Analysis of the antigenic determinants of the OspC protein of the Lyme disease spirochetes: Evidence that the C10 motif is not immunodominant or required to elicit bactericidal antibody responses

Abstract

As Ixodes ticks spread to new regions, the incidence of Lyme disease (LD) in companion animals and humans will increase. Preventive strategies for LD in canines center on vaccination and tick control (acaricides). Both subunit and bacterin based LD veterinary vaccines are available. Outer surface protein C (OspC), a potent immunogen and dominant early antigen, has been demonstrated to elicit protective antibody (Ab) responses. However, a single OspC protein elicits a relatively narrow range of protection. There are conflicting reports as to whether the immunodominant epitopes of OspC reside within variable or conserved domains. A detailed understanding of the antigenic determinants of OspC is essential for understanding immune responses to this essential virulence factor and vaccinogen. Here, we investigate the contribution of the conserved C-terminal C10 motif in OspC triggered Ab responses. Using a panel of diverse recombinant full length OspC proteins and their corresponding C10 deletion variants (OspCΔC10), we demonstrate that the C10 motif does not significantly contribute to immunization or infection induced Ab responses in rabbits, rats, canines, horses and non-human primates. Furthermore, the C10 motif is not required to trigger potent bactericidal Ab responses. This study provides insight into the antigenic structure of OspC. The results enhance our understanding of immune responses that develop during infection or upon vaccination and have implications for interpretation of LD diagnostic assays that employ OspC.

Serologic Evidence for the Exposure of Eastern Coyotes ( Canis latrans ) in Pennsylvania to the Tick-Borne Pathogens Borreliella burgdorferi and Anaplasma phagocytophilum

“… High seropositivity for B. burgdorferi and A. phagocytophilum in eastern coyotes. B. burgdorferi B31 and human promyelocytic HL-60 cells (CCL-240; ATCC) and HL-60 cells infected with A. phagocytophilum NCH-1 were cultivated as previously described ( 14 , 15 ). Cells were harvested by centrifugation, washed, and solubilized in SDS-PAGE buffer.…”

“…Cells were harvested by centrifugation, washed, and solubilized in SDS-PAGE buffer. The B. burgdorferi cell lysates (A) and A. phagocytophilum -infected HL-60 cells (B) were separated by SDS-PAGE (AnykD Criterion precast gels; Bio-Rad), immunoblotted, and screened with a 1:1,000 dilution of each plasma sample, as previously described ( 15 ). The sector of Pennsylvania from which each animal was harvested is indicated above the immunoblots, with a plus or minus indicating the Ab scoring for each sample (see Table 1, footnote b, for sector abbreviations).…”

“…The sector of Pennsylvania from which each animal was harvested is indicated above the immunoblots, with a plus or minus indicating the Ab scoring for each sample (see Table 1, footnote b, for sector abbreviations). The migration positions of native A. phagocytophilum P130 and P44 proteins were determined by screening cell lysate immunoblots with rat anti-P130 and rat anti-P44 antisera (C), generated as previously described ( 15 ). Molecular weight markers are indicated.…”

“…The FhbB protein, a factor H-plasminogen binding protein produced by the human periopathogen Treponema denticola (13), served as a negative control, and as expected, the plasma samples were not reactive with this protein. The immunoscreening results obtained with each individual plasma sample are summarized and HL-60 cells infected with A. phagocytophilum NCH-1 were cultivated as previously described (14,15). Cells were harvested by centrifugation, washed, and solubilized in SDS-PAGE buffer.…”

Lyme disease vaccines face familiar challenges, both societal and scientific

“…This became a core component of a canine vaccine, called Vanguard crLyme, that the FDA approved in 2016. In that vaccine, both OspC and OspA antibodies work in concert to kill bacteria both inside and outside the tick (5).…”