Leibniz Virology Lecture 2026 with Professor Otto Haller

A Lifetime of Discovery: Professor Haller Reflects on Mx1, Interferon, and the Transspecies Transmission of Influenza Virus

On 30 June 2026, the Leibniz Institute of Virology (LIV) welcomed Professor Otto Haller (University Medical Center Freiburg) for the annual Leibniz Virology Lecture. Professor Haller, recipient of the Robert Koch Gold Medal in 2025, looked back on a career that has fundamentally shaped our understanding of innate antiviral immunity. In his lecture, “Host Gene Control of Influenza Virus and Transspecies Transmission”, he retraced the discoveries that turned a chance observation into a cornerstone of modern virology.

The event opened with welcoming remarks from LIV Scientific Director Professor Marcus Altfeld, followed by a laudation by Professor Stephanie Pfänder, Head of the LIV Research Group “Emerging Viruses”. She highlighted not only Haller’s scientific contributions but also his dedication to mentoring young scientists. His leadership style, based on trust and scientific independence, had earned him the affectionate nickname “the scientific Montessori” among former students and trainees.

Professor Haller is widely regarded as a pioneer of innate antiviral immunity. His lecture showed how an unexpected observation in mice led to key insights into antiviral defence.

“It all started with an unexpected observation in mice,” Haller recalled. “Some animals survived influenza infection while others died. The crucial difference was a functional Mx1 gene.” Mx1-positive mice were resistant to influenza infection, whereas Mx1-deficient animals developed severe disease.

This unexpected finding ultimately led to the identification of Mx1 as a key effector of innate antiviral immunity. At the time, interferon was widely regarded as a non-specific antiviral factor. Haller's work revealed instead that interferon exerts its antiviral activity through highly specific inducible effector proteins, including Mx1, which inhibit influenza virus replication. In humans, the homologous protein MxA fulfils this defensive function.

As Haller explained, severe cases of influenza are often associated with inherited defects in the interferon pathway—so-called “inborn errors of immunity”. For instance, certain variants of MxA may compromise early antiviral defence in patients, thereby predisposing to severe disease.

At the same time, he showed how avian influenza viruses can evade MxA-mediated restriction through escape mutations. However, such adaptations frequently incur fitness costs, which must subsequently be compensated by additional mutations. MxA thus represents a major molecular barrier in the adaptation of influenza viruses to humans.

As in previous years, the lecture was accompanied by a live graphic recording capturing the main concepts. Afterwards, guests continued discussions over coffee and cake. Earlier that day, early-career researchers at LIV met Professor Haller over lunch for an informal exchange on research and scientific careers.

Through the annual Leibniz Virology Lecture, LIV honours outstanding scientists whose work has advanced our understanding of viruses and their interaction with the host, while inspiring future generations of researchers.