Pandemic influenza A H1N1/09 virus infection in hematopoietic SCT recipient

Influenza virus infects bone marrow mesenchymal stromal cells in vitro: implications for bone marrow transplantation

Mesenchymal stromal cells (MSCs) have differentiation, immunomodulatory, and self-renewal properties and are, therefore, an attractive tool for regenerative medicine and autoimmune diseases. MSCs may be of great value to treat graft-versus-host disease. Influenza virus causes highly contagious seasonal infection and occasional pandemics. The infection is severe in children, elderly, and immunocompromised hosts including hematopoietic stem cell transplant patients. The objective of this study was to determine if MSCs are permissive to influenza virus replication. We isolated MSCs from the bone marrow of 4- to 6-week-old germ-free pigs. Swine and human influenza virus strains were used to infect MSCs in vitro. MSCs expressed known influenza virus α-2,3 and α-2,6 sialic acid receptors and supported replication of swine and human influenza viruses. Viral infection of MSCs resulted in cell lysis and proinflammatory cytokine production. These findings demonstrate that bone marrow-derived MSCs are susceptible to influenza virus. The data also suggest that transplantation of bone marrow MSCs from influenza virus-infected donors may transmit infection to recipients. Also, MSCs may get infected if infused into a patient with an ongoing influenza virus infection.

Clinical features and outcome of 2009-influenza A (H1N1) after allogeneic hematopoietic SCT

The impact of the 2009 H1N1-Influenza A (H1N1) pandemic in allogeneic hematopoietic SCT recipients (allo-HSCT) is not yet well defined. Between May 2009 and May 2010, all allo-HSCTs who presented with respiratory symptoms were screened for the presence of the H1N1 virus. Oseltamivir resistance was assessed and chart reviews were performed for all cases. In all, 51 of 248 (20%) allo-HSCT recipients followed at our outpatient clinic were screened. We identified 10 patients with H1N1 infection. Close contact with children was the most commonly suspected mode of transmission. Upper and lower respiratory tract infections were present in eight and five patients, respectively. Lymphopenia (<1 G/L) was the most frequent biological abnormality. High immunosuppression was responsible for severe infection requiring mechanical ventilation associated with prolonged viral shedding in three patients who had significant comorbidities and GvHD. Two of them developed an oseltamivir-resistant strain and both patients died subsequently despite intensive therapy, resulting in a case fatality rate of 20%. In conclusion, although most allo-HSCTs had mild symptoms from H1N1 infection, severe immunosuppression and emergence of oseltamivir resistance were likely responsible for a substantial morbidity, further supporting the need for vaccination and monitoring of close contacts, especially children.