Antibodies (Abs) contribute to the control of @entity778 in vivo by reducing progeny virus yield from infected cells (yield reduction [YR]) and by inhibiting progeny virus from spreading the @entity281 to new host cells (virus neutralization [VN]). Previous studies showed that the @entity281 could be resolved in @entity466 ( @entity466 ) @entity19 by treatment with hemagglutinin (HA)-specific monoclonal antibodies (MAbs) that exhibit both VN and YR activities but not by MAbs that exhibited only YR activity. To determine whether virus clearance requires both activities, we measured the therapeutic activity of an HA-specific MAb (VN and YR) and its Fab fragment (VN) by intranasal (i.n.) administration to infected @entity466 @entity19 . @entity13446 ( @entity13446 ) and Fab cleared the @entity281 with i.n. 50% effective doses (ED(50)s) of 16 and 90 pmol, respectively. To resolve an established @entity281 solely by VN activity, Fab must be present in the respiratory tract at an effective threshold concentration until all infected cells have died and production of virus has ceased. Because @entity13446 and Fab had different half-lives in the respiratory tract (22 and 8 h, respectively) and assuming that both operated mainly or solely by VN, it could be estimated that clearance was achieved 24 h after Ab treatment when both reagents were present in the respiratory tract at approximately 10 pmol. This dose was approximately 200 times larger than the respiratory tract-associated Ab dose resulting from administration of the intraperitoneal ED(50) (270 pmol) of @entity13446 . This indicated that our procedure of i.n. administration of Ab did not make optimal use of the Ab's therapeutic activity.

Virus-neutralizing activity mediated by the Fab fragment of a hemagglutinin-specific antibody is sufficient for the @entity778 in @entity466 XXXX .

@entity778 :: ('MESH:D015658', 'Disease') :: ['influenza virus infection'] @entity19 :: ('10090', 'Species') :: ['mice'] @entity281 :: ('MESH:D007239', 'Disease') :: ['infection'] @entity13446 :: ('16059(Tax:10090)', 'Gene') :: ['Immunoglobulin G', 'IgG'] @entity466 :: ('MESH:D016511', 'Disease') :: ['SCID', 'severe combined immunodeficiency']
@entity19 :: (10090,Species) :: ['mice']
