A. P. West, Structural insights on the role of antibodies in HIV-1 vaccine and therapy, Cell, vol.156, pp.633-648, 2014.

A. L. Moekotte, Monoclonal antibodies for the treatment of Ebola virus disease, Expert. Opin. Investig. Drugs, vol.25, pp.1325-1335, 2016.

R. Nachbagauer and F. Krammer, Universal influenza virus vaccines and therapeutic antibodies, Clin. Microbiol. Infect, vol.23, pp.222-228, 2017.

S. Paessler and D. H. Walker, Pathogenesis of the viral hemorrhagic fevers, Annu. Rev. Pathol, vol.8, pp.411-440, 2013.

T. W. Geisbert and P. B. Jahrling, Exotic emerging viral diseases: progress and challenges, Nat. Med, vol.10, pp.110-121, 2004.

M. B. Oldstone, Arenaviruses. I. The epidemiology molecular and cell biology of arenaviruses. Introduction, Curr. Top. Microbiol. Immunol, vol.262, 2002.

J. H. Nunberg and J. York, The curious case of arenavirus entry, and its inhibition, Viruses, vol.4, pp.83-101, 2012.

R. N. Charrel and X. De-lamballerie, Arenaviruses other than Lassa virus, Antivir. Res, vol.57, pp.89-100, 2003.

T. Lisieux, New arenavirus isolated in Brazil, Lancet, vol.343, pp.391-392, 1994.

R. B. Tesh, P. B. Jahrling, R. Salas, and R. E. Shope, Description of Guanarito virus (Arenaviridae: Arenavirus), the etiologic agent of Venezuelan hemorrhagic fever, Am. J. Trop. Med. Hyg, vol.50, pp.452-459, 1994.

M. Zong, I. Fofana, and H. Choe, Human and host species transferrin receptor 1 use by North American arenaviruses, J. Virol, vol.88, pp.9418-9428, 2014.

M. Enserink, Emerging diseases. New arenavirus blamed for recent deaths in California, Science, vol.289, pp.842-843, 2000.

S. R. Radoshitzky, Transferrin receptor 1 is a cellular receptor for New World haemorrhagic fever arenaviruses, Nature, vol.446, pp.92-96, 2007.

H. Choe, S. Jemielity, J. Abraham, S. R. Radoshitzky, and M. Farzan, Transferrin receptor 1 in the zoonosis and pathogenesis of New World hemorrhagic fever arenaviruses, Curr. Opin. Microbiol, vol.14, pp.476-482, 2011.

J. Abraham, Host-species transferrin receptor 1 orthologs are cellular receptors for nonpathogenic new world clade B arenaviruses, PLoS Pathog, vol.5, p.1000358, 2009.

T. Reignier, Receptor use by the Whitewater Arroyo virus glycoprotein, Virology, vol.371, pp.439-446, 2008.

T. A. Bowden, Unusual molecular architecture of the machupo virus attachment glycoprotein, J. Virol, vol.83, pp.8259-8265, 2009.

D. J. Burri, J. R. Da-palma, S. Kunz, and A. Pasquato, Envelope glycoprotein of arenaviruses, Viruses, vol.4, pp.2162-2181, 2012.

S. Mahmutovic, Molecular basis for antibody-mediated neutralization of new world hemorrhagic fever mammarenaviruses, Cell Host Microbe, vol.18, pp.705-713, 2015.

R. B. Brouillette, E. K. Phillips, N. Ayithan, and W. Maury, Differences in glycoprotein complex receptor binding site accessibility prompt poor crossreactivity of neutralizing antibodies between closely related arenaviruses, J. Virol, vol.91, pp.1454-1470, 2017.

A. Shimon, O. Shani, and R. Diskin, Structural basis for receptor selectivity by the Whitewater Arroyo mammarenavirus, J. Mol. Biol, vol.429, pp.2825-2839, 2017.

L. E. Clark, Vaccine-elicited receptor-binding site antibodies neutralize two New World hemorrhagic fever arenaviruses, Nat. Commun, vol.9, p.1884, 2018.

L. Zeitlin, Monoclonal antibody therapy for Junin virus infection, Proc. Natl Acad. Sci. USA, vol.113, pp.4458-4463, 2016.

J. M. Gershoni and A. Aronheim, Molecular decoys: ligand-binding recombinant proteins protect mice from curarimimetic neurotoxins, Proc. Natl Acad. Sci. USA, vol.85, pp.4087-4089, 1988.

D. J. Capon, Designing CD4 immunoadhesins for AIDS therapy, Nature, vol.337, pp.525-531, 1989.

K. Wycoff, Anti-infective immunoadhesins from plants, Plant Biotechnol. J, vol.13, pp.1078-1093, 2015.

C. M. Lawrence, Crystal structure of the ectodomain of human transferrin receptor, Science, vol.286, pp.779-782, 1999.

J. Abraham, K. D. Corbett, M. Farzan, H. Choe, and S. C. Harrison, Structural basis for receptor recognition by New World hemorrhagic fever arenaviruses, Nat. Struct. Mol. Biol, vol.17, pp.438-444, 2010.

Y. Cheng, O. Zak, P. Aisen, S. C. Harrison, and T. Walz, Structure of the human transferrin receptor-transferrin complex, Cell, vol.116, pp.565-576, 2004.

M. J. Bennett, J. A. Lebron, and P. J. Bjorkman, Crystal structure of the hereditary haemochromatosis protein HFE complexed with transferrin receptor, Nature, vol.403, pp.46-53, 2000.

L. C. Montemiglio, Cryo-EM structure of the human ferritin-transferrin receptor 1 complex, Nat. Commun, vol.10, p.1121, 2019.

M. Hezareh, A. J. Hessell, R. C. Jensen, J. G. Van-de-winkel, and P. W. Parren, Effector function activities of a panel of mutants of a broadly neutralizing antibody against human immunodeficiency virus type 1, J. Virol, vol.75, pp.12161-12168, 2001.

C. A. Diebolder, Complement is activated by IgG hexamers assembled at the cell surface, Science, vol.343, pp.1260-1263, 2014.

G. Helguera, An antibody recognizing the apical domain of human transferrin receptor 1 efficiently inhibits the entry of all new world hemorrhagic fever arenaviruses, J. Virol, vol.86, pp.4024-4028, 2012.

K. E. Maier, A new transferrin receptor aptamer inhibits new world hemorrhagic fever mammarenavirus entry, Mol. Ther. Nucleic Acids, vol.5, p.321, 2016.

A. I. Flyak, Mechanism of human antibody-mediated neutralization of Marburg virus, Cell, vol.160, pp.893-903, 2015.

A. Sanchez, Junin virus monoclonal antibodies: characterization and cross-reactivity with other arenaviruses, J. Gen. Virol, vol.70, pp.1125-1132, 1989.

M. E. Weinblatt, A trial of etanercept, a recombinant tumor necrosis factor receptor:Fc fusion protein, in patients with rheumatoid arthritis receiving methotrexate, N. Engl. J. Med, vol.340, pp.253-259, 1999.

M. C. Genovese, Abatacept for rheumatoid arthritis refractory to tumor necrosis factor alpha inhibition, N. Engl. J. Med, vol.353, pp.1114-1123, 2005.

F. Vincenti, A phase III study of belatacept-based immunosuppression regimens versus cyclosporine in renal transplant recipients (BENEFIT study)

, Am. J. Transplant, vol.10, pp.535-546, 2010.

B. E. Strober and K. Menon, Alefacept for the treatment of psoriasis and other dermatologic diseases, Dermatol. Ther, vol.20, pp.270-276, 2007.

H. M. Hoffman, Long-term efficacy and safety profile of rilonacept in the treatment of cryopryin-associated periodic syndromes: results of a 72-week open-label extension study, Clin. Ther, vol.34, pp.2091-2103, 2012.

H. Cohen-dvashi, N. Cohen, H. Israeli, and R. Diskin, Molecular mechanism for LAMP1 recognition by Lassa virus, J. Virol, vol.89, pp.7584-7592, 2015.

H. Cohen-dvashi, H. Israeli, O. Shani, A. Katz, and R. Diskin, Role of LAMP1 binding and pH sensing by the spike complex of Lassa virus, J. Virol, vol.90, pp.10329-10338, 2016.

Z. Otwinowski and W. Minor, Processing of X-ray diffraction data collected in oscillation mode, Method Enzymol, vol.276, pp.307-326, 1997.

P. Adams, PHENIX: a comprehensive Python-based system for macromolecular structure solution, Acta Crystallogr. Sect. D, vol.66, pp.213-221, 2010.

P. Emsley, B. Lohkamp, W. G. Scott, and K. Cowtan, Features and development of Coot, Acta Crystallogr. D, vol.66, pp.486-501, 2010.

, We are grateful to Gotthard Guillaume at the ESRF, Grenoble, France for providing assistance in using beamline ID30B. We thank Dr. Yosef Scolnik for his kind help in recording CD spectra, Dr. Emmanuel Levy for granting us access to his confocal microscope, Mr. Daniel J. Deer for technical support, and Dr. Deborah Fass for providing critical comments and suggestions. We thank Miles Carroll and Roger Hewson (Public Health England, Porton Down, UK) for providing the Machupo virus, Carvallo strain. BSL-4 experiments using MACV were supported by the Pasteur-Weizmann joint research program collaborative research grant S-CR18069-02 to M.M. and R.D. BSL-4 operations of the Galveston National Laboratory and Department of Microbiology and Immunology are supported by NIAID/NIH Grant No. UC7AI094660 to T, The lab of R.D. is supported by research grants from the Enoch Foundation, from the Abramson Family Center for Young Scientists, from Ms. Rudolfine Steindling, and from the I-CORE Program of the Planning and Budgeting Committee and The Israel Science Foundation