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© 2015 American Chemical Society.A series of 6-hetaryloxy benzoxaborole compounds was designed and synthesized for a structure-activity relationship (SAR) investigation to assess the changes in antimalarial activity which result from 6-aryloxy structural v

The optimization of a series of benzimidazole-benzoxaborole hybrid molecules linked via a ketone that exhibit good activity against Onchocerca volvulus , a filarial nematode responsible for the disease onchocerciasis, also known as river blindness, is described. The lead identified in this series, 21 (AN15470), was found to have acceptable pharmacokinetic properties to enable an evaluation following oral dosing in an animal model of onchocerciasis. Compound 21 was effective in killing worms implanted in Mongolian gerbils when dosed orally as a suspension at 100 mg/kg/day for 14 days but not when dosed orally at 100 mg/kg/day for 7 days.

New antimalarial drugs are needed. The benzoxaborole AN13762 showed excellent activity against cultured Plasmodium falciparum , against fresh Ugandan P. falciparum isolates, and in murine malaria models. To gain mechanistic insights, we selected in vitro for P. falciparum isolates resistant to AN13762. In all of 11 independent selections with 100 to 200 nM AN13762, the 50% inhibitory concentration (IC 50 ) increased from 18-118 nM to 180-890 nM, and whole-genome sequencing of resistant parasites demonstrated mutations in prodrug activation and resistance esterase (PfPARE). The introduction of PfPARE mutations led to a similar level of resistance, and recombinant PfPARE hydrolyzed AN13762 to the benzoxaborole AN10248, which has activity similar to that of AN13762 but for which selection of resistance was not readily achieved. Parasites further selected with micromolar concentrations of AN13762 developed higher-level resistance (IC 50 , 1.9 to 5.0 μM), and sequencing revealed additional mutations in any of 5 genes, 4 of which were associated with ubiquitination/sumoylation enzyme cascades; the introduction of one of these mutations, in SUMO-activating enzyme subunit 2, led to a similar level of resistance. The other gene mutated in highly resistant parasites encodes the P. falciparum cleavage and specificity factor homolog PfCPSF3, previously identified as the antimalarial target of another benzoxaborole. Parasites selected for resistance to AN13762 were cross-resistant with a close analog, AN13956, but not with standard antimalarials, AN10248, or other benzoxaboroles known to have different P. falciparum targets. Thus, AN13762 appears to have a novel mechanism of antimalarial action and multiple mechanisms of resistance, including loss of function of PfPARE preventing activation to AN10248, followed by alterations in ubiquitination/sumoylation pathways or PfCPSF3. IMPORTANCE Benzoxaboroles are under study as potential new drugs to treat malaria. One benzoxaborole, AN13762, has potent activity and promising features, but its mechanisms of action and resistance are unknown. To gain insights into these mechanisms, we cultured malaria parasites with nonlethal concentrations of AN13762 and generated parasites with varied levels of resistance. Parasites with low-level resistance had mutations in PfPARE, which processes AN13762 into an active metabolite; PfPARE mutations prevented this processing. Parasites with high-level resistance had mutations in any of a number of enzymes, mostly those involved in stress responses. Parasites selected for AN13762 resistance were not resistant to other antimalarials, suggesting novel mechanisms of action and resistance for AN13762, a valuable feature for a new class of antimalarial drugs., (Copyright © 2020 Sindhe et al.)

The elimination of filarial diseases such as onchocerciasis and lymphatic filariasis is hampered by the lack of a macrofilaricidal-adult worm killing-drug. In the present study, we tested the in vivo efficacy of AN11251, a boron-pleuromutilin that targets endosymbiotic Wolbachia bacteria from filarial nematodes and compared its efficacy to doxycycline and rifampicin. Doxycycline and rifampicin were previously shown to deplete Wolbachia endosymbionts leading to a permanent sterilization of the female adult filariae and adult worm death in human clinical studies. Twice-daily oral treatment of Litomosoides sigmodontis-infected mice with 200 mg/kg AN11251 for 10 days achieved a Wolbachia depletion > 99.9% in the adult worms, exceeding the Wolbachia reduction by 10-day treatments with bioequivalent human doses of doxycycline and a similar reduction as high-dose rifampicin (35 mg/kg). Wolbachia reductions of > 99% were also accomplished by 14 days of oral AN11251 at a lower twice-daily dose (50 mg/kg) or once-per-day 200 mg/kg AN11251 treatments. The combinations tested of AN11251 with doxycycline had no clear beneficial impact on Wolbachia depletion, achieving a > 97% Wolbachia reduction with 7 days of treatment. These results indicate that AN11251 is superior to doxycycline and comparable to high-dose rifampicin in the L. sigmodontis mouse model, allowing treatment regimens as short as 10-14 days. Therefore, AN11251 represents a promising pre-clinical candidate that was identified in the L. sigmodontis model, and could be further evaluated and developed as potential clinical candidate for human lymphatic filariasis and onchocerciasis., Competing Interests: I have read the journal's policy and the authors of this manuscript have the following competing interests: RTJ, JDT, SAW, MJT, AH and MPH are non-paid members of the MacroDA consortium. RTJ, CSL, YRF, RS, EE, XL, and JCP were employees of Anacor. The other authors have declared that no competing interests exist.

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children and causes chronic diarrhea in AIDS patients, but the only approved treatment is ineffective in malnourished children and immunocompromised people. We here use a drug repositioning strategy and identify a promising anticryptosporidial drug candidate. Screening a library of benzoxaboroles comprised of analogs to four antiprotozoal chemical scaffolds under pre-clinical development for neglected tropical diseases for Cryptosporidium growth inhibitors identifies the 6-carboxamide benzoxaborole AN7973. AN7973 blocks intracellular parasite development, appears to be parasiticidal, and potently inhibits the two Cryptosporidium species most relevant to human health, C. parvum and C. hominis. It is efficacious in murine models of both acute and established infection, and in a neonatal dairy calf model of cryptosporidiosis. AN7973 also possesses favorable safety, stability, and PK parameters, and therefore, is an exciting drug candidate for treating cryptosporidiosis.

A series of pleuromutilins modified by introduction of a boron-containing heterocycle on C(14) of the polycyclic core are described. These analogs were found to be potent anti- Wolbachia antibiotics and, as such, may be useful in the treatment of filarial infections caused by Onchocerca volvulus, resulting in Onchocerciasis or river blindness, or Wuchereria bancrofti and Brugia malayi and related parasitic nematodes resulting in lymphatic filariasis. These two important neglected tropical diseases disproportionately impact patients in the developing world. The lead preclinical candidate compound containing 7-fluoro-6-oxybenzoxaborole (15, AN11251) was shown to have good in vitro anti- Wolbachia activity and physicochemical and pharmacokinetic properties providing high exposure in plasma. The lead was effective in reducing the Wolbachia load in filarial worms following oral administration to mice.

Recent development of benzoxaborole-based chemistry gave rise to a collection of compounds with great potential in targeting diverse infectious diseases, including human African Trypanosomiasis (HAT), a devastating neglected tropical disease. However, further medicinal development is largely restricted by a lack of insight into mechanism of action (MoA) in pathogenic kinetoplastids. We adopted a multidisciplinary approach, combining a high-throughput forward genetic screen with functional group focused chemical biological, structural biology and biochemical analyses, to tackle the complex MoAs of benzoxaboroles in Trypanosoma brucei. We describe an oxidative enzymatic pathway composed of host semicarbazide-sensitive amine oxidase and a trypanosomal aldehyde dehydrogenase TbALDH3. Two sequential reactions through this pathway serve as the key underlying mechanism for activating a series of 4-aminomethylphenoxy-benzoxaboroles as potent trypanocides; the methylamine parental compounds as pro-drugs are transformed first into intermediate aldehyde metabolites, and further into the carboxylate metabolites as effective forms. Moreover, comparative biochemical and crystallographic analyses elucidated the catalytic specificity of TbALDH3 towards the benzaldehyde benzoxaborole metabolites as xenogeneic substrates. Overall, this work proposes a novel drug activation mechanism dependent on both host and parasite metabolism of primary amine containing molecules, which contributes a new perspective to our understanding of the benzoxaborole MoA, and could be further exploited to improve the therapeutic index of antimicrobial compounds.

Novel l-valinate amide benzoxaboroles and analogues were designed and synthesized for a structure-activity-relationship (SAR) investigation to optimize the growth inhibitory activity against Trypanosoma congolense (T. congolense) and Trypanosoma vivax (T. vivax) parasites. The study identified 4-fluorobenzyl (1-hydroxy-7-methyl-1,3-dihydrobenzo[c][1,2]oxaborole-6-carbonyl)-l-valinate (5, AN11736), which showed IC 50 values of 0.15 nM against T. congolense and 1.3 nM against T. vivax, and demonstrated 100% efficacy with a single dose of 10 mg/kg against both T. congolense and T. vivax in mouse models of infection (IP dosing) and in the target animal, cattle, dosed intramuscularly. AN11736 has been advanced to early development studies., (Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Carboxamide pyrazinyloxy benzoxaboroles were investigated with the goal to identify a molecule with satisfactory antimalarial activity, physicochemical properties, pharmacokinetic profile, in vivo efficacy, and safety profile. This optimization effort discovered 46, which met our target candidate profile. Compound 46 had excellent activity against cultured Plasmodium falciparum, and in vivo against P. falciparum and P. berghei in infected mice. It exhibited good PK properties in mice, rats, and dogs. It was highly active against the other 11 P. falciparum strains, which are mostly resistant to chloroquine and pyrimethamine. The rapid parasite in vitro reduction and in vivo parasite clearance profile of 46 were similar to those of artemisinin and chloroquine, two rapid-acting antimalarials. It was nongenotoxic in an Ames assay, an in vitro micronucleus assay, and an in vivo rat micronucleus assay when dosed orally up to 2000 mg/kg. The combined properties of this novel benzoxaborole support its progression to preclinical development.

Benzoxaboroles are effective against bacterial, fungal and protozoan pathogens. We report potent activity of the benzoxaborole AN3661 against Plasmodium falciparum laboratory-adapted strains (mean IC 50 32 nM), Ugandan field isolates (mean ex vivo IC 50 64 nM), and murine P. berghei and P. falciparum infections (day 4 ED 90 0.34 and 0.57 mg kg -1 , respectively). Multiple P. falciparum lines selected in vitro for resistance to AN3661 harboured point mutations in pfcpsf3, which encodes a homologue of mammalian cleavage and polyadenylation specificity factor subunit 3 (CPSF-73 or CPSF3). CRISPR-Cas9-mediated introduction of pfcpsf3 mutations into parental lines recapitulated AN3661 resistance. PfCPSF3 homology models placed these mutations in the active site, where AN3661 is predicted to bind. Transcripts for three trophozoite-expressed genes were lost in AN3661-treated trophozoites, which was not observed in parasites selected or engineered for AN3661 resistance. Our results identify the pre-mRNA processing factor PfCPSF3 as a promising antimalarial drug target.

Toxoplasma gondii is an important food and waterborne pathogen causing toxoplasmosis, a potentially severe disease in immunocompromised or congenitally infected humans. Available therapeutic agents are limited by suboptimal efficacy and frequent side effects that can lead to treatment discontinuation. Here we report that the benzoxaborole AN3661 had potent in vitro activity against T. gondii Parasites selected to be resistant to AN3661 had mutations in TgCPSF3 , which encodes a homologue of cleavage and polyadenylation specificity factor subunit 3 (CPSF-73 or CPSF3), an endonuclease involved in mRNA processing in eukaryotes. Point mutations in TgCPSF3 introduced into wild-type parasites using the CRISPR/Cas9 system recapitulated the resistance phenotype. Importantly, mice infected with T. gondii and treated orally with AN3661 did not develop any apparent illness, while untreated controls had lethal infections. Therefore, Tg CPSF3 is a promising novel target of T. gondii that provides an opportunity for the development of anti-parasitic drugs., (© 2017 The Authors. Published under the terms of the CC BY 4.0 license.)

The apicomplexan parasites Cryptosporidium and Toxoplasma are serious threats to human health. Cryptosporidiosis is a severe diarrheal disease in malnourished children and immunocompromised individuals, with the only FDA-approved drug treatment currently being nitazoxanide. The existing therapies for toxoplasmosis, an important pathology in immunocompromised individuals and pregnant women, also have serious limitations. With the aim of developing alternative therapeutic options to address these health problems, we tested a number of benzoxaboroles, boron-containing compounds shown to be active against various infectious agents, for inhibition of the growth of Cryptosporidium parasites in mammalian cells. A 3-aminomethyl benzoxaborole, AN6426, with activity in the micromolar range and with activity comparable to that of nitazoxanide, was identified and further characterized using biophysical measurements of affinity and crystal structures of complexes with the editing domain of Cryptosporidium leucyl-tRNA synthetase (LeuRS). The same compound was shown to be active against Toxoplasma parasites, with the activity being enhanced in the presence of norvaline, an amino acid that can be mischarged by LeuRS. Our observations are consistent with AN6426 inhibiting protein synthesis in both Cryptosporidium and Toxoplasma by forming a covalent adduct with tRNA(Leu) in the LeuRS editing active site and suggest that further exploitation of the benzoxaborole scaffold is a valid strategy to develop novel, much needed antiparasitic agents., (Copyright © 2016 Palencia et al.)

There is a need for new antimalarials, ideally with novel mechanisms of action. Benzoxaboroles have been shown to be active against bacteria, fungi, and trypanosomes. Therefore, we investigated the antimalarial activity and mechanism of action of 3-aminomethyl benzoxaboroles against Plasmodium falciparum Two 3-aminomethyl compounds, AN6426 and AN8432, demonstrated good potency against cultured multidrug-resistant (W2 strain) P. falciparum (50% inhibitory concentration [IC50] of 310 nM and 490 nM, respectively) and efficacy against murine Plasmodium berghei infection when administered orally once daily for 4 days (90% effective dose [ED90], 7.4 and 16.2 mg/kg of body weight, respectively). To characterize mechanisms of action, we selected parasites with decreased drug sensitivity by culturing with stepwise increases in concentration of AN6426. Resistant clones were characterized by whole-genome sequencing. Three generations of resistant parasites had polymorphisms in the predicted editing domain of the gene encoding a P. falciparum leucyl-tRNA synthetase (LeuRS; PF3D7_0622800) and in another gene (PF3D7_1218100), which encodes a protein of unknown function. Solution of the structure of the P. falciparum LeuRS editing domain suggested key roles for mutated residues in LeuRS editing. Short incubations with AN6426 and AN8432, unlike artemisinin, caused dose-dependent inhibition of [(14)C]leucine incorporation by cultured wild-type, but not resistant, parasites. The growth of resistant, but not wild-type, parasites was impaired in the presence of the unnatural amino acid norvaline, consistent with a loss of LeuRS editing activity in resistant parasites. In summary, the benzoxaboroles AN6426 and AN8432 offer effective antimalarial activity and act, at least in part, against a novel target, the editing domain of P. falciparum LeuRS., (Copyright © 2016, American Society for Microbiology. All Rights Reserved.)

A series of 6-hetaryloxy benzoxaborole compounds was designed and synthesized for a structure-activity relationship (SAR) investigation to assess the changes in antimalarial activity which result from 6-aryloxy structural variation, substituent modification on the pyrazine ring, and optimization of the side chain ester group. This SAR study discovered highly potent 6-(2-(alkoxycarbonyl)pyrazinyl-5-oxy)-1,3-dihydro-1-hydroxy-2,1-benzoxaboroles (9, 27-34) with IC50s = 0.2-22 nM against cultured Plasmodium falciparum W2 and 3D7 strains. Compound 9 also demonstrated excellent in vivo efficacy against P. berghei in infected mice (ED90 = 7.0 mg/kg).

Structure-activity relationships of 6-(benzoylamino)benzoxaborole analogs were investigated for the inhibition of TNF-α, IL-1β, and IL-6 from lipopolysaccharide stimulated peripheral blood mononuclear cells. Compound 1q showed potent activity against all three cytokines with IC50 values between 0.19 and 0.50μM, inhibited LPS-induced TNF-α and IL-6 elevation in mice and improved collagen-induced arthritis in mice. Compound 1q (AN4161) is considered to be a promising lead for novel anti-inflammatory agent with an excellent pharmacokinetic profile., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A series of novel 6-(aminomethylphenoxy)benzoxaborole analogs was synthesized for the investigation of the structure-activity relationship of the inhibition of TNF-alpha, IL-1beta, and IL-6, from lipopolysaccharide stimulated peripheral blood mononuclear cells. Compounds 9d and 9e showed potent activity against all three cytokines with IC50 values between 33 and 83nM. Chloro substituted analog 9e (AN3485) is considered to be a promising lead for novel anti-inflammatory agent with a favorable pharmacokinetic profile., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Gram-negative bacteria cause approximately 70% of the infections in intensive care units. A growing number of bacterial isolates responsible for these infections are resistant to currently available antibiotics and to many in development. Most agents under development are modifications of existing drug classes, which only partially overcome existing resistance mechanisms. Therefore, new classes of Gram-negative antibacterials with truly novel modes of action are needed to circumvent these existing resistance mechanisms. We have previously identified a new a way to inhibit an aminoacyl-tRNA synthetase, leucyl-tRNA synthetase (LeuRS), in fungi via the oxaborole tRNA trapping (OBORT) mechanism. Herein, we show how we have modified the OBORT mechanism using a structure-guided approach to develop a new boron-based antibiotic class, the aminomethylbenzoxaboroles, which inhibit bacterial leucyl-tRNA synthetase and have activity against Gram-negative bacteria by largely evading the main efflux mechanisms in Escherichia coli and Pseudomonas aeruginosa. The lead analogue, AN3365, is active against Gram-negative bacteria, including Enterobacteriaceae bearing NDM-1 and KPC carbapenemases, as well as P. aeruginosa. This novel boron-based antibacterial, AN3365, has good mouse pharmacokinetics and was efficacious against E. coli and P. aeruginosa in murine thigh infection models, which suggest that this novel class of antibacterials has the potential to address this unmet medical need.

Pro-inflammatory cytokines play a critical role in the development of autoimmune and inflammatory diseases. Targeting the cytokine environment has proven efficient for averting inflammation. In this study, we reported that 6-[4-(aminomethyl)-2-chlorophenoxyl]benzo[c][1,2]oxaborol-1(3H)-ol (AN3485), a benzoxaborole analog, inhibited TLR2-, TLR3-, TLR4-, and TLR5-mediated TNF-α, IL-1β, and IL-6 release from human PBMCs and isolated monocytes with IC(50) values ranging from 18 to 580 nM, and the inhibition was mediated at the transcriptional level. Topical administration of AN3485 significantly reduced PMA-induced contact dermatitis and oxazolone-induced delayed-type hypersensitivity in mice, indicating its capability of penetrating skin and potential topical application in skin inflammation. Oral administration of AN3485 showed dose-dependent suppression of LPS-induced TNF-α and IL-6 production in mice with an ED(90) of 30 mg/kg. Oral AN3485, 35 mg/kg, twice a day, suppressed collagen-induced arthritis in mice over a 20-day period. The potent anti-inflammatory activity in in vitro and in vivo disease models makes AN3485 an attractive therapeutic lead for a variety of cutaneous and systemic inflammatory diseases.

We have used boron-based molecules to create novel, competitive, reversible inhibitors of phosphodiesterase 4 (PDE4). The co-crystal structure reveals a binding configuration which is unique compared to classical catechol PDE4 inhibitors, with boron binding to the activated water in the bimetal center. These phenoxybenzoxaboroles can be optimized to generate submicromolar potency enzyme inhibitors, which inhibit TNF-α, IL-2, IFN-γ, IL-5 and IL-10 activities in vitro and show safety and efficacy for topical treatment of human psoriasis. They provide a valuable new route for creating novel potent anti-PDE4 inhibitors., (Copyright © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

A series of new boron-containing benzoxaborole compounds was designed and synthesized for a continuing structure-activity relationship (SAR) investigation to assess the antimalarial activity changes derived from side-chain structural variation, substituent modification on the benzene ring and removal of boron from five-membered oxaborole ring. This SAR study demonstrated that boron is required for the antimalarial activity, and discovered that three fluoro-substituted 7-(2-carboxyethyl)-1,3-dihydro-1-hydroxy-2,1-benzoxaboroles (9, 14 and 20) have excellent potencies (IC(50) 0.026-0.209 μM) against Plasmodium falciparum., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

A series of boron-containing benzoxaborole compounds was designed and synthesized for a structure-activity relationship investigation surrounding 7-(HOOCCH(2)CH(2))-1,3-dihydro-1-hydroxy-2,1-benzoxaborole (1) with the goal of discovering a new antimalarial treatment. Compound 1 demonstrates the best potency (IC(50)=26nM) against Plasmodium falciparum and has good drug-like properties, with low molecular weight (206.00), low ClogP (0.86) and high water solubility (750μg/mL at pH 7)., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The hypocretin (Hcrt; also known as orexin) system has been implicated in arousal state regulation and energy metabolism. We hypothesize that age-related sleep problems can result from dysfunction of this system and thus measured messenger RNA (mRNA) levels of preprohcrt in the hypothalamus, and hcrt receptor 1 (hcrtr1) and hcrt receptor 2 (hcrtr2) in eight brain regions of 3, 12, 18 and 24 months old C57BL/6 mice. Expression of preprohcrt and the colocalized prodynorphin did not change with age. Whereas an age-related change in hcrtr1 mRNA expression was observed only in the hippocampus, hcrtr2 mRNA levels declined in the hippocampus, thalamus, pons, and medulla; these reductions ranged from 33 to 44%. Declining trends (P < 0.1) in hcrtr2 mRNA levels were also observed in the cortex, basal forebrain and hypothalamus. These results are consistent with the hypothesis that an age-related deterioration occurs in the Hcrt system that may contribute to age-related sleep disorders., (Copyright 2002 Elsevier Science Ireland Ltd.)

Using GeneChips, basal and lipopolysaccharide (LPS)-induced gene expression was examined in the hippocampus of 3-, 12-, 18- and 24-month-old male C57BL/6 mice to identify genes whose altered expression could influence hippocampal function in advanced age. Gene elements that changed with age were selected with a t-statistic and specific expression patterns were confirmed with real-time quantitative PCR. Basal expression of 128 gene elements clearly changed with age in the hippocampus. Fourteen gene elements showed increased expression with age and these increases were validated after LPS stimulation. Major histocompatibility complex (MHC) TL region and thymic shared antigen (TSA-1) gene expression increased, suggesting T cell activation in the hippocampus with age. Cytokine (interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha) and chemokine (macrophage chemotactic protein-1) expression increased sharply in 24-month-old mice. These findings are in contrast to a decrease in the peripheral immune response, documented by decreased T cell proliferation and decreased ratios of naive to memory T cells. Age-related increases in inflammatory potential in the brain may contribute to neurodegenerative diseases of the aged.

The increased mortality observed when human immunodeficiency virus (HIV)-infected individuals are treated with clarithromycin (CLA) as prophylaxis for disseminated infection with organisms of the Mycobacterium avium complex (MAC) suggests that CLA might possess immunosuppressive activities. To test this possibility, we assessed the immunological response of BALB/c mice following subchronic (28 days) oral administration of CLA alone or in combination with zidovudine (ZDV). Because normal hematopoiesis is needed to maintain the immune system, we also examined the effect of these drugs given individually or in combination on several hematological parameters. The major effect of administration of 500 mg/kg CLA was a marked decrease in the lymphocyte/neutrophil ratio, and the only evidence of hematotoxicity in mice treated with 240 mg/kg ZDV alone was mild macrocytic anemia. However, treatment with a combination of CLA and ZDV resulted in severe hematotoxicity, evidenced by a significant (p < 0.01) decrease in the number of circulating erythrocytes, neutrophils, and lymphocytes and a 67% drop in splenic cellularity (p < 0.01). Treatment with CLA or ZDV alone or both drugs in combination had no effect on lymphocyte function, determined by measuring the ex vivo proliferative activity of splenocytes in response to alloantigens or a B cell mitogen, lipopolysaccharide (LPS). However, because of the cellular depletion in the spleen, overall immune responses in this organ decreased significantly (p < 0.05) in mice treated with CLA plus ZDV. These data suggest that interactions between CLA and ZDV warrant further evaluation because these drugs are given in combination to persons with advanced HIV infection.

Pyrimethamine (Pyr) is commonly used for treatment of toxoplasmic encephalitis in AIDS patients; however, in two clinical studies, an increased number of deaths were observed when Pyr was coadministered with zidovudine (ZDV). The BALB/c mouse was chosen as a model to study the mechanism underlying the unexpected toxicity from coadministration of these drugs. Daily administration by oral gavage of 60 mg/kg Pyr and 240 mg/kg ZDV resulted in 100% lethality after 30 days. These dose levels produced no effect when the drugs were given individually for the same period. Administration of combinations of Pyr and ZDV resulted in macrocytic anemia and leukopenia with synergistic decreases in lymphocyte and neutrophil numbers. To examine the mechanism of this hematotoxicity at the cellular level, mouse bone marrow colony-forming unit (mCFU) assays were employed. A combination of ZDV with various concentrations of Pyr resulted in synergistic decreases in numbers of erythroid and granulocyte-macrophage precursors (mCFU-E and mCFU-GM). mCFU-GM precursors appeared more sensitive than erythroid precursors to combinations of Pyr and ZDV. Incorporation of (14)C-ZDV into cellular DNA was increased in a dose-dependent manner in the presence of increasing concentrations of Pyr in the mCFU-GM assay. This suggested that inhibition of dihydrofolate reductase by Pyr and accompanying inhibition of dTTP synthesis allows preferential incorporation of ZDV into DNA, with resulting strand breakage and cell death. (14)C-ZDV incorporation was also observed when human GM cultures were analyzed, however, incorporation was less and required higher concentrations of Pyr., ((c) 2002 Elsevier Science (USA).)

We investigated the immunohematoxicities of the antiparasitic drug dapsone (DDS) and the antiretroviral drug zidovudine (ZDV, AZT) given alone or in combination in BALB/c mice. DDS is used for prophylaxis and treatment of Pneumocystis carinii infection in AIDS patients. We examined the impact of concurrent administration of these drugs on the immune and hematopoietic systems because DDS causes hematotoxicity and ZDV therapy results in bone marrow toxicity. Daily oral administration of DDS at 25 and 50 mg/kg for 28 days caused a slight anemia, marked methemoglobinemia, reticulocytosis, and a moderate leukopenia (P < 0.01 for all parameters) but had no discernible effect on platelet count. In DDS-treated mice, the proliferative response of splenic T cells to concanavalin A was > or = 35% higher than that manifested by splenocytes from vehicle-treated control mice. ZDV at 240 and 480 mg/kg was not immunosuppressive but caused low-grade macrocytic anemia, thrombocytosis, and neutropenia; these effects were drug dose-dependent and statistically significant (P < 0.01). Concurrent administration of DDS and ZDV augmented the severity of ZDV-mediated macrocytic anemia, and 7 of 12 (58%) mice did not survive treatment with the high doses of DDS and ZDV (50 and 480 mg/kg, respectively). On the other hand, co-administration of ZDV mitigated DDS-induced methemoglobinemia and the DDS-associated elevation in lymphoproliferative response. These data suggest interaction between DDS and ZDV in mice and indicate a need for caution in using DDS as long-term therapy in AIDS patients receiving ZDV.

Toxoplasmic encephalitis (TE) is a life-threatening disease of immunocompromised individuals and has increased in prevalence as a consequence of AIDS. TE has been modeled in inbred mice, with CBA/Ca mice being susceptible and BALB/c mice resistant to the development of TE. To better understand the innate mechanisms in the brain that play a role in resistance to TE, nitric oxide (NO)-dependent and NO-independent mechanisms were examined in microglia from BALB/c and CBA/Ca mice and correlated with the ability of these cells to inhibit Toxoplasma gondii replication. These parameters were measured 48 h after stimulation with lipopolysaccharide (LPS) gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), or combinations of these inducers in T. gondii-infected microglia isolated from newborn mice. CBA/Ca microglia consistently produced less NO than did BALB/c microglia after stimulation with LPS or with IFN-gamma plus TNF-alpha, and they inhibited T. gondii replication significantly less than did BALB/c microglia. Cells of both strains treated with IFN-gamma alone significantly inhibited uracil incorporation by T. gondii, and N(G)-monomethyl-L-arginine (NMMA) treatment did not reverse this effect. In cells treated with IFN-gamma in combination with other inducers, NMMA treatment resulted in only partial recovery of T. gondii replication. This IFN-gamma-dependent inhibition of replication was not due to generation of reactive oxygen species or to increased tryptophan degradation. These data suggest that NO production and an IFN-gamma-dependent mechanism contribute to the inhibition of T. gondii replication after in vitro stimulation with IFN-gamma plus TNF-alpha or with LPS. Differences in NO production but not in IFN-gamma-dependent inhibition of T. gondii replication were observed between CBA/Ca and BALB/c microglia.

Trimethoprim-sulfamethoxazole (TMP-SMX), commonly used for prophylaxis of Pneumocystis carinii pneumonia (PCP) in AIDS patients, often produces a high incidence of treatment-limiting reactions. We investigated the effect of oral administration of TMP-SMX alone or in combination with the antiretroviral drug zidovudine (ZDV) on hematopoiesis and cellular immunity in BALB/c mice. Daily treatment for 28 days with TMP-SMX (160:800 mg/kg) had no effect on hematopoiesis or the ex vivo proliferative response of splenic T lymphocytes to allogeneic tumor cells (EL-4) or to concanavalin A (ConA), or that of splenic B cells to lipopolysaccharide (LPS). ZDV at 240 mg/kg/day was not immunosuppressive but caused a mild macrocytic anemia. Combined treatment produced severe pancytopenia, a significant drop in splenic cellularity, and a 61% decrease in the percentage of splenic macrophages. The percentage of splenic CD3+ lymphocytes increased 150% in the TMP-SMX + ZDV group, but the ratios of T-cell subsets and the frequency of B cells remained unchanged. Combined drug treatment did not impair the proliferative response of B cells to LPS or that of T cells to EL-4 cells. In concert with the reduction in the percentage of macrophages, the proliferative response of T lymphocytes to ConA decreased significantly. Optimal ConA-induced T-cell proliferation requires the participation of accessory cells (AC) (e.g., macrophages); EL-4 cells are able to function as AC. These data indicate that ZDV synergizes with TMP-SMX, causing severe hematotoxicity and suppressing AC-dependent immune function, and suggest that this therapeutic regimen may contribute to the immune deterioration in AIDS patients.

B7-1 is a co-stimulatory molecule that provides a second signal for T-cell activation. Several studies have demonstrated that vaccination with a vector containing genes encoding B7-1 and an antigen appears to be efficacious at promoting immune responsiveness to the antigen. To evaluate the safety of such a protocol and determine the effect of the B7-1 vector on immune responsiveness, female C57BL/6 mice were administered Wyeth wild-type vaccinia virus (V-WT) or V-WT containing the gene for B7-1 (rV-B7-1) as a single s. c. injection or 3 monthly s.c. injections. Immunologic parameters were evaluated in half of the mice and general toxicity in the other half. Immunologic end points included determination of splenic lymphocyte phenotypes, mitogen-induced T- and B-cell proliferation, T-cell proliferation in response to alloantigens, cell-mediated cytotoxicity (CMC), natural killer cell activity and serum anti-nuclear antibody (ANA) titers. No significant signs of general toxicity were noted. The primary immunologic effect was an increase in the ability of spleen cells to lyse allogeneic targets and to proliferate in response to allogeneic stimulation. Numbers of splenic CD8(+) cells were also increased. These effects were more pronounced after 3 vaccinations than after a single vaccination. Minimal differences in ANA were observed between mice immunized with V-WT and rV-B7-1. In addition, no serum antibodies against B7-1 were detected in any mice. The data suggest that vaccination with rV-B7-1 augments CMC with minimal toxicity., (Copyright 2000 Wiley-Liss, Inc.)

Increased mortality has been observed when HIV-infected patients were treated with pyrimethamine (Pyr) as prophylaxis for toxoplasmic encephalitis, suggesting that Pyr might possess immunosuppressive activity. To analyze this in an animal model, immune function was assessed in BALB/c mice using a battery of in vivo and ex vivo assays and an in vivo model of host resistance to Listeria monocytogenes infection. Treatment for 30 days with 60 mg/kg Pyr decreased circulating white blood cell and lymphocyte counts but not neutrophil, red blood cell, or platelet counts or hemoglobin levels. Splenic B cell percentages and lipopolysaccharide-induced B cell proliferation decreased significantly after treatment with 60 mg/kg Pyr, as did levels of anti-keyhole limpet hemocyanin (KLH) IgM in serum 7 days after immunization with KLH. Anti-KLH IgG levels 14 days after immunization were not affected. Percentages of splenic T cells and macrophages and T cell proliferation in the presence of concanavalin A or allogeneic cells were not decreased by Pyr treatment. An ex vivo assay of T-cell-mediated cytotoxicity was also unaffected. When host resistance to L. monocytogenes infection was assessed, dramatic increases in mortality were observed in Pyr-treated compared to control mice. Increased numbers of L. monocytogenes organisms were observed in liver and spleen of Pyr-treated mice, compared to controls. The reduction in Listeria resistance, which is T cell mediated, contrasts with the fact that no significant changes in T-cell-mediated immunity were observed. It is possible that Pyr affects parameters of innate immunity, which were not monitored in this study.

Murine resistance to development of toxoplasmic encephalitis (TE) has recently been mapped to the D region of the major histocompatibility complex (H-2). Since the gene for tumor necrosis factor alpha (TNF-alpha) is located 5' of the D region and TNF-alpha has been implicated as playing a role in neurological diseases, we were interested in determining the relationship of TNF-alpha production to TE resistance. We have demonstrated that resistance to TE in inbred mice can be correlated with specific restriction fragment length polymorphisms and microsatellite variants in the TNF-alpha gene. Mice that are susceptible to TE express elevated levels of TNF-alpha mRNA in brain tissue 6 wk after infection with the ME49 strain of Toxoplasma gondii. Resistant mice and all mice that are uninfected show no detectable TNF-alpha mRNA expression in brain tissue. Differences in the TNF-alpha gene between susceptible and resistant mice have been localized to the first intron, the promoter, and the 3' end of the TNF-alpha gene. These data implicate differences in regulation of TNF-alpha production in brain tissue as contributing to differences in susceptibility to development of TE.

We have assessed tumor necrosis factor-alpha (TNF-alpha) production and its autocrine effects on activation in two murine macrophage cell lines which have distinct responses to the activation stimuli interferon-gamma (IFN-gamma) and bacterial lipopolysaccharide (LPS), and compared these responses to those observed in thioglycollate-elicited peritoneal macrophages. IFN-gamma induced TNF-alpha production in RAW 264.7 cells and this induction was regulated at the transcriptional level. IFN-gamma did not stimulate TNF-alpha production in either WEHI-3 cells or peritoneal macrophages, although MHC class II antigen expression was induced. LPS stimulated TNF-alpha production in the RAW 264.7 cell line and peritoneal macrophages; however, no TNF-alpha was detected in WEHI-3 cells activated with LPS. We also assessed the ability of endogenous TNF-alpha to serve as an autocrine regulator of two aspects of IFN-gamma-mediated macrophage activation, namely, induction of antibody-independent tumoricidal activity and induction of MHC class II antigen expression. These studies revealed that TNF-alpha could act synergistically or antagonistically with IFN-gamma in the regulation of these two functions, depending on both the macrophage population used and the function assessed. The results of our experiments suggest that the mechanism of induction of TNF-alpha production by IFN-gamma or LPS, and the ultimate autocrine contribution of such TNF-alpha to a given activation response, is dependent on the activated macrophage target population under analysis. The WEHI-3 and RAW 264.7 cell lines provide a model system for comparative exploration of the mechanistic basis of this differential regulation.

In this report, we have demonstrated that IFN-gamma and TNF-alpha increase expression of both the I-A and I-E region gene products on the surface of the myelomonocytic cell line WEHI-3, and that they mediate this increase via an increase in A alpha transcription. Constructs containing 5' deletion mutations of the A alpha promoter attached to the bacterial chloramphenicol acetyl transferase gene were used to delineate the minimum 5' flanking sequences required for promoter activity, and for inducibility by IFN-gamma and TNF-alpha. Approximately 115 bp of 5' sequences are required for minimum induction by IFN-gamma or TNF-alpha when the cytokines are present separately. This includes the three conserved promoter elements, the X, Y, and H boxes. Nested linker-scanner mutations demonstrated that additional regions were also critical for optimal induction by IFN-gamma or TNF-alpha. These include the kappa B-like enhancer and a TNF-alpha-specific sequence that we have tentatively called the T box. The T box sequence was also found in the promoter regions of the human HLA-DQ alpha and rat RT1.B alpha genes. Although the entire T box sequence element was not found in the other mouse class II genes, all class II alpha genes contained the SV40 core enhancer element in the regions included by the T box. Mouse class II beta genes appear to contain neither the T box nor the core enhancer element in this region, suggesting differential regulation of class II alpha and beta genes by TNF-alpha.

In BALB/c mice, the injection of pristane resulted in a severe decrease in splenic T and B cell proliferative responses to mitogens and in a depression of natural killer (NK) activity. The effects of T and B cells, which persisted for at least 5 mo, were mediated by different mechanisms. T cell responsiveness to PHA dropped significantly below control levels 1 wk after the first of three monthly pristane injections, whereas B cell proliferation in response to LPS did not decrease until 4 wk after the first injection. The removal of plastic-adherent suppressor cells completely restored T cell proliferative capacity, but had no effect on B cells. NK activity against YAC-1 tumor targets was reduced 1 mo after the first pristane injection and remained depressed for at least 3 mo. This depression was not mediated by plastic-adherent suppressor cells. Spleen cell NK activity from pristane-treated mice could not be augmented by the interferon inducer Poly I:C to the same extent as that of control mice. This suggests an effect of pristane on either pre-NK cells or on cells that regulate NK activity.

Surface configurations are vessels fabricated from tubing and plate, films deposited on the surface of vessels, and beads confined in vessels. The average association constant between thrombin and sites on commercial poly(methyl methacrylate) surface (Lucite) is near 4 X 10(8) liters/mole at 22 degrees C, pH 7.0, and ionic strength 0.15. Depending on Lucite composition, average adsorption U, in molecules/cm2 of apparent solution-surface interface, ranges from 0.7 to 8.8 X 10(11). Analysis based on the assumptions that solution dimensions are preserved, adsorption is random, and surface rearrangement is negligible indicates a paucity of surface sites. Plasma albumin competes with thrombin for surface sites. Attempts to detect, by thrombin adsorption, the presence of free sites at 4.5 X 10-9M albumin or the displacement of bound albumin indicate an albumin-site association contrast greater than 1.6 X 10(9). Cross-linked poly(methyl acrylate) bead surface has U less than 5 X 10(10). In contrast to acrylic resins are silicone gum, polypropylene, and polyisobutylene, for which U ranges from 15 to 20 X 10(11). Analysis as above indicates that sites are of frequent occurrence. Material composition suggests that thrombin can interact with nonpolar groups. Further characteristics of low-energy surfaces are that progressive surface denaturation is small and there is a large variance between nominally equivalent configurations.

We demonstrated a tightly coordinated timing in the appearance of mRNA for the four class II (Ia) MHC chains, A alpha, A beta, E alpha, and E beta, and the Ia-associated invariant chain in a murine macrophage cell line after the addition of immune interferon (IFN-gamma) or of IFN-gamma-containing supernatants from Con A-stimulated spleen cells. The marked increase in mRNA levels for these molecules at approximately 8 hr after IFN-gamma addition contrasts sharply with the earlier, more gradual kinetics observed for class I (H-2) and beta 2-microglobulin mRNA. The difference in kinetics of IFN-gamma induction of class I and class II mRNA suggests differential regulation of the expression of Ia and H-2 antigens. The long lag period preceding detection of Ia mRNA raises the possibility that IFN-gamma may not directly mediate the increase in mRNA expression, but may act through an additional cellular intermediate.