Neonatal small bowel epithelia: enhancing anti-bacterial defense with lactoferrin and Lactobacillus GG

BACKGROUND AND AIMS: Extremely preterm human infants have increased susceptibility to small bowel infection. We hypothesized that early colonization of the immature small intestine with Lactobacillus GG (LGG), and use of a recombinant lactoferrin (rhLF) to promote growth of LGG, would enhance gut defenses against enteroinvasive Escherichia coli. METHODS: Newborn rat pups were treated with nothing, intra-gastric LGG, or rhLF + LGG on days 3 and 4 of life. Gut colonization by LGG was quantified in lavaged jejunal and ileal fluid and gut wall homogenates on day 5 of life. Separate studies used similarly treated litters of newborn rats that were infected late on day 4 of life with E. coli [10(12) CFU/kg]. Sixteen hours later, the numbers of E. coli were measured in small bowel fluid and gut wall homogenates. RESULTS: Control pups initially had lactic acid bacteria colonize the bowel, but these bacteria were not LGG. Pups treated with LGG or rhLF + LGG had significantly higher numbers of LGG in the ileum versus jejunum. Contrary to our hypothesis, rhLF did not augment LGG colonization. After E. coli-related gut infection, planktonic [lavage fluid] and epithelia-adherent growth [gut wall homogenates] of E. coli in the small bowel were most effectively reduced by pre-treatment with rhLF and LGG (P < .05). CONCLUSION: Prophylactic therapy with recombinant human lactoferrin and the probiotic, Lactobacillus GG, act to enhance defenses against invasive E. coli in the nascent small intestine. We suggest that rhLF and LGG are therapeutic agents that may reduce necrotizing enterocolitis and gut-related sepsis in preterm human infants.     

Bias in satellite-derived pigment measurements due to coccolithophores and dinoflagellates

Satellite-derived estimates of phytoplankton pigments are thoughtto be affected by the phytoplankton species composition. Measurementsof surface algal chlorophyll and satellite-derived pigment werecompared for waters containing coccolithophores and dinoflagellates.Satellite-derived chlorophyll concentration was underestimatedby a factor of 2–3 in a patch of the large coccolithophore,Umbilicosphaera sibogae, and also in a bloom of the dinoflagellate,Gonyaulax polyedra. Overall abundance and species-specific propertiessuch as light scatter and vertical migration probably causedthese results.     

NGF and Neurotrophin-3 Both Activate TrkA on Sympathetic Neurons but Differentially Regulate Survival and Neuritogenesis

In this report we examine the biological and molecular basis of the control of sympathetic neuron differentiation and survival by NGF and neurotrophin-3 (NT-3). NT-3 is as efficient as NGF in mediating neuritogenesis and expression of growth-associated genes in NGF-dependent sympathetic neurons, but it is 20–40fold less efficient in supporting their survival. Both NT-3 and NGF induce similar sustained, long-term activation of TrkA, while NGF is 10-fold more efficient than NT-3 in mediating acute, short-term TrkA activity. At similar acute levels of TrkA activation, NT-3 still mediates neuronal survival two- to threefold less well than NGF. However, a mutant NT-3 that activates TrkC, but not TrkA, is unable to support sympathetic neuron survival or neuritogenesis, indicating that NT3–mediated TrkA activation is necessary for both of these responses. On the basis of these data, we suggest that NGF and NT-3 differentially regulate the TrkA receptor both with regard to activation time course and downstream targets, leading to selective regulation of neuritogenesis and survival. Such differential responsiveness to two ligands acting through the same Trk receptor has important implications for neurotrophin function throughout the nervous system.     

The quantitative analysis of nanoplankton: a study of methods

The Filter-Transfer-Freeze (FTP) technique has been comparedto traditional techniques (Utermhl, electronic particle counter,counting chamber, etc.) for ability to give quantitative cell-densityestimates of either natural water samples or Laboratory cultures.The FTF technique was found to be equal or superior to theseother methods for nanoplankton populations. In addition, theFTF technique offers many advantages such as (i) good opticalquality of the sample. (ii) flexibility in preservation andfixation of sample, (iii) convenience of multiple optical modesfor sample analysis and (iv) rapid and easy preparation allowingaccurate analysis of oceanic nanoplankton on board ship.     

Vaccination Expands Antigen-Specific CD4+ Memory T Cells and Mobilizes Bystander Central Memory T Cells

CD4⁺ T helper memory (Th_mem) cells influence both natural and vaccine-boosted immunity, but mechanisms for their maintenance remain unclear. Pro-survival signals from the common gamma-chain cytokines, in particular IL-7, appear important. Previously we showed in healthy volunteers that a booster vaccination with tetanus toxoid (TT) expanded peripheral blood TT-specific Th_mem cells as expected, but was accompanied by parallel increase of Th_mem cells specific for two unrelated and non cross-reactive common recall antigens. Here, in a new cohort of healthy human subjects, we compare blood vaccine-specific and bystander Th_mem cells in terms of differentiation stage, function, activation and proliferative status. Both responses peaked 1 week post-vaccination. Vaccine-specific cytokine-producing Th_mem cells were predominantly effector memory, whereas bystander cells were mainly of central memory phenotype. Importantly, TT-specific Th_mem cells were activated (CD38^High HLA-DR⁺), cycling or recently divided (Ki-67⁺), and apparently vulnerable to death (IL-7Rα^Low and Bcl-2 ^Low). In contrast, bystander Th_mem cells were resting (CD38^Low HLA-DR^- Ki-67^-) with high expression of IL-7Rα and Bcl-2. These findings allow a clear distinction between vaccine-specific and bystander Th_mem cells, suggesting the latter do not derive from recent proliferation but from cells mobilized from as yet undefined reservoirs. Furthermore, they reveal the interdependent dynamics of specific and bystander T-cell responses which will inform assessments of responses to vaccines.     

DNA fusion vaccines enter the clinic

Induction of effective immune attack on cancer cells in patients requires conversion of weak tumor antigens into strong immunogens. Our strategy employs genetic technology to create DNA vaccines containing tumor antigen sequences fused to microbial genes. The fused microbial protein engages local CD4+ T cells to provide help for anti-tumor immunity, and to reverse potential regulation. In this review, we focus on induction of CD8+ T cells able to kill target tumor cells. The DNA vaccines incorporate tumor-derived peptide sequences fused to an engineered domain of tetanus toxin. In multiple models, this design induces strong CD8+ T-cell responses, able to suppress tumor growth. For clinical relevance, we have used “humanized” mice expressing HLA-A2, successfully inducing cytolytic T-cell responses against a range of candidate human peptides. To overcome physical restriction in translating to patients, we have used electroporation. Clinical trials of patients with cancer are showing induction of responses, with preliminary indications of suppression of tumor growth and evidence for clinically manageable concomitant autoimmunity.     

Mobilizing Endogenous Stem Cells for Repair and Regeneration: Are We There Yet?

Harnessing endogenous repair mechanisms to promote tissue regeneration in situations in which it does not normally occur has long been a goal in biomedical science. Recent advances in tissue stem cells indicate that this goal may now be achievable. Here we consider both the promise and the hurdles we still have to overcome.