To develop more detailed models of EBV persistence we have studied the dynamics of virus shedding in healthy carriers. We demonstrate that EBV shedding into saliva is continuous and rapid such that the virus level is replaced in ≤2 minutes, the average time that a normal individual swallows. Thus, the mouth is not a reservoir of virus but a conduit through which a continuous flow stream of virus passes in saliva. Consequently, virus is being shed at a much higher rate than previously thought, a level too high to be accounted for by replication in B cells in Waldeyer's ring alone. Virus shedding is relatively stable over short periods (hours-days) but varies through 3.5 to 5.5 logs over longer periods, a degree of variation that also cannot be accounted for solely by replication in B cells. This variation means, contrary to what is generally believed, that the definition of high and low shedder is not so much a function of variation between individuals but within individuals over time. The dynamics of shedding describe a process governing virus production that is occurring independently ≤3 times at any moment. This process grows exponentially and is then randomly terminated. We propose that these dynamics are best explained by a model where single B cells sporadically release virus that infects anywhere from 1 to 5 epithelial cells. This infection spreads at a constant exponential rate and is terminated randomly, resulting in infected plaques of epithelial cells ranging in size from 1 to 105 cells. At any one time there are a very small number (≤3) of plaques. We suggest that the final size of these plaques is a function of the rate of infectious spread within the lymphoepithelium which may be governed by the structural complexity of the tissue but is ultimately limited by the immune response.

Memory B cells latently infected with Epstein-Barr virus (mB Lats)

Dengue virus immune protection is specific to the serotype encountered and is thought to persist throughout one’s lifetime. Many serotype cross-reactive memory B cells isolated from humans with previous dengue infection are specific for the nonstructural and the prM structural viral proteins, and they can enhance infection in vitro. However, plasmablasts circulating in enormous numbers during acute secondary infection have not been studied. In this study, we analyzed single plasmablasts from two patients by sorting the cells for Ig sequence analysis and for recombinant expression of Abs. In contrast to memory B cells, most plasmablast-derived Abs bound to the structural E protein of dengue, and protection experiments in mice revealed that virus serotypes encountered during past infections were neutralized more efficiently than were the serotypes of the current infection. Together with genetic analyses, we show evidence that plasmablasts in dengue patients are a polyclonal pool of activated E protein–specific memory B cells and that their specificity is not representative of the serum Abs secreted by long-lived plasma cells in the memory phase. These results contribute to the understanding of the phenomenon of original antigenic sin in dengue.

Epstein-Barr virus (EBV) is an important human pathogen that establishes a lifelong persistent infection and for which no precise animal model exists. In this paper we describe in detail an agentbased model and computer simulation of EBV infection. Agents representing EBV and sets of B and T lymphocytes move and interact on a three-dimensional grid approximating Waldeyer's ring, together with abstract compartments for lymph and blood. The simulation allows us to explore the development and resolution of virtual infections in a manner not possible in actual human experiments. Specifically, we identify parameters capable of inducing clearance, persistent infection, or death.