A highly attenuated recombinant human respiratory syncytial virus lacking the G protein induces long-lasting protection in cotton rats

Background

Respiratory syncytial virus (RSV) is a primary cause of serious lower respiratory tract illness for which there is still no safe and effective vaccine available. Using reverse genetics, recombinant (r)RSV and an rRSV lacking the G gene (ΔG) were constructed based on a clinical RSV isolate (strain 98-25147-X).

Results

Growth of both recombinant viruses was equivalent to that of wild type virus in Vero cells, but was reduced in human epithelial cells like Hep-2. Replication in cotton rat lungs could not be detected for ΔG, while rRSV was 100-fold attenuated compared to wild type virus. Upon single dose intranasal administration in cotton rats, both recombinant viruses developed high levels of neutralizing antibodies and conferred comparable long-lasting protection against RSV challenge; protection against replication in the lungs lasted at least 147 days and protection against pulmonary inflammation lasted at least 75 days.

Conclusion

Collectively, the data indicate that a single dose immunization with the highly attenuated ΔG as well as the attenuated rRSV conferred long term protection in the cotton rat against subsequent RSV challenge, without inducing vaccine enhanced pathology. Since ΔG is not likely to revert to a less attenuated phenotype, we plan to evaluate this deletion mutant further and to investigate its potential as a vaccine candidate against RSV infection.

Lung pathology and immediate hypersensitivity in a mouse model after vaccination with pertussis vaccines and challenge with Bordetella pertussis

While evaluating vaccine efficacy against clinical Bordetella pertussis isolates in mice, after challenge vaccinated mice showed increased lung pathology with eosinophilia, compared to challenged, non-vaccinated animals. This led us to study bacterial clearance, lung pathology, lung TNF-alpha expression, and parameters of immediate hypersensitivity (IH), being serum IgE levels, eosinophil numbers in the bronchoalveolar lavage fluid, and ex vivo IL-4, IL-5, IL-10, IL-13, and IFN-gamma production by the bronchial lymph node cells. BALB/c mice received a combined Diphtheria (D), Tetanus (T), Poliomyelitis, and whole-cell Pertussis vaccine (WCV), a combined D, T, and three-component acellular Pertussis vaccine (ACV), aluminium hydroxide adjuvant, or PBS, 28 and 14 days before B. pertussis infection. Similarly treated non-infected mice were taken as a control. Infection induced pathology; this induction was stronger after (especially WCV) vaccination. WCV but not ACV vaccination induced TNF-alpha expression after challenge. After challenge, IH parameters were strongly increased by (especially ACV) vaccination. Vaccinated IL-4 KO mice showed similar clearance and pathology, in the absence of IgE and with reduced numbers of eosinophils. Vaccinated (Th1-deficient) T-bet KO mice showed reduced clearance and similar pathology. In summary, after challenge vaccination increased lung pathology, TNF-alpha expression (only WCV), and IH parameters. Th1 cells were critical for clearance.

Molecular evidence for association of chlamydiales bacteria with epitheliocystis in leafy seadragon (Phycodurus eques), silver perch (Bidyanus bidyanus), and barramundi (Lates calcarifer)

Epitheliocystis in leafy seadragon (Phycodurus eques), silver perch (Bidyanus bidyanus), and barramundi (Lates calcarifer), previously associated with chlamydial bacterial infection using ultrastructural analysis, was further investigated by using molecular and immunocytochemical methods. Morphologically, all three species showed epitheliocystis cysts in the gills, and barramundi also showed lymphocystis cysts in the skin. From gill cysts of all three species and from skin cysts of barramundi 16S rRNA gene fragments were amplified by PCR and sequenced, which clustered by phylogenetic analysis together with other chlamydia-like organisms in the order Chlamydiales in a lineage separate from the family Chlamydiaceae. By using in situ RNA hybridization, 16S rRNA Chlamydiales-specific sequences were detected in gill cysts of silver perch and in gill and skin cysts of barramundi. By applying immunocytochemistry, chlamydial antigens (lipopolysaccharide and/or membrane protein) were detected in gill cysts of leafy seadragon and in gill and skin cysts of barramundi, but not in gill cysts of silver perch. In conclusion, this is the first time epitheliocystis agents of leafy seadragon, silver perch and barramundi have been undoubtedly identified as belonging to bacteria of the order Chlamydiales by molecular methods. In addition, the results suggested that lymphocystis cysts, known to be caused by iridovirus infection, could be coinfected with the epitheliocystis agent.

Dechloromonas hortensis sp. nov. and strain ASK-1, two novel (per)chlorate-reducing bacteria, and taxonomic description of strain GR-1

Recent studies on the occurrence of (per)chlorate-reducing bacteria have resulted in the characterization of strains capable of dissimilatory (per)chlorate reduction. Phylogenetic analysis has shown that these bacteria are members of the Proteobacteria. Strains have been isolated from polluted and pristine sites, but only strains from polluted sites have been characterized in detail and deposited in culture collections. Herein we describe the isolation and characterization of perchlorate-reducing bacterium strain MA-1(T) and chlorate-reducing bacterium strain ASK-1, respectively isolated from a pristine and a chlorate-polluted site. Both isolates are members of the Proteobacteria. The 16S rRNA gene sequence similarity of MA-1(T) to Dechloromonas agitata DSM 13637(T) is 97.6%, but the relatedness in DNA-DNA reassociation is only 37%. Therefore, we propose to classify strain MA-1(T) (=DSM 15637(T)=ATCC BAA-776(T)) as the type strain of a novel species, Dechloromonas hortensis sp. nov. Strain ASK-1 and a previously described strain GR-1 show 100 and 99% 16S rRNA gene sequence similarity to Pseudomonas chloritidismutans DSM 13592(T) and Dechlorosoma suillum DSM 13638(T), respectively. DNA-DNA hybridization studies indicated that strains ASK-1 and GR-1 are related at the species level to P. chloritidismutans DSM 13592(T) (79%) and Dechlorosoma suillum DSM 13638(T) (85%), respectively. As suggested previously, Dechlorosoma suillum appears to be a later heterotypic synonym of Azospira oryzae. Although strain ASK-1 is identified as P. chloritidismutans, its morphology and growth requirements are different from those of the type strain.

Respiratory Syncytial Virus Infection of Monocyte-Derived Dendritic Cells Decreases Their Capacity to Activate CD4 T Cells

Respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infections in children, the elderly, and immune-compromised individuals. CD4 and CD8 T cells play a crucial role in the elimination of RSV from the infected lung, but T cell memory is not sufficient to completely prevent reinfections. The nature of the adaptive immune response depends on innate immune reactions initiated after interaction of invading pathogens with host APCs. For respiratory pathogens myeloid dendritic cell (DC) precursors that are located underneath the epithelial cell layer lining the airways may play a crucial role in primary activation of T cells and regulating their functional potential. In this study, we investigated the role of human monocyte-derived DC in RSV infection. We showed that monocyte-derived DC can be productively infected, which results in maturation of the DC judged by the up-regulation of CD80, CD83, CD86, and HLA class II molecules. However, RSV infection of DC caused impaired CD4 T cell activation characterized by a lower T cell proliferation and ablation of cytokine production in activated T cells. The suppressive effect was caused by an as yet unidentified soluble factor produced by RSV-infected DC.

Effect of clarithromycin treatment on Chlamydia pneumoniae in vascular tissue of patients with coronary artery disease: a randomized, double-blind, placebo-controlled trial

Several small clinical trials have indicated that antibiotic treatment of Chlamydia pneumoniae infection is associated with a better outcome in patients with coronary artery disease (CAD). It has not been demonstrated whether antibiotic treatment eradicates C. pneumoniae from vascular tissue. The aim of the present study was to assess the effect of clarithromycin on the presence of C. pneumoniae in the vascular tissue of patients with CAD. Patients who had CAD and who were waiting for coronary artery bypass graft surgery were enrolled in a randomized, double-blind, placebo-controlled trial. Patients were treated with clarithromycin at 500 mg or placebo once daily from the day of inclusion in the study until surgery. Several vascular tissue specimens were obtained during surgery. The presence of C. pneumoniae in vascular tissue specimens was examined by immunohistochemical staining (IHC) and two PCR assays. Chlamydia immunoglobulin G (IgG) titers were determined by an enzyme-linked immunosorbent assay at the time of inclusion in the study and 8 weeks after surgery. A total of 76 patients were included, and 180 vascular tissue specimens were obtained (80 specimens from the group treated with clarithromycin and 100 specimens from the group treated with placebo). Thirty-five patients received clarithromycin (mean duration, 27 days; standard deviation [SD], 12.2 days), and 41 patients received placebo (mean duration, 27 days; SD, 13.9 days). IHC detected the C. pneumoniae major outer membrane protein antigen in 73.8% of the specimens from the group treated with clarithromycin and 77.0% of the specimens from the group treated with placebo (P was not significant). Chlamydia lipopolysaccharide antigen was found in only one specimen from the group that received placebo. C. pneumoniae DNA was not detected in any specimen. Baseline Chlamydia-specific IgG titers were equally distributed in both groups and were not significantly different after treatment. There was no indication of an active C. pneumoniae infection in vascular tissue. Chlamydia-specific IgG titers remained unchanged throughout the study in both the antibiotic- and the placebo-treated patients.

Association of Bordetella pertussis with host immune cells in the mouse lung

Mouse models are frequently used to study immunity and pathogenesis to Bordetella pertussis infection. To improve the understanding of the mouse infection model, the influx of host cells and B. pertussis localisation in the lungs were evaluated. Furthermore, the roles of filamentous hemagglutinin (FHA) and fimbriae (Fim) in these processes were determined. B. pertussis infection stimulated the recruitment of polymorphonuclear granulocytes (PMN), alveolar macrophages, and lymphocytes. As determined by double immunofluorescence staining, 2 hr after infection most B. pertussis were free in the alveolar space, some were attached to alveolar epithelia, and some were associated with and phagocytosed by PMN. After 3 days, most bacteria were associated with and phagocytosed by macrophages, some by PMN. B. pertussis was shown not to be ingested by epithelial cells or associated with interstitial macrophages. B. pertussis mutants lacking expression of FHA or Fim were associated with and phagocytosed by the same cell types as parental bacteria. The Fim mutant, however, induced a more severe inflammation, and was cleared faster from the lungs compared to the parental strain and the FHA mutant. These results suggest that Fim does not affect bacterial localisation in the mouse lung, but does influence host immune mechanisms. Possibly, Fim may exert an anti-inflammatory function and thereby inhibit killing by macrophages.

Donor-specific tolerance in a murine model: the result of extra-thymic T cell deletion?

Previously, we established a murine model, that involves the engraftment of fully allogeneic T cell depleted donor bone marrow cells in sublethally irradiated and single dose anti-CD3 treated recipient mice. These mice developed permanent stable multilineage mixed chimerism and donor-specific tolerance without graft-versus-host disease. Recently, we have shown that donor-specific tolerance is not induced and/or maintained by clonal anergy, neither by a Th1/Th2 shift, nor by suppressor or other regulatory processes. In the present study, we investigated whether clonal deletion plays a role in tolerance induction in our model. We studied the kinetics of TCRVbeta8(+) T cells in BALB/c (H-2L(d+))-->dm2 (H-2L(d-)) chimeras, in which combination of mouse strains TCRVbeta8 predominates the anti-donor response. We found that TCRVbeta8(+) T cells were specifically deleted. To our surprise, this deletion was also found in mixed chimeras, thymectomized prior to the conditioning regimen. We conclude that clonal deletion plays a role in the establishment and maintenance of donor-specific tolerance, and that the thymus is not required for this process. In addition, confocal laser-scanning microscopy clearly showed the presence of abundant amounts of donor T cells and some donor antigen presenting cells in the small intestine in thymectomized chimeras and not in other organs, suggesting that T cell selection might take place in this organ in the absence of the thymus.

Ultrastructural characterization of effector-target interactions for human neonatal and adult NK cells reveals reduced intercellular surface contacts of neonatal cells

Limitations in neonatal natural killer (NK) cell responses may be associated with the less efficient newborn capacity to solve viral infections. Although these limitations have been extensively reported they are poorly characterized. Making use of the major histocompatibility complex (MHC) class I negative cell line K562, the parameters required for the initial events involved in neonatal NK/target cell interactions were determined and compared with adult blood NK cell/target cell interactions. Ultrastructural characterization of effector-target cell interactions revealed that neonatal NK cells are more strongly activated upon contact with K562 cells than adult blood NK cells. Furthermore, the neonatal capacity to establish contacts, in particular extensive contacts, is significantly reduced when compared with adult blood NK cells. However, no significant differences were found either in the cell surface expression levels or activation state of LFA-1, which could account for the reduced intercellular contacts. Because extensive contacts are crucial for effective immunologic synapse formation, these data suggest that a limited or nonsustained positive signaling may occur on neonatal NK cells, restricting their NK cell-mediated lysis capacity.

Autoreactivity against induced or upregulated abundant self-peptides in HLA-A*0201 following measles virus infection

Infectious agents have been implied as causative environmental factors in the development of autoimmunity. However, the exact nature of their involvement remains unknown. We describe a possible mechanism for the activation of autoreactive T cells induced by measles virus (MV) infection. The display of HLA-A*0201 associated peptides obtained from MV infected cells was compared with that from uninfected cells by mass spectrometry. We identified two abundant self peptides, IFI-6-16(74-82) and Hsp90beta(570-578), that were induced or upregulated, respectively, following infection. Their parental proteins, the type I interferon inducible protein IFI-6-16, and the beta chain of heat shock protein 90, have not been involved in MV pathogenesis. MV infection caused minor and major changes in the intracellular expression patterns of these proteins, possibly leading to altered peptide processing. CD8+ T cells capable of recognizing the self-peptides in the context of HLA-A*0201 were detectable at low basal levels in the neonatal and adult human T cell repertoire, but were functionally silent. In contrast, peptide-specific producing IFN-gamma producing effector cells were present in MV patients during acute infection. Thus, MV infection induces an enhanced display of self-peptides in MHC class I, which may lead to the temporary activation of autoreactive T cells.

A measles virus glycoprotein-derived human CTL epitope is abundantly presented via the proteasomal-dependent MHC class I processing pathway

Peptides derived from measles virus (MV) are presented by MHC class I molecules at widely divergent levels, but it is currently unknown how functional these levels are. Here, for the first time, we studied the natural occurrence and the underlying processing events of a known MV CTL epitope derived from the fusion glycoprotein (MV-F) and restricted via HLA-B*2705. Using MHC-peptide elution of MV-infected cells followed by sensitive mass spectrometry we determined the naturally occurring sequence to be RRYPDAVYL, corresponding to MV-F(438-446). Its level of expression was enumerated at approximately 1500 copies per cell, which is considered to be abundant, but lies within the range described for other viral CTL epitopes in human MHC class I molecules. We found that processing of the MV-F(438-446) epitope occurs primarily via the classic MHC class I loading pathway, since presentation to CTL depends on both the transporter associated with antigen presentation (TAP) and the proteasome. Even though it is cotranslationally inserted into the ER, a major part of MV-F is located in the cytosol, where it accumulates rapidly in the presence of proteasome inhibitors. We therefore conclude that a substantial cytosolic turnover of MV-F, together with some excellent processing features of MV-F(438-446) precursors, such as precise C-terminal excision by proteasomes, efficient TAP transport and strong HLA binding, dictate the abundant functional expression of the MV-F(438-446) CTL epitope in HLA-B*2705 at the surface of MV-infected cells.