Molekulare Infektionsmechanismen des Lassavirus im humanen respiratorischen Epithel und die Entwicklung eines Antikörper-basierten Therapieansatzes

Lassa virus (LASV) belongs to the family Arenaviridae and is endemic to several West African countries. An estimated 100,000–300,000 infections occur annually with approximately 5,000 deaths. While most of the infections are mild or asymptomatic, approximately 20% progress to more severe health conditions, including hemorrhagic fever. To date, no specific antiviral drug or approved vaccine is available. Chronically infected rodents of the species Mastomys natalensis are the main rodent reservoir. Transmission of LASV from its rodent host to humans is thought to occur mainly via inhalation of dust or droplets contaminated with infectious rodent excretions. Although the respiratory tract is an important entry site for LASV, the mechanism of overcoming the epithelial barrier is unknown. To examine LASV infection processes of the human respiratory tract, the present work aimed to establish an air-liquid interface (ALI) cell culture model using differentiated human bronchial epithelial cells (HBEpCs). This in vitro cell system closely resembling composition, structure, and functional properties of the human airway epithelium in vivo was then used to analyse LASV replication kinetics, the polarity of viral entry and release, and to determine cell tropism of LASV in the bronchial epithelium. LASV can infect the respiratory epithelium via both the apical and basolateral membrane, tough different cell types are targeted during initial infection depending on the route of infection. Directed virus release occurred predominantly via the apical membrane, which is in agreement with an intrinsic apical localization of LASV GP. Virus release into the submucosal tissue via the basolateral membrane site was observed upon disruption of the epithelial integrity and thus polarity during multicyclic LASV replication. Similar to what has been observed in infected immune cells, LASV infection of the human respiratory tract does not induce a robust type I IFN response. However, infection of HBEpCs induced a strong type III IFN response. Interestingly, the type III IFN response was more pronounced upon LASV addition to the basolateral cell surface, suggesting that the antiviral immune response depends on the site of virus entry. In addition, the present study aimed to analyze the immunogenic potential of native-like trimeric GP expressed on the surface of LASV GP VLPs. Immunization of rabbits with these VLPs induced broadly neutralizing GP-specific antibodies capable of inhibiting the infection of relevant LASV human target cells, including airway epithelial cells. Functional characterization revealed that these neutralizing antibodies blocked virus-host interactions at the pre- and-post attachment level during viral entry. Furthermore, the polyclonal antisera show cross-neutralising activity against five phylogenetically different LASV lineages. In summary, the data obtained in the present work do not only provide new insights that contribute to a better understanding of the molecular pathogenicity mechanisms of LASV, but also to the development of novel potential therapeutic approaches against highly pathogenic LASV.