1977. against the 2009 2009 A (H1N1) computer virus, even when tested at 5 g/ml (Table ?(Table22). MAb 4D20 kinetics. Given that the Sa-specific MAb 4D20 did not bind the HA of the 2009 2009 A (H1N1) computer virus, we explored the role of additional amino acid variations outside the Sa site in the alteration of binding and found that reversing either HA protein residue E77 or S78 of the 2009 2009 novel H1N1 to the respective residue of the 1918 computer virus HA restored binding of MAb 4D20 by biolayer interferometry using human Fc receptor tips and recombinant secreted HA. MAb 4D20 associated more readily with the E77D mutant ([equilibrium dissociation constant], 7.2 10?9 M versus 1.8 10?8 M, respectively). Selection and characterization of antibody escape mutants. We selected and sequenced the HA gene of new MARMs by using the wild-type (wt) A/swine/Iowa/15/1930 computer virus or a recombinant computer virus generated by reverse genetics made up of the CA04 HA and NA proteins in an A/Puerto Rico/8/34 computer virus background (kindly provided by Peter Palese) (1, 18). Briefly, escape mutant viruses were selected Phloroglucinol by treatment Phloroglucinol of computer virus with extra antibody, followed by recovery of neutralization-resistant viruses in 10-day-old embryonated chicken eggs. RNA was extracted from virus-infected allantoic fluid and then cDNA was generated by reverse transcription-PCR (RT-PCR), directly cloned, sequenced, and aligned to previously decided wt computer virus HA gene sequences. These studies revealed that MAb 2B12 selected computer virus mutants made up of either the K166E mutation or a novel mutation at the 125C position (S to I). The MAb 2D1 selected for the K166E or K166N mutation in the 2009 2009 Phloroglucinol HA protein, identical to changes that mediated escape to this antibody in MARMs selected by treatment of the 1918 human or 1930 swine viruses. Animal studies. We tested the MAbs 2B12 and 2D1 for therapeutic efficacy in a nonlethal mouse model of wt CA04 computer virus infection (9). Female BALB/c (8-week-old) mice were inoculated intranasally with 1,000 50% median infective dose (MID50) units in a 50-l volume of the CA04 computer virus, Rabbit Polyclonal to CARD11 as described previously (13). At 24 h after inoculation, mice were administered 200, 20, or 2 g (approximately 10, 1, or 0.1 mg/kg) of MAb 2D1 or 2B12 or an equal volume of human IgG (Sigma) by the intraperitoneal route to each mouse, in groups of nine mice. Mice were observed for weight loss every other day for 14 days. Subsets of four animals treated with the MAbs were euthanized on day 3 after contamination, and whole lungs were homogenized in 1 ml of sterile PBS. Computer virus titer in lung tissue homogenates was determined by plaque titration in MDCK cell monolayer cultures. The limit of computer virus detection was 100.95. MAb 2D1 showed a marked therapeutic efficacy when administered 1 day after Phloroglucinol computer virus inoculation, resulting in a 5 log10 PFU/ml decrease of lung computer virus titers of lung homogenate at the highest dose (Table ?(Table3)3) and the prevention of weight loss (Fig. ?(Fig.1).1). MAb 2B12 did not affect replication at the doses tested. Open in a separate windows FIG. 1. Therapeutic efficacy of 1918 HA-specific MAbs against disease caused by the 2009 2009 A (H1N1) computer virus in mice. In each group, five mice were followed every other day for weight. MAb 2D1 at 200-g or 20-g doses prevented weight loss at all time points after computer virus inoculation, compared to the control; ( 0.002 for all by analysis of variance [ANOVA]). Neither.