Multivariate models for predicting progression to AIDS and survival in human immunodeficiency virus-infected persons

Development and external validation of a prognostic model for survival of people living with HIV/AIDS initiating antiretroviral therapy

Background: Most existing prognostic models for people living with HIV/AIDS (PLWHA) were derived from cohorts in high-income settings established a decade ago and may not be applicable for contemporary patients, especially for patients in developing settings. The aim of this study was to develop and externally validate a prognostic model for survival in PLWHA initiating ART based on a large population-based cohort in China.

Methods: We obtained data for patients from the Chinese National Free Antiretroviral Treatment Program database. The derivation cohort consisted of PLWHA treated between February 2004 and December 2019 in a tertiary center in Guangzhou, South China, and validation cohort of patients treated between February 2004 to December 2018 in another tertiary hospital in Shenyang, Northeast China. We included ART-naive patients aged above 16 who initiated a combination ART regimen containing at least three drugs and had at least one follow-up record. We assessed 20 candidate predictors including patient characteristics, disease characteristics, and laboratory tests for an endpoint of death from all causes. The prognostic model was developed from a multivariable cox regression model with predictors selected using the least absolute shrinkage and selection operator (Lasso). To assess the model's predictive ability, we quantified the discriminative power using the concordance (C) statistic and calibration accuracy by comparing predicted survival probabilities with observed survival probabilities estimated with the Kaplan–Meier method.

Findings: The derivation cohort included 16481 patients with a median follow-up of 3·41 years, among whom 735 died. The external validation cohort comprised 5751 participants with a median follow-up of 2·71 years, of whom 185 died. The final model included 10 predictors: age, body mass index, route of HIV acquisition, coinfection with tuberculosis, coinfection with hepatitis C virus, haemoglobin, CD4 cell count, platelet count, aspartate transaminase, and plasma glucose. The C-statistic was 0·84 (95% confidence interval 0·82–0·85) in internal validation after adjustment of optimism and 0·84 (0·82–0·87) in external validation, which remained consistently above 0·75 in all landmark time points within five years of follow up when using time-updated laboratory measurements. The calibration accuracy was satisfactory in both derivation and validation cohorts.

Interpretation: We have developed and externally validated a model to predict long-term survival in PLWHA on ART. This model could be applied to individualized patient counseling and management during treatment, and future innovative trial design.

Funding: Natural Science Foundation of China Excellent Young Scientists Fund, Natural Science Foundation of China International/Regional Research Collaboration Project, Natural Science Foundation of China Young Scientist Fund, the National Science and Technology Major Project of China,National Special Research Program of China for Important Infectious Diseases, 13th Five-Year Key Special Project of Ministry of Science and Technology, and the Joint-innovation Program in Healthcare for Special Scientific Research Projects of Guangzhou.

Impaired Neurocognitive Performance and Mortality in HIV: Assessing the Prognostic Value of the HIV-Dementia Scale

This study examined whether global HIV-associated neurocognitive impairment (NCI), assessed with the HIV-Dementia Scale (HDS), predicted mortality in an ethnically diverse sample of 209 HIV-positive adults. Participants were predominantly in the mid-range of illness at baseline, and followed over 13-years. At baseline, 31 (15%) participants scored in the NCI range (HDS ≤ 10); 58 (28%) died during follow-up. Baseline NCI was significantly associated with earlier mortality (HR = 2.10, 95% CI [1.10-4.00]) independent of sociodemographic and HIV disease-related covariates. Less errors on the antisaccade task, an index of executive/attention control, was the only HDS subtest predicting earlier mortality (HR = 0.72, 95% CI [0.58-0.90]). In the absence of an AIDS-defining condition, NCI, particularly in the executive/attention domain, is an independent prognostic marker of mortality in a diverse HIV-positive cohort. These findings highlight the clinical utility of brief cognitive screening measures in this population.

Host factors determine differential disease progression after infection with nef-deleted simian immunodeficiency virus

Infection of macaques with live attenuated simian immunodeficiency virus (SIV) usually results in long-lasting efficient protection against infection with pathogenic immunodeficiency viruses. However, attenuation by deletion of regulatory genes such as nef is not complete, leading to a high viral load and fatal disease in some animals. To characterize immunological parameters and polymorphic host factors, we studied 17 rhesus macaques infected with attenuated SIVmac239ΔNU. Eight animals were able to control viral replication, whereas the remaining animals (non-controllers) displayed variable set-point viral loads. Peak viral load at 2 weeks post-infection (p.i.) correlated significantly with set-point viral load (P<0.0001). CD4(+) T-cell frequencies differed significantly soon after infection between controllers and non-controllers. Abnormal B-cell activation previously ascribed to Nef function could already be observed in non-controllers 8 weeks after infection despite the absence of Nef. Two non-controllers developed an AIDS-like disease within 102 weeks p.i. Virus from these animals transmitted to naïve animals replicated at low levels and the recipients did not develop immunodeficiency. This suggested that host factors determined differential viral load and subsequent disease course. Known Mhc class I alleles associated with disease progression in SIV WT infection only marginally influenced the viral load in Δnef-infected animals. Protection from SIVmac251 was associated with homozygosity for MHC class II in conjunction with a TLR7 polymorphism and showed a trend with initial viral replication. We speculated that host factors whose effects were usually masked by Nef were responsible for the different disease courses in individual animals upon infection with nef-deleted viruses.

Delayed-type hypersensitivity and hepatitis B vaccine responses, in vivo markers of cellular and humoral immune function, and the risk of AIDS or death

BACKGROUND

Delayed-type hypersensitivity (DTH) test responsiveness is associated with HIV disease progression; however it is unknown whether other immune markers, such as hepatitis B virus (HBV) vaccine seroresponse, also predict HIV outcomes.

METHODS

Eligible participants received HBV vaccine after HIV diagnosis, had non-anergic DTH testing at the time of last HBV vaccination, and available post-vaccine HBV antibody responses. The risk of progression to AIDS or death from the time of last HBV vaccination was evaluated.

RESULTS

Of 369 eligible participants with non-anergic DTH responses, 148 (40%) were HBV vaccine responders. In a multivariate model adjusted for age, CD4 count, viral load, and number of vaccinations, HBV vaccine non-responders had an increased risk of progression to AIDS or death (HR 1.81; 95% CI, 1.03-3.19).

CONCLUSIONS

HBV vaccine seroresponses were independent of DTH responses which suggest that non-response to HBV vaccine is not solely due to cell-mediated immune dysfunction in HIV-infected persons.

Highly active antiretroviral therapy reduces the age-associated risk of dementia in a cohort of older HIV-1-infected patients

Historically, older patients have shown a higher risk of HIV-1-associated dementia (HIVD). The objective of this study was to evaluate the association of aging with HIVD and minor cognitive motor disorders (MCMDs) during the late-highly active antiretroviral therapy (HAART) era and to analyze characteristics, predictive factors, and survival of older HIV-1-infected individuals affected by these disorders. A nested longitudinal study was designed for a cohort of HIV-1-infected individuals with neurological diseases. Multiple logistic regression and Cox regression for survival were employed. From 2000 to 2003, 195 patients with HIVD (53%) or MCMD (47%) were enrolled. The cumulative prevalence of these two disorders was 21%, with an increasing rate for calendar year (p < 0.001). Previous antiretroviral exposure occurred in 46% of patients. Mean CD4(+) cell count and plasma HIV-1 RNA were 144 cells/microl and 4.5 log10 copies/ml, respectively. The mean age was 44 years (SD, 9.9), with 35% of patients aged 20-39 years (I), 45% aged 40-49 years (II), and 20% aged >/=50 years (III). Among drug-naive patients, the prevalence of HIVD progressively increased in older subjects: 7.2% (I), 15.3% (II), and 27.3% (III) (p < 0.001), whereas no significant increase in HIVD with older age was observed in drug-treated subjects. Older age was independently associated with an increased risk of HIVD (odds ratio, 6.44; 95% confidence interval, 2.82-14.69) in naive but not in experienced individuals, but had no significant effect on survival. No significant effect of age was observed for MCMD. We conclude that in our cohort, HAART seems to alter the relationship between aging and HIVD, conferring a neuroprotective effect to older patients. These results may have significant implications for the clinical management of the older HIV population.

Salivary gland function in HIV-infected patients treated with highly active antiretroviral therapy (HAART)

OBJECTIVE

This study was undertaken to determine if HAART alters salivary oral host defense in HIV(+) men.

STUDY DESIGN

Whole, parotid, and submandibular/sublingual saliva was collected from 39 healthy men and 147 HIV(+) patients with mild to moderate immune dysfunction (69 treated with HAART [HAART(+)]; 78 not treated [HAART(-)]). Salivary flow rates, anticandidal activities, electrolytes, and antimicrobial/antifungal proteins were determined.

RESULTS

While CD4(+) cell counts were not different between the HIV(+) groups, the median viral load for HAART(-) was 15 times greater than HAART(+). For both HAART groups, salivary yeast carriage rates and concentration were comparable and both showed similar reductions in salivary flow rates. Salivary anticandidal activities were not altered. Saliva composition of both HIV(+) groups was different from control, but only uric acid in parotid saliva of HAART(+) differed from HAART(-).

CONCLUSIONS

HAART does not adversely affect inherent salivary oral host defense in HIV(+) patients with mild to moderate immune dysfunction.

Alteration in salivary function in early HIV infection

The etiology of salivary gland hypofunction in HIV(+) patients is unclear. This study was designed to determine the effect of early-stage HIV(+) infection (CD4(+) > 200 cells/ micro L; n = 139) on salivary gland function and the relationship of this dysfunction to the taking of xerostomic medications. Salivary flow rates and the content of electrolytes and antimicrobial proteins in stimulated parotid and submandibular/sublingual saliva were determined. Compared with healthy controls (n = 50), the HIV(+) group showed significant reductions in flow rates of unstimulated whole (35%), stimulated parotid (47%), unstimulated submandibular/sublingual (23%), and stimulated submandibular/sublingual (39%) saliva. The flow rates for the HIV(+) patients taking xerostomic medications did not differ from those of patients who did not. Concentrations of some salivary gland components were altered in the HIV(+) group. Analysis of these data suggests that salivary gland function is adversely affected early in HIV infection and that these changes do not appear to be compounded by the taking of xerostomic medications.

Correlates of immune activation marker changes in human immunodeficiency virus (HIV)-seropositive and high-risk HIV-seronegative women who use illicit drugs

The majority of natural history studies of human immunodeficiency virus (HIV) infection have immune and viral parameters in men. Data demonstrating that women have lower HIV-1 RNA levels than men at the same CD4 cell counts have raised the question of immunologic differences in HIV-seropositive women. This study describes levels and changes in phenotypic markers of immune maturity, function, and activation in the CD4 and CD8 cell subsets in HIV-seropositive and high-risk HIV-seronegative women. Our primary hypothesis was that activation levels would be significantly higher among illicit drug users. However, results showed that HIV-1 RNA level was the strongest predictor of marker level and that both HIV-1 RNA level and CD4 cell count were independently associated with CD4 activation, but illicit drug use was not. In summary, this study demonstrated that immune activation was a significant pathogenic feature in women and that activation was driven by HIV infection and not illicit drug use.

nef gene is required for robust productive infection by simian immunodeficiency virus of T-cell-rich paracortex in lymph nodes

The pathogenesis of AIDS virus infection in a nonhuman primate AIDS model was studied by comparing plasma viral loads, CD4(+) T-cell subpopulations in peripheral blood mononuclear cells, and simian immunodeficiency virus (SIV) infection in lymph nodes for rhesus macaques infected with a pathogenic molecularly cloned SIVmac239 strain and those infected with its nef deletion mutant (Deltanef). In agreement with many reports, whereas SIVmac239 infection induced AIDS and depletion of memory CD4(+) T cells in 2 to 3 years postinfection (p.i.), Deltanef infection did not induce any manifestation associated with AIDS up to 6.5 years p.i. To explore the difference in SIV infection in lymphoid tissues, we biopsied lymph nodes at 2, 8, 72, and 82 weeks p.i. and analyzed them by pathological techniques. Maximal numbers of SIV-infected cells (SIV Gag(+), Env(+), and RNA(+)) were detected at 2 weeks p.i. in both the SIVmac239-infected animals and the Deltanef-infected animals. In the SIVmac239-infected animals, most of the infected cells were localized in the T-cell-rich paracortex, whereas in the Deltanef-infected animals, most were localized in B-cell-rich follicles and in the border region between the paracortex and the follicles. Analyses by double staining of CD68(+) macrophages and SIV Gag(+) cells and by double staining of CD3(+) T cells and SIV Env(+) cells revealed that SIV-infected cells were identified as CD4(+) T cells in either the SIVmac239 or the Deltanef infection. Whereas the many functions of Nef protein were reported from in vitro studies, our finding of SIVmac239 replication in the T-cell-rich paracortex in the lymph nodes supports the reported roles of Nef protein in T-cell activation and enhancement of viral infectivity. Furthermore, the abundance of SIVmac239 infection and the paucity of Deltanef infection in the T-cell-rich paracortex accounted for the differences in viral replication and pathogenicity between SIVmac239 and the Deltanef mutant. Thus, our in vivo study indicated that the nef gene enhances SIV replication by robust productive infection in memory CD4(+) T cells in the T-cell-rich region in lymphoid tissues.

Replication, immunogenicity, and protective properties of live-attenuated simian immunodeficiency viruses expressing interleukin-4 or interferon-gamma

Nef deletion mutants of SIV-expressing interleukin-4 (SIV-IL4) or interferon-gamma (SIV-IFN) were constructed to study the effect of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) on viral load, immunogenicity, and protective properties. Four rhesus monkeys were infected with SIV-IL4 and four were infected with SIV-IFN. During the acute phase of infection, the cell-associated viral load, but not the plasma viral RNA load, was approximately 10-fold lower in SIV-IFN-infected macaques than in SIV-IL4-infected rhesus monkeys. The viral load declined to hardly detectable levels 4 months postinfection in all animals. SIV antibody titers and the affinity of these antibodies were higher in SIV-IL4-infected macaques than in SIV-IFN-infected animals, consistent with a stimulation of T helper cell type 2 immune responses by IL-4. At peak viremia, there was a trend to higher interleukin-12 and perforin mRNA levels of the lymph nodes in the SIV-IFN-infected macaques than in the SIV-IL4-infected monkeys. Deletion of the viral IFN gene, but not the viral IL-4 gene, after the development of antiviral immune responses suggests a repressive effect of IFN, but not IL-4, on virus spread in vivo. A trend to higher set point viral RNA levels in SIV-IL4-infected monkeys in comparison to monkeys infected with the parental nef deletion mutant and similar viral RNA levels during the acute phase of infection suggest that IL-4 expression leads to a slight reduction in the control of virus replication by host immune responses. However, SIV-IL4 and SIV-IFN induced protection against a homologous challenge virus. Subsequent challenge with an SIV-HIV-1 hybrid virus (SHIV) also revealed protection in the absence of neutralizing antibodies.

Markers of HIV-1 disease progression in individuals with haemophilia coinfected with hepatitis C virus: a longitudinal study

BACKGROUND

Low serum albumin concentration is associated with short-term survival in individuals with HIV-1. However, few investigators have assessed whether individuals with a low serum albumin concentration have delayed progression to AIDS, or survive in the long term. We aimed to assess the relation between markers of liver function and progression to AIDS and death in individuals with haemophilia infected with HIV-1 and hepatitis C virus.

METHODS

We measured markers of liver function and took CD4 counts every 3 months in 111 patients registered at the Royal Free Hospital Haemophilia Centre, London, UK. HIV RNA concentrations were measured yearly and then every 3-6 months from 1996. We used Cox's regression models to assess the independent prognostic value of these markers for AIDS and death.

FINDINGS

As a fixed covariate, albumin concentrations measured shortly after HIV-1 seroconversion were associated with risk of AIDS (relative hazard 0.91 [95% CI 0.84-1.00], p=0.04) and death (0.89 [0.82-0.96], p=0.004) over a 15-year period. These findings were independent of the CD4 count and HIV-1 RNA concentration. As a time-updated covariate, after adjustment for CD4 count and HIV-1 RNA concentrations, albumin was not associated with progression to AIDS (0.96 [0.90-1.01], p=0.13), but was strongly associated with death (0.88 [0.84-0.93], p<0.0001) in the short term.

INTERPRETATION

Low concentrations of albumin in individuals infected with HIV-1 could indicate a poor outlook and should therefore prompt concern at any stage of infection.

Contribution of immune activation to the pathogenesis and transmission of human immunodeficiency virus type 1 infection

The life cycle of human immunodeficiency virus type 1 (HIV-1) is intricately related to the activation state of the host cells supporting viral replication. Although cellular activation is essential to mount an effective host immune response to invading pathogens, paradoxically the marked systemic immune activation that accompanies HIV-1 infection in vivo may play an important role in sustaining phenomenal rates of HIV-1 replication in infected persons. Moreover, by inducing CD4+ cell loss by apoptosis, immune activation may further be central to the increased rate of CD4+ cell turnover and eventual development of CD4+ lymphocytopenia. In addition to HIV-1-induced immune activation, exogenous immune stimuli such as opportunistic infections may further impact the rate of HIV-1 replication systemically or at localized anatomical sites. Such stimuli may also lead to genotypic and phenotypic changes in the virus pool. Together, these various immunological effects on the biology of HIV-1 may potentially enhance disease progression in HIV-infected persons and may ultimately outweigh the beneficial aspects of antiviral immune responses. This may be particularly important for those living in developing countries, where there is little or no access to antiretroviral drugs and where frequent exposure to pathogenic organisms sustains a chronically heightened state of immune activation. Moreover, immune activation associated with sexually transmitted diseases, chorioamnionitis, and mastitis may have important local effects on HIV-1 replication that may increase the risk of sexual or mother-to-child transmission of HIV-1. The aim of this paper is to provide a broad review of the interrelationship between immune activation and the immunopathogenesis, transmission, progression, and treatment of HIV-1 infection in vivo.

Predicting HIV disease progression in children using measures of neuropsychological and neurological functioning. Pediatric AIDS clinical trials 152 study team

BACKGROUND

Neuropsychological testing and 2 measures of neurological status, cortical atrophy, and motor dysfunction were assessed for their usefulness in predicting human immunodeficiency virus (HIV) disease progression in infants, children, and adolescents who participated in Pediatric AIDS Clinical Trials Group Protocol 152 (PACTG 152).

METHODS

A cohort of 722 antiretroviral therapy-naive children with symptomatic HIV infection were assessed at study entry and at later intervals. Assessments included neurodevelopmental testing, neuroradiologic imaging, and neurological examination of motor function. CD4 cell count and plasma RNA viral load also were measured.

RESULTS

Children with the lowest neuropsychological functioning (IQ < 70) at baseline had the highest risk for later HIV disease progression (56%), compared with those with borderline/low (IQ = 70-89) functioning (26%), or with average or above (IQ > 90) functioning (18%). This was also true of week 48 neuropsychological functioning. Motor dysfunction (especially reduced muscle mass) at entry also predicted disease progression. Furthermore, motor dysfunction and week 48 neuropsychological functioning provided predictive information beyond that obtainable from surrogate markers of HIV disease status (eg, CD4 count, HIV RNA level). Children with cortical atrophy also were at higher risk for later disease progression, but when CD4 count and RNA viral load were known, cortical atrophy information provided no additional predictive information.

CONCLUSIONS

Measures of neuropsychological and motor function status provide unique information regarding pediatric HIV disease progression. As such, these findings have important implications for predicting long-term outcomes (eg, longevity) in pediatric patients.

Consensus statement: anemia in HIV infection--current trends, treatment options, and practice strategies. Anemia in HIV Working Group

BACKGROUND

Despite important advances in antiretroviral therapy, anemia remains a problem in many HIV-infected patients. Although the incidence of anemia in these patients has decreased, its prevalence appears to have stabilized or decreased only slightly. Anemia has a deleterious effect on both functional capacity and quality of life, and has been associated with shortened survival.

OBJECTIVE

The Anemia in HIV Working Group, an expert panel of physicians and researchers involved in the care of HIV-infected patients, met to determine the impact of anemia in this patient population; to develop practice strategies for the clinician treating HIV-infected patients with anemia; and to identify future research directions.

METHODS

The proposed practice strategies are based on results of the available clinical trials (as identified through a MEDLINE search), a review of the literature, and the clinical experience and expert opinion of the panel. The present report is based on meetings held in February and June of 1998; as further experience with various treatment options accumulates and the impact of highly active antiretroviral therapy becomes clearer, the panel will reconvene to develop evidence-based guidelines.

RESULTS

The working group considers HIV-associated anemia to be an important contributor to the morbidity and mortality of this infection. Recent reports indicate that recovery from anemia is associated with improved quality of life and survival.

CONCLUSIONS

As HIV-infected persons live longer, maintaining quality of life becomes an increasingly important goal of treatment. When planning treatment strategies, clinicians should consider the quality-of-life decrement caused by anemia. Transfusions should be used when rapid recovery is required, and underlying conditions causing anemia should be treated, if possible. Recombinant human erythropoietin (rHuEPO) therapy is appropriate in certain HIV-infected persons and should be considered to maintain hemoglobin concentrations. The target hemoglobin level is 12 g/dL for men and 11 g/dL for women. Weekly rHuEPO dosing is suggested, initiated at 40,000 U, as has been established in patients with cancer.

Evidence for recombination of live, attenuated immunodeficiency virus vaccine with challenge virus to a more virulent strain

Live, attenuated immunodeficiency virus vaccines, such as nef deletion mutants, are the most effective vaccines tested in the simian immunodeficiency virus (SIV) macaque model. In two independent studies designed to determine the breadth of protection induced by live, attenuated SIV vaccines, we noticed that three of the vaccinated macaques developed higher set point viral load levels than unvaccinated control monkeys. Two of these vaccinated monkeys developed AIDS, while the control monkeys infected in parallel remained asymptomatic. Concomitant with an increase in viral load, a recombinant of the vaccine virus and the challenge virus could be detected. Therefore, the emergence of more-virulent recombinants of live, attenuated immunodeficiency viruses and less-aggressive wild-type viruses seems to be an additional risk of live, attenuated immunodeficiency virus vaccines.

Env-independent protection induced by live, attenuated simian immunodeficiency virus vaccines

Live attenuated simian immunodeficiency viruses (SIV), such as nef deletion mutants, are the most effective vaccines tested in the SIV-macaque model so far. To modulate the antiviral immune response induced by live attenuated SIV vaccines, we had previously infected rhesus monkeys with a nef deletion mutant of SIV expressing interleukin 2 (SIV-IL2) (B. R. Gundlach, H. Linhart, U. Dittmer, S. Sopper, S. Reiprich, D. Fuchs, B. Fleckenstein, G. Hunsmann, S. Stahl-Hennig, and K. Uberla, J. Virol. 71:2225-2232, 1997). In the present study, SIV-IL2-infected macaques and macaques infected with the nef deletion mutant SIVDeltaNU were challenged with pathogenic SIV 9 to 11 months postvaccination. In contrast to the results with naive control monkeys, no challenge virus could be isolated from the SIV-IL2- and SIVDeltaNU-infected macaques. However, challenge virus sequences could be detected by nested PCR in some of the vaccinated macaques. To determine the role of immune responses directed against Env of SIV, four vaccinated macaques were rechallenged with an SIV-murine leukemia virus (MLV) hybrid in which the env gene of SIV had been functionally replaced by the env gene of amphotropic MLV. All vaccinated macaques were protected from productive infection with the SIV-MLV hybrid in the absence of measurable neutralizing antibodies, while two naive control monkeys were readily infected. Since the SIV-MLV hybrid uses the MLV Env receptor Pit2 and not CD4 and a coreceptor for virus entry, chemokine inhibition and receptor interference phenomena were not involved in protection. These results indicate that the protective responses induced by live attenuated SIV vaccines can be independent of host immune reactions directed against Env.

Lymphocyte phenotyping in infants: maturation of lymphocyte subpopulations and the effects of HIV infection

Changes in the distribution of lymphocyte subpopulations in infants with perinatally acquired HIV infection are confounded by the rapid changes that are the result of normal maturation of the immune system. We describe the changes in seven lymphocyte phenotypes (CD3+ CD4+, CD3+ CD8+, CD8+ HLA- DR+, CD8+ CD38+, CD8+ CD57+, CD3-/ CD16+ 56+, and CD19+) over the first 2 years of life in 390 HIV-1 exposed but uninfected and 98 HIV-1-infected infants enrolled in the Women and Infants Transmission Study. The greatest changes in uninfected infants were declines in the CD3+ CD4+ lymphocytes and increases in CD8+ HLA- DR+ and CD19+ lymphocytes. All phenotypes were affected by HIV infection but the greatest changes were declines in the CD3+ CD4+ subset and increases in the CD3+ CD8+ and CD8+ HLA- DR+ subsets. Thus, this study provides reference data for the maturational changes in lymphocyte phenotypes in HIV-exposed but uninfected infants and describes the overall changes that occur with perinatally acquired HIV infection.

Rapid and selective depletion of CD4+ T lymphocytes and preferential loss of memory cells on interaction of mononuclear cells with HIV-1 glycoprotein-expressing cells

Contact of HIV glycoprotein-expressing cells with CD4+ T lymphocytes in vitro causes cell-cell fusion and/or cytopathogenicity. The question of whether this process similarly underlies the death of helper T cells in vivo has not yet been resolved. To investigate the loss of uninfected CD4+ T cells in an environment that may reflect the in vivo situation, unfractionated, unstimulated peripheral blood mononuclear cells were cocultured with HIV-1 glycoprotein-expressing cells, and early alterations of T-cell numbers were quantitated using a newly developed quantitative flow cytometric assay. The results demonstrate that a large fraction of normal-sized, regular CD4+ T cells disappeared immediately on cocultivation with envelope glycoprotein-expressing cells. In contrast, CD8+ T lymphocytes remained unaffected. Significant loss of uninfected T-helper cells required the presence of less than 1% infected cells. Moreover, memory T cells (CD45RO+, CD29 hi+) were depleted more rapidly than naive cells (CD45RO-, CD29 lo+). The observation that a large fraction of intact primary T-helper cells disappeared on contact with HIV glycoprotein-expressing cells suggests that a similar process may occur in vivo and contribute to the loss of T-helper cells in the infected individual. In addition, the preferential loss of memory cells may account for the early loss of immune functions in the course of HIV infection.

Increased losses of CD4+CD45RA+ cells in late stages of HIV infection is related to increased risk of death: evidence from a cohort of 347 HIV-infected individuals

OBJECTIVE

To examine changes in the distribution of CD4+CD45RA+ (naive) and CD4+CD45RO+ (memory) lymphocytes in various stages of HIV infection and the effect of these changes on disease progression.

DESIGN AND METHODS

Expression of CD45RA+ and CD45RO+ on CD4+ lymphocytes was analysed by flow cytometry in a prospectively followed cohort of 300 HIV-infected individuals (median follow-up time, 2.90 years; range, 0.02-4.54 years) and in a group of 102 age- and sex-matched uninfected controls. Survival analysis was performed considering AIDS development and death as endpoints.

RESULTS

The median CD4+CD45RA+/CD45RO+ ratio was 1.3 (25-75% quartiles, 0.9-2.4) in controls; it was increased to 1.8 (1.1-2.5) in 40 HIV-infected individuals with CD4+ cell counts > 500 x 10(6)/l (P < 0.05); it was similar at 1.4 (0.8-2.0) in 106 HIV-infected individuals with CD4+ cell counts of 200-500 x 10(6)/l; and it was decreased to 0.9 (0.5-1.4) in 154 HIV-infected individuals with CD4+ cell counts < 200 x 10(6)/l (P < 10[-6]). When fitted in a Cox model adjusting for the total number of CD4+ cells and age a lower concentration of CD4+CD45RA+ cells was associated with an increased risk of dying. The concentration of CD4+CD45RO+ cells was not significantly associated with AIDS or death in age- and CD4+ cell count-adjusted Cox models.

CONCLUSIONS

This study confirms a selective loss of memory CD4+ cells early in HIV infection followed by increased loss of naive CD4+ cells in later stages of the infection. The loss of naive CD4+ cells seems to be important in the pathogenesis of terminal HIV infection.

HIV infection and aging: mechanisms to explain the accelerated rate of progression in the older patient

Age is an important predictor of progression in HIV infections. Not only do older individuals' develop AIDS more rapidly than younger persons, they die more quickly after developing an AIDS-defining illness. While the elderly have higher morbidity and mortality rates from viral and bacterial infections, the mechanism(s) responsible for the more rapid progression of HIV infection in older individuals has not been described. Our results demonstrate that the destruction of T cells in both young and old HIV infected patients progresses at the same rate. HIV 1-infected cells from older individuals do not appear more susceptible to immune mediated destruction. The more rapid progression appears due to an inability of older persons to replace functional T cells that are being destroyed. These findings suggest that improved survival in older HIV infected individuals will require more aggressive antiretroviral therapies as well as continued research to identify and preserve immune system elements that control the virus.

Survival after AIDS-defining events in patients with < 200 lymphocytes CD4+ x 10(6)/L who are toxoplasmosis antibody positive. ANRS 005/ACTG 154 Trial Group

The objective of this study was to assess whether patients with CD4+ cell counts <200 x 10(6)/L have a decreased survival after the occurrence of any AIDS-defining event; 187 patients from the placebo arm of a clinical trial of toxoplasmosis prophylaxis (ANRS005-ACTG154) were included. For this analysis, patients were HIV infected without any AIDS-defining event, had a CD4+ lymphocyte count < 200 x 10(6)/L, had a positive serology for Toxoplasma gondii, and had no severe liver, renal, or hematologic abnormalities. We used proportional hazards regression to study the relationships between baseline variables. AIDS-defining events as time-dependent variables, and survival. The risk of dying was increased by 1.9 for a 10-year increase in age and by 1.3 when CD4+ decreased by 50 x 10(6)/L; after the occurrence of a pneumocystosis, a cytomegalovirus infection, or a toxoplasmosis, the risk of dying was multiplied, respectively, by 10.9 (3.0-40.2), 10.0 (2.8-35.4), and 10.0 (4.5-22.2). None of the other AIDS-defining events was associated with an increased risk of dying, but the power to detect such an association was limited. We conclude that the occurrence of pneumocystosis, cytomegalovirus infection, or toxoplasmosis; age; and CD4+ cell count are important determinants of survival for HIV1-infected patients with CD4+ counts < 200 x 10(6)/L who are toxoplasmosis antibody positive.

Construction, replication, and immunogenic properties of a simian immunodeficiency virus expressing interleukin-2

To study the effect of interleukin-2 (IL-2) on simian immunodeficiency virus (SIV) replication, pathogenesis, and immunogenicity, we replaced the nef gene of SIVmac239 by the IL-2 coding region. The virus, designated SIV-IL2, stably expressed high levels of IL-2 in cell culture. In comparison to SIVmac239, SIV-IL2 replicated more efficiently in peripheral blood mononuclear cells in the absence of exogenously added IL-2. To determine whether this growth advantage would be of relevance in vivo, four juvenile rhesus monkeys were infected with SIV-IL2 and four monkeys were infected with a nef deletion mutant of SIV (SIVdeltaNU). After a peak in the cell-associated viral load 2 weeks postinfection, the viruses could barely be isolated 3 to 7 months postinfection. Mean capsid antigen levels were higher in the SIV-IL2 group than in the nef deletion group 2 weeks postinfection. Viruses reisolated from the SIV-IL2-infected animals expressed high levels of IL-2 during the acute phase of infection. Deletions in the IL-2 coding region of SIV-IL2 were observed in two of the SIV-IL2-infected macaques 3 months postinfection. Urinary neopterin levels, a marker for unspecific immune stimulation, were higher in the SIV-IL2-infected macaques than in SIVdeltaNU-infected animals during the acute phase of infection. The SIV-specific T-cell-proliferative response and antibody titers were similar in both groups. Cytotoxic T cells directed against viral antigens were detected in all SIV-IL2-infected macaques and in two of the SIVdeltaNU-infected animals. Expression of IL-2 did not seem to alter the attenuated phenotype of nef deletion mutants fundamentally, although there might have been a slight increase in virus replication and immune stimulation during the acute phase of infection. Deletion of the viral IL-2 gene 3 months postinfection could be a consequence of a selective disadvantage due to local coexpression of viral antigen and IL-2 in the presence of an antiviral immune response.

Prospective longitudinal analysis of viral load and surrogate markers in relation to clinical progression in HIV type 1-infected persons

The temporal relationship between viral and surrogate markers and clinical status was analyzed prospectively every 8 weeks in 34 asymptomatic HIV-1-infected persons. After 3 years, 25 persons remained clinically healthy whereas 9 persons showed clinical progression. In accordance with other reports we found that at study entry HIV-RNA load was predictive of clinical progression. All markers tested evolved significantly in time in both progressors and nonprogressors. The HIV RNA load in plasma and HIV DNA load in T cells were linearly related only in nonprogressors. In addition, the RNA/DNA ratio during follow-up was significantly higher in progressors, indicating a higher replication rate in progressors. The HIV DNA load correlated inversely with CD4+ T cell counts and positively with p24 antigenemia in both nonprogressors and progressors. A significant correlation of HIV DNA load with SI phenotype occurred in progressors only. HIV RNA levels correlated with beta 2-microglobulin level and with p24 antigenemia but not with SI phenotype. These three markers can all routinely be measured in plasma; however, only the HIV RNA levels appear to be informative for clinical progression. Six to 8 months before clinical progression, an SI phenotype switch, increased HIV RNA in plasma, and decreased CD4+ T cell counts were all indicative of an impending clinical event.