No abstract

The expression of endogenous retrotransposable elements including Long Interspersed Nuclear Element-1 (LINE-1 or L1) and Human Endogenous Retrovirus (HERV)-K accompanies neoplastic transformation and infection with viruses such as HIV. The ability to engender immunity safely against such self-antigens would facilitate the development of novel vaccines and immunotherapies. Here we address the safety and immunogenicity of vaccination with these elements. We employed immunohistochemical analysis and literature-precedent to identify potential off-target tissues in humans and establish their translatability in preclinical species to guide safety assessments. Immunization of mice with murine L1 Open Reading Frame-2 (L1O2) induced strong CD8 T cell responses without detectable tissue damage. Similarly, immunization of rhesus macaques with human L1O2 (96% identity with macaque), and Simian ERV (SERV)-K Gag and Env induced polyfunctional T cell responses to all antigens, and antibody responses to SERV-K Env. There were no adverse safety or pathology findings related to vaccination. These studies provide the first evidence that immune responses can be induced safely against this class of self antigens, and pave the way for their investigation as HIV- or tumor-associated targets.

Nevirapine treatment can cause a skin rash. We developed an animal model of this rash and determined that the 12-hydroxylation metabolic pathway is responsible for the rash, and treatment of animals with 12-OH-nevirapine also leads to a rash. In the present study, we investigated the specificity of lymphocytes in nevirapine-induced skin rash. Brown Norway rats were treated with nevirapine or 12-OH-nevirapine to induce a rash. Lymph nodes were removed, and the response of lymphocytes to nevirapine and its metabolites/analogs was determined by cytokine production (enzyme-linked immunosorbent assay, enzyme-linked immunosorbent spot assay, and Luminex) and proliferation (alamar blue assay). Subsets of lymphocytes were depleted to determine which cells were responsible for cytokine production. Lymphocytes from animals rechallenged with nevirapine proliferated to nevirapine, but not to 12-OH-nevirapine or 4-chloro-nevirapine. They also produced interferon-␥ (IFN-␥) when exposed to nevirapine, significantly less when exposed to 4-chloro-nevirapine, and very little when exposed to 12-OHnevirapine, even though oxidation to 12-OH-nevirapine is required to induce the rash. Moreover, the specificity of lymphocytes from 12-OH-nevirapine-treated rats was the same, i.e., responding to nevirapine more than to 12-OH-nevirapine, even though these animals had never been exposed to nevirapine. A Luminex immunoassay showed that a variety of other cytokines/chemokines were also produced by nevirapine-stimulated lymphocytes. CD4 ϩ cells were the major source of IFN-␥. The specificity of lymphocytes in activation assays cannot be used to determine what initiated an immune response. This has significant implications for understanding the evolution of an immune response and the basis of the pharmacological interaction hypothesis.Nevirapine (NVP), marketed under the trade name Viramune (Boehringer Ingelheim GmbH, Ingelheim, Germany), is a non-nucleoside reverse transcriptase inhibitor used in the treatment of human immunodeficiency virus infections. Although effective, its use has been limited because of its propensity to cause skin rash and liver toxicity. In patients, skin rashes vary from mild erythematous, maculopapular rashes to more severe Stevens-Johnson syndrome or toxic epidermal necrolysis (Warren et al., 1998;Fagot et al., 2001). Our group discovered a novel animal model of NVPinduced skin rash in rats. The characteristics of NVP-induced skin rash in Brown Norway rats are very similar to the milder rashes that occur in humans, which suggests that the mechanisms are very similar. Specifically, in both humans and rats there is a 2-to 3-week delay between starting the drug and the onset of rash, and on re-exposure, symptoms are more severe and accelerated (Shenton et al., 2003;Taiwo, 2006). Females are more susceptible to developing rash than males in both Brown Norway rats and humans. Furthermore, the sensitivity to NVP-induced skin rash can be transferred with CD4 ϩ T cells from NVP-rechallenged rats to naive recipients ...

Treatment of HIV-1 infections with nevirapine is associated with skin and liver toxicity. These two organ toxicities range from mild to severe, in rare cases resulting in life-threatening liver failure or toxic epidermal necrolysis. The study of the mechanistic steps leading to nevirapine-induced skin rash has been facilitated by the discovery of an animal model in which nevirapine causes a skin rash in rats that closely mimics the rash reported in patients. The similarity in characteristics of the rash between humans and rats strongly suggests that the basic mechanism is the same in both. The rash is clearly immune-mediated in rats, and partial depletion of CD4(+) T cells, but not CD8(+) T cells, is protective. We have demonstrated that the rash is related to the 12-hydroxylation of nevirapine rather than to the parent drug. This is presumably because the 12-hydroxy metabolite can be converted to a reactive quinone methide in skin, but that remains to be demonstrated. Although the rash is clearly related to the 12-hydroxy metabolite rather than the parent drug, cells from rechallenged animals respond ex vivo to the parent drug by producing cytokines such as interferon-gamma with little response to the 12-hydroxy metabolite, even when the rash was induced by treatment with the metabolite rather than the parent drug. This indicates that the response of T cells in vitro cannot be used to determine what caused an immune response. We are now studying the detailed steps by which the 12-hydroxy metabolite induces an immune response and skin rash. This animal model provides a unique tool to study the mechanistic details of an idiosyncratic drug reaction; however, it is likely that there are significant differences in the mechanisms of different idiosyncratic drug reactions, and therefore the results of these studies cannot safely be generalized to all idiosyncratic drug reactions.