Immune Defense Cells Research Articles

Toxoplasma gondii promotes changes in VIPergic submucosal neurons, mucosal intraepithelial lymphocytes, and goblet cells during acute infection in the ileum of rats

The intestinal mucosa plays an important role in the mechanical barrier against pathogens. During Toxoplasma gondii infection, however, the parasites invade the epithelial cells of the small intestine and initiate a local immune response. In the submucosal plexus, this response promotes an imbalance of neurotransmitters and induces neuroplasticity, which can change the integrity of the epithelium and its secretory function. This study evaluated the submucosal neurons throughout acute T. gondii infection and the relationship between possible alterations and the epithelial and immune defense cells of the mucosa. Forty Wistar rats were randomly assigned to 8 groups (n=5): 1 control group, uninfected, and 7 groups infected with an inoculation of 5000 sporulated T. gondii oocysts (ME-49 strain, genotype II). Segments of the ileum were collected for standard histological processing, histochemical techniques, and immunofluorescence. The infection caused progressive neuronal loss in the submucosal general population and changed the proportion of VIPergic neurons throughout the infection periods. These changes may be related to the observed reduction in goblet cells that secret sialomucins and increase in intraepithelial lymphocytes after 24hours, and the increase in immune cells in the lamina propria after 10days of infection. The submucosa also presented fibrogenesis, characterizing injury and tissue repair. The acute T. gondii infection in the ileum of rats changes the proportion of VIPergic neurons and the epithelial cells, which can compromise the mucosal defense during infection.

Occupational exposure to diesel engine exhaust and serum cytokine levels

The International Agency for Research on Cancer has classified diesel engine exhaust (DEE) as a human lung carcinogen. Given that inflammation is suspected to be an important underlying mechanism of lung carcinogenesis, we evaluated the relationship between DEE exposure and the inflammatory response using data from a cross-sectional molecular epidemiology study of 41 diesel engine testing workers and 46 unexposed controls. Repeated personal exposure measurements of PM2.5 and other DEE constituents were taken for the diesel engine testing workers before blood collection. Serum levels of six inflammatory biomarkers including interleukin (IL)-1, IL-6, IL-8, tumor necrosis factor (TNF)-α, macrophage inflammatory protein (MIP)-1β, and monocyte chemotactic protein (MCP)-1 were analyzed in all subjects. Compared to unexposed controls, concentrations of MIP-1β were significantly reduced by ∼37% in DEE exposed workers (P < 0.001) and showed a strong decreasing trend with increasing PM2.5 concentrations in all subjects (Ptrend < 0.001) as well as in exposed subjects only (Ptrend = 0.001). Levels of IL-8 and MIP-1β were significantly lower in workers in the highest exposure tertile of PM2.5 (>397 µg/m3 ) compared to unexposed controls. Further, significant inverse exposure-response relationships for IL-8 and MCP-1 were also found in relation to increasing PM2.5 levels among the DEE exposed workers. Given that IL-8, MIP-1β, and MCP-1 are chemokines that play important roles in recruitment of immunocompetent cells for immune defense and tumor cell clearance, the observed lower levels of these markers with increasing PM2.5 exposure may provide insight into the mechanism by which DEE promotes lung cancer. Environ. Mol. Mutagen. 59:144-150, 2018. © 2017 Wiley Periodicals, Inc.

Comparative biology of the pentraxin protein family: evolutionarily conserved component of innate immune system.

The immune system is based on the actions of the collection of specialized immune defense cells and their secreted proteins and peptides that defend the host against infection by parasites. Parasites are organisms that live part or all of their lives in close physical association with the host and extract nutrients from the host and, by releasing toxins and virulence factors, cause disease with the potential for injury and premature death of that host. Parasites of the metazoa can be viruses, eubacteria, fungi, protozoans, and other metazoans. The immune system operates to kill or eliminate parasites and eliminate or detoxify their toxins and virulence factors. Although some of the elements of immune systems are specific to a particular phylum of metazoans, others show extensive evolutionary conservation, being present in several or all major phyla of the metazoa. The pentraxins display this latter character in their roles in immune defense. Pentraxins have been documented in vertebrates, nonvertebrate chordates, arthropods, and mollusks and may be present in other taxa of metazoans. Presumably the pentraxins appeared early in the evolution of metazoa, prior to their evolutionary divergence in the Precambrian epoch into many phyla present today, and have been preserved for the 542millionyears since that explosive evolutionary radiation. The fidelity with which these phyla have preserved the pentraxins suggests that the functions of these proteins are important for survival of the members of these diverse taxa of animals.

Abstract 4836: Immune-tolerance due to aberrant expression of Natural Killer-Cell Immunoglobulin-like Receptors (KIRs) on cancer cells and enhanced cancer-platelet interactions

Abstract Background: Metastatic cancer cells spread through blood vessels where they constantly interact with platelets and leukocytes, forming tumor microemboli and thereby protected from otherwise rapid elimination from host immune defense cells such as NK cells. We previously demonstrated that metastatic cancer cells with aberrant expression or with forced ectopic expression of Natural Killer Immunoglobulin-like Receptors (KIRs) are more resistant to NK killing than those with null or low KIR expression. Here we report that KIR-expressing cancer cells interact more strongly with platelets leading to significantly increase in NK tolerance than those cancer cells with null or low KIR expression. We have demonstrated that certain anti-platelet antagonists are capable of reversing the NK tolerance of these cancer cells in vitro. Methods: Aberrant expressions of KIR genes in metastatic cancers derived from orthotopic rat models were detected by DNA microarray analysis and verified with immunohistochemistry and flow cytometry. Stable transformants with ectopic expression of KIR2DL1 or KIR3DL1 were enriched by cell sorting. Binding of cancer cells with human platelets were analyzed by flow cytometry. NK killing of GFP-tagged cancer cells with differential KIR expressions in the presence and absence of human platelets, with or without pretreatment of anti-platelet antagonists or anti-KIR antibodies, was accessed with a fluorescent plate reader. Results: Using in vitro NK cytotoxic assays, we have found that KIR (aberrant or ectopic) expression or platelet coating on cancers clearly increased their resistance to NK cell killing when compared with parental cells. Interestingly, platelet coating on those metastatic cancer cells with high (aberrant or ectopic) KIR expression increased their IC50 values by 6 to 14 folds respectively when compared with parental cells. We show that NK tolerance correlates positively with platelet coating and the levels of KIR expression on the cancer cells (with correlation coefficient = 0.90 to 0.98), and that the NK resistance is significantly increased when both KIR aberrant expression and platelet coating are present on the cancer cells. However, pretreatment with anti-KIR antibodies and anti-platelet antagonists effectively reverse NK resistance. Conclusion: Aberrant KIR expression on cancer cells enhances their interaction with platelets leading to significant increase in NK tolerance. Anti-platelet antagonists and anti-KIR antibodies alone or in combination may have clinical potential for the treatment or prevention of metastatic and immune resistant cancer cells. Citation Format: Daniel CF Chan, Zhiyong Zhang, Di Zheng, Tiffany Chan, Mary Berg, Kathryn Horwitz, Natalie Ahn, Lewis Lanier, Paul Bunn. Immune-tolerance due to aberrant expression of Natural Killer-Cell Immunoglobulin-like Receptors (KIRs) on cancer cells and enhanced cancer-platelet interactions. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4836. doi:10.1158/1538-7445.AM2014-4836

Aggressive forms of periodontitis secondary to systemic disorders.

A number of systemic disorders increase a patient's susceptibility to destructive periodontitis and have impacts on periodontal disease progression and severity. The underlying factors are usually genetic and are mainly related to alterations in the immune response and in certain endocrine functions, leading to various syndromes in which periodontitis and/or early tooth loss are secondary manifestations. Neutrophils are important immune defense cells that play a significant role in controlling the spread of microbial plaque infections in the dentogingival region. This review focuses on a selected group of systemic disorders that are associated with alterations in either neutrophil counts (quantitative disorders) or function (qualitative disorders), and defects in the mineralization of bone and dental tissues. In most of these diseases controlling the periodontal disease progression is very challenging. Proper diagnosis is a prerequisite for proper management of the periodontal problem. Future advances in research, including gene targeting and the resolution of enzyme deficiencies, may bring about remedies of the underlying systemic disorders and may significantly improve the outcome of periodontal treatment in these patients.

Monovalent mannose-based DC-SIGN antagonists: Targeting the hydrophobic groove of the receptor

Dendritic cell-specific, intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) is a C-type lectin expressed specifically on dendritic cells. It is a primary site for recognition and binding of various pathogens and thus a promising therapeutic target for inhibition of pathogen entry and subsequent prevention of immune defense cell infection. We report the design and synthesis of d-mannose-based DC-SIGN antagonists bearing diaryl substituted 1,3-diaminopropanol or glycerol moieties incorporated to target the hydrophobic groove of the receptor. The designed glycomimetics were evaluated by in vitro assay of the isolated DC-SIGN extracellular domain for their ability to compete with HIV-1 gp120 for binding to the DC-SIGN carbohydrate recognition domain. Compounds 14d and 14e, that display IC50 values of 40 μM and 50 μM, are among the most potent monovalent DC-SIGN antagonists reported. The antagonistic effect of all the synthesized compounds was further evaluated by a one-point in vitro assay that measures DC adhesion. Compounds 14d, 14e, 18d and 18e were shown to act as functional antagonists of DC-SIGN-mediated DC adhesion. The binding mode of 14d was also studied by molecular docking and molecular dynamics simulation, which revealed flexibility of 14d in the binding site and provides a basis for further optimization.

Calcitonin gene-related peptide is a key neurotransmitter in the neuro-immune axis

The question of how the neural and immune systems interact in host defense is important, integrating a system that senses the whole body with one that protects. Understanding the mechanisms and routes of control could produce novel and powerful ways of promoting and enhancing normal functions as well as preventing or treating abnormal functions. Fragmentation of biological research into specialities has resulted in some failures in recognizing and understanding interactions across different systems and this is most striking across immunology, hematology, and neuroscience. This reductionist approach does not allow understanding of the in vivo orchestrated response generated through integration of all systems. However, many factors make the understanding of multisystem cross-talk in response to a threat difficult, for instance the nervous and immune systems share communication molecules and receptors for a wide range of physiological signals. But, it is clear that physical, hard-wired connections exist between the two systems, with the key link involving sensory, unmyelinated nerve fibers (c fibers) containing the neuropeptide calcitonin gene-related peptide (CGRP), and modified macrophages, mast cells and other immune and host defense cells in various locations throughout the body. In this review we will therefore focus on the induction of CGRP and its key role in the neuroimmune axis.

Effects of pH, temperature, and osmolarity on the morphology and survival rate of primary hemocyte cultures from the Mitten Crab, Eriocheir sinensis

Hemocytes are the main immune defense cells in crustacean, and its in vitro culture can be a useful tool for the study of host and pathogen interaction. In the present study, the primary hemocyte culture of Chinese mitten crab (Eriocheir sinensis), including mixed and single hemocyte, was set up for the first time. In this study, different pH (6.4, 6.8, 7.2, 7.6, and 8.0), temperature (26, 28, and 30°C), and osmolarity (500, 700, 900, 1,100, and 1,300 mOsm kg(-1)) values were tested. Moreover, the effects of two types of medium (1× L-15 and 3× L-15) with the same osmolarity on hemocyte culture were evaluated. After incubation at different culture conditions, the morphological changes (degranulation, lysis, shrinkage, and detachment) and survival rate of hemocytes were taken into account in order to evaluate the culture condition effect. Our results showed that the total hemocyte counts of Chinese mitten crab were about 2.5 × 10(7) cells ml(-1), and three subpopulations of hemocytes were distinguished as granulocytes (43.46 ± 4.98%), semigranulocytes (31.04 ± 1.95%), and hyalinocytes (25.50 ± 4.89%). The optimal culture condition for primary hemocytes of Chinese mitten crab was 3× L-15 medium, 1,100 mOsm kg(-1), pH 6.8 at 28°C. Hemocytes at optimal culture condition could retain a better morphology and higher survival rate: hemocytes retained a survival rate >60% after 5 d and >40% after 7 d. Furthermore, the hemocyte subpopulations were isolated by Percoll step gradient centrifugation and cultured in optimized hemocyte culture conditions. The results showed that hyalinocytes and semigranulocytes could maintain a survival rate of >50% after 15 d, while granulocytes only retained a survival rate of 26% after 5 d.

Where will the concept of lymph node micrometastasis advance?

There are several morphological pathways by which lymph node metastasis can arise: invasion into a deeper layer; detachment of tumor cells from the primary tumor; infiltration into intramural lymphatics; flow to extramural lymphatics; arrival to afferent lymphatics of a marginal sinus; movement to the lymph node cortex; and implantation of tumor cells into the node and formation of metastasis. Some cancer cells move from an efferent lymphatic vessel to the next lymph node. In terms of the first step toward lymph node metastasis, a small number of cancer cells is thought to be related to the formation of metastasis. Recent research into biological aspects has elucidated various tumor characteristics. What kinds of tumor cells have metastatic potential? Many molecules in the pathways toward lymphatic metastasis are thought to be related. Once tumor cells invade the lymphatics, can all cells implant into lymph nodes? Numerous immune cells are originally present in the lymph nodes, and such cells fight and defend against the invasion of bacteria, viruses, tumor cells, and so on. Thus, it is speculated that only certain special cancer cells can implant and grow to form an overt metastasis. What are these special cancer cells? The recent concept of epithelial-mesenchymal transition and the stem cell theory seems to offer an important key to solving the properties of tumor cells. Tumor cells able to seed a metastasis must presumably have the ability to avoid immune defense cells. Further basic studies will elucidate the mechanisms underlying lymphatic metastasis. Meanwhile, in the clinical field, lymph node metastasis offers an important prognostic factor for gastrointestinal (GI) cancer. The presence of tiny lymph node metastasis, in the form of lymph node micrometastasis (LNM) that is not detectable by routine histological examination, has been reported in carcinomas of various organs. Although overt lymph node metastasis is thought to be related to prognosis, what is the relationship between LNM and prognosis? Recent advances in techniques such as immunohistochemistry (IHC) and reverse transcription-polymerase chain reaction (RT-PCR) have allowed the detection of LNM. Recently, LNM has been defined by the criteria of TNM classification and roughly divided in some categories according to the size of the metastatic foci or the method of detection. Clinical evaluation of LNM is somewhat difficult, because of the differences in study designs and methods of detection, such as the sample size, tumor stage of patients, number of removed nodes based on the area of lymph node dissection, use of immunohistochemistry, RTPCR, or other methods, and the kinds of antibodies or primers used. Several articles have discussed the clinical significance of LNM of GI cancer. The present review articles summarize the current knowledge of LNMs in GI cancer from the perspectives of both molecular and biological characteristics and clinical aspects. These articles will be helpful as an overview of the current understanding of LNM and areas requiring further investigation.

Candida albicans secreted aspartic proteases 4-6 induce apoptosis of epithelial cells by a novel Trojan horse mechanism.

Systemic infection by the pathogenic yeast Candida albicans produces high mortality in immune-compromised people. Such infection starts with the penetration of the organism at the mucosal surfaces, facilitated by the secreted aspartic proteases (Saps) 4, 5, and 6. The functional mechanism of these virulence factors is unclear. We discovered that Saps 4-6 each contains amino acid motifs RGD/KGD to bind integrins on epithelial cell A549 and are internalized to endosomes and lysosomes. These processes are inhibited by RGD-containing peptides or by substituting RGD motifs of these Saps. The internalization of Saps 4-6 results in partial permeabilization of lysosomal membranes, measured by the redistribution of the lysosomal tropic dye acridine orange to the cytosol, and the triggering of apoptosis via caspase activation. Sap 2 and mutated Saps 4-6 contain no RGD motif, are ineffective in these processes, and a proteolytic inhibitor abolished Sap 4 activity in lysosome permeabilization. Same results were also seen for human tongue keratinocyte SCC-15 cells. Mucosal lesions from this fundamental new mechanism may permit C. albicans to enter the body and may be used to attack cells in immune defense during systemic infections. RGD-motif may also be incorporated in Sap inhibitors for Candidiasis drugs targeting to lysosomes.

Immune modulatory and antioxidant effects of melatonin in experimental periodontitis in rats

Melatonin is an important antioxidant, and through its anti-inflammatory effects it can control immune responses, oxidative stress, and defense cell infiltration. Periodontitis is a disease of the oral cavity and the generation of free radicals is an important consideration in this disease. Therefore, we examined the immune-modulatory and antioxidant roles of melatonin in the treatment of periodontitis. In all, 30 male Wistar rats were randomly divided into three groups: the control group, the periodontitis-induced (PED) group, and the periodontitis+melatonin treatment (MEL+PED) group. The control group received no treatment, whereas periodontitis was induced in both the PED and the MEL+PED groups, with the MEL+PED group being treated with systemic melatonin. For the periodontitis-induced groups, the rats' mandibular first molar teeth were ligatured (3-0 cotton) in a submarginal position for 4 weeks, and then the ligature was removed. After removal of the ligature, melatonin was administered only to the MEL+PED group (an ip dose of 10mg/kg body wt for 15 days at 11:00 PM each day). In the histological examination, the MEL+PED group, which received the melatonin, showed reduced inflammatory cytokines (IL-1β, from 97.47 to 84.24pg/ml; TNF-α, from 0.22530 to 0.22519pg/ml), regulated oxidative stress parameters (MDA, from 41,458 to 30,708nmol/g; GSH, from 18,166 to 25,858nmol/mg), and less periodontal tissue destruction (CEJ-PL, lingual, from 244.54 to 140.57μm; buccal, from 235.6 to 158.93μm; and CEJ-BC, lingual, from 383.65 to 287.76μm; buccal, from 391.92 to 296.12μm). From these findings we conclude that, even when periodontitis was induced, melatonin reduced the oxidative damage in the rats' periodontal tissue by inhibiting the inflammatory effects and by restoring the antioxidants.

Blockade of JNK and NFAT pathways attenuates orthopedic particle‐stimulated osteoclastogenesis of human osteoclast precursors and murine calvarial osteolysis

Particles released from orthopedic implants attract immune host defense cells to the bone-implant interface and contribute to development of inflammation. The inflammatory microenvironment supports recruitment and differentiation of osteoclasts, the primary culprit of osteolysis. Therefore, understanding the complex signals that contribute to osteoclastogenesis and osteolysis is a sensible approach to design strategies to inhibit bone loss. The signaling cascades that coordinate osteoclastogenesis have been widely investigated. These include MAP kinases, Akt/PI3K pathway, NF-κB signal transduction pathway, and NFAT pathway. We have recently reported that polymethylmethacrylate (PMMA) particles activate the NFAT pathway in murine osteoclast precursors and that NFAT inhibitors dose-dependently block PMMA-induced osteoclastogenesis. In the current study, we examined the role of JNK and NFATc1 in mice in response to PMMA particles using murine calvaria model. We show that locally administered MAPK/JNK inhibitor SP600125 and calcineurin/NFAT inhibitor cyclosporine-A effectively blocked PMMA-induced osteolysis in murine calvaria. To buttress the clinical relevance of JNK/NFATc1-based regulation of PMMA-induced osteoclastogenesis, we evaluated the effect of PMMA using human macrophages. We demonstrate that SP600125 and cyclosporine-A abolished particle-induced osteoclastogenesis in human osteoclast progenitors retrieved from patients undergoing total hip replacement. Thus JNK and NFATc1 appear to act as significant mediators of orthopedic particle-induced osteolysis in humans.

Neutrophil Function: From Mechanisms to Disease

Neutrophils are the most abundant white blood cells in circulation, and patients with congenital neutrophil deficiencies suffer from severe infections that are often fatal, underscoring the importance of these cells in immune defense. In spite of neutrophils' relevance in immunity, research on these cells has been hampered by their experimentally intractable nature. Here, we present a survey of basic neutrophil biology, with an emphasis on examples that highlight the function of neutrophils not only as professional killers, but also as instructors of the immune system in the context of infection and inflammatory disease. We focus on emerging issues in the field of neutrophil biology, address questions in this area that remain unanswered, and critically examine the experimental basis for common assumptions found in neutrophil literature.

Characterization of the immune defense related tissues, cells, and genes in amphioxus

Amphioxus is an important animal model for phylogenetic analysis, including comparative immunology. Exploring the immune system in amphioxus contributes to our understanding of the origin and evolution of the vertebrate immune system. We investigated the amphioxus immune system using ultrastructural examination and in situ hybridization. The expression patterns of TLR1 (toll-like receptor 1), C1Q (complement component 1, q subcomponent), ECSIT (evolutionarily conserved signaling intermediate in Toll pathways), SoxC, DDAHa (Dimethylarginine dimethylaminohydrolase a), and NOS (nitric oxide synthase) show that these genes play key roles in amphioxus immunity. Our results suggest that the epidermis and alimentary canal epithelium may play important roles in immune defense, while macrophages located in the coelom and so-called lymph spaces may also be crucial immune cells.

Involvement of the Cytokine MIF in the Snail Host Immune Response to the Parasite Schistosoma mansoni

We have identified and characterized a Macrophage Migration Inhibitory Factor (MIF) family member in the Lophotrochozoan invertebrate, Biomphalaria glabrata, the snail intermediate host of the human blood fluke Schistosoma mansoni. In mammals, MIF is a widely expressed pleiotropic cytokine with potent pro-inflammatory properties that controls cell functions such as gene expression, proliferation or apoptosis. Here we show that the MIF protein from B. glabrata (BgMIF) is expressed in circulating immune defense cells (hemocytes) of the snail as well as in the B. glabrata embryonic (Bge) cell line that has hemocyte-like features. Recombinant BgMIF (rBgMIF) induced cell proliferation and inhibited NO-dependent p53-mediated apoptosis in Bge cells. Moreover, knock-down of BgMIF expression in Bge cells interfered with the in vitro encapsulation of S. mansoni sporocysts. Furthermore, the in vivo knock-down of BgMIF prevented the changes in circulating hemocyte populations that occur in response to an infection by S. mansoni miracidia and led to a significant increase in the parasite burden of the snails. These results provide the first functional evidence that a MIF ortholog is involved in an invertebrate immune response towards a parasitic infection and highlight the importance of cytokines in invertebrate-parasite interactions.

Cutting Edge: Lung Mucosal Th17-Mediated Responses Induce Polymeric Ig Receptor Expression by the Airway Epithelium and Elevate Secretory IgA Levels

Polymeric Ig receptor (pIgR) is a central player in mucosal immunity that mediates the delivery of polymeric IgA and IgM to the apical surface of epithelial cells via transcytosis. Emerging evidence suggests that Th17 cells not only mediate autoimmunity but also play key roles in mucosal host defense against pathogens. We demonstrate that OVA-specific CD4(+) Th17 cells, in addition to causing neutrophilic inflammation in mice, mediated a pronounced influx of CD19(+) B cells into the lungs following Ag inhalation. Coincident with this recruitment was a striking induction in pIgR expression by the bronchial epithelium and a subsequent increase in airway IgM and secretory IgA levels. Intranasal administration of IL-17 revealed a crucial role for this cytokine in inducing pIgR expression by the epithelium. These findings support a key role for Th17 cells in pulmonary immune defense against respiratory pathogens by promoting pIgR-mediated transport of secretory IgA and IgM into the airway.

AIDS Vaccine Development: the Past, the Present, and the Future

AIDS was first reported in 1981 by Gottlieb MS et al at USC (University of California) Medical Center: Healthy homosexual men with pneumocystis carinii pneumonia and mucosal candidiasis had deficiency in CD4 T lymphocyte, a critical immune defense cell (1). In 1983, Dr. F. Barre-Sinoussi and L. Montagnier isolated a new human T-lymphotropic retrovirus, later named HIV-1(human immunodeficiency virus type 1) which turned out to be one of the causes of AIDS (2). Through their discovery, they received the 2008 Nobel Prize in Physiology or Medicine award. Discovery of the causative agent of AIDS had been the driving force to investigate its genomic structure, function, and replication mechanism. Most importantly, the development of a diagnostic kit contributed to the knowledge of AIDS as an infectious disease especially in the route of transmission. In addition, the development of antiretroviral drugs reduced the mortality of some HIV-infected individuals. However, high price and side effects of the current therapeutic drugs have not been beneficial for most AIDS patients. Thus, it has been generally accepted that the development of a low price and effective prophylactic AIDS vaccine is the only answer to stop the global epidemic. Despite tremendous efforts over the past 25 years, there is no promising candidate for an HIV vaccine. No one has even been able to design and develop a model leading to an effective vaccine. This review will introduce four major milestones in AIDS vaccine development to date which resulted in major social, economic and scientific impacts (Fig. 1). Figure 1 Time lines for HIV/AIDS pandemic and the development for AIDS vaccines. In 1989, the hopes for a HIV vaccine started from a highly effective formalin-inactivated whole SIV vaccine which was known to confer protection in macaques with AIDS (3). However, three years later, it was found that the protective effect was mediated by antigens (such as HLA and β2m) from the human cells used to grow the viral strain (4). In 1992, Dr. Ronald Desrosiers reported that a live attenuated SIV vaccine with a deletion in the nef gene can be efficient in treating AIDS of macaques (5). Unfortunately, three years later, Dr. Ruth Ruprecht found that this live attenuated vaccine had a safety issue in which the vaccine itself caused AIDS in neonatal macaques. For this reason, research into the development of a live attenuated vaccine has been no longer carried out (6). In 1990, Genentech reported that their recombinant glycoprotein gp120 subunit vaccine could induce protection in chimpanzees with HIV-1 (7). In phase I and II trial, they confirmed the safety and immunogenicity. However, when this vaccine was tested on 5,000 volunteers to test efficacy, vaccination failed to show reduction in HIV and thus was not able to become commercialized (8). Finally, Merck Co. reported that replication-incompetent adenoviral vaccine could elicit effective anti-viral T cell immune response against SHIV (pathogenic HIV-1 and SIV hybrid virus) in 2002 (9). Based on this positive result in monkeys, they entered clinical trial to evaluate the efficacy with almost 10,000 HIV-1 negative healthy volunteers. Disappointedly, in November 2007, they announced negative results on the interim report with 3,000 volunteers. This vaccine was ineffective in lowering plasma viremia postinfection and increased the risk of acquiring HIV-1 infection; therefore, further study on the vaccine was not pursued (10). There were five major vaccines introduced as possible treatments for AIDS: killed vaccine, live-attenuated vaccine, subunit vaccine, vectored vaccine, and DNA vaccine (Table I). Among them, DNA vaccine is the most promising AIDS vaccine since it was the only one that could provide a safe and protective immunity against HIV. Despite the safety concerns of the live attenuated vaccine, it is currently the only vaccine that is capable of inducing a protective immunity. Hence, the vaccine that has similar qualities and induces a strong response of the immune system similar to that of the live attenuated vaccine is the most probable to become a successful AIDS vaccine. In this regard, the fact that the DNA vaccine with electroporation (EP) does not have a vectored immunity makes it an excellent candidate because it can induce antibodies and a T cell response by continuous injections which are as powerful as live the attenuated vaccine. Therefore, there are high expectations for DNA vaccine with EP to develop successful AIDS vaccines commercially available in the near future. Table I The Potential of the five major AIDS vaccine candidates In order to develop an effective DNA vaccine with EP, the vaccine candidate should be evaluated thoroughly in terms of protective immunity in a small number of volunteers before entering large-scale phase IIb~III efficacy trials. More importantly, even before considering any clinical trials in humans, the efficacy test should be evaluated in the appropriate SIVmac-rhesus macaque challenge model that closely resembles the human case.

Antimicrobial peptides are present in immune and host defense cells of the human respiratory and gastroinstestinal tracts

Previous studies have implicated antimicrobial peptides in the host defense of the mammalian intestinal and respiratory tract. The aim of the present study has been to characterize further the expression of these molecules in non-epithelial cells of the human pulmonary and digestive systems by detailed immunohistochemical analysis of the small and large bowel and of the large airways and lung parenchyma. Additionally, cells obtained from bronchoalveolar lavage were analyzed by fluorescent activated cell sorting and immunostaining of cytospin preparations. hBD-1, hBD-2, and LL-37 were detected in lymphocytes and macrophages in the large airways, lung parenchyma, duodenum, and colon. Lymphocytes positive for the peptides revealed a staining pattern and distribution that largely matched that of CD3-positive and CD8-positive T-cells. Macrophages with positive staining for the antimicrobial peptides also stained positively for CD68 and CD74. In view of the morphology of the LL-37-positive and hBD-2-positive mucosal lymphocytes, they are probably also B-cells. Thus, antimicrobial peptides of the defensin and cathelicidin families are present in a variety of non-epithelial cells of mucosal organs. These findings confirm that antimicrobial peptides have multiple functions in the biology of the mucosa of these organs.

Keratinocyte production of cathelicidin provides direct activity against bacterial skin pathogens.

Immune defense at an interface with the external environment reflects the functions of physical and chemical barriers provided by epithelial and immune cells. Resident epithelial cells, such as keratinocytes, produce numerous peptides with direct antimicrobial activity but also provide a physical barrier against invading pathogens and signal the recruitment of circulating immune cells, such as neutrophils. Antimicrobial peptides such as cathelicidin are produced constitutively by neutrophils and are inducible in keratinocytes in response to infection. The multiplicity of antimicrobial peptides and their cellular sources has resulted in an incomplete understanding of the role of cathelicidin production by epithelial cells in cutaneous immune defense. Therefore, this study sought to evaluate keratinocyte antimicrobial activity and the potential contribution of keratinocyte cathelicidin to host protection against two leading human skin pathogens. Wild-type mice and those with a targeted deletion of the cathelicidin gene, Cnlp, were rendered neutropenic prior to cutaneous infection. Interestingly, Cnlp-deficient mice remained more susceptible to group A streptococcus infection than mice with Cnlp intact, suggesting the involvement of epithelial cell-derived cathelicidin in host immune defense. Keratinocytes were then isolated in culture and found to inhibit the growth of Staphylococcus aureus, an effect that was partially dependent on their ability to synthesize and activate cathelicidin. Further, lentivirus-mediated delivery of activated human cathelicidin enhanced keratinocyte antimicrobial activity. Combined, these data illustrate the potential contribution of keratinocyte cathelicidin to the innate immune defense of skin against bacterial pathogens and highlight the need to consider epithelial antimicrobial function in the diagnosis and therapy of skin infection.

Mutual interference of HIV and natural killer cell-mediated immune response

Natural killer (NK) cells represent important early effector cells in innate immune defense as they exert their functions without prior sensitization. They participate in regulation of innate and adaptive immune responses and hematopoiesis by producing various cytokines and chemokines. In addition, NK cells lyse virally infected and malignant cells raising them to multifunctional members of the first line of defense. Unlike other lymphocytes they lack specific antigen receptors. They rather bind cells using ubiquitous molecules and communicate via a pattern of receptors specific for MHC-I molecules with their counterparts. In general, successful binding of the receptors delivers an inhibitory signal to NK cells thus sparing the target cell from lysis. In contrast, down-regulated or altered MHC-I expression as frequently observed during virus infection or on malignant cells prevents ligation of inhibitory receptors and MHC-I paralyzing inhibition and thus inducing lysis of the target cell. In human immunodeficiency virus (HIV) infection NK cells are of central importance since they can combat viral infection itself and opportunistic pathogens like fungi and protozoa that usually spread during the course of HIV infection. However, various studies have reported alterations in HIV patients affecting NK cell numbers and functions that might negatively influence course and severity of the disease. This review will focus on the mutual interference of NK cells and the HI virus.