Anterior cervical plating.

Although anterior cervical instrumentation was initially used in cervical trauma, because of obvious benefits, indications for its use have been expanded over time to degenerative cases as well as tumor and infection of the cervical spine. Along with a threefold increase in incidence of cervical fusion surgery, implant designs have evolved over the last three decades. Observation of graft subsidence and phenomenon of stress shielding led to the development of the new generation dynamic anterior cervical plating systems. Anterior cervical plating does not conclusively improve clinical outcome of the patients, but certainly enhances the efficacy of autograft and allograft fusion and lessens the rate of pseudoarthrosis and kyphosis after multilevel discectomy and fusions. A review of biomechanics, surgical technique, indications, complications and results of various anterior cervical plating systems is presented here to enable clinicians to select the appropriate construct design.

Protective effect of rotavirus VP6-specific IgA monoclonal antibodies that lack neutralizing activity.

Rotaviruses are the leading cause of severe gastroenteritis and dehydrating diarrhea in young children and animals worldwide. A murine model and "backpack tumor" transplantation were used to determine the protective effect of antibodies against VP4(an outer capsid viral protein) and VP6(a major inner capsid viral protein). Only two non-neutralizing immunoglobulin A (IgA) antibodies to VP6 were capable of preventing primary and resolving chronic murine rotavirus infections. These antibodies were not active, however, when presented directly to the luminal side of the intestinal tract. These findings support the hypothesis that in vivo intracellular viral inactivation by secretory IgA during transcytosis is a mechanism of host defense against rotavirus infection.

Cleavage of rotavirus VP4 in vivo.

The infectivity of rotavirus particles is dependent on proteolytic cleavage of the outer capsid protein, VP4, at a specific site. This cleavage event yields two fragments, identified as VP5* and VP8*. It has been hypothesized that the particle is more stable, but non-infectious, when VP4 is in the uncleaved state. Uncleaved VP4 and the resultant increased stability might be advantageous for the virus to resist environmental degradation until it infects a susceptible host. When VP4 is cleaved in the lumen of the host's gastrointestinal tract, the virus particle would become less stable but more infectious. To test this hypothesis, a series of experiments was undertaken to analyse the cleavage state of VP4 on virus shed by an infected host into the environment. Immunoblots of intestinal wash solutions derived from infant and adult BALB/c mice infected with a virulent cell culture-adapted variant of the EDIM virus (EW) or wild-type murine rotavirus EDIM-Cambridge were analysed. Virtually all of the VP4 in these samples was in the cleaved form. Moreover, cell culture titration of trypsin-treated and untreated intestinal contents from pups infected with EW indicated that excreted virus is fully activated prior to trypsin addition. It was also observed that trypsin-activated virus has no disadvantage in initiating infection in naive animals over virions containing an intact VP4. These studies indicate that VP4 is cleaved upon release from the intestinal cell and that virus shed into the environment does not have an intact VP4.

Analyses of homologous rotavirus infection in the mouse model.

The group A rotaviruses are significant human and veterinary pathogens in terms of morbidity, mortality, and economic loss. Despite its importance, an effective vaccine remains elusive due at least in part to our incomplete understanding of rotavirus immunity and protection. Both large and small animal model systems have been established to address these issues. One significant drawback of these models is the lack of well-characterized wild-type homologous viruses and their cell culture-adapted variants. We have characterized four strains of murine rotaviruses, EC, EHP, EL, and EW, in the infant and adult mouse model using wild-type isolates and cell culture-adapted variants of each strain. Wild-type murine rotaviruses appear to be equally infectious in infant and adult mice in terms of the intensity and duration of virus shedding following primary infection. Spread of infection to naive cagemates is seen in both age groups. Clearance of shedding following primary infection appears to correlate with the development of virus-specific intestinal IgA. Protective immunity is developed in both infant and adult mice following oral infection as demonstrated by a lack of shedding after subsequent wild-type virus challenge. Cell culture-adapted murine rotaviruses appear to be highly attenuated when administered to naive animals and do not spread efficiently to nonimmune cagemates. The availability of these wild-type and cell culture-adapted virus preparations should allow a more systematic evaluation of rotavirus infection and immunity. Furthermore, future vaccine strategies can be evaluated in the mouse model using several fully virulent homologous viruses for challenge.