Infection with feline immunodeficiency virus alters intestinal epithelial transport and mucosal immune responses to probiotics

HIV infection is associated with intestinal mucosal dysfunction and probiotics offer the therapeutic potential to enhance the mucosal barrier in HIV+ patients. To evaluate the response of immunocompromised hosts to probiotics, we orally administered Lactobacillus acidophilus to cats with chronic feline immunodeficiency virus (FIV) infection. FIV infection significantly affected transcellular, but not paracellular, transport of small molecules across the intestinal epithelium. Additionally, probiotic treatment of FIV+ cats resulted in changes in cytokine release and mucosal leukocyte percentages that were not paralleled in FIV- cats. These results suggest a novel role for FIV in upregulating transcellular transport across the gastrointestinal epithelial barrier and demonstrate the potential therapeutic use of probiotic bacteria to restore intestinal homeostasis.

Circulatory antigen processing by mucosal dendritic cells controls CD8(+) T cell activation

Circulatory antigens transit through the small intestine via the fenestrated capillaries in the lamina propria prior to entering into the draining lymphatics. But whether or how this process controls mucosal immune responses remains unknown. Here we demonstrate that dendritic cells (DCs) of the lamina propria can sample and process both circulatory and luminal antigens. Surprisingly, antigen cross-presentation by resident CX3CR1(+) DCs induced differentiation of precursor cells into CD8(+) T cells that expressed interleukin-10 (IL-10), IL-13, and IL-9 and could migrate into adjacent compartments. We conclude that lamina propria CX3CR1(+) DCs facilitate the surveillance of circulatory antigens and act as a conduit for the processing of self- and intestinally absorbed antigens, leading to the induction of CD8(+) T cells, that partake in the control of T cell activation during mucosal immune responses.

Nanomedicine Faces Barriers

Targeted nanoparticles have the potential to improve drug delivery efficiencies by more than two orders of magnitude, from the ~ 0.1% which is common today. Most pharmacologically agents on the market today are small drug molecules, which diffuse across the body’s blood-tissue barriers and distribute not only into the lesion, but into almost all organs. Drug actions in the non-lesion organs are an inescapable part of the drug delivery principle, causing “side-effects” which limit the maximally tolerable doses and result in inadequate therapy of many lesions. Nanoparticles only cross barriers by design, so side-effects are not built into their mode of operation. Delivery rates of almost 90% have been reported. This review examines the significance of these statements and checks how far they need qualification. What type of targeting is required? Is a single targeting sufficient? What new types of clinical challenge, such as immunogenicity, might attend the use of targeted nanoparticles?

Albumin transcytosis across the epithelium of the lactating mouse mammary gland

Murine milk contains 18 mg ml(-1) serum albumin, a concentration equal to that in the serum of the lactating mouse. We examined cellular transport using in vivo methods in the mouse. At steady state the specific activity of (125)I-albumin injected into the blood stream was equal in plasma and whey, confirming that milk albumin is extra-mammary in origin. Fluorescent albumin crossed the gland from basolateral surface to lumen via cytoplasmic vesicles, but was not transported in the apical to basal direction. Albumin was segregated from transferrin at the basal surface of the epithelial cells and did not colocalize with either caveolin-1 or -2. Vesicular transport was not disrupted by filipin providing additional evidence that, unlike the vascular endothelium, caveoli are not involved. Cytoplasmic albumin was localized to vesicles containing IgA and transport was disrupted by agents that interfere with clathrin-mediated endocytosis. Together, these findings provide evidence that albumin is transported across the mammary epithelium by the same pathway as immunoglobulin. The possibility that the massive transfer of albumin into mouse milk is mediated by fluid phase transport is considered.