Maternal transfer of neutralizing antibodies to B. burgdorferi OspA after oral vaccination of the rodent reservoir

Abstract

Lyme Disease presents unique challenges for public health. Transfer of protective antibodies between mothers and offspring should occur after vaccination of mice. We present new evidence for maternal transfer of oral vaccine induced neutralizing anti-OspA IgG antibodies to mouse pups mainly through ingestion of colostrum. We found a strong statistical correlation of antibody transfer between mothers that produced the most robust IgG response to OspA and their respective pups. OspA-specific antibody was detected as early as 24 h after birth and protective levels of antibodies lasted until ~5 weeks of age in the majority of pups but persisted in some mice until 9 weeks. This was further supported by detection of neutralizing antibodies in serum of all pups at 2-3 weeks after birth and in some offspring adult mice at 9 weeks of age. A clear association was found between robust antibody responses in mothers and the length of time antibody persisted in the respective pups using a novel longitudinal Bayesian model. These factors are likely to impact the enzootic cycle of B. burgdorferi if reservoir targeted OspA-based vaccination interventions are implemented.

Keywords: Bayesian modelling; Borrelia burgdorferi; Lyme disease; Maternal-transfer; Oral vaccination; OspA.

Figure 1.

Diagram of the immunization schedule, breeding, parturition and bleeding of mothers and offspring. OV, oral vaccination; D, day after first vaccine dose; w, weeks; cohort A, pups terminated and bled within 24h of birth; cohort B, pups bled 2 weeks after birth and then weekly until termination at 17 weeks.

Figure 2.

OspA-specific antibodies in serum from orally vaccinated mothers over ~7 months post first vaccine dose. We measured anti-OspA IgG by ELISA in serum from 10 mothers orally vaccinated with E. coli expressing OspA (EcA, M1-M10) and 6 placebo controls (Ec, M11-M16). Mice were bled before (D0) and after immunization (D21, D35), before breeding (D54), after the pups were born at ~D140 (7-week old pups) and at ~D210 (17-week old pups). A, Protocol for vaccination, breeding and blood collection from mothers; B, Comparison of anti-OspA IgG (OD₄₅₀>0.8) between EcA and Ec groups. Differences between EcA and Ec groups are statistically significant by unpaired t test with Welch’s correction, D21 p=0.0038, D35 p= 0.0260, D54 p=0.0003, D140 p=0.0147, D210 p=0.0488. C, Longitudinal log scale trajectory of antibody response over time, each line represents one mother, M5 was not bled on D140.

Figure 3.

OspA-specific antibodies in serum from offspring born to orally vaccinated mothers within 24h of birth and over 4 months post birth. A, Longitudinal log scale trajectory of anti-OspA IgG measured in serum from both cohorts of pups, by individual pup: Cohort A pups were analyzed on the day of birth, and Cohort B pups were analyzed 2 to 9 weeks after birth. B and C, Anti-OspA IgG in both cohorts of pups, grouped by mother. Statistics by Unpaired t test with Welch’s correction between EcA and Ec, * p<0.05, ** p<0.005, *** p<0.0005 and **** p<0.0001. EcA, oral vaccination with E. coli expressing OspA; Ec Ctrl, placebo control; M1-M10 EcA vaccinated mothers; w, weeks.

Figure 4.

Bayesian hierarchical model showing median anti-OspA antibody levels in EcA vaccinated and control mothers, and pups from each group. Each group median is given along with 95% posterior credible intervals (Cr-I). Differences in antibody curves between vaccinated and control mothers and their offspring are immediately apparent. Legend: EcA, oral vaccination with E. coli expressing OspA; Ec, oral vaccination with Ec placebo; Cr-I, Credible Intervals.

Figure 5.

Anti-OspA neutralizing antibody (nAb) function against B. burgdorferi. Number of motile B. burgdorferi (Bb) after treatment of a multi-strain culture with A) pooled serum from mothers M6 M7 M8 M10, pooled serum from mothers M2 M4 M5 and individual serum samples from mothers M3 and M9; B, pooled serum from all pups born to M9 on the day of birth (Cohort A); C, pooled 2–3w serum from Cohort B pups born to M2 M3, M4 and M5 (pooled according to birth mother); and D, pooled serum from all pups born to M3 collected 9 weeks after birth (Cohort B). Live Bb were counted under a dark field microscope.