A Study of the Specificity of Lymphocytes in Nevirapine-Induced Skin Rash

Abstract

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 ...

Idiosyncratic Drug Reactions and the Potential Role of Metabolism

“…It is also possible that an immune response is initiated elsewhere in the body, and the skin becomes a bystander because of its high immunosurveillance activity. This is consistent with the observation that a reactive metabolite may be responsible for initiating an immune response, but then the immune response spreads so that lymphocytes recognize the parent drug [157]. Although drugs can cause other types of rashes, such as fixed drug eruptions, the discussion is limited to urticaria, maculopapular rashes, and Stevens-Johnson syndrome/TEN.…”

Idiosyncratic Adverse Drug Reactions: Current Concepts

“…The unstated assumption upon which the P-I hypothesis is based is that what T cells from patients with a history of an IDR respond to is what initially induced the immune response. However, in the nevirapine model, T cells from affected animals responded better to nevirapine than they did to the benzylic alcohol metabolite, although we can be sure that it was the sulfate of the benzylic alcohol that induced the skin rash (Chen et al, 2009). Thus it appears that once an immune response is initiated by a reactive metabolite, the immune response can spread to recognize the parent drug.…”

“…In addition, the rash in rats is dependent on CD4+ T cells in the rat, and patients with a low CD4 T-cell count have a lower incidence of rash. Furthermore, incubation of lymphocytes from affected patients or rats produce IFN-g (Keane et al, 2007;Chen et al, 2009). Although the rash can be induced in other strains of rats, the incidence is much lower, and it can only be induced in male rats by using a cotreatment with aminobenzotriazole.…”

“…Throughout this discussion, readers must be aware that, as yet, it is difficult to define the contribution of hapten/pharmacological pathways of T-cell activation in patients, and indeed whether the noncovalently bound parent drug mimics the action of hapten-peptide conjugates by surmounting the binding energy needed for T-cell activation in an in vitro model. In this respect, Chen et al (2009) have shown in an animal model that once an immune response is induced by a reactive metabolite, the response can spread to recognize the parent drug (discussed in detail in Section IV.A).…”

Idiosyncratic Drug Reactions

“…Since sulfotransferases are known to occur in skin, this provides a plausible explanation for the development of nevirapine-induced skin rashes [16,180]. Studies on the specificity of lymphocytes in nevirapine-treated BN rats have demonstrated that reactive metabolites may be responsible for initiation of an immune response but in addition, the immune response may be extended in that lymphocytes may also become reactive to the parent drug [190].…”