Divergence of variant binding/neutralizing antibodies following SARS-CoV-2 booster vaccines in myeloma: Impact of hybrid immunity

Abstract We characterized virus-neutralization and spike-binding antibody profiles in myeloma patients following monovalent or bivalent-SARS-CoV-2 booster vaccination. Vaccination improves the breadth of binding antibodies but not neutralization activity against current variants. Hybrid immunity and immune imprinting impact vaccine-elicited immunity.

immunization, two booster immunizations, and a bivalent booster administered 1-6 months after the third dose (n=42).The nAb titers against the ancestral strain (WA1) in patients that received the bivalent booster were 2.3-fold higher than neutralization titers in patients that received the monovalent booster (Figure S1).nAbs against BA.1 and BA.5 after monovalent or bivalent booster had lower titers compared to WA1, with a reduction in neutralization potency ranging between 7.1-8.2-foldfor BA.1 and between 8.9-12.4-foldfor BA.5 (Figure S1).Neutralizing antibodies against the newly circulating Omicron variants BQ.1.1 and XBB.1.5were low or undetectable.
Detection of anti-nucleocapsid (NC) binding antibodies (900 AU/ml as cutoff) was utilized as evidence of recent SARS-CoV-2 exposure (12).In the monovalent-boosted group, 45.5% of the monovalent-boosted patients were anti-NC+ (n=46) (Figure S2).Next, we compared neutralization and antibody binding titers between individuals with low/undetectable anti-NC antibodies and those with recent SARS-CoV-2 exposure.In the monovalent-boosted group, the neutralization titers against WA1 were 11-fold higher in patients with recent SARS-CoV-2 exposure compared to unexposed patients (Geometric Mean Titer [GMT] 1379 vs 125).
Neutralization titers against Omicron variants BA.1 (GMT 134 vs. 28), BA.5 (GMT 95 vs. 24), BQ.1.1 (GMT 38 vs. 20.5),and XBB.1.5(GMT 30 vs. <20) were higher in SARS-CoV-2 exposed compared to unexposed patients (Figure 1A).We then assessed the temporal distribution of sampling among the monovalent-boosted group.In Figure 1B, antibody titers against WA1 are shown to indicate that most of the samples (69% and 59% in unexposed and exposed patients, respectively) were collected at time points under 50 days after immunization.However, a higher proportion of responders to multiple variants was observed among samples collected from exposed patients compared to unexposed patients at time points over 50 days after vaccination (Figure 1C).
Consistent with high community spread and breakthrough infections with the Omicron variant, we found that 73.8% of the bivalent-boosted patients were anti-NC+ (n=31) (Figure S2).In the bivalent-boosted group, the neutralization titers against WA1 showed modestly elevated titers (1.3 fold) in patients with recent SARS-CoV-2 exposure compared to unexposed patients (GMT 894 vs. 676).Neutralization titers were elevated against Omicron variants BA.1 (GMT 139 vs. 42), BA.5 (GMT 87 vs. 32), BQ.1.1 (GMT 43 vs. 22), and XBB.1.5(GMT 33.5 vs. <20) in SARS-CoV-2-exposed compared to unexposed patients (Figure 1D).The temporal distribution of sampling among the bivalent-boosted group (Figure 1E) showed that most of the samples (91% and 87% in unexposed and exposed patients, respectively) were collected at time points over 50 days after immunization.A higher proportion of responders to multiple variants were present among samples collected from exposed patients compared to unexposed patients at time points over 50 days after vaccination (Figure 1F).
We next determined the IgG binding titers using Spike-specific electrochemiluminescence assays (11).Nearly all samples across the two cohorts tested positive for SARS-CoV-2 Spike-IgG binding (97%), except four unexposed SARS-CoV-2 patients receiving a monovalent booster.We tested a panel of pre-Omicron and Omicron Spike variants and found significantly higher binding titers in exposed SARS-CoV-2 patients that received a monovalent booster as compared to unexposed patients (P <0.0001; Figure 2A).In contrast, we did not observe a statistically significant difference in the bivalent vaccinated group (Figure 2B).In all the data points tested with sera samples collected from patients that received boosting immunization with monovalent or bivalent vaccines, no differences were observed between binding IgG titers to the Spike protein from early variants (B.1.1.7,B.1.351,and B.1.617.2) and the binding IgG titers to the Spike protein from the ancestral SARS-CoV-2 strain (Figure S3).However, in SARS-CoV-2 unexposed and exposed patients, differences were observed between the IgG antibody response against the Spike protein from the ancestral SARS-CoV-2 strain and the IgG response against most of the Omicron variants (Figure S3).
We next analyzed the clinical correlates of neutralizing antibodies against WA1 and the contemporary XBB.1.5variant as described (10, 13) (Tables S1 and S2).Anti-CD38 therapy correlated with reduced induction of nAb against WA1 in both cohorts of patients that received monovalent and bivalent boosters (Table S2).nAb against XBB-1 were low in all subsets and not impacted by these variables (Table S1).
This study shows that although bivalent vaccination induced significantly higher nAb titers against the ancestral strain in unexposed individuals, compared to those induced by monovalent boosters, titers against circulating Omicron variants (e.g., XBB.1) were very low or undetectable.
Hybrid immunity enabled higher induction of broadly reactive nAbs.However, there was no correlation between Spike-binding antibodies and neutralization against circulating variants, suggesting that vaccination elicited antibodies that are not neutralizing.The inability to elicit antibodies against neutralizing epitopes suggests that a vaccination regimen with repeat boosters or using different vaccine platforms is needed to improve the effect of bivalent booster immunization in MM patients.
We have reported that a single monovalent booster vaccine is associated with increased nAb against the ancestral strain and the B.1.617.2 variant but not the Omicron variants in MM patients (10).It has been suggested that immune imprinting provided by prior infection or SARS-CoV-2 vaccination negatively impacts vaccine immunogenicity of booster immunizations (14).Consistent with this, we observed preferential boosting of nAb against the ancestral WA1 strain following booster immunization.Booster immunization particularly improved the breadth and longevity of the antibody response in patients with hybrid immunity.These results may be linked to the further expansion of class-switched memory B cells, described previously following monovalent boosters in MM (10).As with monovalent vaccines (10), patients with prior anti-CD38 antibodies also exhibit poor response to bivalent vaccines, which may relate to the adverse impact of these therapies on B/plasma cells and T-follicular-helper cells.The need for multiple vaccines in MM patients may not be SARS-CoV-2-specific, as multiple vaccines were also shown to improve seroprotection following influenza vaccination in a randomized trial in MM (15).Overall, our data show that most MM patients lack detectable nAb against current Omicron variants despite bivalent booster immunization.Spike-binding IgG antibodies against several Omicron variants were detected, suggesting that while immune imprinting may impact the induction of broadly neutralizing antibodies, reduced nAbs following vaccination in MM is not due to the inability to produce antibodies.High-risk cohorts of MM patients, such as those with prior CD38 or BCMA targeting therapies, may be at particular risk for ongoing reinfections with these viruses and may need consideration of newer approaches, including additional boosters or newer vaccine platforms.

Figure 1 .
Figure 1.Live virus neutralizing antibody titers against WA1, BA.1, BA.5, BQ.1.1,and XBB.1.5after monovalent or bivalent mRNA booster vaccination in patients with MM. (A) Comparative response of samples collected from MM patients after monovalent booster immunizations.Black lines, patients without evidence of natural exposure to SARS-CoV-2.Red lines, patients with natural exposure to SARS-CoV-2 by confirmation of positive anti-nucleocapsid binding antibodies.Dark black and dark red lines represent the geometric mean titers (GMT).The focus reduction neutralization test (FRNT50 [the reciprocal dilution of serum that neutralizes 50% of the input virus]) geometric mean titer (GMT) of neutralizing antibodies against the WA1 strain, and each Omicron subvariants is shown at the top of the panel, GMT values in black unexposed patients, GMT values in red patients exposed to SARS-CoV-2 infections.B) Time course of FRNT titers against WA1 in patients that received monovalent immunization and were unexposed (gray symbols) or exposed (red symbols) to SARS-CoV-2.C) Percentage of responders against individual variants tested at time points over 50 days, among unexposed (gray bars) or exposed (red bars) to SARS-CoV-2 that received monovalent booster immunization.D) Comparative response of samples collected from MM patients after bivalent booster immunizations.Black lines, patients without evidence of natural exposure to SARS-CoV-2.Red lines, patients with natural exposure to SARS-CoV-2 by confirmation of positive anti-nucleocapsid binding antibodies.Dark black and dark red lines represent the GMT of neutralizing antibodies against the virus tested.GMT of neutralizing antibodies is shown at the top of the panel, with GMT values in black unexposed patients and GMT values in red patients exposed to SARS-CoV-2 infections.E) Time course of FRNT titers against WA1 in patients that received bivalent immunization and were unexposed (gray symbols) or exposed (red symbols) to SARS-CoV-2.F) Percentage of responders against individual variant tested at time points over 50 days, among unexposed (gray bars) or exposed (red bars) to SARS-CoV-2 that received bivalent booster immunization.

Figure 2 .
Figure 2. SARS-CoV-2 Spike-binding IgG antibody titers in MM patients that received a monovalent or bivalent booster immunization.Antibody responses were measured by electrochemiluminescence using the Meso Scale Discovery (MSD) platform.(A) Comparative response of samples collected from MM patients after monovalent booster immunizations.Black lines, patients without evidence of natural exposure to SARS-CoV-2.Red lines, patients with natural exposure to SARS-CoV-2 by confirmation of positive anti-nucleocapsid binding antibodies (titer >900 AU/ml).Dark black and dark red lines represent the geometric mean titers (GMT).B) Comparative response of samples collected from MM patients after bivalent booster immunizations.Black lines, patients without evidence of natural exposure to SARS-CoV-2.Red lines, patients with natural exposure to SARS-CoV-2 by confirmation of positive anti-nucleocapsid binding antibodies (titer >900 AU/ml).Dark black and dark red lines represent the geometric mean titers (GMT).Prepandemic plasma samples from healthy individuals were used to set the detection cutoff levels for SARS-CoV-2 Spike-specific IgG antibody titers.