Joseph B. Margolick

Latent infection of CD4 + T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective combination therapy

Combination therapy for HIV-1 infection can reduce plasma virus to undetectable levels, indicating that prolonged treatment might eradicate the infection. However, HIV-1 can persist in a latent form in resting CD4+ T cells. We measured the decay rate of this latent reservoir in 34 treated adults whose plasma virus levels were undetectable. The mean half-life of the latent reservoir was very long (43.9 months). If the latent reservoir consists of only 1 × 105 cells, eradication could take as long as 60 years. Thus, latent infection of resting CD4+ T cells provides a mechanism for lifelong persistence of HIV-1, even in patients on effective anti-retroviral therapy.

Long-term follow-up studies confirm the stability of the latent reservoir for HIV-1 in resting CD4 + T cells

Latent HIV-1 persists in resting memory CD4+ T cells, even in patients receiving highly active antiretroviral therapy (HAART). It has been unclear how stable this latent reservoir is and whether its persistence reflects replenishment by low-level viremia. Here we show that even in treated patients who have had no detectable viremia for as long as 7 years, the reservoir decays so slowly (t1/2 = 44 months) that eradication is unlikely.

Stimulation of HIV-1-Specific Cytolytic T Lymphocytes Facilitates Elimination of Latent Viral Reservoir after Virus Reactivation

Highly active antiretroviral therapy (HAART) suppresses HIV-1 replication but cannot eliminate the virus because HIV-1 establishes latent infection. Interruption of HAART leads to a rapid rebound of viremia, so life-long treatment is required. Efforts to purge the latent reservoir have focused on reactivating latent proviruses without inducing global T cell activation. However, the killing of the infected cells after virus reactivation, which is essential for elimination of the reservoir, has not been assessed. Here we show that after reversal of latency in an in vitro model, infected resting CD4(+) T cells survived despite viral cytopathic effects, even in the presence of autologous cytolytic T lymphocytes (CTLs) from most patients on HAART. Antigen-specific stimulation of patient CTLs led to efficient killing of infected cells. These results demonstrate that stimulating HIV-1-specific CTLs prior to reactivating latent HIV-1 may be essential for successful eradication efforts and should be considered in future clinical trials.

Activation of the PTEN/mTOR/STAT3 pathway in breast cancer stem-like cells is required for viability and maintenance

Side-population (SP) cells within cancers and cell lines are rare cell populations known to enrich cancer stem-like cells. In this study, we characterized SP cells from the human breast cancer cell line MCF7 as a model for cancer stem-like cells. Compared with non-SP cells, MCF7 SP cells had higher colony-formation ability in vitro and greater tumorigenicity in vivo, suggesting that MCF7 SP cells enrich cancer stem-like cells. cDNA microarray analysis of the SP cells indicated higher expression of ATP-binding cassette transporters and genes involved in quiescence, which were confirmed by quantitative RT-PCR and flow cytometry cell cycle analysis. To identify signal pathways important for cancer stem-like cells, we analyzed cDNA microarray data and identified nine pathways that were altered in the SP cells. To analyze the protein signaling networks, we used reverse-phase signaling pathway protein microarray technology and identified three signaling proteins that are significantly different between MCF7 SP and non-SP cells. Notably, signaling of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR), signal transduction and activator of transcription (STAT3), and phosphatase and tensin homolog (PTEN) was confirmed to be critical for MCF7 SP cell survival and proliferation by pathway specific inhibitors, selected gene knockdown, and in vivo tumorigenicity assay. The STAT3 pathway was found to be positively regulated by mTOR signaling, whereas PTEN served as a negative regulator of both STAT3 and mTOR signaling. This study suggests the existence of prosurvival signaling pathways critical for cancer stem-like cell maintenance, which could be selectively targeted for inhibiting cancer stem-like cells for improved treatment.

Improved coreceptor usage prediction and genotypic monitoring of R5-to-X4 transition by motif analysis of human immunodeficiency virus type 1 env V3 loop sequences.

ABSTRACT Early in infection, human immunodeficiency virus type 1 (HIV-1) generally uses the CCR5 chemokine receptor (along with CD4) for cellular entry. In many HIV-1-infected individuals, viral genotypic changes arise that allow the virus to use CXCR4 (either in addition to CCR5 or alone) as an entry coreceptor. This switch has been associated with an acceleration of both CD3+ T-cell decline and progression to AIDS. While it is well known that the V3 loop of gp120 largely determines coreceptor usage and that positively charged residues in V3 play an important role, the process of genetic change in V3 leading to altered coreceptor usage is not well understood. Further, the methods for biological phenotyping of virus for research or clinical purposes are laborious, depend on sample availability, and present biosafety concerns, so reliable methods for sequence-based“ virtual phenotyping” are desirable. We introduce a simple bioinformatic method of scoring V3 amino acid sequences that reliably predicts CXCR4 usage (sensitivity, 84%; specificity, 96%). This score (as determined on the basis of position-specific scoring matrices [PSSM]) can be interpreted as revealing a propensity to use CXCR4 as follows: known R5 viruses had low scores, R5X4 viruses had intermediate scores, and X4 viruses had high scores. Application of the PSSM scoring method to reconstructed virus phylogenies of 11 longitudinally sampled individuals revealed that the development of X4 viruses was generally gradual and involved the accumulation of multiple amino acid changes in V3. We found that X4 viruses were lost in two ways: by the dying off of an established X4 lineage or by mutation back to low-scoring V3 loops.

Sex differences in HIV-1 viral load and progression to AIDS

BACKGROUND Plasma HIV-1 RNA measurements are used for initiation of antiretroviral treatments. Whether the viral-load association with prognosis is similar in women and men is unknown. METHODS We studied 812 specimens from 650 injection-drug users (IDUs) participating in a continuous observational study of patients based in a community clinic. HIV-1 load was measured by branched-chain DNA on samples from 527 IDUs from the baseline visit, and by reverse-transcriptase PCR and quantitative microculture on samples from 285 IDUs at a follow-up visit 3 years later. FNDINGS: Women had lower median viral-load measurements than men by branched-chain DNA (3365 vs 8907 copies/mL; p=0.001), reverse-transcriptase PCR (45416 vs 93130 copies/mL; p=0.02), and quantitative microculture (5 vs 8 infectious units per million peripheral blood mononuclear cells; p=0.015). This association remained even after adjustment for CD4 cell count, race, and drug use within the previous 6 months. Time to AIDS was statistically similar for men and women in a univariate proportional-hazards model and in a model adjusting for CD4 cell count. Proportional-hazards models showed that women with the same viral load as men had a 1.6-fold higher risk of AIDS (95% CI 1.10-2.32); or, equivalently, that women with half the viral load of men had a similar time to AIDS as men. INTERPRETATION Although a biological mechanism remains unclear, these data suggest that current recommendations for HIV-1 viral-load thresholds to initiate antiretroviral therapy should be revised downwards for women.

Natural History of Human Immunodeficiency Virus Type 1 Viremia after Seroconversion and Proximal to AIDS in a Large Cohort of Homosexual Men

The natural history of human immunodeficiency virus type 1 (HIV-1) viremia and its association with clinical outcomes after seroconversion was characterized in a cohort of homosexual men. HIV-1 RNA was measured by reverse-transcription polymerase chain reaction (RT-PCR) in stored longitudinal plasma samples from 269 seroconverters. Subjects were generally antiretroviral drug naive for the first 3 years after seroconversion. The decline in CD4 lymphocyte counts was strongly associated with initial HIV RNA measurements. Both initial HIV RNA levels and slopes were associated with AIDS-free times. Median slopes were +0.18, +0.09, and -0.01 log10 copies/mL, respectively, for subjects developing AIDS <3, 3-7, and>7 years after seroconversion. In contrast, HIV RNA slopes in the 3 years preceding AIDS and HIV RNA levels at AIDS diagnosis showed little variation according to total AIDS-free time. HIV RNA load at the first HIV-seropositive visit ( approximately 3 months after seroconversion) was highly predictive of AIDS, and subsequent HIV RNA measurements showed even better prognostic discrimination.

Initial Plasma HIV-1 RNA Levels and Progression to AIDS in Women and Men

BACKGROUND It is unclear whether there are differences between men and women with human immunodeficiency virus type 1 (HIV-1) infection in the plasma level of viral RNA (the viral load). In men, the initial viral load after seroconversion predicts the likelihood of progression to the acquired immunodeficiency syndrome (AIDS), but the relation between the two has not been assessed in women. Currently, the guidelines for initiating antiretroviral therapy are applied uniformly to women and men. METHODS From 1988 through 1998, the viral load and the CD4+ lymphocyte count were measured approximately every six months in 156 male and 46 female injection-drug users who were followed prospectively after HIV-1 seroconversion. RESULTS The median initial viral load was 50,766 copies of HIV-1 RNA per milliliter in the men but only 15,103 copies per milliliter in the women (P<0.001). The median initial CD4+ count did not differ significantly according to sex (659 and 672 cells per cubic millimeter, respectively). HIV-1 infection progressed to AIDS in 29 men and 15 women, and the risk of progression did not differ significantly according to sex. For each increase of 1 log in the viral load (on a base 10 scale), the hazard ratio for progression to AIDS was 1.55 (95 percent confidence interval, 0.97 to 2.47) among the men and 1.43 (95 percent confidence interval, 0.76 to 2.69) among the women. The median initial viral load was 77,822 HIV-1 RNA copies per milliliter in the men in whom AIDS developed and 40,634 copies per milliliter in the men in whom it did not; the corresponding values in the women were 17,149 and 12,043 copies per milliliter. Given the recommendation that treatment should be initiated when the viral load reaches 20,000 copies per milliliter, 74 percent of the men but only 37 percent of the women in our study would have been eligible for therapy at the first visit after seroconversion (P<0.001). CONCLUSIONS Although the initial level of HIV-1 RNA was lower in women than in men, the rates of progression to AIDS were similar. Treatment guidelines that are based on the viral load, rather than the CD4+ lymphocyte count, will lead to differences in eligibility for antiretroviral treatment according to sex.

Association between highly active antiretroviral therapy and hypertension in a large cohort of men followed from 1984 to 2003

Objective:To examine the impact of HIV infection and highly active antiretroviral therapy on systolic and diastolic hypertension. Design:Cohort study with semi-annual assessment of the outcome. Methods:We studied 5578 participants of the Multicenter AIDS Cohort Study with blood pressure measurements obtained between 1984 and 2003. The primary outcomes were systolic hypertension (SH; systolic blood pressure > 140 mmHg) and diastolic hypertension (DH; diastolic blood pressure > 90 mmHg). Statistical analyses were performed using multiple logistic regression with robust variance estimation. Results:Of the 84 813 person-visits available for analysis, 7.3 and 8.0% showed SH and DH, respectively. Controlling for age, race, body mass index, and smoking, HIV positive men not taking antiretroviral therapy were significantly less likely than HIV negative men to have SH [odds ratio (OR), 0.79; 95% confidence interval (CI), 0.70–0.89], as were men taking mono/combination therapy (OR, 0.69; 95% CI, 0.59–0.80). The prevalence of SH among men taking highly active antiretroviral therapy (HAART) for less than 2 years was similar to that among HIV negative men (OR, 1.06; 95% CI, 0.87–1.30), but was significantly higher thereafter; for 2 to 5 years of HAART (OR, 1.51; 95% CI, 1.25–1.82) and for more than 5 years of HAART (OR, 1.70; 95% CI, 1.34–2.16). In contrast, DH was not significantly higher among men with prolonged HAART use compared to that among HIV negative controls. Conclusions:Prolonged HAART use was significantly associated with a higher prevalence of SH. This finding suggests that individuals taking HAART may be at increased risk of developing hypertension-related conditions and underscores the importance of blood pressure monitoring among these individuals.

Resting CD4+ T Cells from Human Immunodeficiency Virus Type 1 (HIV-1)-Infected Individuals Carry Integrated HIV-1 Genomes within Actively Transcribed Host Genes

ABSTRACT Resting CD4+ T-cell populations from human immunodeficiency virus type 1 (HIV-1)-infected individuals include cells with integrated HIV-1 DNA. In individuals showing suppression of viremia during highly active antiretroviral therapy (HAART), resting CD4+ T-cell populations do not produce virus without cellular activation. To determine whether the nonproductive nature of the infection in resting CD4+ T cells is due to retroviral integration into chromosomal regions that are repressive for transcription, we used inverse PCR to characterize the HIV-1 integration sites in vivo in resting CD4+ T cells from patients on HAART. Of 74 integration sites from 16 patients, 93% resided within transcription units, usually within introns. Integration was random with respect to transcriptional orientation relative to the host gene and with respect to position within the host gene. Of integration sites within well-characterized genes, 91% (51 of 56) were in genes that were actively expressed in resting CD4+ T cells, as directly demonstrated by reverse transcriptase PCR (RT-PCR). These results predict that HIV-1 sequences may be included in the primary transcripts of host genes as part of rapidly degraded introns. RT-PCR experiments confirmed the presence of HIV-1 sequences within transcripts initiating upstream of the HIV-1 transcription start site. Taken together, these results demonstrate that HIV-1 genomes reside within actively transcribed host genes in resting CD4+ T cells in vivo.