Combination Therapy Using Chimeric Monoclonal Antibodies Protects Mice from Lethal H5N1 Infection and Prevents Formation of Escape Mutants

Abstract

BackgroundGiven that there is a possibility of a human H5N1 pandemic and the fact that the recent H5N1 viruses are resistant to the anti-viral drugs, newer strategies for effective therapy are warranted. Previous studies show that single mAbs in immune prophylaxis can be protective against H5N1 infection. But a single mAb may not be effective in neutralization of a broad range of different strains of H5N1 and control of potential neutralization escape mutants.Methods/Principal FindingsWe selected two mAbs which recognized different epitopes on the hemagglutinin molecule. These two mAbs could each neutralize in vitro escape mutants to the other and in combination could effectively neutralize viruses from clades 0, 1, 2.1, 2.2, 2.3, 4, 7 and 8 of influenza A H5N1 viruses. This combination of chimeric mAbs when administered passively, pre or post challenge with 10 MLD50 (50% mouse lethal dose) HPAI H5N1 influenza A viruses could protect 100% of the mice from two different clades of viruses (clades 1 and 2.1). We also tested the efficacy of a single dose of the combination of mAbs versus two doses. Two doses of the combination therapy not only affected early clearance of the virus from the lung but could completely prevent lung pathology of the H5N1 infected mice. No escape variants were detected after therapy.Conclusions/SignificanceOur studies provide proof of concept that the synergistic action of two or more mAbs in combination is required for preventing the generation of escape mutants and also to enhance the therapeutic efficacy of passive therapy against H5N1 infection. Combination therapy may allow for a lower dose of antibody to be administered for passive therapy of influenza infection and hence can be made available at reduced economic costs during an outbreak.

Intranasal Delivery of an IgA Monoclonal Antibody Effective against Sublethal H5N1 Influenza Virus Infection in Mice

“…In this regard, DPJY01 shows remarkable activity against H5N1 infection under prophylactic and therapeutic conditions. Previous studies have shown the potential of IgG MAbs for passive immunotherapy against H5N1 influenza virus when administered parentally (4,9,18,19,24,27,28,30,38). Instead, we developed an IgA MAb that can be administered intranasally.…”

Properties and Therapeutic Efficacy of Broadly Reactive Chimeric and Humanized H5-Specific Monoclonal Antibodies against H5N1 Influenza Viruses

“…Research groups, including ours, have attempted to characterize MAbs which bind to the conserved epitopes located on the HA1 subunit (7,25,31). Recently, several studies have reported on MAbs which recognize a highly conserved helical region in the membrane-proximal stem of HA1/HA2 and which demonstrate heterosubtypic neutralizing abilities against H1, H2, H5, H6, H8, and H9 subtype viruses (10,30,33).…”

“…The HA2 subunit, which is primarily responsible for mediating the fusion of viral and cell membranes, is relatively conserved among different subtypes of influenza viruses. While most H5N1-specific antibodies have been found to target the HA1 region (7,21,25,31), several recent studies have reported on antibodies with the potential to neutralize influenza viruses of different subtypes by targeting the HA2 region of the HA protein (10,12,15,30,33).…”

Opportunities and Challenges of Therapeutic Monoclonal Antibodies as Medical Countermeasures for Biodefense

“…This problem may be overcome by using mixtures of mAbs that target various areas of bio-threat agents. Several studies demonstrated that combination therapy with mAb cocktails could prevent escape variants for many viruses including influenza, coronavirus, and lymphocytic choriomeningitis virus [50][51][52]. Also, a cocktail of functional mAbs could provide more protection and target more microbial strains than a single one.…”