| 1. |
- Andersson, Björn, 1985, et al.
(författare)
-
Nitrogen fixation in shallow-water sediments: Spatial distribution and controlling factors
- 2014
-
Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 59:6, s. 1932-1944
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrogenase activity (NA) in shallow-water (< 1 m) sediments was investigated at 60 randomly selected sites along a 150 km stretch on the brackish-water Swedish west coast, without targeting any specific type of sediments, such as microbial mats. Benthic nitrogen (N) fixation and diazotrophs (nifH genes) were found at all sites, regardless of the presence of cyanobacterial or microbial mats. The majority of sites showed N fixation rates between 0.03 and 1 mmol N m−2 d−1. These rates were similar to those of benthic denitrification previously measured in the area. Maximum rates up to 3.4 mmol N m−2 d−1 were measured. A structural equation model was used to investigate direct and indirect effects of biogeochemical and physical factors on NA. Number of nifH genes had the largest direct positive influence on NA, whereas increasing wave exposure had an indirect negative effect on NA through its influence on the diazotrophic abundance. Increased salinity, previously been shown to suppress NA in coastal waters, was found to directly stimulate benthic N fixation, likely by generating favorable conditions for diazotrophic sulfate-reducing bacteria. Our field data confirmed previously observed negative effects of dissolved inorganic nitrogen on NA, which have so far mainly been experimentally studied. Both NA rates and the number of nifH genes correlated positively with pore-water dissolved inorganic phosphorus concentrations. These findings show that the potential for N fixation in illuminated sediments can be considerable, stretching beyond cyanobacterial mats, being controlled by complex interactions between biotic and abiotic factors.
|
|
| 2. |
- Forsell, Mattias N E, et al.
(författare)
-
Biochemical and immunogenic characterization of soluble human immunodeficiency virus type 1 envelope glycoprotein trimers expressed by semliki forest virus.
- 2005
-
Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 79:17, s. 10902-14
-
Tidskriftsartikel (refereegranskat)abstract
- The current lack of envelope glycoprotein immunogens that elicit broadly neutralizing antibody responses remains a major challenge for human immunodeficiency virus type 1 (HIV-1) vaccine development. However, the recent design and construction of stable soluble gp140 trimers have shown that some neutralization breadth can be achieved by using immunogens that better mimic the functional viral spike complex. The use of genetic delivery systems to drive the in vivo expression of such immunogens for the stimulation of neutralizing antibodies against HIV-1 may offer advantages by maintaining the quaternary structure of the trimeric envelope glycoproteins. Here, we describe the biochemical and immunogenic properties of soluble HIV-1 envelope glycoprotein trimers expressed by recombinant Semliki Forest virus (rSFV). The results presented here demonstrate that rSFV supports the expression of stable soluble gp140 trimers that retain recognition by conformationally sensitive antibodies. Further, we show that rSFV particle immunizations efficiently primed immune responses as measured after a single boost with purified trimeric gp140 protein, resulting in a Th1-biased antibody response. This differed from the Th2-biased antibody response obtained after repeated immunizations with purified gp140 protein trimers. Despite this difference, both regimens stimulated neutralizing antibody responses of similar potency. This suggests that rSFV may be a useful component of a viral vector prime-protein boost regimen aimed at stimulating both cell-mediated immune responses and neutralizing antibodies against HIV-1.
|
|
| 3. |
- Sundbäck, Maria
(författare)
-
Vaccine strategies based on mycobacterial heat shock protein 65
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mycobacteria can infect macrophages and dendritic cells (DC), where they reside inside the endosomal compartment. The importance of CD4+ T cells in protective immunity against mycobacteria and other intracellular pathogens is well established, and for a long time these cells were thought to be the major defense in controlling an infection. Lately, several reports have shown that also cytotoxic CD8+ T cells contribute to protective immunity. Heat shock proteins (lisp) are highly conserved molecules that have been shown to contain important antigens both for B and T cell mediated immune responses against several infections. Studies have indicated that in vivo expression of the hsp65 gene from M. leprae could induce protection against live bacterial challenge with M. tuberculosis. CD8+ T cells could confer the observed hsp65 induced protection. We studied an immunization approach where plasmids encoding mycobacterial hsp65 (Mhsp65) were injected intramuscularly in mice to evaluate the resultant immune response following in vivo transcription of the immunogen. This mode of immunization is associated with efficient CD8+ T cell priming and the generation of a T helper I (Th1) type of immune response. Genetic vaccination further offers possibilities to manipulate the quality of the induced immune responses. We showed that the immune response could be efficiently enhanced after co-administration of either a Schiff base forming drug, tucaresol, or by plasmids encoding the cytokines interferon-gamma (IFN-gamma) or granulocyte-macrophage colony stimulating factor (GM-CSF). Among these, tucaresol had the most prominent effect, resulting in a general enhancement of the immune responses in our studies. This makes tucaresol a potent and interesting adjuvant candidate for plasmid DNA immunization. Human antigenic epitopes can be evaluated in mice expressing transgenes for human HLA complexes, since antigen processing and presentation is similar in mouse and man. We concluded that Mhsp65 plasmid injection results in human HLA class I and II restricted antigen presentation, and a subsequent priming of CD8+ and CD4+ T cells in HLA transgenic mice. We did also investigate CD8+ T cells with specificity for Mhsp65. This was studied by the identification of human I-ILA class I restricted cytotoxic T lymphocyte (CTL) epitopes encoded within Mhsp65. One of the identified epitopes, Mhsp659-369, is conserved within hsp65 from several human pathogens. Our results revealed that Mhsp659-369 could be processed and presented in the context of HLA-A*0201 during both Salmonella and mycobacterial infections. Several additional pathogens have this conserved epitope. These results suggested that T cells primed during infections may recognize conserved pathogen-associated epitopes, thereby conferring protection to unrelated pathogens. In summary, DNA vaccines have the potential to induce protection against intracellular pathogens like M. tuberculosis, where Mhsp65 fulfills the criteria to be an efficient antigen. The use of defined epitopes can ftirther restrict the immune responses.
|
|
