AML-loaded DC generate Th1-type cellular immune responses in vitro

BACKGROUND

The generation of AML-specific T-lymphocyte responses by leukemia-derived DC has been documented by multiple investigators and is being pursued clinically. An obstacle to widespread use of this strategy is that it has not been possible to generate leukemic DC from all patients, and an alternative approach is needed if the majority of leukemia patients are to receive therapeutic vaccination in conjunction with other treatment protocols.

METHODS

In the present study, we generated DC from CD14-selected monocytes isolated from healthy donor PBPC and loaded them with a total cell lysate from AML patient blasts.

RESULTS

Immature in vitro-derived DC exhibited robust phagocytic activity, and mature DC demonstrated high expression of CD80, CD83, CD86 and the chemokine receptor CCR7, important for DC migration to local lymph nodes. Mature, Ag-loaded DC were used as APC for leukemia-specific cytotoxic T-lymphocyte (CTL) induction and demonstrated cytotoxic activity against leukemic targets. CTL lysis was Ag-specific, with killing of both allogeneic leukemic blasts and autologous DC loaded with allogeneic AML lysate. HLA-matched controls were not lysed in our system.

DISCUSSION

These data support further research into the use of this strategy as an alternative approach to leukemia-derived DC vaccination.

Treatment of mice with IL-12 DNA constructs leads to augmented NK activity in lungs but low IFN-gamma release -- implications for Bordetella pertussis infections following aerosol challenge

Interleukin-12 protein has been widely used experimentally in therapeutic and adjuvant settings in the treatment of different diseases including intra-cellular bacterial infections. The in vivo clearance of Bordetella pertussis infections in naive mice and in animals vaccinated with whole cell vaccine is considered to be a Th-1 dependent mechanism. Furthermore, the addition of IL-12 protein to an acellular pertussis vaccine increases the efficacy of this vaccine. Whilst the use of IL-12 protein is often beneficial, a number of problems there are associated with this cytokine including toxicities and down regulation of normal immune functions. The use of DNA constructs encoding this cytokine may be a way of achieving maximum therapeutic benefit with minimum toxicity. The aims of this study were to optimise the effects of two IL-12 DNA constructs, especially with respect to augmenting pulmonary immune responsiveness and to compare the effect of IL-12 DNA and IL-12 protein on bacterial colonisation of lungs following aerosol challenge with B. pertussis. We found that IL-12 DNA constructs augmented the activity of pulmonary NK cells but had little effect on the course of B. pertussis infections in mice. In contrast to IL-12 protein, the DNA constructs had no immunosuppressive effects on splenic lymphocyte mitogen responses.

High dose interleukin-12 exacerbates Bordetella pertussis infection and is associated with suppression of cell-mediated immunity in a murine aerosol challenge model

The in-vivo clearance of Bordetella pertussis infections in murine models in naive mice and animals vaccinated with whole-cell vaccine is considered to be via a Th-1-dependent mechanism in which interleukin-12 (IL)-12 may play a prominent role. It has also been demonstrated clearly that the treatment of animals with macrophage-derived IL-12 administered with an acellular vaccine can increase the efficacy of this vaccine preparation to levels seen with the whole-cell vaccine. However, the effects of exogenously added IL-12 on immune responses in non-vaccinated B. pertussis-challenged mice remain unclear, with two studies giving contradictory findings. In this study we have treated mice with escalating doses of mIL-12 (0.1-10 microg/mouse) prior to challenge with B. pertussis (using an aerosol challenge model of infection). The ability of mice to clear infection was assessed in IL-12 treated and in phosphate buffered saline (PBS) control animals at days 6 and 13 post-challenge. Lymphoid cells were isolated from spleen and cell-mediated immune responses assessed at days 1, 6 and 13 post-challenge. In addition, the direct effects of high-dose IL-12 on challenged mice was assessed by checking natural killer (NK) activity from isolated lung and spleen lymphoid cells as well as interferon-gamma (IFN-gamma) generation from isolated cells and serum at day 1 post-challenge. The results from this study show that bacterial colonization of the lungs is actually enhanced following treatment with high-dose IL-12. This is associated with impaired cellular immune responses. The mechanisms associated with the immunosuppressive effects of IL-12 are discussed.

Developments in reduction and replacement of in vivo toxicity and potency tests for pertussis vaccines

The regulatory control of pertussis vaccines, as for other biological products, requires that they conform to specified standards of safety and efficacy. The current potency test for whole cell vaccines, the intracerebral mouse protection test (AMPT) is still the only such assay that has shown a correlation with protection in children. An alternative in vivo assay based on non-lethal aerosol challenge of mice has been assessed as a replacement for the current AMPT. An in vitro assay based on determination of reactive nitrogen/oxygen intermediates produced as a result of macrophage activation has also been investigated as a potential replacement for the in vivo challenge test. On the other hand, for safety testing, an enzymatic-HPLC coupled assay using a fluorescein-labelled G alpha(i3)C20 peptide to measure the enzymatic ribosylation activity of active pertussis toxin was evaluated for its suitability as a replacement for the current histamine sensitisation test (HIST). An assay for adenylate cyclase toxin (ACT)-related toxicity, based on measuring the ACT-induced oxidative burst in macrophage-like cell cultures has also been investigated. Although some questions still need to be answered in relation to the development of suitable replacements for in vivo tests of pertussis vaccines, the prospects for further improvements are promising.

Comparison of the bioactivity of reference preparations for assaying Bordetella pertussis toxin activity in vaccines by the histamine sensitisation and Chinese hamster ovary-cell tests: assessment of validity of expression of activity in terms of protein concentration

Pertussis toxin (PT) in its detoxified form is an important antigenic component of both acellular and whole cell pertussis vaccines. Limits on the content of active PT in acellular vaccines are set in official monographs (EP, WHO, USP) and evidence of compliance is therefore, required by regulatory authorities. The two assay methods which are currently used by most manufacturers and official national control laboratories to monitor residual PT activity in acellular pertussis vaccines (and also in whole cell vaccines) are histamine sensitising (HIST) assays and Chinese hamster ovary (CHO) cell assays. Currently, different reference preparations of PT are used by individual laboratories for these tests. We therefore organised an international collaborative study to examine, by these two assay methods, two freeze-dried purified preparations of PT, one preparation in ampoules coded JNIH-5 and one preparation in ampoules coded 90/518, together with in-house reference (IHR) preparations in current use. Data from this study confirm that both JNIH-5 and 90/518 show biological activity both in HIST assays and in CHO-cell assays. Both HSD50 and ED50 values obtained in this study differ significantly between laboratories and thus show that biological activity is not determined by the nominal masses of preparations. Estimates of relative potency of 90/518 in terms of JNIH-5 per ampoule for the HIST assays do not differ significantly between laboratories. The overall mean estimates of relative potency of 90/518 in terms of JNIH-5 do not differ significantly between the two methods. Data from this study further indicate that the biological activity of different preparations was not directly related to their stated protein content. The use of protein content to indicate the level of PT activity in different preparations would give misleading results. Thus, use of a common standard is shown to greatly improve between laboratory agreement of estimates.

Investigation of role of nitric oxide in protection from Bordetella pertussis respiratory challenge

The mechanism whereby whole-cell pertussis vaccines (WCV) confer protection against Bordetella pertussis is still not fully understood. We have previously reported that macrophage activation produced by vaccination with WCV is associated with induction of NO synthesis by macrophages in response to in vitro stimulation with B. pertussis antigens. To determine whether NO production is an effector of protection or simply a marker of activation, the susceptibility of inducible nitric oxide synthase (type II, iNOS) knockout mice to infection with B. pertussis was examined. We showed that iNOS knockout mice were more susceptible to B. pertussis respiratory challenge than wild-type mice. iNOS-deficient mice also developed a less effective protective response than wild-type mice after the same immunization with WCV. This suggests that NO plays an important role in effecting protection against B. pertussis challenge.

Lymphoid apoptosis and myeloid hyperplasia in CCAAT displacement protein mutant mice

CCAAT displacement protein (cux/CDP) is an atypical homeodomain protein that represses expression of several developmentally regulated lymphoid and myeloid genes in vitro, including gp91-phox, immunoglobulin heavy chain, the T-cell receptor beta and gamma chains, and CD8. To determine how this activity affects cell development in vivo, a hypomorphic allele of cux/CDP was created by gene targeting. Homozygous mutant mice (cux/CDP(Delta HD/Delta HD)) demonstrated a partial neonatal lethality phenotype. Surviving animals suffered from a wasting disease, which usually resulted in death between 2 and 3 weeks of age. Analysis of T lymphopoiesis demonstrated that cux/CDP(Delta HD/Delta HD) mice had dramatically reduced thymic cellularity due to enhanced apoptosis, with a preferential loss of CD4(+)CD8(+) thymocytes. Ectopic CD25 expression was also observed in maturing thymocytes. B lymphopoiesis was also perturbed, with a 2- to 3-fold reduction in total bone marrow B-lineage cells and a preferential loss of cells in transition from pro-B/pre-BI to pre-BII stages due to enhanced apoptosis. These lymphoid abnormalities were independent of effects related to antigen receptor rearrangement. In contrast to the lymphoid demise, cux/CDP(Delta HD/Delta HD) mice demonstrated myeloid hyperplasia. Bone marrow reconstitution experiments identified that many of the hematopoietic defects were linked to microenvironmental effects, suggesting that underexpression of survival factors or overexpression of death-inducing factors accounted for the phenotypes observed. Tumor necrosis factor (TNF) levels were elevated in several tissues, especially thymus, suggesting that TNF may be a target gene for cux/CDP-mediated repression. These data suggest that cux/CDP regulates normal hematopoiesis, in part, by modulating the levels of survival and/or apoptosis factors expressed by the microenvironment.

Laboratory testing of whole cell pertussis vaccine: a WHO proficiency study using the Kendrick test

Whole cell pertussis vaccine (WCV), commonly in combination with vaccines for diphtheria and tetanus, has an important role in reducing morbidity and mortality among children in most parts of the world. Testing to assure the efficacy of such vaccines is essential. We have, therefore, carried out, under the Global Training Network (GTN) of the Department of Vaccines and Biologicals at the World Health Organization (WHO), a proficiency study involving 13 laboratories in 12 countries that routinely test WCV. Two vaccine samples were tested in this study and represented samples which were expected clearly either to pass (sample B, a full strength vaccine) or to fail (sample A, 1/8 strength of vaccine B). Data from this study showed good performance by the majority of participants. Most assays were statistically valid and were carried out to the level of precision achieved for these assays in previous studies. This study also indicated that, relative to the assay precision, the in-house reference (IHR) preparations are in general accurately calibrated. Statistically valid assays of the sub-potent vaccine, A, showed it to fail in all except one laboratory. Statistically valid assays of the potent vaccine, B, showed it to pass in all laboratories. Nevertheless, the between laboratory variability of estimates for vaccine B, and for comparisons of the two vaccine samples suggested that there are some differences in results in different laboratories. The introduction of a common working standard may assist in reducing inter-laboratory variation. This study has shown clearly satisfactory performance by most laboratories. However, a serious problem was detected in one laboratory where the sub-potent vaccine A could have been passed and was not distinguished from the eight-fold more potent vaccine B. There were also indications of possible problems in several other laboratories, where IHR preparation may not be accurately calibrated or where vaccine samples A and B may not be completely distinguished. Although this study provides reassurance that most laboratories perform well, it demonstrates the essential role of ongoing proficiency studies in high-lighting problems.

[Detection of malondialdehyde-DNA adduct level by 32P-postlabeling assay in normal human esophageal epithelium and esophageal squamous cell carcinoma]

OBJECTIVE

To study whether the main malondialdehyde-DNA adduct (M1-dG) produced by lipid peroxidation is involved in the carcinogenesis of esophagus.

METHODS

DNA samples were isolated from normal esophageal epithelium (n = 32) obtained by biopsy and esophageal squamous cell carcinoma specimens (n = 30) obtained by surgery. All tissue samples came from individuals living in Linxian, Henan, a high-risk area of esophageal cancer. Contents of M1-dG adducts were detected by 32P-postlabeling method.

RESULTS

M1-dG adducts were detectable both in the normal and cancerous tissue samples. However, normal esophageal epithelial tissues exhibited significantly lower levels of M1-dG adducts (median 3.4, range 1.7/10(8)-55.4/10(8) nucleotides) than those found in esophageal cancer tissues (median 14.1, range 1.4/10(8)-59.0/10(8) nucleotides, P < 0.0001). The adduct levels were neither associated with gender, age, tobacco smoking status or genetic polymorphism in the CYP2E1, an enzyme participating in the oxidation of ethanol to form reactive free radicals.

CONCLUSIONS

Our findings provide evidence that DNA damage, resulted from lipid peroxidation, can accumulate in the normal human esophageal tissue and reach relatively high level in cancer tissue which suggests that M1-dG adducts may be involved in the initiation and progression of cancer with its mutagenic and carcinogenic effects.

International collaborative study: evaluation of proposed International Reference Reagent of pertussis antiserum (mouse) 97/642

A freeze dried preparation of mouse serum in vials coded 97/642 containing antibodies to five pertussis antigens [pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), fimbriae type 2 and 3 (Fim 2 and 3)] has been assessed for its suitability as an international reference reagent in an international collaborative study by thirteen laboratories in nine countries. This serum has been compared with U.S. Standard Pertussis Antiserum (mouse) Lot No. 1 (US Lot 1), which has been in use since 1995, for antibodies for each antigen. Calibration of the proposed International Reference Reagent of Pertussis Antiserum (pIRR) in terms of US Lot 1 gives results which are broadly consistent between laboratories for antibodies to each antigen, although the between-laboratory differences are larger than those seen for comparison of identical sera. Calibration of two positive control sera in terms of the pIRR gave similar between laboratory variability of estimates to that obtained when the same sera were calibrated in terms of US Lot 1. Overall continuity of estimates is maintained if units are assigned to the pIRR based on its calibration in terms of US Lot 1 in this study. Data presently available indicate that the pIRR is sufficiently stable to serve as a reference reagent. It was therefore recommended, with the agreement of all participants, that the preparation in vials coded 97/642 be established as the First International Reference Reagent for Pertussis Antiserum, mouse, with assigned unitages 16 units of anti-PT per vial, 143 units of anti-FHA per vial and 30 units of anti-PRN per vial based on its calibration in terms of US Lot 1. These unitages are also consistent with calibration of 97/642 in terms of the Japanese preparations JNIH-11 for anti-FHA and of JNIH-12 for anti-PT. Purified antigens for Fim 2 and Fim 3 are not readily available and an arbitrary value of 32 units per vial is suggested for anti-Fim 2 and 3 mixture. These recommendations were agreed by the Expert Committee on Biological Standardization of the World Health Organization.