Multifaceted roles for STAT3 in gammaherpesvirus latency revealed through in vivo B cell knockout models

Cancers associated with the oncogenic gammaherpesviruses, Epstein-Barr virus and Kaposi sarcoma herpesvirus, are notable for their constitutive activation of the transcription factor signal transducer and activator of transcription 3 (STAT3). To better understand the role of STAT3 during gammaherpesvirus latency and the B cell response to infection, we used the model pathogen murine gammaherpesvirus 68 (MHV68). Genetic deletion of STAT3 in B cells of CD19cre/+Stat3f/f mice reduced peak MHV68 latency approximately sevenfold. However, infected CD19cre/+Stat3f/f mice exhibited disordered germinal centers and heightened virus-specific CD8 T cell responses compared to wild-type (WT) littermates. To circumvent the systemic immune alterations observed in the B cell-STAT3 knockout mice and more directly evaluate intrinsic roles for STAT3, we generated mixed bone marrow chimeric mice consisting of WT and STAT3 knockout B cells. We discovered a dramatic reduction in latency in STAT3 knockout B cells compared to their WT B cell counterparts in the same lymphoid organ. RNA sequencing of sorted germinal center B cells revealed that MHV68 infection shifts the gene signature toward proliferation and away from type I and type II IFN responses. Loss of STAT3 largely reversed the virus-driven transcriptional shift without impacting the viral gene expression program. STAT3 promoted B cell processes of the germinal center, including IL-21-stimulated downregulation of surface CD23 on B cells infected with MHV68 or EBV. Together, our data provide mechanistic insights into the role of STAT3 as a latency determinant in B cells for oncogenic gammaherpesviruses.IMPORTANCEThere are no directed therapies to the latency program of the human gammaherpesviruses, Epstein-Barr virus and Kaposi sarcoma herpesvirus. Activated host factor signal transducer and activator of transcription 3 (STAT3) is a hallmark of cancers caused by these viruses. We applied the murine gammaherpesvirus pathogen system to explore STAT3 function upon primary B cell infection in the host. Since STAT3 deletion in all CD19+ B cells of infected mice led to altered B and T cell responses, we generated chimeric mice with both normal and STAT3-deleted B cells. B cells lacking STAT3 failed to support virus latency compared to normal B cells from the same infected animal. Loss of STAT3 impaired B cell proliferation and differentiation and led to a striking upregulation of interferon-stimulated genes. These findings expand our understanding of STAT3-dependent processes that are key to its function as a pro-viral latency determinant for oncogenic gammaherpesviruses in B cells and may provide novel therapeutic targets.

Intrinsic p53 Activation Restricts Gammaherpesvirus-Driven Germinal Center B Cell Expansion during Latency Establishment

Gammaherpesviruses (GHV) are DNA tumor viruses that establish lifelong latent infections in lymphocytes. For viruses such as Epstein-Barr virus (EBV) and murine gammaherpesvirus 68 (MHV68), this is accomplished through a viral gene-expression program that promotes cellular proliferation and differentiation, especially of germinal center (GC) B cells. Intrinsic host mechanisms that control virus-driven cellular expansion are incompletely defined. Using a small-animal model of GHV pathogenesis, we demonstrate in vivo that tumor suppressor p53 is activated specifically in B cells that are latently infected by MHV68. In the absence of p53, the early expansion of MHV68 latency was greatly increased, especially in GC B cells, a cell-type whose proliferation was conversely restricted by p53. We identify the B cell-specific latency gene M2, a viral promoter of GC B cell differentiation, as a viral protein sufficient to elicit a p53-dependent anti-proliferative response caused by Src-family kinase activation. We further demonstrate that EBV-encoded latent membrane protein 1 (LMP1) similarly triggers a p53 response in primary B cells. Our data highlight a model in which GHV latency gene-expression programs that promote B cell proliferation and differentiation to facilitate viral colonization of the host trigger aberrant cellular proliferation that is controlled by p53.

IMPORTANCE

Gammaherpesviruses cause lifelong infections of their hosts, commonly referred to as latency, that can lead to cancer. Latency establishment benefits from the functions of viral proteins that augment and amplify B cell activation, proliferation, and differentiation signals. In uninfected cells, off-schedule cellular differentiation would typically trigger anti-proliferative responses by effector proteins known as tumor suppressors. However, tumor suppressor responses to gammaherpesvirus manipulation of cellular processes remain understudied, especially those that occur during latency establishment in a living organism. Here we identify p53, a tumor suppressor commonly mutated in cancer, as a host factor that limits virus-driven B cell proliferation and differentiation, and thus, viral colonization of a host. We demonstrate that p53 activation occurs in response to viral latency proteins that induce B cell activation. This work informs a gap in our understanding of intrinsic cellular defense mechanisms that restrict lifelong GHV infection.

B cell-intrinsic STAT3-mediated support of latency and interferon suppression during murine gammaherpesvirus 68 infection revealed through an in vivo competition model

Cancers associated with the oncogenic gammaherpesviruses, Epstein-Barr virus and Kaposi sarcoma herpesvirus, are notable for their constitutive activation of the transcription factor STAT3. To better understand the role of STAT3 during gammaherpesvirus latency and immune control, we utilized murine gammaherpesvirus 68 (MHV68) infection. Genetic deletion of STAT3 in B cells of CD19cre/+Stat3f/f mice reduced peak latency approximately 7-fold. However, infected CD19cre/+Stat3f/f mice exhibited disordered germinal centers and heightened virus-specific CD8 T cell responses compared to WT littermates. To circumvent the systemic immune alterations observed in the B cell-STAT3 knockout mice and more directly evaluate intrinsic roles for STAT3, we generated mixed bone marrow chimeras consisting of WT and STAT3-knockout B cells. Using a competitive model of infection, we discovered a dramatic reduction in latency in STAT3-knockout B cells compared to their WT B cell counterparts in the same lymphoid organ. RNA sequencing of sorted germinal center B cells revealed that STAT3 promotes proliferation and B cell processes of the germinal center but does not directly regulate viral gene expression. Last, this analysis uncovered a STAT3-dependent role for dampening type I IFN responses in newly infected B cells. Together, our data provide mechanistic insight into the role of STAT3 as a latency determinant in B cells for oncogenic gammaherpesviruses.

Pediatric SARS-CoV-2 Seroprevalence in Arkansas Over the First Year of the COVID-19 Pandemic

BACKGROUND

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) seroprevalence studies largely focus on adults, but little is known about spread in children. We determined SARS-CoV-2 seroprevalence in children and adolescents from Arkansas over the first year of the coronavirus disease of 2019 (COVID-19) pandemic.

METHODS

We tested remnant serum samples from children ages 1-18 years who visited Arkansas hospitals or clinics for non-COVID-19-related reasons from April 2020 through April 2021 for SARS-CoV-2 antibodies. We used univariable and multivariable regression models to determine the association between seropositivity and participant characteristics.

RESULTS

Among 2357 participants, seroprevalence rose from 7.9% in April/May 2020 (95% CI, 4.9-10.9) to 25.0% in April 2021 (95% CI, 21.5-28.5). Hispanic and black children had a higher association with antibody positivity than non-Hispanic and white children, respectively, in multiple sampling periods.

CONCLUSIONS

By spring 2021, most children in Arkansas were not infected with SARS-CoV-2. With the emergence of SARS-CoV-2 variants, recognition of long-term effects of COVID-19, and the lack of an authorized pediatric SARS-CoV-2 vaccine at the time, these results highlight the importance of including children in SARS-CoV-2 public health, clinical care, and research strategies.

Chronic anti-phencyclidine monoclonal antibody therapy decreases phencyclidine-induced in utero fetal mortality in pregnant rats

Illicit drug use during pregnancy is a serious social and public health problem inflicting an array of deleterious effects on both mother and offspring. We investigated the hypothesis that a murine anti-phencyclidine (PCP) monoclonal antibody (mAb6B5; K(D)=1.3 nM) can safely protect mother and fetus from PCP-induced adverse health effects in pregnant rats. Pregnant Sprague-Dawley rats (n=4-5) were intravenously administered bolus injections of PCP (1mg/kg) on multiple days during pregnancy. They were also chronically treated with anti-PCP mAb6B5 at 45 mg/kg as a PCP antagonist. This dose provided one mAb-PCP binding site for every four PCP molecules. Therapeutic and safety study endpoints included pregnancy outcome (litter size, number of live vs. dead pups), maternal hemodynamic status and locomotor activity. Maternal hemodynamic changes (i.e., blood pressure and heart rate) and locomotor activity were measured in dams from gestation days 6-21 (one day antepartum) using a radiotelemetry-tracking device with a femoral arterial pressure catheter. This mAb6B5 treatment regimen significantly (p=0.008) reduced the number of PCP-induced in utero fetal deaths (odds ratio=3.2; 95%CI 1.3 to 7.9) and significantly (p<0.05) reduced acute PCP-induced maternal locomotor effects in the second trimester. Maternal hemodynamic responses to PCP were not significantly affected by mAb6B5 treatment. In conclusion, these data suggest that anti-PCP mAb treatments administered during pregnancy can safely protect a mother and her fetus(es) from PCP-related morbidity and mortality even when the mAb dose is too low to significantly prevent other PCP-induced maternal pharmacological effects.

Interviewing witnesses: the effect of forced confabulation on event memory

After viewing a crime video, participants answered 16 answerable and 6 unanswerable questions. Those in the "voluntary guess" condition had a "don't know" response option; those in the "forced guess" condition did not. One week later the same questions were answered with a "don't know" option. In both experiments, information generated from forced confabulation was less likely remembered than information voluntarily self-generated. Further, when the same answer was given to an unanswerable question both times, the confidence expressed in the answer increased over time in both the forced and the voluntary guess conditions. Pressing eyewitnesses to answer questions, especially questions repeated thrice (Experiment 2), may not be an effective practice because it reliably increases intrusion errors but not correct recall.

Effects of anti-phencyclidine and anti-(+)-methamphetamine monoclonal antibodies alone and in combination on the discrimination of phencyclidine and (+)-methamphetamine by pigeons

RATIONALE

Drug-specific monoclonal antibodies against phencyclidine (PCP) and (+)-methamphetamine [(+)-METH] should bind to these drugs to block their discriminative stimulus effects.

OBJECTIVES

To determine if mouse monoclonal antibodies against PCP and (+)-METH can block the discriminative stimulus effects of the drugs in pigeons.

MATERIALS AND METHODS

Pigeons were trained to discriminate among intramuscular injections of saline, 1 mg/kg PCP, and 2 mg/kg (+)-METH. After responding stabilized, cumulative dose-response curves were obtained for PCP and (+)-METH. Doses of an anti-PCP antibody at 620 mg/kg (anti-PCP mAb6B5) with a K (D) of 1.3 nM for PCP and no measurable affinity for (+)-METH and 1,000 mg/kg doses of anti-(+)-METH antibody (anti-METH mAb6H7) with a K (D) of 41 nM for (+)-METH and no measurable affinity for PCP were subsequently administered, first alone and later in combination after which the dose-response curves were redetermined.

RESULTS

When the antibodies were given alone, the anti-PCP antibody blocked the discriminative stimulus effects of PCP, but not those of (+)-METH, and the anti-(+)-METH antibody blocked the discriminative stimulus effects of (+)-METH, but not those of PCP. The anti-PCP antibody shifted the PCP dose-response curve further to the right and for a longer time than the anti-(+)-METH antibody shifted the dose response curve for (+)-METH. When the anti-PCP and anti-(+)-METH antibodies were administered on the same day, the discriminative stimulus effects of both drugs were completely blocked 1 day after antibody administration.

CONCLUSIONS

These experiments demonstrate the high specificity of the antibodies for the drugs to which they bind and show that monoclonal antibodies can be combined to antagonize the effects of more than one drug.

Development of a liquid chromatography–tandem mass spectrometric method for the determination of methamphetamine and amphetamine using small volumes of rat serum

The aim of this paper was to develop LC/MS/MS methodology for the determination of methamphetamine (METH) and amphetamine (AMP) using low microliter volumes (20-150 microl) of rat serum and demonstrate the use of this method for the study of serum pharmacokinetics in the rat. The analytes were extracted from rat serum using solid-phase extraction followed by an isocratic separation on a narrow-bore Hypersil C(18) column. Lower limits of quantitation for METH and AMP were 0.3 ng/ml using positive ion electrospray tandem mass spectrometry. The accuracy of the method was within 20% of the actual values over a wide range of serum concentrations. The within-day and between-day precision was better than 20% (R.S.D.). Ion-suppression matrix effects on electrospray ionization were evaluated for extracted rat serum. The LC/MS/MS method was further validated by comparing serum concentrations of METH and AMP to serum concentrations previously determined using an LC/[ (3)H]-METH assay with radiochemical detection. Finally, the LC/MS/MS method was used to study the pharmacokinetics of METH and AMP after a 1mg/kg intravenous bolus dose of METH to female Sprague-Dawley rats.

Effects of murine-derived anti-methamphetamine monoclonal antibodies on (+)-methamphetamine self-administration in the rat

Two murine-derived anti-methamphetamine monoclonal antibodies were studied as potential pharmacokinetic antagonists of (+)-methamphetamine self-administration by rats. Intravenous administration of a 1 g/kg dose of the lower affinity [antibody equilibrium dissociation constant (K(d)) = 250 nM] monoclonal antibody (mAb) designated mAb6H8, 1 day before the start of several daily 2-h self-administration sessions produced effects that depended on the dose of (+)-methamphetamine. mAb6H8 increased the rate of self-administration of a unit dose of 0.06 mg/kg (+)-methamphetamine, had little effect on the rate of self-administration of a unit dose of 0.03 mg/kg (+)methamphetamine, and lowered the rate of self-administration of a unit dose of 0.01 mg/kg (+)-methamphetamine to a level similar to that after saline substitution. mAb-induced changes in rates of self-administration occurred very early in self-administration sessions and lasted for 3 to 7 days. Intravenous administration of a 1 or a 0.6 g/kg dose of a higher affinity (K(d) = 11 nM) mAb designated mAb6H4, 24 h before the first of several self-administration sessions, produced very similar effects to the lower affinity mAb, despite the more than 20-fold greater affinity for (+)-methamphetamine. It is proposed that these anti-methamphetamine antibodies bind some of the self-administered (+)-methamphetamine before it can penetrate into brain, thereby reducing the amount of free drug available to function as a reinforcer. Although neither of these mAb medications are optimal antibodies for treating (+)-methamphetamine abuse, the experiments demonstrate that anti-(+)-methamphetamine monoclonal antibodies can attenuate the self-administration of the drug and suggest the potential of using monoclonal antibodies as pharmacokinetic antagonists of (+)-methamphetamine.

Pharmacokinetic antagonism of (+)-methamphetamine discrimination by a low-affinity monoclonal anti-methamphetamine antibody

Animals were trained to discriminate 5 or 10 mg/kg cocaine (rats), or 3 mg/kg (+)-amphetamine (pigeons) from saline, after which dose-response curves were determined for (+)-methamphetamine and other drugs before and after administration of a (+)-methamphetamine-specific monoclonal antibody (K(D) =250 nM). In rats trained to discriminate 10 mg/kg cocaine from saline, intravenous (+)-methamphetamine was about three times more potent as a discriminative stimulus than intraperitoneal (+)-methamphetamine. Also in these rats, intraperitoneal (+)-methamphetamine and (+)-amphetamine were about equipotent as discriminative stimuli, and were about three times more potent than intraperitoneal cocaine. In pigeons trained to discriminate 3 mg/kg intramuscular (i.m.) (+)-amphetamine from saline, (+)-methamphetamine and (+)-amphetamine were nearly equipotent, while cocaine was slightly less potent. In rats trained to discriminate 5 or 10 mg/kg cocaine from saline, intravenous administration of 1 g/kg of the antibody shifted both intravenous and intraperitoneal dose-response curves for (+)-methamphetamine discrimination approximately threefold to the right at 1 or 4 days after administration of the antibody. In pigeons trained to discriminate 3 mg/kg intramuscular (+)-amphetamine from saline, a similar shift of the (+)-methamphetamine dose-response curve to the right also lasted for 4-7 days. However, the antibody did not affect the (+)-amphetamine dose-response curve (pigeons), or the cocaine (rats) dose-response curve. The data show that a low affinity anti-(+)-methamphetamine-specific antibody can produce a specific antagonism of an effect of (+)-methamphetamine that is closely associated with its abuse.

Intravenous (+)-methamphetamine causes complex dose-dependent physiologic changes in awake rats

Hemodynamic and temperature dose-response relationships were characterized in freely moving rats following i.v. (+)-methamphetamine administration to mimic the rapid onset of effects experienced by many human users. Rats received saline and (+)-methamphetamine in a repeated-measures, mixed-sequence design at 22+/-1 degrees C. Significantly greater blood pressure and heart rate elevations were observed after 1.0 and 3.0 mg/kg (+)-methamphetamine vs. 0.1 and 0.3 mg/kg. The time to peak hemodynamic values and the duration of effects were significantly greater after 3.0 mg/kg vs. the lower doses. The time to peak temperatures was significantly longer after 1.0 mg/kg vs. the lower doses. Following 3.0 mg/kg, all rats experienced temperature decreases before having elevated temperatures. The duration and magnitude of the delayed temperature elevations were significantly greater after 3.0 mg/kg vs. the lower doses. In conclusion, the (+)-methamphetamine-induced hemodynamic and temperature effects were not temporally synchronized, and the complex responses were not linearly related to dose.

Differential and region-specific activation of mitogen-activated protein kinases following chronic administration of phencyclidine in rat brain

We have previously demonstrated elevation of the extracellular signal-regulated kinase (ERK) pathway in the cerebellum from patients with schizophrenia, an illness that may involve dysfunction of the N-methyl-D-aspartate (NMDA) receptor. Since the NMDA antagonist, phencyclidine (PCP), produces schizophrenic-like symptoms in humans, and abnormal behavior in animals, we examined the effects of chronic PCP administration in time- and dose-dependent manner on ERK and two other members of mitogen-activated protein kinase family, c-Jun N-terminal protein kinase (JNK) and p38, in rat brain. Osmotic pumps for PCP (18 mg/kg/day) and saline (controls) were implanted subcutaneously in rats for three, 10, and 20 days. Using Western blot analysis, we found no change at three days, but a significant increase in the phosphorylation of ERK1, ERK2 and MEK in the cerebellum at 10- and 20-days of continuous PCP infusion. For the experiments involving various doses of PCP, rats were infused with PCP at concentrations of 2.5, 10, 18, or 25 mg/kg/day, or saline for 10 days. We observed a dose-dependent elevation in the phosphorylation of ERK1 and ERK2 only in the cerebellum but not in brainstem, frontal cortex or hippocampus. The activities of JNK and p38 were unchanged in all investigated brain regions including cerebellum. These results demonstrate that chronic infusion of PCP in rats produces a differential and brain region-specific activation of MAP kinases, suggesting a role for the ERK signaling pathway in PCP abuse and perhaps in schizophrenia.

Generation of anti-(+)methamphetamine antibodies is not impeded by (+)methamphetamine administration during active immunization of rats

The goal of these studies was to determine if chronic (+)methamphetamine ((+)METH) administration affects the production of anti-(+)METH antibodies during active immunization of rats. Active immunization for the treatment of chronic drug abuse has been proposed for drugs such as cocaine and nicotine. However, studies have not adequately addressed whether continual drug use during treatment would affect the development of an immune response. For the current studies, male Sprague-Dawley rats were immunized with either keyhole limpet hemocyanin (KLH; control group) or a (+)METH hapten ((+)METH with a six carbon spacer group at the para position of the ring structure)-KLH conjugate. The (+)METH-KLH animals were further divided into two groups. One group was immunized with no subsequent administration of (+)METH, while the other group was immunized and repeatedly challenged (twice a week throughout the study) with an i.p. dose of 3 mg/kg (+)METH. The results showed that the two groups of (+)METH-KLH immunized rats developed and maintained anti-(+)METH antibody titers. The anti-(+)METH immune responses of the two groups were not statistically different (P < 0.05) as measured by serum titers and the relative antibody affinities. These data suggest that repeated administration of (+)METH does not affect the generation of an anti-(+)METH antibody response in actively immunized rats.

The effect of rate of drug administration on the extent and time course of phencyclidine distribution in rat brain, testis, and serum

The goal of these studies was to examine the relationship between the rate of phencyclidine (PCP) administration and PCP tissue distribution. The time course of PCP distribution in serum, brain, and testis after rapid (i.v.) and slow (s.c.) administration was studied. Brain and serum PCP concentrations after an i.v. bolus dose (1 mg/kg at 900 microg/min) were highest at 30 s and decreased biphasically, with serum concentrations decreasing 30 times faster than brain concentrations during the early phase. Consequently, the brain-to-serum PCP concentration ratio increased from 8:1 at 30 s to 14:1 at 20 min before equilibrating at a ratio of 3:1 that remained constant from 1 to 8 h. In contrast, the testis-to-serum ratio increased slowly from 1:1 to 12:1 over 4 h, and then remained constant. In a separate group of animals, an s.c. infusion of PCP (18 mg/kg/day or 3.6 microg/min) produced a brain-to-serum ratio (6:1) that remained constant throughout the 96-h infusion. Testis-to-serum ratios increased from 4:1 at 1 h to 12:1 at 8 h and then remained constant for 96 h. Steady-state infusion of a pharmacologically inactive dose (2.5 mg/kg/day) produced a brain-to-serum ratio (3:1) that was significantly lower than the ratio (6:1) after infusion of the three pharmacologically active doses (10-25 mg/kg/day). The temporary high brain PCP concentrations and the dynamic disequilibrium between brain and serum concentrations after rapid i.v. administration could provide a better understanding of the preference of the human drug abuser for rapid rates (e.g., i.v. or smoking) of drug administration.

Disposition of methamphetamine and its metabolite amphetamine in brain and other tissues in rats after intravenous administration

These studies characterized the concentration-time profile of (+)-methamphetamine [(+)-METH] and its metabolite (+)-amphetamine [(+)-AMP] in the brain and five other tissues after (+)-METH administration. Male Sprague-Dawley rats received a pharmacologically active (+)-METH i.v. bolus dose (1.0 mg/kg) or a nonpharmacologically active s.c. infusion (20 h at 1.2 mg/kg/day). Tissues (n = 3 per time point) were collected for more than four elimination half-lives in the i.v. group, or at a single steady-state time point (20 h) in the s.c. group. Based on data from the area under the concentration-time curves after i.v. dosing, the rank order of (+)-METH tissue accumulation was kidney > spleen > brain > liver > heart > serum with terminal elimination half-life values ranging from 53 to 66 min. (+)-METH concentrations were highest at the first measured time point (2 min) in all tissues except the spleen, which peaked at 10 min. The brain-to-serum concentration ratio rose from 7:1 at 2 min to a peak of 13:1 at 20 min before equilibrating to a constant value of 8:1 at 2 h. Following s.c. (+)-METH dosing, the (+)-METH brain-to-serum concentration ratio was the same as the equilibrated ratio following i.v. dosing. (+)-AMP concentrations peaked at 20 min in all tissues before decaying with terminal elimination half-life values ranging from 68 to 75 min. Analysis of the area under the concentration-time curve molar amounts of (+)-AMP and (+)-METH showed that (+)-AMP accounted for approximately one-third of the drug tissue exposure over time. Thus, these data indicate the importance of both (+)-METH and (+)-AMP in pharmacological effects following i.v. (+)-METH administration.

Anti-phencyclidine monoclonal antibodies provide long-term reductions in brain phencyclidine concentrations during chronic phencyclidine administration in rats

These studies examined the hypothesis that a single large dose of monoclonal anti-phencyclidine (PCP) antibody could provide long-term reductions in brain PCP concentrations despite continuous PCP administration. PCP (18 mg/kg/day, s.c.) was infused to steady-state (24 h) and then a mole-equivalent dose of a short-acting anti-PCP antigen-binding fragment (Fab) or a long-acting anti-PCP IgG was administered i.v. The PCP infusion continued for up to 27 days, even though the binding capacity of the single dose of antibody used should have been saturated within the first day. At selected time points after antibody administration, brain, testis, and serum PCP concentrations were measured. Serum PCP concentrations rapidly increased approximately 100- and 300-fold after Fab or IgG administration, respectively. Based on the antibody-bound PCP concentrations in serum, the functional elimination half-life (t(1/2lambdaZ)) values for PCP-Fab and PCP-IgG complexes were 9.4 h and 15.4 days, respectively. Fab and IgG administration produced a complete removal of PCP from the brain within 15 min. Although brain PCP concentrations were significantly decreased for only 4 h in Fab-treated animals, IgG administration resulted in significant decreases in brain PCP concentrations lasting for at least 27 days. In contrast, testis PCP concentrations were not substantially affected by antibody administration, suggesting that redistribution of PCP from the testis is too slow to benefit from a limited dose of antibody. These results indicate that anti-PCP IgG can preferentially protect the brain for approximately 4 weeks after IgG administration, even when the antibody binding capacity should have been saturated with continuously administered PCP.

Spontaneous locomotor activity and pharmacokinetics of intravenous methamphetamine and its metabolite amphetamine in the rat

The purpose of these studies was to better understand the behavioral effects and pharmacokinetics of an i.v. bolus dose of (+)-methamphetamine [(+)-METH] in a rat model of (+)-METH abuse. We characterized the behavioral effects after increasing (+)-METH doses (0.1, 0.3, and 1.0 mg/kg) and the pharmacokinetics of (+)-METH (and its metabolite (+)-amphetamine [(+)-AMP)]) at the lowest and highest of these doses in adult male Sprague-Dawley rats. The doses and route of administration were selected to mimic aspects of human use on a dose/body weight basis. Although the 0.1 mg/kg dose did not cause statistically significant increases in locomotor activity compared with saline controls, the higher doses (0.3 and 1.0 mg/kg) caused statistically significant increases in locomotor activity (p <.05), which lasted for up to 3 h at the highest dose. After the 1.0 mg/kg dose, the volume of distribution at steady state was 9.0 liters/kg, the total clearance was 126 ml/min/kg, and the average distribution and elimination half-lives were 9.2 and 63.0 min, respectively. Because the pharmacokinetic values after the 0.1 mg/kg dose were not different from those after the 1.0 mg/kg dose, the pharmacokinetics of (+)-METH were considered to be independent of the dose over this 10-fold range. (+)-AMP serum concentrations after the 1.0 mg/kg dose peaked from 10 to 30 min, and exhibited a T(1/2lambdaz) of 98.5 min. The statistically longer T(1/2lambdaz) of (+)-AMP (p <.05) suggested that the (+)-AMP terminal elimination rate and not the (+)-AMP metabolic formation rate is the rate-limiting step in (+)-AMP elimination following i.v. (+)-METH dosing.

Sexual dimorphism in phencyclidine in vitro metabolism and pharmacokinetics in rats

Studies were conducted to determine the differences in phencyclidine (PCP) in vitro metabolism and pharmacokinetics in female and male Sprague-Dawley (SD) rats. Formation rates of five major PCP metabolites in liver microsomes were significantly higher (p <.05) in males compared with females in three different rat strains (SD, Fischer 344, and Dark Agouti). In addition, the formation rate for an irreversibly bound PCP metabolite in males was the second highest of the six metabolites measured in these studies. However, the liver microsomes from the females produced essentially no metabolite binding in any strain. To determine the in vivo consequences of these in vitro metabolism results, we determined PCP's pharmacokinetic profile in female SD rats after a pharmacologically active i.v. dose of PCP (1 mg/kg) and then compared these data with the pharmacokinetic profile in male SD rats. The value for PCP systemic (and nonrenal) clearance was more than 45% lower (p <.05) in female rats. In addition, the terminal elimination T(1/2) was significantly longer (p <.05) in the female rats (5.5 versus 3.4 h, respectively). Because the initial serum concentration, volume of distribution at steady state, and renal clearance were not significantly different between the sexes, the longer half-life was attributed directly to a decreased ability of females to metabolize the drug. Consequently, these pharmacokinetic data suggest pharmacological differences in PCP effects between female and male rats are due primarily to a decreased ability of female rats to metabolize the drug.

Pharmacokinetic mechanisms for obtaining high renal coelimination of phencyclidine and a monoclonal antiphencyclidine antigen-binding fragment of immunoglobulin G in the rat

Our purpose was to determine mechanisms and methods for significantly increasing the renal coelimination of phencyclidine (PCP) and an anti-PCP monoclonal antibody binding fragment (anti-PCP Fab). To accomplish this goal, we performed a series of experiments to examine the dose-dependence of Fab elimination, mechanisms for enhancing PCP and Fab urinary coelimination and the antigenicity of repeated Fab administration. The results showed that urinary elimination of PCP and anti-PCP Fab was linear over a 30-fold range of doses. Anti-PCP Fab serum pharmacokinetics were best described using bi- or tri-exponential curves with a terminal elimination half-life of approximately 8 hr. Nevertheless, under all experimental conditions the early, nonterminal phase(s) were responsible for the majority (60%) of intact Fab elimination, with only 40% of the Fab eliminated during the terminal phase. These data suggest that the early rapid decline in Fab serum concentrations was primarily due to passive filtration and excretion of intact Fab, and not due to extravascular distribution as previously described. In comparison of methods for enhancing renal coelimination of Fab and PCP, systemic alkalinization produced a significant increase in Fab urinary elimination, with 69% of the Fab dose and 41% of the PCP dose recovered intact in the urine. Finally, in studies of the antigenicity of Fab, repeated administration of Fab produced no significant immune response or renal impairment. Overall, these experiments suggest that careful attention to the physiological status of the kidney during early time periods is essential for maximum coelimination of Fab and bound chemicals.

Crystal structure of monoclonal 6B5 Fab complexed with phencyclidine

The crystal structure of monoclonal antibody (mAb) 6B5 Fab fragment complexed with 1-(1-phenylcyclohexyl)piperidine (PCP or phencyclidine) was determined at 2.2-A resolution. 6B5 was originally produced from a mouse immunized with a phencyclidine analogue hapten 5-[N-(1'phenylcyclohexyl)amino]pentanoic acid conjugated to bovine serum albumin. This mAb was selected for further study because of its high affinity (Kd = 2 x 10(-9) M/liter) for PCP and usefulness in reversing PCP-induced central nervous system toxicity in laboratory animals. The dominant feature of the 6B5 Fab.PCP complex is the deep binding site and hydrophobic nature of the interaction. The ligand binding pocket of 6B5 Fab has numerous aromatic side chains, as compared with other known Fab structures. The most notable feature of the binding site is a Trp at position 97H (H-chain), and the side chain of this residue appears to act as a hydrophobic umbrella on the ligand in the antigen binding pocket. There are only two other known Fabs found with a Trp at the 97H position in complementarity determining region (CDR) H3, but they do not play a major role in the interaction with their respective antigens; in both Fab TE33 and R6.5 the Trp 97H side chain is positioned away from the bound antigen. Comparison of the CDR residues of 6B5 with other Fab structures with similar CDR sizes and amino acid compositions reveals a number of important patterns of residue substitutions that appear to be critical for specific PCP ligand interactions.

Pharmacodynamics of a monoclonal antiphencyclidine Fab with broad selectivity for phencyclidine-like drugs

The development of treatment strategies for drug intoxication has been hindered in part by the lack of clinically useful antagonists. Consequently, the major goal of these studies was to determine whether a monoclonal antibody Fab fragment (of IgG) could be used as an effective drug class-selective antagonist and to understand better the dose-response relationships for reversing CNS drug toxicity. Changes in drug-induced locomotor effects in a rat model were used to assess the ability of the antiphencyclidine (anti-PCP) Fab to reverse the behavioral effects of PCP and other potent arylcyclohexylamines. In experiments to determine the pharmacodynamics of Fabinduced antagonism of behavioral effects, the Fab completely reversed all PCP-induced locomotor effects in a Fab dose-dependent manner with a minimal effective dose of 0.18 mole-equivalents of Fab and an ED50 value of about one-third mole-equivalent. The anti-PCP Fab also completely reversed the locomotor effects induced by two other structurally related potent analogs of PCP: 1-[1-(2-thienyl)cyclohexyl]piperidine and N-ethyl-1-phenylcyclohexylamine. In addition, pharmacological and immunological selectivity was further tested by treatment of the behavioral effects induced by the structurally unrelated locomotor stimulant (+)methamphetamine. The antibody did not effectively reverse the effects of methamphetamine-induced locomotor activity. These results indicate that antibody-based medications can be developed to treat toxicity caused by classes of drugs as well as by individual drugs.

Exposure to acute stress induces brain interleukin-1beta protein in the rat

Peripheral immune stimulation such as that provided by lipopolysaccharide (LPS) has been reported to increase brain levels of IL-1beta mRNA, immunoreactivity, and bioactivity. Stressors produce many of the same neural and endocrine responses as those that follow LPS, but the impact of stressors on brain interleukin-1beta (IL-1beta) has not been systematically explored. An ELISA designed to detect IL-1beta was used to measure levels of IL-1beta protein in rat brain. Brain IL-1beta was explored after exposure to inescapable shock (IS; 100 1.6 mA tail shocks for 5 sec each) and LPS (1 mg/kg) as a positive control. Rats were killed either immediately or 2, 7, 24, or 48 hr after IS. Brains were dissected into hypothalamus, hippocampus, cerebellum, posterior cortex, and nucleus tractus solitarius regions. LPS produced widespread increases in brain IL-1beta, but IS did not. Adrenal glucocorticoids are known to suppress IL-1beta production in both the periphery and brain. Thus, it was possible that the stressor did provide stimulus input to the brain IL-1beta system(s), but that the production of IL-1beta protein was suppressed by the rapid and prolonged high levels of glucocorticoids produced by IS. To test this possibility rats were adrenalectomized or given sham surgery, with half of the adrenalectomized rats receiving corticosterone replacement to maintain basal corticosterone levels. IS produced large increases in brain IL-1beta protein in the adrenalectomized subjects 2 hr after stress, whether basal corticosterone levels had been maintained. Thus elimination of the stress-induced rise in corticosterone unmasked a robust and widespread increase in brain IL-1beta.

Stationary crystal diffraction with a monochromatic convergent X-ray source and application for macromolecular crystal data collection

A diffraction geometry utilizing convergent X-rays from a polycapillary optic incident on a stationary crystal is described. A mathematical simulation of the resulting diffraction pattern (in terms of spot shape, position and intensity) is presented along with preliminary experimental results recorded from a lysozyme crystal. The effective source coverage factor is introduced to bring the reflection intensities onto the same scale. The feasibility of its application to macromolecular crystal data collection is discussed.

Brain microsomal metabolism of phencyclidine in male and female rats

These studies examined the microsomal brain metabolism of phencyclidine (PCP) in male and female Sprague-Dawley rats. Several monohydroxylated metabolites of PCP were detected including cis- and trans-1-(1-phenyl-4-hydroxycyclohexyl)piperidine (c-PPC and t-PPC) and 1-(1-phenylcyclohexyl)-4-hydroxypiperidine (PCHP). The in vitro formation of these metabolites required NADPH and was inhibited by carbon monoxide. c-PPC was formed in the male and female brain microsomes at rates of 7.1 +/- 1.3 and 5.7 +/- 1.1 fmol/min per mg, respectively, while t-PPC was formed at rates of 16.2 +/- 3.3 and 16.5 +/- 4.2 fmol/min per mg. PCHP had the highest formation rate at 50.7 +/- 8.9 and 48.2 +/- 8.8 fmol/min per mg, respectively. Although previous studies with rat liver microsomes find higher levels of PCP metabolism in male rats and the formation of an irreversibly bound metabolite in male rats, the present study of brain metabolism found no sex differences in brain metabolism. The formation of PCP metabolites in male rat livers is at least partially mediated by the male-specific isozyme CYP2C11, and possibly CYP2D1. Nevertheless, the formation of the major brain metabolite, PCHP, was not inhibited by an anti-CYP2C11 or an anti-CYP2D6 antibody. However, PCHP formation was inhibited by drug inhibitors of CYP2D1-mediated metabolism, suggesting the involvement of a CYP2D isoform. These data indicate brain metabolism of PCP is significant, but unlike the liver it is not sexually dimorphic.

Metabolism of phencyclidine by human liver microsomes

These studies examined in vitro metabolism of phencyclidine (PCP) in a series of human liver microsomes (N = 10). Each sample was characterized for cytochrome P450 (CYP) content and for CYP1A, CYP2A, CYP2C, CYP2D, CYP2E, CYP3A, CYP4A, and lauric acid 11-hydroxylation metabolic activities. At least five PCP metabolites (c-PPC, t-PPC, PCHP, an unknown metabolite, and an irreversibly bound metabolite) were formed by the various human liver microsomes. Nevertheless, there was a large degree of inter-individual variation in the metabolite formation. For example, the irreversibly bound metabolite was formed in detectable amounts in only four of the ten samples. c-PPC, t-PPC and the irreversibly bound PCP metabolite formation rates significantly correlated with CYP3A activity. The CYP3A inhibitor troleandomycin was used to inhibit the formation of PCP metabolites. Troleandomycin inhibition was dose dependent with the highest dose producing complete inhibition of the formation of c-PPC, t-PPC, PCHP, and the irreversibly bound metabolite. In addition, PCP inhibited CYP3A-mediated testosterone 6 beta-hydroxylation by 50%. Furthermore, the relative intensity of CYP3A immunoreactive proteins significantly correlated with testosterone 6 beta-hydroxylation and with PCP metabolite formation (except for the unknown metabolite). PCHP formation also correlated with CYP1A activity, while the formation of the unknown PCP metabolite correlated with CYP2A activity. These studies suggest that several CYP isoforms contribute to PCP metabolism and that CYP3A plays a major role in PCP biotransformation in human liver microsomes.