Immunogenic and isotype-specific responses to Russian and US cold-adapted influenza A vaccine donor strains A/Leningrad/134/17/57, A/Leningrad/134/47/57, and A/Ann Arbor/6/60 (H2N2) in mice

The immunogenicity of the Russian cold-adapted (ca) donor stains, A/Leningr ad (Len)/134/17/57 and A/Leningrad/134/47/57, and the US strain A/Ann Arbor (AA)/6/60-ca, were compared in BALB/c mice with their respective wild-type parental viruses. Each ca donor strain was less immunogenic than. its wild -type parent. The vaccinating dose, when administered twice, which prevente d multiplication of a standard challenge of parental wild-type virus in 50% of mice (the 50% protective dose or PD50), was shown for A/Len/134/17/57-c a, A/Len/134/47/57-ca, and A/AA/6/60-ca to be 10(3.77), 10(4.32), and 10(4. 70), respectively. These findings were extended by measuring the number of antibody secreting cells induced in the lungs and mediastinal lymph nodes o f mice infected with the same ca donors using an ELISPOT assay. When each d onor strain was administered twice at a dose of 100 PD50 over a 3-week inte rval, the overall immunoglobulin isotype antibody secreting cell profiles w ere shown to be similar. However, A/Len/134/17/57-ca and A/Len/134/47/57-ca induced significantly higher total immunoglobulin responses in the lungs t han A/AA/6/60-ca (P <0.05). A/Len/134/17/57-ca also induced a significantly greater IgA response in the lungs than A/AA/6/60-ca (P <0.05). These resul ts suggest that A/Len/134/17/57-ca is a superior immunogen to A/Len/134/47/ 57-ca which in turn is more immunogenic than A/AA/6/60-ca. (C) 2001 Wiley-L iss, Inc.