Inhibition of rotavirus replication by a non-neutralizing, rotavirus VP6–specific IgA mAb

Abstract

Rotaviruses are the leading cause of severe diarrheal disease in young children. Intestinal mucosal IgA responses play a critical role in protective immunity against rotavirus reinfection. Rotaviruses consist of three concentric capsid layers surrounding a genome of 11 segments of double-stranded RNA. The outer layer proteins, VP4 and VP7, which are responsible for viral attachment and entry, are targets for protective neutralizing antibodies. However, IgA mAb's directed against the intermediate capsid protein VP6, which do not neutralize the virus, have also been shown to protect mice from rotavirus infection and clear chronic infection in SCID mice. We investigated whether the anti-VP6 IgA (7D9) mAb could inhibit rotavirus replication inside epithelial cells and found that 7D9 acted at an early stage of infection to neutralize rotavirus following antibody lipofection. Using electron cryomicroscopy, we determined the three-dimensional structure of the virus-antibody complex. The attachment of 7D9 IgA to VP6 introduces a conformational change in the VP6 trimer, rendering the particle transcriptionally incompetent and preventing the elongation of initiated transcripts. Based on these observations, we suggest that anti-VP6 IgA antibodies confers protection in vivo by inhibiting viral transcription at the start of the intracellular phase of the viral replication cycle.

Functional Maturation of the Human Antibody Response to Rotavirus

“…After the virus has entered the cell, the outer capsid is released, exposing the VP6-coated double-layer particle (DLP), which then is activated for transcription. These anti-VP6 mAbs block viral transcription in vitro in a dose-dependent manner when introduced into a cell concurrently with DLPs or during transcytosis in the cell (3)(4)(5)(6). The specific role of such VP6 Abs in preventing or resolving human infection is still unclear.…”

“…Intracellular virus neutralization using DLPs, MA104 cells, and lipofectin was performed as described previously (4). The number of Ag-positive foci or fluorescent focus units in each well was counted by sweeping across one well of a 96-well plate using a ϫ10 objective.…”

Intraepithelial Cell Neutralization of HIV-1 Replication by IgA

“…During transport of IgA through mucosal epithelial cells, after polymeric Ig receptor (pIgR) 4 -mediated endocytosis, IgA Abs may also be able to interact intracellularly with viral proteins to inhibit viral replication. Evidence for such intraepithelial cell neutralization has been demonstrated in vitro with IgA mAbs against Sendai and measles viruses (paramyxoviruses), influenza virus (an orthomyxovirus), and rotavirus (a reovirus) (17)(18)(19)(20)(21)(22)37), but not yet with Abs to HIV (a retrovirus). In addition, neutralization (presumably intracellular) was shown in mice by an IgA mAb against a rotavirus internal protein, which was able both to prevent infection and cure persistent infection (17).…”

Distribution and phenotype of murine rotavirus-specific B cells induced by intranasal immunization with 2/6 virus-like particles

“…immunization have not been elucidated. Only VP6-specific sIgA produced by plasmocytes in the intestinal lamina propria (ILP) may participate to rotavirus clearance during transcytosis in epithelial cells [10,11]. However, it is assumed that nasal immunization leads to a restricted distribution of Ag-specific IgA in the upper aerodigestive and the urogenital tracts, but not in the intestine [12].…”