Role of glycans for gO-dependent entry of the human cytomegalovirus

• Applicant: Dr. Cora Stegmann
• Subject Area: Virology
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 419091726

Infections with the human cytomegalovirus (HCMV) are a major problem for pregnant women as they can result in severe diseases of the in utero infected child, even under conditions of preexisting immunity. A reason for this insufficient immune protection could be the low frequency of antibodies against the glycoprotein O (gO). This protein forms a complex with the glycoproteins gH and gL which is not essential but determines the infectivity of progeny virus. Currently, the mechanisms of gO-dependent entry of HCMV are not fully understood. More than 50% of the molecular mass of gO are made up by glycans which could contribute to infection as well as to protection of the virus from antibodies. However, their role has not been addressed directly yet. Therefore, the aim of this project is to determine the role of the glycans on gO for HCMV entry and to clarify whether the glycans contribute to shielding of HCMV from neutralizing antibodies. To answer these questions, the first step is to systematically mutate each of the predicted glycosylation sites within gO. This will allow to determine which glycans contribute to formation of the gH/gL/gO complex and which glycan modifications are dispensable and can be therefore removed without interfering with the incorporation of the complex into the virion. Based on these data, a virus with reduced glycosylation of gO will be generated. In order to test the importance of the glycans for virus entry, this virus will then be characterized regarding its ability to bind to and penetrate into HCMV host cells. A recently developed human lectin microarray will be utilized to directly and systematically test the interaction of gO with this class of glycan-binding proteins. This approach will identify novel cellular interaction partners of HCMV and thereby help to further elucidate the mechanisms of gO-dependent entry of HCMV. To test the hypothesis of gO-mediated glycan shielding, it will be analyzed whether the virus with reduced glycosylation is more sensitive to neutralization and if it induces an enhanced antibody response. Overall, this project will deepen our understanding of HCMV entry and potentially lead to the development of improved immunization strategies against HCMV infection.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Brent Ryckman, Ph.D.