REAGENT or RESOURCE	SOURCE	IDENTIFIER
Antibodies
19.7E	Robinson et al.19	Patent WO2018106712A1
12.1F	Robinson et al.19	Patent WO2018106712A1
25.10C	Robinson et al.19	Patent WO2018106712A1
37.7H	Robinson et al.19	Patent WO2018106712A1
LAVA01	This study	N/A
LAVA02	This study	N/A
LAVA03	This study	N/A
LAVA04	This study	N/A
Goat anti-mouse	Seracare	Cat# 5450-0011
HRP-labeled goat anti-rabbit IgG	Jackson Immunoresearch	Cat# 111-035-144
HRP-labeled donkey anti-guinea pig IgG	Jackson Immunoresearch	Cat# 706-035-148
Donkey anti-rabbit IgG-PE	Biolegend	Cat# 406421
Goat-anti-rabbit IgM-PE	Southern Biotech	Cat# 4020-09
PE-labeled anti-human CD16 antibody	Biolegend	Cat# 302008
Fixable Viability Dye eF780	eBioscience	Cat# 65-0865-14
Bacterial and virus strains
Lassa virus (Josiah strain)	Philipps-University Marburg	GenBank: P08669
Guinea-pig adapted Lassa virus (Josiah strain)	Safronetz et al.35	GenBank: P08669
NEB 5-alpha Competent E. coli (High Efficiency)	New England Biolabs	Cat# C2987H
Biological samples
Sera immunized rabbits	This study	N/A
Sera immunized guinea pigs	This study	N/A
PBMCs immunized rabbits	This study	N/A
PBMCs naïve humans	Sanquin Blood bank Amsterdam	N/A
Chemicals, peptides, and recombinant proteins
I53-50B.4PT1	Walls et al.44	N/A
IL-15	Thermo Scientific	Cat# BMS319
Tween20	Sigma-Aldrich	Cat# P1379-500ML
Bovine Serum Albumin (fraction V)	Thermo Scientific	Cat# 9048-46-8
Milk powder	PanReac AppliChem	Cat# A0830
1% 3,3′,5,5′-tetranethylbenzidine	Sigma-Aldrich	Cat# 88748
EDTA (Titriplex III)	Sigma-Aldrich	Cat# 1.08418.1000
Saquinavir	NIH-ARP	Cat# 4658
DEAE-dextran	Sigma-Aldrich	Cat# D9885
Mass spectrometry grade trypsin	Promega	Cat# V5280
Sequencing grade chymotrypsin	Promega	Cat# V1061
Alpha lytic protease	Sigma-Aldrich	Cat# A6362
Acetonitrile, 80%, 20% Water with 0.1% Formic Acid, Optima LC/MS	Thermo Scientific	Cat# 15431423
Water with 0.1% Formic Acid (v/v), Optima™ LC/MS Grade	Thermo Scientific	Cat# LS118-212
Acetonitrile	Thermo Scientific	Cat# 10489553
Trifluoroacetic acid	Thermo Scientific	Cat# 10155347
Dithiothreitol	Sigma-Aldrich	Cat# 43819
Iodacetamide	Sigma-Aldrich	Cat# I1149
Phorbol myristate acetate (PMA)	Sanbio	Cat# P8139-1MG
Urea	Sigma-Aldrich	U5378-1KG
Glu-C	Promega	Cat# V1651
BioLock solution	IBA Lifesciences	Cat# 2-0205-050
Reporter Lysis buffer	Promega	Cat# E3971
PBS	Thermo Scientific	Cat# 10010023
TBS	Alfa Aesar	Cat# J60764.K2
Glutaraldehyde	Sigma-Aldrich	Cat#
PEI MAX	Polysciences	Cat# 24765-1
3,3’,5,5’-tetranethylbenzidine	Sigma-Aldrich	Cat# T4444
Squalene Emulsion adjuvant	Polymun Scientific	N/A
AEC chromogen	Enquire Bioreagents	Cat# AB64252
Galanthus Nivalis Lectin	Vector Laboratories	Cat# L-1240-5
Amersham High Molecular Weight marker	Sigma-Aldrich	Cat# 17-0445-01
1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide	Thermo Scientific	Cat# A35391
Sulfo-N-Hydroxysulfosuccinimide	Thermo Scientific	Cat# A39269
Casein buffer	Thermo Scientific	Cat# 37528
Penicillin	Sigma-Aldrich	Cat# P3032-10MI
Streptomycin	VWR	Cat# 382-EU-100G
Penicillin-Streptomycin (5,000 U/mL)	Gibco	Cat# 15070063
Gentamicin	Corning	Cat# 30-005-CR
Fugene	Promega	Cat# E5911
Carboxymethylcellulose	Thermo Scientific	Cat# M352-500
Neutral buffered formalin	Thermo Scientific	Cat# 245-684
Ionomycin	Sanbio	Cat# 10004974-5
Streptavidin BB515	BD	Cat# 564453
Streptavidin AF647	Biolegend	Cat# 405237
Streptavidin BV421	Biolegend	Cat# 405226
Lauryl maltose neopentyl glycol	Anatrace	Cat# NG310
Uranyl Formate	Electron Microscopy Sciences	Cat #D310 25 GM
Critical commercial assays
Bright-Glo Luciferase Assay System	Promega	Cat# E2620
Deposited data
3D map of GPCysR4(Josiah) from localized reconstruction of GPCysR4(Josiah)-I53-50NP	This paper	EMDB: EMD-25107
3D model of GPCysR4(Josiah) from localized reconstruction of GPCysR4(Josiah)-I53-50NP	This paper	PDB: 7SGD
3D map of I53-50NP from focused refinement of GPCysR4(Josiah)-I53-50NP	This paper	EDMB: EMD-25108
3D model of I53-50NP from focused refinement of GPCysR4(Josiah)-I53-50NP	This paper	PDB: 7SGE
3D map of GPCysR4(Josiah)-I53-50A.1NT1 in complex with LAVA01 antibody	This paper	EMDB: EMD-25109
3D model of GPCysR4(Josiah)-I53-50A.1NT1 in complex with LAVA01 antibody	This paper	PDB: 7SGF
Experimental models: Cell lines
FreeStyle 293F cells	Thermo Scientific	Cat# R79007
HEK 293T cells	ATCC	Cat# CRL-11268
Vero cells	ATCC	Cat# CCL-81
Vero E6 cells	ATCC	Cat# CRL-i586
TZM-bl cells	NIH ARRRP	Cat# 8129
THP-1 cells	ATCC	Cat# TIB-202
Experimental models: Organisms/strains
New Zealand White rabbits	Covance Research Products, Inc	N/A
Hartley Guinea Pigs	UTMB	N/A
Recombinant DNA
GPCysR4(Josiah)-StreptagII pPPI4 plasmid	This study	N/A
GPCysR4(Josiah)-I53-50A.1NT1-Strep-tagII pPPI4 plasmid	This study	N/A
GPCysR4(Josiah)-I53-dn5B-StreptagII pPPI4 plasmid	This study	N/A
GPCysR4(Josiah)-I53-50A.1NT1-Avi-His pPPI4 plasmid	This study	N/A
GPCysR4(NIG08-A41)-I53-50A.1NT1-Avi-His pPPI4 plasmid	This study	N/A
Furin pPPI4 plasmid	Brouwer et al.29	N/A
Fc-tagged LAMP-1 ectodomain	Jae et al.15	N/A
19.7E HC, 19.7E LC, 12.1F HC, 12.1F LC, 25.10C HC, 25.10C LC, 37.7H HC, 37.7H LC gene fragments	Integrated DNA Technologies	N/A
Software and algorithms
Dynamics	Wyatt Technology Corporation	N/A
ByosTM (Version 4.0)	Protein Metrics Inc.	https://www.proteinmetrics.com/products/byonic/
GraphPad Prism v8	GraphPad	N/A
XCalibur Version v4.2	Thermo Scientific	N/A
Orbitrap Fusion Tune application v3.1	Thermo Scientific	N/A
FlowJo v.10.7.1	Flowjo	N/A
UCSF ChimeraX	Goddard et al.45	N/A
cryoSPARC.v2	Punjani et al.46	N/A
Leginon	Suloway et al.47	N/A
MotionCor2	Zheng et al.48	N/A
GCTF	Zhang49	N/A
Relion/3.0	Zivanov et al.50	N/A
Localized Reconstruction v1.2.0	Ilca et al.51	N/A
AbodyBuilder	Leem et al.52	N/A
Coot	Casañal et al.53	N/A
EMRinger	Barad et al.54	N/A
MolProbity	Williams et al.55	N/A
Appion	Lander et al.56	N/A
Other
EasySpray PepMap RSLC C18 column (75 μm x 75 cm)	Thermo Scientific	Cat# ES805
Fetal bovine serum	R&D Biosystems	Cat# S11150H
Fetal calf serum	Gibco	Cat# 10270/106
C18 ZipTip	Merck Milipore	Cat# ZTC18S008
Immobilized papain resin	Thermo Scientific	Cat# 20341
Protein A resin	Thermo Scientific	Cat# 20333
CD56 MicroBeads, human	Miltenyi Biotec	Cat# 130-050-401
CaptureSelect IgG-Fc resin	Thermo Scientific	Cat# 2942852010
FluoSpheres NeutrAvidin-Labeled Microspheres	Thermo Scientific	Cat# F8776
Vivaspin 6, 10.000 Da MWCO, polyethersulfone	Sigma-Aldrich	Cat# GE28-9322-96
Vivaspin 20, 50.000 Da MWCO, polyethersulfone	Sigma-Aldrich	Cat# GE28-9323-62
Vivaspin 500, 3.000 Da MWCO, polyethersulfone	Sigma-Aldrich	Cat# GE28-9322-18
Amicon 15, 10.000 Da MWCO, cellulose	Sigma-Aldrich	Cat# UFC901024
Slide-A-Lyzer Mini dialysis device 10 kDa MWCO	Thermo Scientific	Cat# 88401
PepMap100 C18 3UM 75UMx2CM Nanoviper	Thermo Scientific	Cat# 164946
Ni-NTA agarose	QIAGEN	Cat# 30210
Novex Wedgewell 10-20% Tris-Glycine gels	Thermo Scientific	Cat# XP10202BOX
NuPAGE 4-12% Bis-Tris gels	Thermo Scientific	Cat# NP0321BOX
Superose 6 increase 10/300 GL	Sigma-Aldrich	Cat# GE29-0915-96
HiLoad 16/600 Superdex pg200	Sigma-Aldrich	Cat# GE28-9893-35
Econo-column chromatography columns	BIO RAD	Cat# 7371512
NGC chromatography system	BIO RAD	N/A
Octet K2 system	Sartorius (FortéBio)	N/A
Octet Biosensors: Streptavidin	Sartorius (FortéBio)	Cat# 18-5019
Octet Biosensors: Protein A	Sartorius (FortéBio)	Cat# 18-5010
Octet Biosensors: Anti-Human Fc Capture (AHC)	Sartorius (FortéBio)	Cat# 18-5060
Nucleobond Xtra Maxi kit	Macherey-Nagel	Cat# 740414.50
Fast Digest BamHI	Thermo Scientific	Cat# FD0054
Fast Digest Green buffer 10x	Thermo Scientific	Cat# B72
Fast Digest PstI	Thermo Scientific	Cat# FD0614
Fast Digest NotI	Thermo Scientific	Cat# FD0593
Random Hexamer Primers	Thermo Scientific	Cat# SO142
dNTP mix	New England Biolabs	Cat# N0447S
HotStarTaq Plus DNA polymerase	Qiagen	Cat# 203603
Biotin protein ligase	GeneCopoeia	Cat# BI001
T5 exonuclease	New England Biolabs	Cat# M0363
Taq DNA ligase	New England Biolabs	Cat# M0208S
NAD+	New England Biolabs	Cat# B9007S
Superscript III RTase	Thermo Fischer	Cat# 18080044
Phusion High-Fidelity DNA Polymerase	New England Biolabs	Cat# M0530S
Magplex Microspheres	Luminex	Cat# MC10065-01
FreeStyle 293 Expression medium	Thermo Scientific	Cat# 12338018
Ficoll-Paque™ PLUS	Sigma-Aldrich	Cat# GE17-1440-02
DMEM	Gibco	Cat# 11965092
OptiMEM	Gibco	Cat# 31985-070
Iscove's Modified Dulbecco's Medium	Gibco	Cat# 12440053
RPMI 1640 Medium	Gibco	Cat# 11875093
Glutamax supplement	Thermo Scientific	Cat# 35050061
L-Glutamine	Gibco	Cat# 25030149
High-binding plates: Half-area 96-well polystyrene high-binding microplate	Greiner	Cat# 675061
Steritop Filter Units	Merck Millipore	Cat# C3239
QuantiFoil R 2/1 grids (400-mesh)	Thermo Scientific	Cat# 50-190-2583
UltrAuFoil R 1.2/1.3 grids (300-mesh)	Quantifoil Micro Tools GmbH	N/A
Glomax reader	Turner BioSystems	Model# 9101-002
Microplate 96 well half area white	Greiner bio-one	Cat# 675074
FACSymphony A1 Cell Analyzer	BD biosciences	N/A
FACS-ARIA-SORP	BD biosciences	N/A
Greiner CELLSTAR® 96 well plates round bottom clear wells	Merck Millipore	Cat# M9436
Strep-TactinXT Superflow high capacity resin	IBA Life Sciences	Cat# 2-4010-010
NanoDrop 2000C	Thermo Scientific	Cat# ND-2000C
Prometheus NT.48 NanoDSF	NanoTemper Technologies	N/A
Dynapro Nanostar	Wyatt Technology Corporation	N/A
Orbitrap Eclipse mass spectrometer	Thermo Scientific	N/A
Ultimate 3000 HPLC	Thermo Scientific	N/A
Vitrobot mark IV	Thermo Scientific	N/A
Solarus 950 plasma system	Gatan	N/A
FEI Titan Krios	Thermo Scientific	N/A
K2 Summit direct electron detector camera	Gatan	N/A
MAGPIX system	Luminex	Model# MAGPIX-XPON4.1-CEIVD