Tick-borne encephalitis vaccines: past and present

Vaccines to protect against tick-borne encephalitis (TBE) are produced by two manufacturers and are widely used in European and Asian countries, where TBE virus is endemic. General trends in vaccine development during recent decades and extensive postmarketing experience resulted in several modifications to their formulations and practical implications for use. Modifications were made to the production process, such as the change of the virus master bank from mouse brain to primary cells; to the excipients, especially the stabilizers and preservative; and to include formulations for children. Additionally, a rapid vaccination schedule has been developed for persons who require a fast onset of protection. Recent data from clinical studies and postmarketing surveillance indicate that both vaccines are safe, efficacious and interchangeable. Further (major) changes to formulation or alternative targets for vaccine development are not anticipated in the next 5 years. Recent serologic studies indicate that the persistence of protective immunity was longer than expected. Thus, recommendations for prolongation of TBE booster intervals have been made in several European countries, and a harmonization for booster recommendations is predicted within the European Union. Based on epidemiologic trends, the use of TBE vaccines will continue to increase in all age groups, including children.     

Phorbol ester-induced inhibition of the beta-adrenergic system in pulmonary endothelium: role of a pertussis toxin-sensitive protein

To investigate possible cellular mechanisms for how activation of protein kinase C inhibits the relaxation caused by isoproterenol, we studied the effect of the protein kinase C activator 4 beta-phorbol-12 beta-myristate-13 alpha-acetate (PMA) on the increase in cyclic AMP (cAMP) production and adenylate cyclase activity caused by isoproterenol in bovine pulmonary artery endothelial cells. Treatment of intact cells with PMA prevented in a time- and dose-dependent manner the increase in cAMP production caused by isoproterenol, whereas 4 alpha-phorbol-12 beta-myristate-13 alpha-acetate (4 alpha-PMA), which does not activate protein kinase C, did not affect isoproterenol-induced cAMP production. PMA also reduced the increase in adenylate cyclase activity caused by isoproterenol, forskolin, and Gpp(NH)p. To test the hypothesis that the inhibitory effect of PMA is mediated via a pertussis toxin-sensitive G protein, we determined whether pretreatment of the cells with pertussis toxin would prevent the inhibitory effects of PMA. In pulmonary endothelial cells, pertussis toxin ADP-ribosylated an Mr 40,000 peptide that comigrated with the pertussis toxin substrate of human erythrocytes. Pertussis toxin treatment eliminated the inhibitory effect of PMA on isoproterenol-stimulated cAMP production and adenylate cyclase activity. Thus, the protein kinase C activator PMA inhibits the increase in cAMP production and adenylate cyclase caused by isoproterenol. This inhibitory effect in endothelial cells appears to be mediated via a pertussis toxin-sensitive protein.     

Development and preliminary evaluation of a slide latex agglutination assay for detection of Clostridium perfringens type A enterotoxin

A slide latex agglutination (SLA) assay was developed for rapid screening for Clostridium perfringens type A enterotoxin (CPE). SLA specifically detected CPE added to buffer or normal feces (sensitivity limit of 1 μg CPE/g feces). Using clinical fecal samples from C. perfringens food poisoning cases, a strong correlation was shown between (1) SLA results and results from other CPE assays and (2) between SLA results and illness status.     

Regeneration of tooth development in vitro following sodium fluoride treatment

Mandibular incisors were dissected from the jaws of 15- and 16- days C57BL/10 mouse embryos and cultured on agar-solidified Eagle's basal medium supplemented with fetal calf serum, an antibiotic, and glutamine. The experimental medium was the same as the control except that fluoride was added such that the final concentrations ranged from 2.0-8.0 mM NaF. Control and experimental explants were recovered after two, four and six days of incubation and studied histologically. After two days of fluoride treatment (3.0 mM NaF), cellular degeneration was observed in the dental papilla mesenchyme while the enamel organ epithelium appeared more resistant. Prolonged treatment or treatment at higher concentrations resulted in destruction of the dental papilla. The enamel organ was still present but was abnormal and reduced. Older tooth germs were less affected overall when incubated at the same fluoride dosage and time of treatment. When explants subjected to limited exposure (2 days) to fluoride were placed on control medium, the suppressed tooth germs recovered. The recovery was enhanced by grafting untreated mesenchyme to the treated explants followed by incubation on control medium. The observations indicate that NaF can suppress the development of tooth germs in vitro and that recovery from the suppresion does occur. The more severe inhibition observed in the mesenchymal component when compared to the response of the epithelial component of the treated explants suggests that fluoride may alter the ultimate morphology of the tooth crown by disrupting the normal epithelial-mesenchymal interaction which occurs during early tooth development.     

Changes in the level of acetylcholinesterase of Nematospiroides dubius and Trichostrongylus colubriformis following paralysis by levamisole in vivo

Acetylcholinesterase (acetylcholine acetylhydrolase; EC 3.1.1.7) levels of Nematospiroides dubius from laboratory mice and Trichostrongylus colubriformis from lambs have been measured. The anthelmintic levamisole (leavo isomer of 2,3,5,6-tetrahydro-6-phenylimidazo-(2,1b)-thiazole (Tetramizole)) did not affect the level of acetylcholinesterase in N. dubius in vivo but caused a reduction in the level of the enzyme in T. colubriformis following paralysis in vivo. The effect of levamisole on acetylcholinesterase in the nematodes is explained in terms of the differing roles of the enzyme in these two species.     

A meta-analysis of the effect of HIV prevention interventions on the sex behaviors of drug users in the United States

We examined the effectiveness of 33 U.S.-based HIV intervention studies in reducing the sexual risk behaviors of drug users by reducing unprotected sex or increasing the use of male condoms. The studies, identified as of June 1998, through the HIV/AIDS Prevention Research Synthesis project, were published in 1988 or later, measured behavioral or biologic outcomes, used experimental designs or certain quasi-experimental designs, and reported sufficient data for calculating an effect size for sexual risk reduction. Of the 33 studies, 94% recruited injection drug users; 21% recruited crack users. The mean age of participants was 36 years. Almost all studies were randomized (94%), provided another HIV intervention to the comparison groups (91%), and evaluated behavioral interventions (91%). On average, interventions were conducted in 5 sessions (total, 10 hours) during 4.5 months. Interventions compared with no interventions were strong and significant (k = 3; odds ratio [OR], 0.60; 95% confidence interval [CI], 0.43-0.85). Interventions compared with other HIV interventions showed a modest additional benefit (k = 30; OR, 0.91; 95% CI, 0.81-1.03). When we extrapolated our result (an OR of 0.60) to a population with a 72% prevalence of risk behavior, the proportion of drug users who reduced their risk behaviors was 12.6% greater in the intervention groups than in the comparison groups. Our meta-analysis shows that interventions can lead to sexual risk reduction among drug users and justifies providing interventions to drug users. Developing interventions with stronger effects to further reduce sexual risk behaviors among drug users must remain a high priority.     

Altered gating of HERG potassium channels by cobalt and lanthanum

Activation of the rapid, delayed rectifier K current (IKr) is important for normal repolarization of cardiac action potentials, especially in mammalian ventricular muscle. The study of this current has been greatly aided by the discovery that the human ether-a-go-go-related gene (HERG) encodes the pore-forming alpha subunits of these channels. As for other voltage-activated K+ channels, divalent and trivalent cations affect the gating of HERG channels by screening negative membrane surface charges or by direct interaction with the channel gating mechanism. Previous studies have reported that IKr of myocytes, and HERG channels heterologously expressed in Xenopus oocytes, are reduced by external Co2+ and La3+. We have reinvestigated the "blocking" effect of Co2+ and La3+ on HERG channels expressed in Xenopus oocytes. At concentrations previously reported to block IKr or HERG current (IHERG), Co2+ (10 mM) and La3+ (10 microM) had only small effects on the magnitude of fully activated IHERG. The apparent block results from altered kinetics and voltage dependence of gating, similar to the effects of Ca2+ on HERG channels. Under control conditions, the half-points for voltage-dependent activation and inactivation of HERG were -35+/-2.1 and -76.3+/-1.7 mV, respectively. Co2+ and La3+ accelerated the rate of deactivation, decreased the rate of current activation, and shifted the half-point of the HERG channel activation curve by +53 and +65 mV, respectively. Co2+ shifted the voltage dependence of inactivation by + 14 mV, whereas La3+ had no effect. Co2+ also slowed the onset of IHERG inactivation and accelerated the rate of recovery from inactivation. These results indicate that reduction of IHERG by Co2+ (10 mM) and La3+ (10 microM) during depolarizing pulses is caused by a positive shift in the voltage dependence of activation, and does not result from pore block.     

A novel isoform of the smooth muscle cell differentiation marker smoothelin

Studies on smooth muscle cell differentiation and those on vascular development in mouse and humans have long been hampered by the lack of suitable markers. Here we describe a novel, large isoform of smoothelin, a structural protein of differentiated, contractile smooth muscle cells. The protein, which is highly conserved in mouse and humans, shows homology with other cytoskeleton-associated smooth muscle cell proteins and contains an actinin-type actin-binding domain. Northern blot analysis from various mouse organs identified short and long smoothelin mRNA forms, which exhibit distinct tissue expression patterns. The short form is highly expressed in visceral muscle tissues such as intestine and stomach and is not detectable in brain, while the long mRNA form is expressed in all vascularized organs. These results may provide new tools and approaches to study both smooth muscle cell differentiation and proliferative vascular disease. Received: 25 August 1998 / Accepted: 19 October 1998     

Lung preservation solution substrate composition affects rat lung oxidative metabolism during hypothermic storage

Lungs harvested for transplantation utilize oxygen after procurement. We investigated the effects of storage solution substrate composition on pulmonary oxidative metabolism and energetics during the preservation interval. Rat lungs were harvested and stored at 10 degrees C in low-potassium dextran (LPD) solution. Groups of lungs were preserved with preservation solution containing 5mM carbon-13 ((13)C) labeled glucose or increasing concentrations of (13)C labeled pyruvate. Additional groups of rat lungs were studied with dichloroacetate (DCA) added to the pyruvate-modified preservation solutions. Oxidative metabolism (measured by (13)C-enrichment of glutamate) and adenine nucleotide levels were quantified. Increasing preservation solution pyruvate concentration augmented glutamate (13)C-enrichment up to a concentration of 32mM pyruvate. DCA further stimulated oxidative metabolism only at lower concentrations of pyruvate (4 and 8mM). ATP and ADP were not different among groups, but AMP levels were higher in the glucose group. These data suggest that altering the substrate composition of the preservation solution influences lung metabolism during allograft preservation for transplantation.     

Involvement of central amygdalar and bed nucleus of the stria terminalis corticotropin-releasing factor in behavioral responses to social defeat

The authors investigated whether corticotropin-releasing factor (CRF) within the central nucleus of the amygdala (CeA) and bed nucleus of the stria terminalis (BNST) is a critical component of the neural circuitry mediating conditioned defeat. In this model, hamsters that have experienced social defeat subsequently display only submissive-defensive agonistic behavior instead of territorial aggression. Conditioned defeat was significantly reduced following infusion of the CRF receptor antagonist D-Phe CRF((12-41)) into the BNST but not into the CeA. In another experiment, hamsters given unilateral lesions of the CeA and infusions of D-Phe CRF((12-41)) into the contralateral BNST displayed significantly less submissive behavior than did controls. These data suggest that CRF acts within a neural circuit that includes the amygdala and the BNST to modulate agonistic behavior following social defeat.