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Effect of Highly Active Antiretroviral Therapy on Viral Burden in the Lungs of HIV-Infected Subjects

  1. Homer L. Twigg III1,
  2. Michael Weiden2,
  3. Fred Valentine2,
  4. Carol T. Schnizlein Bick1,
  5. Roland Bassett3,
  6. Lu Zheng3,
  7. Joseph Wheat1,
  8. Richard B. Day1,
  9. Helen Rominger1,
  10. Ronald G. Collman4,
  11. Lawrence Fox5,
  12. Barbara Brizz6,
  13. Joan Dragavon7,
  14. Robert W. Coombs7 and
  15. R. Pat Bucy8
  1. 1 Division of Pulmonary and Critical Care Medicine and the AIDS Clinical Trials Unit, Indiana University Medical Center, Indianapolis
  2. 2 Divisions of Pulmonary Medicine and Infectious Diseases, New York University Medical Center, New York
  3. 3 Center for Biostatistics in AIDS Research, Harvard School of Public Health, Boston, Massachusetts
  4. 4 Division of Pulmonary, Allergy, and Critical Care Medicine, University of Pennsylvania Medical Center, Philadelphia
  5. 5 HIV Research Branch, National Institute of Allergy and Infectious Diseases, Boston, Massachusetts
  6. 6 Social and Scientific Systems, Silver Spring, Maryland
  7. 7 Department of Laboratory Medicine, University of Washington, Seattle
  8. 8 Department of Pathology, University of Alabama at Birmingham, Birmingham
  1. Reprints or correspondence: Dr. Homer L. Twigg III, Indiana University Medical Center, Richard Roudebush VA Medical Center, 1481 W. 10th St., VA 111P-IU, Indianapolis, IN 46202 (htwig{at}iupui.edu).

  1. Presented in part: American Thoracic Society International Conference, San Diego, May 2005.

 
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Abstract

Background. Human immunodeficiency virus (HIV) is readily detectable in the lungs of infected subjects and leads to an accumulation of CD8+ lymphocytes in the alveolar space. Although highly active antiretroviral therapy (HAART) is effective in reducing viremia, less is known about its effect on tissue compartments. The AIDS Clinical Trials Group Protocol 723 Team evaluated the effect of HAART on lung viral load and cellular constituents.

Methods. Bronchoalveolar lavage (BAL) fluid and blood were collected before initiation of HAART and again at 4 and 24 weeks after initiation of therapy. The BAL cell differential was determined, lymphocyte phenotyping was performed, and acellular BAL fluid, plasma HIV RNA load, and BAL cell and peripheral blood mononuclear cell HIV RNA and DNA loads were measured.

Results. HAART induced a rapid decrease in HIV that was detectable in acellular BAL fluid and a slower decrease in the HIV RNA and DNA loads in BAL cells. HAART was associated with a significant decrease in the absolute number and percentage of CD8+ alveolar lymphocytes. There was a significant correlation between residual BAL cell DNA at 24 weeks and the absolute number of CD4+ lymphocytes in the alveolar space.

Conclusions. HAART is associated with a significant decrease in the pulmonary HIV burden and a return of alveolar cellular constituents to normal.

Pulmonary complications are an important cause of morbidity and mortality in HIV-infected subjects [1,2]. HIV is frequently detected in the lungs of infected individuals and likely is important in the pathogenesis of HIV-related pulmonary disease. Increased susceptibility to infections can be attributed to the effect of HIV on systemic and pulmonary immunity [3]. In contrast, the cause of nonspecific inflammatory reactions in the lung, such as lymphocytic alveolitis, is less clear, but it may be related to the persistence of viral antigens leading to a state of chronic macrophage and lymphocyte activation in the alveolar space. Up to 60% of asymptomatic, treatment-naive, HIV-infected individuals have increased numbers of CD8+ cytotoxic T lymphocytes (CTLs) in the alveolar space [4]. Many of these CTLs are specific for HIV-infected cells [5], suggesting that lymphocytic alveolitis represents an immune response to HIV in the lung. If true, control of HIV in the lungs could restore the pulmonary milieu to a more normal environment.

Highly active antiretroviral therapy (HAART) significantly reduces HIV load in the vascular compartment 6] and in the lymph nodes [7]. However, the effect of HAART on other tissue compartments is largely unexplored. The purpose of the present study was to determine whether HAART resulted in a significant decrease in the pulmonary HIV burden and to assess whether any observed changes in the viral load led to improvement in the alveolar abnormalities found in HIVinfected subjects. We prospectively performed bronchoscopy with bronchoalveolar lavage (BAL) in treatment-naive HIVinfected subjects before initiation of HAART and again at 4 and 24 weeks after the start of therapy. HIV RNA was measured in the acellular lavage, and HIV RNA and DNA were measured in BAL cells. These measurements were compared with similar measurements in blood, to determine the effect of HAART on the pulmonary HIV load and to assess whether the vascular and pulmonary compartments differed in their response to therapy. The effect that HAART had on BAL cell differentials and lymphocyte subsets was also determined.

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Materials and Methods

Subjects and study design. The AIDS Clinical Trials Group Protocol 723 (ACTG 723) was a multicenter, prospective, longitudinal study designed to assess the effect of HAART on pulmonary viral burden and immune function. Protease inhibitor- and nonnucleoside reverse-transcriptase inhibitor-naive HIVinfected subjects who were scheduled to begin receiving HAART (defined as treatment with ⩾3 antiretroviral drugs) were asked to undergo bronchoscopy with BAL before starting therapy (hereafter referred to as “entry bronchoscopy”) and again at 4 and 24 weeks after HAART was initiated. The study was approved by the institutional review board for human research at each participating institution. Even if subjects were participating in other drug trials, written, informed consent specific forACTG 723 was obtained from each subject.

Eligible subjects had confirmed HIV infection, were >18 years of age, and had been free of respiratory tract symptoms in the past 30 days. In addition, subjects had to have a CD4 lymphocyte count of ⩽500 cells/μL and a plasma HIV RNA load of ⩾5000 copies/mL within 30 days before study entry. The latter 2 inclusion criteria were chosen to maximize the likelihood that subjects would have either lymphocytic alveolitis (defined as >15% lymphocytes in total bronchoalveolar cells) or detectable HIV in acellular BAL or BAL cells. One of these findings had to be noted after entry bronchoscopy was performed, for the subject to continue participation in the study.

If subjects met the criteria for continued participation in the study, bronchoscopy was again performed at weeks 4 and 24 after initiation of HAART. If subjects currently had a respiratory tract infection or had experienced such infection in the past 14 days, bronchoscopy was delayed until the subject had been symptom free for 2 weeks. At each time point, blood was also collected for measurement of the plasma viral load, determination of the HIV RNA and DNA loads in peripheral blood mononuclear cells (PBMCs), and measurement of the blood urea nitrogen concentration for determination of epithelial lining fluid in BAL samples as described below.

Experimental procedures. Bronchoscopy with BAL was performed as described elsewhere [8]. Lavage fluid was filtered through sterile gauze, and BAL cells were pelleted by centrifugation. The supernatant was saved as the acellular BAL fraction at -70°C. BAL cells were washed and counted, and cytospins were performed for determination of the cell differential. BAL cells were stained with CD45, CD3, and either CD8 or CD4 monoclonal antibodies (Becton Dickinson) and were analyzed by flow cytometry (FACSCalibur; Becton Dickinson). After gating on CD45+ cells, the percentage and absolute number of CD3+CD4+ and CD3+CD8+ cells were determined. The remaining BAL cells were then resuspended in human AB serum containing 10% dimethyl sulfoxide at a concentration of >5 × 106 cells/mL and were frozen at -70°C. PBMCs were isolated on a ficoll-hypaque gradient and were processed in the same way that BAL cells were processed.

HIV RNA loads were determined in acellular BAL and in plasma by use of UltraSensitive reverse-transcription polymerase chain reaction (Roche Diagnostics). The lower limit of quantitation was 50 copies/mL. Cellular HIV RNA and DNA loads in PBMCs and BAL cells were quantitated as described elsewhere [9]. In brief, cyropreserved cells were thawed and immediately dissolved in guanidinium isothiocyanate solution [10]. Total DNA was extracted using the DNeasy Tissue kit (Qiagen), and total RNA was isolated using the RNeasy minikit (Qiagen). RNA was reversed transcribed using random hexamer priming and the Superscript RNase H-Reverse Transcription kit (Invitrogen). Both DNA and cDNA from the RNA extraction were analyzed using a molecular beacon probe specific for a conserved section of the HIV gag gene [11] by use of the Roche LightCycler instrument [9]. The lower limit of quantitation for RNA was 300 copies/106 cells, and, for DNA, it was 30 copies/106 cells.

BAL urea nitrogen concentrations were measured using a commercially available kit (Urea Nitrogen Kit; Sigma Diagnostics). Along with the plasma urea nitrogen concentration, this concentration allowed calculation of the epithelial lining fluid in each BAL sample [12]. The HIV load in the acellular fraction of BAL was expressed as the number of copies per milliliter of epithelial lining fluid. The amount of HIV RNA and DNA in BAL cells and PBMCs was expressed as the number of copies per 106 cells.

Statistics. The primary virologic end point in both the lung and blood was defined as either a 1-log10 decrease in the viral load (either per milliliter or per 106 cells) or a decrease to a value below the lower limit of quantitation. Subjects for whom data for a parameter were missing at baseline were excluded from analyses involving that parameter. For descriptive analyses, the percentage of subjects with a viral load below the lower limit of quantitation and the percentage of subjects who reached the combined virologic end points at each follow-up point were reported. Because of the large proportions of viral loads found to be below the lower limit of quantitation after entry into the study, the Sign test was used to assess whether there were decreases in viral loads from the baseline value. Comparisons between the lung and vascular compartments were made using χ2 analysis. Both the relationship between the HIV load in blood and the lung and the relationship between residual detectable HIV in the lung and the absolute number of alveolar macrophages and lymphocytes, as well as lymphocyte subsets, in epithelial lining fluid were assessed using Spearman's rank correlation coefficients. Differences in BAL cell differentials over time were analyzed using the Mann-Whitney rank sum test. A decrease in the incidence of lymphocytic alveolitis from baseline was examined using McNemar's test. P ⩽ .05 was considered to be statistically significant.

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Results

Participation and follow-up. Thirty male and 10 female subjects were enrolled in the study. The median age of the subjects was 38 years, the median plasma HIV load at baseline was 75,000 copies/mL, and the median CD4 cell count at baseline was 203 cells/μL. A total of 69% of the subjects were smokers. Of the 40 subjects enrolled in the study, 2 did not meet criteria for continuing participation in the study after entry bronchoscopy was performed, and 1 was too difficult to sedate; all 3 of these patients were withdrawn from the study. The remaining 37 subjects were eligible for bronchoscopy at weeks 4 and 24 and are the study population for this work. Of these 37 subjects, 33 underwent a follow-up procedure at week 4, and 29 had data from study entry and from weeks 4 and 24 available for analysis. There was no difference in the CD4 cell count or plasma viral load noted at baseline, when the 29 subjects who completed the study were compared with the 8 subjects who did not. The bronchoscopy performed at week 4 was conducted at a median of 34 days after initiation of HAART. Bronchoscopies performed at week 24 were conducted a median of 168 days after initiation of HAART.

Effect of HAART on blood and lung HIV-I burdens. As expected, HAART was associated with a significant decrease in the plasma viral load (figure 1A). By week 24 after initiation of HAART, 50% of subjects had plasma viral loads below the lower limit of quantitation, and 82% had reached the combined end point of either a 1-log10 decrease in the plasma viral load or undetectable levels. These data demonstrate that the subjects forming the lung study population were truly receiving HAART, and they suggest that the subjects had good compliance with their medical regimens.

Figure 1.
Figure 1.

Effect of highly active antiretroviral therapy (HAART) on the plasma HIV load, peripheral blood mononuclear cell (PBMC) HIV RNA load, and PBMC HIV DNA load. Blood was obtained before initiation of HAART and again at weeks 4 and 24 after initiation of therapy. Black bars denote the median viral loads for the population at the designated time point. HAART induced a rapid and significant decrease in the plasma viral load (n = 33 subjects) (A), the PBMC HIV RNA load (n = 32 subjects) (B), and the PBMC HIV DNA load (n = 32 subjects) (C). Data were analyzed using the Sign test. *P <.0001; +P values between P = .0001 and P < .005.

The data on the HIV RNA and DNA loads in PBMCs are1 shown in figure 1B and 1C, respectively. At 24 weeks, only 28% of the subjects had HIV RNA loads in PBMCs that were below the lower limit of quantitation, and only 48% had HIV DNA levels that were below the lower limit of quantitation. Although decreases in viral loads in PBMCs were less dramatic than those in plasma, the changes from baseline were still significant for HIV RNA (P < .0001) and HIV DNA (P = .001).

Changes in the lung compartment are shown in figure 2. The numbers of viral copies per milliliter of BAL fluid were converted to the number of viral copies per milliliter of epithelial lining fluid, to account for dilution during bronchoscopy [12]. On the basis of dilution calculations, the lower limit of detection for epithelial lining fluid in figure 2A was 1500 copies/mL. At entry, 86% of subjects had detectable HIV in epithelial lining fluid (figure 2A). By 4 weeks after initiation of HAART, 82% of subjects had viral loads in the epithelial lining fluid that were below the lower limit of quantitation, and 91% had reached the combined end point of having either a 1-log10 decrease in the BAL viral load or levels below the lower limit of quantitation. The corresponding percentages of subjects noted at 24 weeks were both 86%. The decreases in HIV RNA loads in epithelial lining fluid at weeks 4 and 24 after initiation of HAART were highly significant (P < .0001). The data on the HIV RNA and DNA loads in BAL cells are shown in figure 2B and 2C, respectively. At 24 weeks, 83% of subjects had HIV RNA loads in BAL cells that were below the lower limit of quantitation, and 70% had HIV DNA levels below the lower limit of quantitation. The decreases from baseline in the HIV RNA loads in BAL cells (P < .0001) and in the HIV DNA loads in BAL cells (P < .001) were highly significant.

Figure 2.
Figure 2.

Effect of highly active antiretroviral therapy (HAART) on the lung epithelial lining fluid (ELF) HIV load, the bronchoalveolar lavage (BAL) cell HIV RNA load, and the BAL cell HIV DNA load. Bronchoscopy with BAL was performed on 33 subjects before initiation of HAART and again at weeks 4 and 24 after initiation of therapy. Acellular BAL viral loads were converted to the number of viral copies per milliliter of ELF. Black bars denote the median viral loads for the population at the designated time point. HAART induced a rapid and sustained decrease in the amount of HIV detectable in acellular ELF (A), BAL cell HIV RNA (B), and BAL cell HIV DNA (C). Data were analyzed using the Sign test. *P < .0001; +P values between P = .0001 and P < .005.

At baseline, the ability to detect HIV in the lung and vascular compartments was similar (table 1). After 4 weeks of HAART, the ability to detect HIV in epithelial lining fluid was significantly lower than the ability to detect HIV in plasma, although this finding likely reflects a dilution effect of the lavage procedure on the epithelial lining fluid. There was no difference in the ability to detect HIV RNA and DNA in lung and blood cells. After 6 months of therapy, the ability to detect HIV RNA in lung cells was significantly poorer than the ability to detect HIV RNA in PBMCs. No difference was seen in the ability to detect HIV DNA in cells from both these compartments. Thus, the lung appears to respond to HAART as well as, if not better than, the vascular compartment.

Association between blood and lung HIV loads. At baseline, there was a strong correlation between BAL cell DNA and PBMC DNA (r = 0.45; P = .01) and between BAL cell RNA and PBMC RNA (r = 0.45; P = .01). In contrast, the association between epithelial lining fluid RNA and plasma RNA was not significant. However, the correlation between plasma viral RNA and epithelial lining fluid RNA became significant at week 4 (r = 0.43; P < .01) and week 24 (r = 0.65; P < .001). The association between BAL cell DNA and PBMC DNA remained strong at week 4 (r = 0.80; P < .0001) and week 24 (r = 0.62; P < .001). The association between BAL cell RNA and PBMC RNA was also significant at 4 weeks (r = 0.39; P = .03) and 24 weeks (r = 0.38; P = .04). Thus, after initiation of HAART, there is a significant correlation between the viral load in the vascular and lung compartments. The correlation appears to be strongest for viral DNA.

Effect of HAART on the BAL cell differential. Normal BAL differentials consist of 85%-90% alveolar macrophages and 10%-12% lymphocytes [13]. As expected [4], HIV-infected subjects had an increase in the percentage of alveolar lymphocytes to twice the percentage considered to be normal (figure 3A) and a 4-5-fold increase in the absolute number of lymphocytes (figure 3B). HAART was associated with a significant decrease in the percentage and total number of BAL lymphocytes. Six months after initiation of therapy, the percentage and total number of lymphocytes were comparable to those reported for the normal population [13]. The decrease was caused exclusively by a significant decrease in the number of BAL CD3+CD8+ cells (figure 3C). The number of BAL CD4+ lymphocytes did not change over the duration of the study and remained similar to that reported for the normal population. The decrease in the percentage of lymphocytes was offset by a significant increase in the percentage of alveolar macrophages after HAART. These changes resulted in a significant reduction in the percentage of subjects who had lymphocytic alveolitis (table 2), decreasing from 41% of subjects at the time of entry into the study to 24% at study week 24 (P = .02). In agreement with work published elsewhere [8], lymphocytic alveolitis was more prevalent in subjects with baseline CD4+ cell counts of >200 cells/μL (50% of such subjects), compared with subjects with a CD4+ cell count of <200 cells/μL (29% of such subjects). Also in agreement with the findings of previous studies [14], alveolar lymphocytosis was more severe in nonsmokers than in smokers (mean percentage of alveolar lymphocytes ±SD, 40% ±5% vs. 12% ±4%, respectively). The decrease in the mean percentage (±SD) of alveolar lymphocytes by week 24 was significant in nonsmokers (from 40% ± 5% to 22% ± 5%) but not in smokers (from 12% ± 4% to 8% ± 2%). However, 5 smokers met criteria for lymphocytic alveolitis, and, in these subjects, the mean percentage (±SD) of alveolar lymphocytes did decrease after HAART (from 25% ± 3% to 13% ± 4%). Thus, HAART is associated with a significant reduction in the number of lymphocytes in the alveolar space and a return of the BAL differential toward a measurement considered to be normal.

Figure 3.
Figure 3.

Effect of highly active antiretroviral therapy (HAART) on the bronchoalveolar lavage (BAL) cell differential of 32 subjects. Bronchoscopy with BAL was performed before initiation of HAART and again at weeks 4 and 24 after initiation of therapy. BAL absolute cell counts and the BAL cell differential were determined. HAART was associated with a significant decrease in the percentage (A) and absolute number (B) of alveolar lymphocytes (lymphs) with time. The decrease in lymphs was seen exclusively in the CD8+ cell subset (C). The decrease in the percentage of lymph was offset by a significant increase in the percentage of alveolar macrophages (AM) noted during HAART, returning the BAL cell differential toward normal. Statistical analysis was performed using the Mann-Whitney rank sum test. *P < .01. ELF, epithelial lining fluid; Neut, neutrophil.

Figure 4.
Figure 4.

Correlation between bronchoalveolar lavage (BAL) cell DNA and the absolute number of lymphocytes (n = 28 subjects) (A), alveolar macrophages (n = 28 subjects) (B), and CD4+ and CD8+ lymphocytes (n = 22 subjects) (C) per milliliter of epithelial lining fluid (ELF) after 24 weeks of highly active antiretroviral therapy. At 24 weeks, there was a significant correlation between BAL cell DNA levels and the absolute number of lymphocytes, but not alveolar macrophages, per milliliter of ELF. The correlation between alveolar lymphocytes and BAL cell DNA is confined to the CD4+ lymphocyte subset. Statistical analysis performed using Spearman's rank correlation coefficients.

Table 1.
Table 1.

Comparison of the ability to detect HIV in the lung and blood compartment.

Table 2.
Table 2.

Change in the percentage of subjects with lymphocytic alveolitis before and during receipt of highly active antiretroviral therapy.

Association between the residual pulmonary viral load and the cell count. Finally, we examined the association between the residual viral load in the lung of patients receiving HAART and the number of cells in the alveolar space. At week 24 after initiation of the study, there was a significant correlation between the BAL cell DNA load and the absolute number of lymphocytes—but not alveolar macrophages—in the alveolar space (figure 4A and 4B). Furthermore, this correlation between BAL cell DNA and alveolar lymphocytes was true only for the CD4+ lymphocyte population (figure 4C). There was no correlation between any BAL cell population and BAL cell RNA or epithelial lining fluid RNA at week 24. These data suggest that residual HIV in the lung, when present in patients receiving HAART, resides within the CD4+ lymphocyte population.

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Discussions

In the present study, we demonstrated that, in HIV-infected subjects, HAART induces a significant decrease in the viral load in the alveolar space, both in the acellular and cellular fractions. Concomitant with the decline in the pulmonary viral load, there is a delayed but significant decrease in the absolute number and percentage of alveolar lymphocytes, returning to an alveolar cell differential considered to be normal. This decrease is caused exclusively by a decrease in the absolute number of CD8+ lymphocytes in the alveolar space. Finally, residual HIV in the lung of patients receiving HAART correlates with the absolute number of CD4+ T cells in the lung.

HAART is very effective in reducing the plasma viral load to undetectable levels [6]. The decrease is characterized by a rapid, early exponential phase lasting several weeks, followed by a slower linear phase lasting 2–3 years [15]. This has been interpreted as rapid death of short-lived infected cells, followed by a slower loss of longer-lived cells [15]. Others have suggested that the decrease in viremia is the result of decreased immune activation and improved immune function, resulting in fewer and less intense “viral bursts” [16]. Blood CD4+ T cell recovery inversely parallels the decrease in the plasma viral load, with a rapid increase in CD4+ cell counts occurring in the first 1–2 months, followed by a slower, more sustained recovery over 1–2 years [17,18].

The effect of HAART at the tissue level is less well defined, primarily because different tissue compartments behave differently in response to HIV infection as well as in response to therapy. In lymph nodes, the effect of HAART mirrors that in blood [7] and is associated with decreased cellular proliferation and down-regulation of inflammatory genes [19]. The gastrointestinal tract is very sensitive to HIV infection, with a rapid loss of CD4+ T cells occurring in gut-associated lymphoid tissue (GALT) [20]. Furthermore, HAART-induced suppression of viral replication in GALT in patients with chronic HIV infection is incomplete and is associated with poor CD4+ T cell reconstitution in the gastrointestinal tract [20]. In contrast, our results in a chronically infected HIV cohort demonstrate a significant decrease in acellular and BAL cellular HIV RNA loads in the alveolar space over 6 months. This is associated with a return of the alveolar environment toward normal. These findings highlight the differences in the response to HAART in different tissue compartments.

The source of persistent cellular HIV reservoirs in patients receiving HAART has been attributed to mononuclear phagocytes [21] and long-lived CD4+ lymphocytes [22,23]. Our results suggest that the latter is occurring in the lung, where there was a significant correlation between the absolute number of alveolar CD4+ lymphocytes and BAL cell DNA at 24 weeks after initiation of HAART. This is consistent with the observation that most lung T lymphocytes are long-lived memory cells [24,25]. However, we cannot rule out the possibility that lymphocytes recovered from the alveolar space represent cells that have recently emigrated from the vascular compartment. In fact, the strong correlation between BAL cell HIV DNA and PBMC HIV DNA supports this hypothesis as well.

Changes in the pulmonary viral load could affect the immunologic milieu in the lung. We demonstrate a significant decrease in lung lymphocytes occurring in association with HAART, resulting in a significant decrease in the number of subjects with lymphocytic alveolitis. These results support previous cross-sectional experiments demonstrating a significant correlation between alveolar lymphocytes and the ability to detect HIV in BAL fluid [8]. Because most lymphocytes in the lungs of HIV-infected subjects are CD8+ HIV-specific cytotoxic T cells [5], we speculate that decreasing the pulmonary viral burden reduces the antigenic drive to maintain these cells in the alveolar space. This speculation is strongly supported by the finding that the decrease in lung lymphocytes results primarily from a decline in the CD8+ T cell subset.

The clinical implications of our findings are at least 2-fold. By returning the alveolar environment toward normal, pulmonary immune function may be improved. In the lung, HAART has been associated with decreased numbers of opportunistic infections [26], decreased numbers of mycobacterial infections [27], and a decreased incidence of bacterial pneumonia [28]. This improved immunologic milieu has led to the development of guidelines as to when primary and secondary prophylaxis against opportunistic pathogens can be discontinued [29]. Second, the decrease in the pulmonary viral load and the number of alveolar CD8+ lymphocytes could significantly decrease the incidence of HIV-associated emphysema, a condition postulated to be mediated both directly by the virus and by lung cytotoxic T cells [30,31].

There are limitations to the present study. The HAART regimen was not standardized, so statements about the effectiveness of specific drugs cannot be made. We can only conclude that a medical regimen sufficient to clear virus from the vascular compartment can have similar effects in the lung. Second, although this is one of the largest longitudinal studies of HIV in the lung, it remains relatively small, making subgroup analysis difficult. Third, we studied a well-defined population of HIV-infected subjects characterized by a CD4 lymphocyte count of ⩽500 cells/μL and a plasma HIV RNA load of ⩾5000 copies/mL. These criteria were chosen to maximize the likelihood that we would be able to detect a change in the pulmonary compartment in patients starting HAART. Although these parameters encompass a large percentage of HIV-infected subjects not receiving antiretroviral therapy, they do limit the patient population to which these results apply. Specifically, patients with less advanced disease characterized by higher peripheral blood CD4 cell counts and lower plasma viral loads may have a different pulmonary response to HAART.

In conclusion, HAART induces a rapid decrease in the amount of HIV detectable in the acellular and cellular components of the alveolar space. This is associated with a significant decrease in the percentage and absolute numbers of alveolar CD8+ lymphocytes. In some individuals, HIV remains detectable in the lung 6 months after initiation of HAART, primarily as DNA in BAL CD4+ T cells, suggesting that either long-lived resident memory T cells or recently migrating vascular lymphocytes are the source for persistent HIV in the lung. Whether individuals with significant decreases in the pulmonary HIV load and normalization of the alveolar compartment cell differential realize improvement in pulmonary immunity and better clinical outcomes is currently under investigation.

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AIDS Clinical Trials Group Protocol 723 Team

Other contributors to this work are Janet Forcht and Charles Gonzalez (New York University/Bellevue, New York, New York); Doris Shank (University of Pennsylvania, Philadelphia, Pennsylvania); Jorge L. Santana and Santiago Marrero (University of Puerto Rico, San Juan, Puerto Rico); Scharla Estep (Pharmaceutical Affairs Branch, Division of Acquired Immunodeficiency Syndrome, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland); M. K. Holohan (Social and Scientific Systems, Silver Spring, Maryland); Michele Holody, Janeen Duffy, Ann Walawander, Bernadette Jarocki, and Amanda Zadzilka (Frontier Science and Technology Research Foundation, Amherst, New York); Leslie Thompson (University of Miami School of Medicine, Miami, Florida); and Daniel Kuritzkes (University of Colorado Health Sciences Center, Denver, Colorado).

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Footnotes

  • Potential conflicts of interest: none reported.

  • Financial support: Adult AIDS Clinical Trials Group, funded by the National Institute of Allergy and Infectious Diseases (grant AI 38858); Statistical and Data Analysis Center (grant AI 38855); individual AIDS Clinical Trials Units at Indiana University (grant AI 25859), New York University (grant AI 27665), the University of Alabama at Birmingham (grant AI 32775), the University of Puerto Rico (grant AI 34832), and the University of Washington (grant AI 27664); General Clinical Research Center Awards, funded by the National Center for Research Resources at Indiana University (grant MO1 RR750) and New York University (grant MO1 RR00096); grants RO1 HL59834 (to H.L.T.), HL057879 (to M.W.), and P20 RR11126 (to Jorge L. Santana).

  • a Study group members are listed after the text.

  • Received April 30, 2007.
  • Accepted June 28, 2007.
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  1. J Infect Dis. (2008) 197 (1): 109-116. doi: 10.1086/523766
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