Kinase-deficient CMVpp65 triggers a CMVpp65 specific T-cell immune response in HLA-A*0201.Kb transgenic mice after DNA immunization

Model Predicts That MKP1 and TAB1 Regulate p38α Nuclear Pulse and Its Basal Activity through Positive and Negative Feedback Loops in Response to IL-1

Interleukin-1 mediates inflammation and stress response through nuclear activity of p38α. Although IL-1 receptor is not degraded, p38α activation is transient. IL-1 also causes cell migration and EMT by modulating cell-cell junctions. Although molecules involved in p38 activation are known, mechanism of the transient nuclear response and its basal activity remains unknown. By mathematical modeling of IL1/p38 signaling network, we show that IL-1 induces robust p38α activation both in the nucleus and in the cytoplasm/membrane. While nuclear response consists of an acute phase, membrane response resembles a step change. Following stimulation, p38α activity returns to a basal level in absence of receptor degradation. While nuclear pulse is controlled by MKP1 through a negative feedback to pp38, its basal activity is controlled by both TAB1 and MKP1 through a positive feedback loop. Our model provides insight into the mechanism of p38α activation, reason for its transient nuclear response, and explanation of the basal activity of MKK3/6 and p38α, which has been experimentally observed by other groups.

Biologic and immunologic effects of knockout of human cytomegalovirus pp65 nuclear localization signal

The human cytomegalovirus (CMV) pp65 protein contains two bipartite nuclear localization signals (NLSs) at amino acids (aa) 415 to 438 and aa 537 to 561 near the carboxy terminus of CMV pp65 and a phosphate binding site related to kinase activity at lysine-436. A mutation of pp65 with K436N (CMV pp65mII) and further deletion of aa 537 to 561 resulted in a novel protein (pp65mIINLSKO, where NLSKO indicate NLS knockout) that is kinaseless and that has markedly reduced nuclear localization. The purpose of this study was to biologically characterize this protein and its immunogenicity compared to that of native pp65. Unlike the native CMV pp65, following either DNA- or recombinant adeno-associated virus-based transduction of CMV pp65mIINLSKO into cells in vitro, the first observation of pp65mIINLSKO expression was in the cytoplasm and pp65mIINLSKO was expressed at higher levels than the native protein. The CMV pp65mIINLSKO mRNA was more abundant earlier than CMV pp65 mRNA (at 4 h and 8 h, respectively), but the half-lives of the proteins were the same. This modification altered the antigenic processing of CMV pp65 in vitro, as measured by the improved efficiency of cytotoxic killing in a pp65mIINLSKO-transduced human HLA A*0201 target cell line. In HHDII mice expressing HLA A*0201, pp65mIINLSKO was as immunogenic as CMV pp65. By RNA microarray analysis, expression of the CMV pp65mIINLSKO had less of an effect on cell cycle pathways than the native CMV pp65 did and a greater effect on cell surface signaling pathways involving immune activity. It is concluded that the removal of the primary NLS motif from pp65 does not impair its immunogenicity and should be considered in the design of a vaccine.

Induction of pluripotent protective immunity following immunisation with a chimeric vaccine against human cytomegalovirus

Based on the life-time cost to the health care system, the Institute of Medicine has assigned the highest priority for a vaccine to control human cytomegalovirus (HCMV) disease in transplant patients and new born babies. In spite of numerous attempts successful licensure of a HCMV vaccine formulation remains elusive. Here we have developed a novel chimeric vaccine strategy based on a replication-deficient adenovirus which encodes the extracellular domain of gB protein and multiple HLA class I & II-restricted CTL epitopes from HCMV as a contiguous polypeptide. Immunisation with this chimeric vaccine consistently generated strong HCMV-specific CD8⁺ and CD4⁺ T-cells which co-expressed IFN-γ and TNF-α, while the humoral response induced by this vaccine showed strong virus neutralizing capacity. More importantly, immunization with adenoviral chimeric vaccine also afforded protection against challenge with recombinant vaccinia virus encoding HCMV antigens and this protection was associated with the induction of a pluripotent antigen-specific cellular and antibody response. Furthermore, in vitro stimulation with this adenoviral chimeric vaccine rapidly expanded multiple antigen-specific human CD8⁺ and CD4⁺ T-cells from healthy virus carriers. These studies demonstrate that the adenovirus chimeric HCMV vaccine provides an excellent platform for reconstituting protective immunity to prevent HCMV diseases in different clinical settings.

Human cytomegalovirus pp65 lower matrix protein: a humoral immunogen for systemic lupus erythematosus patients and autoantibody accelerator for NZB/W F1 mice

Both the infection of human cytomegalovirus (HCMV) and the immunization of its recombinant glycoprotein (gB) in mice have been known to induce autoimmunity, resulting in symptoms similar to those of human systemic lupus erythematosus (SLE). Research has also found that the murine cytomegalovirus (MCMV)-specific monoclonal antibody (mAb) is able to react with a human U1-70K-like autoantigen. To investigate HCMV involvement in autoimmunity, we analysed the humoral responses to HCMV by autoimmune patients and normal adults. Our studies show unambiguously that sera from SLE patients exhibited an elevated IgG titre to HCMV when compared with those observed in controls and other connective tissue disease (CTD) patients (P < 0.001). The IgM titres to HCMV and IgG to HBV were evaluated, and no significant differences were noted among all testing groups. In addition to initiating T cell activity, as reported by many investigators, we found that the HCMV pp65 antigen (also known as lower matrix protein) was able to induce humoral responses in SLE patients. Immunoblot assays showed that 82.56% of sera from SLE patients reacted with the HCMV pp65 antigen, but only 11.11%, 23.53% and 31.17% of patients from normal control, rheumatoid arthritis (RA) and CTD patients, respectively, reacted to it. Unlike HCMV pp65, HCMV pp150 induced B cell activity in most collected sera (92.22%-98.04%). Finally, female NZB/W F1 mice immunized with plasmids encoding HCMV pp65 open reading frame (pcDNApp65) developed an early onset of autoantibody activity and more severe glomerulonephritis. Thus, we conclude that the HCMV pp65 antigen triggers humoral immunity in SLE patients and autoimmune-prone mice and that it could very well exacerbate the autoimmune responses in susceptible animals.

Cytomegalovirus immune reconstitution occurs in recipients of allogeneic hematopoietic cell transplants irrespective of detectable cytomegalovirus infection

The question of when immune reconstitution of cytomegalovirus (CMV)-specific CD8 T cells occurs after hematopoietic cell transplantation and, more specifically, to which CMV targets this immunity is likely to be directed remains poorly understood. The dependence of immune reconstitution on CMV reactivation is even less clear. To better understand these events, 44 CMV-seropositive HLA-A*0201 subjects were followed up at approximately days 40, 90, 120, 150, 180, and 360 after hematopoietic cell transplantation for CMV immunity as measured by 2 types of assays: (1) an HLA-A*0201 tetramer-binding assay for both CMV pp65 (pp65) and immediate-early 1 (IE-1) or (2) intracellular cytokine interferon gamma responses induced by pp65 or IE-1-derived peptides. To verify the reliability of IE-1-specific assays relative to the pp65-based assays, a pilot study first compared the development of IE-1-specific immunity in a subgroup by using multiple HLA-A*0201-restricted peptides, and then these recipients were followed up for 1 year for immunologic function and for CMV infection. The IE-1-specific response occurred to each of the 3 HLA-A*0201-restricted peptides studied (IE-1-256, -297, and -316), and there was no predominant IE peptide response. However, the immunodominant HLA-A*0201-restricted pp65 peptide was recognized significantly more frequently than these IE-1 peptides. When this was compared with the occurrence of CMV infection, the overall immune reactivity, as measured by the mean or median number of CD8+ T cells reactive to either pp65 or IE-1 peptides by intracellular cytokine or tetramer binding assay, was not significantly different in those with and without CMV infection. For patients who demonstrated reconstituted immunity to CMV at 1 year, all were reconstituted by 6 months, and the timing of the first observed immune reactivity to either of the pp65 or the IE peptides was not different in those with and without detectable CMV infection.

DNA and low titer, helper-free, recombinant AAV prime-boost vaccination for cytomegalovirus induces an immune response to CMV-pp65 and CMV-IE1 in transgenic HLA A*0201 mice

A prime-boost immunization regimen allowed the use of low titer, helper-free rAAV-pp65mII and rAAV-IE1 virus to elicit specific humoral and cellular responses to two important cytomegalovirus (CMV) antigens: the immediate-early 1 (IE-1) and pp65 proteins. Simultaneous immunization of both CMV proteins, using DNA vaccine priming followed by rAAV boost, induced antibody (Ab) response, CD8 lymphocytes with cytotoxic function, and detectible binding of the cognate peptide epitopes for human HLA A*0201 restriction using tetramer technology.

Use of transgenic HLA A*0201/Kb and HHD II mice to evaluate frequency of cytomegalovirus IE1-derived peptide usage in eliciting human CD8 cytokine response

Unlike the pp65 protein of human cytomegalovirus (CMV), which has an immunodominant peptide, pp65(495-503), recognized by human CD8(+) cells in the context of HLA A*0201, the fine peptide specificity for CMV IE1 has shown no such immunodominance. With the use of transgenic HLA A*0201/Kb and HHD II mice, a selected pool of IE1 peptides, including IE1(p256-264), IE1(p297-304), and IE1(p316-324), were shown to stimulate cytolytic T-lymphocyte lysis in the context of HLA A*0201. Based on an intracellular gamma interferon response, IE1(p297-304), a previously unrecognized CD8 epitope, triggered a prominent response to CMV IE1 in HLA A*0201 subjects.