Eimeria coecicola Cheissin 1947: endogenous development in gut-associated lymphoid tissue

Coccidia-free rabbits were inoculated with different doses of a pure strain of Eimeria coecicola and samples of gut were taken at 80, 96, 112, 128, 144, and 160 h postinoculation. The use of a very low infective dose (2-20 oocysts) was sufficient to study the last merogony. The number of merozoites in meronts increased when the infective dose decreased. Only the first merogony of this coccidium in lymphocytes or M-cells of gut-associated lymphoid tissue (GALT) has previously been described. Three other generations of meronts are described herein. All these endogenous stages were observed in the epithelium of the vermiform appendix, sacculus rotundus, and Peyer's patches, especially at the bases of the domes. However, in heavily infected tissues the gamonts were seen throughout the epithelium of the GALT. The third- and fourth-generation meronts were of two types. As in other eimerian species of the rabbit, type A meronts produced thick polynucleated merozoites, whereas type B meronts gave rise to large numbers of thin merozoites with one nucleus. Microgamonts were polynucleated and less numerous than macrogamonts. Type A meronts were also polynucleated and less numerous at the end of the merogony. Therefore, types A and B could correspond to a sexual phenotype differentiation occuring during the two asexual phases of multiplication.     

Expression and immune response to foreign epitopes in bacteria. Perspectives for live vaccine development

We previously developed a general procedure which allows the genetic coupling of a chosen foreign linear epitope in different regions of a carrier protein. By using as carriers, two bacterial envelope proteins, the LamB and MalE proteins of E. coli K12, we were able to express the same epitope in different sites of the two proteins and in different compartments of the bacteria. This allowed us to analyze the influence of the localization in E. coli cells of a foreign B-cell epitope on the induction of specific antibody responses, and the role of the molecular environment on the immunological properties of foreign B- or T-cell epitopes, using either purified hybrid proteins or live recombinant bacteria. Several LamB and MalE hybrid proteins were expressed in the aroA attenuated strain of S. typhimurium, SL3261. Immunizations of mice with live recombinant bacteria by the intravenous route showed that it was possible to induce humoral responses against inserted foreign sequences. In order to improve the in vivo stability of the plasmids carrying the different contructions, and to increase the amounts of recombinant LamB and MalE hybrid proteins expressed in vivo, the LamB and malE genes were placed under the control of the anaerobically inducible pnirBpromoter control. The genetic factors susceptible of influencing the immune response to recombinant Salmonella in mice were also studied.     

Intestinal epithelial cells down-regulate macrophage tumor necrosis factor-alpha secretion: a mechanism for immune homeostasis in the gut-associated lymphoid tissue

BACKGROUND: The gut lumen contains more than 10(6) organisms per gram of luminal contents. The mechanisms that limit the response of macrophages in the lamina propria to these microbial antigens are unknown, although an intrinsic defect in this mechanism may contribute to the development of inflammatory bowel disease. Intestinal epithelial cells (IEC) may play an important role in mediating tonic down-regulation of local immune cell activation. The purpose of this study was to discern whether IEC might modulate macrophage activation in response to a variety of microbial stimuli. METHODS: Thioglycollate-elicited murine peritoneal macrophages were activated by endotoxin, zymosan, Escherichia coli, and Candida albicans in the presence or absence of IEC from the rat intestinal epithelial cell line IEC-6. Macrophage tumor necrosis factor-alpha (TNF-alpha) secretion was determined by enzyme-linked immunosorbent assay. RESULTS: Lipopolysaccharide or zymosan-activated macrophages in coculture with IEC secreted significantly less TNF-alpha than macrophages cultured alone. The inhibitory effect of the IEC was dependent on their activation by lipopolysaccharide. Interleukin-1 alpha production was not affected. IEC-mediated suppression of macrophage TNF-alpha secretion was reversed by indomethacin but not by neutralizing antibody to TGF-beta. CONCLUSIONS: Lipopolysaccharide-activated IEC down-regulate macrophage TNF-alpha secretion in response to microbial stimuli through a prostanoid-mediated mechanism. IEC may mediate tonic down-regulation of immune cell activation in the gut-associated lymphoid tissue and may thereby regulate local and systemic inflammatory responses.     

In situ immune response in gut-associated lymphoid tissue (GALT) following oral antigen in TCR-transgenic mice

Oral administration of Ag results in systemic hyporesponsiveness termed oral tolerance. The regulatory cells induced by oral Ag are effective in the suppression of Th1-type autoimmune diseases. We examined the cytokine microenvironment in gut-associated lymphoid tissue in response to orally administered OVA in OVA TCR-transgenic mice. Mice were fed a low (0.5 mg) or high (500 mg) dose of OVA one time or five times. Immunohistochemical analysis demonstrated increased IL-4, IL-10, and TGF-beta in the gut within 6 h of a low-dose feeding and after five low-dose or high-dose feedings. IFN-gamma and IL-2 either decreased or showed no change, with the exception of a small transient increase in IL-2 at 6 h after a low dose. Increases in IL-4 and IL-10 were found in the dome of the Peyer's patch, and increases in TGF-beta were observed in the interfollicular region and the villi. IL-10 was also substantially increased in the villi. IL-4 and IL-10 were produced predominately by CD4+ T cells. TGF-beta was found predominately in macrophages and CD4+ T cells. Peyer's patches had a marked up-regulation of TGF-beta mRNA as measured by RT-PCR. These results demonstrate the differential activation of cytokine production in discrete regions of gut-associated lymphoid tissue. The induction of cytokines known to inhibit autoimmune disease at the site of Ag absorption indicates an important role for the mucosal immune system in the establishment of oral tolerance.     

New approaches in vaccine development

BACKGROUND: A prospective study was carried out at the University Hospital, Kuala Lumpur to determine the cervical carriage rate of Ureaplasma urealyticum and Mycoplasma hominis among healthy pregnant women at delivery and the incidence of nasopharyngeal colonisation among their infants. PATIENTS: Sixty mother and baby pairs were examined. RESULTS: Cervical colonisation among the mothers was found to be 56.7% for U.urealyticum and 17.7% for M.hominis. The transmission rate to their infants was 88.2% and 30% for U.urealyticum and M.hominis respectively. CONCLUSION: There was no statistically significant difference in the maternal colonisation rates according to ethnic group, parity and past history of abortion. All U.urealyticum isolates in our study were sensitive to erythromycin but about one-third were resistant to tetracycline and ciprofloxacin and 26.5% were resistant to minocycline.     

Genetic rearrangements leading to disruption of heterologous gene expression in mycobacteria: an observation with Escherichia coli beta-galactosidase in Mycobacterium smegmatis and its implication in vaccine development

Different mycobacteria carrying cloned genes for heterologous protective antigens have been proposed as vaccine vehicles. In this study, the stability of the expression of beta-galactosidase was studied in Mycobacterium smegmatis using integrative (pMV361::lacZ) and replicative (pMV261::lacZ) vectors. Recombinant M. smegmatis forms blue colonies on X-gal plates. Occasional white mutants encountered while plating on X-gal plates were genetically analysed. The loss of lacZ phenotype was due to insertion of an IS element in lacZ gene of integrative vector whereas in case of replicative vectors, loss of lacZ phenotype was due to deletions of different sizes in the lacZ gene and the Phsp60 promoter region. The frequency of such events was rare, 1.7 x 10(-5) in integrative vector and 2 x 10(-3) in the case of replicative vector. The integrative vector seemed more stable in terms of expression of foreign genes in mycobacteria. Hence, the rearrangements reported in the present study warrant serious consideration before implementing mycobacteria as recombinant vaccines.     

Progress in the development of Lactococcus lactis as a recombinant mucosal vaccine delivery system

Statutory authority for retaking absconders from mental hospitals has existed ever since county asylums (the forerunners of mental hospitals) were first built in the nineteenth century. Today under the Mental Health Act, 1983 that 'right' can be exercised by the police, mental hospital staff, approved social workers, etc. This article looks at jurisprudential aspects of that 'right'. It points out that 'right' actually means 'power' (not 'privilege', 'claim' or 'immunity'). In addition it argues that the Mental Health Act, 1983 does only confer a power (rather than impose a duty) to retake absconders from mental hospitals and that there should not be statutory or other imposition of such a duty.     

Delivery of epitopes by the Salmonella type III secretion system for vaccine development

Avirulent strains of Salmonella typhimurium are being considered as antigen delivery vectors. During its intracellular stage in the host, S. typhimurium resides within a membrane-bound compartment and is not an efficient inducer of class I-restricted immune responses. Viral epitopes were successfully delivered to the host-cell cytosol by using the type III protein secretion system of S. typhimurium. This resulted in class I-restricted immune responses that protected vaccinated animals against lethal infection. This approach may allow the efficient use of S. typhimurium as an antigen delivery system to control infections by pathogens that require this type of immune response for protection.     

Papillomaviruses and cervical cancer: pathogenesis and vaccine development

A subset of human papillomaviruses (HPVs) has been implicated as the principal etiologic agents of cervical cancer. Cervical cancers consistently retain and express two of the viral genes, E6 and E7. Although infection with HPV seems to be necessary, other factors, such as cellular immune function, play an important role in determining whether cervical infection will regress, persist, or progress to cancer. The close relationship between viral infection and cancer makes HPV an attractive target for prophylactic and therapeutic vaccines. Candidate vaccines have been shown to have efficacy in animal models, and human clinical trials are planned or in progress.     

A role for tumor necrosis factor receptor type 1 in gut-associated lymphoid tissue development: genetic evidence of synergism with lymphotoxin beta

Lymphotoxin alpha (LTalpha) signals via tumor necrosis factor receptors (TNFRs) as a homotrimer and via lymphotoxin beta receptor (LTbetaR) as a heterotrimeric LTalpha1beta2 complex. LTalpha-deficient mice lack all lymph nodes (LNs) and Peyer's patches (PPs), and yet LTbeta-deficient mice and TNFR-deficient mice have cervical and mesenteric LN. We now show that mice made deficient in both LTbeta and TNFR type 1 (TNFR1) lack all LNs, revealing redundancy or synergism between TNFR1 and LTbeta, acting presumably via LTbetaR. A complete lack of only PPs in mice heterozygous for both ltalpha and ltbeta, but not ltalpha or ltbeta alone, suggests a similar two-ligand phenomenon in PP development and may explain the incomplete lack of PPs seen in tnfr1-/- mice.     

Effects of zinc supplementation on the immune system and on antibody response to multivalent influenza vaccine in hemodialysis patients

BACKGROUND: It has been theorized that fetal myelomeningocele repair may reduce ongoing intrauterine injury and perhaps allow healing and regeneration of dysplastic neural tissue. We report on the postnatal imaging studies of the first 4 patients to have undergone intrauterine myelomeningocele repair at our institution. METHODS: Each of the 4 patients underwent postnatal sonographic and MRI. In addition, the postnatal ultrasounds of these 4 were compared to a group of retrospective controls. RESULTS: MRI scans of the 4 experimental subjects revealed no evidence of hindbrain herniation while other stigmata of the Chiari-II malformation persisted. In comparison to the retrospective controls this absence of herniation was distinctly unusual. CONCLUSION: Intrauterine myelomeningocele repair may reduce the degree of hindbrain herniation normally seen in patients with myelomeningocele. This raises the possibility that intrauterine repair may decrease the morbidity associated with the Chiari type-II malformation including brainstem dysfunction, hydrocephalus and syringomyelia.     

Recent progress in live influenza vaccine development]

As live influenza vaccine, cold-adapted influenza virus vaccines (ca vaccine) have been extensively investigated in both the U.S and Russia. In Russia it has been licensed since 1988 and it is going to be licensed in the U.S. within a year or two. In general, the ca vaccine is more effective in seronegative population than the inactivated vaccine. In seropositive adult population, both are equally effective. In the elderly, inactivated vaccine is better than the live vaccine. In Japan, clinical trials were also conducted with the American ca vaccines. Although the efficacy was confirmed in limited locations, the vaccine could not be evaluated from the point of license approval because big epidemic did not occur during the studies.     

Nutrition and the immune system: an introduction

Nutrition is a critical determinant of immune responses and malnutrition the most common cause of immunodeficiency worldwide. Protein-energy malnutrition is associated with a significant impairment of cell-mediated immunity, phagocyte function, complement system, secretory immunoglobulin A antibody concentrations, and cytokine production. Deficiency of single nutrients also results in altered immune responses: this is observed even when the deficiency state is relatively mild. Of the micronutrients, zinc; selenium; iron; copper; vitamins A, C, E, and B-6; and folic acid have important influences on immune responses. Overnutrition and obesity also reduce immunity. Low-birth-weight infants have a prolonged impairment of cell-mediated immunity that can be partly restored by providing extra amounts of dietary zinc. In the elderly, impaired immunity can be enhanced by modest amounts of a combination of micronutrients. These findings have considerable practical and public health significance.     

Host-pathogen interaction in amebiasis and progress in vaccine development

Entamoeba histolytica, the causative organism of invasive intestinal and extraintestinal amebiasis, infects approximately 50 million people each year, causing an estimated 40 to 100 thousand deaths annually. Because amebae only infect humans and some higher non-human primates, an anti-amebic vaccine could theoretically eradicate the organism. Uncontrolled epidemiologic studies indicate that acquired immunity to amebic infection probably occurs and that such a vaccine might be feasible. Application of molecular biologic techniques has led to rapid progress towards understanding how Entamoeba histolytica causes disease, and to the identification of several amebic proteins associated with virulence. These proteins are now being evaluated as potential vaccine components. Parenteral and oral vaccine preparations containing recombinant amebic proteins have been effective in preventing disease in a gerbil model of amebic liver abscess. Although systemic and mucosal cellular and humoral immunity both appear to play a role in protection against Entamoeba histolytica, the relative importance of each in the human immune response remains unknown. No animal model of intestinal amebiasis currently exists, moreover, so it has been impossible to evaluate protection against colonization and colitis. Further investigation of the fundamental mechanisms by which Entamoeba histolytica causes disease and of the human immune response to amebic infection is necessary to assess the true feasibility of an anti-amebic vaccine.     

Changes in the aging immune system

We describe a solid-state, silicon integrated, bidirectional flow sensor for respiratory applications. The sensor is a thermal vector sensor. The electronic circuitry for obtaining bidirectional sensitivity is presented together with actual application to a healthy volunteer put on mechanical ventilation. The sensor's input flow range is from -60 to +60 L/min, and its rise-time is < or = 40 ms and fall-time is < or = 60 ms. The effect of changes in gas composition as used in mechanically ventilated patients on the sensor output signal are estimated to be less than 2%. The temperature sensitivity is about -1.5% per degree Celsius.