Efficacy of oryzalin and associated histological changes in Cryptosporidium-infected neonatal rats

This paper reports the anti-cryptosporidial effects of, and concomitant amelioration of the histological changes in the gut of neonatal rats with intestinal cryptosporidiosis treated with the dinitroaniline, oryzalin. The ED50 was determined to be 7 mg/kg using twice daily doses administered for 3 consecutive days. A maximum inhibition of 85.5% was achieved at 25 mg/kg and this inhibition remained constant despite increasing the oryzalin dose to 200 mg/kg. Cryptosporidiosis significantly decreased the intestinal villus/crypt (VC) ratio by approximately 50% (duodenum = 2.3, jejunum = 2.5 and ileum = 1.7) when compared to uninfected untreated controls (duodenum = 4.3, jejunum = 5.9 and ileum = 4.5). Treatment with oryzalin doubled the VC ratio in the duodenum, jejunum and ileum following doses of 5 mg, 50 mg and 200 mg/kg respectively. Oryzalin concentrations in the small intestine contents and plasma were determined, using HPLC, at 0.5, 1 and 2 h after dosing. The much greater dose required to return VC ratios to normal in the ileum (200 mg/kg) compared to the duodenum (6.25 mg/kg) appeared to reflect the decreased concentration of the drug in the distal small intestine. Concentrations of oryzalin equivalent to the in vitro IC50 were maintained for 2 h in the first half of the small intestine following a single dose of 100 mg/kg.

M-Vax: an autologous, hapten-modified vaccine for human cancer

A novel approach to active immunotherapy has been devised based on modification of autologous cancer cells with the hapten, dinitrophenyl (DNP). This technology is being developed by AVAX Technologies as a treatment for melanoma under the brand name, M-Vax(TM). The treatment program consists of multiple intradermal injections of DNP-modified autologous tumour cells mixed with Bacille Calmette-Guérin (BCG). DNP-vaccine administration to patients with metastatic melanoma induces a unique reaction - the development of inflammation in metastatic masses. The inflammation is mediated by IFN-gamma-producing T-lymphocytes, some of which represent expansion of novel clones. Following DNP-vaccine treatment, almost all patients develop delayed-type hypersensitivity (DTH) to autologous, DNP-modified melanoma cells; approximately half also exhibit DTH to autologous, unmodified tumour cells. The toxicity of the vaccine is mild, consisting mainly of papules or pustules at the injection sites. Clinical trials have been conducted in two populations of melanoma patients: stage IV with measurable metastases and clinical stage III patients, rendered tumour-free by lymphadenectomy. In 83 patients with measurable metastases, there were 11 antitumour responses: two complete responses (CRs), four partial responses (PRs) and five mixed. Both CRs and two of four PRs occurred in patients with lung metastases. In 214 stage III patients the 5-year overall survival rate was 46% (one nodal site = 48%, in-transit metastases = 50%, two nodal sites = 36%). In both populations, the induction of DTH to unmodified autologous tumour cells was associated with significantly longer survival. This technology is applicable to other human cancers and clinical trials have been initiated with ovarian adenocarcinoma. There appear to be no insurmountable impediments to applying this approach to much larger numbers of patients or to developing it as a standard cancer treatment.

Plasmodium: assessment of the antimalarial potential of trifluralin and related compounds using a rat model of malaria, Rattus norvegicus

A rodent model of malaria, Plasmodium berghei was used to assess the antimalarial potential of dinitroaniline herbicides. Trifluralin, pendimethalin, oryzalin, and benfluralin were all active against P. berghei in vitro at, or close to, submicromolar concentrations, with a rank order of potency similar to that against other protozoa. The dinitroanilines did not elicit a cytotoxic effect against a mammalian cell line at concentrations 100-fold higher than those for activity against P. berghei. Neither trifluralin nor oryzalin exhibited any antimalarial activity in vivo after oral administration at the maximum dose tolerated by the host. In a pharmacokinetic study, it was found that the lack of in vivo antimalarial activity was due to poor absorption. Other DNs which have better absorption characteristics than either trifluralin or oryzalin may offer more scope for antimalarial activity in vivo.

A comparison of the effects of two dinitroanilines against Cryptosporidium parvum in vitro and in vivo in neonatal mice and rats

The effects of two dinitroanilines, oryzalin and trifluralin, were compared against Cryptosporidium parvum, in vitro using HCT-8 cells and in vivo using neonatal Swiss ARC mice and Wistar neonatal rats. In vitro, oryzalin and trifluralin exhibited IC(50) values (concentration necessary to cause a 50% inhibition) of 750 and 800 nM, respectively. A viability assay showed that neither compound produced a cytotoxic effect on the host cells at concentrations as high as 1 microM. The in vivo component of this study consisted of inoculation of neonatal mice and neonatal rats with 10(5) viable oocysts of C. parvum per animal and the subsequent treatment of this infection with trifluralin and oryzalin administered via gastric intubation. At doses of 100 mg kg(-1) body weight administered twice daily for 3 consecutive days, trifluralin had no statistically significant effect on the number of oocysts recovered from the gut of either rats or mice compared with controls, whereas at the same concentration, oryzalin caused 90 and 79% inhibition of oocysts recovered from mice and rats, respectively.

Synthesis and evaluation of dinitroanilines for treatment of cryptosporidiosis

The efficacy of a series of dinitroaniline herbicide derivatives for the treatment of Cryptosporidium parvum infections has been studied. The lead compounds oryzalin (compound 1) and trifluralin (compound 2) have low water solubility (<3 ppm) which was alleged to be a major contributor to their poor pharmacokinetic availability. Derivatives of compounds 1 and 2 were synthesized. In these derivatives the functionality at the C-1 amine position or the C-4 position was substituted with groups with various hydrophilicities to determine if a direct relation existed between water solubility and overall activity. The chlorinated precursors of these derivatives were also examined and were found to be less active in the C. parvum assays, a result in direct contrast to earlier work with Leishmania. Enhanced water solubility alone did not overcome the drug availability problem; however, several candidates with similar activities but with toxicities lower than those of the lead compounds were produced.

Activation markers on T cells infiltrating melanoma metastases after therapy with dinitrophenyl-conjugated vaccine

Treatment of metastatic melanoma patients with an autologous vaccine modified by the hapten, dinitrophenyl (DNP), produces a striking immunological effect: the induction of clinically evident inflammatory responses in metastatic tumors. Histological examination shows these tumors to be infiltrated with T lymphocytes. We studied the expression of activation markers on those cells and compared them with matched peripheral blood lymphocytes (PBL) and with lymphocytes extracted from metastases before treatment with DNP-conjugated vaccine. The median fraction of cells that were T cells in post-vaccine tumors was 41%, as compared with 9% in pre-treatment tumors, and those T cells were predominantly CD8+ (mean CD8/CD4 ratio = 5.0). A high proportion of both pre- and post-treatment infiltrating T cells expressed HLA-DR (mean +/- SE = 48% +/- 4%), CD69 (56% +/- 7%), and ganglioside GD3 (68% +/- 5%). This distinguished them from matched PBL in which expression of those markers was significantly lower (HLA-DR = 10% +/- 2%; CD69 = 2% +/- 0.4%; GD3 = 49% +/- 4%). These changes were not accompanied by increased cell-surface expression of interleukin-2 (IL-2) receptors, either CD25 or p75, which were expressed by 1%-2% and 12% of tumor-infiltrating lymphocytes (TIL), respectively. The pattern of activation marker expression that we identified appears to be characteristic of tissue T cells with the memory phenotype. The low expression of IL-2 receptors could indicate functional impairment of TIL in situ, perhaps because of inhibitory molecules produced by melanoma cells.

Mechanism of densensitization in DNCB-contact sensitive guinea pigs

Contact sensitivity to dinitrochlorobenzene (DNCB) in guinea pigs could be rapidly suppressed by intravenous injection of dinitrobenzene sulfonic acid sodium salt (DNBSO3). This suppression is transient and antigen-specific. Macrophages from desensitized animals are not inactivated as shown by their ability to react, both in vivo and in vitro to lymphokines produced in a separate system. Therefore, effector lymphocytes are considered the target for the desensitizing antigen. Using an adoptive transfer system it was demonstrated that effector lymphocytes are inactivated by a direct effect of the hapten. Since this inactivation can be reversed by trypsin treatment, a receptor blockade of effector lymphocytes is proposed as the mechanism of desensitization of DNCB-contact sensitive guinea pigs. This does not exclude the possibility that additional mechanisms such as suppressor cells, compartmentalization or endogenous proliferation of lymph node lymphocytes may play an additional role.

[Study of indirect active immunotherapy of Ehrlich carcinoma]

Preliminary results of active immunotherapy ,both in vitro and in vivo, about ascitical Ehrlich carcinoma transplanted in albinic swiss mice are presented. In the in vitro experiment, tumor cells were marked with the immunoglobulin, anti-tumor-associated antigens (TAA) and were coupled to a dinitrophenyl radical (Ig DNP anti-TAA). These cells were meaningfully hindered from migration in presence of swiss albinic mice's splenic cells. These mice were sensibilized to the tumor cells marked with Ig-DNP. The injection of a Ig-DNP anti-TAA 0,3 ml, every third days, intraperitoneal way, in a span of 21 days, in albinical swiss mice with a transplant of 3 X 10(5) Ehrlich carcinoma cells (group A) 24 hours before, constituted the in vivo test. The growth ought to be compared to an Ig-DNP tolerant group (group B), which received equal quantities of tumor cells and followed the same plan of treatment, as well as to another control group transplanted under the same conditions, but with no treatment (group C). Eight days from the experiment, there was a clear difference between group A and groups B and C. The last two groups died from 13th to the 26th day after the transplant. On the contrary, the whore group A continued alive and with no sign of ascitical tumor. Nevertheless, an animal of group A died after the 28th day, due to a solid tumor in the abdominal wall.