High IL-7 plasma levels may induce and predict the emergence of HIV-1 virulent strains in pediatric infection.

BACKGROUND: HIV-1 infection results in severe immunodeficiency when T-cell loss cannot be compensated. IL-7 is one of the main cytokines involved in the maintenance of T-cell homeostasis. However, IL-7 can also enhance HIV-1 replication in vivo and lead to an accelerated progression of AIDS. OBJECTIVE: The aim of our study was to evaluate if the increase of IL-7 levels in response to CD4+ T cell depletion could favor the emergence of HIV-1 strains with more aggressive phenotypes in pediatric infection. STUDY DESIGN: Plasma IL-7 levels were measured in 42 HIV-1 vertically infected infants at different times of infection, and HIV-1 isolates were obtained from primary cell cultures to determine replication rate and syncytium-inducing (SI) capability on MT-2 cell line. RESULTS: IL-7 levels were significantly higher in infants harboring HIV-1 SI strains compared to those with non-syncytium-inducing (NSI) viruses (p<0.0001). Likewise, IL-7 levels were higher in infants with rapid replicating viral strains versus those with slow replicating viruses (p=0.0006). Despite the strong negative correlation between IL-7 levels and CD4+ T lymphocyte counts (r=-0.55, p=0.0001), covariance analysis demonstrated that the high levels of IL-7 were associated with more virulent phenotype features (SI and rapid replicating strains) independently of CD4+ T cell depletion. In 19 of the 42 infants, longitudinal follow-up studies showed that SI to NSI phenotype switch can occur after HAART administration, with a reduction in IL-7 levels and an increase in CD4+ T cell counts. CONCLUSIONS: IL-7 response to T-cell depletion may enhance T-cell production, but at the same time may foster HIV-1 disease progression favoring the emergence of more virulent HIV-1 strains characterized by SI capability and rapid replication rate.     

Effect of the HIV-1 syncytium-inducing phenotype on disease stage in vertically-infected children

The syncytium-inducing (SI) capability of HIV-1 isolates from 48 HIV-infected children was determined in order to examine the association of the SI phenotype with an AIDS diagnosis and/or with other clinical parameters in HIV-infected children. In a retrospective cross-sectional analysis, phenotypic data were linked to clinical and immunologic data from each patient. Multiple longitudinal samples were analyzed from 14 patients. Children with SI viruses were older than children with nonsyncytium-inducing (NSI) strains. Twelve of 13 children less than 2 years old carried NSI viruses, seven of the 12 already had a diagnosis of AIDS. Two children under 2 years of age died within 1 month of NSI virus isolation. Although plasma p24 antigen levels tended to be higher in the NSI group, the difference appeared to reflect high p24 levels in children under 2 years old with AIDS. When children under 2 were omitted, differences in age, CD4+ cell counts, p24 antigenemia, and clinical parameters were not significant. The SI phenotype of HIV-1 did not occur more frequently in children with an AIDS diagnosis. Four children remained stable with SI isolates over time periods of 16 to 31 months. Three children's isolates converted from NSI to SI and 2 converted from SI to NSI. These data indicate that SI viruses do not play a significant role in progression to AIDS during the first 2 years of life. Furthermore, for children above the age of 2, the association between advanced disease stage and the SI phenotype in adults may not apply. J. Med. Virol. 55:56–63, 1998. © 1998 Wiley-Liss, Inc.     

Virological and Immunological Response to HAART Therapy in a Community-Based Cohort of HIV-1-Positive Individuals

Abstract

Purpose: To determine virological and immunological response to highly active antiretroviral therapy (HAART) and to investigate factors influencing response in a community-based setting. Method: Plasma HIV RNA levels and CD4 cell counts were studied in 168 unselected individuals starting HAART including indinavir or ritonavir or hard-gel saquinavir-containing regimens. Results: Overall, 60% of the patients reduced their HIV RNA to below 500 Eq/mL, but half of them experienced a subsequent virologic rebound. Patients with higher baseline HIV RNA, higher baseline CD4 cell count, and simultaneous initiation of combination therapy and patients on indinavir or ritonavir regimen were more likely to have virologic response within 6 months since HAART initiation. Patients with lower baseline CD4 cell count and with lower rates of viral clearance had a higher probability of a subsequent virologic rebound. Forty percent of the patients had increased their CD4 cell counts by more than 100 cells/μL (immunologic response). The probability of immunologic response was independent of baseline HIV RNA levels and CD4 cell count; however, the more complete the virologic suppression, the higher the probability of immunologic response. Thirty percent of the patients had discordance between virologic and immunologic responses. Conclusion: The rate of virologic failure in this unselected group of patients was higher than that observed in randomized clinical trials, but only a minority (11%) of the patients were treatment naïve. Starting combination therapy simultaneously and initiating antiretroviral therapy before advanced HIV disease has developed predict virologic response, whereas the magnitude of viral suppression predicts mid to long immunological response.     

Biological properties of primary HIV-1 isolates with varying serotype]

Russian HIV variants with common (rapid/high SI and slow/low NSI) and rare (slow/low SI and rapid/high NSI) phenotypes are described. SI variants demonstrate a higher p24 concentration level than serotype-independent NSI. The majority of SI variants belonging to A, B, and C serotypes were isolated from patients with mainly stage B3. At stages B2 and C2, when the majority of viruses are characterized by NSI phenotype, serotype D isolates are characterized only by SI phenotype. The spectrum of cell tropism was wide for all rapid/high strains and narrow for all slow/low ones.     

Coreceptor usage and RANTES sensitivity of non-syncytium-inducing HIV-1 isolates obtained from patients with AIDS

OBJECTIVES: The biologic phenotype of HIV-1 primary isolates obtained from approximately 50% of patients who progress to AIDS switches from non-syncytium-inducing (NSI) to syncytium-inducing (SI). We evaluated possible associations between virus coreceptor usage, sensitivity to inhibition by beta-chemokines, and disease progression of patients who continue to yield NSI isolates after developing AIDS. STUDY DESIGN/METHODS: Sequential virus isolates were analyzed for biologic phenotype using the MT-2 cell assay, for sensitivity to beta-chemokines using RANTES inhibition, and for coreceptor usage using U87.CD4 and GHOST.CD4 cells expressing different chemokine/orphan receptors or donor peripheral blood mononuclear cells (PBMC) defective in CCR5 expression. In addition, the env V3 region was sequenced and the length of the V2 region determined. RESULTS: All NSI isolates, regardless of patient status at time of isolation, were dependent on CCR5 expression for cell entry. Furthermore, there was no indication of broadened coreceptor usage of NSI isolates obtained from persons with late-stage AIDS. A majority of NSI isolates remained RANTES sensitive; however, virus variants with reduced sensitivity were observed. The V2 lengths and the V3 sequences exhibited no or minor changes at analysis of sequential NSI isolates. CONCLUSIONS: Our data suggest that NSI isolates obtained from AIDS patients remain CCR5 dependent (ie, R5) and, in many cases, also remain sensitive to RANTES inhibition. However, virus variants with decreased sensitivity to RANTES inhibition may evolve during disease progression, not only as a result of a switch from NSI to SI but also in patients who develop AIDS while continuing to maintain R5 isolates.     

中国HIV-1病毒分离株的生物学特性与疾病进展关系的研究

目的　从HIV AIDS患者应用微量全血法分离中国HIV 1毒株 ,研究HIV 1的生物学特性与HIV AIDS疾病进展相关性。方法　建立微量全血法 ,从HIV AIDS全血标本中分离 17株HIV 1病毒分离株 ;检测这 17株病毒分离株嗜性和复制动力。结果　从 2 6例HIV AIDS病例中分离出HIV 1病毒 ,分离率为 6 5 .4 % (17 2 6 ) ,其中 17例HIV 1感染者的病毒分离率为 5 2 .9% (9 17) ,均为巨噬细胞嗜性 (M嗜性 ,NSI) ;9例AIDS患者的HIV 1病毒分离率为 88.9% (8 9) ,其中 7株为T细胞嗜性 (T嗜性 ,SI) ,1株为巨噬细胞嗜性。通过检测P2 4抗原确定 17株HIV 1病毒分离株的复制动力。在分离到的 17株HIV 1中 ,SI型病毒分离株与AIDS组显著相关 (P <0 .0 5 ) ;AIDS期的病毒分离株的复制动力明显高于HIV感染期 (P <0 .0 5 )。结论　微量全血法可用于病毒分离。 17株分离株的HIV 1复制动力与CD4 + T淋巴细胞计数呈线性负相关 ,与病毒载量呈正相关。     

Virologic,immunologic, and clinical follow-up of a couple infected by the human immunodeficiency virus type one,group O

The pathogenic course (virologic, immunologic, and clinical changes) of infection due to human immunodeficiency virus type one (HIV-1) group O viruses is unknown at present. To address this issue, serial HIV-1 isolates from a married couple (patients A and B) infected with a group O virus were analyzed to determine the temporal association between disease status and alterations in several parameters including plasma viral burden as measured by semiquantitative polymerase chain reaction, changes in CD4+ T cells, presence of neutralizing antibodies, and the ability to induce syncytia on the MT2 cells. For patient A who has been asymptomatic for at least 8 years, both the absence of syncytium-inducing (SI) variants and the presence of autologous and heterologous neutralizing antibodies correlated with a clinically healthier status. In contrast, a switch from NSI to SI variants was observed in patient B in 1990, followed by an expanded in vitro host range, increased viral burden, and a sharp decrease in CD4+ T cells 4 years later. Moreover, plasma obtained from this patient uniformly failed to neutralize both autologous and heterologous viruses. These observations in patient B correlated with a slightly unfavorable clinical status. Based on our preliminary results, it appears that the pathogenic course of infections due to group O viruses is similar to that reported previously for infections due to group M viruses. J. Med. Virol. 51:202–209, 1997. © 1997 Wiley-Liss, Inc.     

Role of HIV-1 phenotype in viral pathogenesis and its relation to viral load and CD4+ T-cell count

The predictive value of HIV-1 phenotype in peripheral blood mononuclear cell (PBMC) coculture and the relation among viral phenotype, viral load, and CD4+ T-cell count were examined in two studies. In study A, 132 HIV-1–infected individuals were examined retrospectively for the relation between the result of their initial HIV cultivation in PBMC coculture and survival rate 6 years later. In study B, 176 patients were examined since 1994 for markers of HIV disease progression. HIV-1 phenotype was determined by PBMC cocultivation, viral load by NASBA HIV RNA QT System, and CD4+ T-cell count by flow cytometry. In study A, the percentage of survival for patients with initial negative virus culture was significantly higher (95%) than in patients with nonsyncytia-inducing (NSI) isolates (78%) and syncytia-inducing (SI) isolates (21%) (P < 0.05 and P < 0.0001, respectively). When SI phenotype was subdivided into moderately cytopathogenic and highly cytopathogenic, significant differences in the rate of survival between these subgroups could be observed (45% vs. 14%; P < 0.05). In study B, progression from negative virus culture to the isolation of NSI variants was associated with increasing viral load (P < 0.0001) but did not affect CD4+ T-cell count significantly (P > 0.07), whereas the switch from NSI to SI virus was accompanied by significant decline of CD4+ T-cells (P < 0.0001) but no change in viral load (P > 0.21). Thus, isolation and phenotyping of HIV represents an additional striking predictive marker for progression of HIV infection. J. Med. Virol. 56:259–263, 1998. © 1998 Wiley-Liss, Inc.     

Replication capacity,biological phenotype,and drug resistance of HIV strains isolated from patients failing antiretroviral therapy

The fitness of human immunodeficiency virus (HIV) in vivo depends on the interaction of a multitude of viral and host factors. The aim of this study was to analyze the biological phenotype and the intrinsic capacity of the HIV isolates with drug-resistance mutations to replicate efficiently in the absence of drugs. An open label multicenter cross-sectional study was undertaken on 28 HIV-infected patients failing antiretroviral treatment. The subjects were studied for CD4+ cell count, HIV viral load, syncytium-inducing phenotype, genotypic drug-resistance assay, and replication capacity of HIV isolates assessed by co-culture assay. All HIV isolates showed a decreased replication capacity compared with wild-type strains. The lowest replication capacity was detected in HIV strains with more than five drug-resistance mutations. The highest replication capacity was observed in strains carrying the K103N and Y181C primary mutations that emerged after treatment with non-nucleoside analogue inhibitors. Isolates with R5 biological phenotype had a higher number of resistant mutations than X4 isolates (P = 0.004). Particularly, the R5 phenotype was detected in all 6 isolates with more than 14 drug-resistance mutations. Patients with R5 strains had plasma viral load similar to patients with X4 strains, but marginally higher CD4+ cell counts, and their HIV isolates had significantly lower replication capacity of HIV isolates (P = 0.008). No patient carrying HIV with a maintained replication capacity had a viral load less than 30,000 copies/ml. In patients failing HAART, the detection of HIV isolates with the R5 biological phenotype correlates with CD4+ cell count, an impaired replication capacity, and a high number of drug-resistance mutations.     

The HIV-2 genotype and the HIV-1 syncytium-inducing phenotype are associated with a lower virus replication in dendritic cells

During sexual transmission, HIV infects the mucosal dendritic cells and is transferred to CD4 T cells. Whether HIV variants of a particular genetic (sub)type or phenotype selectively infect dendritic cells (DC) or are preferentially transferred to T cells remains highly controversial. To avoid the cumbersome use of primary dendritic cells, in vitro dendritic cell models were generated from precursors, either hematopoietic progenitor cells (HPC) or monocytes (MO). Productive infection in the dendritic cells and transfer of the virus to T cells was assessed for a range of HIV variants. HPC-derived dendritic cells (HPC-DC) were more susceptible to HIV-1 than to HIV-2 isolates. The HIV-1 group O strains were more productive in HPC-DC than group M, but amongst the latter, no subtype-related difference was observed. Both non-syncytium-inducing (NSI) and SI HIV isolates and lab strains could productively infect HPC-DC, albeit with a different efficiency. Adding blocking antibodies confirmed that both CCR-5 and CXCR-4 co-receptors were functional. Biological HIV-1 clones of the NSI/R5 phenotype infected more readily HPC-DC than SI/X4 clones. MO-derived dendritic cells were, however, more exclusive in their preference for NSI/R5 clones. Some HIV variants, that did not grow readily in HPC-DC alone, could be rescued by adding resting or pre-activated T cells. The present data show that HIV-2 isolates and SI clones replicate less in model-DC, but no preference for a particular HIV-1 subtype was evident. Co-culture with T cells could "correct" a limited growth in dendritic cells. Clearly, both intrinsic dendritic cell susceptibility and enhancement by T cells are explained only partly by HIV genotype and phenotype. The in vitro dendritic cell models seem useful tools to further unravel interactions between HIV, DC, and T cells.     

Indian primary HIV-2 isolates and relationship between V3 genotype, biological phenotype and coreceptor usage

The chemokine coreceptors play a significant role in HIV entry and pathogenesis. The V3 region of HIV envelope glycoprotein is considered as a principal determinant for viral phenotype and tropism. The present study describes lack of association between the V3 genotype and viral phenotype of 18 Indian HIV-2 isolates. The viruses were isolated, confirmed by PCR and the HIV subtypes were determined by sequencing V3 region of the env gene. The coreceptor usage and syncytium inducing (SI) capacity of isolates was determined. Our study indicated that CCR5 coreceptor usage and NSI phenotype is predominant among Indian HIV-2 isolates obtained from patients in the early stage of infection. Two of the four HIV-2 isolates obtained from the late stage patients were SI and dual tropic. Phylogenetic analysis of these isolates revealed close relatedness to the isolates from western and southern India.     

Performance of immunologic responses in predicting viral load suppression: implications for monitoring patients in resource-limited settings

BACKGROUND: World Health Organization (WHO) guidelines for the use of antiretroviral therapy (ART) in resource-limited settings state that CD4 cell counts may be used to indicate when ART regimens should be changed because of treatment failure. The performance of immunologic monitoring for this purpose has not been evaluated, however. METHODS: Participants aged > or =18 years from the British Columbia HIV/AIDS Drug Treatment Program who had CD4 cell counts < or =200 cells/microL or an AIDS diagnosis at baseline had CD4 cell counts measured at 6 and 12 months after treatment initiation. Logistic regression analysis was used to calculate sensitivity, specificity, and positive and negative predictive values for immunologic responses in terms of predicting failure to achieve 2 viral load measurements < 500 copies/mL within 1 year. RESULTS: Viral load suppression occurred in 674 (60%) of 1125 subjects. Using no increase in CD4 cell counts at 6 months as a definition of treatment failure had a sensitivity of 34%, specificity of 94%, positive predictive value of 75%, and negative predictive value of 71% for predicting failure to achieve virologic suppression. Using 12-month CD4 cell count values, the measurements were 35%, 95%, 79%, and 73%, respectively. CONCLUSION: Immunologic criteria to predict which patients have not achieved virologic suppression results in significant misclassification of therapeutic responses.     

Enhancing of anti-viral activity against HIV-1 by stimulation of CD8+ T cells with thymic peptides.

HIV-1 can be neutralized by soluble factors produced and secreted by activated CD8+ T cells. Production of such anti-viral CD8 factors (including chemokines) can be induced with IL-2 or phytohaemagglutinin (PHA). In addition to PHA or IL-2, we have co-stimulated CD8+ T cells with PHA/IL-2 and a mixture of thymic peptides (TP) of molecular weights below 10 kD. For the activation, CD8+ T cells were purified from peripheral blood mononuclear cells of HIV-1- individuals and any resultant anti-viral activity was monitored using an HIV-1 neutralization assay. Using HIV-1 isolates highly resistant to chemokine inhibition we detected significantly higher levels of HIV-1 neutralizing activity in CD8+ T cell culture supernatants which had been co-activated with TP. When the TP-induced anti-viral activity was monitored, neutralization of both non-syncytia-inducing (NSI) and syncytia-inducing (SI) patient isolates was enhanced by 38% (NSI, PHA +/- TP), 66% (SI, PHA +/- TP), 28% (NSI, IL-2 +/- TP), and 57% (SI, IL-2 +/- TP) compared with the anti-viral activity present in supernatants from CD8+ T cell cultures stimulated only with PHA or IL-2. Peptide sequence analysis of purified TP showed that the TP mixture predominantly contains peptides with homology to human histone and collagen sequences. Our data demonstrate that CD8+ T cells are additionally activated by a mixture of TP. In this way, the production of HIV-1 neutralizing CD8 factors can be enhanced.     

Co-receptor usage was more predictive than NSI/SI phenotype for HIV replication in macrophages: is NSI/SI phenotyping sufficient?

A monocyte-derived macrophage (MDM) culture assay was used to define the replication kinetics of HIV isolates. Ten-day-old MDMs were infected with HIV. Supernatants were collected and assayed for HIV p24 on days 3, 7, 10, and 14 post-infection (PI). In this assay, SF162 (macrophage tropic, NSI) produced increasing amounts of HIV p24 antigen with increasing time in culture. BRU (nonmacrophage tropic, SI) infection resulted in low levels of HIV p24 antigen with no increase in production during the culture period. A panel of 12 clinical isolates was evaluated. All isolates produced detectable levels of HIV p24 antigen in MDMs. However, the NSI viruses had significantly higher log10 HIV p24 antigen values at all times PI (P < 0.01). Co-receptor usage was determined for all 12 isolates (8 NSI and 4 SI). All SI isolates used CXCR4 for entry; two used CXCR4 only, one used CXCR4, CCR5, and CCR3, and one was a mixture of two isolates using CXCR4 and CCR5. None of the NSI viruses used CXCR4 for entry. All used CCR5 as their predominant co-receptor. Of the eight NSI isolates, three used CCR5 only, two used CCR5 and CCR2b, one used CCR5 and CCR3, and one used CCR5, CCR3, and CCR2b. Log10 HIV p24 antigen production on day 14 PI for viruses that used CCR5+CCR3 (3.79 + 1.40) was greater than for viruses that used CCR5+CCR2b (3.22 + 1.55) or CCR5 (3.32 + 1.49), and all were greater than those that used CXCR4 only (1.69 + 0.28), regardless of SI phenotype (P < 0.05). Thus, in these primary isolates, macrophage tropism and replication kinetics were closely linked to CCR5 utilization, whereas SI capacity was closely linked to CXCR4 utilization. Furthermore, viruses, which could use CCR5 and CCR3 for entry, had a replication advantage in macrophages, regardless of SI phenotype.     

It is safe to stop antiretroviral therapy in patients with preantiretroviral CD4 cell counts >250 cells/microL

OBJECTIVE: To study clinical, immunologic, and virologic outcomes in patients who stop antiretroviral therapy (ART) with relatively preserved CD4 cell counts. DESIGN AND METHODS: Patients with a documented CD4 cell count >250 cells/microL who stopped ART for any reason for at least 5 weeks were studied. Relevant clinical and laboratory data were collected using a standardized data collection form. MAIN OUTCOME MEASURES: Patients were monitored for outcomes including Centers for Disease Control (CDC) category B or C events, time to restarting ART, and time to reaching a CD4 cell count of < or = 250 cells/microL. RESULTS: A total of 107 patients were included. The median time on ART was 45 months and median number of antiretroviral medications was 4. The median pre-ART CD4 cell count and HIV viral load were 463 cells/microL and 4.35 log copies/mL, respectively. The median CD4 cell at time of ART stop was 739 cell/microL. The slope of the CD4 decrease was 65 cells/mo in the first 2 months, which was greater than the subsequent decline of 8 cells/mo thereafter (P < 0.01). Similarly the median viral load increase was 2.54 log copies/mL in the first 2 months after stopping and was unchanged after that point. Two patients experienced the retroviral rebound syndrome after ART cessation but no CDC category B or C events were observed during 10 months of follow-up. The median time from stopping ART to reaching the combined endpoint of CD4 <250 or restarting ART was 8.9 months. In multivariate analysis, pre-ART CD4 cell count >250 was protective of reaching the combined endpoint (odds ratio = 0.156, P = 0.03). Other predictors of reaching the combined endpoint in multivariate analysis were older age and number of prior ART agents. Patients who restarted ART had a favorable virologic and immunologic response. CONCLUSIONS: Patients with relatively high CD4 cell counts prior to starting ART did well after stopping ART. Pre-ART CD4 cell count can be used to predict outcomes after ART cessation.     

Safe treatment interruptions in patients with nadir CD4 counts of more than 350 cells/microL: a randomized trial

OBJECTIVE: To evaluate clinical, immunologic, and virologic performance of patients with nadir CD4 counts of >350 cells/microL upon treatment interruption. DESIGN: Randomized, open-label clinical trial of 48 weeks' duration. METHODS: Patients on effective highly active antiretroviral therapy, with nadir CD4 counts of >350 cells/microL and peak viral loads of <50,000 copies/mL were randomized to continue therapy or to interrupt antiretroviral medication. End points for patients with treatment interruption were CD4 counts of <350 cells/microL, viral loads of >1 log above the pretherapy values, or clinical symptoms attributable to HIV, at which point treatment was restarted. In the continuation group, the end points were virologic failure, opportunistic infections, and treatment discontinuation due to toxicities. RESULTS: Twenty patients were randomized to stop therapy and 16 patients to continue. Median CD4 counts at baseline were 643 cells/microL for the interruption group and 633 cells/microL for the continuation group. No end points were reached in the interruption group. By week 8, viral load returned to values comparable to those of pretherapy in all patients in the interruption group and remained stable until week 48. CD4 counts dropped in the interruption group (median loss of 156 cells/microL) at week 48. Significant decreases in venous lactate were observed in the interruption group. CONCLUSIONS: Treatment interruptions in patients with nadir CD4 counts of >350 cells/microL seem safe for at least 48 weeks. Pretherapy viral load appears as a valuable tool to predict its level at week 48.     

Genotypic and phenotypic analysis of the env gene from South African HIV-1 subtype B and C isolates

The objective of the study was to assess the genotypic and phenotypic properties of 18 viral strains from human immunodeficiency virus-1 (HIV-1) positive patients and to identify subtype C isolates for vaccine design strategies. All the isolates were non-syncytium-inducing (NSI) in both the primary and MT-2 cell cultures. The amino acid charge of the V3 loop correlated with the NSI phenotype of the strains. The V3 competitive peptide enzyme immunoassay and DNA sequencing of the partial gp120 region gave concordant results on the 15 subtype C strains, whereas the three B genotypes gave a positive to B, a nonreactive to B, and a dual reaction to the B-D peptides, respectively. Sixteen of the isolates used only CCR5 as coreceptor whereas two isolates made use of additional coreceptors including CXCR4. In summary, all our subtype C isolates are NSI phenotypically and almost all of them use CCR5 exclusively as their coreceptor.     

A pilot trial of indinavir, ritonavir, didanosine, and lamivudine in a once-daily four-drug regimen for HIV infection.

OBJECTIVE: To evaluate the tolerance, pharmacokinetics, and virologic and immunologic outcomes of once-daily indinavir, ritonavir, didanosine, and lamivudine in HIV-seropositive individuals. DESIGN: Open-label 24-week pilot study. PATIENTS: Ten HIV-seropositive subjects who were either antiretroviral-naive or minimally experienced with short-term single-or dual-nucleoside therapy provided informed consent and were enrolled. All subjects received didanosine (400 mg) 30 to 60 minutes before a meal followed by indinavir (1200 mg), ritonavir (400 mg), and lamivudine (300 mg) concurrent with the aforementioned meal. METHODS: Safety laboratory tests, including a complete blood cell count and amylase, lipase, liver transaminase, and nonfasting lipid monitoring as well as plasma HIV viral load and CD4+ lymphocyte count, were carried out at monthly intervals. Genotyping was performed at baseline. Pharmacokinetic studies for indinavir and ritonavir were performed at week 8. RESULTS: Nine of 10 subjects completed 24 weeks of therapy. No subject demonstrated primary protease inhibitor mutations at baseline. Toxicities experienced by subjects were typically mild and consistent with those commonly reported for each of the medications, including two cases of hematuria. By week 24, median nonfasting cholesterol and triglyceride levels increased by 49% and 108%, respectively. Median baseline plasma HIV viral load and CD4+ lymphocyte count were 29,292 (4.47 log10) copies/ml and 224 cells/mm3, respectively. Eight of 10 subjects had a plasma HIV viral load of <50 copies/ml by week 12. The 2 subjects with a detectable HIV viral load reached <50 copies/ml by week 28. Median CD4+ lymphocyte counts increased by 193 cells/mm3 at week 24. Indinavir and ritonavir plasma concentrations remained above respective inhibitory and effective concentrations (IC95 and EC50) (uncorrected for protein binding) throughout the 24-hour dosing interval for 6 of 10 and 8 of 10 subjects, respectively. CONCLUSIONS: Our pilot study demonstrates excellent virologic suppression despite low minimum protease inhibitor concentrations during a dosing interval in some patients and is supportive of further study.     

The role of resistance characteristics of viral strains in the prediction of the response to antiretroviral therapy in HIV infection

OBJECTIVE: To study the role of resistance characteristics of viral mutants in the prediction of virologic and immunologic response to antiretroviral therapy in HIV-infection. METHODS: This study is based on a mathematical model that generates viral and immunologic dynamics of HIV infection, taking into account drug-resistant mutants and therapy. We analyzed predictive factors of the increase in CD4 cell count and of the decrease in viral load from baseline after 6 months of HAART on a sample of 300 simulated individuals. The set of potential predictors was constituted by patients' state at initiation of therapy and by resistance characteristics of viral strains at that time. Predictive models, obtained by stepwise regression, were selected and compared using Mallows' Cp criterion. RESULTS: In addition to baseline viral load and CD4 cell count, known to influence response to therapy, baseline CD8 cell count and resistance characteristics of detectable strains are shown to improve the accuracy of the prediction. On the contrary, resistance parameters of low frequency viral mutants have no predictive value. CONCLUSIONS: Characteristics of preexisting detectable resistant mutants as determinants of virologic and immunologic response to antiretroviral therapy increase the capacity to predict the outcome of the treatment. Therefore, the use of phenotypic and genotypic testing could be crucial and should be considered for the choice of therapy.