Therapeutic vaccination for chronic hepatitis B in the Trimera mouse model

Therapeutic vaccination for chronic hepatitis B in the Trimera mouse modelrnRaja Vuyyuru and Wulf O. BöcherrnHepatitis B is a liver disease caused by Hepatitis B virus (HBV). It ranges in severity from a mild illness, lasting a few weeks (acute), to a serious long-term (chronic) illness that can lead either to liver disease or liver cancer. Acute infection is self limiting in most adults, resulting in clearance of virus from blood and liver and the development of lasting immunity. However 5% of acutely infected patients do not resolve primary HBV infection, leading to chronic infection with persistent viral replication in the liver. The strength of the initial antiviral immune response elicited to Hepatitis B determines the subsequent clinical outcome. A strong and broad T cell response leads to spontaneous resolution. Conversely, a weak T cell response favours viral persistence and establishment of chronic disease. While treatments using interferon-alpha or nucleos(t)ide analogues can reduce disease progression, they rarely lead to complete recovery. The lack of a suitable small animal model hampered efforts to understand the mechanisms responsible for immune failure in these chronic patients.rnIn current study we used Trimera mice to study the efficacy of potential vaccine candidates using HBV loaded dendritic cells in HBV chronic infection in vivo. The Trimera mouse model is based on Balb/c mice implanted with SCID mouse bone marrow and human peripheral blood mononuclear cells (PBMC) from HBV patients, and thus contains the immune system of the donor including their HBV associated T cell defect.rnIn our present study, strong HBV specific CD4+ and CD8+ T cell responses were enhanced by therapeutic vaccination in chronic HBV patients. These T cell responses occurred independently of either the course of the disease or the strength of their underlying HBV specific T cell failure. These findings indicate that the Trimera mouse model represents a novel experimental tool for evaluating potential anti-HBV immunotherapeutic agents. This in vivo data indicated that both the HBV specific CD4+ cell and CD8+ responses were elicited in the periphery. These HBV specific T cells proliferated and secreted cytokines upon restimulation in Trimera mice. The observation that these HBV specific T cells are not detectable directly ex vivo indicates that they must be immune tolerant or present at a very low frequency in situ. HBV specific T cell responses were suppressed in Trimera mice under viremic conditions, suggesting that viral factors might be directly involved in tolerizing or silencing antiviral T cell responses. Thus, combination of an effective vaccine with antiviral treatment to reduce viremia might be a more effective therapeutic strategy for the future. Such approaches should be tested in Trimera mice generated in HBV or HBs expressing transgenic mice before conducting clinical trials.rn

A new double laser pulse pumping scheme for transient collisionally excited plasma soft X-ray lasers

Within this thesis a new double laser pulse pumping scheme for plasma-based, transient collisionally excited soft x-ray lasers (SXRL) was developed, characterized and utilized for applications. SXRL operations from ~50 up to ~200 electron volt were demonstrated applying this concept. As a central technical tool, a special Mach-Zehnder interferometer in the chirped pulse amplification (CPA) laser front-end was developed for the generation of fully controllable double-pulses to optimally pump SXRLs.rnThis Mach-Zehnder device is fully controllable and enables the creation of two CPA pulses of different pulse duration and variable energy balance with an adjustable time delay. Besides the SXRL pumping, the double-pulse configuration was applied to determine the B-integral in the CPA laser system by amplifying short pulse replica in the system, followed by an analysis in the time domain. The measurement of B-integral values in the 0.1 to 1.5 radian range, only limited by the reachable laser parameters, proved to be a promising tool to characterize nonlinear effects in the CPA laser systems.rnContributing to the issue of SXRL pumping, the double-pulse was configured to optimally produce the gain medium of the SXRL amplification. The focusing geometry of the two collinear pulses under the same grazing incidence angle on the target, significantly improved the generation of the active plasma medium. On one hand the effect was induced by the intrinsically guaranteed exact overlap of the two pulses on the target, and on the other hand by the grazing incidence pre-pulse plasma generation, which allows for a SXRL operation at higher electron densities, enabling higher gain in longer wavelength SXRLs and higher efficiency at shorter wavelength SXRLs. The observation of gain enhancement was confirmed by plasma hydrodynamic simulations.rnThe first introduction of double short-pulse single-beam grazing incidence pumping for SXRL pumping below 20 nanometer at the laser facility PHELIX in Darmstadt (Germany), resulted in a reliable operation of a nickel-like palladium SXRL at 14.7 nanometer with a pump energy threshold strongly reduced to less than 500 millijoule. With the adaptation of the concept, namely double-pulse single-beam grazing incidence pumping (DGRIP) and the transfer of this technology to the laser facility LASERIX in Palaiseau (France), improved efficiency and stability of table-top high-repetition soft x-ray lasers in the wavelength region below 20 nanometer was demonstrated. With a total pump laser energy below 1 joule the target, 2 mircojoule of nickel-like molybdenum soft x-ray laser emission at 18.9 nanometer was obtained at 10 hertz repetition rate, proving the attractiveness for high average power operation. An easy and rapid alignment procedure fulfilled the requirements for a sophisticated installation, and the highly stable output satisfied the need for a reliable strong SXRL source. The qualities of the DGRIP scheme were confirmed in an irradiation operation on user samples with over 50.000 shots corresponding to a deposited energy of ~ 50 millijoule.rnThe generation of double-pulses with high energies up to ~120 joule enabled the transfer to shorter wavelength SXRL operation at the laser facility PHELIX. The application of DGRIP proved to be a simple and efficient method for the generation of soft x-ray lasers below 10 nanometer. Nickel-like samarium soft x-ray lasing at 7.3 nanometer was achieved at a low total pump energy threshold of 36 joule, which confirmed the suitability of the applied pumping scheme. A reliable and stable SXRL operation was demonstrated, due to the single-beam pumping geometry despite the large optical apertures. The soft x-ray lasing of nickel-like samarium was an important milestone for the feasibility of applying the pumping scheme also for higher pumping pulse energies, which are necessary to obtain soft x-ray laser wavelengths in the water window. The reduction of the total pump energy below 40 joule for 7.3 nanometer short wavelength lasing now fulfilled the requirement for the installation at the high-repetition rate operation laser facility LASERIX.rn