Pulmonary Function in HIV-1 Vertically Infected Children

Pulmonary Function in HIV-1 Vertically Infected Children Amandine Rubio1, Fabrice Monpoux2*, Carole Bailly3,4, Dominique Crenesse4 and Marc Albertini3,4 1Clinique Universitaire de Pédiatrie, Hôpital Couple Enfant, CHU de Grenoble, 38043 GRENOBLE cedex 09, France 2Service d’hematologie-oncologie infantile, GCS Pédiatrique CHU-Lenval, Hopital de l’Archet, 151 route de Saint Antoine de Ginestiere, 06202 NICE Cedex 3, France 3Service de Médecine Infantile, France 4Service de Physiologie et Explorations fonctionnelles, GCS Pédiatrique CHU-Lenval, Hôpital pour enfants Lenval, 57 Avenue de la Californie, 06200 NICE, France


Introduction
Pulmonary complications have been a major cause of morbidity and mortality in children with HIV infection [1]. Before the introduction of highly active antiretroviral therapy (HAART), opportunistic pulmonary infections, mainly Pneumocystis jiroveci (carinii) pneumonia and, to a lesser extent, Streptococus pneumoniae pneumonia, were frequent, potentially lethal complications [1][2][3][4]. Introduction of HAART in the mid-eighties and improvements in prophylaxis resulted in an impressive decrease of their incidence [2][3][4]. Besides infections, pulmonary complications include a large number of clinical and radiological conditions in which the lung immune system plays a central role, such as lymphocytic interstitial pneumonia (LIP) or immune reconstitution inflammatory syndrome (IRIS) [1,4]. In the pre-HAART era, HIVinfected subjects had a high prevalence of respiratory complaints [5] and HIV infection was associated with accelerated development of emphysema, airway obstruction, reduced diffusing capacity for carbon monoxide and airway hyperresponsiveness [6][7][8][9].
Since the development of effective ART, obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease, are becoming a growing concern in this population [9][10][11][12]. Recent studies demonstrated that 31 to 64% of HIV-infected adults have respiratory symptoms with up to 20% of airway obstruction determined by spirometry [13,14], and 20% of doctor-diagnosed asthma [15]. Likewise, a greater incidence of asthma was reported in HIV-infected versus noninfected children [16,17]. Foster et al. reported an association between HAART treatment and asthma-medication use in HIV-infected children [18]. However, we did not find any data regarding pulmonary function testing in the HAART era in HIV-infected children in the literature.
forced expiratory volume in one second: FEV 1 and forced expiratory flow during the middle half of FVC: FEF  ) and carbon monoxide diffusing capacity (TL CO ) using the single breath-hold method. Measurements were performed with a water-sealed spirometer Sensormedics 2400-Viasys (Cardinal Health Inc., Dublin, OH, USA) in accordance with international criteria [19][20][21]. Results were expressed as raw values and percentages of predicted values according to the anthropometric data of each patient. PFT measurements were compared to a cohort of age, height, weight and gender-matched healthy children. Comparisons of qualitative parameters were done with the Fisher's exact test. Correlations between quantitative values used regression model. Adjusted R squared values (adjusted R 2 ) are furnished. Quantitative results between sub-groups of patients were compared with the Mann-Whitney-U-test. All statistical analyses were performed using Statview® software 5.0 for Windows (SAS Institute, Cary, NC, USA). p values below 0.05 are considered to indicate statistical significance.

Results
Seventeen HIV-1 chronically infected children were included: 12 girls and 5 boys, with a mean age of 14.9 ± 2.4 years (range: 10.8-18.3) ( Table 1). Nine were HIV stage N/A, 3 were stage B and 5 suffered from AIDS definition illness. None of the children suffered from acute or chronic respiratory disease or had any respiratory symptoms determined by respiratory questionnaire and clinical examination. Mean CD4 T-cell count at inclusion was 820 ± 301 cells/mm 3 (range: 313-1,254) or 35 ± 10% (range: . Mean viral load was 1.79 ± 0.85 log 10 copies/mm 3 (range: 1.3-4.0). Twelve children had undetectable viral load. Each child had been exposed to an average of 6 ± 3 (range: 2-11) antiretroviral drugs since birth. At the time of enrolment, 4 patients received HAART with two nucleoside reverse transcriptase inhibitors (NRTI) and 1 protease inhibitor (PI), 11 received 2 NRTIs + 1 non nucleoside reverse transcriptase inhibitor (NNRTI), 1 was on PI monotherapy, and 1 was receiving 1 drug of each class (NRTI + NNRTI + PI).
When compared with matched healthy children, the only difference was the FEV1/FVC ratio that was significantly lower in the patients' group (91.9% of predicted value versus 97.1%, p<0.0001) (Tables 1  and 2). Furthermore, although FEF 25-75 values were similar in the two groups, we observed that this parameter increased with age and weight in healthy children (p=0.006 and p=0.007 respectively), as was reported by Neukirch et al. [22], but not in infected patients ( Figure 2).

Discussion
Our data shows that in vertically HIV-1 infected non-smoking adolescents, PFT values are in normal ranges, with a high prevalence of sub-clinical mild and reversible basal obstructive ventilatory impairment, as was observed in adult patients [9,10,14]. Similarly, in 1997 de Martino et al. published that children with perinatally acquired HIV-1 infection had higher airway resistance than matched controls, and that resistance decreased with age in the latter but not in infected patients [23]. We also observed that TL CO analysis, which is a measure of gas exchange potential [24], demonstrated a strong correlation with the CD4/CD8 T-cell ratio and viral replication. In the mid-nineties, decreases in the TL CO were described in patients with infectious lung disease, mainly Pneumocystis pneumonia [9][10][11][12]. In 1995, Rosen et al. published that advanced HIV infection, characterized by CD4 count < 200/mm 3 or HIV-associated symptoms, were all associated with reductions in TL CO measurements [9]. Conversely, Nieman et al. showed that patients with reduced TL CO progressed more rapidly to AIDS [11]. TL CO reduction may result from two main mechanisms: diffuse alveolar destruction (as observed in Pneumocystis pneumonia, pulmonary hypertension or fibrosis) or a decrease in alveolar expansion (as observed in neuromuscular disease) [24]. Patients with HIV infection receiving HAART may potentially suffer from each of these two mechanisms.
Recent data supported the fact that in adult patients, the use of HAART is independently associated with a decrease in FEV1/FVC after controlling for other independent risk factors such as age, cigarette smoking, intra venous drug use or previous pneumonia [14,15]. In our population, we also found a significantly lower FEV1/FVC ratio in our patients than in controls. Foster et al. suggested that the increased incidence of asthma in HAART-treated HIV-infected children may be driven by immunoreconstitution of CD4 T-cells [18]. They indeed   showed that HIV+ HAART-treated children had the same cumulative incidence of asthma (around 30% by the age of 13) as non-infected children, whereas HIV-positive untreated children (who had lower CD4 and higher CD8 T cell percentages) had a thrice-lower incidence of asthma. This is indeed supported by the notion that CD4 T-cells are essential for the development of asthma in animal models [25,26]. Likewise, Gutin and Secord reported that the onset of asthma in HIVinfected children most frequently occurred within 3 years of beginning HAART [27]. Despite the fact that our patients were HAART-treated, none had developed asthma, and we did not find a significant relationship between FEV1 or FEV1/FVC and CD4+ or CD8+ T-cell counts or percentages in our patients. This could be explained by the relatively small sample size of our population.
We found however evidence of small-diameter bronchi obstruction (reduction in FEF  in 4/17 of our patients), and a positive correlation between plasmatic CD4/CD8 ratio and FEF  . It is possible that in pediatric patients, alterations of FEF 25-75 may reflect or precede those observed in adult larger bronchi. Unfortunately none of our patients underwent broncho-alveolar liquid fluid (BALF) analysis or high resolution CT-scan. But even if the blood immuno-virological status does not reflect the exact events arising at the alveolar level, it is possible that our results reflect a particular response of the lungs to infection. In 1997 Lipman et al. compared BALF analysis (cells and cytokine levels) from HIV-1 infected patients with pneumonia and HIV-1 positive individuals with no respiratory disease to healthy controls and showed that alteration of the potential relevance to the pulmonary immune response are occurring in alveolar macrophages prior to the onset of respiratory disease [28]. Actual evidence for pulmonary tissue-level effects of HIV is conflicting. Alveolar macrophages and dendritic cells within the lung are targets for HIV infection and become increasingly infected as HIV infection progresses [3]. We recently showed that children's response to HAART is nowadays similar to that of adults with approximately 80% achieving an undetectable viral load and a good immunological response [29]. It is likely that with HAART, the plasmatic viral load decrease is associated with a reduction in the overall HIV lung concentration.     Altogether, the mechanistic link between HAART and airway obstruction is not precisely known. Potential explanations include: a) direct effects of HAART in the lung; b) chronic stimulation of inflammation induced by restoration of the immune system, with the release by CD8+ T-cells of inflammatory cytokines known to be implicated in airway inflammation [15]; c) the development of a hyperallergic state [16], as was shown by a higher sputum eosinophil count [15]; d) and/or the development of autoimmunity.
Although evidence of airway obstruction was small in our vertically HIV-infected HAART-treated pediatric population, these subjects face a lifetime of antiretroviral treatment and may be at risk of developing clinically significant disease as they age. Smoking avoidance, routine influenza and pneumococcal vaccinations and careful pulmonary follow-up must therefore be combined to decrease the risk of respiratory symptoms and airway obstruction in these patients.