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- Che, Karlhans Fru
(författare)
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Immunomodulatory Effects of Human ImmunodeficiencyVirus (HIV-1) on Dendritic Cell and T cell Responses : Studies of HIV-1 effects on Dendritic cell functionality reflected in primed T cells
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The human immunodeficiency virus (HIV)-1 is the causative agent of acquired immune deficiency syndrome (AIDS) worldwide. Till date there are no vaccines or cure for this infection as the virus has adapted myriad ways to remain persistent in the host where it causes severe damage to the immune system. Both humoral and cellular immune responses are mounted against HIV-1 during the initial phase of infection but fail to control viral replication as these responses are severely depleted during disease progression. Of great importance in HIV-1 research today is the in depth understanding of the types of immune responses elicited, the mechanisms behind their decline and how these responses can be maintained overtime.The focus of this thesis was to examine the possibility of priming HIV-1 specific T cell responses in vitro from whole viral particles and in detail, scrutinize the type of T cell responses and epitope specificities generated. Next was to investigate in vitro the factors responsible for impaired immune responses in HIV-1 infected individuals. We were also interested in understanding the underlying mechanisms through which HIV-1 initiate suppression of T cell functionality.Results showed that using HIV-1 pulsed monocyte derived dendritic cells (DCs), we were able to prime HIV-1 specific CD4+ and CD8+ T cells from naïve T cells in vitro. The epitopes primed in vitro were located within the HIV-1 envelope, gag, and pol proteins and were confirmed ex vivo to exist in acute and chronically infected individuals. We established that many of the novel CD4+ T cell epitopes primed in vitro also existed in vivo in HIV-1 infected individuals during acute infection. These responses declined/disappeared early on, which is in line with HIV-1 preferential infection of HIV-1 specific CD4+ T cells.Besides declining HIV-1 specific T cell responses, many HIV-1 infected individuals also have impaired T cell functionality. We established that one reason behind the decline and impairment in immune responses was the increased expression of inhibitory molecules PD-1, CTLA-4, and TRAIL on HIV-1 primed T cells. These T cells had the capacity to suppress new responses in a cell-cell contact dependent manner. The ability of the HIV-1 primed T cells to proliferate was severely impaired and this condition was reversed after a combined blockade of PD-1, CTLA-4 and TRAIL. Furthermore, more inhibitory molecules TIM-3, LAG-3, CD160, BLIMP-1, and FOXP3 were also found increased at both gene and protein levels on HIV-1 primed T cells. Additionally, we showed decreased levels of functional cytokines IL-2, IFN-γ and TNF-α, and the cytolytic proteins perforin and granzyme in DC T cell priming cocultures containing HIV-1. This could be as a result of the decreased T cell activation or impaired production by T cells. The mechanisms responsible for the elevated levels of inhibitory molecules emanated mainly from the P38MAPK/STAT3 pathways. Blockade of these pathways in both allogeneic and autologous DC-T cell assays significantly suppressed expression of inhibitory molecules and subsequently rescued T cell proliferation.In conclusion, HIV-1 pulsed DCs have the capacity to prime HIV-1 specific responses in vitro that do exist in HIV-1 infected individuals and we found evidence that many of these responses were eliminated rapidly in HIV-1 infected individuals. HIV-1 triggers through P38MAPK/STAT3 pathway the synthesis of inhibitory molecules, namely CTLA-4, PD-1, TRAIL, TIM-3, LAG-3, CD160, and suppression associated transcription factors FOXP3, BLIMP-1 and DTX1. This is followed by decreased T cell proliferation and functionality which are much needed to control viral replication.
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| 2. |
- Kindberg, Elin, 1981-
(författare)
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Host genetic risk factors to viral diseases - a double-edged sword : Studies of norovirus and tick-borne encephalitis virus
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is today well known that the outcome of a certain infection depends on factors of both the host and the pathogen. Studies of host genetic susceptibility to infectious diseases aim to increase the understanding of why some individuals are more susceptible than others, to a certain infection. Knowledge of genetic susceptibility to a viral disease may be used in development of new therapeutic means, and also to recognize individuals who are at increased risk of severe symptoms if infected with a pathogen. It seems however that a risk factor for one disease may play a protective role in another situation; like a double-edged sword.In this thesis I have studied genetic factors affecting susceptibility to norovirus (NoV) and factors affecting the risk of developing tick-borne encephalitis (TBE) after infection with TBE virus (TBEV). NoV is the cause of the “winter vomiting disease”, affecting millions of people every year, and causing up to 200,000 fatalities among children in developing countries, each year. It is today recognized that the secretor status of an individual, i.e. the ability to express ABO blood groups and related antigens, in secretions and on mucosa, affect the risk of being infected by NoV. By studying authentic NoV outbreaks in Denmark, Spain and Sweden and by comparing the secretor status of affected and unaffected individuals we were able to confirm that secretor status have indeed great impact on susceptibility to some NoV strains, but also that there are strains circulating, which infect individuals regardless of secretor status.TBEV is endemic in many parts of Europe and Asia but studies have shown that 70-95% of all infections are asymptomatic or sub-clinical. Some individuals do however develop TBE, a severe disease including meningitis or encephalitis with or without myelitis. Also, many patients suffer from long-time sequelae and TBEV infections may in worst case be fatal. The reason for difference in disease outcome is not known and we have chosen to study if genetic factors affecting the immune response may play a role in disease outcome. To do this we used a prospectively collected Lithuanian material with samples from patients with TBE, AME (aseptic meningoencephalitis) and matched healthy controls. So far we have found that a deletion in chemokine receptor 5 (CCR5), a gene encoding a receptor involved in cell migration, is a risk factor for developing disease. We have also data showing that toll-like receptor 3 (TLR3), a receptor recognizing double stranded RNA (dsRNA), which is a product of TBEV replication, may instead of being protective increase the risk of TBE.
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| 3. |
- Tjomsland, Veronica
(författare)
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Complement activation - good or evil in HIV-1 infection? : interaction of free and complement opsonized HIV-1 with monocyte derived dendritic cells and immune cells in the cervical mucosa
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Worldwide, the heterosexual route is the most common mode of sexual transmission of HIV-1 and women are particularly susceptible to this infection. After penetration of the mucosal epithelium HIV-1 interacts with potential target cells, i.e. dendritic cells (DCs) and CD4+ T cells. The complement system, a key component of the innate immune system, is immediately activated by HIV-1 in vivo. However, HIV-1 can resist complement mediated lysis and become coated with complement fragments and this opsonization influences the viral interaction with immune cells. The DCs are the most potent antigen presenting cell. This cell effectively links the innate recognition of viruses to the generation of an adaptive immune response. However, HIV-1 exploits the function of the DCs to facilitate viral spread and infection. HIV-1 interacts with a range of receptors expressed by the DCs including C-type lectins, integrins and complement receptors (CRs). The uptake of virions by DCs leads to their activation and migration to the lymph nodes. At this site DCs present HIV-1 derived antigen on MHC class I and II molecules and trigger an HIV-1 specific T cell response. The interplay between the virus and the DCs is complex and the initial receptor binding may affect antigen uptake, infection, and antigen presentation.The fundamental questions of this thesis are the following: How is free and opsonized HIV-1 internalized, processed, and presented on MHC class I and II molecules by DCs and how do free and opsonized HIV-1 particles interact with immune cells in the cervical mucosa?Our results indicate that opsonization of HIV-1 plays a critical role in the interaction with immune cells. Complement opsonization of HIV-1 (C-HIV) significantly enhanced the internalization by the DCs compared to free HIV (F-HIV). Both C-HIV and F-HIV interacted with the CD4 receptor, C-type lectins and integrins. In addition, opsonization of HIV-1 favored an MHC class I presentation by DCs compared to F-HIV. However, the endocytic receptors macrophage mannose receptor, β7 integrin, and CR3 guided the antigens to different compartments with distinct properties and efficiencies for degradation and MHC class I and II presentation of viral antigens. MHC class I presentation of F-HIV and C-HIV was dependent of viral fusion in a CD4/coreceptor dependent manner. Moreover, MHC class II presentation of antigens derived from HIV-1 required endocytosis and proteolysis in acidified compartments. HIV-1 infection of cervical mucosa immune cells and tissue was assessed in a cervical tissue explant model. C-HIV significantly enhanced infection of DCs compared to F-HIV, whereas C-HIV decreased the infection of CD4+ T cells. Blocking the viral use of integrins in the cervical tissue explants significantly decreased the HIV-1 infection of both emigrating DCs and CD4+ T cells and the establishment of founder populations in these tissues. This thesis work has brought forward new facts that can be used to facilitate the development of an effective vaccine or microbicide.
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