Adoptive B cell therapy for chronic viral infection

Abstract

T cell-based therapies have been widely explored for the treatment of cancer and chronic infection, but B cell-based therapies have remained largely unexplored. To study the effect of B cell therapy, we adoptively transferred virus-specific B cells into mice that were chronically infected with lymphocytic choriomeningitis virus (LCMV). Adoptive transfer of virus-specific B cells resulted in increase in antibody titers and reduction of viral loads. Importantly, the efficacy of B cell therapy was partly dependent on antibody effector functions, and was improved by co-transferring virus-specific CD4 T cells. These findings provide a proof-of-concept that adoptive B cell therapy can be effective for the treatment of chronic infections, but provision of virus-specific CD4 T cells may be critical for optimal virus neutralization.

Keywords: B cells; adoptive cell therapy; chronic viral infection; lymphocytic choriomeningitis virus (LCMV); virus.

Figure 1

Transfer of virus-specific B cells improves antibody levels in chronically infected mice. (A) Experimental outline for evaluating the effect of B cell transfer during a chronic viral infection. Mice chronically infected with LCMV Cl-13 WE-GP received 5x10⁶ KL25H B cells. (B) Representative FACS plots showing the frequencies of KL25 B cells in blood. (C) Summary of KL25H B cells in blood. CD45.1 expression was used to distinguish donor cells. (D) Summary of virus-specific antibody levels in sera by enzyme-linked immunosorbent assay (ELISA). Experiments were repeated 5 times, n=3-5 mice per group per experiment. Error bars represent SEM. The p-values were calculated using Mann-Whitney test. **P<0.005. Dotted line represents limit of detection.

Figure 2

Adoptive B cell therapy improves viral control. (A) Summary of viral control in sera. (B) Summary of viral loads in spleen. (C) Summary of viral loads in liver. Experimental layout was similar as the one depicted in Figure 1A. The limit of detection is indicated by a dashed line. Experiments were performed 3 times, n=2-5 mice per experiment. Error bars represent SEM. The p-values were calculated using Mann-Whitney test. *P<0.05, **P<0.005, ***P<0.0005. Dotted line represents limit of detection.

Figure 3

CD8 T cell responses are not significantly improved by adoptive B cell therapy. (A) Representative FACS plots showing the frequencies of LCMV-specific CD8 T cells in PBMCs at day 14 post-transfer. (B) Summary of LCMV-specific (GP276-specific) CD8 T cells. Experiments were performed 3 times, n=3-5 mice per experiment. Error bars represent SEM. The p-values were calculated using Mann-Whitney test. ns, not significant.

Figure 4

Antigen specificity is required for adoptive B cell therapy to be effective. (A) Experimental outline for evaluating the effect of B cell transfer during a chronic viral infection. Mice chronically infected with LCMV Cl-13 received 5x10⁶ KL25H B cells. (B) Summary of virus-specific antibody levels in sera. (C) Summary of viral loads in spleen. (D) Summary of viral loads in liver. The limit of detection is indicated by a dashed line. Experiments were performed 2 times, n=3-4 mice per experiment. Error bars represent SEM. The p-values were calculated using Mann-Whitney test. ns, not significant. Dotted line represents limit of detection.

Figure 5

The efficacy of adoptive B cell therapy is partly dependent on antibody effector functions. An Fc receptor blocking antibody (2.4G2) was administered intraperitoneally every three days, five times (500 μg/dose). (A) Summary of viral loads in spleen. (B) Summary of viral loads in liver. Experiments were performed 2 times, n=3-5 mice per experiment. Error bars represent SEM. The P values were calculated using the Kruskal-Wallis non-parametric ANOVA test. ns, not significant. *P<0.05, ***P<0.0005, ****P<0.0001. Dotted line represents limit of detection.

Figure 6

Virus-specific CD4 T cells enhance adoptive B cell therapy. (A) Experimental outline for evaluating whether LCMV-specific CD4 T cells augment the efficacy of adoptive B cell therapy. (B) Summary of viral loads in serum. (C) Summary of viral loads in spleen. (D) Summary of viral loads in liver. Experiments were performed 2 times, n=3-5 mice per experiment. Error bars represent SEM. The P values were calculated using the Kruskal-Wallis non-parametric ANOVA test. ns, not significant. *P<0.05, ***P<0.0005. Dotted line represents limit of detection.

Figure 7

Combined therapy with CD4 T cells and B cells enhances neutralizing antibody responses. Summary of neutralization assays, using 100 PFU of LCMV Cl-13 WE-GP virus, cultured with mouse sera (day 14 post-transfer). Sera were diluted 40-fold. Two days after infection, monolayers were stained with a fluorescently labeled anti-LCMV antibody (VL4) and results were plotted as focus forming units (FFU). Experiments were performed 2 times, n=3-5 mice per experiment. Error bars represent SEM. The P values were calculated using the Kruskal-Wallis non-parametric ANOVA test. ns, not significant, **P<0.005. Dotted line represents limit of detection.