Interleukin-7 Treatment Reverses Parenteral Nutrition-Induced Impairment of Resistance to Bacterial Pneumonia with Increased Secretory Immunoglobulin A Levels

Lipid Compositions of Total Parenteral Nutrition Affect Gut Peyer's Patches and Morphology in Mice

INTRODUCTION

Although parenteral nutrition (PN) is the only option for providing adequate nutrition to patients who cannot tolerate oral ingestion, it severely impairs intestinal barrier function in terms of morphology and immunity. While addition of either soybean oil (SO) or fish oil (FO) to PN partially reverses these defects, the effects of the oil composition (FO/SO ratio) on morphology and gut-associated lymphoid tissues (GALT) have yet to be elucidated. We focused on the effects of the FO/SO ratio in PN on the number of lymphocytes in Peyer's patches, immunoglobulin A levels, and intestinal structures.

METHODS

Male ICR mice (n = 61) were randomized into five groups; oral nutrition (Chow, n = 14) and four groups receiving PN without oral nutrition. PN solutions contained fat emulsions with the following FO:SO ratios: 0:1 (SO, n = 12), 1:11.5 (11.5FSO, n = 17),1:2 (1:2FSO, n = 13) and 1:0 (FO, n = 5). All mice underwent jugular vein catheter insertion. The PN groups were given isocaloric and isonitrogenous nutritional support with 20% of total calories from fat emulsions with equivalent fat delivery in 11.9 g/kg/d. After 5 d of each feeding, Peyer's patches lymphocytes were isolated from the small intestine, counted and analyzed with flowcytometry for determination of their phenotypes (αβTCR+, γδTCR+, CD4+, CD8+ and B cells). Villus height and crypt depth of the jejunum and ileum were evaluated with hematoxylin-eosin staining. Immunoglobulin A levels in the intestinal washings were also determined.

RESULTS

Numbers of total lymphocytes and B lymphocytes in PP were increased in the 1:2 FSO-PN but neither in the 1:11.5 FSO nor the FO group, as compared to the SO group. There were no marked differences among the groups in numbers neither of total T cells nor in any of T cell phenotypes determined. The 1:2 FSO group showed significantly greater villus height and crypt depth than the SO group. IgA levels did not differ significantly among the four PN groups.

CONCLUSIONS

The PN with 1:2 FSO (FO:SO = 1:2) maintained lymphocyte numbers in PP and intestinal villus morphology at levels nearly the same as those obtained with chow feeding. An appropriate ratio of FO to SO in PN is expected to prevent immunological impairment and morphological atrophy of the gut associated with lack of oral nutrition.

The Broad Immunomodulatory Effects of IL-7 and Its Application In Vaccines

Interleukin-7 (IL-7) is produced by stromal cells, keratinocytes, and epithelial cells in host tissues or tumors and exerts a wide range of immune effects mediated by the IL-7 receptor (IL-7R). IL-7 is primarily involved in regulating the development of B cells, T cells, natural killer cells, and dendritic cells via the JAK-STAT, PI3K-Akt, and MAPK pathways. This cytokine participates in the early generation of lymphocyte subsets and maintain the survival of all lymphocyte subsets; in particular, IL-7 is essential for orchestrating the rearrangement of immunoglobulin genes and T-cell receptor genes in precursor B and T cells, respectively. In addition, IL-7 can aid the activation of immune cells in anti-virus and anti-tumor immunity and plays important roles in the restoration of immune function. These biological functions of IL-7 make it an important molecular adjuvant to improve vaccine efficacy as it can promote and extend systemic immune responses against pathogens by prolonging lymphocyte survival, enhancing effector cell activity, and increasing antigen-specific memory cell production. This review focuses on the biological function and mechanism of IL-7 and summarizes its contribution towards improved vaccine efficacy. We hope to provide a thorough overview of this cytokine and provide strategies for the development of the future vaccines.

Bioinspired Heteromultivalent Ligand-Decorated Nanotherapeutic for Enhanced Photothermal and Photodynamic Therapy of Antibiotic-Resistant Bacterial Pneumonia

Pseudomonas aeruginosa can cause a multitude of inflammations in humans. Due to its ability to form biofilm, the bacteria show durable resistance to drugs. Herein, we developed a heteromultivalent ligand-decorated nanotherapeutic inspired by living system for inhibition of antibiotic-resistant bacterial pneumonia. The nanotherapeutic with a heteromultivalent glycomimetic shell can specifically recognize P. aeruginosa to inhibit its biofilm formation and protect native cells from bacterial infection; the rate of biofilm inhibition was up to 85%. The nanotherapeutic with a bioresponsive hydrophobic core can protonate and control drug release in the microenvironment of bacterial infections. By utilizing these properties, the nanotherapeutics can effectively penetrate the internal structure of biofilms to release the drug, dispersing the biofilm by over 80% under laser irradiation. In vivo bioinspired nanotherapeutics have the potential to efficiently inhibit antibiotic-resistant P. aeruginosa-induced pneumonia. Collectively, we expect biomimicking systems to be the next generation of prevention and treatment as integrated antibacterial agents against P. aeruginosa.

A Biomimetic Non-Antibiotic Approach to Eradicate Drug-Resistant Infections

The chronic infections by pathogenic Pseudomonas aeruginosa (P. aeruginosa) remain to be properly addressed. In particular, for drug-resistant strains, limited medication is available. An in vivo pneumonia model induced by a clinically isolated aminoglycoside resistant strain of P. aeruginosa is developed. Tobramycin clinically treating P. aeruginosa infections is found to be ineffective to inhibit or eliminate this drug-resistant strain. Here, a newly developed non-antibiotics based nanoformulation plus near-infrared (NIR) photothermal treatment shows a remarkable antibacterial efficacy in treating this drug-resistant pneumonia. The novel formulation contains 50-100 nm long nanorods decorated with two types of glycomimetic polymers to specifically block bacterial LecA and LecB lectins, respectively, which are essential for bacterial biofilm development. Such a 3D display of heteromultivalent glycomimetics on a large scale is inspired by the natural strengthening mechanism for the carbohydrate-lectin interaction that occurs when bacteria initially infects the host. This novel formulation shows the most efficient bacteria inhabitation and killing against P. aeruginosa infection, through lectin blocking and the near-infrared-light-induced photothermal effect of gold nanorods, respectively. Collectively, the novel biomimetic design combined with the photothermal killing capability is expected to be an alternative treatment strategy against the ever-threatening drug-resistant infectious diseases when known antibiotics have failed.

Impact of the feeding route on gut mucosal immunity

PURPOSE OF REVIEW

Enteral nutrition is recommended as a standard nutritional therapy in clinical settings. The rationale behind enteral nutrition may be decreased infectious morbidities compared with parenteral nutrition. However, the mechanism may not be well understood.

RECENT FINDINGS

Animal studies have revealed that enteral nutrition, compared with parenteral nutrition, preserves the gut-associated lymphoid tissue mass and function with well controlled gut cytokine milieu and intracellular signaling pathway, leading to the maintenance of intestinal and extraintestinal acquired mucosal immunity. Moreover, enteral nutrition can enhance the gut innate immunity by increasing the antimicrobial peptides, such as secretory phospholipase A2. More importantly, a recent clinical study demonstrated preoperative parenteral nutrition without enteral nutrition to decrease the number of T cells, IgA-producing cells, and mature dendritic cells in human terminal ileum, which are consistent with the data obtained from animal studies. Investigation of the mechanism has given us some surrogates of enteral nutrition during parenteral nutrition, such as glutamine, butyric acid, cytokines, and other mediators. However, to date, no surrogates can restore parenteral-nutrition-induced impairment of host defense completely.

SUMMARY

Because enteral nutrition is a practical way to preserve gut immunity, clinicians should make any efforts to shorten the period of enteral nutrition absence and increase the dose according to the degree of tolerance.