Vaccination against Seasonal Influenza A/H3N2 Virus Reduces the Induction of Heterosubtypic Immunity against Influenza A/H5N1 Virus Infection in Ferrets

Infection of the Upper Respiratory Tract with Seasonal Influenza A(H3N2) Virus Induces Protective Immunity in Ferrets against Infection with A(H1N1)pdm09 Virus after Intranasal, but Not Intratracheal, Inoculation

“…These findings are in agreement with previous studies which demonstrated that after intranasal inoculation with a seasonal influenza A(H3N2) virus, ferrets were protected from infection with a highly pathogenic avian influenza A virus of the H5N1 subtype or with influenza A(H1N1)pdm09 virus inoculated via the intranasal route (16,17).…”

“…For instance, a seasonal A(H3N2) virus inoculated intranasally in a volume of 50 l into mice typically reaches the lungs, resulting in virus replication in that organ, which in turn causes pathological changes and the formation of inducible bronchiole-associated lymphoid tissue (iBALT) (21,49), containing local virus-specific B and T cells, which may contribute to protective immunity in the lungs to viruses of other subtypes, including H5N1 and H1N1pdm09 (16). In contrast, influenza virus A/Brisbane/010/ 2007 (H3N2) inoculated intranasally into ferrets did not cause pathological changes or formation of iBALT in the lungs and therefore may confer only inefficient direct protection against replication in the lungs (16).…”

“…The protein concentration was determined using a bicinchoninic acid (BCA) protein assay kit (Thermo Scientific Pierce Protein Biology Products). The presence of virus-specific T cells in peripheral blood mononuclear cells (PBMC) of ferrets 28 days after inoculation with influenza A/H3N2 virus was tested using a T cell proliferation assay as described previously (16,41). In brief, cryopreserved PBMC were thawed, washed, and then labeled with 0.3 M carboxyfluorescein diacetate succinimidyl ester (CFSE; Invitrogen, Breda, Netherlands) for 5 min.…”

“…This type of immunity has been demonstrated mainly in animals, including mice (13)(14)(15), ferrets (16,17), and guinea pigs (18), using various combinations of influenza A virus subtypes for priming and challenge infections. Heterosubtypic immunity can be long lasting, as demonstrated in ferrets (19).…”

“…In most studies, the same route of inoculation is used for priming and challenge infections with viruses of different subtypes (16,17,22). For example, priming with a seasonal influenza A virus and subsequent challenge infection of ferrets with A(H1N1)pdm09 viruses were performed by intranasal inoculation (17,22,34).…”