INTERFERENCE BETWEEN COLD-ADAPTED (CA) INFLUENZA-A AND INFLUENZA-B VACCINE REASSORTANTS OR BETWEEN CA REASSORTANTS AND WILD-TYPE STRAINS INEGGS AND MICE

Interference between pairs of cold-adapted (ca) influenza A and B vacc ine reassortant viruses and between ca influenza B reassortant viruses and wild-type influenza strain A/PR/8/34 was studied in embryonated e ggs and/or in the respiratory tract of three strains of mice. Interfer ence in eggs between ca A and B reassortants occurred after 2 days but was masked by later cycles of growth. When doses of 10(6) EID(50) of the reassortant viruses B/60/32/R and A/47/6/R were administered to ou tbred mice, interference with the growth of A/47/6/R occurred in the t urbinates; interference with the growth of B/60/32/R did nor occur. Ho wever, interference with the growth of B/60/32/R was noted in the lung s of Balb/c mice after co-infection with 10(6) EID(50) of both A/PR/8/ 34 and B/60/32/R. Interference did not occur when the dose of B/60/32/ R was increased to 10(7) ErD50 per mouse. When CBA mice were co-infect ed with 10(6) EID(50) of both B/60/32/R and the influenza A ca reassor tant R/34, or 10(6) EID(50) of B/60/32/R, R/34 and A/Leningrad/134/57, interference did not occur. Interference could not be detected in mic e following dual infection from serum responses to individual viruses.