Protein glycosylation in Campylobacter jejuni: partial suppression of pglF by mutation of pseC

Campylobacter jejuni has systems for N- and O-linked protein glycosylation. Although biochemical evidence demonstrated that a pseC mutant in the O-linked pathway accumulated the product of pglF in the N-linked pathway, analyses of transformation frequencies and glycosylation statuses of N-glycosylated proteins indicated a partial suppression of pglF by pseC.     

Robust anti-tumor immunity and memory in Rag-1-deficient mice following adoptive transfer of cytokine-primed splenocytes and tumor CD80 expression

Successful immunotherapy of solid tumors has proven difficult to achieve. The aim of the current study was to further investigate the effects of peripheral CD80-mediated co-stimulation on the efficacy of polyclonal anti-tumor effector CTL in an adoptive transfer model. Splenocytes obtained from wild-type mice immunized with CD80-transduced EL4 tumor cells were expanded in vitro in the presence of either IL-12 or IL-15 and irradiated CD80-transduced EL4 tumor cells. Polyclonal CD8 T cells were the major subset in the effector population. Primed effector cells were adoptively transferred into immuno-deficient Rag-1-deficient mice which were then challenged with syngeneic vector-control or CD80-transduced EL4 tumor cells. Expression of CD80 enhanced the elimination of EL4 tumors and mouse survival. Both IL-12 and IL-15 cultured cells had enhanced cytotoxicity. Importantly, anti-tumor memory was maintained without tumor evasion following re-challenge with either CD80-transduced and vector-control EL4 cells. We also show, using antibody-mediated depletion, that endogenous NK cells present in Rag-1-deficent mice exert anti-EL4 tumor activity that is enhanced by CD80 expression. Collectively these data show that peripheral co-stimulation by tumor expression of CD80 results in enhanced anti-tumor efficacy of NK and polyclonal effector T cells, and suggest that TCR repertoire diversity helps protect against tumor escape and provides memory with resultant robust immunity to subsequent tumor challenge irrespective of CD80 status.     

Evaluation of three equine FSH superovulation protocols in mares

Superovulation could potentially increase embryo recovery for immediate transfer or cryopreservation. The objectives were to evaluate the effect of pretreatment with progesterone and estradiol (P+E) on follicular response to eFSH and compare doses of eFSH and ovulatory agents on follicular development and ovulation in mares. In Experiment 1, 40 mares were assigned to one of four treatment groups. Group 1 consisted of untreated controls. Group 2 mares were administered eFSH without pretreatment with P+E. Group 3 mares were administered P+E for 10 days starting in mid-diestrus followed by eFSH therapy. Group 4 mares were administered P+E for 10 days followed by eFSH therapy. All treated mares were administered 12.5mg eFSH twice daily and prostaglandins were given on the second day of eFSH therapy. Mares were bred with fresh semen the day of hCG administration and with cooled semen the following day. The numbers of preovulatory follicles and ovulations were lower for mares treated with P+E prior to eFSH treatment. Pretreatment with P+E in estrus also resulted in a lower embryo recovery rate per ovulation compared to the other two eFSH treatment groups. In Experiment 2, two doses of eFSH (12.5 and 6.25mg) and two ovulation-inducing agents (hCG and deslorelin) were evaluated. The number of preovulatory follicles was greater for mares given 12.5mg of eFSH compared to mares given 6.25mg. Number of ovulations was greatest for mares given 12.5mg of eFSH twice daily followed by administration of hCG. Embryo recovery per flush was similar among treatment groups, but the percent of embryos per ovulation was higher for mares given the low dose of eFSH. In summary, there was no advantage to giving P+E prior to eFSH treatment. In addition, even though the lower dose of eFSH resulted in fewer ovulations, embryo recovery per flush and embryo recovery per ovulation were similar or better for those given the lower dose of eFSH.     

Chemotherapy-induced diarrhea is associated with changes in the luminal environment in the DA rat

The microflora of the gastrointestinal tract (GIT) are a complex ecosystem, performing a number of beneficial functions. Irinotecan causes both early and late diarrhea, the latter possibly caused, in part, by changes in the microflora of the GIT. Female DA rats were given atropine subcutaneously, prior to a single 200 mg/kg intraperitoneal dose of irinotecan. Animals were monitored for diarrhea and killed at 30 and 60 mins, 2, 6, 12, 24, 48, and 72 hrs after chemotherapy administration. Control rats received no treatment. Fecal samples and stomach, jejunum, and colon samples were collected and stored at -70 degrees C until required. Standard microbiological culture techniques were used to grow and isolate the flora. Biochemical tests were used to identify the bacteria. The level of growth was noted for relative comparison between time points and graded accordingly. Early diarrhea was observed in the rats from 2-6 hrs after treatment, after which time the diarrhea resolved. Late onset diarrhea was apparent 72 hrs after treatment. Changes were seen in the flora of the stomach, jejunum, colon and feces. The majority of microflora changes were seen 6, 12, and 24 hrs after treatment, with a relative increase or decrease in the presence of bacteria in comparison with control rats. In some rats bacteria were not observed at all time points, and different bacteria not seen in control animals were identified in rats treated with irinotecan. These changes were observed up to 72 hrs after treatment. In conclusion, irinotecan treatment causes changes in the flora of the stomach, jejunum, colon, and feces of rats and is associated with the development of diarrhea. These changes in flora may have systemic effects and in particular may contribute to the development of chemotherapy-induced mucositis.     

Structure-Function Analysis of Heterodimer Formation,Oligomerization, and Receptor Binding of the Staphylococcus aureus Bi-component Toxin LukGH

The bi-component leukocidins of Staphylococcus aureus are important virulence factors that lyse human phagocytic cells and contribute to immune evasion. The γ-hemolysins (HlgAB and HlgCB) and Panton-Valentine leukocidin (PVL or LukSF) were shown to assemble from soluble subunits into membrane-bound oligomers on the surface of target cells, creating barrel-like pore structures that lead to cell lysis. LukGH is the most distantly related member of this toxin family, sharing only 30–40% amino acid sequence identity with the others. We observed that, unlike other leukocidin subunits, recombinant LukH and LukG had low solubility and were unable to bind to target cells, unless both components were present. Using biolayer interferometry and intrinsic tryptophan fluorescence we detected binding of LukH to LukG in solution with an affinity in the low nanomolar range and dynamic light scattering measurements confirmed formation of a heterodimer. We elucidated the structure of LukGH by x-ray crystallography at 2.8-Å resolution. This revealed an octameric structure that strongly resembles that reported for HlgAB, but with important structural differences. Structure guided mutagenesis studies demonstrated that three salt bridges, not found in other bi-component leukocidins, are essential for dimer formation in solution and receptor binding. We detected weak binding of LukH, but not LukG, to the cellular receptor CD11b by biolayer interferometry, suggesting that in common with other members of this toxin family, the S-component has the primary contact role with the receptor. These new insights provide the basis for novel strategies to counteract this powerful toxin and Staphylococcus aureus pathogenesis.     

Synapse-Assembly Proteins Maintain Synaptic Vesicle Cluster Stability and Regulate Synaptic Vesicle Transport in Caenorhabditis elegans

The functional integrity of neurons requires the bidirectional active transport of synaptic vesicles (SVs) in axons. The kinesin motor KIF1A transports SVs from somas to stable SV clusters at synapses, while dynein moves them in the opposite direction. However, it is unclear how SV transport is regulated and how SVs at clusters interact with motor proteins. We addressed these questions by isolating a rare temperature-sensitive allele of Caenorhabditis elegans unc-104 (KIF1A) that allowed us to manipulate SV levels in axons and dendrites. Growth at 20° and 14° resulted in locomotion rates that were ∼3 and 50% of wild type, respectively, with similar effects on axonal SV levels. Corresponding with the loss of SVs from axons, mutants grown at 14° and 20° showed a 10- and 24-fold dynein-dependent accumulation of SVs in their dendrites. Mutants grown at 14° and switched to 25° showed an abrupt irreversible 50% decrease in locomotion and a 50% loss of SVs from the synaptic region 12-hr post-shift, with no further decreases at later time points, suggesting that the remaining clustered SVs are stable and resistant to retrograde removal by dynein. The data further showed that the synapse-assembly proteins SYD-1, SYD-2, and SAD-1 protected SV clusters from degradation by motor proteins. In syd-1, syd-2, and sad-1 mutants, SVs accumulate in an UNC-104-dependent manner in the distal axon region that normally lacks SVs. In addition to their roles in SV cluster stability, all three proteins also regulate SV transport.