Matrix Matters: Assessment of Commutability among BK Virus Assays and Standards

Quantitative testing of BK virus (BKPyV) nucleic acid has become the standard of care in transplant patients. While the relationship between interassay harmonization and commutability has been well characterized for other transplant-related viruses, it has been less well studied for BKPyV, particularly regarding differences in commutability between matrices. Here, interassay agreement was evaluated among six real-time nucleic acid amplification tests (NAATs) and one digital PCR (dPCR) BKPyV assay. Differences in the commutability of three quantitative standards was examined across all assays using a variety of statistical approaches. Panels, including 40 samples each of plasma and urine samples previously positive for BKPyV, together with one previously negative plasma sample and four previously negative urine samples, were tested using all assays, with each real-time NAAT utilizing its usual quantitative calibrators. Serial dilutions of WHO, National Institute for Standards and Technology (NIST), and commercially produced (Exact/Bio-Rad) reference materials were also run by each assay as unknowns. The agreement of the clinical sample values was assessed as a group and in a pairwise manner. The commutability was estimated using both relativistic and quantitative means. The quantitative agreement across assays in the urine samples was within a single log10 unit across all assays, while the results from the plasma samples varied by 2 to 3 log10 IU/mL. The commutability showed a similar disparity between the matrices. Recalibration using international standards diminished the resulting discrepancies in some but not all cases. Differences in the sample matrix can affect the commutability and interassay agreement of quantitative BKPyV assays. Differences in commutability between matrices may largely be due to factors other than those such as amplicon size, previously described as important in the case of cytomegalovirus. Continued efforts to standardize viral load measurements must address multiple sources of variability and account for differences in assay systems, quantitative standards, and sample matrices.

Hepatitis due to human herpesvirus 6B after hematopoietic cell transplantation and a review of the literature

Human herpesvirus 6B (HHV-6B) is an opportunistic pathogen associated with a growing number of complications in immunocompromised patients. Multiple reports of HHV-6B-associated hepatitis following primary HHV-6 infection and liver transplantation have appeared, but this has only been well documented in 1 patient after hematopoietic cell transplantation (HCT). This report describes a case of acute hepatitis likely caused by HHV-6B in an HCT recipient who was successfully treated with ganciclovir. HHV-6B DNA was demonstrated in plasma and hepatic tissue using quantitative polymerase chain reaction and immunohistochemical stains. Chromosomal integration was ruled out. We review the literature reporting HHV-6B-associated hepatitis, which may be an underappreciated cause of liver disease after HCT.

Combinatorial anti-HIV gene therapy: using a multipronged approach to reach beyond HAART

The 'Berlin Patient', who maintains suppressed levels of HIV viremia in the absence of antiretroviral therapy, continues to be a standard bearer in HIV eradication research. However, the unique circumstances surrounding his functional cure are not applicable to most HIV(+) patients. To achieve a functional or sterilizing cure in a greater number of infected individuals worldwide, combinatorial treatments, targeting multiple stages of the viral life cycle, will be essential. Several anti-HIV gene therapy approaches have been explored recently, including disruption of the C-C chemokine receptor 5 (CCR5) and CXC chemokine receptor 4 (CXCR4) coreceptor loci in CD4(+) T cells and CD34(+) hematopoietic stem cells. However, less is known about the efficacy of these strategies in patients and more relevant HIV model systems such as non-human primates (NHPs). Combinatorial approaches, including genetic disruption of integrated provirus, functional enhancement of endogenous restriction factors and/or the use of pharmacological adjuvants, could amplify the anti-HIV effects of CCR5/CXCR4 gene disruption. Importantly, delivering gene disruption molecules to genetic sites of interest will likely require optimization on a cell type-by-cell type basis. In this review, we highlight the most promising gene therapy approaches to combat HIV infection, methods to deliver these therapies to hematopoietic cells and emphasize the need to target viral replication pre- and post-entry to mount a suitably robust defense against spreading infection.

Measurement of CTL-induced cytotoxicity: the caspase 3 assay

Cytotoxic T lymphocytes (CTL) are critical effector cells of the immune system. Measurement of target cell damage has historically been an important measure of CTL function. CTL kill their target cells predominantly by inducing programmed cell death, or apoptosis. The gold standard for CTL-mediated cytotoxicity has been the (51)Cr release assay. However, measurement of target cell lysis by (51)Cr release does not provide mechanistic information on the fate of target cells, especially at the single cell level. Given the recent advances in our understanding of programmed cell death, newer assays are required which evaluate the status of the apoptotic pathways in target cells. We have developed a flow cytometry-based assay for CTL-mediated cytotoxicity based on specific binding of antibody to activated caspase 3 in target cells. Our assay is convenient and more sensitive than the (51)Cr release assay. The use of this assay should allow mechanistic studies of the intracellular events resulting from CTL attack.

Laboratory approaches to the diagnosis of hepatitis C virus infection

Hepatitis C virus (HCV) infection is a major and growing health problem worldwide. Laboratory testing plays an important role in the response to the HCV epidemic. Serologic tests for antibody to HCV are useful for screening purposes. The mainstays of laboratory testing for HCV, however, are the molecular approaches. Qualitative molecular tests are useful for confirmation of positive screening tests. Quantitative molecular tests provide prognostic information regarding the likelihood of response to therapy, and allow the monitoring of treatment efficacy. Similarly, genotyping assays predict response to therapy, and allow rational decisions regarding duration of treatment. The combination of continually improving laboratory testing, together with new drugs targeting distinct molecular determinants that are either essential or important in the viral replication cycle, is likely to lead to dramatic improvements in the management of HCV disease.

Ontogeny and specificities of mucosal and blood human immunodeficiency virus type 1-specific CD8(+) cytotoxic T lymphocytes

Induction of adaptive immunity to human immunodeficiency virus type 1 (HIV-1) at the mucosal site of transmission is poorly understood but crucial in devising strategies to control and prevent infection. To gain further understanding of HIV-1-specific T-cell mucosal immunity, we established HIV-1-specific CD8(+) cytotoxic T-lymphocyte (CTL) cell lines and clones from the blood, cervix, rectum, and semen of 12 HIV-1-infected individuals and compared their specificities, cytolytic function, and T-cell receptor (TCR) clonotypes. Blood and mucosal CD8(+) CTL had common HIV-1 epitope specificities and major histocompatibility complex restriction patterns. Moreover, both systemic and mucosal CTL lysed targets with similar efficiency, primarily through the perforin-dependent pathway in in vitro studies. Sequence analysis of the TCRbeta VDJ region revealed in some cases identical HIV-1-specific CTL clones in different compartments in the same HIV-1-infected individual. These results clearly establish that a subset of blood and mucosal HIV-1-specific CTL can have a common origin and can traffic between anatomically distinct compartments. Thus, these effectors can provide immune surveillance at the mucosa, where rapid responses are needed to contain HIV-1 infection.

Inhibition of apoptosis by primary isolates of herpes simplex virus

HSV-1 inhibits apoptosis of the infected cell, presumably to increase viral yield. Weaker anti-apoptotic activity was previously reported in laboratory-adapted HSV-2, but not in two low-passage clinical HSV-2 isolates, suggesting that the anti-apoptotic effect might result from adaptation to laboratory growth. We therefore assembled a large panel of clinical strains of HSV-1 and HSV-2. Clinical and laboratory strains of HSV-1 strongly inhibited apoptosis of Jurkat cells, as determined by morphologic change or caspase activation, while clinical HSV-2 strains showed no inhibitory activity in Jurkat cells. These findings suggest fundamental differences between HSV-1 and HSV-2 in their manipulation of host cell apoptosis.

HSV and glycoprotein J inhibit caspase activation and apoptosis induced by granzyme B or Fas

HSV-1 inhibits apoptosis of infected cells, presumably to ensure that the infected cell survives long enough to allow completion of viral replication. Because cytotoxic lymphocytes kill their targets via the induction of apoptosis, protection from apoptosis could constitute a mechanism of immune evasion for HSV. Several HSV genes are involved in the inhibition of apoptosis, including Us5, which encodes glycoprotein J (gJ). Viruses deleted for Us5 showed defects in inhibition of caspase activation after Fas ligation or UV irradiation. Transfected cells expressing the Us5 gene product gJ were protected from Fas- or UV-induced apoptosis, as measured by morphology, caspase activation, membrane permeability changes, or mitochondrial transmembrane potential. In contrast, caspase 3 activation in mitochondria-free cell lysates by granzyme (gr)B was inhibited equivalently by Us5 deletion and rescue viruses, suggesting that gJ is not required for HSV to inhibition this process. However, mitochondria-free lysates from transfected cells expressing Us5/gJ were protected from grB-induced caspase activation, suggesting that Us5/gJ is sufficient to inhibit this process. Transfected cells expressing Us5/gJ were also protected from death induced by incubation with purified grB and perforin. These findings suggest that HSV has a comprehensive set of immune evasion functions that antagonize both Fas ligand- and grB-mediated pathways of CTL-induced apoptosis. The understanding of HSV effects on killing by CTL effector mechanisms may shed light on the incomplete control of HSV infections by the immune system and may allow more rational approaches to the development of immune modulatory treatments for HSV infection.

Quantitation of BK virus load in serum for the diagnosis of BK virus-associated nephropathy in renal transplant recipients

BK virus-associated nephropathy is an increasingly recognized cause of graft dysfunction among kidney transplant recipients, and definitive diagnosis requires renal biopsy. By using a newly developed, quantitative, real-time polymerase chain reaction (PCR) assay for BK virus DNA, a retrospective analysis was done of sequential serum samples (n=28) from 4 transplant recipients with histopathologically documented BK virus nephropathy and from samples (n=76) from 16 transplant recipient control patients. BK virus DNA was detected in serum samples from all 4 case patients versus 0 of 16 control patients (P< .0001, Fisher's exact test) at a median of 32 weeks (range, 17-61 weeks) before the diagnosis of BK virus nephropathy. BK virus load decreased in 3 of 3 patients after the reduction of immunosuppression and/or nephrectomy. It is concluded that quantitative PCR for BK virus DNA in serum is useful both for identifying transplant recipients at risk for BK virus nephropathy and for monitoring the response to therapy.

Fatal parvovirus myocarditis in a 5-year-old girl

Infection with parvovirus B19 is common in children and typically causes mild illness. We report here the case of a 5-year-old girl who died suddenly, 2 weeks after the clinical diagnosis of a parvoviral infection (erythema infectiosum). Microscopic examination of the heart showed severe myocarditis with extensive T-cell and macrophage infiltration. Cultures, serology, and molecular analyses of serum for enteroviridae, adenovirus, influenza, varicella zoster, cytomegalovirus, and herpes simplex viruses were negative. Quantitative polymerase chain reaction (PCR) analysis for parvovirus B19 in peripheral blood, however, showed active infection (91,000 genomes/mL serum; 2.4 genomes/mononuclear cell). Despite the presence of myocarditis, immunostaining for parvoviral surface antigens was negative in the heart. Quantitative PCR analysis of paraffin sections showed that myocardial parvoviral content was significantly less than that of the normal appearing kidney and within the range predicted simply by tissue blood content. Thus, parvovirus B19 infection can be complicated by fatal myocarditis. Because the virus does not appear to have infected the heart, per se, we speculate that myocarditis arose from immunological cross-reaction to epitopes shared between the virus and the myocardium. HUM PATHOL 32:342-345.

High-throughput quantitative analysis of hepatitis B virus DNA in serum using the TaqMan fluorogenic detection system

Reproducible quantitative assays to detect viral nucleic acids have proven useful in defining disease progression and following response to therapy in a wide variety of viral infections. We describe the development of a quantitative assay to detect hepatitis B virus (HBV) DNA using real-time fluorescent-probe polymerase chain reaction (PCR) (TaqMan). The assay is highly reproducible, highly automated, and much more sensitive than the currently used branched-chain DNA (bDNA) assay for HBV. The quantitative PCR assay accurately detected samples ranging from 10 to 10(9) copies of HBV DNA per milliliter. Of 157 serum samples submitted for HBV quantitation, 119 were positive by TaqMan PCR versus only 55 by bDNA (P <.001). All 55 bDNA-positives were positive by TaqMan. Of the 77 samples with detectable HBV-DNA titers below 3.75 x 10(5) copies by TaqMan, only 13 were detected by bDNA. We tested 119 patients negative for all HBV serologic markers, and all tested negative in the TaqMan assay. HBV DNA was detected by TaqMan in 164 of 195 (84%) of hepatitis B surface antigen (HBsAg)-positive samples. Among hepatitis B e antigen (HBeAg)-positive samples, median titers were 4. 3 x 10(6) copies/mL versus 322 copies/mL in HBeAg-negative samples (P =.012). The TaqMan assay for HBV DNA is highly sensitive and reproducible and thus appears useful in accurately defining levels of viral replication among persons with HBV infection.

The tunel assay in the diagnosis of graft-versus-host disease: caveats for interpretation

Acute graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality following bone marrow transplantation, and early detection is important to allow effective therapy. Since the presence of apoptotic keratinocytes (dyskeratotic bodies) has been suggested as a useful diagnostic criterion for GVHD, attention has focused on the use of the TUNEL assay to detect apoptosis in clinical specimens. We reviewed clinical specimens upon which TUNEL had been performed for possible artifacts that might interfere with accurate evaluation for GVHD. Several distinct types of artifact were found and could be re-created in experimental systems. Artifacts in TUNEL staining generally resulted from the lack of specificity of this reaction for apoptotic cell death. Artifacts were found resulting from inadequate fixation, over-exposure of the TUNEL reaction, and proximity to the section edge. In addition, a novel artifact, apparently resulting from DNA shearing during the sectioning process, was noted and confirmed using confocal microscopy of experimental specimens. The TUNEL assay must therefore must be interpreted with caution in the clinical setting. In our laboratory, we consider TUNEL-positive cells as apoptotic only when accompanied by apoptotic morphology. Although these criteria clearly miss some cells in the early stages of apoptosis, they provide the highest specificity for apoptotic cell death.

Herpes simplex virus inhibits apoptosis through the action of two genes, Us5 and Us3

Apoptosis of virus-infected cells occurs either as a direct response to viral infection or upon recognition of infection by the host immune response. Apoptosis reduces production of new virus from these cells, and therefore viruses have evolved inhibitory mechanisms. We previously showed that laboratory strains of herpes simplex virus type 1 (HSV-1) protect infected cells from apoptosis induced by cytotoxic T lymphocytes or ethanol. We have now evaluated the ability of HSV-1 and HSV-2 laboratory and clinical isolates to inhibit apoptosis induced by anti-Fas antibody or UV irradiation and explored the genetic basis for this inhibition. HSV-1 isolates inhibited apoptosis induced by UV or anti-Fas antibody. In contrast, HSV-2 clinical isolates failed to inhibit apoptosis induced by either stimulus, although the HSV-2 laboratory strain 333 had a partial inhibitory effect on UV-induced apoptosis. Inhibition of apoptosis by HSV was accompanied by marked reduction of caspase-3 and caspase-8 activity. Deletion of the HSV-1 Us3 gene markedly reduced inhibition of UV-induced apoptosis and partially abrogated inhibition of Fas-mediated apoptosis. Conversely, deletion of the HSV-1 Us5 gene markedly reduced protection from Fas-mediated apoptosis and partially abrogated protection from UV. The Us11 and Us12 genes were not necessary for protection from apoptosis induced by either stimulus. The differences between HSV-1 and HSV-2 in the ability to inhibit apoptosis may be factors in the immunobiology of HSV infections.

Keratinocyte apoptosis following bone marrow transplantation: evidence for CTL-dependent and -independent pathways

Acute graft-versus-host disease (GVHD) is a complication of bone marrow transplantation (BMT). The histopathologic features used to diagnose GVHD are nonspecific, and may be secondary to chemotherapy or irradiation given before BMT. The presence of apoptotic keratinocytes or activated CTL may distinguish GVHD from conditioning effects. This study investigated the relationship in BMT recipients between keratinocyte apoptosis and the effects of conditioning regimens or immune-mediated GVHD. Inflammatory cells, apoptotic keratinocytes, and CTL expressing TIA-1 (a molecule associated with the lytic granules of CTL) were quantitated in allogeneic and autologous recipients. Allogeneic recipients could exhibit keratinocyte apoptosis secondary to a combination of conditioning effects and immune-mediated GVHD. In contrast, autologous recipients should show conditioning effects only. 'Capped' TIA-1-positive lymphocytes and apoptotic keratinocytes were much more frequent in the allogeneic group than the autologous group (16.1% of total TIA-1 positive lymphocytes vs 4.5%, P=0.02; and 37.6/mm2 vs 3.9/mm2, P = 0.005, respectively), although there was some overlap in their frequency. Among individual recipients of allogeneic BMT, the number of epidermal lymphocytes or macrophages correlated with the number of apoptotic keratinocytes. A similar, but weaker, correlation was seen between the number of 'capped' TIA-1-positive lymphocytes and apoptotic keratinocytes. No such relationship was seen in autologous recipients. In allogeneic recipients, TIA-1 expressing CTL were seen in intimate contact with apoptotic keratinocytes, some of which also had detectable cytoplasmic TIA-1. No CTL/keratinocyte interactions were identified in autologous recipients. Our results suggest that apoptotic keratinocytes arise in the skin of BMT patients due to both GVHD and conditioning effects, and that the keratinocyte damage in GVHD is mediated by both CTL-dependent and -independent mechanisms. Increased numbers of apoptotic keratinocytes, in the presence of increased epidermal lymphocytes or 'capped' TIA-l-expressing lymphocytes, support a diagnosis of GVHD, but must be interpreted in the context of clinical information and other histopathologic findings.

Herpes simplex virus type 1 renders infected cells resistant to cytotoxic T-lymphocyte-induced apoptosis

Many viruses interfere with apoptosis of infected cells, presumably preventing cellular apoptosis as a direct response to viral infection. Since cytotoxic T lymphocytes (CTL) induce apoptosis of infected cells as part of the "lethal hit," inhibition of apoptosis could represent an effective immune evasion strategy. We report here herpes simplex virus type 1 (HSV-1) interference with CTL-induced apoptosis of infected cells and show that HSV-1 inhibits the nuclear manifestations of apoptosis but not the membrane changes. The HL-60 cell line (human promyelocytic leukemia) undergoes apoptosis in response to many stimuli, including incubation with ethanol. After HSV-1 infection (strains E115 and 17+), ethanol-treated cells did not produce oligonucleosomal DNA fragments characteristic of apoptosis, as assayed by gel electrophoresis and enzyme-linked immunosorbent assay. Inhibition was detected 2 h after infection and increased over time. Importantly, HSV-1-infected cells were resistant to apoptosis induced by antigen-specific CD4+ CTL, despite the fact that CTL recognition and degranulation in response to infected targets remained intact. Unlike HSV-1, HSV-2 (strains 333 and HG52) did not inhibit DNA fragmentation. In contrast to the inhibition of DNA fragmentation by HSV-1, none of the HSV-1 or -2 strains interfered with the ethanol-induced exposure of surface phosphatidylserine characteristic of apoptosis, as determined by annexin V binding. These results demonstrate that genes of HSV-1 inhibit the nuclear manifestations of apoptosis but not the membrane manifestations, suggesting that these may be mediated via separate pathways. They also suggest that HSV-1 inhibition of CTL-induced apoptosis may be an important mechanism of immune evasion.

A survivor of breast cancer with immunity to MUC-1 mucin, and lactational mastitis

The human mucin, MUC-1, is a transmembrane glycoprotein that is produced by both normal an malignant epithelium. The MUC-1 produced by malignant epithelium is underglycosylated, which leads to the expression by tumors of novel T and B cell epitopes on the mucin polypeptide core. Similar underglycosylation occurs in the lactating breast. In this report, we describe a long-term survivor of breast cancer whose tumor strongly expressed the T- and B-cell-stimulatory epitopes. Five years after presenting with the tumor, the patient had her first pregnancy, at which time she developed fulminant lymphocytic mastitis. We demonstrate that the lactating breast produced mucin expressing the same "tumor-specific" epitopes as the original cancer. The patient had circulating anti-mucin antibodies of both the IgM and IgG isotypes (these are not found in normal controls), and mucin-specific cytotoxic T lymphocytes in the peripheral blood. Limiting-dilution analysis for mucin-specific cytotoxic T lymphocytes in three different experiments yielded frequencies of 1 in 3086, 1 in 673, and 1 in 583, compared to approximately 1 in 10(6) in normal controls. The patient remains clinically free of carcinoma after 5 additional years of follow-up. We propose that the original tumor primed the patient's immune response against the mucin epitopes, and that the re-expression of these epitopes on the lactating breast evoked a secondary immune response. It is tempting to speculate that the vigor of her anti-mucin immunity may have helped protect this patient against recurrent tumor.

MUC-1 epithelial tumor mucin-based immunity and cancer vaccines

Many obstacles still stand in the way to eliciting an effective immune response against cancer, even though several antigens and antigenic peptides have been identified as potential tumor targets. All of them, including the MUC-1 mucin, share the caveat of being normal cellular proteins. Unlike all the others, however, MUC-1 expressed on tumors can still be considered a truly tumor-specific antigen. Its expression on normal cells is hidden from the immune system, and its aberrant glycosylation on tumors creates new epitopes recognized by the immune system. Moreover, all other tumor targets identified so far are MHC-restricted peptides that can only be recognized by patients who carry a specific HLA type, or on tumors which continue to express particular HLA alleles. MUC-1 is powerfully different. Recognized as a native molecule independent of MHC, it is a universal immunogen and a universal target, and if made effectively immunogenic, it would be expected to elicit immune responses in all patients, and against numerous MUC-1 expressing human tumors. It may, in fact, be the extraordinary solution to an extraordinary problem of cancer immunity and immunotherapy.

Cytotoxic T cells from ovarian malignant tumors can recognize polymorphic epithelial mucin core peptides

CTL isolated from tumor infiltrating lymphocytes/tumor associated lymphocytes (TAL) infiltrating ovarian tumors have been demonstrated to mediate lysis of tumor targets after in vitro culture. These effector cells are of particular interest as cellular probes to detect and define human tumor Ag and epitopes that stimulate cellular immunity to human tumors. Polymorphic epithelial mucin (PEM) core peptides are potential candidates as tumor specific Ag because of their preferential expression on epithelial tumors. We report here that ovarian CTL-TAL can recognize mucin (Muc-1) core peptide of PEM. Several ovarian CTL-TAL lines were developed that recognized in a non-MHC restricted fashion an Muc-1+ ovarian tumor, but not Muc-1-tumor. To define the specificity of these CTL-TAL and exclude cross-reactivity with other potential Ag, cytotoxicity experiments were performed using as targets EBV-transformed cell lines with an expression construct containing the Muc.1 cDNA. These ovarian CTL-TAL lysed mucin core-peptide transfected cells but not targets transfected with an expression construct containing a mucin frame-shift mutant cDNA as control. In addition, targets pulsed with short synthetic peptides composed of amino acids 1-14 of the Muc 1 core peptide repeat were also lysed by the same CTL-TAL. This lysis was inhibited by the mAb SM3 that recognize an epitope on the mucin core peptide. These results, which are a demonstration of a specific Ag recognized by ovarian CTL-TAL, may be of interest for specific immunotherapy of ovarian cancer.

Cytotoxic T cells from ovarian malignant tumors can recognize polymorphic epithelial mucin core peptides

CTL isolated from tumor infiltrating lymphocytes/tumor associated lymphocytes (TAL) infiltrating ovarian tumors have been demonstrated to mediate lysis of tumor targets after in vitro culture. These effector cells are of particular interest as cellular probes to detect and define human tumor Ag and epitopes that stimulate cellular immunity to human tumors. Polymorphic epithelial mucin (PEM) core peptides are potential candidates as tumor specific Ag because of their preferential expression on epithelial tumors. We report here that ovarian CTL-TAL can recognize mucin (Muc-1) core peptide of PEM. Several ovarian CTL-TAL lines were developed that recognized in a non-MHC restricted fashion an Muc-1+ ovarian tumor, but not Muc-1-tumor. To define the specificity of these CTL-TAL and exclude cross-reactivity with other potential Ag, cytotoxicity experiments were performed using as targets EBV-transformed cell lines with an expression construct containing the Muc.1 cDNA. These ovarian CTL-TAL lysed mucin core-peptide transfected cells but not targets transfected with an expression construct containing a mucin frame-shift mutant cDNA as control. In addition, targets pulsed with short synthetic peptides composed of amino acids 1-14 of the Muc 1 core peptide repeat were also lysed by the same CTL-TAL. This lysis was inhibited by the mAb SM3 that recognize an epitope on the mucin core peptide. These results, which are a demonstration of a specific Ag recognized by ovarian CTL-TAL, may be of interest for specific immunotherapy of ovarian cancer.

Tumor-specific cytotoxic T cell clones from patients with breast and pancreatic adenocarcinoma recognize EBV-immortalized B cells transfected with polymorphic epithelial mucin complementary DNA

Human breast and pancreatic adenocarcinomas are tumors of ductal epithelial cell origin and as such produce and express on their surface polymorphic epithelial cell mucin encoded by the MUC 1 gene. We have previously reported that tumor-specific cytotoxic T cells derived from patients bearing such tumors recognize specific epitopes on the mucin polypeptide core. This recognition was not MHC-restricted because of the highly repetitive sequence of the polypeptide core, which allows simultaneous recognition of many identical epitopes, and cross-linking and aggregation of TCR on mucin-specific T cells. Those studies were performed with limited numbers of tumor cells or allogeneic tumor cell lines. A renewable source of autologous cells presenting this Ag was necessary to further explore mucin-specific immunity. We report here successful establishment and functional analysis of mucin-specific CTL lines and clones derived from breast and pancreatic cancer patients, using either autologous or allogeneic mucin-transfected B cells as Ag. Our results demonstrate that transfection of autologous or allogeneic B cells with mucin confers upon them tumor Ag-presenting ability as well as susceptibility to lysis by mucin-specific CTL. Transfection of APC with this or any other human tumor Ag that may be molecularly defined in the future provides a unique and powerful tool with which to examine the ability of a tumor-associated Ag to stimulate T cell responses.

Tumor-specific cytotoxic T cell clones from patients with breast and pancreatic adenocarcinoma recognize EBV-immortalized B cells transfected with polymorphic epithelial mucin complementary DNA

Human breast and pancreatic adenocarcinomas are tumors of ductal epithelial cell origin and as such produce and express on their surface polymorphic epithelial cell mucin encoded by the MUC 1 gene. We have previously reported that tumor-specific cytotoxic T cells derived from patients bearing such tumors recognize specific epitopes on the mucin polypeptide core. This recognition was not MHC-restricted because of the highly repetitive sequence of the polypeptide core, which allows simultaneous recognition of many identical epitopes, and cross-linking and aggregation of TCR on mucin-specific T cells. Those studies were performed with limited numbers of tumor cells or allogeneic tumor cell lines. A renewable source of autologous cells presenting this Ag was necessary to further explore mucin-specific immunity. We report here successful establishment and functional analysis of mucin-specific CTL lines and clones derived from breast and pancreatic cancer patients, using either autologous or allogeneic mucin-transfected B cells as Ag. Our results demonstrate that transfection of autologous or allogeneic B cells with mucin confers upon them tumor Ag-presenting ability as well as susceptibility to lysis by mucin-specific CTL. Transfection of APC with this or any other human tumor Ag that may be molecularly defined in the future provides a unique and powerful tool with which to examine the ability of a tumor-associated Ag to stimulate T cell responses.

Expression of tumor-associated epitopes on Epstein-Barr virus-immortalized B-cells and Burkitt's lymphomas transfected with epithelial mucin complementary DNA

Mucins are among the best described human tumor-associated antigens. At least 73 tumor-reactive anti-mucin antibodies have been described; in addition, we have previously demonstrated the existence of tumor-specific cytotoxic T-lymphocyte epitopes on the mucin produced by breast and pancreatic tumors. To determine whether the appearance of tumor-associated mucin epitopes can be explained by altered post-translational modification of mucin in tumors, or whether the generation of these epitopes requires changes in the mucin gene itself, we studied four Burkitt's lymphomas and six Epstein-Barr virus-immortalized B-cell lines transfected with an expression construct containing the mucin complementary DNA. Transfected cell lines showed stable maintenance of the mucin gene, which comprises 20 or more tandem repeats of a 60-nucleotide sequence. Transfected cells expressed many tumor-associated mucin epitopes, suggesting that the changes in mucin synthesis seen in breast and pancreatic tumors are present in other malignant cell types as well. Furthermore, even though each cell line was transfected with the identical mucin construct, each expressed a different subset of tumor-associated mucin epitopes. This suggests that the specificity of these epitopes for tumors is not due to genetic alterations of the mucin gene in tumors. Incubating transfected cells with phenyl-N-acetyl-alpha-galactosaminide, an inhibitor of O-linked glycosylation, altered cell surface carbohydrate structures and resulted in increased expression of all tumor-associated epitopes, implicating incomplete glycosylation of mucin in the generation of these epitopes. These findings suggest that alterations in the posttranslational modification of normal gene products can result in the expression of novel epitopes. Furthermore, the ability to transfect cancer patients' Epstein-Barr virus-immortalized B-cell lines with mucin will provide an unlimited supply of autologous, mucin-bearing cells with which to study these patients' T-cell response to mucin.

Cytotoxic T-lymphocytes derived from patients with breast adenocarcinoma recognize an epitope present on the protein core of a mucin molecule preferentially expressed by malignant cells

A population of tumor-reactive cytotoxic T-cells can be propagated from tumor-draining lymph nodes of patients with breast adenocarcinoma. These T-cells specifically recognize breast and pancreatic tumor cells in a major histocompatibility complex (MHC)-unrestricted fashion but not other tumors of epithelial origin or the natural killer target K562. The tumor-specific but MHC-unrestricted lytic activity of these cytotoxic T-lymphocytes (CTLs) is mediated through the alpha/beta T-cell receptor. The molecule recognized by these CTLs is ductal epithelial mucin produced by breast and pancreatic adenocarcinomas. The protein core of the mucin consists of multiple tandem repeats of a 20-amino acid sequence. Antibody SM3, directed against a determinant on the mucin protein core preferentially expressed on malignant cells is able to significantly inhibit lysis of tumor cells by the CTL, while other antibodies binding to different core epitopes are not. Normal breast epithelial lines, which also express mucin but not the SM3 epitope, are not lysed by these tumor-reactive CTLs or act as cold target inhibitors of lysis of tumor lines. The data suggest that the highly repetitive nature of the mucin allows cross-linking of the T-cell receptor on mucin-specific T-cells and therefore accounts for the lack of MHC restriction seen in this system. They further suggest that the mucin core epitope recognized on tumor cells is not expressed on normal epithelial cells in a manner that can be recognized by tumor-reactive CTLs. These findings support the role of mucins as important tumor-associated antigens mediating the cellular response to certain human cancers and suggest that epithelial mucin core sequences might form the basis for an effective vaccine to augment the antitumor immune response.