Antibody is critical for the clearance of murine norovirus infection

Abstract

Human noroviruses cause more than 90% of epidemic nonbacterial gastroenteritis. However, the role of B cells and antibody in the immune response to noroviruses is unclear. Previous studies have demonstrated that human norovirus specific antibody levels increase upon infection, but they may not be protective against infection. In this report, we used murine norovirus (MNV), an enteric norovirus, as a model to determine the importance of norovirus specific B cells and immune antibody in clearance of norovirus infection. We show here that mice genetically deficient in B cells failed to clear primary MNV infection as effectively as wild-type mice. In addition, adoptively transferred immune splenocytes derived from B-cell-deficient mice or antibody production-deficient mice were unable to efficiently clear persistent MNV infection in RAG1(-/-) mice. Further, adoptive transfer of either polyclonal anti-MNV serum or neutralizing anti-MNV monoclonal antibodies was sufficient to reduce the level of MNV infection both systemically and in the intestine. Together, these data demonstrate that antibody plays an important role in the clearance of MNV and that immunoglobulin G anti-norovirus antibody can play an important role in clearing mucosal infection.

FIG. 1.

B cells limit MNV replication and are required for MNV clearance in the distal ileum and MLN. Virus titers in the distal ilea (A) and MLN (B) of B6 and μMT mice. These data are pooled from at least two independent experiments with five mice per group in each experiment, and each symbol indicates a sample from an individual mouse. *, P < 0.05. LD, limit of detection.

FIG. 2.

Antibody responses and capacity of adoptively transferred immune splenocytes to clear enteric MNV infection. (A) Levels of serum anti-MNV IgG antibody determined by ELISA (1:100 serum dilution) in mock- and MNV-immunized wild-type B6 mice 35 to 42 days postinfection. (B) Virus titers in the distal ileum of persistently infected RAG1^−/− mice 6 days after transfer of medium alone, nonimmune splenocytes, or immune splenocytes. These data are pooled from three independent experiments with three to five mice per group in each experiment. **, P < 0.0001; *, P < 0.05. LD, limit of detection.

FIG. 3.

B cells and antiviral antibody production are essential for efficient clearance of MNV infection from intestine of persistently infected RAG1^−/− mice. Virus titers in the duodena/jejuna (A and C) and distal ilea (B and D) of persistently infected RAG1^−/− recipients after adoptive transfer of medium (mock), immune wild type, μMT splenocytes (A and B) or HELMET splenocytes (C and D). These data are pooled from three independent experiments with three to five mice per group in each experiment. **, P < 0.0001; *, P < 0.05. LD, limit of detection.

FIG. 4.

Immune serum and neutralizing IgG MAbs reduce MNV infection from intestines and spleens of RAG1^−/− mice. Virus titers in distal ilea (A and C) and spleens (B and D) of persistently infected RAG1^−/− recipients 6 days after passive transfer of either immune serum (A and B) or neutralizing MAbs specific for capsid protein (C and D). These data are pooled from three independent experiments with three mice per group in each experiment. **, P < 0.0001; *, P < 0.05. LD, limit of detection.