Systemic infection and limited replication of SHIV vaccine virus in brains of macaques inoculated intracerebrally with infectious viral DNA

Resources, mortality, and disease ecology: Importance of positive feedbacks between host growth rate and pathogen dynamics

Resource theory and metabolic scaling theory suggest that the dynamics of a pathogen within a host should strongly depend upon the rate of host cell metabolism. Once an infection occurs, key ecological interactions occur on or within the host organism that determine whether the pathogen dies out, persists as a chronic infection, or grows to densities that lead to host death. We hypothesize that, in general, conditions favoring rapid host growth rates should amplify the replication and proliferation of both fungal and viral pathogens. If a host population experiences an increase in mortality, to persist it must have a higher growth rate, per host, often reflecting greater resource availability per capita. We hypothesize that this could indirectly foster the pathogen, which also benefits from increased within-host resource turnover. We first bring together in a short review a number of key prior studies which illustrate resource effects on viral and fungal pathogen dynamics. We then report new results from a semi-continuous cell culture experiment with SHIV, demonstrating that higher mortality rates indeed can promote viral proliferation. We develop a simple model that illustrates dynamical consequences of these resource effects, including interesting effects such as alternative stable states and oscillatory dynamics. Our paper contributes to a growing body of literature at the interface of ecology and infectious disease epidemiology, emphasizing that host abundances alone do not drive community dynamics: the physiological state and resource content of infected hosts also strongly influence host-pathogen interactions.

Characterization of T-cell responses in macaques immunized with a single dose of HIV DNA vaccine

The optimization of immune responses (IR) induced by HIV DNA vaccines in humans is one of the great challenges in the development of an effective vaccine against AIDS. Ideally, this vaccine should be delivered in a single dose to immunize humans. We recently demonstrated that the immunization of mice with a single dose of a DNA vaccine derived from pathogenic SHIV(KU2) (Delta4SHIV(KU2)) induced long-lasting, potent, and polyfunctional HIV-specific CD8(+) T-cell responses (G. Arrode, R. Hegde, A. Mani, Y. Jin, Y. Chebloune, and O. Narayan, J. Immunol. 178:2318-2327, 2007). In the present work, we expanded the characterization of the IR induced by this DNA immunization protocol to rhesus macaques. Animals immunized with a single high dose of Delta4SHIV(KU2) DNA vaccine were monitored longitudinally for vaccine-induced IR using multiparametric flow cytometry-based assays. Interestingly, all five immunized macaques developed broad and polyfunctional HIV-specific T-cell IR that persisted for months, with an unusual reemergence in the blood following an initial decline but in the absence of antibody responses. The majority of vaccine-specific CD4(+) and CD8(+) T cells lacked gamma interferon production but showed high antigen-specific proliferation capacities. Proliferative CD8(+) T cells expressed the lytic molecule granzyme B. No integrated viral vector could be detected in mononuclear cells from immunized animals, and this high dose of DNA did not induce any detectable autoimmune responses against DNA. Taken together, our comprehensive analysis demonstrated for the first time the capacity of a single high dose of HIV DNA vaccine alone to induce long-lasting and polyfunctional T-cell responses in the nonhuman primate model, bringing new insights for the design of future HIV vaccines.

Cocaine-mediated enhancement of virus replication in macrophages: implications for human immunodeficiency virus-associated dementia

Injection drug use has been recognized as a major risk factor for acquired immunodeficiency syndrome (AIDS) from the outset of the epidemic. Cocaine, one of the most widely abused drugs in the United States, can both impair the functions of macrophages and CD4(+) lymphocytes and also activate human immunodeficiency virus (HIV)-1 expression in these cells. Because the brain is the target organ for both cocaine and HIV, the objective of the present study was to explore the effects of cocaine on virus replication in macrophages, the target cells for the virus in the central nervous system (CNS). Cocaine markedly enhanced virus production in simian human immunodeficiency virus (SHIV)-infected monocyte-derived macrophages (MDMs) and in U1 cells, a chronically infected promonocytic cell line as monitored by enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry. Cocaine treatment also resulted in the activation of nuclear factor (NF)-kappa B and transcriptional activation of the HIV-LTR (long terminal repeat) gag-GFP (green fluorescent protein). Analyses of chemokines in cocaine-treated macrophages by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and Luminex assays suggested increased expression of interleukin (IL)-10, a cytokine that is known to promote HIV replication in MDMs. In addition to enhancing IL-10 expression, cocaine also caused an up-regulation of the macrophage activation marker, human leukocyte antigen (HLA)-DR, in MDMs. The synergistic effect of cocaine on virus replication and its enhancement of host activation markers suggest that cocaine functions at multiple pathways to accelerate HIV-associated dementia (HAD).

Protection of macaques against AIDS with a live attenuated SHIV vaccine is of finite duration

Using background data that live vaccines against several viral pathogens are effective in inducing life-long protection against disease, we undertook studies in macaques to determine the duration of protection that two live SHIV vaccines could induce against AIDS. Earlier studies had established that macaques immunized once with a live vaccine and challenged 6 months later were protected, and that other macaques given two sequential inoculations of live vaccines were protected for at least 1 year. Protection was associated with persistence of the vaccine viruses. In this study, we sought to determine whether the duration of protection in macaques given a single inoculation of replication competent live vaccines would extend beyond 3 years. Two groups of four rhesus macaques were inoculated with two live SHIV vaccines, respectively. The viruses replicated transiently in all animals but at the 3-year time point, PCR analysis of PBMC did not detect DNA of either virus in any of the animals, and all were negative for CMI responses in the blood. All 8 animals succumbed to disease when challenged with pathogenic viruses.

Quantitative multiplex assay for simultaneous detection of the Indiana serotype of vesicular stomatitis virus and HIV gag

Assessment of in vivo viral replication of live attenuated recombinant vesicular stomatitis virus (rVSV) vaccine vector candidates encoding HIV gag requires comprehensive preclinical safety studies, and development of sensitive assays to monitor the outcome of vaccination of animals is important. In this study, two 2-step quantitative real-time RT-PCR assays were developed; a singleplex assay to detect VSV genomic RNA from ferrets inoculated intra-cranially (IC) or intra-nasally (IN) with either a wild-type (wt) virus or an attenuated rVSV vector engineered to express HIV gag protein, and a duplex assay to simultaneously detect VSV-N and HIV-gag mRNAs from cynomolgus macaques inoculated intra-thalamically (IT) with the same viruses. Using synthetic oligonucleotides as standards, the lower limit of detection of VSV-N and HIV-gag was 50 copies. Results showed high levels of wt VSV(IN) genomic RNA and mRNA in ferret and macaque tissues, respectively, and significantly lower levels of VSV genomic RNA and VSV-N and HIV-gag mRNAs in tissues from animals inoculated with the attenuated rVSV vector. These assays correlated with both the course of infection for these animals, and the infectious viral load measured by a standard plaque assay, and could be used to determine the safety profile of rVSV vaccine vectors.

Immunoprophylaxis against AIDS in macaques with a lentiviral DNA vaccine

We earlier reported that immunization of macaques with a reverse transcriptase-deleted SHIV(KU2) (DeltartSHIV(KU2)) plasmid that contained HIV-1(HXB2) env and SIV gag-nef induced protection against AIDS caused by challenge virus SHIV89.6P with a heterologous env. We further deleted vif and integrase from DeltartSHIV(KU2) and substituted the 3'LTR with SV40 poly A sequences, creating Delta4SHIV(KU2) (M) and a parallel construct containing gag-nef of HIV-1(SF2), Delta4SHIV(KU2) (H). Six macaques received two intramuscular injections of the (M) DNA, and another six received three injections of the (H) DNA. Three of the latter group received two post-challenge boosts with (M) DNA vaccine. Seven virus control macaques were inoculated with SHIV89.6P. All twelve immunized macaques were challenged with SHIV89.6P virus, and CMI responses were measured by ELISPOT assays. Virus control animals all developed progressive infection, whereas vaccinated macaques from both groups controlled virus replication, with plasma viral loads dropping to undetectable levels between weeks 6 and 126 p.i. This DNA vaccine was efficacious even though it encoded Env, Gag, and Nef that were genetically distinct from the proteins in the challenge virus. The DNA vaccine induced broad-based protection without using viral proteins to boost the immunity.

Therapy of "SHIV" infected macaques with liposomes delivering antisense interleukin-4 DNA

BACKGROUND/OBJECTIVES

To explore the effects of antisense (AS) interleukin (IL)-4 on virus replication and CD8+ T-cell responses in lymph nodes and blood of macaques infected with simian human immunodeficiency virus, SHIV(89.6)P.

METHODS

Six macaques were inoculated with simian human immunodeficiency virus (SHIV(89.6)P). Seven days later, four of the animals were given 1 mg AS IL-4 plasmid complexed with Megafectin liposome, intravenously, and two of these received a second injection of the same material on day 9. All six macaques were killed at 2 weeks post infection (pi) and monitored for viral RNA and CD8+ T cells in blood and lymph nodes by real-time reverse transcriptase-polymerase chain reaction, flow cytometry and immunohistochemistry.

RESULTS

In contrast to the lymph nodes from virus control animals, the lymph nodes of AS IL-4-treated animals had a significant reduction in viral loads and reduced depletion of cells from the nodes. There was an increase in CD8+ T cells in the nodes, and many of the cells expressed granzyme B, suggesting functional activation. This trend of virus reduction and increased CD8+ T cell numbers was also reflected in blood.

CONCLUSIONS

The therapeutic effect of the AS IL-4 suggests indirectly that the acute immunosuppressive disease caused by SHIVs is mediated, in part, by IL-4 that causes enhanced virus replication by suppressing anti-viral CD8+ T-cell responses, and that this effect was reduced by treatment of the animals with AS IL-4.

The role of monocytes and perivascular macrophages in HIV and SIV neuropathogenesis: information from non-human primate models

Perivascular macrophages are located in the perivascular space of cerebral microvessels and thus uniquely situated at the intersection between the brain parenchyma and blood. Connections between the nervous and immune systems are mediated in part through these cells that are ideally located to sense perturbations in the periphery and turnover by cells entering the central nervous system (CNS) from the circulation. It has become clear that unique subsets of brain macrophages exist in normal and SIV- or HIV-infected brains, and perivascular macrophages and similar cells in the meninges and choroid plexus play a central role in lentiviral neuropathogenesis. Common to all these cell populations is their likely replacement within the CNS by monocytes. Studies of SIV-infected non-human primates and HIV-infected humans underscore the importance of virus-infected and activated monocytes, which traffic to the CNS from blood to become perivascular macrophages, potentially drive the blood-brain barrier damage and cause neuronal injury. This review summarizes what we know about SIV- and HIV-induced neuropathogenesis focusing on brain perivascular macrophages and their precursors in blood that may mediate HIV CNS infection and injury.

Active simian immunodeficiency virus (strain smmPGm) infection in macaque central nervous system correlates with neurologic disease

Simian immunodeficiency virus strain smmPGm can induce neuropathology in macaques and is a model for the development of human HIV-related brain injury. For quantitative studies of proviral presence and expression in the central nervous system (CNS), we inoculated 8 macaques intravenously with the virus. Three animals were necropsied 2 to 4 weeks after development of infection, and we obtained lymphoid tissue biopsies from 5 animals before 5 weeks after infection. Peak plasma viral loads averaged 10 viral RNA Eq/mL at week 2, whereas cerebrospinal fluid viral loads peaked at 10 viral RNA Eq/mL. The proviral DNA loads and viral gag mRNA expression in tissues were quantified by real-time polymerase chain reaction. Two animals developed neurologic disease characterized by meningoencephalitis and meningitis. Proviral DNA levels in CNS tissues of these animals at necropsy revealed 10 and 10 copies/microg of DNA, respectively, whereas viral RNA expression in the CNS reached 100 to 1000 times higher levels than those seen in early necropsies. In sharp contrast, in 2 animals necropsied at later times without CNS disease, virus mRNA expression was not detected in any CNS tissue. Our results are consistent with the hypothesis that active virus expression in the CNS is strongly correlated with neurologic disease and that the event occurs at variable periods after infection.

A noninfectious simian/human immunodeficiency virus DNA vaccine that protects macaques against AIDS

Simian/human immunodeficiency virus SHIV(KU2) replicates with extremely high titers in macaques. In order to determine whether the DNA of the viral genome could be used as a vaccine if the DNA were rendered noninfectious, we deleted the reverse transcriptase gene from SHIVKU2 and inserted this DNA (DeltartSHIVKU2) into a plasmid that was then used to test gene expression and immunogenicity. Transfection of Jurkat and human embryonic kidney epithelial (HEK 293) cells with the DNA resulted in production of all of the major viral proteins and their precursors and transient export of a large quantity of the Gag p27 into the supernatant fluid. As expected, no infectious virus was produced in these cultures. Four macaques were injected intradermally with 2 mg of the DNA at 0, 8, and 18 weeks. The animals developed neutralizing antibodies and low enzyme-linked immunospot assay (E-SPOT) titers against SHIVKU2. These four animals and two unvaccinated control animals were then challenged with heterologous SHIV89.6P administered into their rectums. The two control animals developed viral RNA titers exceeding 10(6) copies/ml of plasma, and these titers were accompanied by the loss of CD4+ T cells by 2 weeks after challenge. The two control animals died at weeks 8 and 16, respectively. All four of the immunized animals became infected with the challenge virus but developed lower titers of viral RNA in plasma than the control animals, and the titers decreased over time in three of the four macaques. The fourth animal remained viremic and died at week 47. Whereas the control animals failed to develop E-SPOT responses, all four of the immunized animals developed anamnestic E-SPOT responses after challenge. The animal that died developed the highest E-SPOT response and was the only one that produced neutralizing antibodies against the challenge virus. These results established that noninfectious DNA of pathogenic SHIV could be used as a vaccine to prevent AIDS, even though the immunological assays used did not predict the manner in which the challenge virus would replicate in the vaccinated animals.

Simian human immunodeficiency virus-associated pneumonia correlates with increased expression of MCP-1, CXCL10, and viral RNA in the lungs of rhesus macaques

Pulmonary disorders are the most frequent cause of death in HIV-1-infected individuals with AIDS and remain important even in the current era of potent antiretroviral therapy. Macaques infected with Simian/Human Immunodeficiency Virus (SHIV) develop pulmonary disease and concurrent opportunistic infections similar to those observed in HIV-infected individuals, thereby providing an excellent working model to elucidate the pathogenesis of the human lung disease. Since chemokines play a crucial role in the recruitment of inflammatory cells to tissues, we investigated the relationship between respiratory disease and the levels of chemokines, monocyte chemotactic protein-1 (MCP-1) and CXCL10, in the lungs of SHIV-infected rhesus macaques. We found that lung pathology in infected macaques was closely associated with overexpression of MCP-1 and CXCL10. In addition, these chemokines could, in part, be responsible for the recruitment of inflammatory cells infiltrating into the diseased lungs as demonstrated by chemotactic assays. Lung pathology and increased levels of MCP-1 and CXCL10 correlated with high viral loads in the lung parenchyma. Using confocal microscopy, we identified SHIV-infected macrophages as the major producers of MCP-1 and CXCL10 in the diseased lungs. These data suggest that chemokine overexpression plays an important role in the pathogenesis of SHIV-associated pulmonary disease in macaques.

Quantification of tetracycline resistance genes in feedlot lagoons by real-time PCR

A new real-time PCR method is presented that detects and quantifies three tetracycline resistance (Tcr) genes [tet(O), tet(W), and tet(Q)] in mixed microbial communities resident in feedlot lagoon wastewater. Tcr gene real-time TaqMan primer-probe sets were developed and optimized to quantify the Tcr genes present in seven different cattle feedlot lagoons, to validate the method, and to assess whether resistance gene concentrations correlate with free-tetracycline levels in lagoon waters. The method proved to be sensitive across a wide range of gene concentrations and provided consistent and reproducible results from complex lagoon water samples. The log10 of the sum of the three resistance gene concentrations was correlated with free-tetracycline levels (r2 = 0.50, P < 0.001; n = 18), with the geometric means of individual resistance concentrations ranging from 4- to 8.3-fold greater in lagoon samples with above-median tetracycline levels (>1.95 microg/liter by enzyme-linked immunosorbent assay techniques) than in below-median lagoon samples. Of the three Tcr genes tested, tet(W) and tet(Q) were more commonly found in lagoon water samples. Successful development of this real-time PCR assay will permit other studies quantifying Tcr gene numbers in environmental and other samples.

Inhibition of pathogenic SHIV replication in macaques treated with antisense DNA of interleukin-4

Interleukin-4 is implicated in the pathogenesis of HIV-induced AIDS and causes enhancement of replication of virus strains that use the CXCR4 (X4) coreceptor. In this study, we explored the effects of interleukin-4 (IL-4) antisense (AS) DNA on replication of X4, simian human immunodeficiency viruses, SHIV(KU-2) and SHIV89.6P. AS IL-4 oligomer caused inhibition of virus replication in cultures of CD4+ T cells and macrophages derived from macaques. Plasmid expressing AS IL-4 DNA was also effective in abrogating virus replication in macrophage cultures. Relevance of these cell culture studies was confirmed in vivo by treating SHIV89.6P-infected macaques with AS IL-4 DNA. Six macaques were inoculated with the virus, and 4 were treated with AS IL-4 DNA. This resulted in a significant decrease in viral RNA concentrations in the liver, lungs, and spleen tissues that are all sites of virus replication in macrophages. This is the first demonstration of effective inhibition of an HIV-like virus in tissues by AS DNA of a cytokine. In the present era of increasing resistance of HIV to antiviral compounds, exploration of adjunct therapies directed at host responses in combination with antiretroviral drugs may be of value for the treatment of AIDS.

HIV in central nervous system and behavioral development: an HIV-2287 macaque model of AIDS

OBJECTIVE

To determine which route of inoculation produced consistent and frequent HIV infection in the central nervous system (CNS) and alterations in cognitive and motor development in infant macaques.

METHODS

Infant macaques (Macaca nemestrina) were inoculated with the highly pathogenic strain HIV-2287 intravenously (n = 3) or intrathecally (n = 3). Uninfected infants were evaluated as controls. Disease progression was evaluated by virological assessment of blood and cerebral spinal fluid (CSF), CD4 T cell count in blood, and quinolinic acid levels in CSF (a surrogate marker of neuronal cell damage). The effect of HIV infection on cognitive and motor development in infants was monitored during the 6-month study.

RESULTS

Either route of HIV-2287 inoculation produced detectable viral RNA in CSF and productive infection in blood. Detection of virus in CSF paralleled a rise in quinolinic acid levels. All HIV-infected infants experienced a severe and rapid decline in CD4 T cell counts by 10 weeks after viral infection. HIV-infected infants, particularly those infected by the intravenous route, exhibited delays in reaching cognitive and motor milestones, which paralleled neuropathological changes.

CONCLUSIONS

The HIV-2287 infant model produced a high incidence of viral infection in the CNS regardless of the route of inoculation. Significant alteration in neurobehavioral development was observed in HIV-infected infants, and this measure was significantly impaired particularly in infants infected by the intravenous route. These data, coupled with the ability to detect viral RNA and changes in quinolinic acid levels in CSF, may allow quantitative evaluation of drug and immune candidates for treating neurological effects of AIDS.