OBJECTIVES:

Although intestinal dysbiosis is well established in Crohn's disease (CD), little is known about the microbial metabolic activity of CD patients. In this study, we compared the metabolite patterns of the CD patients with profiles from healthy controls (HCs) and correlated them to disease activity and bacterial composition. In addition, the influence of the prebiotic oligofructose-enriched inulin (OF-IN) on the CD metabolites profile was evaluated.

METHODS:

Sixty-seven inactive and moderately active CD patients were included in a double-blinded randomized placebo controlled trial (RCT). Patients consumed either 10 g OF-IN or 10 g placebo twice per day for 4 weeks. They collected a fecal sample before the start of the study (baseline) and after the treatment period. In addition, fecal samples were obtained from 40 HCs. The metabolite profile was assessed using gas chromatography–mass spectrometry.

RESULTS:

The number of fecal metabolites was significantly higher in HCs than in CD patients (P<0.001). Forty compounds differed between CD patients and HCs. When correlating the metabolite levels to disease activity, significantly lower levels of butyrate, pentanoate, hexanoate, heptanoate, and p-cresol were found in active patients as compared with HCs. In the RCT, no significant changes in the metabolite pattern were found in patients randomized to placebo. In patients receiving OF-IN (per protocol; n=21), the relative levels of acetaldehyde (P=0.0008) and butyrate (P=0.0011) were significantly increased as compared with baseline.

CONCLUSIONS:

We identified medium chain fatty acids and p-cresol as differentiating metabolites toward CD disease status and as compared with HCs. In addition, OF-IN intake primarily increased the carbohydrate fermentation metabolites butyrate and acetaldehyde.

A screening of conformationally constrained aromatic amino acids as base cores for the preparation of new NK1 receptor antagonists resulted in the discovery of three new NK1 receptor antagonists, 19 [Ac-Aba-Gly-NH-3′,5′-(CF3)2-Bn], 20 [Ac-Aba-Gly-NMe-3′,5′-(CF3)2-Bn] and 23 [Ac-Tic-NMe-3′,5′-(CF3)2-Bn], which were able to counteract the agonist effect of substance P, the endogenous ligand of NK1R. The most active NK1 antagonist of the series, 20 [Ac-Aba-Gly-NMe-3′,5′-(CF3)2-Bn], was then used in the design of a novel, potent chimeric opioid agonist-NK1 receptor antagonist, 35 [Dmt-D-Arg-Aba-Gly-NMe-3′,5′-(CF3)2-Bn], which combines the N-terminus of the established Dmt1-DALDA agonist opioid pharmacophore (H-Dmt-D-Arg-Phe-Lys-NH2) and 20, the NK1R ligand. The opioid component of the chimeric compound 35, i.e. Dmt-D-Arg-Aba-Gly-NH2 36, also proved to be an extremely potent and balanced μ- and δ opioid receptor agonist with subnanomolar binding and in vitro functional activity.

Background

An important limiting factor in the development of centrally acting pharmaceuticals is the blood-brain barrier (BBB). Transport of therapeutic peptides through this highly protective physiological barrier remains a challenge for peptide drug delivery into the central nervous system (CNS). Because the most common strategy to treat moderate to severe pain consists of the activation of opioid receptors in the brain, the development of active opioid peptide analogues as potential analgesics requires compounds with a high resistance to enzymatic degradation and an ability to cross the BBB.

Results

Herein we report that tetrapeptide analogues of the type H-Dmt1-Xxx2-Yyy3-Gly4-NH2 are transported into the brain after intravenous and subcutaneous administration and are able to activate the μ- and δ opioid receptors more efficiently and over longer periods of time than morphine. Using the hot water tail flick test as the animal model for antinociception, a comparison in potency is presented between a side chain conformationally constrained analogue containing the benzazepine ring (BVD03, Yyy3: Aba), and a "ring opened" analogue (BVD02, Yyy3: Phe). The results show that in addition to the increased lipophilicity through amide bond N-methylation, the conformational constraint introduced at the level of the Phe3 side chain causes a prolonged antinociception. Further replacement of NMe-D-Ala2 by D-Arg2 in the tetrapeptide sequence led to an improved potency as demonstrated by a higher and maintained antinociception for AN81 (Xxx2: D-Arg) vs. BVD03 (Xxx2: NMe-D-Ala). A daily injection of the studied opioid ligands over a time period of 5 days did however result in a substantial decrease in antinociception on the fifth day of the experiment. The compact opioid agonist - NK1 antagonist hybrid SBCHM01 could not circumvent opioid induced tolerance.

Conclusions

We demonstrated that the introduction of a conformational constraint has an important impact on opioid receptor activation and subsequent antinociception in vivo. Further amino acid substitution allowed to identify AN81 as an opioid ligand able to access the CNS and induce antinociception at very low doses (0.1 mg/kg) over a time period up to 7 hours. However, tolerance became apparent after repetitive i.v. administration of the investigated tetrapeptides. This side effect was also observed with the dual opioid agonist-NK1 receptor antagonist SBCHM01.

CD8 T cell clonal expansions (TCE) have been observed in elderly, healthy individuals as well in old mice, and have been associated with the ageing process. Both chronic latent and non-persistent viral infections have been proposed to drive the development of distinct non-functional and functional TCE respectively. Biases in TCR Vβ repertoire diversity are also recurrently observed in patients that have undergone strong immune challenge, and are preferentially observed in the CD8 compartment. Healthy adults can also exhibit CD8 T cells with strong alterations of their CDR3 length distribution. Surprisingly, no specific investigations have been conducted to analyze the CD8 T cell repertoire in normal adults, to determine if such alterations in TCR Vβ repertoire share the features of TCE. In this study, we characterized the phenotype and function of the CD8 population in healthy individuals of 25–52 years of age. All but one of the EBV-positive HLA-B8 healthy volunteers that were studied were CMV-negative. Using a specific unsupervised statistical method, we identified Vβ families with altered CDR3 length distribution and increased TCR Vβ/HPRT transcript ratios in all individuals tested. The increase in TCR Vβ/HPRT transcript ratio was more frequently associated with an increase in the percentage of the corresponding Vβ+ T cells than with an absence of modification of their percentage. However, in contrast with the previously described TCE, these CD8+ T cells were not preferentially found in the memory CD8 subset, they exhibited normal effector functions (cytokine secretion and cytotoxic molecule expression) and they were not reactive to a pool of EBV/CMV/Flu virus peptides. Taken together, the combined analysis of transcripts and proteins of the TCR Vβ repertoire led to the identification of different types of CD8+ T cell clone expansion or contraction in healthy individuals, a situation that appears more complex than previously described in aged individuals.

The relevance of biological materials and processes to computing—aliasbioputing—has been explored for decades. These materials include DNA, RNA and proteins, while the processes include transcription, translation, signal transduction and regulation. Recently, the use of bacteria themselves as living computers has been explored but this use generally falls within the classical paradigm of computing. Computer scientists, however, have a variety of problems to which they seek solutions, while microbiologists are having new insights into the problems bacteria are solving and how they are solving them. Here, we envisage that bacteria might be used for new sorts of computing. These could be based on the capacity of bacteria to grow, move and adapt to a myriad different fickle environments both as individuals and as populations of bacteria plus bacteriophage. New principles might be based on the way that bacteria explore phenotype space via hyperstructure dynamics and the fundamental nature of the cell cycle. This computing might even extend to developing a high level language appropriate to using populations of bacteria and bacteriophage. Here, we offer a speculative tour of what we term bactoputing, namely the use of the natural behaviour of bacteria for calculating.

The dimerization and trimerization of the Dmt-Tic, Dmt-Aia and Dmt-Aba pharmacophores provided multiple ligands which were evaluated in vitro for opioid receptor binding and functional activity. Whereas the Tic- and Aba multimers proved to be dual and balanced δ/μ antagonists, as determined by the functional [S35]GTPγS binding assay, the dimerization of potent Aia-based ‘parent’ ligands unexpectedly resulted in substantial less efficient receptor binding and non-active dimeric compounds.

Objective

The non-invasive in vivo visualization of activated platelets using a target-specific MRI contrast agent to identify thrombi, hallmarks of vulnerable/high-risk atherosclerotic plaques.

Methods

Inflammatory thrombi were induced in mice via topical application of arachidonic acid on the carotid. Thrombus formation was imaged with intravital fluorescence microscopy and molecular MRI. To accomplish the latter, a paramagnetic contrast agent (P975) that targets the glycoprotein αIIbβ3 expressed on activated platelets was investigated. The specificity of P975 for activated platelets was studied in vitro. In vivo, high spatial-resolution MRI was performed at baseline and longitudinally over 2 hours after injecting P975 or a non-specific agent. The contralateral carotid, a sham surgery group and a competitive inhibition experiment served as controls.

Results

P975 showed a good affinity for activated platelets with an IC50 value of 2.6 µM. In thrombosed animals, P975 produced an immediate and sustained increase in MRI signal whereas none of the control groups revealed any significant increase in MRI signal 2 hours post-injection. Importantly, the competitive inhibition experiment with a αIIbβ3 antagonist suppressed the MRI signal enhancement, which is indicative for the specificity of P975 for the activated platelets.

Conclusion

P975 allowed in vivo target-specific noninvasive MR imaging of activated platelets.

Background

The clinical treatment of various types of pain relies upon the use of opioid analgesics. However most of them produce, in addition to the analgesic effect, several side effects such as the development of dependence and addiction as well as sedation, dysphoria, and constipation. One solution to these problems are chimeric compounds in which the opioid pharmacophore is hybridized with another type of compound to incease antinociceptive effects. Neurotensin-induced antinociception is not mediated through the opioid system. Therefore, hybridizing neurotensin with opioid elements may result in a potent synergistic antinociceptor.

Results

Using the known structure-activity relationships of neurotensin we have synthesized a new chimeric opioid-neurotensin compound PK20 which is characterized by a very strong antinociceptive potency. The observation that the opioid antagonist naltrexone did not completely reverse the antinociceptive effect, indicates the partial involvement of the nonopioid component in PK20 in the produced analgesia.

Conclusions

The opioid-neurotensin hybrid analogue PK20, in which opioid and neurotensin pharmacophores overlap partially, expresses high antinociceptive tail-flick effects after central as well as peripheral applications.

Thirty-nine new thiazolide/thiadiazolide compounds were compared with the nitrothiazole nitazoxanide for activity against Cryptosporidium parvum development in HCT-8 cells. Twenty-seven agents exerted ≥90% inhibition. Agents with a lower 50% inhibitory concentration (IC50) than nitazoxanide were either NO2 or halogen 5 substituted on the thiazole moiety. Other 5 substitutions such as methyl, C3H7, C6H11, H, SO2CH3, and SCH3 negatively impacted activity. Five-substituted deacetylated analogues exhibited higher IC50s than their acetylated counterparts. Halogeno-thiazolide/thiadiazolides may provide valuable nitro-free alternatives to nitazoxanide.

Cryptosporidium spp. are a cause of self-limited diarrhea in immunocompetent hosts. In immunocompetent rats, Cryptosporidium parvum infection induced digestive hypersensitivity, a key pathophysiological factor in functional digestive disorders such as irritable bowel syndrome (IBS). In such a rat model, we sought to document whether jejunal hypersensitivity depends on C. parvum isolate and is associated with a mast cell accumulation. Five-day-old rats were orally administered 105 oocysts of either Nouzilly (NoI) or Iowa (IoI) C. parvum isolate. NoI-infected rats exhibited the lowest food intake on days 7 and 14 postinfection (p.i.). On day 7 p.i., small intestine villus atrophy, crypt hyperplasia, and inflammatory cell infiltration were prominent in NoI-infected rats, with higher numbers of Cryptosporidium forms than in IoI-infected rats. Compared to uninfected control rats, jejunal intraepithelial lymphocytes (IELs) were increased only in NoI-infected rats on day 14 p.i. On day 50 p.i., jejunal hypersensitivity to distension was found only in NoI-infected rats; this hypersensitivity is associated with activated mast cell accumulation. The number of mast cells in the jejunal lamina propria was increased from day 36 p.i. in NoI-infected rats and only at day 120 p.i. in IoI-infected rats. Our data suggest that both the severity of infection (weight loss, reduced food intake, villus atrophy, and IEL accumulation) and the onset of a jejunal hypersensitivity after infection in association with an activated mast cell accumulation are isolate dependent and related to NoI infection. This cryptosporidiosis rat model is a relevant model for the study of underlying mechanisms of postinfectious IBS-like symptoms.

Replacement of the constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) in the opioid Dmt-Tic-Gly-NH-Bn scaffold by the 4-amino-1,2,4,5-tetrahydro-indolo[2,3-c]azepin-3-one (Aia) and 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba) scaffolds has led to the discovery of novel potent μ-selective agonists (Structures 5 and 12) as well as potent and selective δ-opioid receptor antagonists (Structures 9 and 15). Both stereochemistry and N-terminal N,N-dimethylation proved to be crucial factors for opioid receptor selectivity and functional bioactivity in the investigated small peptidomimetic templates. In addition to the in vitro pharmacological evaluation, automated docking models of Dmt-Tic and Dmt-Aba analogues were constructed in order to rationalize the observed structure-activity data.

In search of new selective antagonists and/or agonists for the human melanocortin receptor subtypes hMC1R to hMC5R to elucidate the specific biological roles of each GPCR, we modified the structures of the superagonist MT-II (Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH2) and the hMC3R/hMC4R antagonist SHU9119 (Ac-Nle-c[Asp-His-D-Nal(2′)-Arg-Trp-Lys]-NH2) by replacing the His-D-Phe and His-D-Nal(2′) fragments in MT-II and SHU9119, respectively, with Aba-Xxx (4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one-Xxx) dipeptidomimetics (Xxx = D-Phe/pCl-D-Phe/D-Nal(2′)). Employment of the Aba mimetic yielded novel selective high affinity hMC3R and hMC3R/hMC5R antagonists.

To retrospectively evaluate the incidence of tumour cell contamination of peripheral blood stem cell (PBSC) collections and to correlate these data with the clinical outcome after high-dose chemotherapy (HDCT) with stem cell rescue in patients with a high-risk Ewing tumour. Peripheral blood stem cell collections obtained from 171 patients were analysed. Tumour contamination was assessed by reverse transcriptase–polymerase chain reaction (RT–PCR). The files of 88 patients who underwent HDCT followed by PBSC reinfusion were reviewed in detail, and their outcome compared to the PBSC RT–PCR results. Seven of 88 PBSC collections (8%) contained tumour cells as detected by RT–PCR. Peripheral blood stem cells were collected after a median of five cycles of chemotherapy. No clinical factor predictive of tumour cell contamination of PBSC harvest could be identified. Event-free survival (EFS) and overall survival (OS) of the whole study population were 45.3 % and 51.8 % at 3 years from the date of the graft, respectively. Forty-five patients relapsed with a median time of 15 months after graft, only four of whom had tumour cell contamination of the PBSC harvest. Tumour cell contamination of PBSC collection is rare and does not seem to be associated with a significantly poorer EFS or OS in this high-risk population.

In 5-day-old immunocompetent Sprague-Dawley rats infected with either 102 or 105 Cryptosporidium parvum oocysts, transient infection resulted 120 days later in increased cardiovascular depressor response to jejunal distension and jejunal myeloperoxidase activity (P < 0.05). Nitazoxanide treatment normalized jejunal sensitivity (P < 0.001) but not myeloperoxidase levels (P > 0.05). Data warrant further evaluation of the role of early cryptosporidiosis in the development of chronic inflammatory gut conditions.

Several gene sequences of parasitic protozoa belonging to protein kinase gene families and epidermal growth factor (EGF)-like peptides, which act via binding to receptor tyrosine kinases of the EGF receptor (EGFR) family, appear to mediate host-protozoan interactions. As a clue to EGFR protein tyrosine kinase (PTK) mediation and a novel approach for identifying anticoccidial agents, activities against Sarcocystis neurona, Neospora caninum, and Cryptosporidium parvum grown in BM and HCT-8 cell cultures of 52 EGFR PTK inhibitor isoflavone analogs (dihydroxyisoflavone and trihydroxydeoxybenzoine derivatives) were investigated. Their cytotoxicities against host cells were either absent, mild, or moderate by a nitroblue tetrazolium test. At concentrations ranging from 5 to 10 μg/ml, 20 and 5 analogs, including RM-6427 and RM-6428, exhibited an in vitro inhibitory effect of ≥95% against at least one parasite or against all three, respectively. In immunosuppressed Cryptosporidium parvum-infected Mongolian gerbils orally treated with either 200 or 400 mg of agent RM-6427/kg of body weight/day for 8 days, fecal microscopic oocyst shedding was abolished in 6/10 animals (P of <0.001 versus untreated controls) and mean shedding was reduced by 90.5% (P of <0.0001) and 92.0% (P of <0.0001), respectively, higher levels of inhibition than after nitazoxanide (200 mg/kg/day for 8 days) or paromomycin (100 mg/kg/day for 8 days) treatment (55.0%, P of <0.001, and 17.5%, P of >0.05, respectively). After RM-6427 therapy (200 mg/kg/day for 8 days), the reduction in the ratio of animals with intracellular parasites was nearly significant in ileum (P = 0.067) and more marked in the biliary tract (P < 0.0013) than after nitazoxanide or paromomycin treatment (0.05 < P < 0.004). RM-6428 treatment at a regimen of 400 mg/kg/day for 12 days inhibited oocyst shedding, measured using flow cytometry from day 4 (P < 0.05) to day 12 (P < 0.02) of therapy, when 2/15 animals had no shedding (P < 0.0001) and 11/15 were free of gut and/or biliary tract parasites (P < 0.01). No mucosal alteration was microscopically observed for treated or untreated infected gerbils. To our knowledge, this report is the first to suggest that the isoflavone class of agents has the potential for anticoccidial therapy.

One-month-old dexamethasone-immunosuppressed Mongolian gerbils were challenged with 1 oocyst to 2 × 105 oocysts from two isolates genotyped as Cryptosporidium hominis and C. parvum (genotype 2), respectively. A similar dose-dependent gut infection was obtained, and the initial genotype maintained for 21 to 22 days. The data suggest that immunosuppressed gerbils provide a reliable rodent model of persistent C. hominis infection.

The importance of waterborne transmission of Cryptosporidium parvum to humans has been highlighted by recent outbreaks of cryptosporidiosis. The first step in a survey of contaminated water currently consists of counting C. parvum oocysts. Data suggest that an accurate risk evaluation should include a determination of viability and infectivity of counted oocysts in water. In this study, oocyst infectivity was addressed by using a suckling mouse model. Four-day-old NMRI (Naval Medical Research Institute) mice were inoculated per os with 1 to 1,000 oocysts in saline. Seven days later, the number of oocysts present in the entire small intestine was counted by flow cytometry using a fluorescent, oocyst-specific monoclonal antibody. The number of intestinal oocysts was directly related to the number of inoculated oocysts. For each dose group, infectivity of oocysts, expressed as the percentage of infected animals, was 100% for challenge doses between 25 and 1,000 oocysts and about 70% for doses ranging from 1 to 10 oocysts/animal. Immunofluorescent flow cytometry was useful in enhancing the detection sensitivity in the highly susceptible NMRI suckling mouse model and so was determined to be suitable for the evaluation of maximal infectivity risk.

The susceptibilities of three bovine and two human Babesia divergens isolates to antimicrobial agents were evaluated in vitro by a tritiated hypoxanthine incorporation assay. The MICs at which 50% of isolates are inhibited (MIC50s) for mefloquine (chlorhydrate), chloroquine (sulfate), quinine (chlorhydrate), clindamycin (phosphate), pentamidine (isethionate), phenamidine (isethionate) plus oxomemazine (chlorhydrate), lincomycin (chlorhydrate monohydrate), and imidocarb (dipropionate) were determined. Except for imidocarb, the MIC50s observed for the different isolates were close. Imidocarb and the combination of phenamidine plus oxomemazine exhibited the highest in vitro activity, while antimalarial agents such as mefloquine, choroquine, and quinine were inactive. Other drugs had intermediate activities. The data support further in vitro evaluation of antimicrobial agents active against B. divergens for the improvement of therapeutic strategies.

Patients with tienilic acid hepatitis exhibit autoantibodies that recognize unalkylated cytochrome P450 2C9 in humans but recognize 2C11 in rats. Our aim was to determine whether the immune reaction is also directed against neoantigens. Rats were treated with tienilic acid and hepatocytes were isolated. Immunoprecipitation, immunoblotting, and flow cytometry experiments were performed with an anti-tienilic acid or an anti-cytochrome P450 2C11 antibody. Cytochrome P450 2C11 was the main microsomal or plasma membrane protein that was alkylated by tienilic acid. Inhibitors of vesicular transport decreased flow cytometric recognition of both unalkylated and tienilic acid-alkylated cytochrome P450 2C11 on the plasma membrane of cultured hepatocytes. Tienilic acid hepatitis sera that were preadsorbed on microsomes from untreated rats (to remove autoantibodies), poorly recognized untreated hepatocytes in flow cytometry experiments, but better recognized tienilic acid-treated hepatocytes. This recognition was decreased by adsorption with tienilic acid or by preexposure to the anti-tienilic acid or the anti-cytochrome P450 2C11 antibody. We conclude that cytochrome P450 2C11 is alkylated by tienilic acid and follows a vesicular route to the plasma membrane. Tienilic acid hepatitis sera contain antibodies against this tienilic acid adduct, in addition to the previously described anticytochrome P450 autoantibodies.

An immunosuppressed rat model was used to investigate the anti-Cryptosporidium parvum activity of sinefungin. In infected animals, oral sinefungin therapy resulted in a dose-related suppression of oocyst shedding, which correlated with oocyst disappearance from ileal sections. When administered prior to or on the day of oocyst challenge, sinefungin successfully prevented infection. These data suggest that sinefungin could be considered as a candidate molecule in the treatment of human cryptosporidiosis, considered to be the most significant enteric opportunistic infection in AIDS.

Serum antibody response to plasmodial antigens was investigated in 97 Thai patients with Plasmodium falciparum malaria. No difference in immunoglobulin G (IgG) antibody levels was detected between groups without or with cerebral manifestations of malaria (n = 40). In patients with the most severe form of the disease, i.e., those who died despite adequate therapy (n = 12), antibody detected in the immunofluorescent-antibody test was found at lower levels than in those who recovered (geometric means: IgG = 1/420 versus 1/3,800; IgM = 1/15 versus 1/70); similarly, precipitating malarial antibodies were present in only 1 of these 12 patients, while they were detectable in 65 of the remaining 85 patients (76.5%). In contrast, anticytomegalovirus antibody levels were similar in the different groups of patients. Results show that depression of antibody response may extend to antiplasmodial responses during severe malaria. The link between fatality and a low level of antibody production suggests that an appropriate immune response to malarial antigens may be required to achieve recovery with drug treatment and provides a new direction for malaria therapy research.

During Plasmodium falciparum malaria, a wide spectrum of parasite-encoded blood-stage proteins is presented to the immune system of the host. To explore their multiple interactions with T cells from donors who have had no previous exposure to the parasite, whole schizont extract was used in vitro. Both CD4+ and CD8+ lymphocytes from all individuals tested were stimulated to proliferate. The responses were dependent on the presence of accessory cells and were only partially replaced by recombinant interleukin-1. Responses were inhibited by monoclonal antibodies to CD3, the alpha beta-chain T-cell receptor, or CD4 molecules but not to CD2. P. falciparum schizont extract-specific T-cell clones were generated and maintained by using sole stimulation by P. falciparum extract with autologous accessory cells or recombinant interleukin-2. Monoclonal antibodies to CD3 (or the alpha beta-chain T-cell receptor) blocked cloned T-cell responses to the schizont extract, and although the responses of the majority of the CD4+ or CD8+ T-cell clones were restricted by autologous accessory cells and inhibited by monoclonal antibodies to either CD4 or CD8, other clones responded to P. falciparum in the absence of accessory cells and were not regulated by the same monoclonal antibodies. The last category of clones consisted of autoreactive T cells. These data suggest that at the first contact with P. falciparum, requirements are met for significant T-cell stimulation.

Effective treatment for Cryptosporidium infection in immunocompromised patients has yet to be found. We report a rodent model of persistent Cryptosporidium infection. Sprague-Dawley rats were injected subcutaneously twice a week for 8 weeks with 25 mg of hydrocortisone acetate. Fed a regular low-protein diet for 9 weeks, they were challenged once with 10(5) calf Cryptosporidium oocysts 5 weeks after the start of the hydrocortisone acetate regimen. Oocyst shedding was evaluated in feces daily by using a carbolfuchsin-staining method. Rats shed oocysts from days 2 to 9 after ingestion and developed a persistent infection for more than 38 days. Excretion was lower after subsequent parasite challenges, suggesting that a degree of protection developed progressively. The results suggest that this experimental model provides a procedure for screening candidate therapeutic agents.

Antibodies against Trichomonas vaginalis were detected in serum samples from 98 patients by three immunological assays. A good correlation was observed between the enzyme-linked immunosorbent assay and the immunofluorescence method, whereas it was found that the enzyme-linked immunosorbent assay correlated better with the current or past detection of organisms than did other serological methods (immunofluorescence and hemagglutination). Similar results were obtained with whole trichomonads and two T. vaginalis soluble antigenic preparations, which suggests that immunodominant moieties shared by several T. vaginalis strains were detected. The level of antibodies of the immunoglobulin A class was higher in patients with past records of trichomoniasis, but less significantly so than the total antitrichomonal antibody level. Antibodies of the four immunoglobulin G subclasses were detected. Immunoglobulin G1 antibody values were higher in female than male patients.