenson and Talleklint (1992).…”

Tick Infestation of Sika Deer (Cervus nippon) in the Western Part of Yamaguchi Prefecture, Japan.

“…For example, Anaplasma marginale is known to be a pathogen for both cattle and deer [11]. In the U.S.A., deer are considered to be an important reservoir of zoonosis agents, such as Borrelia burgdorferi, a Lyme disease spirochete [13]. Thus it is important to clarify the tick species found in sika deer from the viewpoint of both livestock and public health.…”