Process intensification of EB66® cell cultivations leads to high-yield yellow fever and Zika virus production

A live-attenuated, human vaccine against mosquito-borne yellow fever virus has been available since the 1930s. The vaccine provides long-lasting immunity and consistent mass vaccination campaigns counter viral spread. However, traditional egg-based vaccine manufacturing requires about 12 months and vaccine supplies are chronically close to shortages. In particular, for urban outbreaks, vaccine demand can be covered rarely by global stockpiling. Thus, there is an urgent need for an improved vaccine production platform, ideally transferable to other flaviviruses including Zika virus. Here, we present a proof-of-concept study regarding cell culture-based yellow fever virus 17D (YFV) and wild-type Zika virus (ZIKV) production using duck embryo-derived EB66® cells. Based on comprehensive studies in shake flasks, 1-L bioreactor systems were operated with scalable hollow fiber-based tangential flow filtration (TFF) and alternating tangential flow filtration (ATF) perfusion systems for process intensification. EB66® cells grew in chemically defined medium to cell concentrations of 1.6 × 10⁸ cells/mL. Infection studies with EB66®-adapted virus led to maximum YFV titers of 7.3 × 10⁸ PFU/mL, which corresponds to about 10 million vaccine doses for the bioreactor harvest. For ZIKV, titers of 1.0 × 10¹⁰ PFU/mL were achieved. Processes were automated successfully using a capacitance probe to control perfusion rates based on on-line measured cell concentrations. The use of cryo-bags for direct inoculation of production bioreactors facilitates pre-culture preparation contributing to improved process robustness. In conclusion, this platform is a powerful option for next generation cell culture-based flavivirus vaccine manufacturing.

     

Adaptively timed conditioned responses and the cerebellum: A neural network approach

Conditioned responses often reflect knowledge about the timing of a US. This knowledge is manifested in the dependance of response topography on the CS-US interval employed in training. A neural network model and set of learning rules capable of simulating temporally adaptive features of conditioned responses is reviewed, and simulations are presented. In addition, we present a neural network implementation of the model which is designed to reconcile empirical studies of long-term synaptic depression in the cerebellum with neurobiological evidence from studies of the classically conditioned nictitating membrane response of the rabbit.     

Identification of compounds from the eggs of Ostrinia nubilalis and Mamestra brassicae having kairomone activity on Trichogramma brassicae

In the presence of an extract of Ostrinia nubilalis or Mamestra brassicae eggs, female Trichogramma brassicae exhibited increased rates of upwind locomotion in the tubes of a linear olfactometer. GC and GC-MS analyses of O. nubilalis and M. brassicae egg extracts revealed the presence of fatty acids, their ethyl esters, and various hydrocarbons. Exposing the wasps to a mixture of the five main saturated hydrocarbons (heneicosane, tricosane, pentacosane, heptacosane and nonacosane) increased the upwind progression in the olfactometer. Single hydrocarbons elicited reduced or no activity. Ethyl palmitate and palmitic acid were also effective in increasing upwind locomotion. Z11-14:Ac, the main component of the female sex pheromone of O. nubilalis was inactive, regardless of its concentration. It is concluded that various compounds present on the surface of the O. nubilalis egg masses may play a role in the orientation of T. brassicae to its host.     

Renal effects of low-dose aminophylline and enprofylline in newborn rabbits

Renal function was studied in 15 newborn New Zealand rabbits administered either 0.6 mg/kg enprofylline intravenously. Each animal acted as its own control. Glomerular filtration rate (GFR) and renal blood flow (RBF) were assessed by the clearances of inulin and para-aminohippuric acid, respectively. Enprofylline, a xanthine with low adenosine antagonistic properties, did not modify urine flow rate, GFR, RBF, renal vascular resistance, filtration fraction, sodium and potassium urinary excretion, whereas administration of theophylline, a potent adenosine antagonist, was associated with a significant increase in diuresis, renal vascular resistance and filtration fraction. The differences observed in the renal effects of theophylline and enprofylline strongly support the view that 1) the renal actions of micromolar concentrations of theophylline are mediated by an antagonism with endogenous renal adenosine; 2) renal adenosine could play a physiological role in the regulation of renal hemodynamics.     

Evolution of dispersal and life history strategies – <Emphasis Type="Italic">Tetrahymena</Emphasis> ciliates

Background  

Considerable attention has focused on how selection on dispersal and other core life-history strategies (reproductive effort, survival ability, colonization capacity) may lead to so-called dispersal syndromes. Studies on genetic variation in these syndromes within species could importantly increase our understanding of their evolution, by revealing whether traits co-vary across genetic lineages in the manner predicted by theoretical models, and by stimulating further hypotheses for experimental testing. Yet such studies remain scarce. Here we studied the ciliated protist Tetrahymena thermophila, a particularly interesting organism due to cells being able to transform into morphs differing dramatically in swim-speed. We investigated dispersal, morphological responses, reproductive performance, and survival in ten different clonal strains. Then, we examined whether life history traits co-varied in the manner classically predicted for ruderal species, examined the investment of different strains into short- and putative long-distance dispersal, while considering also the likely impact of semi-sociality (cell aggregation, secretion of 'growth factors') on dispersal strategies.