Mapping immune variation and var gene switching in naive hosts infected with Plasmodium falciparum

Falciparum malaria is clinically heterogeneous and the relative contribution of parasite and host in shaping disease severity remains unclear. We explored the interaction between inflammation and parasite variant surface antigen (VSA) expression, asking whether this relationship underpins the variation observed in controlled human malaria infection (CHMI). We uncovered marked heterogeneity in the host response to blood challenge; some volunteers remained quiescent, others triggered interferon-stimulated inflammation and some showed transcriptional evidence of myeloid cell suppression. Significantly, only inflammatory volunteers experienced hallmark symptoms of malaria. When we tracked temporal changes in parasite VSA expression to ask whether variants associated with severe disease rapidly expand in naive hosts, we found no transcriptional evidence to support this hypothesis. These data indicate that parasite variants that dominate severe malaria do not have an intrinsic growth or survival advantage; instead, they presumably rely upon infection-induced changes in their within-host environment for selection.

CD19 as a membrane-anchored adaptor protein of B lymphocytes: costimulation of lipid and protein kinases by recruitment of Vav

CD19 is a coreceptor that amplifies signaling by membrane immunoglobulin (mIg) to promote responses of the B lymphocyte to T-dependent antigens. Vav is a guanine nucleotide exchange factor for the Rho, Rac, Cdc42 family of small GTPases. We found that coligating mIg and CD19 causes a synergistic increase in the tyrosine phosphorylation of CD19. Phosphorylated tyrosine-391 of CD19 binds Vav to mediate a sustained increase in intracellular Ca2+ concentration. This response correlates with activation by the CD19-Vav complex of phosphatidylinositol 4-phosphate 5-kinase for the synthesis of phosphatidylinositol 4,5-bisphosphate. Interaction of CD19 with Vav also mediates the synergistic activation of the mitogen-activated protein kinase JNK. Therefore, CD19 is a membrane adaptor protein that recruits Vav for the activation of lipid and protein kinases.

Evaluation of early feed restriction on egg size and hen performance

Feed restriction was implemented in a factorial design (2x4) when pullets were at either 5 or 10% egg production. Periods of feed restriction were for 0, 3, 4, or 5 d. Two trials each using 672 Hy-line W-77 White Leghorn Hens 19 wk of age were identified and randomly assigned to 16, 2x3 m pens at a density of 7 birds per square meter. Data recorded were days at sexual maturity, egg production, mortality, feed consumption, feed conversion, egg weight, body weight gain, and body weight uniformity. Hens placed on feed restriction reached sexual maturity 3 to 5 d later (P < 0.05) than the unrestricted birds. No significant main effects or interactions were found for egg production, feed consumption, feed conversion, mortality, egg weight, body weight gain, or body weight uniformity for the initial 15 wk or the entire egg production period. These results suggest that early egg size was not increased with the practice of early feed restriction nor did short- or long-term laying performance improve.

Adverse events in methotrexate-treated rheumatoid arthritis patients

Methotrexate (MTX) is an antifolate that has been in use for the treatment of rheumatoid arthritis (RA) since the early 1980s. Its efficacy has been clearly documented [1-4] and its administration early in the course of the disease is now generally accepted [5]. Side-effects from low weekly pulse MTX have been reported [1-6] and it was our initial experience that toxicity, rather than lack of efficacy, was the major factor limiting its clinical use [7]. However, when compared with other disease-modifying antirheumatic drugs, its toxicity appears to be comparable to that of antimalarials [8, 9]. The purpose of this paper is to discuss the possible mechanisms responsible for toxicity due to MTX used at low weekly pulse doses for the treatment of RA, as well as the different toxic manifestations reported in the literature.

Steady-state analysis of alpha-melanotropin in the pars intermedia of Anolis carolinensis: effect of background adaptation

The steady-state levels of alpha-melanotropin-stimulating hormone (alpha-MSH)-related peptides were examined in the pars intermedia of the reptile Anolis carolinensis as a function of background adaptation. After a 7-day period, the content of immunoreactive alpha-MSH-related material in the pars intermedia of light-adapted animals was approximately fourfold higher than that of animals maintained on a dark background for the same period. The immunoreactive alpha-MSH-related material present in the pars intermedia of light-adapted and dark-adapted animals was separately analyzed by gel filtration chromatography, reverse-phase HPLC, and cation-exchange chromatography. For light-adapted animals the major form of alpha-MSH had an apparent molecular weight of 1.5 kDa and a net charge of +4 at pH 3.5. Following reverse-phase HPLC this material eluted as a single peak of immunoreactivity with a retention time distinct from that of both mammalian ACTH(1-13)amide and N-acetyl-ACTH(1-13)amide. For dark-adapted animals a peak of alpha-MSH-sized material with an apparent molecular weight of 1.5 kDa was also detected. Following reverse-phase HPLC analysis this material eluted as an apparent single peak of immunoreactivity with a retention time distinct from that of the mammalian standards. Subsequent analysis of this major HPLC peak by cation-exchange chromatography revealed the presence of at least two forms of immunoreactive alpha-MSH. These forms differed in relative proportions. The major peak of immunoreactivity had a net charge of +4, whereas the minor peak had a net charge of +3. The +3 immunoreactive form was not detected to any appreciable degree in light-adapted animals.