Evidence of Borrelia autoimmunity-induced component of Lyme carditis and arthritis

Abstract

We investigated the possibility that manifestations of Lyme disease in certain hosts, such as arthritis and carditis, may be autoimmunity mediated due to molecular mimicry between the bacterium Borrelia burgdorferi and self-components. We first compared amino acid sequences of Streptococcus pyogenes M protein, a known inducer of antibodies that are cross-reactive with myosin, and B. burgdorferi and found significant homologies with OspA protein. We found that S. pyogenes M5-specific antibodies and sera from B. burgdorferi-infected mice reacted with both myosin and B. burgdorferi proteins by Western blots and enzyme-linked immunosorbent assay. To investigate the relationship between self-reactivity and the response to B. burgdorferi, NZB mice, models of autoimmunity, were infected. NZB mice infected with B. burgdorferi developed higher degrees of joint swelling and higher anti-B. burgdorferi immunoglobulin M cross-reactive responses than other strains with identical major histocompatibility complex (DBA/2 and BALB/c). These studies reveal immunological cross-reactivity and suggest that B. burgdorferi may share common epitopes which mimic self-proteins. These implications could be important for certain autoimmunity-susceptible individuals or animals who become infected with B. burgdorferi.

FIG. 1.

Joint swelling in mice at various weeks after infection with B. burgdorferi. Mice were between 9 and 12 months of age at the time of initial infection. Data are means ± standard deviations (approximately five mice/group). Values are shown as the differences from uninfected time zero for each mouse. The NZB group was significantly different from the other groups on day 14 (P < 0.05; Student's t test).

FIG. 2.

Levels of anti-B. burgdorferi antibodies in B. burgdorferi (Bb)-infected animals at various times pre- and postinfection using equivalent serum dilutions. Data in columns represent mean values for OD (O.D.) readings in an ELISA of pooled sera from each group. Sera (diluted 1:10) were obtained from animals studied at 9 to 12 months of age. Columns are IgM (left three groups) and IgG (right three groups) antibodies reactive with B. burgdorferi.

FIG. 3.

Levels of IgM anti-OspA antibodies in control and B. burgdorferi-infected NZB mice infected between 5 and 6 months of age and bled on day 35 postinfection. Data in columns represent mean values for OD (O.D.) readings in an ELISA.

FIG. 4.

The mean ELISA OD (O.D.) readings of IgM anti-myosin reactivity in pooled sera of groups of mice infected with B. burgdorferi 35 days prior to readings. The anti-S. pyogenes (Strep) M5 MAb 36.2.2 was employed for comparison.

FIG. 5.

Levels of IgM anti-S. pyogenes M5 antibodies in B. burgdorferi-infected animals at various times pre- and postinfection. Data in columns represent mean values for OD readings in an ELISA. Pooled sera (diluted 1:10) were obtained from animals studied at 9 to 12 months of age (approximately five mice/group).

FIG. 6.

Competition of anti-B. burgdorferi (anti-Bb) reactivity with S. pyogenes M5 protein. Sera from 9- to 12-month-old individual NZB and DBA mice obtained on day 20 postinfection with B. burgdorferi or culture supernatants from anti-S. pyogenes (Strep) MAb 36.2.2 were preincubated with 10 μg of S. pyogenes M5 protein and then tested by ELISA for reactivity with B. burgdorferi lysates. Data represent mean OD values.

FIG. 7.

(A) Western blot immunoreactivity of serum or monoclonal antibodies to purified recombinant OspA lipoprotein. The control lane contains anti-OspA monoclonal antibody which detects the 31-kDa OspA protein. Sera were obtained from B. burgdorferi-infected NZB (lane b), DBA/2 (lane c), and BALB/c (lane d) mice 35 days following infection. Also shown are anti-S. pyogenes (Strep) M5 IgM MAbs 36.2.2 (lane e) and 54.2.8 (lane f). (Anti-OspA reactivity was detected with specific conjugated goat anti-mouse IgM in all lanes except the control lane, which was reacted with goat anti-mouse IgG.) (B) Anti-S. pyogenes monoclonal antibodies were screened for binding to ELISA plates coated with either B. burgdorferi sonicates, purified M5 protein, or control subpeptides NT3 and NT4. Data in columns represent mean values for OD readings in an ELISA.