Immune Responses against Conserved and Variable Viral Epitopes

Abstract

We extend well-known mathematical models of viral infection to examine the response of cytotoxic T lymphocytes (CTL) to both conserved and variable viral epitopes. Because most viruses are subject to error-prone reproduction, CTL recognition may be faced with highly variable epitopes, while other CTL epitopes may remain conserved across viral strains. In this paper we examine the steady state conditions for a simple model of viral-immune system dynamics in which the viral strain can be limited by either a specific immune response, a cross-reactive immune response, or host cell availability. We find that the most important factors determining the type of immune response elicited and viral diversity are the relative proliferation rates of the two types of immune response. If the immune response to variable epitopes is strong compared with the response to conserved epitopes, diversity will be negatively correlated with the total burden of infected cells. In this situation high diversity may be indicative of a strong immune response and slower disease progression. In contrast, for patients whose immune response is directed predominantly towards conserved viral epitopes, our model predicts that diversity and viral load will be positively correlated.