  T-cell activation plays a critical role in the initiation and propagation of
HIV-1 infection and yet transient activation of the immune system is a normal
response to immunization. In this study we extend a simple of model of HIV
infection to include T cell activation by vaccination. We then show that the
model can reproduce many but not all of the features of the post-tetanus
immunization rise in viral load observed and reported on by Stanley et al., [N.
Engl. J. Med., 334:1222--1230 (1996)]. Amplitudes and approximate timing of
post-immunization maximum viremia were matched in nine of twelve cases; in
patients with double peaks of nearly equal amplitude the later peaks were
matched. Patients with single early peaks in their viremia were best fit with
relatively high antigen clearance rate constants, while patients with early and
late peaks in viremia of equal or nearly equal amplitude were best-fit with
much lower clearance rates. The rate of clearance may depend on the level of
pre-existing antibody, which in turn would be expected to depend on the time
since the individual under study received a previous tetanus vaccination.
