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. 2016 Oct 20;167(3):684-694.e9.
doi: 10.1016/j.cell.2016.09.049.

Cross-Neutralizing and Protective Human Antibody Specificities to Poxvirus Infections

Iuliia Gilchuk  1 , Pavlo Gilchuk  2 , Gopal Sapparapu  3 , Rebecca Lampley  1 , Vidisha Singh  1 , Nurgun Kose  1 , David L Blum  1 , Laura J Hughes  4 , Panayampalli S Satheshkumar  4 , Michael B Townsend  4 , Ashley V Kondas  4 , Zachary Reed  5 , Zachary Weiner  6 , Victoria A Olson  4 , Erika Hammarlund  7 , Hans-Peter Raue  7 , Mark K Slifka  7 , James C Slaughter  8 , Barney S Graham  9 , Kathryn M Edwards  10 , Roselyn J Eisenberg  11 , Gary H Cohen  12 , Sebastian Joyce  2 , James E Crowe Jr  13
Affiliations

Cross-Neutralizing and Protective Human Antibody Specificities to Poxvirus Infections

Iuliia Gilchuk et al. Cell. .

Abstract

Monkeypox (MPXV) and cowpox (CPXV) are emerging agents that cause severe human infections on an intermittent basis, and variola virus (VARV) has potential for use as an agent of bioterror. Vaccinia immune globulin (VIG) has been used therapeutically to treat severe orthopoxvirus infections but is in short supply. We generated a large panel of orthopoxvirus-specific human monoclonal antibodies (Abs) from immune subjects to investigate the molecular basis of broadly neutralizing antibody responses for diverse orthopoxviruses. Detailed analysis revealed the principal neutralizing antibody specificities that are cross-reactive for VACV, CPXV, MPXV, and VARV and that are determinants of protection in murine challenge models. Optimal protection following respiratory or systemic infection required a mixture of Abs that targeted several membrane proteins, including proteins on enveloped and mature virion forms of virus. This work reveals orthopoxvirus targets for human Abs that mediate cross-protective immunity and identifies new candidate Ab therapeutic mixtures to replace VIG.

Keywords: antigen specificity; cross-neutralization; human monoclonal antibodies; poxvirus infections; protective immunity; smallpox vaccine.

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Figures

None
Graphical abstract
Figure 1
Figure 1
Panel of Orthopoxvirus-Specific Human MAbs A panel of 89 human mAbs was generated based on reactivity to VACV-infected cell lysate or to VACV protein antigens. Individual mAbs were assessed for cross reactivity using CPXV, MPXV, and VARV-infected cell lysates or antigens. (A) Antigen specificity of purified mAbs. Reactivity of Abs of unknown antigen specificity that bound to inactivated VACV-infected cell lysate only is designated as “VACV lysate only.” (B) Representation of mAbs in the panel from (A) that bound only to VACV-infected cell lysate, recombinant VACV proteins, or both, VACV infected cell lysate and recombinant VACV proteins. See also Tables S3 and S4. (C) Cross-reactivity of mAbs that bound to VACV lysates from (B) to VACV-, CPXV-, MPXV-, or VARV-infected cell lysates. See also Figure S2. (D) Cross-reactivity of mAbs that bound to VACV antigens from (B) to the respective 12 ortholog proteins of VARV. Four mAbs with low expression were not tested. See also Tables S1 and S2.
Figure S1
Figure S1
Human Anti-D8 and Anti-H3 MAbs Targeted Diverse Epitopes of the Major VACV Surface Antigens, Related to Figure 1 Anti-D8 and anti-H3 mAbs from our panel were assessed for competitive binding to D8 and H3 proteins by biolayer interferometry. MAbs were judged to compete for the same site if maximum binding of second antibody was reduced to ≤ 39% of its un-competed binding (shown in black boxes). The mAbs were considered non-competing if maximum binding of second mAb was ≥ 61% of its un-competed binding (shown in white boxes). Gray boxes indicate an intermediate phenotype (competition resulted in between 40% and 60% of un-competed binding). Blue, yellow, cyan, green, and red dashed lines indicate designated competition groups. Antibodies that were selected for in vivo protection studies shown in red color. Two anti-H3 mAbs, MPXV-72 and MPXV-1, did not bind to antigen in biolayer interferometry and were distinguished as separate group from other anti-H3 mAbs.
Figure S2
Figure S2
Cross-Reactivity of Human MAbs to Orthopoxviruses, Related to Figure 1 Cross-reactivity of individual mAbs to different orthopoxviruses were assessed by ELISA using infected cell lysates or purified recombinant protein antigens. (A) Examples of mAbs within the panel that exhibited cross-reactivity to VACV, CPXV, MPXV, and VARV-infected cell lysates. Reactivity to VARV-infected cell lysate was measured at single mAb dilution as detailed in Table S3, ND indicates not determined. (B) Examples of four mAbs within the panel that exhibited cross-reactivity to VACV and VARV protein antigen orthologs. These four mAbs were included in mAb mixtures Mix4 and Mix6, which later were assessed for protective capacity in vivo. Data represent one of two independent experiments, shown as mean ± SD of assay triplicates.
Figure 2
Figure 2
Neutralizing and Cross-Neutralizing Potency of Human MAbs Individual mAbs were assessed for neutralization using MV or EV forms of VACV, CPXV, or MPXV. (A) Representation of individual mAbs within the panel that neutralized at least one of three Orthopoxvirus species. See also Table S5. (B) Relative abundance (shown in colors and with percent on the top of each bar) and number of VACV-neutralizing mAbs for each antigen specificity from (A). Anti-I1 and unknown specificity mAbs neutralized MPXV only. (C) Cross-neutralization of VACV, CPXV, or MPXV by individual mAbs from (A). (D) Cross-neutralizing potency of individual neutralizing mAbs from (A). Each symbol represents the mean ± SD of triplicate Emax values of individual mAbs. Antibodies later tested for protection in vivo (detailed below) are indicated in red.
Figure 3
Figure 3
Mixtures of Four or Six MAbs Possess High Cross-Neutralizing Activity for VACV, CPXV, MPXV, and VARV Neutralizing activity of mAbs or VIGIV was assessed using MV- and EV-neutralization assays. Mix6 included anti-L1, anti-H3, anti-A27, anti-D8, anti-B5, and anti-A33 mAbs. Mix4 included anti-L1, anti-A27, anti-B5, and anti-A33 mAbs. (A) VACV neutralization by individual mAbs or their mixtures, compared with VIGIV. MAb mixtures designations are listed in Table S6. (B) Cross-neutralizing activity of Mix4, Mix6 and VIGIV for VACV, CPXV, MPXV, or VARV (only the MV form was tested for VARV). Data represent one of two independent experiments, shown as mean ± SD of assay triplicates. See also Figure S3.
Figure S3
Figure S3
Cross-Neutralizing Activity of Human mAb Mixtures, Related to Figure 3 Cross-neutralizing activity of Mix6, Mix4, or VIGIV was assessed using MV-and EV-neutralization assays for VACV, CPXV, MPXV and VARV (MV form only for VARV). Data represent one of two independent experiments, shown as mean ± SD of assay triplicates.
Figure 4
Figure 4
Mix6 Provides Superior Protection against Lethal VACV Infection In Vivo Groups of C57BL/6 or BALB/c SCID mice representing, respectively, lower respiratory tract (A) or systemic dissemination (C) infection models, were inoculated i.p. with 1.2 mg of Mix6 or with 5 mg of VIGIV, or 1.2 mg of an irrelevant anti-dengue virus neutralizing mAb. The next day (d0) mice were challenged with a lethal dose of VACV and monitored for protection. (A) Protection from respiratory VACV infection that was mediated by Mix6, VIGIV, or vaccination with live VACV 3 weeks prior with a sub-lethal dose of VACV. (B) VACV titers assessed in the lungs of infected mice from (A) on day 7 p.i., shown as mean ± SEM; data represent one of two independent experiments with n = 5–10 mice per group. Dotted line indicates limit of detection (LOD) for the assay. (C) Protection from systemically disseminated lethal VACV infection that was mediated by Mix6. (D) Human mAb concentration in blood of treated mice from (C) at different times after treatment, shown as mean concentration ± SEM. One of two independent experiments, n = 3–5 mice per group.
Figure 5
Figure 5
Human mAb Specificities that Contribute to Protection against Lethal Respiratory VACV Infection C57BL/6 mice were inoculated i.p. 1 day prior to VACV challenge with 0.2 mg of individual mAbs or one of several mixtures designed to de-convolute protective mAbs specificities within Mix6. The next day (d0), mice were challenged IN with VACV and monitored for protection. (A) Protective capacity of individual mAbs of Mix6. Anti-D8 and -H3 specificities were inoculated as a mixture of three to five mAbs to those proteins from different competition-binding groups. (B) Protective capacity of mixtures that were based on Mix6 but had removal of a mAb for a single specificity, either L1, A27, D8, H3, A33, or B5. (C) Protective capacity of mixtures based on Mix4, Mix4 lacking anti-L1 mAb but with a 2-fold excess of anti-A27 mAb, or Mix4 lacking anti-B5 mAb but with a 2-fold excess of anti-A33 mAb. Data shown indicate mean ± SEM from one of two independent experiments using five to ten mice per group. mAb mixtures designations are listed in Table S6. See also Figures S4 and S5.
Figure S4
Figure S4
Protection against of Lethal Respiratory VACV Infection Is Mediated Principally by EV-Targeted MAbs, Related to Figure 5 Groups of C57BL/6 mice were inoculated IP with 1.2 mg of Mix6, or with 0.8 mg of Mix6 lacking two anti-EV mAbs (designated as Mix6(ΔEV)), or 0.4 mg of Mix6 lacking four anti-MV mAbs (designated as Mix6(ΔMV)), or 1.2 mg of an irrelevant anti-dengue virus neutralizing mAb. The next day (d0) mice were challenged by the IN route with a lethal dose of VACV and monitored for protection. (A) Protection from respiratory VACV infection that was mediated by Mix6(ΔEV). (B) Protection from respiratory VACV infection that was mediated by Mix6(ΔMV); Data represent one of two independent experiments with n = 5-10 mice per group. Percent (%) indicates survival by day 7.
Figure S5
Figure S5
Human mAb Specificities that Participate in Protection against Lethal Respiratory VACV Infection, Related to Figure 5 (A) C57BL/6 mice were inoculated i.p. one day prior to VACV challenge with 0.2 mg of individual anti-D8, -H3, -A27, or –L1 mAbs. The next day (day 0), mice were anesthetized and challenged IN with VACV under conditions promoting less severe upper airway infection (2 × 105 pfu VACV in 10 μl of PBS) and monitored for protection. Previously reported protective mouse anti-B5 mAb B126 and anti-H3 #41 (Benhnia et al., 2009, McCausland et al., 2010) served as control treatment for protection. (B) C57BL/6 mice received 400 μg of mAbs in the mixture designated as Mix4(ΔB5) (200 μg of anti-A33, 100 μg of anti-A27, and anti-L1) and was challenged with 10-fold higher (106 pfu) dose of VACV next day. Mice were monitored for protection and survival. Body weight is shown only for animals that survived. Percent figures near each curve indicate survival by day 7 based on endpoint criteria for euthanasia. Data showed mean ± SEM from one of two independent experiments using 5 to 10 mice per group.
Figure 6
Figure 6
Efficient Post-exposure Treatment Effect Mediated by Mix6 MAbs C57BL/6 mice were inoculated i.p. with 1.2 mg of Mix6 on the day before (d-1), or on the day of (d0), or day 1 to day 3 (d1–d3) after lethal IN challenge with VACV. The control group included mice pre-treated one day before challenge with 1.2 mg of an anti-dengue virus mAb. The body weight loss kinetics are shown for 14 days around the time of infection and treatment. Data are presented as mean ± SEM, using five to ten mice per group. Percent indicate survival based on endpoint criteria for euthanasia.
Figure 7
Figure 7
Human mAb Specificities that Contribute to Protection against Progressive Systemic VACV Infection (A and B) BALB/c SCID mice were challenged i.p. with 105 plaque forming units (pfu) VACV. The next day, mice were inoculated i.p. with 1.2 mg of Mix6, 5 mg of VIGIV, or 0.2 mg anti-L1, anti-A27, anti-D8, anti-H3, anti-B5, anti-A33, or irrelevant mAb. Body weight loss kinetics (A) and survival (B). Data in (A) shows body weight only for the animals that survived. Mean ± SEM, n = 5–6 mice per group. Each curve was compared to that of the irrelevant mAb-treated group on (B).
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