Depo-Provera does not alter disease progression in SIVmac-infected female Chinese rhesus macaques

Abstract

Depo-Provera (medroxyprogesterone acetate), a long-acting derivative of progesterone, is utilized during many nonhuman primate microbicide studies to facilitate simian immunodeficiency virus (SIV) infection by thinning the vaginal epithelium. To date, the systemic effects of this steroid hormone in regard to SIV/HIV pathogenesis are not well understood, but an increase in infection rates and lymphoproliferation following progesterone application has been reported. Therefore, a proactive study using 20 Chinese rhesus macaques was designed to investigate the effect of a single Depo-Provera injection on SIV disease progression. Group 1 (n = 10) was treated with 30 mg Depo-Provera intramuscularly 30 days prior to intravenous challenge with 50 TCID(50) SIVmac251, while Group 2 (n = 10) remained untreated, but received the same amount of SIV. Blood samples were taken at predetermined intervals to measure RNA viral loads, CD4(+), CD8(+), and CD20(+) lymphocyte counts and percentages and absolute numbers of naive and memory T lymphocytes. Upon statistical endpoint data analysis, none of the parameters measured were shown to be significantly different between the groups. One animal in the Depo-Provera-treated group and two macaques in the control group were euthanized prior to study end due to the development of clinical signs (in weeks 43 and 51, respectively). All other animals were euthanized between weeks 68 and 71 post-SIV infection. Histopathological evaluations revealed that 5 of 10 animals in each group had developed simian AIDS (SAIDS). In summary, this prospective study demonstrated that a single injection of 30 mg Depo-Provera did not have a significant influence on SIV disease progression.

FIG. 1.

Viral loads were determined with TaqMan RT-PCR as described in the Materials and Methods section. (A) The thick black line represents the mean RNA viral load of the Depo-Provera-treated macaques after SIV infection. (B) The thick gray line shows the mean RNA viral load of the control group macaques after SIV infection. The dashed lines represent RNA viral loads of individual monkeys. There was no statistically significant difference between the two groups (p = 0.39, power 22%).

FIG. 2.

Mean and standard deviations of percentages and absolute CD3⁺CD4⁺ lymphocyte counts (A), CD3⁺CD8⁺ lymphocyte counts (B), and CD20⁺ lymphocyte counts are shown from week –6 to week 60 post-SIVmac251 infection. Absolute lymphocyte counts were determined with a VetScan HMT Hematology Analyzer, and the absolute numbers of lymphocyte populations were determined by the following equation: (Percent CD marker expression × absolute lymphocyte count)/100. There were no statistically significant differences between the groups [(A) p = 0.83, power = 14%; (B) p = 0.77, power = 17%; (C) p = 0.66, power = 26%]. The arrow indicates the day of SIV infection.

FIG. 3.

Mean and standard deviations of percentages and absolute CD4⁺CD95^– (naive) cells (A), CD4⁺CD95⁺ (memory) cells (B), CD8⁺CD95^– (naive) cells (C), and CD8⁺CD95⁺ (memory) cells (D) are shown from week –6 to week 64 post-SIVmac251 infection. Absolute lymphocyte counts were determined with a VetScan HMT Hematology Analyzer and the absolute numbers of lymphocyte populations were determined by the following equation: (Percent CD marker expression × absolute CD4 or CD8 lymphocyte count)/100. There were no statistically significant differences between the groups [(A) p = 0.65, power = 20%; (B) p = 0.89, power = 15%; (C) p = 0.47, power = 40%; (D) p = 0.52, power = 37%]. The arrow indicates the day of SIV infection.

FIG. 4.

AIDS-defining pathology in SIVmac251-infected Chinese rhesus macaques. Typical opportunistic and viral-associated lesions were observed in both experimental and control groups. (A) Lung, Pneumocystis carinii pneumonia (3826). (B) Lung, SIV giant cell pneumonia (3786). (C) Brain, SIV encephalitis (3786). (D) Small intestine, adenovirus enteritis (3779). (E) Gallbladder, Enterocytozoon bieneusi cholecystitis (3826). (F) Spleen, follicular lymphocytic hyperplasia with dysplasia (3781).

FIG. 5.

(A–D) Comparison of percentages and absolute CD4⁺ T lymphocytes and CD4⁺ T memory cells between animals diagnosed with SAIDS and nonprogressor animals. Mean and standard deviations are shown from week –6 to week 64 post-SIVmac251 infection. The arrow indicates the day of infection.