No abstract

Immunoglobulin A (IgA) monoclonal antibodies (MAbs) directed at the conserved inner core protein VP6 of rotavirus, such as the IgA7D9 MAb, provide protective immunity in adult and suckling mice when delivered systemically. While these antibodies do not have traditional in vitro neutralizing activity, they could mediate their antiviral activity either by interfering with the viral replication cycle along the IgA secretory pathway or by acting at mucosal surfaces as secretory IgA and excluding virus from target enterocytes. We sought to determine the critical step at which antirotaviral activity was initiated by the IgA7D9 MAb. The IgA7D9 MAb appeared to directly interact with purified triple-layer viral particles, as shown by immunoprecipitation and immunoblotting. However, protection was not conferred by passively feeding mice with the secretory IgA7D9 MAb. This indicates that the secretory IgA7D9 MAb does not confer protection by supplying immune exclusion activity in vivo. We next evaluated the capacity of polymeric IgA7D9 MAb to neutralize rotavirus intracellularly during transcytosis. We found that when polymeric IgA7D9 MAb was applied to the basolateral pole of polarized Caco-2 intestinal cells, it significantly reduced viral replication and prevented the loss of barrier function induced by apical exposure of the cell monolayer to rotavirus, supporting the conclusion that the antibody carries out its antiviral activity intracellularly. These findings identify a mechanism whereby the well-conserved immunodominant VP6 protein can function as a target for heterotypic antibodies and protective immunity.Rotavirus (RV) is the main cause of severe diarrhea in young infants worldwide and is responsible for 611,000 deaths per year (36). Two vaccines based on attenuated live viruses have recently completed successful phase III clinical trials and showed efficacy in preventing severe RV diarrhea caused by multiple serotypes (45, 50). However, the relevant immune effectors required for achieving protection against diverse circulating strains are still a matter of considerable debate. While CD8 ϩ T cells facilitate the timely clearance of rotavirus infection, B cells with the appropriate pattern of mucosal homing receptors and antibody production have been demonstrated as crucial for protection from reinfection (17, 24).Neutralizing antibodies against RV that block viral replication in cell culture are felt to play a major role in defense. A variety of passive antibody transfer studies in animals (28), as well as immunization studies using selected rotavirus reassortants in humans (7), have demonstrated a clear role for VP4 and VP7 in protective immunity. Neutralizing antibodies are directed against the outer shell VP4 and VP7 proteins, whose variable antigenic specificities define multiple serotypes, assigned as P and G serotypes, respectively (41). Worldwide, the G1-to-G4 serotypes associated with P4 and P8 and the more recently described G9/P6 or P8 serotypes are globally important rotavirus G/P combinations in human...

To evaluate whether the rectal route of immunization may be used to provide appropriate protection against enteric pathogens such as rotaviruses (RV), we studied the antibody response and the protection induced by rectal immunization of mice with RV virus-like particles (VLP). For this purpose, 6-week-old BALBc mice were rectally immunized twice with RV 8-2/6/7-VLP derived from the bovine RV RF81 strain either alone or combined with various adjuvants including four toxins [cholera toxin (CT) and three attenuated Escherichia coli-derived heat-labile toxins (LTs), LT(R192G), LT(R72), and LT ( Rotaviruses (RV) are the leading cause of viral gastroenteritis in young children worldwide and are responsible for more than 500,000 deaths per year in developing countries (40). The high mortality rate in developing countries and the heavy social and economical burden in industrialized countries due to RV infections underline the need for the development of an efficient vaccine. Every candidate RV vaccine that has been developed to date has consisted of orally delivered, live attenuated RV strains or reassortants (8,9,14,20,36,54,56). Most of these vaccines confer significant protection against severe diarrhea but only limited protection against RV infection or mild symptoms. Moreover, live vaccines can be associated with various adverse effects, intussusception being the most severe (33). Thus, the development of new safe vaccine strategies based on nonliving RV should be considered.Virus-like particles (VLP) are nonreplicating structures that mimic virus counterparts in morphology and immunogenicity and could be safe and efficient vaccine candidates. Parenteral immunization with RV VLP has been shown to induce immunogenicity and protection in animal models, particularly in the mouse model (7,11,30). However, RV is commonly transmitted via the fecal-oral route and infects intestinal epithelial cells. Thus, vaccine strategies inducing effective intestinal mucosal immunity responses should be suitable against this pathogen and need to be assessed. RV VLP can be delivered via various mucosal routes of administration in order to induce mucosal effectors. When delivered via the oral route, which is common and handy for vaccine administration, RV VLP induce weak immune responses and do not protect against infection (3, 49). When administered by the nasal route, RV VLP efficiently induce both local and systemic specific immune responses in mice (6,29,34,35) and gnotobiotic pigs (21).

This systemic and continuous scopolamine-induced model of dry eye in the rat may represent a helpful tool to investigate moderate dry eye, and makes a contribution in the field of dry eye study.