Cysticercosis: cellular immune responses during primary and secondary infection

Immune reactions to cysticercosis have been extensively studied in mice. The lack of significant lymphocyte infiltration into the livers of infected mice and the obvious role of antibodies in rejection has led to the general conclusion that cellular reactions do not play a role in protection against this disease. In contrast, the present study examining the immune response to cestode infections in a large animal model (sheep) revealed the presence of a massive and highly organized cellular infiltration in the livers after a secondary Taenia hydatigena infection. The majority of the infiltrating lymphocytes were of the CD4+ phenotype with much fewer CD8+ cells present. While most gamma delta-TCR+ cells in peripheral blood are SBU-T19+, the majority of gamma delta-TCR+ lymphocytes in the liver lesions are SBU-T19- suggesting selective migration of these cells into the lesions. In contrast to the diffuse distribution of T cells in the lesions, B cells were present as distinct aggregates. In primary T. hydatigena infections, host class I and class II MHC antigens were shown, for the first time in cestode infections, to be absorbed onto the surface of the metacestode bladderwall indicating their possible involvement in parasite survival. No immune reactions were observed close to the parasite although lymphocytes and eosinophils were infiltrating the adjacent portal tract areas. Most lymphocytes in both primary and secondary infections were positive for MHC class II antigens suggesting selective recruitment of activated cells to the site of infection. Significant changes in relative and absolute numbers of lymphocyte subpopulations were also observed in the draining hepatic lymph nodes dominated by a massive increase of B cells. In contrast, at the peak of local cellular infiltration, no changes in lymphocyte subpopulations were observed in peripheral blood showing the limited usefulness of this compartment in studying cellular changes in localized infections. The vigorous cellular response observed in the livers of sheep contrasts sharply with the lack of lymphocyte infiltration reported in mice indicating that small animal models may not be appropriate to study cellular responses to cysticercosis in large animals and man.     

Immunopathogenesis: role of innate and adaptive immune responses

Hepatitis B virus (HBV) infection in immunocompetent adults usually results in a self-limited, transient liver disease and viral clearance, with only a small percentage (5 to 10%) developing chronic hepatitis associated with viral persistence. In contrast, when neonates are infected, more than 90% become persistently infected, suffering differing degrees of chronic liver disease. Activation of immunity plays a central role in host-virus interactions, greatly influencing viral replication and the clinical outcome of infection. Although all of the specific mechanisms and consequences of this interaction have not been elucidated, the purpose of this article is to describe the basic arms of the immune system as they interact with the HBV and describe the present state of knowledge in this area. These arms may be divided broadly into innate and specific immune responses, and they have different roles and responses in acute and chronic infection.     

Early syphilis in a man with a negative Treponema pallidum enzyme immunoassay-IgM

Most serological tests for syphilis rely on an individual's ability to produce antibodies. A single screening test may be unreliable for screening in those with primary immunodeficiency. We present the first reported case of primary and secondary syphilis with negative Treponema pallidum enzyme immunoassay-IgM and Venereal Disease Research Laboratory tests in a man with common variable immunodeficiency.     

Antigens of Treponema pallidum recognized by IgG and IgM antibodies during syphilis in humans

IgG and IgM antibody specificities for antigens of Treponema pallidum Nichols strain were determined by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the western blot technique in sera from patients with untreated syphilis, normal persons, persons with biologic false-positive tests for syphilis, and sexual contacts of persons with infectious syphilis. IgG reactivities of sera from individuals with primary syphilis varied considerably but consistently exhibited strong reactivity to a 48-kilodalton band. Sera from patients with secondary and early latent syphilis uniformly demonstrated reactivity to 22 separate polypeptide antigens; decreased reactivity was seen in late latent syphilis. Normal and biologic false-positive sera showed weak IgG reactivity against none to 12 polypeptides. Sera from asymptomatic contacts of persons with infectious syphilis showed reactivity to a varying number of treponemal antigens, including some reactions not seen with normal sera. IgM reactivity was most prominent in secondary syphilis but was demonstrable at all stages of disease.     

Complement activation pathways: a bridge between innate and adaptive immune responses in asthma

Although it is widely accepted that allergic asthma is driven by T helper type 2 (Th2)-polarized immune responses to innocuous environmental allergens, the mechanisms driving these aberrant immune responses remain elusive. Recent recognition of the importance of innate immune pathways in regulating adaptive immune responses have fueled investigation into the role of innate immune pathways in the pathogenesis of asthma. The phylogenetically ancient innate immune system, the complement system, is no exception. The emerging paradigm is that C3a production at the airway surface serves as a common pathway for the induction of Th2-mediated inflammatory responses to a variety of environmental triggers of asthma (i.e., allergens, pollutants, viral infections, cigarette smoke). In contrast, C5a plays a dual immunoregulatory role by protecting against the initial development of a Th2-polarized adaptive immune response via its ability to induce tolerogenic dendritic cell subsets. On the other hand, C5a drives type 2-mediated inflammatory responses once inflammation ensues. Thus, alterations in the balance of generation of the various components of the complement pathway either due to environmental exposure changes or genetic alterations in genes of the complement cascade may underlie the recent rise in asthma prevalence in westernized countries.     

Inflammaging decreases adaptive and innate immune responses in mice and humans

Both the innate and adaptive immune systems decline with age, causing greater susceptibility to infectious diseases and reduced responses to vaccination. Diseases are more severe in elderly than in young individuals and have a greater impact on health outcomes such as morbidity, disability and mortality. Aging is characterized by increased low-grade chronic inflammation, called “inflammaging”, measured by circulating levels of TNF-α, IL-6 and CRP, as well as by latent infections with viruses such as cytomegalovirus. Inflammaging has received considerable attention because it proposes a link between changes in immune cells and a number of diseases and syndromes typical of old age. In this review we aim at summarizing the current knowledge on pathways contributing to inflammaging, on immune responses down-regulated by inflammation and mechanisms proposed. The defects in the immune response of elderly individuals presented in this review should help to discover avenues for effective intervention to promote healthy aging.     

A candidate DNA vaccine elicits HCV specific humoral and cellular immune responses

AIM: TO investigate the immunogenicity of candidate DNA vaccine against hepatitis C virus (HCV) delivered by two plasmids expressing HCV envelope protein 1 (El) and envelope protein 2 (E2) antigens respectively and to study the effect of CpG adjuvant on this candidate vaccine.METHODS: Recombinant plasmJds expressing HCV EI and E2 antigens respectively were used to simultaneously inoculate mice with or without CpG adjuvant. Antisera were then collected and tJters of antJ-HCV antibodies were analyzed by ELISA. One month after the last injection, animals were sacrificed to prepare single-cell suspension of splenocytes.These cells were subjected to HCV antigen specific proliferaion assays and cytokine secretion assays to evaluate the cellular immune responses of the vaccinated animals.RESULTS: Antibody responses to HCV EI and E2 antigens were detected in vaccinated animals. Animals receiving CpG adjuvant had slightly lower titers of anti-HCV antibodies in the sera, while the splenocytes from these animals showed higher HCV-antigen specific proliferation. Analysis of cytokine secretion from the splenocytes was consistent with the above results. While no antigen-specific IL-4 secretion was detected for all vaccinated animals, HCV antigen-specific INF-γ, secretion was detected for the splenocytes of vaccinated animals. CpG adjuvant enhanced the secretion of INF-γ, but did not change the profile of IL-4 secretion.CONCLUSION: Vaccination of mice with plasmids encoding HCV E1 and E2 antigens induces humoral and cellular immune responses. CpG adjuvant significantly enhances the cellular immune response.     

Killer cell immunoglobulin-like receptors influence the innate and adaptive immune responses

Natural killer (NK) cells are a subset of lymphocytes which play a crucial role in early innate immune response against infection and tumor transformation. Furthermore, they secrete interferon- (IFN-) and tumor necrosis factor (TNF) prompting adaptive immunity. NK cells distinguish the unhealthy cells from the healthy ones through an array of cell-surface receptors. Human NK cells use inhibitory and activating killer cell Ig-like receptors (KIR) as primary probe to discriminate between healthy and unhealthy cells. The inhibitory KIRs recognize HLA class I molecules and trigger signals that stop NK killing. The activating KIRs are believed to recognize the determinants associated with infections and tumors, and trigger signals that activate NK killing. Therefore, the effector function of a given NK cell depends upon the receptors that it expresses and ligands that it recognizes on the targets. Genes encoding KIRs and HLA ligands are located on different chromosomes, and vary in number and type. The independent segregation of KIR and HLA genes results in variable KIR-HLA combinations in individuals, which may determine the individual's immunity and susceptibility to disease.     

Glycolipid alpha-C-galactosylceramide is a distinct inducer of dendritic cell function during innate and adaptive immune responses of mice

alpha-Galactosylceramide (alpha-GalCer) is the prototype compound for studying the presentation of glycolipids on CD1d molecules to natural killer T (NKT) lymphocytes. A single i.v. dose of glycolipid triggers a cascade of events involving the production of several cytokines over the course of a day, a short-lived activation of NKT and natural killer (NK) cells, and a more prolonged adaptive T cell immune response if certain antigens are given together with alpha-GalCer. We find that a recently described analogue, alpha-C-galactosylceramide (alpha-C-GalCer), more potently induces these innate and adaptive immune responses in mice. alpha-C-GalCer acts as a more effective trigger for IL-12 and IFN-gamma production, although it minimally elicits IL-4 and TNF-alpha release into the serum. Also, alpha-C-GalCer better mobilizes NKT and natural killer cells to resist B16 melanoma. To help understand these effects, we find that alpha-C-GalCer binds more stably to dendritic cells than alpha-GalCer and that dendritic cells loaded with alpha-C-GalCer induce larger and more long lasting NKT cell responses in vivo. When glycolipid is targeted to dendritic cells in spleen together with antigens in dying cells, such as irradiated tumor cells, alpha-C-GalCer is active as an adjuvant for T cell-mediated immunity at lower doses, just 20 ng per mouse, where it is also able to up-regulate the required CD40L costimulatory molecule on NKT cells. Therefore, alpha-C-GalCer represents a glycolipid that binds more stably to dendritic cells and acts as a more effective link between innate and adaptive immunity in vivo.     

Destructive osteomyelitis associated with early secondary syphilis in an HIV-positive patient diagnosed by Treponema pallidum DNA polymerase chain reaction

A 20-year old man who had sex with men (MSM) presented with destructive osteomyelitis of the sternal bone and diffuse maculopapular rash. During laboratory evaluation he was found to have secondary syphilis and HIV with viral load of 28,000 copies per milliliter and CD4 count of 251 cells per microliter. Surgical debridement and biopsy of the sternal bone was performed. The biopsy examination demonstrated bone necrosis with perivascular infiltration of plasma cells and lymphocytes and rare hystiocytes. No granulomatous lesions were identified and acid-fast, fungal, silver, and Gram's stains did not show any organism. All cultures were negative. Real-time polymerase chain reaction (PCR) using probes targeting a pathogen-specific and highly conserved TpN47 gene of Treponema pallidum was performed on the DNA, extracted from the biopsy specimen and T. pallidum amplicons were detected. Patient was initially treated empirically with vancomycin, piperacillin/tazobactam and intravenous aqueous penicillin G. After confirming the diagnosis he completed 2 weeks of intravenous aqueous penicillin G treatment with resolution of osteomyelitis confirmed at follow-up visit after 6 weeks. Osteomyelitis is a rarely described manifestation of secondary syphilis. To the best of our knowledge, this is the first case of using T. pallidum DNA PCR to confirm the diagnosis of syphilitic osteitis. We suggest that osteomyelitis may be an underrecognized problem in patients with secondary syphilis, especially in HIV-coinfected individuals and PCR seems to be a valuable method in confirming the diagnosis.     

Molecular subtyping of Treponema pallidum in an Arizona County with increasing syphilis morbidity: use of specimens from ulcers and blood

A molecular-based subtyping system for Treponema pallidum was used during an investigation of increasing syphilis in Maricopa County, Arizona. Genital ulcer or whole blood specimens from patients with syphilis were assayed by a polymerase chain reaction (PCR) amplification of a T. pallidum DNA polymerase I gene. Positive specimens were typed on the basis of PCR amplification of 2 variable genes. In all, 41 (93%) of 44 of ulcer specimens and 4 (27%) of 15 blood specimens yielded typeable T. pallidum DNA. Twenty-four (53%) of 45 specimens were subtype 14f; other subtypes identified included 4f, 4i, 5f, 12a, 12f, 14a, 14d, 14e, and 14i. Only 2 specimens were from epidemiologically linked patients. This investigation demonstrates that multiple subtypes of T. pallidum can be found in an area with high syphilis morbidity, although 1 subtype (14f) was predominant. Four typeable specimens were from blood, a newly identified specimen source for subtyping.     

Molecular analysis of the fetal IgM response to Treponema pallidum antigens: implications for improved serodiagnosis of congenital syphilis

Western blot analysis of the fetal IgM response to Treponema pallidum antigens was examined among 39 pairs of maternal/infant sera; this included 12 mothers and infants with active syphilis (group I), 9 mothers with active syphilis and their infants with uncertain infection (group II), and 18 mothers treated for syphilis before delivery and their asymptomatic infants (group III). A fetal IgM response to T. pallidum antigens with apparent molecular masses of 72, 47, 45, 42, 37, 17, and 15 kDa was observed among sera of infants with congenital syphilis. Fractionation of sera into IgM and IgG components by high performance liquid chromatography confirmed that fetal IgM antibodies in every case were directed specifically against a 47-kDa antigen. Two asymptomatic infants from group II also showed serum IgM reactivities with the 47-kDa antigen, thereby appearing to confirm in utero infection. The combined data suggest that fetal serum IgM reactivity with the 47-kDa antigen of T. pallidum can be used as an important molecular marker for the diagnosis of congenital syphilis.     

A centralized gene-based HIV-1 vaccine elicits broad cross-clade cellular immune responses in rhesus monkeys

One of the major challenges that must be met in developing an HIV-1 vaccine is devising a strategy to generate cellular immunity with sufficient breadth to deal with the extraordinary genetic diversity of the virus. Amino acids in the envelopes of viruses from the same clade can differ by >15%, and those from different clades can differ by >30%. It has been proposed that creating immunogens using centralized HIV-1 gene sequences might provide a practical solution to this problem. Such centralized genes can be generated by employing a number of different strategies: consensus, ancestral, or center of tree sequences. These computer-generated sequences are a shorter genetic distance from any two contemporary virus sequences than those contemporary sequences are from each other. The present study was initiated to evaluate the breadth of cellular immunity generated through immunization of rhesus monkeys with vaccine constructs expressing either an HIV-1 global consensus envelope sequence (CON-S) or a single patient isolate clade B envelope sequence (clade B). We show that vaccine immunogens expressing the single centralized gene CON-S generated cellular immune responses with significantly increased breadth compared with immunogens expressing a wild-type virus gene. In fact, CON-S immunogens elicited cellular immune responses to 3- to 4-fold more discrete epitopes of the envelope proteins from clades A, C, and G than did clade B immunogens. These findings suggest that immunization with centralized genes is a promising vaccine strategy for developing a global vaccine for HIV-1 as well as vaccines for other genetically diverse viruses.     

CD14: a bridge between innate immunity and adaptive IgE responses

Total IgE levels are known to be under genetic control. Linkage studies have indicated that one or more loci on chromosome 5q may control total IgE, as well as asthma and bronchial hyperresponsiveness to non-specific stimuli. Our group has undertaken a systematic analysis of chromosome 5q, and has recently characterized five single nucleotide polymorphisms at position -1619, -1359, -1145, -809, and -159 in the promoter of the gene encoding CD14, the myeloid pattern recognition receptor that is critical for efficient innate immune responses to lipopolysaccharide and bacterial ligands. Individuals homozygous for the three major CD14 haplotypes found in the Children Respiratory Study population (n = 390) were analyzed for serum levels of total IgE and soluble CD14. A strong inverse correlation was found between these two parameters, i.e. carriers of the -1359T/-1145A/-159C haplotype had the highest levels of IgE, and the lowest levels of sCD14. Conversely, carriers of the -1359G/-1145G/-159T haplotype had the highest levels of sCD14 and the lowest IgE values. Our results suggest that genetic variation in CD14, a key gene of innate immunity, may modulate the effects that exposure to bacterial ligands has on the development of Th2 responses.