Establishment of a CCR5-expressing T-lymphoblastoid cell line highly susceptible to R5 HIV type 1

The beta-chemokine receptor CCR5 is considered to be an attractive target for inhibition of CCR5-using (R5 or macrophage-tropic) HIV-1. However, R5 HIV-1 cannot replicate in CD4+ T cell or monocyte lines because of the lack of CCR5 expression on their surface, which apparently hampers discovery and development of effective CCR5 antagonists against HIV-1 replication. In this study, we have established the CCR5-expressing T cell line MOLT-4/CCR5, highly permissive to the replication of R5 HIV-1. The cells express a considerable amount of CCR5 on their surface. When the cells were infected with the R5 HIV-1 strains Ba-L and JR-FL, the virus-induced cytopathic effect (syncytium formation) was observed, and the cells produced large amounts of HIV-1 p24 antigen in the culture supernatants. The analyses of progeny viruses for their coreceptor use and gp120 V3 nucleotide sequence revealed that they were R5 HIV-1. The parental cell line MOLT-4 was much less susceptible to Ba-L and totally insusceptible to JR-FL. Furthermore, MOLT-4/CCR5 cells could support the replication of an R5 clinical isolate, but MOLT-4 cells could not. When TAK-779, a novel small-molecule nonpeptide CCR5 antagonist, was examined for its inhibitory effect on R5 HIV-1 replication in MOLT-4/CCR5 cells, the compound displayed potent antiviral activity, as demonstrated in peripheral blood mononuclear cells. These results indicate that the established cell line will be an extremely useful tool for experiments with R5 HIV-1.     

Segregation of R5 and X4 HIV-1 variants to memory T cell subsets differentially expressing CD62L in ex vivo infected human lymphoid tissue

OBJECTIVE: The mechanisms of HIV-triggered immunodeficiency were examined by determining the segregation of R5 and X4 HIV-1 variants into memory T cell subsets expressing differentially a homing receptor, CD62L-selectin, in human lymphoid tissue. METHODS: Subpopulations of CD3 and intracellular p24 gag-positive cells in human lymphoid tissue infected ex vivo with X4 HIV-1 variant NL4-3 and R5 HIV-1 variant AD8 were analysed for expression of the T cell memory markers CD45RO and CD45RA, the T cell homing receptor for lymphoid tissue CD62L, and the HIV-1 coreceptors CCR5 and CXCR4. RESULTS: Memory CD4 T cells were the predominant targets for productive infection of lymphoid tissue ex vivo with both R5 and X4 HIV-1. R5 HIV-1 predominantly infected CD62L-negative memory T cells, which selectively express CCR5. In contrast, X4 HIV-1 variants predominantly infected CD62L+ memory T cells, although CXCR4 coreceptor was equally expressed by memory T cells of both CD62L-positive and CD62L-negative subsets. A high proportion of X4 HIV-1, but not of R5 HIV-1, productively infected T cells, displayed a CD45RA+CD45RO+ phenotype. CONCLUSION: The selective expression of the CCR5 coreceptor by CD62L-negative terminally differentiated memory T cells correlates with the preferential productive infection of these cells with the R5 HIV-1 variant. The predominance of X4 HIV-1 variants in less-differentiated memory T cells may be related to their recent activation state, as suggested by the coexpression of both CD45RA and CD45RO molecules on their surface. Differential homing of CD62L-positive and CD62L-negative cells suggests different routes of dissemination of X4 and R5 viruses.     

No difference in in vitro susceptibility to HIV type 1 between high-risk HIV-negative Ethiopian commercial sex workers and low-risk control subjects

Host factors such as increased beta-chemokine production, HIV-1 coreceptor expression level, and HIV-1 coreceptor polymorphism have been thought to influence susceptibility to HIV-1 infection. To determine the protective role of these factors in Ethiopians who remained HIV-1 uninfected, despite multiple high-risk sexual exposures, we studied 21 Ethiopian women who had been employed as commercial sex workers (CSWs) for five or more years. The HIV-1-resistant CSWs were compared with low-risk age-matched female controls who had a comparable CD4+ cell percentage and mean fluorescence intensity (MFI). Genetic polymorphism in the CCR5, CCR2b, or SDF-1 genes appeared not to be associated with resistance in the Ethiopian CSWs. Expression levels of CCR5 and CXCR4 on naive, memory, and total CD4+ T cells tended to be higher in the resistant CSWs, while the production of beta-chemokines RANTES, MIP-1alpha, and MIP-1beta by phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMCs) was lower compared with low-risk HIV-1 negative controls. In vitro susceptibility of PHA-stimulated PBMCs to primary, CCR5-restricted, Ethiopian HIV-1 isolates was comparable between resistant CSWs and low-risk controls. In vitro susceptibility was positively correlated to CD4+ cell mean fluorescence intensity and negatively correlated to CCR5 expression levels, suggesting that infection of PBMCs was primarily dependent on expression levels of CD4 and that CCR5 expression, above a certain threshold, did not further increase susceptibility. Our results show that coreceptor polymorphism, coreceptor expression levels, beta-chemokine production, and cellular resistance to in vitro HIV-1 infection are not associated with protection in high-risk HIV-1-negative Ethiopian CSWs.     

CCR5 and CXCR4 expression correlated with X4 and R5 HIV-1 infection yet not sustained replication in Th1 and Th2 cells

OBJECTIVE: To investigate the infectivity of T-helper (Th)1 and Th2 cells (derived from ccr5 wild-type and homozygous ccr5 Delta 32) to R5 and X4 HIV-1. DESIGN: It remains unclear whether infection of Th1 and Th2 CD4 cells by R5 and X4 viruses mirrors their co-receptor expression profile as no direct quantitation of coreceptor levels and infection has been performed. In addition, it is unknown whether the lack of CCR5 expression affects the degree of Th1/Th2 polarization. METHODS: Surface expression of CCR5 and CXCR4 was determined by quantitative fluorescence activated cell sorter analysis on in vitro differentiated Th1 and Th2 cells. R5 (Ba-L) and X4 (IIIB) HIV-1 isolates were used for infection studies and the efficiency of viral entry was determined by quantitative real time polymerase chain reaction detection of reverse transcribed proviral DNA. RESULTS: Cell surface density of CCR5 molecules was eight-fold higher in Th1 versus Th2 subsets (P = 0.005) whereas CXCR4 surface density was four-fold higher in Th2 versus Th1 subsets (P = 0.006). Preferential infection and entry of Th1 cells by R5 HIV-1 was not associated with preferential replication, as eventually the R5-virus replicated to a higher level in Th2 cells in spite of lower initial viral infection/entry. By contrast, Th2 cells preferentially supported X4-virus infection and replication. High beta chemokine secretion by Th1 cells was associated with a lower R5 replication rate. CONCLUSIONS: Th1 and Th2 cells differ in their infection efficiency for R5 and X4 HIV-1. ccr5 Delta 32-homozygous individuals maintain the ability for Th1/Th2 polarization, i.e., the expression of CCR5 is not required for Th1/Th2 polarization.     

Low levels of co-receptor CCR5 are sufficient to permit HIV envelope-mediated fusion with resting CD4 T cells

The susceptibility of phenotypically CCR5-negative resting CD4 T cells for membrane fusion with a CCR5-specific HIV-1 envelope was analysed using a novel sensitive fusion assay. A very low overall density of CCR5 on T cells expressing high levels of CD4 was shown to be sufficient for HIV envelope-mediated membrane fusion. These findings are relevant to the understanding of how HIV-1 R5 strains enter and replicate in resting CD4 T cells in vivo.     

Effects of human immunodeficiency virus type 1 infection on CCR5 and CXCR4 coreceptor expression on CD4 T lymphocyte subsets in infants and adolescents

HIV-1 infection alters expression of CCR5 and CXCR4 on CD4 T cells in adults, although an effect by virus on expression of coreceptor genes in pediatric subjects is unknown. We designed an exploratory study to evaluate surface expression of CXCR4 and CCR5 on CD45RA and CD45RO subsets of CD4 T lymphocytes from 17 HIV-1-infected infants and adolescents and 16 healthy age-matched individuals. While age in the absence of HIV-1 infection was unrelated to coreceptor expression, infection affected coreceptor expression differentially in infants and adolescents. Among infected adolescents, CCR5 and CXCR4 expression was significantly increased on CD4 CD45RO T cells, while CXCR4 was diminished in the CD4 CD45RA subset. Although HIV-1 infection in infants was also associated with increased CXCR4 expression on the CD4 CD45RO subset, in contrast to adolescents, infection in infants had no impact on coreceptor expression within the CD45RA CD4 subset. The proportion of CD4 T cells coexpressing CD45RA and CD45RO was increased by infection in both infants and adolescents. The CD45RA CD45RO subset in culture expressed high levels of CD4, CXCR4, and CD69, an early activation marker, and was highly susceptible to HIV-1 infection and replication. Infection of transitional CD4 T cells coexpressing CD45RA and CD45RO could contribute in part to provirus in either CD45RA or CD45RO subsets. Deleterious effects by HIV-1 infection on CD4 T cell homeostasis were greater in infants then adolescents, indicating that adolescence may be an optimal age group for assessing vaccines to prevent or treat HIV-1 infection.     

Increased turnover of CCR5+ and redistribution of CCR5- CD4 T lymphocytes during primary human immunodeficiency virus type 1 infection

CCR5 is the major coreceptor for human immunodeficiency virus (HIV) type 1 during primary infection. CCR5+ CD4 T lymphocytes were studied in subjects with primary HIV-1 infection (PHI) or acute Epstein-Barr virus (EBV) infection and in HIV-uninfected controls. The early decline of CD4 T lymphocytes during PHI resulted from depletion of CCR5- CD4 T lymphocytes. After antiretroviral therapy, Ki-67- CCR5- CD4 T cell counts rapidly increased in the circulation, which suggests that the initial decrease was due to an alteration in trafficking and/or sequestration. In the CCR5+ subset of CD4 T cells, there was an elevation in the proliferative (Ki-67+) fraction during PHI, yet their total number remained in the normal range. In contrast, in acute EBV infection, proliferating CCR5+ CD4 T cells accumulated to very high levels, suggesting they have an important role in the early antiviral response, which may be impaired in HIV-1 infection.     

Susceptibility of HIV type 2 primary isolates to CCR5 and CXCR4 monoclonal antibodies, ligands, and small molecule inhibitors

Human immunodeficiency virus (HIV) entry into susceptible cells involves the interaction between viral envelope glycoproteins with CD4 and a chemokine receptor (coreceptor), namely CCR5 and CXCR4. This interaction has been studied to enable the discovery of a new class of antiretroviral drugs that targets the envelope glycoprotein-coreceptor interaction. However, very few data exist regarding HIV-2 susceptibility to these coreceptor inhibitors. With this work we aimed to identify this susceptibility in order to assess the potential use of these molecules to treat HIV-2-infected patients and to further understand the molecular basis of HIV-2 envelope glycoprotein interactions with CCR5 and CXCR4. We found that CCR5-using HIV-2 isolates are readily inhibited by maraviroc, TAK-779, and PF-227153, while monoclonal antibody 2D7 shows only residual or no inhibitory effects. The anti-HIV-2 activity of CXCR4-targeted molecules reveals that SDF-1α/CXCL12 inhibited all HIV-2 tested except one, while mAb 12G5 inhibited the replication of only two isolates, showing residual inhibitory effects with all the other CXCR4-using viruses. A major conclusion from our results is that infection by HIV-2 primary isolates is readily blocked in vitro by maraviroc, at concentrations similar to those required for HIV-1. The susceptibility to maraviroc was independent of CD4(+) T cell counts or clinical stage of the patient from which the virus was obtained. These findings indicate that maraviroc could constitute a reliable therapeutic alternative for HIV-2-infected patients, as long as they are infected with CCR5-using variants, and this may have direct implications for the clinical management of HIV-2-infected patients.     

Early proliferation of CCR5(+) CD38(+++) antigen-specific CD4(+) Th1 effector cells during primary HIV-1 infection

We investigated whether HIV-1 antigen-specific CD4(+) T cells expressed the viral coreceptor CCR5 during primary HIV-1 infection (PHI). In the peripheral blood of subjects with very early PHI (< 22 days after onset of symptoms), there was a 10- to 20-fold increase in the proportion of highly activated (CD38(+++)) and proliferating (Ki-67(+)) CD4(+) T cells that expressed CCR5(+), and were mostly T-cell intracellular antigen-1 (TIA-1)(+) perforin(+) granzyme B(+). Inthe same patient samples, CD4(+) T cells producing interferon (IFN)-gamma in response to HIV group-specific antigen (Gag) peptides were readily detected (median, 0.58%) by intracellular cytokine assay-these cells were again predominantly CD38(+++), Ki-67(+), and TIA-(++), as well as Bcl-2(low). On average, 20% of the Gag-specific CD4(+) T cells also expressed interleukin-2 (IL-2) and were CD127 (IL-7R)(+). Taken together, these results suggest that Gag-specific T-helper 1 (Th1) effector cells express CCR5 during the primary response and may include precursors of long-term self-renewing memory cells. However, in PHI subjects with later presentation, antigen-specific CD4(+) T cells could not be readily detected (median, 0.08%), coinciding with a 5-fold lower level of the CCR5(+)CD38(+++) CD4(+) T cells. These results suggest that the antiviral response to HIV-1 infection includes highly activated CCR5(+)CD4(+) cytotoxic effector cells, which are susceptible to both apoptosis and cytopathic infection with HIV-1, and rapidly decline.     

Expression of CD4 controls the susceptibility of THP-1 cells to infection by R5 and X4 HIV type 1 isolates

The monocytic THP-1 cell line has been used to study HIV-monocyte/macrophage interactions and the relationship between differentiation, virus production, and virus latency. Undifferentiated THP-1 cells are susceptible to infection by T-tropic human immunodeficiency virus type 1 (HIV-1) isolates that use the coreceptor CXCR4 (X4 strains). Treatment with phorbol 12-myristate 13-acetate (PMA) induces differentiation of THP-1 cells into adherent macrophage-like cells, which are susceptible to M-tropic, CCR5-dependent isolates (R5 strains). The aim of this study was to determine whether variabilities observed in the susceptibility of THP-1 cells to HIV-1 infection may be related to the differential expression of CD4, CCR5, and CXCR4. Both propagation and PMA treatment of THP-1 cells resulted in a marked decrease in CD4-positive cells, whereas the expression of CCR5 and CXCR4 was not reduced during propagation. Both coreceptors were also relatively "resistant" to PMA-induced downregulation when compared with the low percentage of CD4-positive cells in differentiated cultures. In undifferentiated THP-1 cells, low CD4 expression significantly reduced the susceptibility of the cells to infection with the R5 HIV-1(BaL) isolate, whereas a PMA-induced decrease in CD4 expression reduced permissiveness of the cells to the X4 HIV-1(IIIB) isolate. Thus, cell surface CD4 plays a primary role in determining how efficiently THP-1 cells can be infected with the X4 and the R5 isolates.     

Biological characterization of HIV type 1 envelope V3 regions from mothers and infants associated with perinatal transmission.

Our previous study has shown that the human immunodeficiency virus type 1 (HIV-1) envelope V3 region minor genotypes of infected mothers were transmitted to their infants and predominated initially as a homogeneous virus population in the infants (Ahmad N, Baroudy BM, Baker RC, et al.: J Virol 1995;69:1001-1012). Here we have characterized the biological properties, including cellular tropism, replication efficiency, cytopathic effects, and coreceptor utilization, of these V3 region isolates from mothers and infants. Nineteen V3 region sequences from three mother-infant pairs, including the minor variants of mothers and the major variants of infants as characterized in our previous study, were reciprocally inserted into an HIV-1 infectious molecular clone, pNL4-3, and chimeric viruses were generated by DNA transfections into HeLa cells. Equal amounts of chimeric viruses were then used to infect T lymphocyte cell lines (A3.01 and MT-2), primary blood lymphocytes (PBLs), primary monocyte-derived macrophages (MDMs), and coreceptor cell lines. We found that the V3 region chimeras failed to replicate in T lymphocyte cell lines but replicated in MDMs and PBLs, albeit at reduced levels compared with R5 laboratory HIV-1 strains. In addition, the V3 region chimeras were able to infect the HOS-CD4(+)CCR5(+) cell line, suggesting CCR5 coreceptor utilization. Moreover, the V3 region chimeras were unable to induce syncytia in MT-2 cells, indicative of non-syncytium-inducing (NSI) phenotypes. In conclusion, the HIV-1 minor genotypes of infected mothers with macrophage-tropic and NSI or R5 phenotypes are transmitted to their infants and are initially maintained with the same properties.     

HIV-1 pathogenesis differs in rectosigmoid and tonsillar tissues infected ex vivo with CCR5- and CXCR4-tropic HIV-1

Gut-associated lymphoid tissue (GALT) has been identified as the primary target of HIV-1 infection. To investigate why GALT is especially vulnerable to HIV-1, and to determine whether the selective transmission of CCR5-using viral variants (R5) in vivo is the result of a greater susceptibility of GALT to this viral variant, we performed comparative studies of CXCR4-using (X4) and R5 HIV-1 infections of human lymphoid (tonsillar) and rectosigmoid tissues ex vivo under controlled laboratory conditions. We found that the relative level of R5 replication in rectosigmoid tissue is much greater than in tonsillar tissue. This difference is associated with the expression of the CCR5 co-receptor on approximately 70% of CD4 T cells in rectosigmoid tissue, whereas in tonsillar tissue it is expressed on fewer than 15% of CD4 T cells. Furthermore, tonsillar tissue responds to X4 HIV-1 infection by upregulating the secretion of CC-chemokines, providing a potential CCR5 blockade and further resistance to R5 infection, whereas gut tissue failed to increase such innate immune responses. Our results show that rectosigmoid tissue is more prone than tonsillar lymphoid tissue to R5 HIV-1 infection, primarily because of the high prevalence and availability of R5 cell targets and reduced chemokine blockade. The majority of CD4 T cells express CXCR4, however, and X4 HIV-1 readily replicates in both tissues, suggesting that although the differential expression of co-receptors contributes to the GALT vulnerability to R5 HIV-1, it alone cannot account for the selective R5 infection of the rectal mucosa in vivo.     

The efficiency of R5 HIV-1 infection is determined by CD4 T-cell surface CCR5 density through G alpha i-protein signalling

OBJECTIVE AND DESIGN: The intensity of replication of CCR5-using HIV-1 strains is highly dependent on the number of CCR5 molecules on the surface of CD4-positive T cells. The molecular mechanisms responsible for this phenomenon remained so far unclear. As CCR5 co-receptors are coupled to G alpha i and G alpha q proteins, we tested the hypothesis that the activation triggered through these proteins secondary to the interaction between the viral envelope and CCR5 could account for the effect of the level of CCR5 expression on HIV-1 production. METHODS: We transduced the wild-type or a G-protein signalling-defective CCR5 gene into CD4/CCR5 HOS cells and peripheral blood mononuclear cells. The effect on cell activation in presence of a CCR5-binding chemokine and on HIV infection was monitored by measuring calcium mobilization and p24 antigen production, respectively. The role of G alpha i protein signalling was tested by adding pertussis toxin to the cell cultures or by transfecting small interfering (si) RNAs into the HOS cells. RESULTS: The over-expression of the wild-type form, but not of a G-protein signalling-defective form of CCR5, on the surface of CCR5 expressing peripheral blood mononuclear cells markedly increased their infectability. In addition, both pertussis toxin and G alpha i 1-specific siRNA drastically inhibited R5 infection. CONCLUSIONS: The signalling through G alpha i-protein induced upon R5 virion binding to CCR5 is responsible for the difference in HIV-1 infectability between CD4-positive T cells expressing low or high levels of cell surface CCR5 density. This observation sheds new light on the physiopathology of HIV infection, and opens new therapeutic opportunities targeting G alpha i signalling.     

New CCR5 variants associated with reduced HIV coreceptor function in southeast Asia

BACKGROUND: Despite multiple exposure to HIV-1, some individuals remain uninfected. This resistance has been associated with homozygosity for a 32 base pair deletion in the gene for the CCR5 receptor. This variant occurs frequently in Caucasians but is extremely rare in Asians or Africans. OBJECTIVE: To identify variations in CCR5 receptor gene that affect susceptibility to HIV infection in non-Caucasians. METHODS: CCR5 coding region polymorphisms were screened in three groups of Vietnamese subjects: 47 HIV-1 infected intravascular drug users, 50 highly HIV-1-exposed but seronegative intravascular drug users and 37 HIV-1-unexposed seronegative individuals. DNA was analysed by denaturing high performance liquid chromatography; this was followed by examination of the biochemical and HIV coreceptor properties of the coding regions. RESULTS: Five CCR5 coding region variants were identified in this Vietnamese population. The S185R, I254T and C269F mutations have not been previously described; G106R and R223Q have already been found in other Asian populations, but the functional properties of G106R is not known. These variants differed in biochemical and HIV coreceptor properties. S185R and I254T variants had receptor and coreceptor activities comparable to that of the wild type, whereas C269F and G106R behaved differently. This latter pair are poorly expressed at the cell surface, weakly bind macrophage inflammatory protein 1beta (CCL4) and RANTES (CCL5), and display reduced HIV-1 coreceptor efficiency. CONCLUSIONS: Among the five CCR5 variants found in this Vietnamese population, G106R and C269F displayed significant modifications of their receptor and coreceptor properties, which may contribute to susceptibility to HIV-1 infection and/or disease progression within this population.     

Concordant utilization of macrophage entry coreceptors by related variants within an HIV type 1 primary isolate viral swarm.

There is considerable diversity among HIV-1 strains in terms of their ability to use entry coreceptors on macrophages, especially CXCR4, but it is not known whether virus-specific differences exist among related members of a viral swarm. Defining how entry coreceptors on primary target cells are utilized by the spectrum of HIV-1 variants that emerge in vivo is important for understanding the relationship between coreceptor selectivity and pathogenesis. HIV-1 89.6(PI) is a dual-tropic primary isolate, and the prototype 89.6-cloned R5X4 Env uses both CXCR4 and CCR5 on macrophages. We generated a panel of env clones from the 89.6(PI) quasispecies and found a mixture of R5, R5X4, and X4 variants on the basis of fusion and infection of coreceptor-transfected cell lines. Here we address the use of macrophage coreceptors by these related Envs by analyzing fusion and infection of primary monocyte-derived macrophages mediated specifically through each coreceptor. All R5X4 Envs utilized both CXCR4 and CCR5 on macrophages, while R5 variants used CCR5 only. One variant characterized in cell lines as X4 used both CXCR4 and CCR5 on macrophages. No Env variant fused with macrophages through alternative coreceptor pathways. Thus, there was heterogeneity in coreceptor use among the related Env variants, but use of each coreceptor specifically in macrophages was consistent among members of the viral swarm. Coreceptor use in transfected cells generally predicted use in primary macrophages, although for some Envs macrophages may be a more sensitive indicator of CCR5 use than transfected cell lines.     

R5嗜性的人类免疫缺陷病毒-1在疾病不同阶段的生物学特性

目的 研究HIV-1感染者不同时期分离的R5毒株的生物学特性.方法 采用传统的共培养方法分离并培养HIV-1,用表达CD4和CC趋化因子受体5(CCR5)或CXC趋化因子受体4(CXCR4)的GHOST细胞系,通过流式细胞仪测定病毒辅助受体的利用和感染性,从而判断所分离毒株的CCR5嗜型(R5型毒株);使用2 ng P24病毒量感染正常人分离的外周血单个核细胞(PBMC),ELISA法检测第1、3、5、7、10、15天的HIV-1 P24抗原,反映病毒复制能力;采用HIV-1核酸荧光定量检测试剂盒测定血浆病毒载量.数据分析采用t检验.结果 HIV-1B'亚型感染者22例,其中CD4+细胞>0.2×109/L和CD4+细胞≤0.2×109/L各11例;所分离的病毒仅利用CCR5辅助受体,均为R5型毒株,感染性的结果显示,来自CD4+细胞≤0.2×109/L的11株R5毒株的感染性为(7.392 7±4.584 2)%,而CD4+细胞>0.2×109/L的为(2.613 6±1.610 5)%,差异有统计学意义(t=3.262,P<0.05);两组病毒复制滴度在第7天开始明显上升,培养第7、10、15天,两组病毒复制动力学差异有统计学意义(t值分别为3.771、2.509和2.260;P<0.05),CD4+细胞≤0.2×109/L的R5毒株的复制能力较CD4+细胞>0.2×109/L的明显增强;CD4+细胞≤0.2 × 109/L R5型毒株的病毒载量的对数值为(5.606 8±0.815 1)拷贝/mL,CD4+细胞>0.2 × 109/L的为(4.729 8±0.431 6)拷贝/mL,两组差异有统计学意义(t=3.771,P<0.05).结论 疾病进展过程中,即使病毒的辅助受体利用未从CCR5转变为CXCR4,但病毒的感染性和复制能力已有明显改变.     

Mycobacterium avium complex augments macrophage HIV-1 production and increases CCR5 expression

Infection with HIV-1 results in pronounced immune suppression and susceptibility to opportunistic infections (OI). Reciprocally, OI augment HIV-1 replication. As we have shown for Mycobacterium avium complex (MAC) and Pneumocystis carinii, macrophages infected with opportunistic pathogens and within lymphoid tissues containing OI, exhibit striking levels of viral replication. To explore potential underlying mechanisms for increased HIV-1 replication associated with coinfection, blood monocytes were exposed to MAC antigens (MAg) or viable MAC and their levels of tumor necrosis factor α (TNFα) and HIV-1 coreceptors monitored. MAC enhanced TNFα production in vitro, consistent with its expression in coinfected lymph nodes. Using a polyclonal antibody to the CCR5 coreceptor that mediates viral entry of macrophage tropic HIV-1, a subset of unstimulated monocytes was shown to be CCR5-positive by fluorescence-activated cell sorter analysis. After stimulation with MAg or infection with MAC, CCR5 expression was increased at both the mRNA level and on the cell surface. Up-regulation of CCR5 by MAC was not paralleled by an increase in the T cell tropic coreceptor, CXCR4. Increases in NF-κB, TNFα, and CCR5 were consistent with the enhanced production of HIV-1 in MAg-treated adherent macrophage cultures as measured by HIV-1 p24 levels. Increased CCR5 was also detected in coinfected lymph nodes as compared with tissues with only HIV-1. The increased production of TNFα, together with elevated expression of CCR5, provide potential mechanisms for enhanced infection and replication of HIV-1 by macrophages in OI-infected cells and tissues. Consequently, treating OI may inhibit not only the OI-induced pathology, but also limit the viral burden.