[Seminar] Investigations of immune responses in acute co-infections with unrelated viruses and in vaccine non-responders

Please join us for a seminar from Dr Lukasz Kedzierski, Group Leader, Kedzierska Laboratory, Department of Microbiology and Immunology, Peter Doherty Institute for Infection and Immunity, University of Melbourne:

Date and time: 24 March 2026, 4:30pm - 6:00 PM

Venue: Seminar Room 2, G/F, HKJC Building for Interdisciplinary Research, 5 Sassoon Road

Viral co-infections can profoundly alter immune responses, influencing both disease severity and vaccine efficacy. Using a novel mouse model of co-infection with influenza A virus (IAV) and Semliki Forest virus (SFV), which target distinct organ systems, he demonstrates that the sequence of infection critically shapes antiviral immunity and immunopathology. Prior SFV infection impaired influenza-specific CD8⁺ T cell responses, delayed viral clearance and exacerbated lung inflammation. Conversely, prior influenza infection attenuated SFV-induced encephalitis but resulted in reduced long-term influenza-specific immunity. Simultaneous co-infection did not significantly modify disease outcomes. These findings highlight the balance between protective immunity and immunopathology dictated by co-infection timing.

In parallel, analysis of Australian inactivated influenza vaccine (IIV) cohorts (2015–2022) revealed that 50–60% of individuals failed to seroconvert, despite mounting cellular immune responses. Single-cell transcriptomic profiling of haemagglutinin-specific B cells showed that vaccine non-responders were dominated by atypical-like B cell subsets, whereas responders displayed a broader and more functional B cell repertoire. Elevated frequencies of atypical-like B cells were also associated with severe influenza infection.

Together, this work identifies key immunological determinants of viral co-infection outcomes and influenza vaccine non-responsiveness, providing insights for the development of improved antiviral and vaccination strategies.

About Dr Lukasz Kedzierski:

Dr Lukasz Kedzierski completed his PhD at Monash University on malaria vaccine development before working at the Walter and Eliza Hall Institute on Leishmania host–parasite interactions and drug discovery. He later focused on immune regulation during viral infections.

Since 2017, he has been a Senior Research Fellow and Group Leader at the University of Melbourne, where his research investigates viral persistence, co-infections and vaccine failure. He has authored over 100 publications in leading journals and has received competitive NHMRC and ARC funding.

All are welcome!