Biomedical subjects

O Narayan

Publications and source records attributed to O Narayan.

At least 55 records · Page 3Linked to original sources

PubMed1998

Neurovirulent simian immunodeficiency virus induces calbindin-D-28K in astrocytes.

Astrocyte activation has been postulated to be a major contributor to functional changes in the brain of AIDS patients. We assessed astrocyte activation in the simian immunodeficiency virus (SIV) model. Four groups of macaque brains were examined: uninoculated controls, animals inoculated with virus that did not cause disease, animals inoculated with virus that caused AIDS but did not cause encephalitis, and animals with SIV encephalitis. We examined expression of calbindin-D-28K, a calcium binding protein that is upregulated in astrocytes during excitotoxic events, as well as glial fibrillary acidic protein (GFAP). The presence of calbindin in astrocytes was confirmed by double-labeling using confocal microscopy. Increases in calbindin staining were most apparent in the white matter, but increases in GFAP staining were most apparent in middle layers of the cerebral cortex. Six of the seven animals with SIV encephalitis had calbindin immunoreactive astrocytes in the subcortical white matter, corpus callosum, internal capsule, cerebral peduncle, pontine white matter, and cerebellar white matter. Very rarely, a few, very lightly calbindin-immunoreactive astrocytes were present in the uninoculated control brains. The increase in calbindin expression by astrocytes in SIV encephalitis suggests that these cells are subject to calcium toxicity. In uninoculated control macaques, and in macaques inoculated with virus that did not cause disease, GFAP-immunoreactive astrocytes were present throughout the subcortical white matter and in layer I, but very few were found in layers III-V of the cerebral cortex. Two animals that died of AIDS without encephalitis had somewhat higher numbers of GFAP immunoreactive astrocytes in middle cortical layers. In seven animals that received passaged neurovirulent virus and developed both AIDS and encephalitis, the number of GFAP-immunoreactive astrocytes in middle cortical layers was high, indicating widespread astrocyte activation.

Animals↗

PubMed1998

Fractionator analysis shows loss of neurons in the lateral geniculate nucleus of macaques infected with neurovirulent simian immunodeficiency virus.

Infection of macaques with neurovirulent strains of simian immunodeficiency virus (SIVmac) is an experimental model for the neurological manifestations of AIDS. Loss of neurons has been reported in the cerebral cortex following immunodeficiency viral infection, but thalamic structures which may contribute to electrophysiological changes and neurological deficits have not been examined. In this study, the lateral geniculate nucleus (LGN) of macaques inoculated with macrophage-tropic, neurovirulent virus SIVmac239 (R71 and 17E) was examined for neuron loss using the optical fractionator method. Estimates of the number of neurons in the P layers of the lateral geniculate nucleus of age-matched control macaques ranged from 1.0 to 1.3 x 10(6), while the number of neurons in SIV infected macaques ranged from 0.8 to 1.1 x 10(6), reflecting neuron loss of up to 28%. Neuron loss was not observed in the magnocellular layer. The total number of glia and glial density were unchanged. Loss of neurons in the lateral geniculate nucleus was correlated with the pattern of neuropathological changes. Neuron loss was most severe in animals with encephalitis concentrated in the brain stem and subcortical white matter and was less apparent in animals with diffuse encephalitis. Neuron loss in the lateral geniculate nucleus did not explain changes observed in the visual evoked potential, which was severely affected in two animals which showed a loss of 24 and 26%, while it was normal in a third animal which showed neuron loss of 28%.

Animals↗

PubMed1998

Nucleotide substitutions in the long terminal repeat are not required for development of neurovirulence by simian immunodeficiency virus strain mac.

The question of whether consensus nucleotide substitutions in the long terminal repeat (LTR) region of simian immunodeficiency virus strain mac (SIVmac) are important for neurovirulence was investigated in this report. Brains and lymph nodes from two macaques that developed AIDS and encephalitis following inoculation with two strains of neurovirulent SIVmac, and from one animal with AIDS but no neurological disease after inoculation with non-neurovirulent SIVmac239 were used. The 5' LTR regions from neurovirulent SIVmacR71/17E and SIVmac7F-Lu were amplified, cloned and sequenced and these sequences were compared to the LTRs amplified from three regions of the respective encephalitic brains and lymph nodes from macaques inoculated with each virus. The SIVmac7F-Lu and SIVmacR71/17E viruses had zero and three consensus substitutions, respectively, in the U3, R and U5 regions of the LTR compared to that of SIVmac239. The only consensus substitution in the LTR-gag region of the genome was a T to C change at position 829 within the tRNA binding site. The sequences amplified from the brain and lymph nodes of the two animals with AIDS and encephalitis were identical. This single common substitution in this region of the virus genome, the T to C substitution at position 829, was also found in the LTRs isolated from the brain and lymphoid organs from the macaque inoculated with SIVmac239. The virtual identity in nucleotide sequences in the LTR of the neurovirulent and non-neurovirulent viruses and in CNS and lymph tissues of animals inoculated with the viruses suggests that the LTR has no effect on the tissue tropisms of the viruses.

Amino Acid Sequence↗

PubMed1998

Common themes of antibody maturation to simian immunodeficiency virus, simian-human immunodeficiency virus, and human immunodeficiency virus type 1 infections.

Characterization of virus-specific immune responses to human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) is important to understanding the early virus-host interactions that may determine the course of virus infection and disease. Using a comprehensive panel of serological assays, we have previously demonstrated a complex and lengthy maturation of virus-specific antibody responses elicited by attenuated strains of SIV that was closely associated with the development of protective immunity. In the present study, we expand these analyses to address several questions regarding the nature of the virus-specific antibody responses to pathogenic SIV, SIV/HIV-1 (SHIV), and HIV-1 infections. The results demonstrate for the first time a common theme of antibody maturation to SIV, SHIV, and HIV-1 infections that is characterized by ongoing changes in antibody titer, conformational dependence, and antibody avidity during the first 6 to 10 months following virus infection. We demonstrate that this gradual evolution of virus-specific antibody responses is independent of the levels of virus replication and the pathogenicity of the infection viral strain. While the serological assays used in these studies were useful in discriminating between protective and nonprotective antibody responses during evaluation of vaccine efficacy with attenuated SIV, these same assays do not distinguish the clinical outcome of infection in pathogenic SIV, SHIV, or HIV-1 infections. These results likely reflect differences in the immune mechanisms involved in mediating protection from virus challenge compared to those that control an established viral infection, and they suggest that additional characteristics of both humoral and cellular responses evolve during this early immune maturation.

Animals↗

PubMed1998

Rhesus macaques infected with macrophage-tropic simian immunodeficiency virus (SIVmacR71/17E) exhibit extensive focal segmental and global glomerulosclerosis.

We previously showed that inoculation of rhesus macaques with molecularly cloned lymphocytetropic simian immunodeficiency virus (SIVmac239) results in SIV-associated nephropathy (SIVAN) and that the glomerulosclerotic lesions were associated with the selection of macrophagetropic (M-tropic) variants (V. H. Gattone et al., AIDS Res. Hum. Retroviruses 14:1163-1180, 1998). In the present study, seven rhesus macaques were inoculated with M-tropic SIVmacR71/17E, and the renal pathology was examined at necropsy. All SIVmacR71/17E-infected macaques developed AIDS, and most developed other systemic complications, including SIV-induced encephalitis and lentivirus interstitial pneumonia. There was no correlation between the length of infection (42 to 97 days), circulating CD4(+) T-cell counts, and renal disease. Of the seven macaques inoculated with SIVmacR71/17E, five developed significant mesangial hyperplasia and expansion of matrix and four were clearly azotemic (serum urea nitrogen concentration of 40 to 112 mg/dl). These same five macaques developed focal segmental to global glomerulosclerotic lesions. Increased numbers of glomerular CD68(+) cells (monocytes/macrophages) were found in glomeruli but not the tubulointerstitium of the macaques inoculated with SIVmacR71/17E. All macaques had glomerular deposits of immunoglobulin G (IgG), IgM, and tubuloreticular inclusions, and six of seven had IgA deposition. However, there was no correlation between the presence of circulating anti-SIVmac antibodies, immunoglobulin deposition, and glomerular disease. Tubulointerstitial infiltrates were mild, with little or no correlation to azotemia, while microcystic tubules were evident in those with glomerulosclerosis or azotemia. The four most severely affected macaques were positive for diffuse glomerular immunostaining for viral core p27 antigen, and there was intense staining in the glomeruli of the two macaques with the most severe glomerulosclerosis. Viral sequences were isolated from glomerular and tubulointerstitial fractions from macaques with severe glomerulosclerosis but only from the tubulointerstitial compartment of those that did not develop glomerulosclerosis. Interviral recombinant viruses generated with env sequences isolated from glomeruli confirmed the M-tropic nature of the virus found in the glomeruli. The correlation between the increased number of CD68(+) cells (monocytes/macrophages) in the glomeruli, the localization of p27 antigen in the glomeruli, and the glomerular pathology confirms and extends our previous observations of an association between glomerular infection and infiltration by M-tropic virus and SIVAN.

AIDS-Associated Nephropathy↗

PubMed1998

Oral immunization of macaques with attenuated vaccine virus induces protection against vaginally transmitted AIDS.

The chimeric simian-human immunodeficiency virus SHIVKU-1, bearing the envelope of human immunodeficiency virus type 1 (HIV-1), causes fulminant infection with subtotal loss of CD4(+) T cells followed by development of AIDS in intravaginally inoculated macaques and thus provides a highly relevant model of sexually transmitted disease caused by HIV-1 in human beings. Previous studies using this SHIV model had shown that the vpu and nef genes were important in pathogenesis of the infection, and so we deleted portions of these genes to create two vaccines, DeltavpuDeltanefSHIV-4 (vaccine 1) and DeltavpuSHIVPPc (vaccine 2). Six adult macaques were immunized subcutaneously with vaccine 1, and six were immunized orally with vaccine 2. Both viruses caused infection in all inoculated animals, but whereas vaccine 1 virus caused only a nonproductive type of infection, vaccine 2 virus replicated productively but transiently for a 6- to 10-week period. Both groups were challenged 6 to 7 months later with pathogenic SHIVKU-1 by the intravaginal route. All four unvaccinated controls developed low CD4(+) T-cell counts (<200/microliter) and AIDS. The 12 vaccinated animals all became infected with SHIVKU-1, and two in group 1 developed a persistent productive infection followed by development of AIDS in one. The other 10 have maintained almost complete control over virus replication even though spliced viral RNA was detected in lymph nodes. This suppression of virus replication correlated with robust antiviral cell-mediated immune responses. This is the first demonstration of protection against virulent SHIV administered by the intravaginal route. This study supports the concept that sexually transmitted HIV disease can be prevented by parenteral or oral immunization.

AIDS Vaccines↗

PubMed1998

Simian-human immunodeficiency virus (SHIV) containing the nef/long terminal repeat region of the highly virulent SIVsmmPBj14 causes PBj-like activation of cultured resting peripheral blood mononuclear cells, but the chimera showed No increase in virulence.

SIVsmmPBj14 is a highly pathogenic lentivirus which causes acute diarrhea, rash, massive lymphocyte proliferation predominantly in the gastrointestinal tract, and death within 7 to 14 days. In cell culture, the virus has mitogenic effects on resting macaque T lymphocytes. In contrast, SIVmac239 causes AIDS in rhesus macaques, generally within 2 years after inoculation. In a previous study, replacement of amino acid residues 17 and 18 of the Nef protein of SIVmac239 with the corresponding amino acid residues of the Nef protein of SIVsmmPBj14 yielded a PBj-like virus that caused extensive activation of resting T lymphocytes in cultures and acute PBj-like disease when inoculated into pig-tailed macaques. This study suggested that nef played a major role in both processes. In this study, we replaced the nef/long terminal repeat (LTR) region of a nonpathogenic simian-human immunodeficiency virus (SHIV), SHIVPPc, with the corresponding region from SIVsmmPBj14 and examined the biological properties of the resultant virus. Like SIVsmmPBj14, SHIVPPcPBjnef caused massive stimulation of resting peripheral blood mononuclear cells (PBMC), which then produced virus in the absence of extraneous interleukin 2. However, when inoculated into macaques, the virus failed to replicate productively or cause disease. Thus, while these results confirmed that the nef/LTR region of SIVsmmPBj14 played a major role in the activation of resting PBMC, duplication of the cellular activation process in macaques may require a further interaction between nef and the envelope glycoprotein of simian immunodeficiency virus because SHIV, containing the envelope of human immunodeficiency virus type 1, failed to cause activation in vivo.

Animals↗

PubMed1998

Gradient of microglial activation in the brain of SIV infected macaques.

Brains of macaques inoculated with macrophage-tropic, neurovirulent virus 7F, with lymphocyte-tropic SIV mac239, or with dual-tropic SIVmac239/1yE, were examined for microglial activation, astrocyte activation, apoptosis and neuron loss. The brain one animal inoculated with neurovirulent virus 7f showed massive microglial activation as assessed by expression of the major histo-compatibility complex class II (MHC-II). In this animal very numerous, large microglial nodules expressing MHC-II were concentrated in the basal pons and internal capsule. These microglial nodules contained cells undergoing apoptosis detected by in situ end labeling of fragmented DNA. In this animal, neuron loss was apparent near the microglial nodules. In the animals inoculated with SIVmac239 or SIVmac239/17E, pathologic changes such as perivascular cuffing and formation of microglial nodules were absent. However, increased expression of MHC-11 by microglial cells was also concentrated in white matter of the basal pons, midbrain and internal capsule. These results indicate the microglial activation in SIV-infected macaques follows a ventral to dorsal gradient regardless of viral tropism. These results also show that the type and severity of neuropathological changes in SIV-infected macaques is highly dependent on the tropism of the inoculated virus.

Animals↗

PubMed1998

Neuroinvasion by ovine lentivirus in infected sheep mediated by inflammatory cells associated with experimental allergic encephalomyelitis.

Maedi Visna Virus (MVV) is a prototypic lentivirus that causes infection only in cells of macrophage lineage, unlike the primate lentiviruses which infect both CD4+ T lymphocytes and macrophages. In primates, the earliest viral invasion is associated with the ability of the virus to infect and activate T cells which convey virus to the brain. Infected monocytes in blood rarely cause CNS infection in absence of activation of CD4+ T cells. In the face of lack of infection or activation of T cells by MVV in sheep, the question arises, how does MVV gain access to the brain to cause the classical lesions of visna? In previous studies on experimental induction of visna, sheep were inoculated with virus directly in the brain. In this study, we asked whether neuroinvasion by MVV would occur if sheep were inoculated with virus in a non-neural site. Nine sheep were inoculated intratracheally and all developed systemic infection when examined 3 weeks later. At this time, five were injected intramuscularly with brain white matter homogenized in Freund's complete adjuvant to induce EAE. None of the four animals inoculated with virus alone developed CNS infection despite typical lentiviral infection in lungs, lymphoid tissues and blood-borne mononuclear cells. In contrast, all five of the sheep injected with brain homogenate developed infection in the brain. Virus was produced by macrophages associated with the EAE lesions. This study illustrated that both activated T cells specific for antigen in the CNS and infected macrophages are essential for lentivirus neuropathogenesis.

Animals↗

PubMed1998

Auditory brainstem responses in a Rhesus Macaque model of neuro-AIDS.

Nine rhesus macaques (Macaca mulatta) were inoculated with a combination of two passaged strains of SIVmac (R71 and 17E), both of which are known to be neurovirulent. Auditory brainstem responses (ABRs) were recorded at regular intervals from these animals both before and after inoculation. Increases in ABR peak and interpeak latency were observed corresponding to progression of SIV disease. Post-inoculation increases in latency were observed for all five peaks of the ABR and for interpeak intervals I-V and III-V. The largest increases in latency were associated with end-stage disease. Within 14 weeks of inoculation, all but two animals developed end-stage simian AIDS and were euthanized. Histopathological examination revealed multifocal lesions in the cerebral gray and white matter as well as in the auditory structures of the brainstem. In most animals, ABR changes were accompanied by evidence of underlying neuropathology. However, cases of severe neuropathology with no ABR abnormalities and vice versa were also noted. Though in a much shorter time frame, SIVmac R71/17E produced both physiological and histopathological abnormalities similar to those associated with HIV disease in humans. These results further support the SIVmac R71/17E infected rhesus macaque as an animal model of HIV related neurological disease in humans.

AIDS Dementia Complex↗

PubMed1997

Infected macaques that controlled replication of SIVmac or nonpathogenic SHIV developed sterilizing resistance against pathogenic SHIV(KU-1).

Twenty macaques were used to evaluate the ability of nonpathogenic SIV(mac) or nonpathogenic chimeric SIV-HIV (SHIV) to induce protection in macaques against superinfection with a pathogenic variant of SHIV (SHIV(KU-1)) originally containing the tat, rev, vpu, and env of HIV-1 (strain HXB2) in a genetic background of SIV(mac)239. Specifically, three macaques inoculated with molecularly cloned, macrophage-tropic SIV(mac)LG1 developed an early systemic infection but recovered with only traces of SIV(mac) DNA in visceral lymphoid tissues. These animals were then inoculated parenterally with pathogenic SHIV(KU-1). All three animals resisted infection with SHIV(KU-1), as indicated by lack of virus recovery and absence of SHIV-specific env and vpu sequences in the visceral lymphoid tissues and multiple regions in the CNS. We also examined the ability of five macaques that had been inoculated with nonpathogenic SHIV (NP-SHIV) to withstand challenge with the pathogenic SHIV(KU-1). Like the SIV(mac)LG1-inoculated macaques, these animals also resisted SHIV(KU-1) challenge as judged by the inability to recover infectious virus, normal CD4+ T cell counts, and the absence of SHIV(KU-1) signature sequences in the lymph node tissue. Thus, eight of eight animals that developed control over primary lentivirus infections had also developed resistance to infection with pathogenic SHIV(KU-1). Three groups of macaques were used as controls for this study. The first group consisted of six macaques inoculated with SHIV(KU-1) alone. All animals developed viremia, showed severe loss of CD4+ T cells within 4 weeks, and succumbed to AIDS within 6 months. The second group of three macaques was inoculated first with SHIV(KU-1) and inoculated later with uncloned, neurovirulent SIV(mac)7F-Lu. A third group of three macaques was inoculated with SIV(mac)7F-Lu followed by inoculation with SHIV(KU-1). PCR analyses using oligonucleotide primers specific for the SIV or HIV env revealed that macaques from the last two groups had widespread infection with both SHIV(KU-1) and SIV(mac), indicating that animals that failed to control productive replication of either SHIV(KU-1) or SIV(mac)7F-Lu could not resist superinfection with the other virus. These data indicate that sterilizing immunity against the virulent SHIV could be induced in animals that had experienced an immunizing infection. Moreover, the divergence of the envelope glycoprotein of the protective avirulent and virulent challenge virus suggests that a single vaccine could protect against infection with a virus containing a different envelope glycoprotein.

Animals↗

PubMed1997

Texture analysis of cerebral white matter in SIV-infected macaque monkeys.

Image texture analysis is used in a wide variety of applications in medical research. Neurovirulent simian immunodeficiency virus (SIV) infection in monkeys is considered a good model for HIV-1 infection in humans and causes neuropathological changes in white matter which can include diffuse myelin pallor, subtle white matter astrocytosis, perivascular macrophage infiltrates, and microglial nodules with multinucleated giant cells. The ability of image texture analysis to quantify these changes was evaluated. Sections of thionin-stained brain tissue from eight male rhesus macaques ranging in age from 42-59 months were used. Four animals served as controls and four animals were infected with neurovirulent SIVmac239/17E-R71 by bone marrow inoculation. Images of cerebral white matter were captured and analyzed by calculating 13 textural features based on statistical analysis of spatial co-occurrence matrices. Statistical analysis of the results included multiple comparisons using the Newman-Keuls multiple range test. The effect of variation in background illumination used at image acquisition was also evaluated. Ten of the 13 textural features used in this study successfully discriminated between tissue from control and SIV-infected animals and were consistent with independent neuropathological assessment. Three textural features were highly sensitive to variation in background illumination and found not useful in this application.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Characterization of the pathogenic KU-SHIV model of acquired immunodeficiency syndrome in macaques.

By animal-to-animal passage in macaques we derived a pathogenic chimeric simian-human immunodeficiency virus (SHIV) that caused CD4+ T cell loss and AIDS in pigtail macaques and used it to inoculate 20 rhesus and pigtail macaques by the intravaginal and intravenous routes. On the basis of the outcome of infection and patterns of CD4+ T cell loss and viral load, disease was classified into four patterns: acute, subacute, chronic, and nonprogressive infection. During the study period, 15 of the 20 animals developed fatal disease, including AIDS, encephalitis, pneumonia, and severe anemia. Opportunistic pathogens identified in these animals included Pneumocystis, cytomegalovirus, Cryptosporidium, Toxoplasma, and Candida. No single parameter by itself predicted outcome, although a combination of low CD4+ T cell counts in blood, high plasma virus levels, and presence of autoantibodies to red blood cells reliably predicted a fatal outcome. Five animals (25%) died within 3 months of inoculation and constituted the group with acute disease, whereas the nine animals (45%) with subacute disease died between 3 and 8 months postinoculation. This 70% mortality within 8 months is significantly shorter than in HIV-1-infected human beings, of whom 70% develop fatal disease a decade after infection. SHIV infection in macaques provides a useful model with which to evaluate antiviral strategies, combining all the advantages of the SIVmac system, yet using a virus bearing the envelope gene of HIV-1.

AIDS-Related Opportunistic Infections↗

PubMed1997

A cell-free stock of simian-human immunodeficiency virus that causes AIDS in pig-tailed macaques has a limited number of amino acid substitutions in both SIVmac and HIV-1 regions of the genome and has offered cytotropism.

We have examined both the sequence changes in the LTR, gag, vif, vpr, vpx, tat, rev, vpu, env, and nef genes and the cell tropism of a cell-free stock of chimeric simian-human immunodeficiency virus (SHIV) isolated from the cerebrospinal fluid of a pig-tailed macaque (PNb) that developed AIDS. This virus (SHIVKU-1) is highly pathogenic when inoculated into other macaques. DNA sequence analysis of PCR-amplified products revealed a total of 5 nucleotide changes in the LTR while vif had 2 consensus amino acid changes. The gag, vif, and vpx had no consensus amino acid substitutions, whereas vpr had 1 consensus substitution. The tat and rev genes of the HXB2 region of SHIVKU-1 had 2 and 1 consensus amino acid changes, respectively. The vpu gene of the HXB2 region of SHIV, which originally had an ACG at the beginning of the gene, reverted to an initiation ATG codon and in addition contained a consensus amino acid substitution at position 69 of this protein. As expected, the majority of the nucleotide substitutions were found in the env and nef genes. Thirteen and 5 amino acid changes were predicted for the corresponding Env and Nef proteins, respectively. In addition, one-third of the env gene clones isolated from the SHIVKU-1 stock had a 5-amino-acid deletion in the V4 region. Using three independent assays, we determined that the changes in the SHIVKU-1 were associated with an increase in the efficiency of replication in macrophages. The strikingly few consensus changes in the virus suggest that conversion of this virus to one capable of causing AIDS in pig-tailed macaques was associated with relatively few changes in the viral envelope and/or accessory genes. These results will provide the basis for the development of a pathogenic, molecular clone of SHIV capable of causing AIDS in pig-tailed macaques.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Early treatment with 9-(2-phosphonylmethoxyethyl)adenine reduces virus burdens for a prolonged period in SIV-infected rhesus macaques.

We evaluated the effects of a reverse transcriptase inhibitor, 9-(2-phosphonylmethoxyethyl)adenine (PMEA), on simian immunodeficiency virus (SIV) infection in rhesus macaques (Macaca mulatta). Four macaques were given PMEA (20 mg/kg) subcutaneously on days 1 and 2 and inoculated with virus on day 2. Drug treatment was continued for 30 consecutive days, after which the virus burdens and course of infection were monitored for a further 6 months. Four control animals that did not receive PMEA all developed high virus burdens and two of the four developed clinical disease. In contrast, virus burdens remained low in three of the four macaques treated with PMEA and all four remained healthy. Our results show that suppression of virus replication early in infection can result in reduced virus burdens for a much longer period.

Adenine↗

PubMed1997

Plasmas from lymphocyte- and macrophage-tropic SIVmac-infected macaques have antibodies with a broader spectrum of virus neutralization activity in macrophage versus lymphocyte cultures.

We examined plasma from macaques infected with three different phenotypes of SIVmac for their ability to neutralize the infectivity of homologous and heterologous virus in lymphocyte (CEMx174 cells or normal rhesus macaque peripheral blood lymphocytes) or normal rhesus macaque macrophage (Mphi) cultures. Similar to previous findings, we observed that some plasmas failed to neutralize or poorly neutralized the infectivity of SIVmac239 and SIVmac251(<1:20 plasma dilution) in lymphocyte cultures. In contrast, when primary rhesus Mphi cultures were used as the indicator cells, the same plasmas neutralized both viruses at high dilutions (1:200 to 1:20,000). Neutralization of virus infectivity by the various plasmas was confirmed by SIV core antigen capture assays. We excluded the possibility that this differential neutralization in Mphi was related to the differences in the ability of the virus strain to replicate in these two cell types by demonstrating that the replication efficiency of SIVmac251 in CEMx174 cells, PBMC, and Mphi cultures was very similar. The role of Fc receptors on the Mphi surface in the clearance of the virus-antibody complexes was also excluded since similar neutralizing results were obtained using whole plasmas, purified IgG antibodies, and purified Fab fragments derived from the IgG fraction of these plasmas. The mechanism of virus neutralization in Mphi does not appear to involve blocking of virus entry into the cells since radiolabeled virus reacted with anti-SIV antibodies was taken up by rhesus Mphi as efficiently as virus reacted with normal antibody. DNA of the neutralized virus was identified in the Mphi cultures, but virus replication, as evidenced by accumulation of viral protein products, was not detectable so long as the antibodies were present in the medium. Removal of the antibodies resulted in a resumption of virus replication in the Mphi. These results indicate that virus infectivity can be efficiently neutralized by antibodies in Mphi cultures by a mechanism that is fundamentally different from that in lymphocyte cultures.

Animals↗

PubMed1997

Significance of macrophage tropism of SIV in the macaque model of HIV disease.

Microglia, alveolar macrophages, and Langerhans cells are representatives of cells of macrophage lineage that are susceptible to infection with HIV-1 and they play important roles in the pathogenesis of AIDS dementia, lymphoid interstitial pneumonia, and systemic viral invasion from mucosal surfaces, respectively. In contrast, elimination of CD4+ T cells with resultant development of immunosuppression and AIDS is thought to be reflective of the exclusive tropism of the virus for CD4+ T cells. Examination of these concepts in macaques infected with molecularly cloned strains of SIVmac suggested that all strains of the virus are both macrophage- and lymphocyte-tropic and that all aspects of pathogenesis including loss of CD4+ T cells are dependent on infection in both cell types. However, viral clones that caused productive lytic infection in macrophages were less virulent than those which caused persistent nonproductive infection. The former caused subclinical and even immunizing infections, whereas the latter caused activation and productive infection in CD4+ T cells, AIDS, and systemic infection, even after inoculation of the virus on mucosal surfaces. If these findings on SIVmac are relevant to HIV-1 disease, then demonstration that HIV-1 isolates are macrophage-tropic probably does not necessarily correlate with their pathogenic potential.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Neuropathogenesis of chimeric simian/human immunodeficiency virus infection in pig-tailed and rhesus macaques.

We recently reported that a chimeric simian/human immunodeficiency virus (SHIVKU-1) developed in our laboratory caused progressive depletion of CD4+ T lymphocytes and AIDS within 6 months of inoculation into pig-tailed macaques (M. nemestrina). None of the pig-tailed macaques showed productive SHIV infection in the central nervous system (CNS). In this report, we show that by further passage of the pathogenic virus in rhesus macaques [M. mulatta], we have derived a new strain of SHIV (SHIVKU-2) that has caused AIDS and productive CNS infection in 3 of 5 rhesus macaques infected with the virus. Productive replication of SHIV in the CNS was clearly shown by high infectivity titers and p27 protein levels in brain homogenates, and in 2 of the 3 rhesus macaques this was associated with disseminated, nodular, demyelinating lesions, including focal multinucleated giant cell reaction, largely confined to the white matter. These findings were reminiscent of HIV-1 associated neurological disease, and our immunohistochemical and in situ hybridization data indicated that the neuropathological lesions were associated with the presence of SHIV-specific viral antigens and nucleic acid respectively. However, the concomitant reactivation of opportunistic infections in these macaques suggested that such pathogens may have influenced the replication of SHIV in the CNS, or modified the neuropathological sequelae of SHIV infection in the rhesus species, but not in pig-tailed macaques. Our findings in the two species of macaques highlight the complexities of lentiviral neuropathogenesis, the precise mechanisms of which are still elusive.

Acquired Immunodeficiency Syndrome↗