Provirus copy number to predict disease progression in asymptomatic human immunodeficiency virus type 1 infection

Circulating proviral HIV DNA and HIV-associated dementia

OBJECTIVE

Individuals continue to develop HIV-1-associated dementia (HAD) despite treatment with highly active antiretroviral therapy (HAART). Monocytes/macrophages (M/MPhi) can harbor proviral DNA that is not eradicated by HAART. To determine if HAD is associated with the level of HIV-1 infection within circulating leukocytes, we quantified HIV-1 DNA copy number in peripheral blood mononuclear cells (PBMC), and in PBMC subsets.

DESIGN

Cross-sectional analysis within the Hawaii Aging with HIV Cohort comparing participants with HAD to those with normal cognition (NC).

METHODS

Real-time PCR assays assessing HIV DNA copy number/1 x 10 cells were performed on PBMC and subsets.

RESULTS

Individuals with HAD (n = 27) had a median (interquartile range) of 9.11 (37.20) HIV DNA per 1 x 10 PBMC compared to 0.49 (0.89) HIV DNA per 1 x 10 PBMC in individuals with NC (n = 22). Using a univariate analysis in the subset of individuals with undetectable viral load (HAD, n = 11; NC, n = 13), the odds of HAD attributable to HIV DNA copy number was 2.76 (1.28-5.94), P < 0.01. Preliminary analysis of a small subset of patients (n = 5) suggested that the primary source of HIV DNA may be the activated M/MPhi (CD14/CD16) subset.

CONCLUSIONS

These findings suggest a potentially important association between circulating provirus and HAD.

The effects of interleukin-2 therapy on the viral reservoir in HIV+ patients

The initial idea that potent antiretroviral therapies could eradicate HIV infection within a few years of treatment has been recently challenged by the demonstration that the viral reservoir persists in the peripheral blood and in the lymphoid tissue. For this reason, an alternative approach based on the use of interleukin-2 has been developed. This cytokine, in fact, may be able to activate infected cells, promoting viral integration and replication, making HIV susceptible to antiretroviral treatments; this fact may ultimately contribute to the eradication of the virus itself. The measurement of the viral reservoir appears therefore essential to monitor the effects of combination therapies. We summarize here the technical approaches that have been used to quantitatively assess the HIV reservoir. We also show that the prolonged use of IL-2 in association with antiretroviral drugs promotes a reduction of the viral reservoir, but is unable to eradicate HIV, even after two years of therapy. The available in vitro and in vivo data do not exclude the fact that IL-2 may have a future in the treatment of HIV infection, though new therapeutic approaches using different strategies are required to clarify this issue.

Low plasma human immunodeficiency virus type 2 viral load is independent of proviral load: low virus production in vivo

Levels of virus in the plasma are closely related to the pathogenicity of human immunodeficiency virus type 1 (HIV-1). HIV-2 is much less pathogenic than HIV-1, and infection with HIV-2 leads to significantly lower plasma viral load. To identify the source of this difference, we measured both viral RNA and proviral DNA in matched samples from 34 HIV-2-infected individuals. Nearly half had undetectable viral RNA loads (<100 copies/ml), but levels of proviral DNA were relatively high and confirmed that quantities of provirus in HIV-1 and HIV-2 infection were similar. Overall, HIV-2 proviral DNA load did not correlate with viral RNA load, and higher viral RNA load was associated with increased production of plasma virus from the proviral template. These results suggest that low viral load in HIV-2 infection is due to decreased rates of viral production, rather than differences in target cell infectivity.

Recombinant gp160 as a therapeutic vaccine for HIV-infection: results of a large randomized, controlled trial. European Multinational IMMUNO AIDS Vaccine Study Group

OBJECTIVES

The primary objective of this study was to expand the safety and immunogenicity database of recombinant gp160 as a therapeutic vaccine in the treatment of HIV-infection. Preliminary efficacy data was also sought.

DESIGN

This trial was a randomized, double-blind, placebo-controlled study. Two-hundred and eight volunteers, 96 therapy-naive with CD4 cell count >500x10(6)/l (group A) and 112 with CD4 cell count of 200-500x10(6)/l (group B, 51 out of 112 on treatment with one or two nucleoside analogues), received monthly injections of rgp160 IIIB vaccine or placebo for the first 6 months of the study; booster immunizations with rgp160 MN or placebo were given at times 15, 18, and 21 months.

METHODS

Safety and immunogenicity data were obtained and measurements of CD4 cell count, plasma viral RNA, and proviral DNA were performed. Clinical outcome was recorded for the 24 months of study.

RESULTS

The vaccine was safe and well tolerated. Despite the induction of new rgp160-specific lymphoproliferative responses and the presence of positive delayed type hypersensitivity skin tests to rgp160 at the end of the 24 month study, no effect on the natural history of HIV infection was detected. Within 24 months, AIDS-defining illnesses had occurred in 19 of the vaccinated volunteers and in 18 of the placebo recipients. Persons with higher plasma viral RNA levels and higher proviral DNA had a more rapid decline in CD4 cell count when compared to persons with lower values. Vaccine did not alter viral RNA or proviral DNA levels.

CONCLUSION

There was no clinical benefit to therapeutic immunizations with rgp160, despite the induction of new lymphoproliferative responses.

Dynamics of provirus load and lymphocyte subsets after interleukin 2 treatment in HIV-infected patients

The association of antiretroviral agents plus interleukin 2 (IL-2) represents an efficient approach to the treatment of HIV+ subjects. While the effects of IL-2 on the immune system have been investigated, little is known concerning its impact on HIV dynamics. Two antiretroviral drugs control HIV viremia, but have minimal effects on the proviral load, a predictor of disease progression and response to therapy. The aim of this study was to define the effect of rIL-2 on HIV proviral copy numbers and its relationship to changes in CD4+ and CD8+ subsets. Twelve HIV+ patients with CD4 cell counts between 200 and 500 cells/mm3 were treated with six cycles of subcutaneous rIL-2, in combination with zidovudine and didanosine. This regimen resulted in a rapid and durable decrease in proviral load in the peripheral blood, in an increase in CD8+ lymphocytes, and in the emergence of a CD4+CD45RA+ T subset. These results demonstrate that the rationale for IL-2 administration to HIV+ patients may depend not only on its effects on the immune system, but also on the reduction of the number of infected cells, reinforcing the notion that IL-2 can have a favorable impact on the natural history of HIV infection.

Epstein-Barr virus DNA in the blood of infants, young children, and adults by age and HIV status

Polymerase chain reaction (PCR) methodology was used to detect Epstein-Barr virus (EBV) DNA in peripheral blood mononuclear cells (PBMCs) from children and adults whose HIV status (i.e., infected or uninfected) is known. Initial EBV infections especially occurred in children between the ages of 7 and 24 months. EBV-positive children with vertically acquired HIV infection tended to have a detectable blood level of EBV DNA for a period of years, and their EBV DNA blood levels often exceeded 10,000 copies/0.1 ml of blood--hundreds of times higher than levels typically found in EBV-positive, HIV-uninfected children of the same age. EBV DNA was found in PBMCs in 26% of 49 HIV-infected mothers who were sampled during their pregnancy, but the median EBV DNA level in their EBV-positive samples was low--only 50 copies/0.1 ml blood. In limited tests with specimens from children infected with both HIV and EBV, high blood levels of EBV DNA unexpectedly appeared to be associated with decreased blood levels of HIV DNA (p = .063).

Effect of therapeutic immunization with recombinant gp160 HIV-1 vaccine on HIV-1 proviral DNA and plasma RNA: relationship to cellular immune responses

Therapeutic vaccination has been proposed as a strategy to augment immune mechanisms to control viral replication and slow clinical progression of HIV infection to disease. Following recombinant gp160 (r-gp160) immunization in three clinical trials, plasma HIV-1 RNA and cellular proviral DNA were assessed by quantitative polymerase chain reaction (PCR) in 76 HIV-seropositive subjects with CD4+ T cell counts > or = 300/mm3. Immunization increased HIV-specific cellular immune responses (e.g., cytotoxic T lymphocyte [CTL] activities, lymphocyte proliferative responses); however, there were no significant effects of immunization or cellular immune responses on measures of plasma RNA or cellular DNA viral load.

Evaluation of the presence of 2-LTR HIV-1 unintegrated DNA as a simple molecular predictor of disease progression

In a preliminary cross-sectional analysis of 109 human immunodeficiency virus type 1 (HIV-1)-infected subjects the presence of 2-long terminal repeat (LTR) unintegrated circular HIV-1 DNA in peripheral blood mononuclear cells (PBMC) was found to be associated with both symptomatic infection (P = 0.0037) and low CD4 counts (P = 0.0004). To investigate the prognostic significance of the presence of 2-LTR HIV-1 DNA, a subset of 23 2-LTR-negative and 25 2-LTR-positive asymptomatic individuals were followed up for 12-24 months. The two groups did not differ in terms of baseline CD4 counts, zidovudine (ZDV) therapy, and duration of HIV-1 infection. Longitudinal analysis of CD4 values did not indicate a significantly different CD4 outcome between the two groups. However, when only ZDV-treated subjects were considered, a significant (P = 0.042) decrease in CD4 counts was found at month 24 with respect to baseline in 2-LTR-positive (n = 12) but not in 2-LTR-negative (n = 11) patients. Moreover, when > 40% CD4 loss from baseline and/or development of CDC stage B or C symptoms were considered as indicators of disease progression, there was a significantly higher number of events in the whole 2-LTR-positive group than in the whole 2-LTR-negative group (P = 0.0197 at month 12, P = 0.0299 at month 18, P = 0.0373 at month 24). Thus, the presence of 2-LTR HIV-1 DNA in PBMC merits further investigation as a simple, qualitative, molecular predictor of disease progression and decreased response to antiretroviral therapy.

HIV DNA blood levels in vertically infected pediatric patients: variations with age, association with disease progression, and comparison with blood levels in infected mothers

Blood levels of HIV DNA in our vertically infected pediatric patients typically followed a characteristic age-related pattern: continuously increasing with increasing age to a peak between ages 4 and 8 months, and thereafter rather steadily declining. Median HIV DNA levels peaked about 3 months earlier in children who by age 24 months developed more severe rather than less severe HIV disease. Children at particular risk of developing severe HIV disease by age 24 months commonly had > 800 HIV DNA copies per 0.1 ml of blood at age 3 weeks to 2 months, > 1,000 copies at 2 to 4 months, and > 2,500 copies at ages 4 to 6 months. Near the time of delivery mothers who transmitted HIV had significantly higher median blood levels of HIV DNA than mothers who did not transmit, but median HIV DNA levels in infected mothers as a group were low compared with those in pediatric patients > or = 1 month of age.

HIV-1 DNA in brains in AIDS and pre-AIDS: correlation with the stage of disease

Seventeen asymptomatic individuals positive for human immunodeficiency virus type 1 (HIV-1) and 16 patients with acquired immunodeficiency syndrome (AIDS), all with polymerase chain reaction evidence of HIV-1 DNA, were selected for quantitative analysis to correlate the levels of HIV-1 DNA in brain tissue with the stage of infection. The AIDS patients either were clinically asymptomatic or presented various abnormalities. Neuropathological lesions were assessed by morphological and immunohistochemical methods. To determine the level of HIV-1 DNA, semiquantitative nested polymerase chain reaction was applied using a digoxigenin-labeled primer and chemiluminescence. Serial dilutions of standard HIV DNA were run in parallel with brain DNA samples. Among the 16 AIDS brains studied, 9 showed changes characteristic of HIV encephalitis/leukoencephalopathy while 1 showed focal pontine leukoencephalopathy and 6 showed no obvious neuropathological lesions. Abnormalities in pre-AIDS individuals included meningitis, microgliosis, and astrogliosis. Copy numbers of HIV-1 DNA in the brains of AIDS patients were higher than those in asymptomatic individuals (median, 135 vs 45 copies/150,000 cells). However, there was some degree of overlapping between the two groups, with some AIDS patients showing low figures while 3 asymptomatic individuals had high copy numbers. This suggests that the use of HIV-1 DNA load in the central nervous system as an indicator of progression of the disease should be restricted to large series and not single patients.

High levels of anti-human immunodeficiency virus type 1 (HIV-1) memory cytotoxic T-lymphocyte activity and low viral load are associated with lack of disease in HIV-1-infected long-term nonprogressors

Lack of disease in long-term nonprogressors with human immunodeficiency virus type 1 (HIV-1) infection was strongly associated with very low copy numbers of HIV-1 DNA and RNA in peripheral blood mononuclear cells and plasma and the presence of high levels of anti-HIV-1 CD8+ memory cytotoxic T lymphocytes specific for Gag, Pol, and Env, compared with levels present in intermediate and advanced progressors. CD8+ memory cytotoxic T lymphocytes may have an important role in controlling HIV-1 replication and preventing disease in long-term nonprogressors.

Correlation between viral DNA load and serum anti p19 antibody concentration in symptomless human T-lymphotropic virus type-I (HTLV-I)-infected individuals

In order to determine whether serum anti-human T-cell lymphotropic virus type I (HTLV-I) antibody concentration is correlated with cellular viral DNA load, these 2 biological parameters were established in 22 symptomless HTLV-I carriers. The proviral copy (PVC) number was determined through quantificative polymerase chain reaction. Specific antibody titers were determined by Western blot with the end-point dilution method; the quantification of each antibody was performed through ScanBlot by determination of the peak height of each Western-blot band. A positive correlation was observed between the PVC number and the titer of total antibodies. When the association between the peak height of each antibody and the PVC number was studied, a significant positive correlation was observed only with anti-p 19. Further evaluation through follow-up studies of symptomless HTLV-I individuals is needed to clarify the value of anti-HTLV-I antibody titer as a predictor of disease progression.

AIDS as immune system activation. Key questions that remain

Immune system activation is gaining attention as a central part of HIV pathogenesis. Although there is no consensus yet as to the source of the signal or the result of the signalling, this line of thinking represents a significant shift in the paradigm away from considering HIV disease like any other cytopathic viral infection. Hopefully, completion of studies focussed on this approach will lead to more complete understanding of AIDS and more effective therapies, and will at least bring to the fore some of the central unanswered questions in modern cellular immunology.