The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings have not been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of the NTP or the U.S. Government.
Nevirapine (NVP), which is marketed under the brand name Viramune, belongs to a class of drugs known as non-nucleoside reverse transcriptase inhibitors and is used for the treatment of acquired immune deficiency syndrome and human immunodeficiency virus). Because HIV can infect immune cells, i.e., CD4+ T cells, it is important to establish if drugs designed to treat the infection can impact the various functions of immune system. Drug hypersensitivity has been demonstrated in mice following NVP treatment using the lymph node proliferation assay (Weaver et al., 2005) and has been reported in HIV-positive humans having CD4+ cell counts greater than 250 cells per microliter (Wit et al., 2008). Furthermore, cases of Stevens-Johnson syndrome and toxic epidermal necrolysis, which are two rare immune-mediated cutaneous adverse reactions, have been linked to NVP treatment (Barvaliya et al., 2011).
Studies evaluating the effects of NVP in adult female B6C3F1 mice, conducted on behalf of the National Toxicology Program, have demonstrated that NVP exposure for 28 days suppressed humoral immunity (antibody-forming cell response) while innate immunity was enhanced (natural killer cell activity). Therefore, the NTP requested that a study be conducted to evaluate the effects of perinatal NVP exposure on the immune system. These developmental immunotoxicology studies were conducted in female B6C3F1 mice. Based on the half-life of the compound and the pattern of use in humans, C57BL/6 dams were exposed to NVP twice daily by oral gavage (for a total daily dose of 88, 176, or 266 mg/kg/day), beginning at the conclusion of a 5-day mating period with C3H males. The first day of the mating period was designated as gestational day 0 and the first day of NVP treatment was GD5. The day of birth for each individual litter was designated as litter PND1. Dams continued to receive NVP treatment until the B6C3F1 offspring were weaned on litter post-natal day 21. The B6C3F1 offspring were exposed via lactation and treated with a single dose of NVP by oral gavage from litter PND4 to litter PND21. On litter PND21, male offspring were removed from the study and female mice were weaned. From litter PND22 until the day of study termination (between approximately PND45 and PND55), the female B6C3F1 offspring were treated twice daily with NVP by oral gavage. NVP dosing formulations were prepared weekly in the vehicle 0.2% methylcellulose with 0.1% Tween 80. The in-life phase of these studies was carried out between 28 May 2003 and 11 August 2003. No usable sheep red blood cell (sRBC) high-salt release membrane antigen was available to evaluate serum IgM anti-sRBC antibody levels. No other significant protocol or standard operating procedure deviations occurred during the study that affected the quality of the data and the ability to interpret the data with respect to the developmental immunotoxicity of NVP.
In each of the four studies conducted, there were no significant differences in the terminal body weights of NVP-exposed mice and those of the vehicle control group, with the exception of a 7% decrease at the 88 mg/kg/day dose in one study. When combined terminal body weights were evaluated, significant decreases were observed at all doses of NVP. The decreases were each 4% when compared to the vehicle control group, and a dose-related trend was observed. Absolute liver weights were significantly increased following developmental exposure to NVP at doses ≥ 176 mg/kg/day in two of three studies, while relative liver weights were significantly increased at doses ≥ 88 mg/kg/day in two studies and at doses ≥ 176 mg/kg/day in the third study. Overall, the weights of the two major immune organs, the spleen and thymus, were unaffected by NVP exposure. With the exception of a few sporadic increases, hematological parameters were unaffected, and no effects were observed on the various leukocyte differentials. Spleen cell numbers were decreased in mice exposed to ≥ 176 mg/kg/day NVP. Absolute values of splenic B cells, T cells, T-helper cells, T-cytotoxic cells, NK cells, and macrophages were all decreased at doses ≥ 176 mg/kg. In addition, TH cells were decreased at the 88 mg/kg/day dose level. Humoral immunity, as assessed using the AFC assay, was significantly suppressed in a dose-related manner at all NVP exposure levels. In contrast, the mixed leukocyte response and anti-CD3 mediated spleen cell proliferation, which are measures of cell-mediated immunity, were unaffected. NK cell activity, a measure of innate immune function, was significantly increased as compared to the vehicle control group.
In conclusion, developmental exposure to NVP resulted in suppression of the humoral immune response (AFC response) and an enhancement of NK cell activity (innate immunity) at doses ≥ 88 mg/kg/day in female B6C3F1 mice.
Weaver J.L., Chapdelaine J.M., Descotes J., Germolec D., Holsapple M., House R., Lebrec H., Meade J., Pieters R., Hastings K.L., & Dean J.H. (2005). Evaluation of a lymph node proliferation assay for its ability to detect pharmaceuticals with potential to cause immune-mediated drug reactions. J Immunotoxicol 2:11-20.
Wit F.W., Kesselring A.M., Gras L., Richter C., van der Ende M.E., Brinkman K., Lange J.M., de Wolf F., & Reiss P. (2008). Discontinuation of nevirapine because of hypersensitivity reactions in patients with prior treatment experience, compared with treatment-naïve patients: the ATHENA cohort study. Clin Infect Dis 46(6):933-40.
Barvaliya M., Sanmukhani J., Patel T., Paliwal N., Shah H., & Tripathi C. (2011). Drug-induced Stevens-Johnson syndrome, toxic epidermal necrolysis, and SJS-TEN overlap: A multicentric retrospective study. J Postgrad Med 57(2):115-9.