ABSTRACT
A H5N2 low pathogenic avian influenza virus (LPAIV) was isolated from a natural reservoir in Bavaria during a routine screen and was used as a vaccine strain to scrutinize the immune response involved in cross-protection after challenge infection with a H5N1 highly pathogenic avian influenza virus (HPAIV). The challenge virus was also isolated from a natural reservoir in Bavaria. Wild type, antibody deficient (muMT), CD4(-/-) and CD8(-/-) mice were infected with the apathogenic H5N2 vaccine strain and challenge infection with a 100-fold MLD(50) of the H5N1 strain was performed 80 days later. While 100% of the wild type and 100% of the CD8(-/-) mice stayed healthy, only 50% of the CD4(-/-) and none of the antibody deficient mice were protected. These results support the view that the humoral immune response and to certain extends the CD4(+) T helper cells are a prerequisite for cross-protective immunity against H5 influenza virus.
Subject(s)
Antibodies, Viral/immunology , CD4-Positive T-Lymphocytes/immunology , Influenza A Virus, H5N1 Subtype/immunology , Influenza A Virus, H5N2 Subtype/immunology , Influenza Vaccines/immunology , Orthomyxoviridae Infections/immunology , Orthomyxoviridae Infections/prevention & control , Animals , Antibody Formation/immunology , Antibody Specificity , Cell Line , Cross Reactions , Female , Flow Cytometry , Hemagglutination Inhibition Tests , Immunity, Cellular/immunology , Immunocompetence , Influenza A Virus, H5N2 Subtype/pathogenicity , Lymphocyte Count , Male , Mice , Mice, Inbred C57BL , Neutralization Tests , Respiratory System/pathology , Vaccination , Viral Plaque AssayABSTRACT
The almost simultaneous initial detections of avian influenza A H5N1 viruses in central Europe in February 2006, at a time devoid of migratory bird activity, raised the question of the origin of these viruses. This report presents molecular data from Europe providing evidence for multiple and spatially overlapping H5N1 introductions into Bavaria, Germany.
