Vaccination of renal cell cancer (RCC) patients with modified vaccinia Ankara (MVA) delivering tumor antigen 5T4 administered alone or with interleukin 2 (IL-2) or interferon-alpha (IFN)

3026

Background: The attenuated vaccinia virus (MVA) has been engineered to deliver the tumor antigen 5T4 (TroVax). More than 90% of RCCs overexpress the 5T4 antigen. A series of clinical trials were conducted to evaluate the effectiveness of MVA 5T4 as a single agent or in combination with either IL-2 or IFN. Methods: Eligibility: Pathologic diagnosis of clear cell or papillary RCC, progressive measurable metastases, any prior therapy, adequate physiological parameters, Karnofsky performance status ≥ 80%, and no active CNS involvement. A regimen of MVA 5T4 alone or in combination with IL-2 or IFN was given. Results: A total of 53 pts received MVA 5T4 alone or in combination with IL-2 or IFN. 13 pts received MVA 5T4 alone, 25 pts received low dose subcutaneous IL-2, and 15 pts received IFN. Clinical responses were assessed by measuring changes in tumor burden via computed tomography or magnetic resonance imaging scan. 5T4-specific cellular and humoral responses were monitored throughout the study. 5T4 was well tolerated with no serious adverse events attributed to vaccination. Of 48 intention-to-treat pts, 43 mounted 5T4-specific antibody responses. 2 pts showed a complete response for > 36 months and 2 other pts had a partial response for > 24 months and 12 months respectively. 20 pts demonstrated disease stabilization for ≥ 3 months. Median progression-free survival and overall survival for all pts was 3.6 months (range 0.8–29.7) and 13.2 months (range 1–38) respectively. A significant relationship was detected between the magnitude of 5T4-specific antibody response and overall survival. Conclusions: 5T4, whether administered alone or in combination, was well tolerated. High frequency of 5T4-specific immune responses and associated enhanced patient survival is encouraging and warrants further investigation.

[Table: see text]

Analysis of immunological and clinical data resulting from four phase I and II trials of MVA-5T4 in colorectal cancer patients

3058

Background: The attenuated vaccinia virus MVA has been engineered to deliver the tumor antigen 5T4 (MVA-5T4; TroVax). 5T4 is a surface glycoprotein expressed by most solid tumors. MVA-5T4 has been tested in one phase I/II and three phase II clinical trials in colorectal cancer patients. All trials demonstrated that MVA-5T4 was well tolerated when administered alone (1 trial), as adjuvant/neoadjuvant to surgery (1 trial), or in combination with chemotherapy (FOLFOX or FOLFIRI; 2 trials). We have now collated data from all four trials, determined the incidence of immune responses across trials, and looked for associations with improved survival. Methods: Patients with histologically proven CRC were recruited to 4 independent trials in which 3 to 6 vaccinations of MVA-5T4 were scheduled to be administered either as a monotherapy, as adjuvant/neoadjuvant to surgery for respectable liver metastases or alongside treatment with FOLFIRI or FOLFOX. Antibody responses specific for 5T4 and MVA were monitored by ELISA. Survival data were collated from each hospital site. Immunological and survival data were analyzed using proportional hazards regression adjusting for age and gender. Results: Survival and immunological response data were available for 73 patients (median age 63), who received a median of 5 MVA-5T4 vaccinations (range 1–6). Of 69 patients tested for antibody responses post-vaccination (4 patients had no post-vaccination blood sample available), 54 (78%) and 65 (94%) showed positive responses for 5T4 and MVA respectively. Exploratory analyses demonstrated significant associations between immune responses and overall survival across trials. Indeed, a Cox proportional hazards model showed that a doubling in the geometric mean 5T4 antibody titre (injections 1 to 3) was associated with a 19.9% reduction in relative risk, adjusted for age and gender (p<1%). Conclusions: MVA-5T4 induced 5T4-specific immune responses in the majority of patients. Although the studies described here were uncontrolled, there were encouraging signs of activity which associated with the presence of 5T4-specific immune responses.

[Table: see text]

The oncofetal protein, 5T4, is a suitable target for antibody-guided anti-cancer chemotherapy with calicheamicin

The oncofetal protein, 5T4, is a tumor-associated protein displayed on the cell membrane of various carcinomas. This molecule is a promising target for anti-tumor vaccine development and for targeted therapy with staphylococcus exotoxin. The potential use of 5T4 as a target for antibody-guided chemotherapy has not been demonstrated. We report oncolytic efficacy and selectivity in vitro and in vivo with immuno-conjugates of calicheamicin (CM) and the anti-5T4 antibody, H8. CM is a potent cytotoxic drug that causes double strand breaks in DNA. Conjugates of CM and H8 were constructed with acid-labile as well as acid-stabile linkers. In vitro, when applied to monolayers of 5T4(+) cells, CM-conjugates targeting 5T4 were consistently more toxic than either free drug or a non-binding control CM-conjugate. This difference was less pronounced on 5T4-deficient cells. In vivo, four 5T4-positive subcutaneous tumor models were treated with conjugates. Efficacy was demonstrated by reduction of tumor growth relative to controls treated with drug vehicle. To evidence selectivity, the efficacy of the anti-5T4 conjugates was compared to the efficacy of H8, a mixture of H8 and calicheamicin, calicheamicin alone or calicheamicin conjugated to the anti-CD33 antibody, hP67.6. In addition, the efficacy and selectivity of an acid-labile conjugate of H8 was evaluated in an orthotopic model for 5T4(+) lung cancer. Increased survival following treatment was used as a parameter of efficacy. Calicheamicin conjugates of H8 were effective and selective in all the examined tumor models. Differences in efficacy between the acid-labile and acid-stabile conjugates depended on the investigated tumor model.

Activity of MVA 5T4 alone or in combination with either interleukin-2 (IL-2) or interferon-α (IFN) in patients (Pts) with metastatic renal cell cancer (MRCC)

3069

Background: MVA 5T4 consists of the highly attenuated modified Vaccinia Ankara virus containing the gene encoding the human TAA 5T4. Ninety percent or more of RCCs overexpress the 5T4 antigen. A series of clinical trials were conducted to evaluate the effectiveness of MVA 5T4 as a single agent or in combination with Interleukin-2 or Interferon Alpha 2B. Methods: Eligibility: pathologic diagnosis of clear cell or papillary RCC, progressive measurable metastases, any prior therapy, adequate physiologic parameters, Karnofsky performance status (KPS) = 80%, and no active CNS involvement. A regimen of MVA 5T4 alone or in combination with IFN or IL-2 was given. Results: A total of 41 patients received MVA 5T4 alone or in combination. 33 patients received MVA 5T4 with low dose IL-2 or IFN. 23 pts had clear cell; 12 papillary; 5 mixed clear cell; and 1 mixed papillary. 19 pts continue to receive therapy. 2 pts (both clear cell RCC) developed complete responses, 3 pts/partial responses (2 clear cell, 1 papillary) 8 pts/stable for 3+months and 6 pts are too early to be staged at this time. Median duration of therapy is 3.0+ (1+-13+) months. Conclusion: Although comparable antibody response were observed in papillary and clear cell histotypes, clear cell patients appeared to be more likely to respond in terms of clinical benefit parameters, to be presented. Of note is that preliminary analysis of clear cell patients suggests a relationship between the anti-5T4 immune response and tumor response. With the immunological potency and encouraging clinical activity, the future research will focus on the phase 3 randomized, double-blind, placebo controlled parallel group study to investigate whether MVA 5T4, added to first line standard of care therapy, prolongs the survival of patients with locally advanced or metastatic clear cell as well as studies to further optimize MVA 5T4 potency.

[Table: see text]

Open label phase II studies of modified vaccinia ankara expressing the tumor antigen 5T4 given in conjunction with IFL and FOLFOX chemotherapy regimens: Final analysis of safety and immunogenicity of MVA 5T4 given before, during and after chemotherapy

2527

Background: 5T4 is a tumour associated antigen that is widely expressed on the surface of most human adenocarcinomas, including colorectal, but rarely in normal cells. Modified Vaccinia Ankara (MVA) has been employed as a vaccine vector to deliver 5T4. Previously, MVA-5T4 has been evaluated in a phase I/II clinical trial in stage IV colorectal cancer patients. MVA-5T4 was shown to be safe and well tolerated and induced 5T4 specific immune responses in most patients. Furthermore, 5T4 specific antibody titres correlated with clinical benefit. Methods: Two open label phase II clinical trials were initiated in which patients with advanced colorectal cancer received MVA-5T4 in conjunction with either 5-FU/leukovorin and irinotecan (TV2-IFL; n=19 patients) or 5-FU/leukovorin and oxaliplatin (TV2-FOLFOX; n=17 patients). MVA-5T4 was administered up to 6 times, 2 prior to, 2 during and 2 post-chemotherapy. The primary objectives were to assess the safety and immunogenicity of MVA-5T4 given in combination with chemotherapy. Results: Recruitment to both trials is complete and MVA-5T4 was well tolerated in all ITT patients, with no serious adverse events being associated with MVA-5T4. 5T4-specific cellular and humoral immune responses were monitored before, during and after chemotherapy in all 23 per protocol patients (n=12 for TV2-IFL and n=11 for TV2-FOLFOX). Following vaccination, all 23 patients mounted 5T4 cellular and/or humoral responses. Immune responses were detectable during chemotherapy in the majority of patients. IFNγ ELISPOT responses to 5T4 peptides revealed precursor frequencies as high as 1 in 1000 PBMCs. Assessment of clinical responses in all PP patients demonstrated an overall response rate of 65% across both trials. Conclusions: MVA-5T4 is safe and well tolerated when administered in conjunction with IFL and FOLFOX chemotherapy regimens. Furthermore, 5T4 specific immune responses are induced in all per protocol patients and can be boosted or maintained during chemotherapy. Encouraging clinical responses have been observed and 5T4 immune responses shown to correlate with clinical benefit.

[Table: see text]

A vaccinia-based vaccine (TroVax) targeting the oncofetal antigen 5T4 administered before and after surgical resection of colorectal cancer liver metastases: Phase II trial

2574

Background: Oncofetal antigen 5T4 is expressed by most colorectal cancers. Administration of a vaccine combining a Modified Vaccinia Ankara (MVA) vector with 5T4 elicits immune responses in late-stage colorectal cancer patients. This trial seeks to investigate the immunological effects of the vaccine both in peripheral blood and locally in tumour tissue resected during potentially curative surgery for colorectal liver metastases. Some patients may have micrometastatic disease, a potential target for immunotherapy. Methods: Colorectal cancer patients selected for resection of liver metastases were eligible. Recruitment of up to 20 patients was planned. Following screening they received 2 vaccinations prior to, and 2 after, surgery. Primary endpoint was assessment of the immune response at time of surgery. Blood was taken for analysis at screening and 2 weeks after each vaccination. A tumour biopsy was obtained at surgery. T-cell responses were assessed using proliferation and gamma-interferon ELISPOT assays; ELISA used to assess serological response. Immunohistochemical analysis was used to confirm tumour antigen expression and the nature of T-cell infiltration into the liver. If 5T4-specific immune responses were demonstrated patients were offered further vaccinations at 20 and 28 weeks post surgery. Results: Of 20 patients recruited, 16 were eligible for assessment, 4 excluded, 1 due to hepatocellular carcinoma, 3 with inoperable disease. There was no grade III/IV toxicity related to vaccination. Tumour expression of 5T4 was confirmed in all cases, local T-cell infiltration consisted predominantly of CD4 cells. According to proliferation assays, 8 of 16 patients had T-cell responses at time of surgery and 12 of 16 in total to date. 14 patients have developed 5T4-specific antibody responses. At median follow up of 8.4 months 7 of 16 patients have disease recurrence. Conclusions: The MVA-5T4 vaccine (TroVax) was safe and well tolerated in all patients undergoing resection of colorectal liver metastases. 5T4 specific cellular and/or humoral immune responses were induced in the majority of patients following vaccination with TroVax.

[Table: see text]

A phase I clinical trial of MVA expressing 5T4 and high-dose interleukin-2 (IL-2) for metastatic renal cell carcinoma

12500

Background: Metastatic renal cell carcinoma (RCC) is an immune responsive tumor. 5T4 is a tumor antigen expressed on the cell surface of clear cell and papillary RCC. We sought to evaluate the safety and immunologic effects of vaccination with modified vaccinia virus Ankara (MVA) expressing 5T4 followed by IL-2 in patients with advanced RCC. Methods: A single dose Phase I clinical trial was conducted in patients with metastatic RCC and who were eligible for high-dose IL-2. Vaccination was given every three weeks by intramuscular injection and was followed immediately by standard high-dose bolus IL-2 (600,000 IU/kg) after the second and third vaccinations. The regimen could be repeated if there was no evidence of disease progression. Peripheral blood and serum was collected before treatment and every three weeks for analysis. Routine blood counts, chemistry, and pituitary functions were monitored. Anti-5T4 antibody titers were determined by ELISA assay and 5T4-specific T cell responses were monitored by interferon-γ ELISPOT assay using overlapping peptides. Results: 25 patients with RCC are being sequentially enrolled. There have been no serious vaccine-related adverse events although typical Grade 3 IL-2 related toxicity has been seen in all patients. To date, all patients tested have developed an increase in 5T4-specific antibody titers following three initial vaccinations. T cell assays are currently in progress. Seven patients have completed the trial through at least one course of treatment (mean age 62.3 years). Of these 7, one patient who presented with a primary tumor in place and synchronous metastatic disease had an objective complete response of all metastatic disease and underwent a post-treatment nephrectomy; the primary tumor demonstrated highly necrotic tumor. Two additional patients have had stable disease and are receiving booster vaccinations every three months. Conclusions: These results demonstrate that local vaccination with an MVA virus expressing 5T4 administered in combination with high-dose IL-2 is safe and induces 5T4-specific antibodies in all patients. Additional T cell responses and clinical follow-up will be presented. The use of MVA-5T4 and IL-2 appears to be a promising approach for the treatment of advanced RCC.

[Table: see text]

A phase II trial to assess the activity of MVA5T4 plus interleukin-2 in patients (Pts) with metastatic renal cell carcinoma (MRCC)

14642

Background: MVA 5T4 consists of a highly attenuated vaccinia virus (modified Vaccinia Ankara, MVA) containing the human tumor associated antigen (TAA) 5T4. Greater than 90% of renal cell cancers are overexpressed by the 5T4 antigen. The primary purpose of this trial is to validate the hypothesis that, in this group of pts, it is possible to induce immune responses either humoral and/or cellular to 5T4 and to break tolerance to the antigen. The immune response will be correlated to clinical outcome. Methods: Eligibility included: pathologic diagnosis of confirmed clear cell or papillary cancer, progressive measurable MRCC, adequate organ/marrow function, Karnofsky Performance Status (KPS) ≥ 80%, any prior therapy, and no active CNS involvement. The dosage schedule of subcutaneous low dose IL-2 will be an initial dose 250,000 U/kg/dose for 5 days in week 1 followed by 125,000 U/kg/dose for 5 days each of weeks 2–6 inclusive. There will then be a 2 week recovery period before the next cycle commences. The dosage regimen of MVA 5T4 will be intramuscular injections given 14 days prior to the first cycle, day 0 and 1 injection given at the beginning of week 4 of the first cycle. In subsequent cycles, booster injections of MVA 5T4 will be given at week 1 only, prior to the commencement of subcutaneous IL-2 therapy. Results: 10 pts have been treated with MVA 5T4 and the LD IL2 regimen. The combination has been extremely well tolerated with no MVA 5T4 related events thus far. Although the study is still continuing to accrue, there are early signs of clinical responses in a number of patients receiving the combination. The immunological analysis is in progress. Conclusion: MVA 5T4 is well tolerated in this group of patients. The immune response will be presented along with clinical outcome.

[Table: see text]

The schistosome egg: development and secretions

We have investigated the development of the schistosome egg and its secretions in order to understand how it migrates through gut tissues and also initiates pathology in the liver. We show by electron microscopy that the subshell envelope is absent in the newly deposited egg, but appears very early and differentiates as development progresses. In the mature egg, this nucleated envelope contains extensive endoplasmic reticulum, suggestive of a protein synthetic capacity. Furthermore, Reynolds' layer only appears between the envelope and the egg-shell in the mature egg and may represent its accumulated secretions. We have biosynthetically labelled and collected the secretions (ESP) released by mature but not immature eggs during culture. Their fractionation by SDS-PAGE reveals a simple pattern of 6 bands, differing markedly in composition from soluble egg antigen preparations. Electrophoresis in casein substrate gels demonstrates the presence of 2 distinct proteases in the egg secretions. By immunocytochemistry, ESP localized predominantly to the envelope of the mature egg, suggesting that this layer rather than the miracidium is the source of egg secretions.

Performance of the dynamic single photon emission computed tomography (dSPECT) method for decreasing or increasing activity changes

Radionuclide imaging is now widely used whenever functional information is required. We present a new approach to dynamic SPECT imaging (dSPECT method) that uses a single slow rotation of a conventional camera and allows us to reconstruct a series of 3D images corresponding to the radiotracer distribution in the body at various times. Using simulations of various camera configurations and acquisition protocols, we have shown that this method is able to reconstruct washout half-lives with an accuracy greater than 90% when used with triple-head SPECT cameras. Accuracy decreases when using fewer camera heads, but dual-head geometries still give an accuracy greater than 80% for short and 90% for long half-lives and about 50-75% for single-head systems. Dynamic phantom experiments have yielded similar results. Presence of attenuation and background activity does not affect the accuracy of the dSPECT reconstructions. In all situations investigated satisfactory dynamic images were produced. A preliminary normal volunteer study measuring renal function was performed. The reconstructed dynamic images may be presented as a three-dimensional movie showing movement of the tracer through the kidneys and the measurement of the regional renal function can be performed. The time-activity curves determined from this dSPECT data are very similar to those obtained from dynamic planar scans.

Characterization, cloning and immunogenicity of antigens released by transforming cercariae of Schistosoma mansoni

A schistosome infection is initiated when the parasite penetrates the skin of a susceptible host. Relatively large quantities of protein are released by transforming cercariae compared to later larval stages. This represents the first parasite material to which the host's immune system is exposed, yet little is known about the proteins which are released during the first few hours post-transformation. We have shown that antiserum raised against such molecules was capable of imparting protection against a schistosome challenge infection upon passive transfer to naïve mice. By screening a cercarial cDNA library with this serum, 38 positive clones were identified. Sequence analysis showed these to represent 8 different molecules which included Schistosoma mansoni 21-7 kDa antigen, calcium-binding-protein and the vaccine candidate glutathione S-transferase (Sm28GST). In addition, 5 clones were isolated, 1 of which had significant homology to many cytochrome C proteins, another with leukocyte elastase inhibitors and 3 which represented novel molecules. Four clones were expressed in a prokaryotic high-level expression vector, sera produced against each purified recombinant protein and used subsequently to probe Western blots and parasite sections. The leukocyte elastase inhibitor homologue and 2 unknowns induced significant proliferation by lymph node cells recovered from mice vaccinated with irradiated cercariae. More strikingly, the 2 novel proteins stimulated very high levels of interferon gamma (IFNgamma) secretion both by lymph node cells and those recovered by broncho-alveolar lavage from the lungs of vaccinated mice. Such results will be discussed in the context of vaccine development.

Functional characterization of intracellular and secreted forms of a truncated hepatitis C virus E2 glycoprotein

The E2 protein of hepatitis C virus (HCV) is believed to be a virion surface glycoprotein that is a candidate for inclusion in an antiviral vaccine. A truncated soluble version of E2 has recently been shown to interact with CD81, suggesting that this protein may be a component of the receptor for HCV. When expressed in eukaryotic cells, a significant proportion of E2 forms misfolded aggregates. To analyze the specificity of interaction between E2 and CD81, the aggregated and monomeric forms of a truncated E2 glycoprotein (E2(661)) were separated by high-pressure liquid chromatography and analyzed for CD81 binding. Nonaggregated forms of E2 preferentially bound CD81 and a number of conformation-dependent monoclonal antibodies (MAbs). Furthermore, intracellular forms of E2(661) were found to bind CD81 with greater affinity than the extracellular forms. Intracellular and secreted forms of E2(661) were also found to differ in reactivity with MAbs and human sera, consistent with differences in antigenicity. Together, these data indicate that proper folding of E2 is important for its interaction with CD81 and that modifications of glycans can modulate this interaction. Identification of the biologically active forms of E2 will assist in the future design of vaccines to protect against HCV infection.

Characterization, cloning and immunogenicity of antigens released by lung-stage larvae of Schistosoma mansoni

Lung-stage schistosomula are the target of protective immunity in mice vaccinated with attenuated cercariae of Schistosoma mansoni. Therefore, proteins present at this developmental stage, and in particular those which are secreted, are a potential source of novel vaccine candidates. However, little information is available about such molecules. Here we describe the cDNA clones identified by screening expression libraries with serum raised against proteins released by lung-stage schistosomula. In total, 11 different cDNA species were identified, 6 of which have been described previously in S. mansoni; these included fructose 1,6-bisphosphate aldolase and Sm21.7 which together accounted for two-thirds of all positive clones. Of the 5 newly described schistosome genes, 1 cDNA had a high degree of homology to the s5a subunit of 26S proteasomes, most significant being with the human protein. The remaining 4 clones showed no significant homologies to any genes sequenced previously. Fructose 1,6-bisphosphate aldolase, Sm21.7, the proteasome homologue and 1 unknown clone (A26) have been expressed in a bacterial expression system and serum produced against each recombinant protein. Immunolocalization showed fructose 1,6-bisphosphate aldolase, Sm21.7 and the proteasome homologue to be most abundant in muscle cells whilst clone A26 was distributed throughout many tissues, but was most abundant in the tegument. Analysis of the cellular immune responses of vaccinated mice showed 3 of the 4 expressed clones to be highly immunogenic, inducing the secretion of large quantities of the Th1-type cytokine interferon gamma.

Multiple line source array for SPECT transmission scans: simulation, phantom and patient studies

Accurate attenuation and scatter corrections in quantitative SPECT studies require attenuation maps of the density distribution in the scanned object. These can be obtained from simultaneous emission/transmission scans.

METHODS

A new method has been developed using a multiple line source array (MLA) for transmission scans, and its performance has been investigated using computer simulations and experimental data. The activity in the central lines of the MLA was higher than at the edges of the system, so that more transmission photons would be directed toward the thicker parts of the human body. A series of transmission-only and simultaneous emission/transmission studies were performed for different phantom configurations and human subjects. Attenuation maps were generated and used in reconstruction of attenuation-corrected emission images.

RESULTS

The mu coefficients for attenuation maps obtained using the MLA system and simulated and experimental data display no artifacts and are qualitatively and quantitatively correct. For phantoms, the agreement between the measured and the true value of mu for water was found to be better than 4%. The attenuation-corrected emission images for the phantom studies demonstrate that the activity in the heart can be accurately reconstructed. A significant qualitative improvement was also obtained when the attenuation correction was used on patient data.

CONCLUSION

Our results indicate that the MLA transmission source can be used in simultaneous transmission/emission imaging to generate accurate attenuation maps. These maps allow for performing an object-specific, attenuation correction of the emission images.

Vaccination against Schistosomiasis: The case for Lung-stage Antigens

The development of an effective vaccine against human schistosomiasis remains a highly desirable yet elusive goal. In this article, Adrian Mountford and Richard Harrop focus attention on an approach that aims to identify proteins from Schistosoma mansoni that are capable of stimulating protective Th1 cell-mediated immune responses. They propose that the most likely source of such antigens is the lung-stage schistosomulum.

Evaluation of cDNA libraries from different developmental stages of Schistosoma mansoni for production of expressed sequence tags (ESTs)

A comparative study of the gene expression profile in different developmental stages of Schistosoma mansoni has been initiated based on the expressed sequence tag (EST) approach. A total of 1401 ESTs were generated from seven different cDNA libraries constructed from four distinct stages of the parasite life cycle. The libraries were first evaluated for their quality for a large-scale cDNA sequencing program. Most of them were shown to have less than 20% useless clones and more than 50% new genes. The redundancy of each library was also analyzed, showing that one adult worm cDNA library was composed of a small number of highly frequent genes. When comparing ESTs from distinct libraries, we could detect that most genes were present only in a single library, but others were expressed in more than one developmental stage and may represent housekeeping genes in the parasite. When considering only once the genes present in more than one library, a total of 466 unique genes were obtained, corresponding to 427 new S. mansoni genes. From the total of unique genes, 20.2% were identified based on homology with genes from other organisms, 8.3% matched S. mansoni characterized genes and 71.5% represent unknown genes.

Minilibraries constructed from cDNA generated by arbitrarily primed RT-PCR: an alternative to normalized libraries for the generation of ESTs from nanogram quantities of mRNA

The generation of expressed sequenced tags (ESTs) depends on the arbitrary selection of individual cDNA clones from libraries. The efficiency of this process reflects the clonal structure of the library used and can be significantly increased using size selected, directional, normalized cDNA libraries. This strategy, however, is not readily applicable when mRNA is limiting, as is the case in the study of complex microorganisms such as parasites, fetal tissues or tumor biopsies. We show here that the construction and systematic sequencing of minilibraries of cDNAs produced by arbitrarily primed PCR provides an alternative means of efficiently generating ESTs in situations where only nanogram quantities of RNA are available. This methodology greatly compensates for unequal message abundance, avoids the need for complex library construction, is equally applicable to the analysis of abundant or rare biological material and is ideally suited to multicenter programmes.

Characterization of dose distribution in radiation therapy plans

As a method of considering only significant radiation doses to different tissues, the ICRU Report 50 recommends taking the dose given to a significant tissue volume (minimum diameter greater then 15 mm) instead of choosing a single, potentially insignificant, voxel value. In order to find this significant volume, we have adapted an emission imaging analysis method to radiation therapy planning. The resulting method finds and characterizes the dose distribution in the volumes of interest in a way that includes spatial arrangement. The data can be used to signal significant hot or cold volumes in the dose plan and to score the plans based on significant dose to the tissues.

Potential allergens stimulate the release of mediators of the allergic response from cells of mast cell lineage in the absence of sensitization with antigen-specific IgE

A number of structurally diverse antigens preferentially stimulate the synthesis of IgE antibodies, but no unifying principle has been proposed that explains the nature of isotype selection. In the present study, we show that common allergens present in bee venom, house dust mite emanations and parasite proteins induce mast cell and basophil degranulation and stimulate interleukin-4 synthesis, and secretion in the absence of antigen-specific IgE. These data point to a linkage between the initial activation of cells of the innate immune system and subsequent adaptive immune responses. They suggest that IgE-independent mast cell and basophil degranulation is predictive of potential allergenicity and can be evaluated by means of a cellular assay. Our study indicates that non-immunological degranulation by prototypic allergens, such as bee venom phospholipase A2 or proteases associated with house dust mite emanations, is critically dependent on enzymatic activity. These findings have potentially important implications for vaccine design in allergic and parasitic disease.

Antigens derived from lung-stage larvae of Schistosoma mansoni are efficient stimulators of proliferation and gamma interferon secretion by lymphocytes from mice vaccinated with attenuated larvae

Protective immunity in C57BL/6 mice exposed to optimally irradiated larvae of Schistosoma mansoni operates against challenge parasites in the lungs and is dependent upon T-helper 1 (Th1) lymphocytes which secrete abundant gamma interferon (IFN-gamma). As an initial step in the identification of the molecules which mediate this immunity, antigenic materials released by larvae at various times during in vitro culture were compared for the ability to induce proliferation of lymph node cells recovered from mice 4 to 6 days after exposure to attenuated parasites. Cells from mice vaccinated with cercariae proliferated most strongly to larval antigens released soon after transformation. In contrast, cells from mice immunized with lung-stage schistosomula responded poorly to these early secretions but proliferated vigorously to antigens released by older larvae. In further studies on the cytokine profile of the responding lymphocytes, it was observed that the balance between IFN-gamma and interleukin-4 (IL-4) secretion depended on the source of antigen used for restimulation. Thus, material released between days 6 and 8 by in vitro-cultured larvae, and the soluble extracts of whole lung-stage larvae, induced abundant IFN-gamma but little IL-4. This finding implies that an overwhelming proportion of the lymphocytes responsive to lung-stage antigens had the Th1 phenotype. In contrast, antigens from cercariae and skin-stage larvae induced the lowest levels of IFN-gamma but higher levels of IL-4. It appears that a proportion of the cells with specificities for early antigens had the Th2 or Th0 phenotype. Our results emphasize that antigens from lung-stage larvae are an important source of potentially protective molecules.

Protein synthesis and release by cultured schistosomula of Schistosoma mansoni

The lung schistosomulum of Schistosoma mansoni is the target of protective immunity in mice singly vaccinated with irradiated cercariae. Since the effector responses are T cell-mediated, their initiation requires the release of antigens from the intact parasite. We have used the technique of biosynthetic labelling with [35S]methionine, before and after transformation of the cercariae, to analyse the kinetics of protein synthesis and release by the schistosomulum. In addition, the proteins present in the soluble fraction of the parasite and those released during in vitro culture have been characterized. During a 7-day culture period schistosomula derived from labelled cercariae lost proteins most rapidly within the first 3 h after transformation. Two proteins of molecular weight 61 and 20 kDa were dominant and may correspond to areas of proteolytic activity. Analysis of the rate of protein synthesis of schistosomula labelled after transformation revealed four different phases, which may relate to the developmental processes occurring in vivo. During the first 24 h, synthesis was very low, increasing to a plateau and then rising to a peak at day 8; therefore the rate declined rapidly. Whilst some stage-specific synthesis of proteins was detected in the soluble fractions of the parasite bodies, the pattern of proteins released by cultured larvae was remarkably uniform. At least 15 proteins were detected by autoradiography with bands at 61, 45 and 20 kDa being particularly prominent. These proteins merit further study as potential mediators of the protective immune response.

Irradiation of Schistosoma mansoni cercariae impairs neuromuscular function in developing schistosomula

Optimally attenuated larvae of Schistosoma mansoni (20 krad) are incapable of migrating farther than the lungs, and they induce high levels of resistance in mice to a subsequent challenge infection. The effect of gamma radiation on the parasite is described and related to the migratory pattern of attenuated larvae. Scanning electron microscopy revealed marked morphological differences between normal and irradiated larvae at the lung stage of development. The latter exhibited random constrictions, probably resulting from contraction of circular muscle fibers, at intervals along the length of the body and showed subtle differences in motility. We suggest these abnormalities account for persistence of attenuated larvae in the skin-draining lymph nodes and lungs, 2 events that are instrumental to the induction of protective immunity in this vaccine model.

Full data utilization in PVI using the 3D radon transform

An algorithm is described for three-dimensional (3D) image reconstruction in positron volume imaging (PVI) using the inversion of the 3D radon transform (RT) for a truncated cylindrical detector geometry. A discrete version of the 3D RT is formed in a 3D histogram from the event-line coordinates of the detected events. The histogram entries represent the plane integrals of the activity in the field of view. Conventional inversion of the x-ray transform (XT) excludes oblique events in non-iterative reconstruction methods. by employing a spatially varying angular acceptance of events into the histogrammed plane integrals of the 3D RT, it is possible to include most of the detected oblique events in the reconstruction of the image using the standard 3D RT inversion formula. the oblique events are added to the histogram with a partial weight compared to those in complete (XT) projections. This single-pass reconstruction image has better statistical noise properties than images formed by RT inversion from complete XT projections, but only for some detector geometries is it significantly better. Monte Carlo simulations were used to study the statistical noise in images reconstructed using the new algorithm. The inherent difference in the axial versus the transaxial statistical noise in images reconstructed from truncated detectors is noted and is found to increase by including oblique events with this new algorithm.

Use of transputers in a 3-D positron emission tomograph

The use of a VME-bus-based transputer network as a parallel processing engine for positron volume imaging (PVI) is discussed. The authors find that the speedups of parallel networks depend on two major factors, the ratio of computation to communication for a task and the size of the task, and give a simple model to explore the limits on speedups. Through actual implementation it is shown that real-time PVI data acquisition can be achieved with about 20 transputer nodes, and it is estimated that three-dimensional (3-D) image reconstruction can be achieved within 10 min using 200 nodes. Larger images and a larger number of histograms can readily be accommodated using the same parallel algorithms, as the model presented places no limits on the size of the images. The versatility and scalability of transputers makes them very suitable for use in PVI tomographs in that the same transputers can be used for speeding up data acquisition, image reconstruction, and display.

Correlations of regional postmortem enzyme activities with premortem local glucose metabolic rates in Alzheimer's disease

Correlations were sought between local cerebral metabolic rates (LCMRs) for glucose in various regions of the cortex, determined in premortem PET scans, with the regional activities of choline acetyltransferase (ChAT), acetylcholinesterase (AChE), beta-glucuronidase (Gluc, a probable index of reactive gliosis), and phosphate-activated glutaminase (PAG, a possible indice of the large pyramidal neurons) measured on postmortem tissue. Significant negative correlations between LCMRs and Gluc activities were found in 6 PET-scanned cases of Alzheimer disease (AD), and positive correlations of LCMRs with PAG were found in 5. By contrast, a positive correlation with ChAT and AChE was found in only 1. The results are consistent with the metabolic deficits in AD being primarily a reflection of local neuronal loss and gliosis. Similar data on two cases of Huntington's disease showed no significant correlations, while 1 patient with Parkinson dementia showed a significant (negative) correlation only with Gluc.

18Fluorodeoxyglucose positron emission tomography studies in presumed Alzheimer cases, including 13 serial scans

Positron emission tomographic (PET) data on local cerebral metabolic rates for glucose (LCMR) are reported for 32 regions of interest (ROI)s in cross-sectional studies on 57 patients with clinically diagnosed Alzheimer's disease (AD) and 20 neurologically normal controls, and in serial studies on 13 of the AD cases, including a familial, young-onset case where the diagnosis has been confirmed at autopsy. Extensive psychological testing was done on all the AD cases. Almost all cortical regions showed a significant decline in LCMR with age in the control subjects. There were the expected cortical metabolic deficits in AD and the serial studies showed a general increase in such deficits over time in 12 of the 13 cases. The regions showing the greatest declines with time in serial studies are the same as those showing the most severe deficiencies in cross-sectional studies. The young-onset case did not show a greater rate of metabolic decline than many of the older cases studied. Results on individual psychological tests tended to correlate with metabolic rates in multiple, rather than single, cortical regions, suggesting intact neuronal networks are required for good performance. The correlations with cortical metabolic activity found were of a sign indicating that the higher the metabolic rates and the better the left:right asymmetry index, the better was the performance.

Cortical glutaminase, beta-glucuronidase and glucose utilization in Alzheimer's disease

Large pyramidal neurons of rat and human neocortex stain immunohistochemically for phosphate-activated glutaminase (PAG). In a limited number of postmortem brains, we find large reductions in cortical PAG activity in Alzheimer's disease (AD). This finding is consistent with histological evidence that pyramidal neurons are affected in AD. The reductions are greater than those found in the same samples in choline acetyltransferase (ChAT) but the possible deleterious effects of coma and similar premortem factors on human PAG activity have yet to be assessed. The activity of beta-glucuronidase, a lysosomal enzyme which occurs in reactive astrocytes, is elevated in the same samples. Positron emission tomography (PET) studies, using 18F-fluorodeoxyglucose (FDG), have demonstrated significant deficiencies in glucose metabolism in the cortex in AD, with the parietal, temporal and some frontal areas being particularly affected. We found in serial scans of 13 AD cases, including one relatively young (44-46 year old) familial case, an exacerbation of the defect over time in most cases. We have found a negative correlation between the regional metabolic rates for glucose (LCMR(s] measured premortem and the beta-glucuronidase activities measured postmortem on a few AD cases that have come to autopsy. The correlations between LCMR(s) and PAG and ChAT activities tend to be positive. The results are consistent with previous suggestions that decreased LCMR(s) in AD reflect local neuronal loss and gliosis.

Crossed cerebellar and uncrossed basal ganglia and thalamic diaschisis in Alzheimer's disease

We detected crossed cerebellar as well as uncrossed basal ganglia and thalamic diaschisis in Alzheimer's disease by positron emission tomography (PET) using 18F-fluorodeoxyglucose. We studied a series of 26 consecutive, clinically diagnosed Alzheimer cases, including 6 proven by later autopsy, and compared them with 9 age-matched controls. We calculated asymmetry indices (AIs) of cerebral metabolic rate for matched left-right regions of interest (ROIs) and determined the extent of diaschisis by correlative analyses. For the Alzheimer group, we found cerebellar AIs correlated negatively, and thalamic AIs positively, with those of the cerebral hemisphere and frontal, temporal, parietal, and angular cortices, while basal ganglia AIs correlated positively with frontal cortical AIs. The only significant correlation of AIs for normal subjects was between the thalamus and cerebral hemisphere. These data indicate that PET is a sensitive technique for detecting diaschisis.