The role of DCs in primary HIV-1 infection remains uncertain. In this study, we enrolled two different groups of subjects with acute HIV-1 infection. One group progressed to CD4 counts below 200 cells/μl within 2 years of HIV-1 infection (CD4 Low Group), while the other group maintained CD4 counts above 500 cells/μl (CD4 High Group). We did not find statistical difference in the pDC number between the two groups during acute HIV-1 infection. However, the mDC number was significantly lower in the CD4 Low Group than in the CD4 High Group.
The online version of this article (doi:10.1186/1742-6405-11-22) contains supplementary material, which is available to authorized users.
Yanmei Jiao, Xin Sun contributed equally to this work.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
YJ drafted the manuscript and statistical analyses. XS participated in flow cytometric analysis. TZ followed up patients and collected samples. XS and XH assisted with manuscript and data anlysis. YJ and WL assisted with flow cytometric analysis and data acquisition. HW conceived the study and participated in the data analysis. HW supervised and coordinated the study. All authors have read and approved the final manuscript.
Introduction
Understanding how the innate immune response affects the outcome of HIV-1 infection in acute HIV-1 infection will open opportunities for vaccine development that can utilize the innate immunity to enhance viral control with minimal pathogenesis. Dendritic cells (DCs) are particularly important innate immune cells and HIV-1 exploits DCs to enhance infection. Thus, DCs are a critical link between virus, CD4+ T-cells, and CD8+ T-cells. DCs are divided into two broad subsets, myeloid (mDC) and plasmacytoid (pDC), based on phenotype, function, and tissue localization. Although details of these subsets are debated and vary based on species, pDCs are specialized early type 1 interferon-secreting cells that initiate antiviral adaptive immune responses. mDCs differentiate from immature bone marrow (BM)-derived precursors and function as peripheral sentinels by transmitting antigen derived signals to draining lymph nodes (LN). mDCs secrete high levels of interleukin-12 (IL-12) and are key players in amplifying adaptive immune responses[1]. Early immune events during HIV infection are associated with the rate of subsequent disease progression. A role for DCs in controlling HIV-1 replication during primary infection has been difficult to assess, given the difficulties in finding individuals with acute HIV infection. The aim of this study is to study the relationship between DCs number in acute infection and disease progression.
Materials and methods
Patients
35 patients recently infected with HIV-1 were recruited from an HIV-1-negative high-risk MSM (men who have sex with men) cohort. They were screened every 2 m for HIV-1 infection from October 2006 in the Beijing You’an Hospital [2]. Thirteen of the 35 patients showed rapid progression of HIV-1 disease, with CD4 counts < 200 cells/ul within 2 y post-infection (CD4 Low Group), while 22/35 cases enrolled in the study maintained a CD4 count higher than 500 cells/ul (CD4 High Group). The progression of early HIV-1 infection can be depicted as six discrete stages, as proposed by Fiebig et al. [3]. All the 35 enrolled patients were in Fiebig stage III. The project was reviewed and approved by the Beijing You’an Hospital Research Ethics Committee, and patients participated in the study following informed consent. Demographic and immunologic characteristics of the patients are reported in Table 1.
Table 1
Characteristics of patients in this study
Patient
Age
Initial CD4 count
Last CD4 count
Initial VL
VL set point
Days from the initial positive point to CD4 < 200 cells/ul
(year)
(cells/ul)
(cells/ul)
(copies/ml)
(copies/ml)
1
22
614
181
1,558
30,800
714
2
23
296
159
8,690
24,600
459
3
23
314
188
53,000
28,400
196
4
25
327
171
110,000
79,600
169
5
26
415
117
392,000
153,600
153
6
26
64
117
26,900,000
714,000
172
7
27
349
153
61,400
61,400
218
8
29
265
118
412,000
393,000
189
9
30
610
72
9,490
7,090
755
10
32
296
145
400,000
26,000
260
11
34
499
69
252,000
776,000
191
12
36
285
53
13,300
13,300
345
13
43
130
195
16,200
11,940
356
14
22
792
605
70,200
662
━
15
23
598
714
34,000
9,700
━
16
23
716
527
14,100
7,210
━
17
24
805
827
56,800
35,900
━
18
24
603
689
16,400
527
━
19
25
552
865
9,170
1,040
━
20
25
716
530
14,900
1,940
━
21
26
678
622
1,440
3,260
━
22
26
823
521
15,000
2,000
━
23
26
805
683
258,000
61,200
━
24
27
640
619
15,500
4,530
━
25
29
716
546
8,780
8,390
━
26
30
813
790
9,700
2,300
━
27
30
745
589
8,260
1,500
━
28
31
823
648
809
200
━
29
32
678
546
18,500
5,200
━
30
32
1148
1056
1,030
554
━
31
34
558
538
26,500
9,700
━
32
34
835
546
10,050
1,890
━
33
37
562
568
27,600
7,960
━
34
38
792
784
70,200
1,312
━
35
40
720
639
6,200
3,320
━
VL: viral load.
Anzeige
Flow cytometric analysis
To identify DCs, the following antibodies from BD Pharmingen (San Diego, CA, USA) were used: Lin-FITC, CD123-PE and CD11c-APC. At least 200,000 events were acquired for each sample. mDCs were identified as Lin-CD123-CD11c+, while pDCs were Lin-CD123 + CD11c-(Figure 1a). DC counts were calculated as follows, using hemocytometer data for lymphocytes and monocytes and flow cytometry data for DC windows, as described previously[4, 5].
×
Absolute blood CD4+ T-cell counts were measured using a FACSCalibur flow cytometer (BD, Franklin Lakes, NJ, USA). Viral load was measured by the Amplicor (Roche Diagnostic Systems, Indianapolis, IN, USA) HIV-1 monitor ultrasensitive method with a detection limit of 40 copies/mL of plasma.
Assays for plasma HIV-1 RNA
Plasma HIV RNA was quantified by real-time PCR (Roche, Germany), a super-sensitive method. The sensitivity of detection of this assay was 40 copies/ml.
Statistical analysis
Comparisons were performed using the nonparametric independent sample tests, and all reported p values were two-sided and considered significant at p < 0.05. All data were analyzed using SPSS statistical software (version 16.0; SPSS, Chicago, IL, USA).
Anzeige
Results
To study the relationship between DCs and disease progression, we compared the pDC and mDC number in Fiebig stage III between the CD4 High, CD4 Low, and normal control groups. We found a higher pDC number in normal controls compared with the CD4 High and CD4 Low groups (Figure 1b). The pDC number between the CD4 High and the CD4 Low groups did not differ significantly (Figure 1b). However, mDCs were significantly lower in the CD4 Low relative to CD4 High and normal controls (Figure 1c). There was no statistically significant difference in the mDC number between the CD4 High and normal controls (Figure 1c). DC numbers were negatively correlated with HIV viral load (Table 2).
Table 2
Results of spearman correlation analysis
Viral load
Viral load set point
pDC
-0.323*
-0.350*
mDC
-0.233
-0.282
Correlation coefficients (Spearman correlation analysis) are shown.
*P < 0.05.
Discussion
Our results are consistent with reports that DCs are markedly reduced in number during acute HIV-1 infection[6‐9], particularly pDCs. The mechanism behind the decline in pDC numbers in acute HIV infection is not clear. It could be because of apoptosis as a direct result of infection[10, 11] or mediated by TRAIL and Fas ligand–Fas interactions; it could be a consequence of compromised production of pDC precursors because of bone marrow infection; or it may reflect pDC migration to lymphoid tissues after HIV-induced activation.
mDCs express apolipoprotein B mRNA editing enzyme catalytic polypeptides (APOBECs), proteins that deaminate cytidine to uridine in nascent minus-strand viral DNA, blocking HIV replication[11, 12]. Mature mDCs increase APOBECG expression, explaining their relative resistance to HIV-1 infection. mDCs capture and process HIV-1, and present associated antigens to T-cells. Thus, the loss of mDCs may on the one hand decrease APOBECG expression. On the other hand, the loss of mDCs decrease their ability of capture and process HIV-1 and present associated antigen to T cells. Therefore, this may explain why the loss of mDC in acute HIV infection could lead to rapid disease progression.
In conclusion, we found that the loss of mDC rather than pDC from the blood during acute HIV infection is associated with rapid disease progression. However, key questions remain to be answered regarding tissue distribution, development, and functional regulation.
Acknowledgments
This study was supported in part by the National Natural Science Foundation of China (81101250, 81371803), the National 12th Five-Year Major Projects of China (2012ZX10001-003, 2012ZX10001-006), Beijing Science and Technology Program funded (D141100000314005) and the Beijing Key Laboratory (BZ0089).
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The authors declare that they have no competing interests.
Authors’ contributions
YJ drafted the manuscript and statistical analyses. XS participated in flow cytometric analysis. TZ followed up patients and collected samples. XS and XH assisted with manuscript and data anlysis. YJ and WL assisted with flow cytometric analysis and data acquisition. HW conceived the study and participated in the data analysis. HW supervised and coordinated the study. All authors have read and approved the final manuscript.