Effect of didanosine, stavudine, and hydroxyurea therapy on apoptosis in CD45RA+ and CD45RO+ T lymphocyte subpopulations

Activity, safety, and immunological effects of hydroxyurea added to didanosine in antiretroviral-naive and experienced HIV type 1-infected subjects: a randomized, placebo-controlled trial, ACTG 307

We performed a 24-week, placebo-controlled, comparative trial of hydroxyurea (HU) monotherapy, didanosine(ddI) monotherapy, and the combination of ddI plus HU administered as 1000 mg qd or 1500 mg qd in antiretroviral-naive and experienced subjects with CD4+ lymphocyte counts of 200-700 cells/mm3. Enrollment included 134 subjects. HU enhanced the antiviral activity of ddI by 1.0 log10 copies/ml after 8 weeks of therapy, with sustained responses over 24 weeks. HU alone over 4 weeks had no effect. Lamivudine resistance had little impact on antiretroviral activity when examined across treatment arms. Increases in absolute CD4+ T cell counts, but not CD4+ T cell percentages, were less in subjects who received HU compared to ddI monotherapy, and lymphoproliferative responses to antigenic and mitogenic stimuli were not altered. Subjects who received HU 1500 mg were more likely to experience dose-limiting hematological toxicities compared to those who received 1000 mg, without any additional antiviral benefit. HU may continue to have a role as a component of HIV therapy.

Differences in cellular activation and apoptosis in HIV-infected patients receiving protease inhibitors or nonnucleoside reverse transcriptase inhibitors

The mechanism of CD4(+) T cell depletion seen in HIV infection is largely mediated by increased apoptosis of these cells. The benefit of protease inhibitor (PI)-based antiretroviral therapy to CD4(+) T cell recovery seems to involve more than its antiviral activity, and a direct antiapoptotic effect of PIs has been proposed to explain it. To test this hypothesis we have analyzed directly, ex vivo, the effects of two different highly active antiretroviral therapy (HAART) regimens on the levels of activation and apoptosis of T lymphocytes. A total of 126 subjects (43 receiving PIs, 35 receiving NNRTIs, 27 untreated HIV carriers, and 21 uninfected control subjects) was included in the study. Apoptosis was measured in blood lymphocytes by flow cytometry, using annexin V labeling. A broad panel of monoclonal antibodies was used to characterize the different CD4(+) and CD8(+) lymphocyte subsets. Apoptosis was significantly increased in HIV-untreated subjects, whereas apoptosis levels did not differ when comparing HIV-positive subjects undergoing HAART and uninfected control subjects. Likewise, markers of activation were elevated in HIV-positive untreated patients, and declined in subjects receiving treatment. However, activated-memory CD8(+) T cells remained significantly higher in treated patients with respect to uninfected control subjects. No differences in the level of apoptosis or in immune activation markers were recognized when comparing subjects receiving PIs and those receiving NNRTIs. Antiretroviral therapy reduces apoptosis of CD4(+) and CD8(+) lymphocytes to normal levels without differences when comparing subjects receiving PI and NNRTI triple combinations. Despite complete suppression of viral replication, activated memory CD8(+) T cells remain significantly elevated in subjects receiving HAART, suggesting the persistence of residual HIV replication. If PIs provide a positive effect on CD4(+) counts beyond an antiviral effect, mechanisms other than apoptosis should be involved.

Entrapment of recent thymic emigrants in lymphoid tissues from HIV-infected patients: association with HIV cellular viral load

OBJECTIVE(S)

Depletion of thymus derived naive T-cells is a feature of HIV infection. Here the impact of HIV infection on the compartmentalization of recent thymic emigrants of (RTE) and naive T-cells was examined.

METHODS

Peripheral blood mononuclear cells (PBMC) and lymphoid tissue (LT) from 43 HIV-infected patients and 12 controls were examined for RTE distribution by measuring coding joint T-cell receptor excisional circles (cjTREC) by PCR and naive and memory T-cell subsets and adhesion molecules (L-selection, LFA-1) by flow cytometry.

RESULTS

In HIV-infected patients, the RTE as quantified by cjTRECs in CD4 LT cells were significantly higher than in PBMC. Their values, however, were less than in control subjects, in both the LT and PBMC compartments. This was associated with an increase in L-selectin and LFA-1 expression on LT derived T cells. In PBMC, a significant positive relationship between TREC and naive CD4 cells and an inverse relationship between TREC and cellular viral load (CVL) was observed. Whereas in LT, there was a positive relationship between cjTREC and both naive CD4 cell percentage and CVL.

CONCLUSIONS

Collectively, the data suggests that LT is a significant reservoir for RTE. The RTE appeared to be entrapped in LT from HIV-infected subjects. Such entrapment is probably a response to the high viral load in these tissues. These observations may partially explain the decline in RTE observed in the peripheral blood of HIV-infected patients, and the delay in recovery of naive cells in blood after initiation of HAART.

Long-term safety and antiretroviral activity of hydroxyurea and didanosine in HIV-infected patients

Long-term safety, immunologic effects, and antiretroviral activity of hydroxyurea and didanosine were evaluated in this retrospective study. Some 65 HIV-1-infected patients (39 of whom were antiretroviral naive) were studied (mean baseline CD4 count, 362 cells/mm3; mean plasma HIV-1 RNA viral load, 4.8 log10 copies/ml). The mean treatment duration was 20 months. Overall tolerance was good: 15 patients interrupted treatment because of clinical or biologic side effects. Four patients experienced a category B event. Patients had a mean increase of 27 CD4 cell counts after 12 months, of 112 after 24 months and of 59 after 36 months. They had a mean 1. 03 log10 fall in HIV-1 RNA after 12 months, 1.59 log10 after 24 months, and 1.27 log10 after 36 months. After 12 months, 35% developed an HIV-1 RNA viral load <200 copies/ml, 53% after 24 months, and 36% after 36 months. Those whose viral load became undetectable after 12 months have significantly lower baseline RNA values (p =.03). Fourteen patients had a viral load <3.4 log10 copies/ml after 24 months of the double therapy. A prolonged viral load suppression can be achieved using a simple combination of two drugs that are inexpensive and well tolerated.

Long-term hydroxyurea in combination with didanosine and stavudine for the treatment of HIV-1 infection. Swiss HIV Cohort Study

OBJECTIVE AND METHODS

In 1998 we reported on a randomized comparison between stavudine plus didanosine plus placebo versus stavudine plus didanosine plus hydroxyurea (HU), in patients with a CD4 count of 200-500 x 10(6) cells/l. After 3 months, the HU group had a higher proportion of patients with viral load < 200 x 10 cells/l. At the end of the 3 months blinded period, patients in the placebo group had the option to add HU if their viral load remained > 200 x 10(6) cells/l. We report results after 24 months.

RESULTS

Seventy-two patients were randomized to the HU arm, and a further 30 elected to add HU after 12 weeks. Twenty-four months after the start of the trial, only 25% of the 72 patients originally randomized to HU, and 20% of the 30 who added HU after week 12, were still taking it. The reasons for stopping HU were: lack of efficacy (45%), adverse events (37%) and patient or physician preference (18%). Side effects were more frequent in the didanosine/stavudine/HU group than in the didanosine/stavudine group: neuropathy (35 versus 15%, P< 0.02), fatigue (22 versus 7%, P< 0.01), and nausea or vomiting (26 versus 9%, P< 0.01). Of those who had discontinued HU, 73% were taking three drugs including a protease inhibitor. Patients who had started HU were compared with similar patients who had started protease inhibitors in the Swiss cohort. The probability of stopping HU was higher than the probability of stopping nelfinavir or indinavir, and similar to the probability of stopping ritonavir.

CONCLUSION

HU increased the antiviral effect of stavudine plus didanosine. However, side effects were more frequent, and after 24 months the majority of patients had switched to protease inhibitor regimens.

Effects of therapy with highly active anti-retroviral therapy (HAART) and IL-2 on CD4+ and CD8+ lymphocyte apoptosis in HIV+ patients

The kinetics and effects of in vivo spontaneous apoptosis and activation-induced cell death (AICD) upon CD4+ and CD8+ lymphocyte subsets and CD4 naive cell numbers were studied in HIV+ subjects with CD4 pretreatment values > 200/mm3, who were subsequently treated for 48 weeks with HAART alone or in combination with six cycles of subcutaneous IL-2. Irrespective of the type of treatment, patients showed a statistically significant increase in CD4 cell counts after 4 weeks, although the CD4 naive subset only increased significantly in the IL-2-treated subjects at the end of treatment. The percentage of CD4 cells undergoing spontaneous apoptosis and AICD was significantly reduced in all patients after 4 weeks and this reduction was maintained until the end of therapy; however, the level always remained significantly higher in comparison with healthy subjects. A statistically significant reduction in CD8 apoptosis levels required at least 24 weeks of therapy. Together these data suggest that a reduction in the level of apoptosis may contribute to the early rise in CD4 numbers measured after HAART, but that later on HAART is unable to improve further this biological parameter. Although the use of IL-2 had no additional effects on spontaneous apoptosis and AICD, it may be beneficial by stimulating a late increase in the numbers of CD4 naive cells in HIV-treated subjects.