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Biomedical subjects

Jeffrey D Lifson

Publications and source records attributed to Jeffrey D Lifson.

17 recordsLinked to original sources
PubMed2003

CpG oligodeoxynucleotides protect normal and SIV-infected macaques from Leishmania infection.

Oligodeoxynucleotides containing CpG motifs (CpG ODNs) mimic microbial DNA and activate effectors of the innate immune response, which limits the spread of pathogens and promotes an adaptive immune response. CpG ODNs have been shown to protect mice from infection with intracellular pathogens. Unfortunately, CpG motifs that optimally stimulate humans are only weakly active in mice, mandating the use of nonhuman primates to monitor the activity and safety of "human" CpG ODNs in vivo. This study demonstrates that CpG ODN treatment of rhesus macaques significantly reduces the severity of the lesions caused by a challenge with Leishmania: Leishmania superinfection is common in immunocompromised hosts, particularly those infected with HIV. This study shows that PBMCs from HIV-infected subjects respond to stimulation with CpG ODNs. To determine whether CpG ODNs can protect retrovirus-infected primates, SIV-infected macaques were treated with CpG ODNs and then challenged with Leishmania: Both lesion size and parasite load were significantly reduced in the CpG-treated animals. These findings support the clinical development of CpG ODNs as immunoprotective agents in normal and HIV-infected patients.

Adjuvants, Immunologic↗
PubMed2003

Novel member of the CD209 (DC-SIGN) gene family in primates.

Two CD209 family genes identified in humans, CD209 (DC-SIGN) and CD209L (DC-SIGNR/L-SIGN), encode C-type lectins that serve as adhesion receptors for ICAM-2 and ICAM-3 and participate in the transmission of human and simian immunodeficiency viruses (HIV and SIV, respectively) to target cells in vitro. Here we characterize the CD209 gene family in nonhuman primates and show that recent evolutionary alterations have occurred in this family across primate species. All of the primate species tested, specifically, Old World monkeys (OWM) and apes, have orthologues of human CD209. In contrast, CD209L is missing in OWM but present in apes. A third family member, that we have named CD209L2, was cloned from rhesus monkey cDNA and subsequently identified in OWM and apes but not in humans. Rhesus CD209L2 mRNA was prominently expressed in the liver and axillary lymph nodes, although preliminary data suggest that levels of expression may vary among individuals. Despite a high level of sequence similarity to both human and rhesus CD209, rhesus CD209L2 was substantially less effective at binding ICAM-3 and poorly transmitted HIV type 1 and SIV to target cells relative to CD209. Our data suggest that the CD209 gene family has undergone recent evolutionary processes involving duplications and deletions, the latter of which may be tolerated because of potentially redundant functional activities of the molecules encoded by these genes.

Amino Acid Sequence↗
PubMed2003

Importance of B-cell responses for immunological control of variant strains of simian immunodeficiency virus.

The properties of three variants of cloned simian immunodeficiency virus strain 239 (SIV239) were compared. One strain (M5) lacked five sites for N-linked carbohydrate attachment in variable regions 1 and 2 (V1 and V2) of the gp120 envelope protein, one strain (DeltaV1-V2) completely lacked V1 and V2 sequences, and another (316) had nine mutations in the envelope that impart high replicative capacity for tissue macrophages. All three strains were capable of significant levels of fusion independent of CD4, and all three were considerably more sensitive to antibody-mediated neutralization than the parent strain from which they were derived. Upon experimental infection of rhesus monkeys, these three variant strains replicated to viral loads at peak height around day 14 that were indistinguishable from or only slightly less than those observed in monkeys infected with the parental SIV239 strain. Viral loads at the set point 20 to 50 weeks after infection, however, were more than 400- to 10,000-fold lower with the variant strains. Depletion of B cells around the time of infection with M5 resulted in less effective immunological control and much higher viral loads at the set point in two of three monkeys. The differences between SIV239 infection, where there is not effective immunological control, and SIVM5 infection, where there is effective immunological control, cannot be easily explained by differences in the inherent replicative capacity of the viruses; rather, they are more readily explained by differences in the effectiveness of the antibody response. These results suggest that resistance of SIV239 to antibody-mediated neutralization is very important for evading effective immunological control, for allowing continuous viral replication, for maintenance of moderate-to-high viral loads at set point, and for disease progression.

AIDS Vaccines↗
PubMed2003

Direct relationship between suppression of virus-specific immunity and emergence of cytomegalovirus disease in simian AIDS.

Although opportunistic infections like cytomegalovirus (CMV) are common sequelae of end-stage AIDS, the immune events leading to CMV reactivation in human immunodeficiency virus (HIV)-infected individuals are not well defined. The role of cellular and humoral CMV-specific immune responses in immune control of latent CMV infection was evaluated prospectively in a cohort of 11 simian immunodeficiency virus (SIV)-infected CMV-seropositive rhesus macaques, 6 of whom had histologic evidence of CMV disease at death. Macaques with CMV disease differed from macaques without CMV disease in having significantly higher levels of plasma SIV RNA and CMV DNA and significantly lower titers of anti-CMV binding antibodies (Abs) at the time of death. A significant decline in anti-CMV Abs and CMV-specific CD4(+) and CD8(+) T lymphocytes over time was observed in the macaques with CMV disease, but not in the macaques without CMV disease. Reduction in CMV-specific CD8(+) T lymphocytes and anti-CMV neutralizing Abs was significantly correlated with a decline in CMV-specific CD4(+) T lymphocytes. Although declines in CMV-specific T lymphocytes alone were sufficient for reactivation of low-level CMV viremia, high-level viremia (>1,000 copies of CMV DNA per ml of plasma) was observed when anti-CMV neutralizing and binding Abs had also declined. Thus, the occurrence of CMV reactivation-associated disease in AIDS is associated with suppression of both cellular and humoral CMV-specific immune responses. The underlying mechanism may be a dysfunction of memory B and CD8(+) T lymphocytes associated with SIV-induced impairment of CMV-specific CD4(+) T-cell help.

Animals↗
PubMed2003

Simian immunodeficiency virus infection in neonatal macaques.

Children with human immunodeficiency virus infection often have higher viral loads and progress to AIDS more rapidly than adults. Since the intestinal tract is a major site of early viral replication and CD4(+) T-cell depletion in adults, we examined the effects of simian immunodeficiency virus (SIV) on both peripheral and intestinal lymphocytes from 13 neonatal macaques infected with SIVmac239. Normal neonates had more CD4(+) T cells and fewer CD8(+) T cells in all tissues than adults. Surprisingly, neonates had substantial percentages of CD4(+) T cells with an activated, memory phenotype (effector CD4(+) T cells) in the lamina propria of the intestine compared to peripheral lymphoid tissues, even when examined on the day of birth. Moreover, profound and selective depletion of jejunum lamina propria CD4(+) T cells occurred in neonatal macaques within 21 days of infection, which was preceded by large numbers of SIV-infected cells in this compartment. Furthermore, neonates with less CD4(+) T-cell depletion in tissues tended to have higher viral loads. The persistence of intestinal lamina propria CD4(+) T cells in some neonates with high viral loads suggests that increased turnover and/or resistance to CD4(+) T-cell loss may contribute to the higher viral loads and increased severity of disease in neonatal hosts.

Animals↗
PubMed2003

Control of viremia and prevention of simian-human immunodeficiency virus-induced disease in rhesus macaques immunized with recombinant vaccinia viruses plus inactivated simian immunodeficiency virus and human immunodeficiency virus type 1 particles.

An effective vaccine against the human immunodeficiency virus type 1 (HIV-1) will very likely have to elicit both cellular and humoral immune responses to control HIV-1 strains of diverse geographic and genetic origins. We have utilized a pathogenic chimeric simian-human immunodeficiency virus (SHIV) rhesus macaque animal model system to evaluate the protective efficacy of a vaccine regimen that uses recombinant vaccinia viruses expressing simian immunodeficiency virus (SIV) and HIV-1 structural proteins in combination with intact inactivated SIV and HIV-1 particles. Following virus challenge, control animals experienced a rapid and complete loss of CD4(+) T cells, sustained high viral loads, and developed clinical disease by 17 to 21 weeks. Although all of the vaccinated monkeys became infected, they displayed reduced postpeak viremia, had no significant loss of CD4(+) T cells, and have remained healthy for more than 15 months postinfection. CD8(+) T-cell and neutralizing antibody responses in vaccinated animals following challenge were demonstrable. Despite the control of disease, virus was readily isolated from the circulating peripheral blood mononuclear cells of all vaccinees at 22 weeks postchallenge, indicating that immunologic control was incomplete. Virus recovered from the animal with the lowest postchallenge viremia generated high virus loads and an irreversible loss of CD4(+) T-cell loss following its inoculation into a naïve animal. These results indicate that despite the protection from SHIV-induced disease, the vaccinated animals still harbored replication-competent and pathogenic virus.

Animals↗
PubMed2003

Effect of humoral immune responses on controlling viremia during primary infection of rhesus monkeys with simian immunodeficiency virus.

Cellular immune responses mediated by CD8+ lymphocytes exert efficient control of virus replication during primary simian immunodeficiency virus (SIV) infection. However, the role that antibodies may play in the early control of virus replication remains unclear. To evaluate how antibody responses may affect virus replication during primary SIVmac infection, we depleted rhesus monkeys of B cells with anti-CD20 antibody. In normal rhesus monkeys immunized with tetanus toxoid, anti-CD20 treatment and resulting depletion of B cells inhibited the generation of antitetanus antibodies, while tetanus-specific T-cell responses were preserved. During the first 4 weeks after inoculation with SIVmac251, development of SIV-specific neutralizing antibody was delayed, and titers were significantly lower in B-cell-depleted monkeys than control-antibody-treated monkeys. Despite the lower neutralizing antibody titers, the levels of plasma SIV RNA and the linear slope of the decline seen in B-cell-depleted monkeys did not differ from that observed in monkeys treated with control antibody. However, beginning at day 28 after SIV infection, the B-cell-depleted monkeys showed a significant inverse correlation between neutralizing antibody titers and plasma virus level. These results suggest that the rapid decline of peak viremia that typically occurs during the first 3 weeks of infection was not significantly affected by SIV-specific antibodies. However, the inverse correlation between neutralizing antibodies and plasma virus level during the postacute phases of infection suggests that humoral immune responses may contribute to the control of SIV replication.

Animals↗
PubMed2003

Mucosal priming of simian immunodeficiency virus-specific cytotoxic T-lymphocyte responses in rhesus macaques by the Salmonella type III secretion antigen delivery system.

Nearly all human immunodeficiency virus (HIV) infections are acquired mucosally, and the gut-associated lymphoid tissues are important sites for early virus replication. Thus, vaccine strategies designed to prime virus-specific cytotoxic T lymphocyte (CTL) responses that home to mucosal compartments may be particularly effective at preventing or containing HIV infection. The Salmonella type III secretion system has been shown to be an effective approach for stimulating mucosal CTL responses in mice. We therefore tested DeltaphoP-phoQ attenuated strains of Salmonella enterica serovar Typhimurium and S. enterica serovar Typhi expressing fragments of the simian immunodeficiency virus (SIV) Gag protein fused to the type III-secreted SopE protein for the ability to prime virus-specific CTL responses in rhesus macaques. Mamu-A*01(+) macaques were inoculated with three oral doses of recombinant Salmonella, followed by a peripheral boost with modified vaccinia virus Ankara expressing SIV Gag (MVA Gag). Transient low-level CTL responses to the Mamu-A*01 Gag(181-189) epitope were detected following each dose of Salmonella. After boosting with MVA Gag, strong Gag-specific CTL responses were consistently detected, and tetramer staining revealed the expansion of Gag(181-189)-specific CD8(+) T-cell responses in peripheral blood. A significant percentage of the Gag(181-189)-specific T-cell population in each animal also expressed the intestinal homing receptor alpha4beta7. Additionally, Gag(181-189)-specific CD8(+) T cells were detected in lymphocytes isolated from the colon. Yet, despite these responses, Salmonella-primed/MVA-boosted animals did not exhibit improved control of virus replication following a rectal challenge with SIVmac239. Nevertheless, this study demonstrates the potential of mucosal priming by the Salmonella type III secretion system to direct SIV-specific cellular immune responses to the gastrointestinal mucosa in a primate model.

AIDS Vaccines↗
PubMed2003

Sites, mechanism of action and lack of reversibility of primate lentivirus inactivation by preferential covalent modification of virion internal proteins.

By exploiting the intrinsic chemistry of retroviruses, we have developed a novel method for generating whole inactivated virion vaccine immunogens with functional envelope glycoproteins. The method takes advantage of the fact that the internal proteins of retroviruses are adapted to the intracellular (reducing) environment, and have cysteine residues present in thiol-form (S-H), while the surface proteins of retroviruses (the envelope glycoproteins SU and TM) are adapted to the (oxidizing) environment of the extracellular milieu, and have their cysteines present as disulfides (S-S). Treatment of retroviral virions with appropriate mild oxidizing agents thus results in preferential covalent modification and functional inactivation of key S-H-containing internal viral proteins, such as the nucleocapsid (NC) protein, that are required for infectivity, while the envelope glycoproteins with their disulfide bonded cysteines remain unaffected. This treatment thus results in virions that do not retain detectable infectivity, but preserves the conformational and functional integrity of the envelope glycoproteins. We have extensively used the disulfide reagent 2,2'-dithiodipyridine (aldrithiol-2, AT-2) to inactivate HIV and SIV via this mechanism and such inactivated virions appear to be a promising vaccine immunogen based on macaque studies. We have biochemically characterized the targets and mechanisms of inactivation involved in AT-2 treatment of virions, and investigated the kinetics of inactivation. Although extremely unlikely under physiological conditions, reversibility of this type of inactivation is a theoretical concern. We have therefore conducted a series of in vitro experiments, in cell free systems and in cell culture, to evaluate this possibility. The results indicate that as judged by both biochemical and biological (infectivity) criteria, inactivation by AT-2 does not appear to be reversible under conditions likely to obtain in vivo.

2,2'-Dipyridyl↗
PubMed2002

The central nervous system as a reservoir for simian immunodeficiency virus (SIV): steady-state levels of SIV DNA in brain from acute through asymptomatic infection.

Latent reservoirs of human immunodeficiency virus (HIV) present significant challenges for eradicating HIV from infected persons, particularly reservoirs in the brain established during acute infection. A simian immunodeficiency virus (SIV)/macaque model of HIV dementia was used to show that viral DNA levels in the brain remained at constant levels from acute through asymptomatic infection, despite significant down-regulation of viral RNA in the brain after the acute phase of infection. Viral replication in the brain coincided with activation of macrophages and microglia in the central nervous system; down-regulation of viral replication coincided with increased infiltration of cytotoxic lymphocytes and reduced activation of macrophages and microglia in the brain. Comparison of viral genotypes in the central nervous system and peripheral blood mononuclear cells suggests that recrudescence of viral replication in brain occurs by reactivation of latent viral DNA. Latent virus in the brain must be considered in therapeutic strategies to eliminate HIV from infected persons.

Acute Disease↗
PubMed2002

SIV(mac) pathogenesis in rhesus macaques of Chinese and Indian origin compared with primary HIV infections in humans.

OBJECTIVE: To develop a SIV-rhesus macaque (Rh) model of AIDS that more closely approximates HIV pathogenesis in humans. DESIGN: The pathogenesis of SIV was compared in two different types of Rh, the Chinese (Ch) and Indian (Ind) subspecies. METHODS: Ch Rh and Ind Rh origin were identified genetically and infected with the SIV(mac)239 molecular clone. Plasma viral loads, depletion of intestinal lymphocytes with memory phenotype, humoral immune responses and CD4/CD8 cell ratios were compared during acute and steady-state periods of infection. RESULTS: Plasma viral loads from 7 days after infection through 240 days were significantly lower in Rh of Ch origin compared with Ind Rh. Viral loads in Ch Rh were closer to viral loads observed in untreated humans infected with HIV-1. Depletion of intestinal effector cells was less evident in SIV-infected Ch Rh compared with Ind Rh. An index of intestinal pathogenesis was devised that closely paralleled viral load and severity of infection. There were no rapid progressors to AIDS among 10 Ch Rh. In contrast, three of four Ind Rh progressed rapidly to AIDS. CONCLUSIONS: Compared with Ind Rh, SIV(mac) pathogenesis in Ch Rh was closer to HIV-1 infections in untreated adult humans. The differences were statistically significant. The Ch Rh subspecies is a suitable AIDS model and may have advantages over the rapid and highly pathogenic Ind Rh model. Moreover, Ind Rh supplies are limited and use of Ch Rh provides a new resource.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Activation of HIV-1 specific CD4 and CD8 T cells by human dendritic cells: roles for cross-presentation and non-infectious HIV-1 virus.

BACKGROUND: The CD4 T cells in mucosal subepithelia are the first cells to become infected during sexual transmission of HIV-1. Dendritic cells (DC) are located in the same area and are known to play a central role in antiviral immune responses. However, extensive viral replication, syncytia formation and cell death follows the interaction between T cells and DC previously exposed to HIV-1. Despite this, anti-HIV responses are generated that control viremia following acute infection. OBJECTIVE: The anti-HIV-1 cellular immune responses observed may be activated by sources other than productively infected DC. HIV-1 induces apoptosis both in cells it infects and in bystander cells. Furthermore, retroviral replication typically generates a predominance of defective particles. We tested whether DC exposed to antigen from either of these sources could elicit anti-HIV specific immune responses. DESIGN AND METHODS: Apoptotic or necrotic monocytes infected with vaccinia virus vectors encoding HIV antigens, a cell line with integrated HIV-1 and apoptotic CD4 T cells pulsed with non-infectious or infectious HIV-1 virus were used as sources of antigens to assess cross presentation by DC. Furthermore, direct DC presentation of antigen from non-infectious and infectious HIV-1 was examined. RESULTS: We find that dead cells expressing HIV-1 antigens as well as non-infectious HIV-1 particles can be acquired and processed by DC, leading to the activation, differentiation and expansion of viral antigen-specific CD4 and CD8 T cells from seropositive individuals. CONCLUSIONS: These sources of antigens may be critical for the generation and maintenance of anti-HIV-1 immunity by DC.

Antigen Presentation↗
PubMed2002

Enhanced in vitro stimulation of rhesus macaque dendritic cells for activation of SIV-specific T cell responses.

The macaque-simian immunodeficiency virus (SIV) system is one of the best animal models available to study the role of dendritic cells (DCs) in transmission and pathogenesis of HIV, as well as to test DC-based vaccine and therapeutic strategies. To better define and optimize this system, the responsiveness of macaque monocyte-derived DCs to a variety of maturation stimuli was examined. Characteristic immunophenotypic and functional DC maturation induced by standard monocyte conditioned medium (MCM) was compared to the activation induced by a panel of stimuli including soluble CD40L, LPS, Poly I:C, PGE(2)/TNFalpha, and a cocktail mixture of PGE(2)/TNFalpha/IL-1beta/IL-6. Immunophenotypic analysis confirmed that all stimuli induced stable up-regulation of CD25, CD40, CD80, CD83, CD86, HLA-DR, DC-LAMP (CD208), and DEC-205 (CD205). In general, macaque DCs exhibited weaker responses to LPS and Poly I:C than human DCs, and soluble CD40L stimulation induced variable expression of CD25. Interestingly, while the endocytic capacity of CD40L-matured cells was down-modulated comparably to DCs matured with MCM or the cocktail, the T cell stimulatory activity was not enhanced to the same extent. The particularly reproducible and potent T cell stimulatory capacity of cocktail-treated DCs correlated with a more homogenous mature DC phenotype, consistently high levels of IL-12 production, and better viability upon reculture compared to DCs activated by other stimuli. Furthermore, cocktail-matured DCs efficiently captured and presented inactivated SIV to SIV-primed T cells in vitro. Thus, the cocktail represents a particularly potent and useful stimulus for the generation of efficacious immunostimulatory macaque DCs.

Animals↗
PubMed2002

Macrophages relate presynaptic and postsynaptic damage in simian immunodeficiency virus encephalitis.

Neurodegeneration observed in lentiviral-associated encephalitis has been linked to viral-infected and -activated central nervous system macrophages. We hypothesized that lentivirus, macrophages, or both lentivirus and macrophages within distinct microenvironments mediate synaptic damage. Using the simian immunodeficiency virus (SIV)-infected macaque model, we assessed the relationship between virus, macrophages, and neurological damage in multiple brain regions using laser confocal microscopy. In SIV-infected macaques with SIV encephalitis (SIVE), brain tissue concentrations of SIV RNA were 5 orders of magnitude greater than that observed in nonencephalitic animals. In SIVE, staining for postsynaptic protein microtubule-associated protein-2 was significantly decreased in the caudate, hippocampus, and frontal cortical gray matter compared to nonencephalitic controls, whereas staining for presynaptic protein synaptophysin was decreased in SIV-infected macaques with and without encephalitis. These data suggest that presynaptic damage occurs independent of pathological changes associated with SIVE, whereas postsynaptic damage is more tightly linked to regional presence of both activated and infected macrophages.

Animals↗
PubMed2002

Envelope glycoprotein incorporation, not shedding of surface envelope glycoprotein (gp120/SU), Is the primary determinant of SU content of purified human immunodeficiency virus type 1 and simian immunodeficiency virus.

Human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) particles typically contain small amounts of the surface envelope protein (SU), and this is widely believed to be due to shedding of SU from mature virions. We purified proteins from HIV-1 and SIV isolates using procedures which allow quantitative measurements of viral protein content and determination of the ratios of gag- and env-encoded proteins in virions. All of the HIV-1 and most of the SIV isolates examined contained low levels of envelope proteins, with Gag:Env ratios of approximately 60:1. Based on an estimate of 1,200 to 2,500 Gag molecules per virion, this corresponds to an average of between 21 and 42 SU molecules, or between 7 and 14 trimers, per particle. In contrast, some SIV isolates contained levels of SU at least 10-fold greater than SU from HIV-1 isolates. Quantification of relative amounts of SU and transmembrane envelope protein (TM) provides a means to assess the impact of SU shedding on virion SU content, since such shedding would be expected to result in a molar excess of TM over SU on virions that had shed SU. With one exception, viruses with sufficient SU and TM to allow quantification were found to have approximately equivalent molar amounts of SU and TM. The quantity of SU associated with virions and the SU:TM ratios were not significantly changed during multiple freeze-thaw cycles or purification through sucrose gradients. Exposure of purified HIV-1 and SIV to temperatures of 55 degrees C or greater for 1 h resulted in loss of most of the SU from the virus but retention of TM. Incubation of purified virus with soluble CD4 at 37 degrees C resulted in no appreciable loss of SU from either SIV or HIV-1. These results indicate that the association of SU and TM on the purified virions studied is quite stable. These findings suggest that incorporation of SU-TM complexes into the viral membrane may be the primary factor determining the quantity of SU associated with SIV and HIV-1 virions, rather than shedding of SU from mature virions.

Animals↗
PubMed2002

Effects of cytotoxic T lymphocytes (CTL) directed against a single simian immunodeficiency virus (SIV) Gag CTL epitope on the course of SIVmac239 infection.

Vaccine-induced cytotoxic T lymphocytes (CTL) have been implicated in the control of virus replication in simian immunodeficiency virus (SIV)-challenged and simian-human immunodeficiency virus-challenged macaques. Therefore, we wanted to test the impact that vaccine-induced CTL responses against an immunodominant Gag epitope might have in the absence of other immune responses. By themselves, these strong CTL responses failed to control SIVmac239 replication.

Animals↗