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J. Virol., Aug 1995, 4888-4897, Vol 69, No. 8
S Kodihalli, DM Justewicz, LV Gubareva and RG Webster
This study investigated whether a single amino acid change in the
hemagglutinin (HA) molecule influenced the efficacy of formalin-
inactivated influenza A (H3N1) vaccine candidates derived from high- growth
reassortants between the standard donor of high-yield genes (A/PR/8/34
[H1N1]) and host cell variants generated from the same clinical isolate
(A/Memphis/7/90 [H3N2]) by passage in embryonated chicken eggs. Two clones
of the isolate generated by growth in eggs differed from the parent virus
(represented by an MDCK cell-grown counterpart) solely by the presence of
Lys (instead of Glu) at position 156 or Ile (instead of Ser) at position
186 in the HA1 subunit. The protective efficacy of egg-grown HA Lys-156 and
HA Ile-186 reassortant variants was compared with that of the MDCK
cell-grown reassortant vaccine. Classically, antibody titers in serum have
been used to demonstrate vaccine efficacy. Here, parameters of B-cell
responsiveness were monitored, including the kinetics, character, and
localization of the primary antibody-forming cell (AFC) response and the
development of B-cell memory in lymphoid tissues associated with the
priming site (spleen) and responsive to pulmonary challenge with infectious
virus (upper and lower respiratory tract lymph nodes). We show that the
egg- grown HA Lys-156 variant induced an AFC profile vastly different from
that elicited by the other two reassortant vaccines. The vaccine was poorly
immunogenic; it induced antibodies that were cross-reactive prior to
challenge but which, postchallenge with a lethal dose of the MDCK
cell-grown reassortant virus, were targeted primarily to the HA Lys-156
variant, were of the immunoglobulin M isotype, were nonprotective, and were
derived from the spleen. In contrast, the egg- grown HA Ile-186 variant was
remarkably like the MDCK cell-grown virus in that protective immunoglobulin
G antibodies were unaffected by the Ile-186 substitution but poorly
recognized HA with Lys-156. Furthermore, memory AFC responsiveness was
localized to regional lymphoid tissue in the upper respiratory tract, where
challenge HA was found. Thus, it is recommended that in the selection of
vaccine candidates, virus populations with the egg-adapted HA Lys-156
substitution be eliminated and that, instead, egg-grown isolates which
minimally contain Ile-186 be used as logical alternatives to MDCK cell-
grown viruses.
Copyright © 1995, American Society for Microbiology
Selection of a single amino acid substitution in the hemagglutinin molecule by chicken eggs can render influenza A virus (H3) candidate vaccine ineffective
Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38101, USA.
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