Human cytomegalovirus infection elicits a glycoprotein M (gM)/gN-specific virus-neutralizing antibody response

Human cytomegalovirus (HCMV) is a ubiquitous human pathogen that infects 40 to 90% of adult human populations. HCMV infections are often asymptomatic in healthy individuals but can cause severe organ and life-threatening disease in immunocompromised patients. The antiviral antibody response to HCMV infection is complex and is known to include virus-neutralizing antibody production against surface glycoproteins encoded by HCMV. We have investigated the human antibody response to a complex of HCMV surface glycoproteins composed of glycoprotein M (gM)/gN, the gene products of the UL100 and UL73 open reading frames. Mouse monoclonal antibodies generated against gM/gN have previously been shown to neutralize HCMV infection of human fibroblasts in vitro. To determine whether human antibodies reactive with the gM/gN complex possess virus-neutralizing properties, we isolated human antibodies reactive with gM/gN from pooled human HCMV hyperimmune globulin by affinity purification using recombinant gM/gN. The affinity-purified human anti-gM/gN antibodies reacted specifically by immunofluorescence with HCMV-infected human fibroblasts and with cells transiently expressing gM/gN, but not with cells transfected with plasmids encoding other immunogenic HCMV proteins. The anti-gM/gN antibodies also reacted specifically only with gM/gN in immunoblot assays using lysates of transfected cells expressing specific HCMV proteins. Last, human anti-gM/gN antibodies efficiently neutralized infectious HCMV in vitro with a capacity comparable to that of human anti-gB antibodies. These data indicated that gM/gN can elicit a virus-neutralizing antibody response in humans infected with HCMV and therefore should be considered a potential candidate for inclusion in prophylactic CMV vaccines.     

Cytokeratin immunoreactivity in lobular intraepithelial neoplasia.

Eighteen commercially available antibodies reactive against different cytokeratin proteins were tested on classic examples of lobular intraepithelial neoplasia (LIN) and of ductal intraepithelial neoplasia (DIN) of the breast. About 90% of higher-grade DIN (AIDH and DCIS) show no or substantially diminished reaction with clone 34betaE12 (specified as reactive against keratins 1, 5, 10, and 14 as determined by the manufacturer), while the cells of LIN were found to express the antigen reactive with this antibody. To determine which of these four keratins are present in the cells of LIN, antibodies reactive against these individual four keratins were tested. None of the four antibodies to keratins 1, 5, 10, or 14 reacted with the cells of LIN. To investigate this further, 13 additional monoclonal antibodies to various other keratin proteins were tested on the cells of LIN. Those that successfully reacted with the cells of LIN were further tested on the cells of DIN. All of the individual antibodies reactive with the cells of LIN were also reactive with the cells of DIN to a degree, with clone RCK108 (reactive against keratin 19) coming the closest to demonstrating the reactivity seen with 34betaE12. We conclude that the reactivity seen in the cells of LIN with 34betaE12 is due to either (a) a crossreaction with keratin 19 that is slightly less prominent than the reaction of the individual clone RCK108, (b) a crossreaction with a keratin protein that was not tested (3, 11, 12), (c) a crossreaction with a protein closely resembling keratin in formalin-fixed, paraffin-embedded tissue, or (d) the detection of a mutated or truncated form of keratin 1, 5, 10, or 14 that cannot be detected by the individual monoclonal antibody.     

The dominant linear neutralizing antibody-binding site of glycoprotein gp86 of human cytomegalovirus is strain specific.

Bacterial fusion proteins, constructed from overlapping fragments of the open reading frame coding for gp86 of human cytomegalovirus (HCMV) strain AD169, were used to localize antigenic regions recognized by antibodies from human convalescent sera. A major domain for binding of conformation-independent antibodies was localized on fusion protein AP86, containing amino acids 15 to 142 of gp86. Human antibodies, affinity purified on AP86, neutralized infectious virus in tissue culture. In addition, a mouse monoclonal antibody (AP86-SA4), raised against AP86, also neutralized HCMV. AP86-SA4 was reactive with viral gp86 in immunoblot assays and showed a plasma membrane staining on intact HCMV-infected fibroblasts late in infection. After exonuclease III deletions of the viral gene, the binding site of neutralizing human as well as mouse antibodies was localized between amino acid residues 34 and 43. The domain has sequence variation between laboratory strains AD169 and Towne, and binding of the antibodies was strain specific. To our knowledge, this is the first characterization of a strain-specific neutralizing epitope on HCMV.     

High Prevalence of Human Cytomegalovirus Proteins and Nucleic Acids in Primary Breast Cancer and Metastatic Sentinel Lymph Nodes

Background

Breast cancer is a leading cause of death among women worldwide. Increasing evidence implies that human cytomegalovirus (HCMV) infection is associated with several malignancies. We aimed to examine whether HCMV is present in breast cancer and sentinel lymph node (SLN) metastases.

Materials and Methods

Formalin-fixed paraffin-embedded tissue specimens from breast cancer and paired sentinel lymph node (SLN) samples were obtained from patients with (n = 35) and without SLN metastasis (n = 38). HCMV immediate early (IE) and late (LA) proteins were detected using a sensitive immunohistochemistry (IHC) technique and HCMV DNA by real-time PCR.

Results

HCMV IE and LA proteins were abundantly expressed in 100% of breast cancer specimens. In SLN specimens, 94% of samples with metastases (n = 34) were positive for HCMV IE and LA proteins, mostly confined to neoplastic cells while some inflammatory cells were HCMV positive in 60% of lymph nodes without metastases (n = 35). The presence of HCMV DNA was confirmed in 12/12 (100%) of breast cancer and 10/11 (91%) SLN specimens from the metastatic group, but was not detected in 5/5 HCMV-negative, SLN-negative specimens. There was no statistically significant association between HCMV infection grades and progesterone receptor, estrogen receptor alpha and Elston grade status.

Conclusions

The role of HCMV in the pathogenesis of breast cancer is unclear. As HCMV proteins were mainly confined to neoplastic cells in primary breast cancer and SLN samples, our observations raise the question whether HCMV contributes to the tumorigenesis of breast cancer and its metastases.     

The N-terminal 513 amino acids of the envelope glycoprotein gB of human cytomegalovirus stimulates both B- and T-cell immune responses in humans.

Host defense against human cytomegalovirus (HCMV) involves both humoral and cell-mediated immunity. In this report, human immune responses to glycoproteins encoded by the HCMV gB homolog gene have been examined by using glycoproteins purified by immunoaffinity from HCMV virions and recombinant proteins expressed by vaccinia viruses containing either the entire gB open reading frame or a C-terminal deletion mutant, gBm165, coding for the N-terminal 513 amino acids of gB. Neutralizing antibodies, helper T cells, and cytotoxic T cells reactive with epitopes on the N-terminal portion of gB were detected in some seropositive individuals, suggesting that this region of gB may be important in eliciting protective immunity during natural infection for some individuals.     

Interactions between human immunodeficiency virus type 1 and human cytomegalovirus in human term syncytiotrophoblast cells coinfected with both viruses.

Human cytomegalovirus (HCMV) and human immunodeficiency virus type 1 (HIV-1) may interact in the pathogenesis of AIDS. The placental syncytiotrophoblast layer serves as the first line of defense of the fetus against viruses. We analyzed the patterns of replication of HIV-1 and HCMV in singly an dually infected human term syncytiotrophoblast cells cultured in vitro. Syncytiotrophoblast cells exhibited restricted permissiveness for HIV-1, while HCMV replication was restricted at the level of immediate-early and early gene products in the singly infected cells. We found that the syncytiotrophoblasts as an overlapping cell population could be coinfected with HIV-1 and HCMV. HIV-1 replication was markedly upregulated by previous or simultaneous infection of the cells with HCMV, whereas prior HIV-1 infection of the cells converted HCMV infection from a nonpermissive to a permissive one. No simultaneous enhancement of HCMV and HIV-1 expression was observed in the dually infected cell cultures. Major immediate-early proteins of HCMV were necessary for enhancement of HIV-1 replication, and interleukin-6 production induced by HCMV and further increased by replicating HIV-1 synergized with these proteins to produce this effect. Permissive replication cycle of HCMV was induced by the HIV-1 tat gene product. We were unable to detect HIV-1 (HCMV) or HCMV (HIV-1) pseudotypes in supernatant fluids from dually infected cell cultures. Our results suggest that interactions between HIV-1 and HCMV in coinfected syncytiotrophoblast cells may contribute to the transplacental transmission of both viruses.     

Tissue Printing as a Tool for Observing Immunological and Protein Profiles in Young and Mature Celery Petioles

Tissue printing onto membranes such as nitrocellulose is a technique employed to study the localization of proteins, nucleic acids, and soluble metabolites from freshly cut tissue slices. We probed tissue prints of young and mature celery (Apium graveolens) petioles with antibodies raised against two proteins, spinach ribulose-1,5-bisphosphate carboxylase and tomato fruit catalase. The purposes of this study were to determine if these proteins are developmentally regulated and to determine if the patterns and intensities of cross-reactivity of antibodies on tissue blots corresponded only to the presence of specific epitopes or was related to the amount of protein present in any given area on the tissue prints. Different and distinct cross-reactivity patterns were observed with each of the two antibodies used. Tissue prints from young and mature tissues also showed differences in antibody cross-reactivity. Comparison of Coomassie blue staining patterns with antibody reactivity patterns showed that there is little relationship between tissue protein concentration and antibody reactivity.     

Induction of complement-dependent and -independent neutralizing antibodies by recombinant-derived human cytomegalovirus gp55-116 (gB).

The human cytomegalovirus (HCMV) envelope glycoprotein complex gp55-116 was expressed in both Escherichia coli and cells infected with a recombinant vaccinia virus. E. coli produced a single protein of Mr 100,000 which approximated the size of the nonglycosylated gp55-116 precursor found in HCMV-infected cells. Cells infected with the recombinant vaccinia virus contained three intracellular forms of Mr 160,000, 150,000, and 55,000 which were detected by a monoclonal antibody reactive with gp55. Comparison of the immunological properties of these recombinant proteins indicated that several of the HCMV gp55-116 monoclonal antibodies and sera from patients infected with HCMV reacted with the vaccinia virus-derived proteins whereas a more restricted group of monoclonal antibodies recognized the E. coli-produced protein. Immunization of mice with either E. coli or vaccinia virus recombinant HCMV gp55-116 resulted in production of virus-neutralizing antibodies. In contrast to the almost exclusive production of complement-dependent neutralizing antibodies following immunization with recombinant vaccinia virus, the E. coli-derived protein induced complement-independent neutralizing antibodies.     

Epitope analysis of antibodies in Japanese to human cytomegalovirus phosphoprotein 150 with synthetic peptides

Serological detection of antibodies specific to human cytomegalovirus (HCMV) is not reliable because the assay uses the whole HCMV protein fraction. Antigenic materials composed of well-characterized viral proteins are being tried for serodiagnosis in Europe. Epitopes of antibodies to HCMV phosphoprotein 150 (pp150) encoded by UL32 in Japanese individuals were investigated for comparison with the results in Europe. The major epitopes on amino acid residues 496 to 652 of HCMV pp150 were identified and the detection of antibodies with an enzyme-linked immunosorbent assay (ELISA) of synthetic peptides against the main epitopes was established. Fifteen seropositive and five seronegative serum samples for the epitope mapping and 131 seropositive and 50 seronegative samples for ELISA were investigated. Overlapping 15-mer peptides moving by two amino acids through V496-H652 were synthesized. The main epitope regions were V508-D530, L526-Q544, S536-D554, T616-G634, S624-P642, and L632-H652. When each peptide was conjugated with bovine serum albumin for ELISA, 80.9% of the seropositive samples were judged to be positive. The results of this study are the same as those for European sera, so the antigenic materials developed in Europe might be used to replace the whole HCMV protein fraction in Japanese.     

Comparison of different double immunostaining protocols for paraffin embedded liver tissue.

Most of the double immunostaining protocols that have been introduced so far have been developed for application on fresh frozen material or based on different species antibodies. In liver tissue, general problems of double immunostaining techniques are further complicated by tissue-specific difficulties, such as necrosis or high intracellular protein content. To assess a reliable double immunostaining protocol for archived, paraffin embedded liver tissue, different protocols based on the use of same species primary antibodies were evaluated in terms of sensitivity, specificity and non-specific background staining in pathological liver specimens. We compared peroxidase-anti-peroxidase, alkaline phosphatase-anti-alkaline phosphatase (PAP/APAP), labelled-avidin-biotin (LAB/LAB) and digoxigenin-anti-digoxigenin (dig-a-dig/PAP) techniques using different cytokeratin antibodies and an antibody against PCNA. Comparison of the double immunostaining techniques revealed a high sensitivity and specificity in all procedures. Sections, which were stained employing PAP/APAP-technique, displayed a higher background staining compared to sections which were treated with the LAB/LAB or dig-a-dig/PAP protocol. In contrast to the dig-a-dig/PAP protocol, the LAB/LAB technique provides a better time/cost relationship. Therefore, we would like to recommend a modified LAB/LAB protocol for simultaneous detection of different antigens in archived liver tissue.     

Complex formation by human cytomegalovirus glycoproteins M (gpUL100) and N (gpUL73)

The envelope glycoproteins of human cytomegalovirus (HCMV) virions are incompletely characterized. We have analyzed complex formation between glycoprotein M (gM or gpUL100) and a second glycoprotein. gM-homologous proteins are conserved throughout the herpesvirus family and represent type III membrane proteins containing multiple hydrophobic sequences. In extracellular HCMV particles, gM was found to be complexed through disulfide bonds to a second protein with an apparent molecular mass of 50 to 60 kDa. The 50- to 60-kDa protein was found to be derived from reading frame UL73 of HCMV strain AD169. UL73-homologous genes are also conserved within herpesviruses. When transiently expressed by itself, the UL73 gene product consisted of a protein of 18 kDa. However, in the presence of gM, the UL73 gene product was posttranslationally modified to the 50- to 60-kDa species. Thus, gM and the UL73 gene product, which represents the gN homolog of herpesviruses, form a disulfide-linked complex in HCMV virions. Transient expression of gM and gN followed by fluorescence imaging with monoclonal antibodies against either protein demonstrated that complex formation was required for transport of the proteins from the endoplasmic reticulum to the Golgi and trans-Golgi compartments. Finally, we tested the gM-gN complex for reactivity with sera from HCMV-seropositive donors. Whereas most sera failed to react with either gM or gN when expressed alone, 62% of sera were positive for the gM-gN complex. Because a murine monoclonal antibody reactive with gN in the gM-gN complex efficiently neutralizes infectious virus, the gM-gN complex may represent a major antigenic target of antiviral antibody responses.     

Human cytomegalovirus load in fresh and glycerolized skin grafts

This study evaluated the detection of Human Cytomegalovirus (HCMV)-DNA in donors' skin samples. HCMV-DNA was quantified in 100 skin specimens, including 50 fresh samples and as many corresponding glycerol-preserved specimens by a home-made Real Time PCR. HCMV-DNA was detected in 19/50 (38%) fresh specimens and 23/50 (46%) glycerol-preserved (p = n.s.). Nevertheless, the mere detection of HCMV-DNA does not imply the presence of infectious virions and therefore does not imply a risk of HCMV transmission, as treatment with glycerol is particularly efficacious in inactivating viral particles. Therefore, HCMV serology confirms its pivotal role in the setting of skin grafting.     

Pathogenesis of Experimental Rhesus Cytomegalovirus Infection

Human cytomegalovirus (HCMV) establishes and maintains a lifelong persistence following infection in an immunocompetent host. The determinants of a stable virus-host relationship are poorly defined. A nonhuman primate model for HCMV was used to investigate virological and host parameters of infection in a healthy host. Juvenile rhesus macaques (Macaca mulatta) were inoculated with rhesus cytomegalovirus (RhCMV), either orally or intravenously (i.v. ), and longitudinally necropsied. None of the animals displayed clinical signs of disease, although hematologic abnormalities were observed intermittently in i.v. inoculated animals. RhCMV DNA was detected transiently in the plasma of all animals at 1 to 2 weeks postinfection (wpi) and in multiple tissues beginning at 2 to 4 wpi. Splenic tissue was the only organ positive for RhCMV DNA in all animals. The location of splenic cells expressing RhCMV immediate-early protein 1 (IE1) in i.v. inoculated animals changed following inoculation. At 4 to 5 wpi, most IE1-positive cells were perifollicular, and at 25 wpi, the majority were located within the red pulp. All animals developed anti-RhCMV immunoglobulin M (IgM) antibodies within 1 to 2 wpi and IgG antibodies within 2 to 4 wpi against a limited number of viral proteins. Host reactivity to RhCMV proteins increased in titer (total and neutralizing) and avidity with time. These results demonstrate that while antiviral immune responses were able to protect from disease, they were insufficient to eliminate reservoirs of persistent viral gene expression.     

Monoclonal antibodies to type V collagen for immunohistological examination of new tissue deposition associated with biomaterial implants

We developed a panel of highly specific monoclonal antibodies (MAb) against dog Type V collagen. Each antibody showed differential reactivities towards Type V collagen from other species. All the antibodies were highly reactive in conventional ELISA, as well as with electroblots of collagen after polyacrylamide gel electrophoresis using non-denaturing conditions. The MAb were shown to be suitable for the immunohistological detection of Type V collagen in tissue sections, although this normally required pre-treatment of sections with 50 mM acetic acid. In particular, the antibodies were shown to be useful for examining samples of a collagen-based biomaterial, a vascular prosthesis, after explant from evaluation in an animal model. This showed that Type V collagen was most prominent in regions of new tissue formation within the neointima, close to the inner surface of the prosthesis. The broad spectrum of differential reactivities allows the antibodies to be used for a wide range of experimental models. These MAb therefore provide a novel approach for the evaluation of biomaterial performance, particularly for collagen-based implants.     

Application of cryo-compatible antibodies to human placenta paraffin sections

The hepes-glutamic acid buffer-mediated organic solvent protection effect (HOPE) -fixation and paraffin embedding technique has been described to expand possibilities for immuno-labellings due to low denaturation of proteins. In this study, the issue was addressed as to whether the HOPE technique could be a useful tool in placenta tissue-based studies when only cryo-compatible antibodies are available. Such antibodies can be used on cryostat sections only, giving results of considerably inferior morphological detail as compared to routinely fixed paraffin embedded tissue sections. Commercially available, only cryo-compatible, monoclonal antibodies against a conformational epitope of HLA-G (clone MEM-G/9) and leukocyte differentiation antigens CD56, CD163 and CD34 III were selected and applied to frozen sections, routinely formalin-fixed and HOPE-fixed paraffin sections. All tested antibodies immunolocalized their antigen on cryo sections and on HOPE-fixed but not formalin-fixed paraffin sections. The HOPE technique provides an excellent preservation of protein antigenicity together with well presented morphological details in paraffin embedded placenta tissues. The detection of native or conformation-dependent epitopes in paraffin sections expands the immunolocalization possibilities in placenta research and reproductive immunology.     

General characterization of human cytomegalovirus-specific proliferative CD4+ T cell clones

Over 80 human T helper cell (Th) clones reactive with human cytomegalovirus (HCMV) were generated using purified whole Towne strain HCMV as the in vitro antigen. These cloned T cells are CD3+, CD4+, CD8- and proliferate specifically to HCMV. All of the clones tested produce interleukin 2 and gamma-interferon and failed to show HCMV-specific cytotoxicity or natural killer (NK) activity. Most of the Th clones recognize multiple laboratory-adapted and wild-type strains of HCMV. The Th clones were also tested for their reactivity to a major envelope glycoprotein complex (gcI) and a 64,000 dalton internal matrix protein. Our results show that both proteins as well as other unidentified protein(s) are involved in Th responses to HCMV.     

The validation of new aromatase monoclonal antibodies for immunohistochemistry--a correlation with biochemical activities in 46 cases of breast cancer

Intratumoral aromatase is a therapeutic target for the treatment of post-menopausal estrogen-dependent breast cancers. Therefore, reliable methods should be developed for routine application for the detection of intratumoral aromatase. Immunohistochemistry (IHC) is considered one of the most suitable methods in this regard. A multi-centre collaborative group has been established to generate and validate new aromatase monoclonal antibodies. We have selected two monoclonal antibodies, #677 against native aromatase protein and F2 against formalin-fixed protein for this purpose. With these two monoclonal antibodies 43 cases of invasive ductal carcinoma, which had been previously assayed for aromatase activity by product isolation methodology, were immunostained in three laboratories in UK, USA and Japan and independently evaluated by three pathologists (H.S., T.A. and S.G.S.). Staining of malignant epithelium, adipose tissue, normal/benign and stromal compartments of the tumors were assessed by estimating the proportion of positive staining cells and the relative intensity of staining in this fashion. Immunoreactivity could be detected in each component of the tissue specimens but a significant positive correlation with biochemical activity was detected only in malignant epithelium stained with 677 not in other components with #677 and not in any of the components. Staining using F2 as a primary antibody did not produce a positive correlation in any components with aromatase activity. These results suggest that we now have a monoclonal antibody against aromatase (#677) which may be used to stain archival materials. A methodology and scoring system is recommended whereby staining significantly correlates with aromatase activity of the resected tissue specimens of breast cancer.