Oral administration of recombinant Mycobacterium smegmatis expressing a tripeptide construct derived from endogenous and microbial antigens prevents atherosclerosis in ApoE(-/-) mice

INTRODUCTION

Immunotherapy by inducing oral tolerance to atherogenic self-antigens is gaining importance as an alternative treatment modality for atherosclerosis. The use of live bacterial vectors to express the recombinant antigen in vivo will obviate the need for large-scale purification of recombinant protein and may also augment the efficacy of oral tolerance induction.

AIM

The objective of the study was to explore the use of recombinant Mycobacterium smegmatis as a live vector for oral delivery of antigens to induce immune tolerance.

METHOD AND RESULTS

We developed a M. smegmatis vector to secrete a recombinant tripeptide construct (AHC; peptides from Apolipoprotein B, Heat-shock protein 60 and Chlamydia pneumoniae outer membrane protein) expressed in a dendroaspin protein scaffold in pJH154 background. Immune response and oral tolerance to the cloned peptides were studied in C57/BL6 mice. The efficacy of this live vaccine to control atherosclerosis was studied in ApoE(-/-) knockout mice in C57/BL6 background. Oral administration of M. smegmatis secreting the cloned AHC antigen was found to induce tolerance to cloned protein and reduce the development of atherosclerosis by 24.0% compared to control. Protection against atherosclerosis was associated with increase in expression of regulatory T cell-associated markers including CTLA4 (1.8-fold), Foxp3 (2.6-fold), TGF-β (2.8-fold), IL10 (2.9-fold), and reduction in lipids, macrophage infiltration, and expression of inflammatory mediators in aorta.

CONCLUSIONS

Our results suggest that M. smegmatis can be developed as an oral carrier of recombinant proteins to treat inflammatory autoimmune diseases.

Modulation of recombinant antigenic constructs containing multi-epitopes towards effective reduction of atherosclerotic lesion in B6;129S-Ldlr(tm1Her)Apob(tm2Sgy)/J mice

Atherosclerosis is increasingly recognized as a complex chronic inflammatory disease. Many more studies have extended vaccination against atherosclerosis by using epitopes from self-antigens or beyond and demonstrated that vaccination with antigens or derivatives could reduce the extent of the lesions in atherosclerosis-prone mice. Our previous study has demonstrated that construct AHHC [ApoB100688-707 + hHSP60303-312 + hHSP60153-163 + Cpn derived peptide (C)] significantly reduced atherosclerotic lesion. The aim of this study was to investigate whether AHHC can be modulated towards increased lesion reduction in mice by creating two other derivatives with a sequential epitope-substitution named RHHC in which A was replaced by an "R" (C5aR1-31) and RPHC with a further "H" (hHSP60303-312) conversion into "P" (protease-activated receptor-142-55) in mice. Antigenic epitopes were incorporated into a dendroaspin scaffold. Immunization of B6;129S-Ldlrtm1HerApobtm2Sgy/J mice with three constructs elicited production of high levels of antibodies against each epitope (apart from hHSP60153-163 and P which induced a low antibody response). Histological analyses demonstrated that the mice immunized with either RPHC or RHHC showed significant reductions in the size of atherosclerostic lesions compared to those with AHHC (69.5±1.1% versus 55.7±3.4%, P<0.01 or 65.6±1.3% versus 55.7±3.4%, P<0.01). Reduction of plaque size in the aortic sinus and descending aorta correlated with alterations in cellular immune responses when compared with controls. We conclude that a recombinant construct RPHC may provide new antigenic and structural features which are favorable for significant reduction in atherosclerotic lesion formation. This approach offers a novel strategy for developing anti-atherosclerotic agents.

Immunization of Chlamydia pneumoniae (Cpn)-infected Apob(tm2Sgy)Ldlr(tm1Her)/J mice with a combined peptide of Cpn significantly reduces atherosclerotic lesion development

Objective

To investigate the antigenic effect of a peptide containing two epitopes of Chlamydia pneumoniae (Cpn) on atherosclerotic lesion formation in mice infected with Cpn.

Materials and Methods

Six-week-old Apob^tm2SgyLdlr^tm1Her/J mice were immunized using a repetitive immunization multiple-sites strategy with KLH-conjugated peptides derived from the major outer membrane protein and the putative outer membrane protein 5 of Cpn. Mice were fed a high-fat diet and infected with Cpn twice during the 10-week diet period. Lesions were evaluated histologically; local and systemic immune responses were analyzed by immunohistochemistry of aorta samples and cytokine measurements in plasma samples and splenocyte supernatants.

Results

Mice immunized with the combined Cpn peptide showed a greater reduction in lesion size compared to mice immunized with either epitope alone [54.7% vs 39.8% or 41.72%] and was also associated with a significant decrease in lesion area in descending aortas compared with those in controls (88.9% for combined Cpn peptide, 81.9% for MOMP peptide and 75.7% for Omp5, respectively). This effect was associated with a shift in the cellular composition of plaques towards decreased inflammatory cell and increased regulatory T-cell content. Additionally, the effect was also connected with decreased secretion of proinflammatory cytokines and increased production of anti-inflammatory cytokines demonstrated in plasma and in supernatant on stimulated spleen cells.

Conclusions

Atherosclerotic lesion formation may be promoted by Cpn infection in the presence of a high-fat diet, and reduced by immunization with the combined Cpn peptide. The combined peptide has more potential than either epitope alone in reducing atherosclerotic lesion development through Treg expansion.

Isocitrate lyase encoding plasmids in BCG cause increased survival in ApoB100-only LDLR-/- mice

We studied the role of isocitrate lyase in the interaction between Mycobacterium bovis BCG and mice. ApoB100-only LDLR-/- (B6;129S-ApoBtm2SgyLdlrtm1Her/J) mice were inoculated with M. bovis BCG harbouring plasmids carrying the gene for isocitrate lyase. The presence of ~29 times more copies of this gene resulted in a higher bacterial yield in the spleens and lungs of the infected mice. The spleen was 3-4 times heavier, and in the spleen the bacteria survived over 10 days longer than did the bacteria with the control plasmid. Propionate was less toxic for bacteria carrying icl plasmids in vitro. This recombinant BCG can be a possible vaccine candidate.

Immunization With a Combination of 2 Peptides Derived From the C5a Receptor Significantly Reduces Early Atherosclerotic Lesion in Ldlr tm1Her Apob tm2Sgy J Mice

Objective—

The goal of this study was to assess whether immunization of Ldlr tm1Her Apob tm2Sgy J mice with 2 peptides located at the N-terminus of the C5a receptor (C5aR), either alone or in combination, is effective in reducing atherosclerotic lesions.

Methods and Results—

Five- to 6-week-old female Ldlr tm1Her Apob tm2Sgy J mice were immunized using a repetitive immunization multiple sites strategy with keyhole limpet hemocyanin-conjugated peptides derived from the C5aR, either alone (designated as C5aR-P1 [aa 1–21] and C5aR-P2 [aa 19–31]) or in combination (designated as C5aR-P1+C5aR-P2). Mice were fed a high-fat diet for 10 weeks. Lesions were evaluated histologically; local and systemic immune responses were analyzed by immunohistochemistry of aorta samples and cytokine measurements in plasma samples and splenocyte supernatants. Immunization of Ldlr tm1Her Apob tm2Sgy J mice with these peptides elicited high concentrations of antibodies against each peptide. Immunization with the single peptide inhibited plaque development. Combined inoculation with C5aR-P1+C5aR-P2 had an additive effect on reducing the lesion in the aorta sinus and descending aortas when compared with controls. This effect correlated with cellular infiltration and cytokine/chemokine secretion in the serum or in stimulated spleen cells as well as specific cellular immune responses when compared with controls.

Conclusion—

Immunization of mice with C5aR-P1 and C5aR-P2, either alone or in combination, was effective in reducing early atherosclerotic lesion development. The combined peptide is more potential than either epitope alone to reduce atherosclerotic lesion formation through the induction of a specific Treg cell response as well as blockage of monocyte differentiation into macrophages.

Transcriptome analysis indicates an enhanced activation of adaptive and innate immunity by chlamydia-infected murine epithelial cells treated with interferon γ

BACKGROUND

Interferon γ (IFN‐γ) is the major cytokine involved in the elimination of Chlamydia infection. Despite its importance, the combined effect of Chlamydia infection and IFN‐γ on the gene expression of murine epithelial cells has only partially been described.

METHODS

The DNA chip method was used to evaluate the impact of IFN‐γ and both the human strain Chlamydia trachomatis L2 infection and the murine strain Chlamydia muridarum infection on the transcriptome of murine epithelial cells.

RESULTS

The gene expression analysis revealed that IFN‐γ had an enhancing effect on both the up‐regulation and down‐regulation of the epithelial gene expression. The influenced gene functional classes included cytokine and chemokine expression, antigen presentation, apoptosis, and genes involved in basic metabolic processes such as fatty acid oxidation. We also detected the up‐regulation of various genes that could be directly antichlamydial, such as members of the p47 GTPase family, inducible nitric oxide synthase, and monokine induced by IFN‐γ (MIG). As a functional validation of DNA chip data, we measured the antichlamydial effect of MIG on the extracellular form of Chlamydia.

CONCLUSIONS

Our results show that IFN‐γ is a key cytokine that primes epithelial cells to activate adaptive and innate immunity and to express antichlamydial effector genes both intracellularly and extracellularly.

Immunization with a combination of ApoB and HSP60 epitopes significantly reduces early atherosclerotic lesion in Apobtm2SgyLdlrtm1Her/J mice

OBJECTIVE

HSP60 is emerging as an immunodominant target of autoantibodies in atherosclerosis and recent studies have revealed oxLDL as a key antigen in the development of atherosclerosis. In this study, we assay whether immunizing Apobtm2SgyLdlrtm1Her/J mice with a combination of ApoB and human HSP60 peptides has an additive effect on atheroprotection compared to ApoB or HSP60 peptides applied alone by following atherosclerotic lesion development.

METHODS AND RESULTS

In this study, 2 weeks after the first immunization, Apobtm2SgyLdlrtm1Her/J mice were placed on a high-fat diet for 8 weeks followed by 2 weeks on a normal diet allowing the mice to adapt to the environment before sacrifice. High levels of ApoB and HSP60 antibodies were detectable in week 2 and week 12 following the first immunization with KLH-conjugated ApoB and HSP60 peptides either individually or in combination. Histological analyses demonstrated that mice immunized with both, ApoB and HSP60 peptides, showed the most significant reduction in atherosclerotic lesions (41.3%; p<0.001) compared to a reduction of 14.7% (p<0.05) and 21.1% (p<0.01) in mice immunized with ApoB or HSP60 peptides, respectively; control mice were immunized with either PBS or adjuvant alone. These results were further supported by significant differences in the cellular and humoral immune responses between test animals.

CONCLUSIONS

Immunization with a combination of ApoB and HSP60 peptide antigens significantly reduced early atherosclerotic lesions in the Apobtm2SgyLdlrtm1Her/J mouse model of atherosclerosis. This approach offers promise as a novel strategy for developing anti-atherosclerotic agents.

Inflammatory- and immune responses in relation to bacterial replication in mice following re-infections with Chlamydophila pneumoniae

OBJECTIVE

Investigation of chronic infections with Chlamydophila pneumoniae.

METHODS

BALB/c mice were repeatedly infected with C. pneumoniae and tested during a 1-year period. Production of histamine, IFN-gamma, IL-6 and antibodies was monitored by ELISA. Live bacteria were cultured and DNA was detected by PCR. Cellular immunity was tested by ELISPOT.

RESULTS

After re-infections, culture positivity and persistence of DNA in lungs and blood were shorter. Detection of DNA at late time points indicated persistent infection in a few mice. Histamine was produced after primary and re-infections, and the level correlated with the number of viable bacteria in lung. IFN-gamma, IL-6 levels, IgG2/IgG1 ratio, IgA titres, and level of chlamydial heat-shock protein antibodies were higher after re-infections. IgM antibodies were demonstrated even after re-infections. High number of IFN-gamma-producing splenocytes was observed after the third inoculation.

CONCLUSION

These results promote an understanding of the patho- and immune mechanisms after C. pneumoniae re-infections.

Expression of bacterial genes and induction of INF-gamma in human myeloid dendritic cells during persistent infection with Chlamydophila pneumoniae

The interactions between human monocyte-derived dendritic cells (DCs) and Chlamydophila pneumoniae (Cpn) infection were investigated. Cpn infection induced the maturation and functional activation of DCs, and Cpn antigens were present in all of the subpopulations during the maturation process. Chlamydial antigens were detected in DCs during an observation period of 28 days. The exponential production of infectious elementary bodies was not observed. Chlamydial transcripts of the 16S rRNA gene, groEL-1 and omcB genes were expressed, as determined by a quantitative real-time PCR, but the expression of the ftsK gene was limited. DC cultures produced IFN-gamma, but the presence of IFN-gamma in the culture medium was not the major factor that decreased the growth of Cpn, as was shown by neutralization of the IFN-gamma. A cell population identified as producing IFN-gamma had no markers for T, B, natural killer, monocyte cells or macrophages but displayed DC morphology and the expression of specific DC markers, such as CD11c and HLA-DR. These results reveal a persistent infection of DCs with the expression of some, but not cell division-related genes and the production of IFN-gamma that may contribute to the pathomechanism of chronic inflammatory diseases associated with persistent Cpn infection.

Chronic infections and histamine, CRP and IL-6 levels after percutaneous transluminal coronary angioplasty

OBJECTIVE AND DESIGN

Our hypothesis was that percutaneous transluminal coronary angioplasty (PTCA) reactivates certain pathogens that contribute to inflammatory processes after the intervention.

SUBJECTS

We determined the levels of antibodies to human Hsp60 and levels of histamine, CRP and IL-6 in sera from 28 patients of unstable angina prior to and on days 4 and 14 after PTCA. We compared the presence of Chlamydophila pneumoniae (Cpn) and human cytomegalovirus (HCMV) DNA in peripheral blood, and levels of antibodies to Cpn, HCMV, herpes simplex virus, Epstein-Barr virus and mycobacterial Hsp65 in the serum.

RESULTS

Higher prevalence of Cpn and HCMV DNA was demonstrated after PTCA than before, but titers of antibodies to the pathogens did not increase. Levels of histamine, CRP and IL-6 were enhanced after PTCA. There was no association between the levels of histamine, CRP and IL-6 and the rate of pathogen DNA, or antibody titers to the pathogens, except an association between Cpn IgA and histamine levels before PTCA.

CONCLUSIONS

Reactivation of Cpn and HCMV and inflammatory change characterized by increased levels of histamine, CRP and IL-6 following PTCA are suggested. An association might exist between Cpn IgA antibody and histamine levels in patients of unstable angina.

Chronic infections and genetic factors in the development of ischemic stroke

The aim of this study was to examine whether chronic infections and genetic factors of the host play roles in the pathophysiology of acute noncardioembolic ischemic stroke. Blood samples from 59 subjects with ischemic stroke and 52 control patients were investigated by nested PCR for the presence of C. pneumoniae DNA, HCMV DNA and enterovirus RNA, by ELISA for the levels of antibodies to C. pneumoniae, HCMV, HSV, HHV-6, EBV and the inflammatory chemokine IL-8, and by PCR for promoter polymorphism of the IL-8 and CD14 host genes. Associations of stroke with the HCMV IgG and HSV-1 IgA antibody levels were observed. No association of stroke was detected with the presence of C. pneumoniae, HCMV or enterovirus nucleic acids in the peripheral blood, C. pneumoniae IgM, IgG and IgA, the HSV IgG, the EBV IgG, or HHV-6 IgG antibody levels, the pathogen burden, the IL-8 or CD14 promoter polymorphisms, or with the serum levels of IL-8 in the overall study population. These results are consistent with the hypothesis that certain pathogens are involved in the development of ischemic stroke.

A soluble factor(s) released by MRC-5 cells early and late after human cytomegalovirus infection induces maturation of monocyte-derived dendritic cells

A human cytomegalovirus (HCMV) strain passaged 10 times on MRC-5 human fibroblast cells failed to express immediate early (IE) antigens in immature dendritic cells (iDCs) after infection. However, both the early and the late HCMV conditioning medium, harvested from MRC-5 cells at 24 h or 7-9 days after infection, respectively, induced a higher ratio of DCs expressing maturation markers (CD40, CD83, CD86 and HLA-DR) on the surface of the cells. HCMV conditioning medium, ultracentrifuged to remove virus particles, exhibited a similarly enhanced expression of DC maturation markers. DCs treated with HCMV conditioning medium harvested late after infection increased the percentages of autologous CD4+ and CD8+ cells of seropositive donors to produce IFN-gamma and stimulated HCMV-specific lymphoproliferative responses. The early HCMC conditioning medium was also able to induce the functional maturation of DCs, as demonstrated by supplementing this medium with a Chlamydia pneumoniae antigen.

Chlamydophila pneumoniae and human cytomegalovirus in atherosclerotic carotid plaques--combined presence and possible interactions

The aim of our study was to investigate the combination of Chlamydophila pneumoniae and human cytomegalovirus (HCMV) as a pathogenic factor in atherosclerosis. Accordingly, we tested by means of PCR and immunohistochemistry the presence of these pathogens in the same atherosclerotic carotid specimen. The histology of the samples and the patients' antibodies against these pathogens were evaluated. Further, we examined the impact of C. pneumoniae and HCMV infection on the gene expression of the human monocytic cell line U937. Six of the 22 samples contained only C. pneumoniae, 4 contained only HCMV, 7 contained both C. pneumoniae DNA and/or antigens of both pathogens, and 5 samples were negative. No correlation was found between the presence of these microbes and either the cellular structure of the plaques, or the serostatus of the patients. The infection of U937 cells with HCMV and especially C. pneumoniae induced inflammation and atherosclerosis-related genes. Furthermore, the doubly-infected cells produced higher levels of the mRNA of pro-platelet basic protein and fatty acid binding protein 4. In conclusion, C. pneumoniae is often present in combination with HCMV in atherosclerotic carotid lesions. The in vitro coinfection model reveals that the doubly-infected monocytes are potent expressors of proatherosclerotic genes, suggesting that this coinfected population may accelerate the process of atherosclerosis.

The interactions between human dendritic cells and microbes; possible clinical applications of dendritic cells

The dendritic cells comprise several subsets that induce and regulate the immune responses against foreign and self-antigens, and that can therefore function as initiators of protective immunity and inducers of central or peripheral tolerance. The different subpopulations of dendritic cells interact with and also influence other cell populations of the immune system, such as T and B lymphocytes and natural killer cells. The factors that determine the given dendritic cell functions depend on the state of maturation and the local microenvironment. The interactions between dendritic cells and microorganisms are rather complex, but progress in the past few years has shed light on several aspects of these interactions. This review lays emphasis on the interactions between human dendritic cells, important components of the intima of arterial specimens at areas predisposed to atherosclerotic lesions, and Chlamydia pneumoniae and cytomegalovirus, the human pathogens most strongly implicated in the development of atherosclerosis. In addition, several examples of the potential clinical applications of dendritic cells are described.

Elevated antibody levels against Chlamydia pneumoniae, human HSP60 and mycobacterial HSP65 are independent risk factors in myocardial infarction and ischaemic heart disease

The relative significance of traditional risk factors, chronic infections and autoimmune processes in the development of acute myocardial infarction (AMI) has not been fully elucidated. We compared serum IgG antibody titres to various pathogens, i.e. Chlamydia pneumoniae (Cpn), cytomegalovirus (CMV) and herpes simplex virus type 1 (HSV-1), and to the potential autoantigens human heat shock protein 60 (hHSP60) and mycobacterial heat shock protein 65 (mHSP65), in serum samples obtained from patients 3-48 h after AMI (n = 40) or stable effort angina (SEA, n = 43), and from controls (n = 46). The strongest association was observed between AMI and the elevated level of hHSP60 antibodies. The association between AMI and the level of Cpn antibodies was also significant. High levels of hHSP60 and Cpn antibodies represented independent risk factors for the development of AMI, but the simultaneous presence of high levels of antibodies to Cpn and hHSP60 suggested a joint effect on the relative risk of AMI (OR = 12.0-21.1). The antibody titres to mHSP65 were higher in the SEA group than in the controls, and the simultaneous presence of high levels of Cpn and mHSP65 antibodies meant an increased risk among the SEA patients. The antibody titres to CMV or HSV-1 were similar in the three groups. In conclusion, these results demonstrate associations of AMI with high levels of anti-hHSP60 and anti-Cpn antibodies, and of SEA with the level of anti-mHSP65 antibodies, these being independent risk factors.

Infection of U937 Monocytic Cells withChlamydia pneumoniaeInduces Extensive Changes in Host Cell Gene Expression

The effect of infection with Chlamydia pneumoniae on host messenger RNA expression in human monocytic cells with complement DNA microarrays was studied. The data chronicle a cascade of transcriptional events affecting 128 genes, many of which have not previously been reported to be affected by C. pneumoniae infection. Down-regulated genes are primarily associated with RNA and DNA metabolism, chromosomal stability, and cell-cycle regulation. Up-regulated messages include those for a variety of genes with important proinflammatory functions. Many of the up-regulated genes-including the hyaluron receptor CD44, vasoconstrictor endothelin-1, smooth muscle growth factor heparin-binding EGF-like growth factor, and fatty acid binding protein-4-had been previously described as linked to the development of atherosclerosis and other chronic inflammatory diseases. C. pneumoniae-infected monocytes can contribute to the development and progression of diseases for which acute or chronic inflammation has been shown to be important, such as atherosclerosis.

Chlamydia pneumoniae exacerbates aortic inflammatory foci caused by murine cytomegalovirus infection in normocholesterolemic mice

Inflammatory foci induced by murine cytomegalovirus infection in normocholesterolemic mice were present temporarily in the aortic wall, but some of these foci developed into advanced lesions that persisted late after infection. The early foci induced by virus infection were significantly exacerbated following a single inoculation with Chlamydia pneumoniae.

Independent and joint effects of antibodies to human heat-shock protein 60 and Chlamydia pneumoniae infection in the development of coronary atherosclerosis

BACKGROUND

Studies have suggested that the prevalence of antibodies against heat-shock proteins (HSPs), Chlamydia pneumoniae (CPN), and cytomegalovirus (CMV) is associated with coronary artery disease (CAD), but the independent or joint effects of human (h) HSP60 antibodies and these pathogens in patients have not been fully elucidated.

METHODS AND RESULTS

A total of 405 subjects (276 patients with CAD and 129 control individuals) were tested for serum antibodies to hHSP60, CPN, and CMV immediate-early-1 (IE1) antigens. Patients were also assessed for serum cholesterol, triglyceride levels, and smoking habit. Significantly elevated levels of antibodies to hHSP60 and CPN but not to CMV-IE1 antigens were documented in CAD patients. Multiple logistic regression analysis and subanalyses of selected subjects showed that these associations were independent of age, sex, smoking, and serum lipid levels. Antibodies to hHSP60 and CPN did not correlate quantitatively; however, the relative risk of disease development was substantially increased in subjects with high antibody levels to both hHSP60 and CPN:, reaching an odds ratio of 82.0 (95% CI 10.6 to 625.0).

CONCLUSIONS

High levels of antibodies to hHSP60 and CPN: are independent risk factors for coronary atherosclerosis, but their simultaneous presence substantially increases the risk for disease development.

Cytotoxic T lymphocyte (CTL) responses to human cytomegalovirus pp65, IE1-Exon4, gB, pp150, and pp28 in healthy individuals: reevaluation of prevalence of IE1-specific CTLs

The prevalence of human cytomegalovirus (HCMV) pp65-, pp150-, IE1-exon4-, gB- and pp28-specific cytotoxic T lymphocyte (CTL) responses was compared among 34 healthy individuals, grouped by neutralizing antibody titers. Moderately and highly seropositive donors showed predominantly pp65- and IE1-exon4-specific CTL responses (92% and 76% of the donors, respectively), with similar precursor frequencies in the 2 donors tested. In addition, highly seropositive and a few moderately seropositive donors showed CTL responses to gB and pp150 (33% and 30% of the donors, respectively). No individual recognized pp28 as a target in the CTL assay. Phenotypic analysis revealed a mixed effector population of CD4+ and CD8+ (1 donor) or only CD8+ cells for pp65-specific effectors (2 donors). IE1-exon4- and pp150-specific effectors were CD8+ (2 donors and 1 donor, respectively), whereas gB-specific CTLs were CD4+ (1 donor). These data may help to design a cellular immunity-based vaccine effective against HCMV diseases.

Induction of human cytomegalovirus (HCMV)-glycoprotein B (gB)-specific neutralizing antibody and phosphoprotein 65 (pp65)-specific cytotoxic T lymphocyte responses by naked DNA immunization

Plasmids expressing the human cytomegalovirus (HCMV) glycoprotein B (gB) (UL55) or phosphoprotein 65 (pp65) (UL83) were constructed and evaluated for their ability to induce immune responses in mice. The full-length gB as well as a truncated form expressing amino acids 1-680 of gB, and lacking the fragment encoding amino acids 681 907 including the transmembrane domain of gB (gB680) were evaluated. Immunization of mice with plasmids coding for gB or gB680 induced ELISA and neutralizing antibodies, with the highest titres in mice immunized with the gB680 plasmid. Mice immunized with the gB plasmid predominantly produced IgG2a gB-specific antibody, while the gB680 plasmid raised mostly IgG1 anti-gB antibody. Mice immunized with the pp65 plasmid developed pp65-specific cytotoxic T lymphocytes (CTL) and ELISA antibodies. Immunization with a mixture of both gB and pp65 plasmids raised antibodies to both proteins and pp65-specific CTL, indicating a lack of interference between these two plasmids. These results suggest that DNA immunization is a useful approach for vaccination against HCMV disease.

Early atherosclerotic plaques in the aorta following cytomegalovirus infection of mice

We show here that BALB/c mice inoculated with murine cytomegalovirus (MCMV) express viral antigens in the endothelial and smooth muscle cells of the aortic wall, and that accumulation of inflammatory cells in the aortic lumen, similar to that seen in early atherosclerotic lesions in humans, colocalizes with the site of virus antigen expression. Immunosuppression of the mice at the time of virus infection increased the expression of viral antigens and the size of early atherosclerotic lesions in the intima. The percentage of the low-density lipoprotein cholesterol (LDL-C), the major lipid contributor to atherosclerotic plaques, was significantly increased in the serum of MCMV-infected mice, whether or not the mice were fed a high cholesterol diet. Human cytomegalovirus (HCMV) significantly increased the esterified cholesterol component of the total cholesterol in a human arterial smooth muscle cell line infected in vitro with HCMV. These results suggest that CMV infection is involved in two of the major mechanisms that lead to development of atherosclerosis, i.e., immune injury and high LDL-C.

The N-terminal 303 amino acids of the human cytomegalovirus envelope glycoprotein B (UL55) and the exon 4 region of the major immediate early protein 1 (UL123) induce a cytotoxic T-cell response

We reported earlier that an adenovirus (Ad) recombinant expressing the full-length human cytomegalovirus (HCMV) glycoprotein B (gB) gene induces gB-specific cytotoxic T lymphocyte (CTL) responses in CBA (H-2k) mice (Berencsi et al., J. Gen. Virol. 74, 257-2512, 1993). Here we show that mice immunized with Ad recombinant viruses expressing truncated forms of the gB gene containing the first 700 (Ad-700), 465 (Ad-465) or 303 (Ad-303) amino acids of gB or an Ad construct containing exon 4 (E4) of the HCMV immediate early 1 (IEI) gene (Ad-IEI (E4)) demonstrate HCMV-specific CTL responses. These data suggest the importance of the first 303 amino acids of the gB polypeptide and the IEI E4 product in designing a vaccine to induce anti-HCMV CTL responses.

Preclinical evaluation of an ALVAC (canarypox)--human cytomegalovirus glycoprotein B vaccine candidate

Successful vaccination against the human cytomegalovirus (HCMV) requires induction of both neutralizing antibody and cytotoxic T lymphocyte (CTL) responses. The HCMV glycoprotein B (gB, UL55) would be one of the most important immunogens to induce neutralizing antibodies. We tested the immunogenicity of an ALVAC (canarypox)-HCMV-gB (ALVAC-gB) recombinant in mice and guinea pigs in order to provide preclinical data for a phase I clinical trial of a HCMV vaccine candidate. ALVAC is an attenuated vaccine strain of canarypox virus which replicates productively in avian species but abortively in mammalian cells. The ALVAC-gB recombinant inoculated subcutaneously in mice and intramuscularly in guinea pigs induced HCMV-specific neutralizing antibodies and gB-specific CTL responses. Ultraviolet irradiation of the ALVAC-gB recombinant before immunization diminished CTL responses, indicating that intracellular expression and processing of gB-protein were necessary for CTL induction. Prior immunity to vaccinia virus did not decrease immunogenicity of the ALVAC-gB recombinant in mice. Thus, despite its host range restriction, ALVAC-gB is potentially capable of inducing both humoral and cell-mediated immune responses to HCMV in both vaccinia-immune and non-immune individuals.

Difference in the production of human interferon-alpha and -beta in mouse cells

Human interferon-alpha 1 and interferon-beta genes with their flanking regions were introduced into mouse LMTK- cells. Although transfected cells contained the interferon genes with a similar copy number and produced a similar amount of interferon-specific mRNA, cells containing the human interferon-beta gene secreted about 10 times more human interferon than cells transfected with the human interferon-alpha 1 gene. When the coding region of the interferon-beta gene was replaced by that of the interferon-alpha 1 gene (hybrid interferon beta/alpha gene), the human interferon production of transfected cells fell by approx. one order of magnitude. These results show that in the case of exogenous interferon genes a translational or post-translational mechanism might significantly affect the final level of human interferons, resulting in higher titres of interferon-beta than of interferon-alpha.