Abstract
IntroductionHuman cytomegalovirus (HCMV) infection has been implicated in the development of autoimmunity, including systemic lupus erythematosus (SLE). Previously we reported that HCMV phosphoprotein 65 (pp65) could induce early onset of autoantibody and glomerulonephritis on lupus-prone NZB/W mice. This study further examined whether the B cell epitope(s) in pp65 is able to drive the development of autoantibody.MethodsSera from SLE patients or HCMVpp65-immunized mice were analyzed for anti-nuclear antibody by immunoblotting, enzyme-linked immunosorbent assay (ELISA), immunofluorescent stain and Crithidia luciliae stain. The deposition of immunoglobulin to the kidney was also examined by immunofluorescent stain. The interactions between pp65 sub-fragment to cellular proteins were revealed by yeast two-hybrid analyses.ResultsOur results showed that most SLE patients possessed antibodies to the C-terminal half of the HCMVpp65 antigen. Of these positive sera, 73% were also positive to the pp65336-439 sub-fragment. The immunization of pp65336-439 induced formation of multiple anti-nuclear antibodies, including anti-chromatin, anti-centriole, anti-mitotic spindle type I/II (MSA I/II) and a significant elevation of anti-double-stranded DNA (anti-dsDNA) antibodies on BALB/c mice. Yeast two-hybrid analyses revealed the binding of pp65336-439 sub-fragment to cellular proteins. Immunoglobulin deposition on glomeruli was also detected on pp65336-439-immunized mice.ConclusionsOur data suggested that HCMVpp65336-439 sub-fragment may induce cross-reactive antibodies to several nuclear antigens, which could contribute to the development of autoimmunity in genetic-suspected individuals.
Highlights
Human cytomegalovirus (HCMV) infection has been implicated in the development of autoimmunity, including systemic lupus erythematosus (SLE)
The pp65336-439 sub-fragment of HCMV contains a B cell epitope(s) targeted by IgG from SLE patients To verify the existence of B-cell epitope(s), HCMVpp65 tegument protein was cloned, truncated and expressed as his-tagged fragments that covered the entire antigen (Figure 1)
We found that immunization of pp65336-439 peptide with complement 3d (C3d) could sustain the humoral immunity to pp65336-439, and such immunization elicited cross-reactive antibody against host cellular proteins, including double-stranded DNA (dsDNA) and its associated proteins on non-autoimmune BALB/c mice
Summary
Human cytomegalovirus (HCMV) infection has been implicated in the development of autoimmunity, including systemic lupus erythematosus (SLE). The Epstein-Barr virus (EBV)-infection-induced systemic lupus erythematosus (SLE)-specific autoantibody is one of the best examples for cross-reactive antibody mediated autoimmunity [1]. In those studies, autoantibodies to Smith antigen B/B’ (SmB/B’) and clinical symptoms that resemble SLE were induced by normal strains of mice following immunization of octapeptide (PPPGRRP) [2]. HCMV belongs to the Betaherpesvirinae family and is an opportunistic pathogen that could cause severe clinical consequences in individuals with impaired immune systems [4] Specific activation of both viral-specific and auto-reactive T-cells during infection has been shown to accelerate the development of type I diabetes [5,6]. Two T-cell dominant regions, pp65303-388 and pp65477-561, located on the C-terminus of pp, have been reported and at least 28 CTL epitopes were verified within the CMVpp65 [13,14]
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