Murine Cytomegalovirus-induced Complement-fixing Antibodies Deposit in Murine Renal Allografts during Acute Rejection

Background. Human cytomegalovirus (CMV) infection is associated with renal allograft dysfunction and loss, particularly in combination with acute rejection. Emerging literature suggests that non-HLA antibodies may contribute to antibody-mediated rejection, but pathogen-induced antibodies have not been investigated in this context. This study examines the presence of CMV-induced antibodies in murine CMV (MCMV)-infected renal allografts during acute rejection. Methods. Intragraft immunoglobulin G (IgG) and complement C3 immunostaining were compared among allogeneic MCMV D^-/R^-, D⁺/R^-, and D⁺/R⁺renal transplants. Intragraft antibody deposition was examined in B cell-deficient recipients treated with MCMV immune sera. Antibody binding and complement-dependent cytotoxicity (CDC) of D^-/R^-and D⁺/R⁺sera against infected renal tubular epithelial cells (TECs) were measured in vitro. IgG immunostaining was performed in D⁺/R⁺allografts and native kidneys and in D⁺/R^-allografts treated with ganciclovir to inhibit viral replication. Results. D⁺/R^-and D⁺/R⁺transplants had more abundant IgG and C3 deposition compared with D^-/R^-recipients. Greater IgG deposition was associated with more severe allograft injury in B cell-deficient recipients treated with MCMV immune sera compared with nonimmune sera. D⁺/R⁺sera induced greater CDC of infected TECs compared with D^-/R^-sera. Native kidneys had lower IgG deposition compared with allografts, despite similar organ viral loads. Ganciclovir-Treated allografts had reduced IgG deposition compared with untreated allografts. Conclusions. In this murine model, complement-fixing antibodies can deposit into MCMV-infected renal allografts, are associated with allograft damage, and can induce CDC of MCMV-infected renal TECs. The allogeneic response and viral replication may also contribute to intragraft antibody deposition.