Gamma interferon responses induced by a panel of recombinant and purified mycobacterial antigens in healthy,non-mycobacterium bovis BCG-vaccinated Malawian young adults

We have previously shown that young adults living in a rural area of northern Malawi showed greater gamma interferon (IFN-gamma) responses to purified protein derivatives (PPD) prepared from environmental mycobacteria than to PPD from Mycobacterium tuberculosis. In order to define the mycobacterial species to which individuals living in a rural African population have been exposed and sensitized, we tested T-cell recognition of recombinant and purified antigens from M. tuberculosis (38 kDa, MPT64, and ESAT-6), M. bovis (MPB70), M. bovis BCG (Ag85), and M. leprae (65 kDa, 35 kDa, and 18 kDa) in >600 non-M. bovis BCG-vaccinated young adults in the Karonga District of northern Malawi. IFN-gamma was measured by enzyme-linked immunosorbent assay (ELISA) in day 6 supernatants of diluted whole-blood cultures. The recombinant M. leprae 35-kDa and 18-kDa and purified native M. bovis BCG Ag85 antigens induced the highest percentages of responders, though both leprosy and bovine tuberculosis are now rare in this population. The M. tuberculosis antigens ESAT-6 and MPT64 and the M. bovis antigen MPB70 induced the lowest percentages of responders. One of the subjects subsequently developed extrapulmonary tuberculosis; this individual had a 15-mm-diameter reaction to the Mantoux test and responded to M. tuberculosis PPD, Ag85, MPT64, and ESAT-6 but not to any of the leprosy antigens. We conclude that in this rural African population, exposure to M. tuberculosis or M. bovis is much less frequent than exposure to environmental mycobacteria such as M. avium, which have antigens homologous to the M. leprae 35-kDa and 18-kDa antigens. M. tuberculosis ESAT-6 showed the strongest association with the size of the Mantoux skin test induration, suggesting that among the three M. tuberculosis antigens tested it provided the best indication of exposure to, or infection with, M. tuberculosis.     

The Dominant Epitope of Borrelia garinii Outer Surface Protein C Recognized by Sera from Patients with Neuroborreliosis Has a Surface-Exposed Conserved Structural Motif

Epitope mapping of outer surface protein C (OspC) by using sera from patients with neuroborreliosis led to the identification of one single major immunodominant epitope within the C-terminal 10 amino acid residues. Peptide binding studies and alanine replacement scanning of the C-terminal decapeptide, PVVAESPKKP, revealed a critical role for the PKKP sequence and its terminal carboxyl group for the binding of immunoglobulin M (IgM) antibodies from patients with Lyme borreliosis. Electron microscopy of antibody-labeled spirochetes indicated that the C-terminal region is exposed on the surface of the spirochete. Based on homology to proteins of known function, this region most probably adopts a polyproline II-like helix, which is found in surface-exposed structures involved in protein-protein interactions. This structural motif is highly conserved in Borrelia species causing Lyme borreliosis and subjected to purifying selection. We suggest that the abundance of the C-terminal region of OspC on the surface of B. burgdorferi allows a multimeric high-avidity interaction between the spirochete and surface Igs on B cells. The resulting cross-linking of surface Igs on B cells may induce a T-cell-independent B-cell activation without IgM-to-IgG switching, thus explaining the lack of IgG antibodies to OspC in neuroborreliosis.     

Efficacy of Amodiaquine in uncomplicated falciparum malaria in Nigeria in an area with high-level resistance to Chloroquine and Sulphadoxine/Pyrimethamine

Falciparum Malaria is hyperendemic in southern Nigeria and chloroquine resistance is an increasing problem. Therefore, the parasitological and haematological response to treatment with amodiaquine was studied in children under 5 years during a 14-day follow-up. Of 105 children who accomplished the study (out of 114 who were enrolled), 95.3% were parasite-negative on thick blood film on day 7, which decreased to 89.5% on day 14. The haemoglobin levels increased on average by 1.3% on day 14 (±1.9) and more pronounced in children with anaemia < 10 g/dl on enrolment. The number of patients with adverse events (mainly pruritus and nausea) was few. This study shows that amodiaquine is effective, safe and affordable in an area with high resistance to chloroquine.     

Glucose-6-phosphate dehydrogenase activity in monolayer cultures of thyroid epithelial cells: TSH and inhibition of nitrogen oxide synthase affect the enzyme activity and the oxygen sensitivity of the histochemical assay

The objective was to investigate glucose-6-phosphate dehydrogenase (G6PD) activity in monolayer cultures of thyroid epithelial cells and to examine whether inhibition of nitric oxide synthase affects activity of G6PD or oxygen sensitivity of the assay. Primary cultures without TSH addition prior to experiments demonstrated a TSH-dependent increase in G6PD activity. G6PD activity was higher in F12 medium than in a serum-free physiological medium. Secondary cultures grown in F12 medium demonstrated a diminished activity of G6PD and a lack of response to TSH. In the serum-free physiological medium, G6PD activity was comparable to that found in primary cultures and a response to high concentrations of TSH was maintained. In primary cultures grown in F12 medium devoid of TSH, G6PD activity decreased dose-dependently when nitric oxide synthase activity was inhibited. The oxygen sensitivity of the assay was comparable to that reported previously in malignant cells and correlated with the activity of G6PD in primary cultures. We suggest that thyroid epithelial cells may be an appropriate system to investigate oxygen sensitivity of the G6PD assay as the cells demonstrate a reduced oxygen sensitivity which can be influenced by culture conditions.     

Effect of the serotonin agonist buspirone on behaviour and hypothalamic-pituitary-adrenal axis in confident and fearful mink

Behavioural and hypothalamic-pituitary-adrenal (HPA) axis responses were investigated in farm mink (Mustela vison) selected for either confident or fearful behaviour for nine generations.Two groups of 2-year-old confident (n=12) and fearful (n=12) female mink were given the serotonin (5-HT) 1A receptor agonist buspirone (1.25 mg/kg/day), whereas two other groups of 2-year-old confident (n=12) and fearful (n=12) female mink were given saline, continuously for 5 weeks via osmotic minipumps. Behavioural reactions towards a novel object and towards humans were tested after 19-25 days, and HPA axis reactivity [adrenocorticotropic hormone (ACTH), cortisol] was measured after 28-31 days of treatment. Confident mink were more exploratory than fearful mink towards humans and a novel object. Confident mink spent more time in contact with the object than did fearful mink during saline-but not during buspirone-treatment. buspirone increased approach-withdrawal conflict behaviour towards a object in fearful mink only. The chronic dose of buspirone did not reduce fear towards humans and did not affect latencies to reaction, number of contacts, number and duration of manipulations, and stereotypic behaviour in a Novel Object test. Different HPA axis responses have emerged between confident and fearful mink, together with a different degree of fear-related behaviour. Fearful mink have a higher cortisol combined with a lower ACTH secretion than confident mink in response to capture and blood sampling. The central serotonergic system may be involved, and even though the precise underlying mechanisms are presently unknown, treatment with a 5-HT(1A) receptor agonist reduces the difference between confident and fearful mink in HPA axis reactivity.     

Ly6C expression differentiates plasma cells from other B cell subsets in mice.

Plasma cell differentiation is induced in vitro by lipopolysaccharide (LPS) stimulation but can be blocked by including anti-CD40 antibodies. Using subtractive cDNA hybridization we have identified the cell surface protein Ly6C as differentially expressed on B cells stimulated with LPS only. Ly6C has been shown to be expressed on certain T cell subsets and on subsets of macrophages and NK cells, but not on resting B cells. We show that Ly6C is up-regulated upon LPS stimulation of B cells in vitro and that this up-regulation is blocked by anti-CD40 or anti-Ig antibodies. Furthermore, ELISPOT analysis of cells sorted by magnetic-activated cell sorting show that Ly6C is expressed on ex vivo plasma cells from the spleen and bone marrow. Flow cytometric analysis showed that Ly6C is expressed on splenic plasma cells as well as on lamina propria plasma cells. Finally, Ly6C cross-linking positively up-regulated the amount of immunoglobulin produced by LPS-stimulated splenic B cells in vitro.     

Presynaptic control of group Ia afferents in relation to acquisition of a visuo-motor skill in healthy humans

Sensory information continuously converges on the spinal cord during a variety of motor behaviours. Here, we examined presynaptic control of group Ia afferents in relation to acquisition of a novel motor skill. We tested whether repetition of two motor tasks with different degrees of difficulty, a novel visuo-motor task involving the ankle muscles, and a control task involving simple voluntary ankle movements, would induce changes in the size of the soleus H-reflex. The slope of the H-reflex recruitment curve and the H-max/M-max ratio were depressed after repetition of the visuo-motor skill task and returned to baseline after 10 min. No changes were observed after the control task. To elucidate the mechanisms contributing to the H-reflex depression, we measured the size of the long-latency depression of the soleus H-reflex evoked by peroneal nerve stimulation (D1 inhibition) and the size of the monosynaptic Ia facilitation of the soleus H-reflex evoked by femoral nerve stimulation. The D1 inhibition was increased and the femoral nerve facilitation was decreased following the visuo-motor skill task, suggesting an increase in presynaptic inhibition of Ia afferents. No changes were observed in the disynaptic reciprocal Ia inhibition. Somatosensory evoked potentials (SEPs) evoked by stimulation of the tibial nerve (TN) were also unchanged, suggesting that transmission in ascending pathways was unaltered following the visuo-motor skill task. Together these observations suggest that a selective presynaptic control of Ia afferents contributes to the modulation of sensory inputs during acquisition of a novel visuo-motor skill in healthy humans.