Targeted Mutational Analysis of Cortisol-Producing Adenomas

CONTEXT

Somatic gene mutations have been identified in only about half of cortisol-producing adenomas (CPAs). Affected genes include PRKACA, GNAS, PRKAR1A, and CTNNB1.

OBJECTIVE

This work aims to expand our understanding of the prevalence of somatic mutations in CPAs from patients with overt Cushing syndrome (OCS) and "subclinical" mild autonomous cortisol excess (MACE), with an immunohistochemistry (IHC)‒guided targeted amplicon sequencing approach using formalin-fixed paraffin-embedded (FFPE) tissue.

METHODS

We analyzed FFPE adrenal tissue from 77 patients (n = 12 men, 65 women) with either OCS (n = 32) or MACE (n = 45). Using IHC for 17α-hydroxylase/17,20-lyase (CYP17A1) and 3β-hydroxysteroid dehydrogenase (HSD3B2), we identified 78 CPAs (32 OCS CPAs and 46 MACE CPAs). Genomic DNA was isolated from the FFPE CPAs and subjected to targeted amplicon sequencing for identification of somatic mutations.

RESULTS

Somatic mutations were identified in 71.8% (56/78) of the CPAs. While PRKACA was the most frequently mutated gene in OCS CPAs (14/32, 43.8%), somatic genetic aberrations in CTNNB1 occurred in 56.5% (26/46) of the MACE CPAs. Most GNAS mutations were observed in MACE CPAs (5/7, 71.4%). No mutations were observed in PRKAR1A. In addition to the known mutations, we identified one previously unreported mutation in PRKACA. Two patients with MACE harbored 2 adjacent tumors within the same adrenal gland - one patient had 2 CPAs, and the other patient had a CPA and an aldosterone-producing adenoma (identified by IHC for aldosterone synthase).

CONCLUSION

A comprehensive FFPE IHC-guided gene-targeted sequencing approach identified somatic mutations in 71.8% of the CPAs. OCS CPAs demonstrated a distinct mutation profile compared to MACE CPAs.

SAT-352 Comprehensive Genetic Analysis of Cortisol-Producing Adenomas

Background: Cortisol-producing adenomas (CPA) are the most common cause of adrenal Cushing’s syndrome. Next-generation sequencing (NGS) has recently facilitated the identification of somatic mutations that cause autonomous cortisol production by these tumors. The most commonly mutated gene in CPAs is PRKACA, resulting in hyper-activation of the protein kinase A (PKA) signaling pathway. Somatic mutations of GNAS, PRKAR1A, and CTNNB1 have also been identified in CPAs. However, direct mutation analysis of CPAs using formalin-fixed paraffin-embedded (FFPE) materials and immunohistochemistry (IHC)-guided targeted NGS has not been done before. Objective: To investigate the prevalence of somatic mutations in CPAs using FFPE tissue sections and targeted NGS. Methods: FFPE adrenal tumor tissue from 37 patients with Cushing’s syndrome who underwent adrenalectomy in our institution was used. IHC of HSD3B2 and CYP17A1 was performed. Aldosterone synthase (CYP11B2) IHC was also performed on tumors with low CYP17A1 expression and one from a patient with concomitant primary aldosteronism with Cushing’s syndrome. IHC-guided gDNA isolation was performed from 40 functional tumor samples [38 CPAs and two CPA-adjacent aldosterone-producing adenomas (APAs)]. Targeted NGS was implemented to identify somatic mutations involved in the tumors. The panel of targeted NGS included PKA pathway related genes (PRKACA, PRKAR1A, GNAS) and β-catenin (CTNNB1), as well as aldosterone-driver genes (KCNJ5, CACNA1D, ATP1A1, ATP2B3). Results: Somatic mutations were found in 63% (24/38) of CPAs. The two most commonly mutated genes were PRKACA (29%, n= 11/38) and CTNNB1 (24%, n= 9/38). GNAS mutations were found in 8% (3/38) of the CPAs and a PRKAR1A mutation was found in one CPA (3%). Of the two CPA-adjacent APAs, one had a KCNJ5 mutation, while the other had a CACNA1D mutation. Clinically, the autonomous cortisol production resulting from these CPAs was dichotomized into either overt or subclinical Cushing’s syndrome. Intriguingly, the majority of PRKACA mutations were found in the overt Cushing’s syndrome group (62%, n= 8/13) compared to only 1/23 (4%) of the subclinical Cushing’s syndrome cohort. The overt Cushing’s syndrome group also contained the single PRKAR1A mutation (8%, n=1/13). Furthermore, CTNNB1 (39%, n= 9/23) and GNAS (13%, n= 3/23) mutations were exclusively observed in subclinical Cushing’s syndrome patients. Conclusion: Targeted NGS on FFPE CPA tissue identified somatic mutations in 63% of tumors. CPAs causing overt Cushing’s syndrome appear to have a distinct mutation profile compared to the tumors observed in subclinical Cushing’s syndrome.

Inhibition of HIV-1 infection by down-regulation of the CXCR4 co-receptor using an intracellular single chain variable fragment against CXCR4

CXCR4 is the major co-receptor used by X4 strains of human immunodeficiency virus type I (HIV-1). In HIV-1-infected patients, the appearance of X4 strains (T cell line-tropic) correlates with disease progression. Since its discovery, the CXCR4 co-receptor has been a major target for different agents which block its function, such as stromal-derived factor 1alpha (SDF-1alpha) and the anti-CXCR4 monoclonal antibody, 12G5. In the present studies, the 12G5 hybridoma was used to construct a single-chain variable antibody fragment (SFv). Murine leukemia virus (MLV) and simian virus 40 (SV(40)) were utilized as delivery vehicles for the anti-CXCR4 SFv. Intracellular expression of the anti-CXCR4 SFv led to down-regulation of this critical co-receptor, as demonstrated by immunostaining. This effect significantly and specifically protected transduced cells from challenge with HIV-1, as measured by HIV-1 p24 antigen expression. Inhibition of HIV-1 replication was specific for X4 HIV-1 strains as demonstrated by MAGI assays. HeLa-CD4/betagal-CCR5 cells expressing the anti-CXCR4 SFv showed significant inhibition of infectivity by the X4 HIV-1 strain NL4-3, but not with the R5 HIV-1 strain Bal. Thus, this anti-HIV-1 molecular therapy has the potential to inhibit HIV-1 replication and virion spread. Targeting CXCR4 by intracellular immunization could be of additional benefit to certain HIV-1-infected patients on highly active antiretroviral therapy (HAART).

Duplicated regions of AF-4 intron 4 at t(4;11) translocation breakpoints

BACKGROUND

AF-4 is a common partner gene of MLL. AF-4 breakpoints occur in introns, but most AF-4 introns are uncharacterized.

METHODS AND RESULTS

We cloned AF-4 intron 4 and examined the frequency of breakpoints in this intron. The 5.8-kb intron is rich in repeat sequences and was the site of translocation in 3 of 17 leukemias with t(4;11). We cloned the der (11) and der (4) breakpoints and isolated the fusion transcripts in the cell line MV4-11 and in a de novo acute lymphoblastic leukemia (ALL). Both translocations joined MLL intron 6 and AF-4 intron 4. In MV4-11, 249 bases from AF-4 were present in both derivative chromosomes, indicating duplication. In the de novo ALL, duplication of 446 bases from MLL and AF-4 occurred. Reciprocal fusion transcripts were expressed.

CONCLUSIONS

Intronic sequence of AF-4 is useful for molecular diagnosis of t(4;11). Duplicated intronic regions suggest staggered chromosomal breakage.

Expression of CXCR4, the receptor for stromal cell-derived factor-1 on fetal and adult human lympho-hematopoietic progenitors

Stromal cell-derived factor-1 (SDF-1) is a CXC chemokine produced by stromal cells that acts as a chemoattractant for human CD34+ progenitor cells. We investigated the expression of CXCR4, the receptor for SDF-1, on CD34+ cells from different hematopoietic sites and developmental stages. CXCR4 was detected by flow cytometry on 37 % of fetal bone marrow (BM) [gestation weeks (gw) 14-23] and 40% of adult BM CD34+ cells. Interestingly, in fetal liver CD34+ cells, CXCR4 was expressed at lower levels at later stages (9%, gw 20-23) compared to early stages of development (39%, gw 7.5-18), suggesting a development-related change in the migratory capacity of progenitors. CXCR4 was detected at similar levels on both phenotypically primitive and committed progenitors from fetal and adult sites. However, B cell lineage progenitor and precursor cells expressed CXCR4 at the highest density (80% of BM CD34+/CD10+ pro-B cells are CXCR4+). CXCR4 was also expressed in the fetal thymus in early T cell precursors and found to be down-regulated during T cell maturation. Finally, we found that stem cell factor, alone or in combination with other cytokines, can up-modulate CXCR4 expression on CD34+ cells by three- to fourfold. In conclusion, our results suggest that CXCR4 may play an important role in the local and systemic trafficking of human CD34+ cells as well as in human B lymphopoiesis and that its expression can be modulated by cytokines.

Megakaryocyte precursors, megakaryocytes and platelets express the HIV co-receptor CXCR4 on their surface: determination of response to stromal-derived factor-1 by megakaryocytes and platelets

Thrombocytopenia is a late complication of human immunodeficiency virus (HIV) infection. The chemokine receptor CXCR4 has been shown to be a co-receptor for lymphocyte-tropic HIV-1 strains. CXCR4 is also a natural receptor for the chemokine SDF-1. We have previously shown that CXCR1 and CXCR2 are present on megakaryocytes and platelets. Although interleukin-8 (IL-8) and other chemokines that bind to these two receptors do not activate platelets, they are able to inhibit megakaryocytopoiesis, presumably through these receptors. We therefore examined whether CXCR4 is present on developing and mature megakaryocytes and on platelets. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated the presence of CXCR4 message. Immature and mature alphaIIbbeta3+ megakaryocytes, and platelets were also positive for CXCR4 by flow cytometric studies using a CXCR4-specific antibody. We then tested whether SDF-1 can affect the biology of these cells. CD34+ cells and immature alphaIIbbeta3+ cells responded to SDF-1 as indicated by Ca2+ mobilization and chemotaxis. However, mature megakaryocytes failed to demonstrate either of these responses, in spite of their continued ability to bind 125I-SDF-1. Further, SDF-1 failed to inhibit megakaryocyte colony growth. Platelets bound 125I-SDF-1 with a K(D) similar to the affinity seen for CXCR4 on other cells, yet SDF-1 did not aggregate washed platelets nor augment aggregation by low-dose ADP or thrombin. SDF-1 also failed to stimulate Ca2+ mobilization, granular release or expression of P-selectin in platelets. Accordingly, although our studies demonstrate that CD34+ precursors, megakaryocytes and platelets all express CXCR4 and bind SDF-1, biological effects were only demonstrable of SDF-1 on CD34+ precursors. The potential biological implications of CXCR4 expression on maturing megakaryocytes and platelets in normal individuals and following HIV infection are discussed.

Chemokine receptors and the molecular basis for human immunodeficiency virus type 1 entry into peripheral hematopoietic stem cells and their progeny

There exist at least two major coreceptors for human immunodeficiency virus (HIV)-1 entry into target cells, the CXCR-4 and CCR-5 chemokine receptors for T lymphocyte-tropic and macrophage-tropic strains of HIV-1, respectively. Highly purified human CD34 cells derived from umbilical cord blood were shown not to express CD4, CXCR-4, and CCR-5 on their cell membranes, as analyzed by immunofluorescent staining and flow cytometric analyses. However, expression of these molecules was inducible when highly purified CD34 cells underwent proliferation and differentiation along myeloid cell lineages, in the presence of suitable cocktails of hematopoietic growth factors. HIV-1 infectivity studies showed that macrophage-tropic strains of HIV-1 could efficiently infect differentiated CD34 cells. T lymphocyte-tropic strains could not infect CD34 cells before or after induction of receptors and coreceptors. These data suggest that HIV-1 infection of CD34 cells and their progeny depends on membrane expression of the critical CD4 receptor, as well as certain chemokine coreceptors.

CC-chemokines enhance the replication of T-tropic strains of HIV-1 in CD4(+) T cells: role of signal transduction

This study demonstrates that several CC-chemokines, including those that inhibit entry and replication of macrophage-tropic strains of HIV, increase the replication of T cell (T)-tropic strains in CD4(+) T cells. Enhancement of T-tropic HIV replication is observed at early stages of replication, requires signaling through inhibitory guanine nucleotide-binding regulatory (Gi) proteins, and is associated with increased cell surface colocalization of CD4 and the T-tropic HIV coreceptor CXCR4. These findings may further our understanding of the factors that influence the replication and spread of T-tropic strains of HIV in vivo and suggest that the use of cell signaling CC-chemokines as therapeutic agents for the purpose of limiting HIV replication in vivo should be approached with caution.

Interactions among HIV gp120, CD4, and CXCR4: dependence on CD4 expression level, gp120 viral origin, conservation of the gp120 COOH- and NH2-termini and V1/V2 and V3 loops, and sensitivity to neutralizing antibodies

The binding of HIV-derived recombinant soluble (s)gp120 to the CD4(+)/CXCR4(+) A3.01 T cell line inhibits the binding of the CXCR4-specific monoclonal antibodies 12G5, which interacts with the second extracellular loop, and 6H8, which binds the NH2 terminus. We have used this as an assay to analyse the interaction of recombinant sgp120 from diverse viral origins with CXCR4. The strength of the interaction between sgp120 and CXCR4 correlated with sgp120 affinity for the CD4-CXCR4 complex, and the interaction of sgp120MN and sgp120IIIB with CXCR4 was highly dependent on the level of CD4 expressed on a variety of different T cell lines. sgp120 from X4, R5X4, and R5 viruses interacted with CXCR4, although the R5 sgp120-CXCR4 interactions were weaker than those of the other gp120s. The interaction of sgp120IIIB or sgp120MN with CXCR4 was inhibited by neutralizing monoclonal antibodies that prevent the sgp120-CD4 interaction but also by antibodies specific for the gp120 V2 and V3 loops, the CD4-induced epitope and the 2G12 epitope, which interfere weakly or not at all with CD4-sgp120 binding. The binding to A3.01 cells of wild-type sgp120HxB2, but not of sgp120 deleted in the COOH and NH2 termini, interfered with 12G5 binding in a dose-dependent manner. Further deletion of the V1 and V2 loops restored CXCR4 binding activity, but additional removal of the V3 loop eliminated the gp120-CXCR4 interaction, without decreasing the affinity between mutated sgp120 and CD4. Taken together, these results demonstrate that the interactions between sgp120 and CXCR4 are globally similar to those previously observed between sgp120 and CCR5, with some apparent differences in the strength of the sgp120-CXCR4 interactions and their dependence on CD4.

Transendothelial migration of megakaryocytes in response to stromal cell-derived factor 1 (SDF-1) enhances platelet formation

Although thrombopoietin has been shown to promote megakaryocyte (MK) proliferation and maturation, the exact mechanism and site of platelet formation are not well defined. Studies have shown that MKs may transmigrate through bone marrow endothelial cells (BMEC), and release platelets within the sinusoidal space or lung capillaries. In search for chemotactic factor(s) that may mediate transmigration of MKs, we have discovered that mature polyploid MKs express the G protein-coupled chemokine receptor CXCR4 (Fusin, LESTR). Therefore, we explored the possibility that stromal cell-derived factor 1 (SDF-1), the ligand for CXCR4, may also induce transendothelial migration of mature MKs. SDF-1, but not other CXC or CC chemokines, was able to mediate MK migration (ED50 = 125 pmol/liter). The MK chemotaxis induced by SDF-1 was inhibited by the CXCR4-specific mAb (12G5) and by pertussis toxin, demonstrating that signaling via the G protein-coupled receptor CXCR4 was necessary for migration. SDF-1 also induced MKs to migrate through confluent monolayers of BMEC by increasing the affinity of MKs for BMEC. Activation of BMEC with interleukin 1beta resulted in a threefold increase in the migration of MKs in response to SDF-1. Neutralizing mAb to the endothelial-specific adhesion molecule E-selectin blocked the migration of MKs by 50%, suggesting that cellular interaction of MKs with BMEC is critical for the migration of MKs. Light microscopy and ploidy determination of transmigrated MKs demonstrated predominance of polyploid MKs. Virtually all platelets generated in the lower chamber also expressed CXCR4. Platelets formed in the lower chamber were functional and expressed P-selectin (CD62P) in response to thrombin stimulation. Electron microscopy of the cells that transmigrated through the BMEC monolayers in response to SDF-1 demonstrated the presence of intact polyploid MKs as well as MKs in the process of platelet formation. These results suggest that SDF-1 is a potent chemotactic factor for mature MKs. Expression of CXCR4 may be the critical cellular signal for transmigration of MKs and platelet formation.

Neuronal apoptosis induced by HIV-1 gp120 and the chemokine SDF-1 alpha is mediated by the chemokine receptor CXCR4

CXCR4, a seven transmembrane domain G-protein-coupled receptor for the Cys-X-Cys class of chemokines, is one of several chemokine receptors that can act as a co-receptor with CD4 for the human immunodeficiency virus (HIV-1) glycoprotein gp120 [1-3]. CXCR4 can mediate the entry of HIV-1 strains that specifically infect T cells, such as the IIB strain (see [4] for review). Recent reports indicate that gp120 can signal through CXCR4 [5] and it has been suggested that signal transduction, mediated by the viral envelope, might influence viral-associated cytopathicity or apoptosis [6]. Neuronal apoptosis is a feature of HIV-1 infection in the brain [7,8], although the exact mechanism is unknown. Here, we address the possible role of CXCR4 in inducing apoptosis using cells of the hNT human neuronal cell line; these cells resemble immature post-mitotic cholinergic neurons and have a number of neuronal characteristics [9-15]. We have previously shown that gp120 from the HIV-1 IIIB strain binds with high affinity to CXCR4 expressed on hNT neurons [15]. We now find that both IIIB gp120 and the Cys-X-Cys chemokine SDF-1 alpha can directly induce apoptosis in hNT neurons in the absence of CD4 and in a dose-dependent manner. To our knowledge, this is the first report of a chemokine and an HIV-1 envelope glycoprotein eliciting apoptotic responses through a chemokine receptor.

Expression patterns of the HIV type 1 coreceptors CCR5 and CXCR4 on CD4+ T cells and monocytes from cord and adult blood

We have measured the surface expression of the HIV-1 coreceptors CCR5 and CXCR4 on CD4+ T cells and monocytes from cord and adult blood. The expression of CCR5 was largely restricted to the memory (CD45RAlow) subset, whereas CXCR4 was expressed on both memory and naive (CD45RAhigh) T cells. The paucity of memory CD4+ T cells in cord blood means that CCR5-positive cells are relatively uncommon, so the overall extent of CCR5 expression was reduced in cord blood, compared with adult blood. IL-2 activation of CD4+ T cells from both cord and adult bloods caused a substantial increase in CCR5 expression, but moderately decreased CXCR4 expression. PHA stimulation increased CCR5 expression slightly, but only on naive cells. Monocytes expressed both CCR5 and CXCR4 at levels that differed little between cord and adult blood.

Productive infection of neonatal CD8+ T lymphocytes by HIV-1

CD8+ T lymphocytes confer significant but ultimately insufficient protection against HIV infection. Here we report that activated neonatal CD8+ T cells can be productively infected in vitro by macrophage-tropic (M-tropic) HIV-1 isolates, which are responsible for disease transmission, whereas they are resistant to T cell-tropic (T-tropic) HIV strains. Physiological activation of CD8-alpha/beta+ CD4- T cell receptor-alpha/beta+ neonatal T cells, including activation by allogeneic dendritic cells, induces the accumulation of CD4 messenger RNA and the expression of CD4 Ag on the cell surface. The large majority of anti-CD3/B7.1-activated cord blood CD8+ T cells coexpress CD4, the primary HIV receptor, as well as CCR5 and CXCR4, the coreceptors used by M- and T-tropic HIV-1 strains, respectively, to enter target cells. These findings are relevant to the rapid progression of neonatal HIV infection. Infection of primary HIV-specific CD8+ T cells may compromise their survival and thus significantly contribute to the failure of the immune system to control the infection. Furthermore, these results indicate a previously unsuspected level of plasticity in the neonatal immune system in the regulation of CD4 expression by costimulation.

Identification and characterization of the CXCR4 chemokine receptor in human T cell lines: ligand binding, biological activity, and HIV-1 infectivity

The CXCR4 chemokine receptor has been shown to respond to the C-X-C chemokine stromal-derived factor (SDF-1) and has recently been shown to be an important coreceptor for HIV-1 infection. In the present paper we have tested a number of human lymphocyte cell lines, including Jurkat, HUT78, CEM, and Sup-T1 for the presence of CXCR4 receptors. We found that these T cell lines bind SDF-1alpha and SDF-1beta with high affinity. The CXCR4 Ab 12G5 inhibited both SDF-1 binding and HIV-1LAI-mediated fusion of CEM. Scatchard analysis revealed the presence of approximately 150,000 SDF-1alpha-binding sites per cell with a Kd between 5 and 10 nM. Cross-competition experiments using unlabeled SDF-1alpha and SDF-1beta revealed that both chemokines are equally capable of displacing their radiolabeled counterparts. Internalization studies with [125]I-SDF-1alpha revealed that Jurkat cells internalized greater than 90% of the ligand by 2 h at 37 degrees C. SDF-1alpha was also chemotactic for Jurkat cells and caused an increase in the rate of extracellular acidification that was half-maximal at 18 nM SDF-1alpha and could be inhibited by pretreatment with the SDF-1 proteins, pertussis toxin, or the Ab 12G5. Finally, SDF-1alpha also caused an increase in the cytosolic Ca2+ concentration in Sup-T1 cells that was abolished by preincubating the cells with pertussis toxin or PMA and inhibited by the Ab 12G5. This molecular characterization of CXCR4 receptors should prove useful in clarifying receptor interaction with SDF-1 proteins and with HIV-1 glycoprotein, with the ultimate aim of targeting the viral interaction for therapeutic intervention.

Promonocytic U937 subclones expressing CD4 and CXCR4 are resistant to infection with and cell-to-cell fusion by T-cell-tropic human immunodeficiency virus type 1

Different strains of human immunodeficiency virus type 1 (HIV-1) vary markedly in the ability to infect cells of the monocyte/macrophage (M/M) lineage. M/M are generally resistant to infection with T-cell-tropic (T-tropic) strains of HIV-1. Recently, the chemokine receptors CCR5 and CXCR4 were identified as cofactors for fusion/entry of macrophage- and T-tropic strains of HIV-1, respectively. To investigate the mechanisms of resistance of M/M to T-tropic HIV-1 infection, we examined a number of subclones of the U937 promonocytic cell line. We found that certain subclones of U937 (plus clones) could, while others (minus clones) could not, support replication of T-tropic strains of HIV-1. We demonstrate that (i) both minus and plus clones support HIV-1 replication when transfected with an infectious molecular cDNA clone of a T-tropic HIV-1; (ii) minus clones do not, but plus clones do, efficiently support fusion with cells expressing HIV-1 IIIB Env; (iii) both plus and minus clones (with the exception of one clone) express physiologically functional CXCR4 protein as well as CD4 on the cell surface; (iv) introduction of CXCR4 into the CXCR4-negative clone does not restore fusogenicity with or susceptibility to T-tropic HIV-1; and (v) a ligand (stromal cell-derived factor 1) for or a monoclonal antibody (12G5) to CXCR4 does not effectively inhibit HIV-mediated cell-to-cell fusion of U937 cells. These data indicate that resistance to T-tropic HIV-1 infection of U937 minus clones occurs at fusion/ entry events and that expression of functional CXCR4 and CD4 is not a sole determinant for susceptibility to T-tropic HIV-1 infection; furthermore, they suggest that other factors are positively or negatively involved in HIV-mediated cell-to-cell fusion in U937 promonocytic cells.

HIV-1 gp120 induces an association between CD4 and the chemokine receptor CXCR4

For efficient entry into target cells, certain T cell-tropic HIV-1 isolates require both CD4 and the coreceptor CXCR4. However, the molecular interactions among CD4, CXCR4, and the HIV-1 envelope glycoproteins are only now being elucidated. Here we show that the binding of soluble gp120 from one macrophage-tropic and four T cell-tropic viruses to a CD4+, but not to a CD4-, T cell line, decreased the binding of an mAb specific for CXCR4 to its epitope, implying an interaction among gp120, CD4, and CXCR4. To confirm such an interaction, we conducted double- and triple-color confocal laser scanning microscopy on CD4+/CXCR4+ cells and determined the extent of CD4 and CXCR4 colocalization by a semiquantitative analysis. In the absence of gp120, a low level of constitutive colocalization between CD4 and CXCR4 was observed. Treatment with T cell-tropic-derived gp120 and, to a lesser extent, macrophage-tropic-derived gp120, increased the colocalization of CD4 with CXCR4, and triple staining indicated that gp120 was associated with the CD4-CXCR4 complexes. Cocapping of the gp120-CD4-CXCR4 complexes at 37 degrees C resulted in the cointernalization of a proportion of the gp120-CXCR4 complexes into intracellular vesicles. These data demonstrate that the binding of gp120 to CD4+ T cells induces the formation of a trimolecular complex consisting of gp120, CD4, and the HIV-1 coreceptor molecule CXCR4.

HIV-1 gp120 induces an association between CD4 and the chemokine receptor CXCR4

For efficient entry into target cells, certain T cell-tropic HIV-1 isolates require both CD4 and the coreceptor CXCR4. However, the molecular interactions among CD4, CXCR4, and the HIV-1 envelope glycoproteins are only now being elucidated. Here we show that the binding of soluble gp120 from one macrophage-tropic and four T cell-tropic viruses to a CD4+, but not to a CD4-, T cell line, decreased the binding of an mAb specific for CXCR4 to its epitope, implying an interaction among gp120, CD4, and CXCR4. To confirm such an interaction, we conducted double- and triple-color confocal laser scanning microscopy on CD4+/CXCR4+ cells and determined the extent of CD4 and CXCR4 colocalization by a semiquantitative analysis. In the absence of gp120, a low level of constitutive colocalization between CD4 and CXCR4 was observed. Treatment with T cell-tropic-derived gp120 and, to a lesser extent, macrophage-tropic-derived gp120, increased the colocalization of CD4 with CXCR4, and triple staining indicated that gp120 was associated with the CD4-CXCR4 complexes. Cocapping of the gp120-CD4-CXCR4 complexes at 37 degrees C resulted in the cointernalization of a proportion of the gp120-CXCR4 complexes into intracellular vesicles. These data demonstrate that the binding of gp120 to CD4+ T cells induces the formation of a trimolecular complex consisting of gp120, CD4, and the HIV-1 coreceptor molecule CXCR4.

A monoclonal antibody (12G5) directed against CXCR-4 inhibits infection with the dual-tropic human immunodeficiency virus type 1 isolate HIV-1(89.6) but not the T-tropic isolate HIV-1(HxB)

We used a monoclonal antibody (12G5) directed against an extracellular domain of CXCR-4 to investigate the role of this receptor in infection of immortalized lymphoid cell lines, peripheral blood mononuclear cells (PBMCs), and primary brain microglia with a dual-tropic strain of human immunodeficiency virus (HIV-1(89.6)) and a T-tropic strain (HIV-1(IIIB)). Addition of antibody 12G5 to cells prior to and during infection with HIV-1(89.6) inhibited p24 production 100- to 10,000-fold in CEMx174 and 174-CD4 cells and about 10-fold in PBMC cultures but had no activity against infection of either monocyte-derived macrophages or brain microglia. In contrast, 12G5 had little or no effect on infection of CEMx174 cells with HIV-1(IIIB) or HIV-1(HxB). To identify the region of the HIV-1(89.6) envelope that confers sensitivity to 12G5, we used chimeric molecular clones. Chimeras containing the V3 loop region of HIV-1(89.6) were inhibited by 12G5 to the same degree as wild-type HIV-1(89.6) whereas replication of those viruses containing the V3 loop of HIV-1(HxB) was not inhibited by the antibody. A similar pattern was seen in infections of a U87 glioblastoma line that coexpresses CD4 and CXCR-4. Antibody 12G5 was also able to block fusion between HeLa-CD4 cells and CEMx174 cells chronically infected with HIV-1(89.6) but had no effect on fusion mediated by cells chronically infected with HIV-1(IIIB). Taken together, these results suggest that different strains of HIV-1 may interact with different sites on CXCR-4 or may have different binding affinities for the coreceptor.

CD4-independent association between HIV-1 gp120 and CXCR4: functional chemokine receptors are expressed in human neurons

BACKGROUND

Chemokines are a family of proteins that chemoattract and activate immune cells by interacting with specific receptors on the surface of their targets. We have shown previously that chemokine receptors including the interleukin-8 receptor B (CXCR2) and the Duffy blood group antigen are expressed on subsets of neurons in various regions of the adult nervous system.

RESULTS

Using a combination of immunohistochemical staining and receptor binding studies, we show that hNT cells, which are differentiated human neurons derived from the cell line NTera2, express functional chemokine receptors of the C-X-X and C-C types. These chemokine receptors include CXCR2, CXCR4, CCR1 and CCR5. We demonstrate high-affinity binding of both types of chemokines to hNT neurons and dose-dependent chemotactic responses to these chemokines in differentiated, but no t undifferentiated, NTera 2 cells. In addition, we show that the envelop glycoprotein from the T-cell-tropic human immunodeficiency virus 1 (HIV-1) strain IIIB is a CD4-independent, dose-dependent inhibitor of the binding of stromal cell-derived factor 1 to its receptor, CXCR4.

CONCLUSIONS

These data support recent findings that members of the chemokine family, including CCR5 and LESTR/Fusin (CXCR4), function as coreceptors in combination with CD4 for HIV-1 invasion. This is the first report of functional expression of chemokine receptors on human neurons. Furthermore, our studies provide for direct CD4-independent association of the viral envelope protein of the HIV-1 strain III with the chemokine receptor CXCR4.

Polyclonal antiidiotypic antibodies mimicking gp120 of HIV-1

Rabbit antiidiotypic antibodies (Ab2) were produced against anti-HIV-1 antibody 0.5 beta (Ab1), which binds to gp120 of HIV-1 and shows virus-neutralizing activity. The Ab2 bound specifically to the Ab1 and their binding to Ab2 was inhibited by a recombinant fragment of gp120 (PB1) or a peptide (residues 301-324 of gp120), both expressing the Ab1-defined epitope. The Ab2 induced in rats antiantiidiotypic antibodies (Ab3) that were Ab1-like in their binding reactivities to PB1, native gp120 or peptide and shared idiotopes with the Ab1. However, the Ab2 did not induce virus-neutralizing Ab3, probably a reflection of the low avidity of the Ab3 as compared to the Ab1.

Monoclonal anti-idiotypic antibodies that mimic the epitope on gp120 defined by anti-HIV-1 monoclonal antibody 0.5 beta

OBJECTIVE

To develop effective, specific and safe anti-idiotypic antibody (Ab2) vaccines against HIV-1.

DESIGN

Murine monoclonal Ab2 were generated against anti-HIV-1 antibody 0.5 beta (Ab1), which binds to gp120, neutralizes HIV-1 and inhibits virus-induced syncytia formation.

METHODS

Mice were immunized with Ab1, and Ab2 were produced from immunized mice by the hybridoma technique. The Ab2 were characterized in vitro, injected into rabbits, and the anti-anti-idiotypes (Ab3) induced in the rabbits were analyzed for binding and antiviral reactivities by enzyme-linked immunosorbent assay, p24gag release and syncytia formation assays.

RESULTS

Seven Ab2 bound to the antigen-combining site of Ab1, one of which (UD7) induced Ab3 in rabbits that were Ab1-like in their binding reactivities to PB1 (recombinant gp120 fragment) or peptides of gp120, and shared idiotypes with the Ab1. Crude Ab3-containing sera specifically and effectively neutralized the virus.

CONCLUSION

Monoclonal Ab2 UD7 has potential as a vaccine against HIV-1.

Replication of a macrophage-tropic strain of human immunodeficiency virus type 1 (HIV-1) in a hybrid cell line, CEMx174, suggests that cellular accessory molecules are required for HIV-1 entry

To investigate the mechanism underlying one aspect of the cellular tropism of human immunodeficiency virus type 1 (HIV-1), we used a macrophage-tropic isolate, 89.6, and screened its ability to infect a number of continuous cell lines. HIV-1 (89.6) was able to replicate robustly in a T-cell/B-cell hybrid line, CEMx174, while it replicated modestly or not at all in either of its parents, one of which is the CD4-positive line CEM.3. Analysis by transfection of a molecular clone, a virus uptake assay, and polymerase chain reaction all provided strong evidence that the block to HIV-1(89.6) replication in the CEM.3 line lies at the level of cellular entry. These results were complemented by preparing a CD4-expressing derivative of the B-cell parent, 721.174, and demonstrating that it is permissive for productive HIV-1(89.6) replication. Given these experimental findings, we speculate that there exist cellular accessory factors which facilitate virus entry and infection in CD4-positive cells. Furthermore, these cellular accessory factors may be quite virus strain specific, since not all macrophage-tropic strains of HIV-1 were able to replicate in the CEMx174 hybrid cell line. This experimental model provides a system for the identification of one or more of these putative cellular accessory factors.

Facial asymmetry in superior oblique muscle palsy

Facial asymmetry is an underrecognized association or sequela of torticollis in congenital or very early onset superior oblique muscle palsy, which when present in an adult, helps to confirm chronicity and prevent unnecessary neurologic evaluation. Nineteen cases of superior oblique muscle palsy were studied prospectively. Of 12 unilateral palsies presenting in adulthood, 9 were considered congenital by history and 7 (77%) of these had facial asymmetry. Large vertical fusional vergence amplitudes and torticollis, on review of childhood photographs, confirmed the early onset of the palsy in each facial asymmetry patient. In addition, two children presenting at age 18 months and 3 years of age with constant head tilting had facial asymmetry. If torticollis is corrected before maturation of the facial structure, resolution of the asymmetry may occur.

Design and synthesis of a CD4 beta-turn mimetic that inhibits human immunodeficiency virus envelope glycoprotein gp120 binding and infection of human lymphocytes

Poor bioavailability, rapid degradation, antigenicity, and high cost often limit the use of proteinaceous pharmaceuticals. One goal of structural biochemistry is the reduction of complex molecules to small functional units that are amenable to high-resolution structural analysis and rapid modification. The dissection of complex proteins into small synthetic conformationally restricted components is an important step in the design of low molecular weight nonpeptides that mimic the activity of the native protein. We have developed a reverse-turn mimetic system to explore peptide and protein structure-function relationships. We now report the design and synthesis of a small molecule (M(r) 810, as its trifluoroacetate salt), water soluble, proteolytically stable mimetic of residues Gln40-Thr45 of the complementarity-determining 2-like region of CD4. This mimetic has a low micromolar Kd for human T-lymphotropic virus type IIIB gp120 and reduces syncytium formation.

Anti-idiotypic antibodies against anti-CD4 antibodies MT151 and OKT4A

Anti-idiotypic antibodies (Ab2) binding to the antigen-combining site of other antibodies may functionally and even structurally mimic antigen. Ab2 to antibodies directed against the lymphocyte CD4 receptor for human immunodeficiency virus type 1 (HIV-1) may mimic the receptor and therefore inhibit viral infectivity. We have produced Ab2 against monoclonal anti-CD4 receptor antibodies (Ab1). The Ab1 strongly inhibit HIV-1 binding to the receptor. Six monoclonal rat Ab2 and two polyclonal rabbit Ab2 were produced against the Ab1 MT151 and nine monoclonal Ab2 against the Ab1 OKT4A. These Ab2 bound only to Ab1 and not to a panel of nine unrelated murine monoclonal antibodies (MAbs). The Ab2 completely inhibited the binding of the homologous Ab1 to CD4-positive target cells, and recombinant soluble CD4 inhibited binding of Ab2 to Ab1. Thus, the Ab2 seemed to mimic the Ab1-binding site of the CD4 receptor, although the results of inhibition assays did not exclude steric hindrance of antibody-combining sites. However, none of the 17 Ab2 bound to gp120 of HIV-1 envelope or inhibited syncytia formation between cells infected and uninfected with HIV-1. These results suggest that the Ab2 do not mimic the HIV-1 binding site of the CD4 receptor. They further suggest that the Ab1 may not bind within the virus-binding site of the CD4 receptor.

A monoclonal antibody against the platelet fibrinogen receptor contains a sequence that mimics a receptor recognition domain in fibrinogen

The binding of fibrinogen to its platelet receptor, the glycoprotein IIb-IIIa complex, is mediated, in part, by an Arg-Gly-Asp (RGD) sequence within the fibrinogen A alpha chain. PAC1 is an IgM-kappa murine monoclonal antibody that binds to the platelet fibrinogen receptor, and its binding is inhibited by both fibrinogen and RGD-containing peptides. To identify the regions of PAC1 that interact with the fibrinogen receptor, we determined the mRNA sequences of PAC1 immunoglobulin heavy and light chain variable regions. Five out of the six complementarity-determining regions (CDRs) of PAC1 had entirely germline sequences with no regions of similarity to fibrinogen. However, CDR3 of the PAC1 heavy chain (H-CDR3) was very large and unique due to the insertion of a novel D region segment. H-CDR3 contained a sequence, Arg-Tyr-Asp (RYD), that, if present in the proper conformation, might behave like the RGD sequence in fibrinogen. A 21-residue synthetic peptide encompassing the H-CDR3 region inhibited fibrinogen-dependent platelet aggregation as well as the binding of PAC1 (Ki = 10 microM) and fibrinogen (Ki = 5 microM) to activated platelets. The RYD region of H-CDR3 appeared to be central to its function, because substitution of the tyrosine with glycine increased the inhibitory potency of the peptide by 10-fold, while replacing the tyrosine with D-alanine or inverting the RYD sequence sharply reduced the inhibitory potency. Thus, the linear sequence, RYD, within H-CDR3 of PAC1 appears to mimic the RGD receptor recognition sequence in fibrinogen. This type of immunologic approach could be useful in studying the structural basis of other receptor-ligand interactions.

Pre-B-cell leukemia with a t(8; 14) and a t(14; 18) translocation is preceded by follicular lymphoma

We have performed gene rearrangement studies on the leukemic blasts of a patient with acute pre-B-cell leukemia. The patient had a 5 year history of follicular lymphoma, which developed into acute pre-B-cell leukemia. The leukemic blasts revealed a karyotype with two translocations, t(8; 14) and t(14; 18), characteristic for Burkitt's lymphoma and follicular lymphoma. The cells are TdT positive, do not possess surface immunoglobulin, and they show immunoglobulin gene rearrangement. The mu heavy chain and kappa light chain constant (C mu and C kappa) loci are deleted, while the gamma and lambda light chain constant (C gamma and C lambda) region genes are rearranged. Both alleles of the heavy chain joining segment (JH) are rearranged on chromosome 14q+, one of them with the bcl-2 oncogene from chromosome 18. The breakpoint of the t(14; 18) translocation occurs in the major breakpoint cluster region in the 3' untranslated region of bcl-2. On chromosome 8 a c-myc rearrangement was mapped immediately 5' to the c-myc first exon in a region involved in sporadic Burkitt lymphoma. The data are consistent with our previous hypothesis on the evolution of B-cell malignancies: a rare pre-B cell develops a t(14; 18) translocation during immunoglobulin VDJ joining that results in an expansion of a follicular lymphoma clone carrying an activated bcl-2 gene. Within the clone of pre-B cells a second translocation, t(8; 14), occurs during heavy chain isotype switching that results in the deregulation of the c-myc involved in the translocation.

Actinomycosis in the acquired immunodeficiency syndrome-related complex

The first case, to our knowledge, of cervicofacial actinomycosis arising in a patient with evidence of infection by the human T-cell lymphotrophic virus type III, the causal agent of the acquired immunodeficiency syndrome, is reported. Clinical uncertainty often exists in cases of actinomycosis due to the relative rarity of the disease, a clinical presentation that is compatible with a host of neoplastic and other infectious disorders, and difficulty in obtaining absolute bacteriologic documentation. Computed tomography was of interest in this case, since the radiographic findings could be correlated with pathophysiologic changes characteristic of this uncommon infection.

Heterogeneity of chromosome 22 breakpoint in Philadelphia-positive (Ph+) acute lymphocytic leukemia

In chronic myelogenous leukemias (CML) with the t(9;22)(q34;q11) chromosome translocation the breakpoints on chromosome 22 occur within a 5.8-kilobase segment of DNA referred to as "breakpoint cluster region" (bcr). The same cytogenetically indistinguishable translocation occurs in approximately 10% of patients with acute lymphocytic leukemias (ALL). In this study we have investigated the chromosome breakpoints in several cases of ALL carrying the t(9;22) translocation. In three of five cases of ALL we found that the bcr region was not involved in the chromosome rearrangement and that the 22q11 chromosome breakpoints were proximal (5') to the bcr region at band 22q11. In addition, we observed normal size bcr and c-abl transcripts in an ALL cell line carrying the t(9;22) translocation. We conclude, therefore, that if c-abl is inappropriately expressed in ALL cells without bcr rearrangements, the genetic mechanism of activation must be different from that reported for CML.

Infection by the retrovirus associated with the acquired immunodeficiency syndrome. Clinical, biological, and molecular features

Peripheral mononuclear cells from more than 160 persons from groups at risk for the acquired immunodeficiency syndrome (AIDS) have yielded AIDS-associated retroviruses (ARV). Antibodies to ARV can also be found in these risk groups. Antibody-negative, virus-positive persons have been identified with early infection or possible viremia with immune complex formation. Established lines of human T and B cells, monocytes, and promyelocytes have been infected with ARV. Moreover, infectious virus has been recovered from macrophages cultured from the blood of some persons with AIDS. The cytopathic effects of ARV in T cells is associated with the accumulation of unintegrated viral forms in the infected cells. The ARV has also been isolated from plasma, serum, saliva, semen, urine, cerebrospinal fluid, and brain tissue. All these results reflect the wide host range of ARV and support its role in neurologic abnormalities seen in some patients. Molecular studies of independent ARV isolates indicate a polymorphism of nucleotide sequences, particularly in the viral envelope region. All these features place ARV in the lentivirus subfamily of human retroviruses.

Phenotypic and functional analysis of B cell lines from patients with multiple myeloma

We characterized phenotypic and functional properties of B cell lines obtained from patients with multiple myeloma to determine how well they conform to particular stages of B cell differentiation. This information is a prerequisite for using such lines as tools for studying B cell growth and the regulation thereof. Two lines, GM1312 and GM1500, expressed B1 and Ia, determinants on early B cells, but expressed little, if any, T10, a determinant expressed on plasma cells. By contrast, B1 and Ia were poorly expressed on two other lines, GM2132 and U266. T10 was expressed on GM2132 but not on U266. Using a reverse hemolytic plaque assay, we also assessed the numbers of cells actively secreting immunoglobulin (IgSCs) in such cultures to provide a functional marker of B cell differentiation. We observed consistently higher numbers of IgSCs in cultures of GM2132 than in GM1500 and GM1312. These phenotypic and functional markers were stable over several months. The data suggest that such cell lines represent early (GM1312, GM1500) and later stages (GM2132, U266) of B cell differentiation, although all lines were derived from patients with multiple myeloma.

Ph1-positive acute leukemia with a 17q;21q translocation

Chromosome studies on the neoplastic cells of an adult patient with poorly differentiated acute leukemia revealed two Ph1-positive subpopulations, with and without a 17q;21q (q22;q22) translocation. The breakpoints appeared to be the same as in the 8;21 and 15;17 translocations of acute mytelogenous leukemia (AML) and acute promyelocytic leukemia (APL), emphasizing the significance of rearrangements involving these sites in the pathogenesis of acute leukemia. Terminally, there was clonal evolution, with the new predominant subline having an additional translocation, 1q;19q, resulting in trisomy for most of 1q and, apparently, additional selective advantage.

Immune interferon and leukocyte-conditioned medium induce normal and leukemic myeloid cells to differentiate along the monocytic pathway

Conditioned medium from phytohemagglutinin-stimulated human leukocytes contains a factor that can induce promyelocytic cell lines and certain acute myelogenous leukemia cells to differentiate along the monocytic pathway. In this report, we show that immature myeloid cells from normal bone marrow or the peripheral blood of patients with chronic myelogenous leukemia can be induced to differentiate to monocyte-like cells by immune gamma interferon (IFN gamma). We have identified IFN gamma as the predominant differentiation factor contained in the conditioned medium. Purified or recombinant IFN gamma, but not various preparations of IFN alpha or beta, can induce monocytic differentiation in myeloid cells. In cultures containing conditioned medium, the cells fail to continue myeloid maturation, and are induced to express monocyte markers and functions, such as monocyte-specific surface antigens, HLA-DR antigens, Fc receptors for monomeric immunoglobulins, nonspecific esterase, and the ability to mediate antibody-dependent, cell-mediated cytotoxicity. Even myeloid cells as mature as metamyelocytes or band cells can be induced by IFN gamma to undergo monocyte differentiation, but monocyte-specific or HLA-DR antigens are not induced in mature neutrophils. These findings reveal a previously unknown, specific function of human IFN gamma and offer new insights to the regulation of monocyte recruitment and differentiation during a virus infection or immune response.