Immunization with porcine cardiac myosin induced mild myocarditis in 50-60% of Diversity Outbred mice after three doses, whereas naïve mice showed no myocarditis.
Does immunization with porcine cardiac myosin emulsified in complete Freund's adjuvant induce autoimmune myocarditis in Diversity Outbred mice?
Diversity Outbred mice can serve as a translationally relevant model for mild autoimmune myocarditis, though their genetic heterogeneity necessitates large sample sizes.
Effect estimate: 55% incidence in 3-dose group
Absolute Event Rate: 55% vs 0%
Background. Inbred mouse models of autoimmune myocarditis are routinely used to investigate the immune mechanisms underlying dilated cardiomyopathy. However, their translational relevance is limited because observations made in a single inbred strain may not reflect those of outbred human populations. This limitation can be overcome by using Diversity Outbred (DO) mice, whose genetic variability is comparable to that of humans. Methods. To investigate the utility of DO mice, we characterized their immune cell distributions and induced myocarditis by immunization with porcine cardiac myosin (PCM) emulsified in complete Freund’s adjuvant. Antigen-specific T cell and antibody responses were evaluated using lymphocytes and serum samples, respectively, and hearts were examined histologically for inflammatory changes. Results. First, we noted no significant variations in the majority of immune cell populations, which include T cells and B cells. However, NK cells, double positive for CD49b and NK1.1, were lacking in both sexes. While we noted sex differences in the expression of major histocompatibility complex class II molecules in antigen-presenting cells, expression of costimulatory molecules was similar in both sexes. Second, upon immunization, we demonstrated that the PCM was immunogenic, and the PCM-reactive T cell responses were generated in both males and females, as measured by a proliferation assay. Third, cytokine analysis revealed marginal detection of Th1 (IFN-γ) and Th17 (IL-17 and IL-22) cytokines, mainly with three doses of immunization. Fourth, determination of PCM-reactive antibody responses revealed significant amounts of IgG1 and IgG2b isotypes. Finally, histological analysis revealed varying degrees of myocarditis in individual mice of both sexes. Conclusions. Our data suggest that mild autoimmune myocarditis can be induced in DO mice. However, to capture the heterogeneity in disease susceptibility, large sample cohorts are required.
Sur et al. (Fri,) conducted a other in Male and female young adult (6-8 weeks old) Diversity Outbred mice induced with myocarditis by immunization with porcine cardiac myosin emulsified in complete Freund’s adjuvant (n=28). Porcine cardiac myosin (PCM) immunization vs. Naïve (non-immunized) mice was evaluated on Incidence and severity of autoimmune myocarditis assessed by histological inflammatory infiltrates in heart tissue on day 21 or day 28 (55% incidence in 3-dose group). Immunization with porcine cardiac myosin induced mild myocarditis in 50-60% of Diversity Outbred mice after three doses, whereas naïve mice showed no myocarditis.