Impaired dendritic cell maturation in response to pandemic H1N109 influenza virus.

Background: Infection with pandemic A/H1N1/2009 influenza virus led to hospitalisation of patients not expected to be at risk of severe disease from seasonal influenza infection.

Objectives: We sought to establish whether (i) DC maturation was compromised in patients experiencing severe pandemic influenza infection, (ii) the pandemic virus differed from seasonal influenza virus in its ability to induce DC maturation and (iii) there was an associated inability to activate memory B cells or induce antibody.

Study Design: Peripheral blood mononuclear (PBMCs) cells were sampled from individuals with confirmed acute pandemic A/H1N1/2009 influenza infection or from healthy vaccinated controls. DCs were differentiated from the PBMC and tested for their ability to mature following stimulation with pandemic virus, seasonal H3N2 influenza virus or LPS. Serum samples from the patients were used to assess seroconversion to influenza and the levels of influenza specific memory B cells in PBMC were also determined.

Results: DCs obtained from all individuals exhibited negligible maturation marker upregulation when exposed to pandemic A/H1N1/2009 virus but showed a strong response to the seasonal H3N2 virus and LPS. Robust levels of memory B cell were obtained in both groups and patients seroconverted to the virus.

Conclusions: Overall, the ability of patient's DC to mature in response to different stimuli was no different to that of control subjects DCs. Importantly, panH1N109 virus failed to induce substantial DC maturation in any individual, contrasting with seasonal virus, but this did not result in failure to mount memory B cell and antibody responses to the virus.