Neurotoxicity of Macrophages 117
NEUROTOXICITY OF MACROPHAGES INFECTED BY HIVI M A R C TARDIEU, CHRISTIANE HERY, and SYLVIANE P E U D E N I E R Laboratoire de Neurovirologie et Neuroimmunologie, Universit~ Paris XI UFR Kremlin Bic~tre
INTRODUCTION Central nervous system (CNS) lesions are frequently observed during Human Immunodeficiency Virus (HIV) infection. Clinical manifestations are highly variable ranging from no symptom to psycho-motor slowing and to severe cognitive and motor disturbances. The variation in intensities of clinical symptoms is particularly true after materno-fetal transmission of the virus. Thus, the vast majority of infected children have biological evidence of infection of their central nervous system but only 20% of the patients have very severe encephalopathy and absence of brain growth (Blanche et al., 1991). Other children have a normal initial development and brain growth, although some of them develop subsequently a mental retardation. The pathogenicity of HIVl-induced encephalopathy is still unknown. Recent papers have described a loss of neurons in the brains of adult HIVl-infected patients (Ketzler et al., 1990; Everall et al., 1991), Such a neuronal destruction had been previously described in the brains of very severely affected children (Epstein et al., 1988). On the other hand, viral antigens are frequently found within the brain of patients who died of AIDS, but have a restricted distribution. Signs of viral replication can be observed only in macrophages, whereas astrocytes and neurons harbor very little if any, viral information, as judged by immuno-cytochemistry and in situ hybridization (Wiley et al., 1986; Vazeux et al., 1987; Price et al., 1988). This selective tropism of HIV1 for brain macrophages has been confirmed in vitro (Watkins et al., 1990). Recently, we observed that the infected brain macrophages are not mature microglial cells but either monocytes which could cross the blood-brain barrier or specialized perivascular microglial cells able to phagocytose infected monocytes or even free virus (Peudenier et al., 1991). The mechanism of neuronal loss during HIV infection is unclear and several hypothesis could be made which will be discussed successively. COULD A LOW GRADE I N F E C T I O N OF NEURONS OR ASTROCYTES BE RESPONSIBLE FOR CELL DEATH? Because a low grade and persistent viral infection is very difficult to rule out by techniques utilizing post mortem brain sections, several studies have directly tested the susceptibility of cultured neurons and astrocytes to HIV1. Their results remain controversial (Cheng-Mayer et al., 1987; Chiodi et al., 1987; Christofinis et al., 1987; Corresponding author: M. TARDIEU, b~timent INSERM, H6pital Bic~tre, 80 avenue du General Leclerc, 94275 Le Kremlin Bic~tre Cedex. Abbreviation used: CNS: central nervous system; HIV: human immunodeficiency virus. Key Words: Human Immunodeficiency Virus, Macrophages, Neural cells cultures, Neurotoxicity. Cell Biology and Copyright © 1992
Toxicology, Vol. 8, No. 3, pp. Princeton Scientific Publishing ISSN: 0742-2091
117-121 Co., Inc.
118
Tardieu et al.
Dewhurst et al., 1987; Wigdahl et al., 1987; Dewhurst et al., 1988; Harouse et al., 1989; Kunsch et al., 1989; Chesebro et al., 1990). A cytopathic effect was rarely observed and a fully productive persistent infection with HIV1 was difficult to establish, except for some experimental systems using either very high titers of virus or transfection to introduce HIV1 into astrocytic cells. Most studies, moreover, used continuous cell lines of either glial or neuronal origin and did not precisely define the tested cells by antigenic markers. In a recent work, we observed that human neurons and astrocytes in primary cultures from cortex or spinal cord were resistant to HIV1 infection, an observation to be related to the absence of CD4 antigen on their surface and of mRNA CD4 in their cytoplasm (Peudenier et al., 1991; Tardieu et al., 1992). It remains possible that specific clones of HIV1 using an entry mechanism independent of the CD4 antigen, a mode of internalization already suggested, replicated better in neurons and astrocytes than the clones we have tested. Neurons and astrocytes do not appear to be a frequent target for HIV infection and a persistent low grade infection of these cells do not appear to be the usual mechanism of neural lesions. CNS cells lesion could then depend on the infection of adjacent macrophages which acted either through the secretion of soluble factors active on distant neurons and astrocytes, or directly after adhesion to neurons and astrocytes. COULD SOLUBLE FACTORS SECRETED BY HIV1 I N F E C T E D M A C R O P H A G E S INDUCE CNS C E L L S LESIONS? A role for different soluble factors has been proposed (Brenneman et al., 1988; Dreyer et al., 1990; Kaiser et al., 1990; Giulian et al., 1990; Lipton et al., 1991; Sabatier et al., 1991). Two viral peptides, gpl20 and tat, modify the survival of rodent neurons or astrocytes, the former protein acting on calcium channels and the latter on membrane polarization. Another still undefined soluble factor, secreted by infected mononuclear phagocytes (from the permanent U937 cell line), alters the survival of chick and rat neurons (Giulian et al., 1990). This factor differs from viral peptides, cytokines or free radicals and acts by way of N-methyl-D-aspartate receptors and not of calcium channels or membrane polarization. Since we had the opportunity to test directly human embryonic neurons and astrocytes in primary cultures instead of rodent neural cells, we initially used a similar experimental approach (Tardieu et al., 1992). Supernatants of HIV 1-infected U937 cells were harvested at day 4 post infection and transferred on human neural cell cultures on their 10th day post-plating. During five different experiments, cells were observed for up to 21 days, and individual cultures were fixed at different times and stained with anti-neurofilament antibodies. No morphological alteration of neurons and astrocytes was induced by the tested supernatants. During two subsequent experiments, HIVl-infected U937 cells were cultured in a double chamber system with a 0.4 lam porous membrane separating them from the neural cell culture. Here again, no astrocytic or neuronal lesion was observed. Finally, HIVl-infected lymphocytes, which actively replicated the virus and secreted viral products, were co-cultured with neural cells and no cytopathic effect was induced.
Neurotoxicity of Macrophages 119
Human neurons and astrocytes appear to be more resistant than chicken and rat neurons to incubation with supernatant of infected macrophages. This could be due to species-related differences in membranes or receptors, but also to technical differences. Whereas Giulian et al. tested supernatants of chronically infected U937 cells (Giulian et al., 1990), we used supernatants of freshly infected cells, suggesting that the neurotoxic factor isolated in the former case might not be secreted during the first three weeks of infection. Since neurons and astrocytes are unaltered in vitro by either HIV1 infection or supernatants of HIVl-infected monocytic cells, and since HIVl-infected brain macrophages expressed antigenic markers of monocytes, as we previously observed (Peudenier et al., 1991), we decided to further study the interaction between CNS cells and HIV 1-infected monocytes. COULD A DIRECT ADHERENCE OF HIV1 INFECTED LYMPHOCYTES OR MONOCYTES INDUCE CNS C E L L S LESIONS? Freshly isolated human monocytes or lymphocytes (either uninfected or HIV 1-infected) or U937 cells were co-cultured with primary human CNS cell culture. Adhesion of monocytes from HIV 1 negative donors to neurons and aslrocytes occurred within hours of co-culture, whereas adhesion of U937 cells was slower and much lower, except if they are HIV-infected. Finally, freshly isolated lymphocytes either uninfected or H1Vl-infected did not adhere to neurons and aslrocytes. HIV 1-infected U937 monocytic cells, after adhesion to neural cells, induced large plaques of necrosis surrounding them. This cytopathic effect began at the time of viral replication (day 16 post infection). Its intensity depended on that of viral replication, and its range was identical to the region of diffusion of viral antigens, as judged by immunocytochemistry. The cytopathic effect was not dependent on the release of free radicals. It could not be induced by cytokines or cytokine-stimulated U937 cells. It seems likely that this cytopathic effect depends on the release of viral antigens either within the site of adherence itself or within a close range of the astrocyte membrane, since at least four different viral polypeptides were detected within the progressively expanding necrotic area (Tardieu et al., 1992). However, we could not exclude that other factors such as that described by Giulian et al. could also participate in cell destruction (Giulian et al., 1990). A role for cytokines appears less likely in view of the relative resistance of the tested cells to TNFc~ or ILl, although they could participate in the induction of necrosis if secreted at the site of adhesion. CONCLUSION Neuronal astrocytes and perhaps oligodendrocytic lesions occur during the course of HIV infection of CNS cells. Most of the results suggest that these lesions are indirectly induced by infected macrophages, probably monocytes, present in the brain. Two mechanisms of neurotoxicity have been studied to date, one testing soluble factors present in supernatant of infected monocytes and the other the direct effect of adhering HIVinfected monocytes to neurons and astrocytes. These two mechanisms are not mutually
120 Tardieu et al.
exclusive. They both indicate a major role for monocytes in the induction of brain lesions and the crucial importance of the neurotoxic approach in the study of HIV induced encephalopathy.
REFERENCES BLANCHE, S., TARDIEU, M., DULIEGE, A.M., ROUZIOUX, C., LEDEIST, F., KUKUNAGA, K., CANIGLIA, M., DEBRE, M., JACOMET, C., MESSIAH, A., and GRISCELLI, C. (1990). Longitudinal study of 94 symptomatic infants with materno-foetal HIV infection: evidence for a bimodal expression of clinical and biological symptoms. Am. J. Dis. Childh. 144:1210-1215. BRENNEMAN, D.E., WESTBROOK, G.L., FITZGERALD, S.P., ENNIST, D.L., ELKINS, K.L., RUFF, M.R., and PRET, C.B. (1988). Neuronal killing by the envelope protein of HIV and its prevention by vasoactive intestinal peptide. Nature 335:639-642. CHENG-MAYER, C., RUTKA, J.T, ROSENBLUM, M.L., MCHUGH, T., STITES, D.P., and LEVY, J.A. (1987). Human immunodeficiency virus can productively infect cultured human glial cells. Proc. Natl Acad Sci USA pp. 3526-3530. CHESEBRO, B., BULLER, R., PORTIS, J., and WEHRLY, K. (1990) Failure of human immunodeficiency virus entry and infection in CD4-positive human brain and skin cells. J. Virol. 64:215-221. CHIODI, F., FUERSTENBERG, S., GILDUNDG, M., ASJO, B., and FENYO, E.M. (1987). Infection of brain derived cells with the human immunodeficiency virus. J .Virol. 61:1244-1247. CHRISTOFINIS, G., PAPADAKI, L., SATTENTAU, Q., FERNS, R.B., and TEDDER, R. (1987). HIV replicates in cultured human brain ceils. AIDS 1:229-234. DEWHURST, S., SAKAI, K., BRESSER, J., STEVENSON, M., EVINGER-HODGES, M.J., and VOLSKI, D.J. (1987). Persistent productive infection of human glial cells by human immunodeficiency virus (HIV) and by infectious molecular clones of HIV. J. Virol. 61:3774-3782. DEWHURST, S., SAKAI, K., ZHANG, K.S., WASIAK, A., and VOLSKI, D.J. (1988). Establishment of human gtial cells chronically infected with the human immunodeficiency virus.Virology. 162:151-159. DREYER, E.B., KAISER, P.K., OFFERMANN, J.T., and LIPTON, S.A. (1990). HIV-1 coat protein neurotoxicity prevented by calcium channel antagonists. Science. 248:364-367. EPSTEIN, L.G. and SHARER, L.R. (1988). Neurology of the human immunodeficiency virus infection of the nervous system in children. In "Aids and the nervous system." (Rosenblum M.L., Levy R.M., Bredessen D.E., eds.) New York, Raven Press, 79-101. EVERALL, I.P., LUTHERT, P.J., LANTOS, P.L. (1991). Neuronal loss in the frontal cortex in HIV infection. Lancet. 337:1119-1121. GIULIAN, D., VACA, K., and NOONAN, C.A. (1990). Secretion of neurotoxins by mononuclear phagocytes infected with HIVI. Science 250:1593-1596. HAROUSE, J.M., KUNSCH, C., HARTLE, H.T., LAUGHLIN, M.A., HOXIE, J.A., WIGDAL, B., and GONZALEZ-SCARANO. (1989). CD4-independent infection of human neural cells by human immunodeficiency virus type 1. J. Virol. 63:2527-2533. KAISER, P.K., OFFERMANN, B.A., and LIPTON, S.A. (1990). Neuronal injury due to HIV1 envelope protein is blocked by anti-gpl20 antibodies but not by anti-CD4 antibodies. Neurology 40:1757-1761. KETZLER, S., WEISS, S., HAUG, H, and BUDKA, H. (1990). Loss of neurons in the frontal cortex in AIDS brains. Acta Neuropathol (Berl). 80:92-94. KUNSCH, C., HARTLE, H.T., and WIGDAHL, B. (1989) Infection of human fetal dorsal root ganglion glial cells with human immonodeficiency virus type 1 involves an entry mechanism independent of the CD4 T4A epitope. J. Virol. 64:5054-5061. LIPTON, S.A. (1991). Calcium channel antagonists and human immunodeficiency virus coat protein-mediated neuronal injury. Ann Neurol. 30:110-114. PEUDENIER, S., HERY, C., MONTAGNIER, L., and TARDIEU, M. (1991). Human microglial cells: Characterization in cerebral tissue and in primary culture, and study of their susceptibility to HIV1 infection. Ann. Neurol. 29:152-161.
Neurotoxicity of Macrophages 121 PEUDENIER, S., FIERY, C., NG, K.H., and TARDIEU, M. (1991). HIV-receptor within the brain: study of CD4 and MHCII on human neurons, astrocytes and microglial cells. Res. Virol. 142:145-149. PRICE, R.W., BREW, B., SIDTIS, J., ROSENBLUM, M., SCHECK, A.C., and CLEARY, P. (1988). The brain in AIDS. Central Nervous System HIV1 infection and AIDS dementia complex. Science 239:586-592. SABATIER, J.M., VIVES, E., MABROUK, K., BENJOUAD, A., ROCHAT, H., DUVAL, A., HUE, B., and BAHRAOUI, E. (1991). Evidence for neurotoxic activity of tat from human immunodeficiency virus type 1. J. Virol. 65:961-967. TARDIEU, M., HERY, C., PEUDENIER, S., BOESPFLUG, O., and MONTAGNIER, L. (1992). HIVl-infected monocytic cells can destroy human neural cells after cell-to-cell adhesion. Ann. Neurol: 32:11-17. VAZEUX, R.M., BROUSSE, N., JARRY, A., HENIN, D., MARCHE, C., VEDRENNE, C., MIKOL, J., WOLFF, J., MICHON, C., ROZENBAUM, W., BUREAU, J.F., MONTAGNIER, L., and BRAHIC, M. (1987). AIDS subacute encephalitis. Identification of HIV-infected cells. Am. J. Pathol. 126:403-410. WATKINS, B.A., DORN, H.H., KELLY, W.B., ARMSTRONG R.C., POTTS, B.J., MICHAELS, F., KUFTA, C.V., and DUBOIS-DALCQ, M. (1990). Specific tropism of HIV1 for microglial cells in primary human brain cultures. Science 249:549-553. WIGDAHL, B., GUYTON, R.A., and SARIN, P.S. (1987). Human immuno-deficiency virus infection of the developing human nervous system. Virology 159:440-445. WILEY, C.A., SCHRIER, R.D., MELSON, J.A., LAMPERT, P.W., and OLDSTON, M.B.A. (1986). Cellular localization of human immunodeficiency virus infection within the brain of acquired immune deficiency syndrome patients. Proc. Natl. Acad. Sci. USA 83:70897093.
NEUROTOXICITY OF MACROPHAGES INFECTED BY HIVI M A R C TARDIEU, CHRISTIANE HERY, and SYLVIANE P E U D E N I E R Laboratoire de Neurovirologie et Neuroimmunologie, Universit~ Paris XI UFR Kremlin Bic~tre
INTRODUCTION Central nervous system (CNS) lesions are frequently observed during Human Immunodeficiency Virus (HIV) infection. Clinical manifestations are highly variable ranging from no symptom to psycho-motor slowing and to severe cognitive and motor disturbances. The variation in intensities of clinical symptoms is particularly true after materno-fetal transmission of the virus. Thus, the vast majority of infected children have biological evidence of infection of their central nervous system but only 20% of the patients have very severe encephalopathy and absence of brain growth (Blanche et al., 1991). Other children have a normal initial development and brain growth, although some of them develop subsequently a mental retardation. The pathogenicity of HIVl-induced encephalopathy is still unknown. Recent papers have described a loss of neurons in the brains of adult HIVl-infected patients (Ketzler et al., 1990; Everall et al., 1991), Such a neuronal destruction had been previously described in the brains of very severely affected children (Epstein et al., 1988). On the other hand, viral antigens are frequently found within the brain of patients who died of AIDS, but have a restricted distribution. Signs of viral replication can be observed only in macrophages, whereas astrocytes and neurons harbor very little if any, viral information, as judged by immuno-cytochemistry and in situ hybridization (Wiley et al., 1986; Vazeux et al., 1987; Price et al., 1988). This selective tropism of HIV1 for brain macrophages has been confirmed in vitro (Watkins et al., 1990). Recently, we observed that the infected brain macrophages are not mature microglial cells but either monocytes which could cross the blood-brain barrier or specialized perivascular microglial cells able to phagocytose infected monocytes or even free virus (Peudenier et al., 1991). The mechanism of neuronal loss during HIV infection is unclear and several hypothesis could be made which will be discussed successively. COULD A LOW GRADE I N F E C T I O N OF NEURONS OR ASTROCYTES BE RESPONSIBLE FOR CELL DEATH? Because a low grade and persistent viral infection is very difficult to rule out by techniques utilizing post mortem brain sections, several studies have directly tested the susceptibility of cultured neurons and astrocytes to HIV1. Their results remain controversial (Cheng-Mayer et al., 1987; Chiodi et al., 1987; Christofinis et al., 1987; Corresponding author: M. TARDIEU, b~timent INSERM, H6pital Bic~tre, 80 avenue du General Leclerc, 94275 Le Kremlin Bic~tre Cedex. Abbreviation used: CNS: central nervous system; HIV: human immunodeficiency virus. Key Words: Human Immunodeficiency Virus, Macrophages, Neural cells cultures, Neurotoxicity. Cell Biology and Copyright © 1992
Toxicology, Vol. 8, No. 3, pp. Princeton Scientific Publishing ISSN: 0742-2091
117-121 Co., Inc.
118
Tardieu et al.
Dewhurst et al., 1987; Wigdahl et al., 1987; Dewhurst et al., 1988; Harouse et al., 1989; Kunsch et al., 1989; Chesebro et al., 1990). A cytopathic effect was rarely observed and a fully productive persistent infection with HIV1 was difficult to establish, except for some experimental systems using either very high titers of virus or transfection to introduce HIV1 into astrocytic cells. Most studies, moreover, used continuous cell lines of either glial or neuronal origin and did not precisely define the tested cells by antigenic markers. In a recent work, we observed that human neurons and astrocytes in primary cultures from cortex or spinal cord were resistant to HIV1 infection, an observation to be related to the absence of CD4 antigen on their surface and of mRNA CD4 in their cytoplasm (Peudenier et al., 1991; Tardieu et al., 1992). It remains possible that specific clones of HIV1 using an entry mechanism independent of the CD4 antigen, a mode of internalization already suggested, replicated better in neurons and astrocytes than the clones we have tested. Neurons and astrocytes do not appear to be a frequent target for HIV infection and a persistent low grade infection of these cells do not appear to be the usual mechanism of neural lesions. CNS cells lesion could then depend on the infection of adjacent macrophages which acted either through the secretion of soluble factors active on distant neurons and astrocytes, or directly after adhesion to neurons and astrocytes. COULD SOLUBLE FACTORS SECRETED BY HIV1 I N F E C T E D M A C R O P H A G E S INDUCE CNS C E L L S LESIONS? A role for different soluble factors has been proposed (Brenneman et al., 1988; Dreyer et al., 1990; Kaiser et al., 1990; Giulian et al., 1990; Lipton et al., 1991; Sabatier et al., 1991). Two viral peptides, gpl20 and tat, modify the survival of rodent neurons or astrocytes, the former protein acting on calcium channels and the latter on membrane polarization. Another still undefined soluble factor, secreted by infected mononuclear phagocytes (from the permanent U937 cell line), alters the survival of chick and rat neurons (Giulian et al., 1990). This factor differs from viral peptides, cytokines or free radicals and acts by way of N-methyl-D-aspartate receptors and not of calcium channels or membrane polarization. Since we had the opportunity to test directly human embryonic neurons and astrocytes in primary cultures instead of rodent neural cells, we initially used a similar experimental approach (Tardieu et al., 1992). Supernatants of HIV 1-infected U937 cells were harvested at day 4 post infection and transferred on human neural cell cultures on their 10th day post-plating. During five different experiments, cells were observed for up to 21 days, and individual cultures were fixed at different times and stained with anti-neurofilament antibodies. No morphological alteration of neurons and astrocytes was induced by the tested supernatants. During two subsequent experiments, HIVl-infected U937 cells were cultured in a double chamber system with a 0.4 lam porous membrane separating them from the neural cell culture. Here again, no astrocytic or neuronal lesion was observed. Finally, HIVl-infected lymphocytes, which actively replicated the virus and secreted viral products, were co-cultured with neural cells and no cytopathic effect was induced.
Neurotoxicity of Macrophages 119
Human neurons and astrocytes appear to be more resistant than chicken and rat neurons to incubation with supernatant of infected macrophages. This could be due to species-related differences in membranes or receptors, but also to technical differences. Whereas Giulian et al. tested supernatants of chronically infected U937 cells (Giulian et al., 1990), we used supernatants of freshly infected cells, suggesting that the neurotoxic factor isolated in the former case might not be secreted during the first three weeks of infection. Since neurons and astrocytes are unaltered in vitro by either HIV1 infection or supernatants of HIVl-infected monocytic cells, and since HIVl-infected brain macrophages expressed antigenic markers of monocytes, as we previously observed (Peudenier et al., 1991), we decided to further study the interaction between CNS cells and HIV 1-infected monocytes. COULD A DIRECT ADHERENCE OF HIV1 INFECTED LYMPHOCYTES OR MONOCYTES INDUCE CNS C E L L S LESIONS? Freshly isolated human monocytes or lymphocytes (either uninfected or HIV 1-infected) or U937 cells were co-cultured with primary human CNS cell culture. Adhesion of monocytes from HIV 1 negative donors to neurons and aslrocytes occurred within hours of co-culture, whereas adhesion of U937 cells was slower and much lower, except if they are HIV-infected. Finally, freshly isolated lymphocytes either uninfected or H1Vl-infected did not adhere to neurons and aslrocytes. HIV 1-infected U937 monocytic cells, after adhesion to neural cells, induced large plaques of necrosis surrounding them. This cytopathic effect began at the time of viral replication (day 16 post infection). Its intensity depended on that of viral replication, and its range was identical to the region of diffusion of viral antigens, as judged by immunocytochemistry. The cytopathic effect was not dependent on the release of free radicals. It could not be induced by cytokines or cytokine-stimulated U937 cells. It seems likely that this cytopathic effect depends on the release of viral antigens either within the site of adherence itself or within a close range of the astrocyte membrane, since at least four different viral polypeptides were detected within the progressively expanding necrotic area (Tardieu et al., 1992). However, we could not exclude that other factors such as that described by Giulian et al. could also participate in cell destruction (Giulian et al., 1990). A role for cytokines appears less likely in view of the relative resistance of the tested cells to TNFc~ or ILl, although they could participate in the induction of necrosis if secreted at the site of adhesion. CONCLUSION Neuronal astrocytes and perhaps oligodendrocytic lesions occur during the course of HIV infection of CNS cells. Most of the results suggest that these lesions are indirectly induced by infected macrophages, probably monocytes, present in the brain. Two mechanisms of neurotoxicity have been studied to date, one testing soluble factors present in supernatant of infected monocytes and the other the direct effect of adhering HIVinfected monocytes to neurons and astrocytes. These two mechanisms are not mutually
120 Tardieu et al.
exclusive. They both indicate a major role for monocytes in the induction of brain lesions and the crucial importance of the neurotoxic approach in the study of HIV induced encephalopathy.
REFERENCES BLANCHE, S., TARDIEU, M., DULIEGE, A.M., ROUZIOUX, C., LEDEIST, F., KUKUNAGA, K., CANIGLIA, M., DEBRE, M., JACOMET, C., MESSIAH, A., and GRISCELLI, C. (1990). Longitudinal study of 94 symptomatic infants with materno-foetal HIV infection: evidence for a bimodal expression of clinical and biological symptoms. Am. J. Dis. Childh. 144:1210-1215. BRENNEMAN, D.E., WESTBROOK, G.L., FITZGERALD, S.P., ENNIST, D.L., ELKINS, K.L., RUFF, M.R., and PRET, C.B. (1988). Neuronal killing by the envelope protein of HIV and its prevention by vasoactive intestinal peptide. Nature 335:639-642. CHENG-MAYER, C., RUTKA, J.T, ROSENBLUM, M.L., MCHUGH, T., STITES, D.P., and LEVY, J.A. (1987). Human immunodeficiency virus can productively infect cultured human glial cells. Proc. Natl Acad Sci USA pp. 3526-3530. CHESEBRO, B., BULLER, R., PORTIS, J., and WEHRLY, K. (1990) Failure of human immunodeficiency virus entry and infection in CD4-positive human brain and skin cells. J. Virol. 64:215-221. CHIODI, F., FUERSTENBERG, S., GILDUNDG, M., ASJO, B., and FENYO, E.M. (1987). Infection of brain derived cells with the human immunodeficiency virus. J .Virol. 61:1244-1247. CHRISTOFINIS, G., PAPADAKI, L., SATTENTAU, Q., FERNS, R.B., and TEDDER, R. (1987). HIV replicates in cultured human brain ceils. AIDS 1:229-234. DEWHURST, S., SAKAI, K., BRESSER, J., STEVENSON, M., EVINGER-HODGES, M.J., and VOLSKI, D.J. (1987). Persistent productive infection of human glial cells by human immunodeficiency virus (HIV) and by infectious molecular clones of HIV. J. Virol. 61:3774-3782. DEWHURST, S., SAKAI, K., ZHANG, K.S., WASIAK, A., and VOLSKI, D.J. (1988). Establishment of human gtial cells chronically infected with the human immunodeficiency virus.Virology. 162:151-159. DREYER, E.B., KAISER, P.K., OFFERMANN, J.T., and LIPTON, S.A. (1990). HIV-1 coat protein neurotoxicity prevented by calcium channel antagonists. Science. 248:364-367. EPSTEIN, L.G. and SHARER, L.R. (1988). Neurology of the human immunodeficiency virus infection of the nervous system in children. In "Aids and the nervous system." (Rosenblum M.L., Levy R.M., Bredessen D.E., eds.) New York, Raven Press, 79-101. EVERALL, I.P., LUTHERT, P.J., LANTOS, P.L. (1991). Neuronal loss in the frontal cortex in HIV infection. Lancet. 337:1119-1121. GIULIAN, D., VACA, K., and NOONAN, C.A. (1990). Secretion of neurotoxins by mononuclear phagocytes infected with HIVI. Science 250:1593-1596. HAROUSE, J.M., KUNSCH, C., HARTLE, H.T., LAUGHLIN, M.A., HOXIE, J.A., WIGDAL, B., and GONZALEZ-SCARANO. (1989). CD4-independent infection of human neural cells by human immunodeficiency virus type 1. J. Virol. 63:2527-2533. KAISER, P.K., OFFERMANN, B.A., and LIPTON, S.A. (1990). Neuronal injury due to HIV1 envelope protein is blocked by anti-gpl20 antibodies but not by anti-CD4 antibodies. Neurology 40:1757-1761. KETZLER, S., WEISS, S., HAUG, H, and BUDKA, H. (1990). Loss of neurons in the frontal cortex in AIDS brains. Acta Neuropathol (Berl). 80:92-94. KUNSCH, C., HARTLE, H.T., and WIGDAHL, B. (1989) Infection of human fetal dorsal root ganglion glial cells with human immonodeficiency virus type 1 involves an entry mechanism independent of the CD4 T4A epitope. J. Virol. 64:5054-5061. LIPTON, S.A. (1991). Calcium channel antagonists and human immunodeficiency virus coat protein-mediated neuronal injury. Ann Neurol. 30:110-114. PEUDENIER, S., HERY, C., MONTAGNIER, L., and TARDIEU, M. (1991). Human microglial cells: Characterization in cerebral tissue and in primary culture, and study of their susceptibility to HIV1 infection. Ann. Neurol. 29:152-161.
Neurotoxicity of Macrophages 121 PEUDENIER, S., FIERY, C., NG, K.H., and TARDIEU, M. (1991). HIV-receptor within the brain: study of CD4 and MHCII on human neurons, astrocytes and microglial cells. Res. Virol. 142:145-149. PRICE, R.W., BREW, B., SIDTIS, J., ROSENBLUM, M., SCHECK, A.C., and CLEARY, P. (1988). The brain in AIDS. Central Nervous System HIV1 infection and AIDS dementia complex. Science 239:586-592. SABATIER, J.M., VIVES, E., MABROUK, K., BENJOUAD, A., ROCHAT, H., DUVAL, A., HUE, B., and BAHRAOUI, E. (1991). Evidence for neurotoxic activity of tat from human immunodeficiency virus type 1. J. Virol. 65:961-967. TARDIEU, M., HERY, C., PEUDENIER, S., BOESPFLUG, O., and MONTAGNIER, L. (1992). HIVl-infected monocytic cells can destroy human neural cells after cell-to-cell adhesion. Ann. Neurol: 32:11-17. VAZEUX, R.M., BROUSSE, N., JARRY, A., HENIN, D., MARCHE, C., VEDRENNE, C., MIKOL, J., WOLFF, J., MICHON, C., ROZENBAUM, W., BUREAU, J.F., MONTAGNIER, L., and BRAHIC, M. (1987). AIDS subacute encephalitis. Identification of HIV-infected cells. Am. J. Pathol. 126:403-410. WATKINS, B.A., DORN, H.H., KELLY, W.B., ARMSTRONG R.C., POTTS, B.J., MICHAELS, F., KUFTA, C.V., and DUBOIS-DALCQ, M. (1990). Specific tropism of HIV1 for microglial cells in primary human brain cultures. Science 249:549-553. WIGDAHL, B., GUYTON, R.A., and SARIN, P.S. (1987). Human immuno-deficiency virus infection of the developing human nervous system. Virology 159:440-445. WILEY, C.A., SCHRIER, R.D., MELSON, J.A., LAMPERT, P.W., and OLDSTON, M.B.A. (1986). Cellular localization of human immunodeficiency virus infection within the brain of acquired immune deficiency syndrome patients. Proc. Natl. Acad. Sci. USA 83:70897093.
