Interleukin-10 blocks atherosclerotic events in vitro and in vivo.

Atherosclerosis can be viewed in part as an inflammatory disease process and may therefore be susceptible to manipulation of the immune state. Interleukin 10 (IL-10) is an inhibitory cytokine produced by activated lymphocytes and monocytes. These studies present evidence that IL-10 can inhibit minimally oxidized LDL (MM-LDL)-induced monocyte-endothelium interaction as well as inhibit atherosclerotic lesion formation in mice fed an atherosclerotic diet. Pretreatment of human aortic endothelial cells (HAECs) for 18, but not 4, hours with recombinant IL-10 caused a significant decrease in MM-LDL-induced monocyte binding. IL-10 was found to be maximally effective at 10 ng/mL. Transfection of HAECs with adenovirus expressing viral bcrf-1 IL-10 (Ad-vIL-10) in a sense but not antisense orientation completely inhibited the ability of MM-LDL to induce monocyte binding. Similar results were obtained with IL-10 or Ad-vIL-10 in HAECs stimulated with oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC). We have previously shown increases in cAMP associated with MM-LDL activation of endothelial cells. The MM-LDL-induced increase in cAMP levels was not inhibited by preincubation with IL-10. In vivo studies demonstrated that mice with a murine IL-10 transgene under the control of the human IL-2 promoter have decreased lesions versus controls on an atherogenic diet (5433+/-4008 mm(2) versus 13 574+/-4212 mm(2); P<0.05), whereas IL-10 null mice have increased lesions (33 250+/-9117 mm(2); P<0.0001) compared with either controls or IL-10 transgenic mice. These studies suggest an important role for IL-10 in the atherosclerotic disease process.

T-cell production of an inducible interleukin-10 transgene provides limited protection from autoimmune diabetes.

In a number of animal models of spontaneous autoimmune diabetes, pathogenesis has been highly correlated with autoreactive T-cell production of the type 1 cytokine interferon-gamma (IFN-gamma), while protection from disease was associated with type 2 cytokines such as interleukin (IL)-4. Curiously, in some models, diabetes is associated with unexpected cytokine patterns; for example, diabetes can develop in NOD mice lacking a functional IFN-gamma gene. In another situation, acceleration of diabetes occurs in transgenic mice with constitutive beta-cell expression of the type 2 cytokine IL-10. IL-10 has generally been associated with immunosuppression, including the modulation of class II expression on antigen-presenting cells and the generation of regulatory CD4 T-cells. Because it is possible that unregulated expression of any cytokine might lead to unphysiological effects in vivo, we tested the notion that an inducible T-cell-specific IL-10 transgene might yet mediate a more physiological protection from autoimmune diabetes. Our results show that indeed, regulated T-cell production of IL-10 does not accelerate diabetes and instead can provide significant protection from disease. These results help rectify the apparent discrepancies between the effect of IL-10 on various models of autoimmune diabetes.

Altered immune responses in interleukin 10 transgenic mice.

Interleukin (IL)-10 is a pleiotropic cytokine which inhibits a broad array of immune parameters including T helper cell type 1 (Th1) cytokine production, antigen presentation, and antigen-specific T cell proliferation. To understand the consequences of altered expression of IL-10 in immune models of autoimmune disease, the response to infectious agents, and the response to tumors, we developed transgenic mice expressing IL-10 under the control of the IL-2 promoter. Upon in vitro stimulation, spleen cells from unimmunized transgenic mice secrete higher levels of IL-10 and lower amounts of IFN-gamma than do controls, although no gross abnormalities were detected in lymphocyte populations or serum Ig levels. Transfer of normally pathogenic CD4(+) CD45RBhigh splenic T cells from IL-10 transgenic mice did not cause colitis in recipient severe combined immunodeficiency mice. Furthermore, co-transfer of these transgenic cells with CD4(+) CD45RBhigh T cells from control mice prevented disease. Transgenic mice retained their resistance to Leishmania major infection, indicating that their cell-mediated immune responses were not globally suppressed. Lastly, in comparison to controls, IL-10 transgenic mice were unable to limit the growth of immunogenic tumors. Administration of blocking IL-10 mAbs restored in vivo antitumor responses in the transgenic mice. These results demonstrate that a single alteration in the T cell cytokine profile can lead to dramatic changes in immune responses in a manner that is stimulus dependent. These mice will be useful in defining differences in inflammatory conditions and cellular immunity mediated by IL-10.

Nonclassical behavior of the mouse CD1 class I-like molecule.

The mouse CD1 (mCD1) molecule is a class I-like molecule that is encoded outside of the MHC. We show here that mCD1 shares several properties with Ag-presenting class I molecules, including a requirement for beta2-microglobulin for stable cell-surface expression in T lymphocyte transfectants and thymocytes. mCD1 is also capable of binding to mouse CD8alphabeta heterodimers participating in the activation of CD8+ T cells in a manner similar to classical class I molecules. However, mCD1 surface expression is not decreased at high temperatures in cells that lack the transporter associated with Ag processing (TAP), including both RMA-S and Drosophila melanogaster cells. The data indicate that mCD1 does not require TAP to be expressed in a stable fashion at the cell surface. We speculate that the ability of mCD1 to reach the cell surface in transporter-deficient cells may reflect its ability to present a distinct set of ligands. The properties of mCD1 described here can account, in part, for the selection of the diverse populations of T cells that are known to be mCD1 reactive.

TAP-independent selection of CD8+ intestinal intraepithelial lymphocytes.

Intestinal intraepithelial lymphocytes (IEL) are mostly CD8 single positive T cells. IEL with a TCR-alpha(beta) that are CD8 single positive are absent from beta(2)-microglobulin (beta(2)m)-deficient mice, consistent with the idea that these IEL, like other TCR-alpha(beta)+, CD8+ T cells, require class I molecules for positive selection. In contrast, here we show that substantial numbers of TCR-alpha(beta)+, CD8 single positive IEL are present in mice deficient for the transporter associated with Ag processing 1 (TAP 1) gene, although T cells with this phenotype are absent from thymus, spleen, and lymph nodes of these same mice. The majority of TCR-alpha(beta)+, CD8 single positive IEL in TAP-deficient mice expresses CD8 molecules composed of alpha(alpha) homodimers and they express a diverse set of V(beta) gene segments. In addition, the number of TCR-alpha(beta)+, CD4/CD8 double positive IEL is decreased in beta(2)m-deficient mice but not in TAP-deficient mice. The dependence of the two TCR-alpha(beta)+ IEL populations that express CD8alpha(alpha) homodimers on beta(2)m as opposed to TAP molecules is striking. It suggests that TAP-independent but beta(2)m-requiring nonclassical class I molecules expressed by cells in the intestine, such as the thymus leukemia Ag and CD1, could play a pivotal role in the development and/or the accumulation of major subpopulations of TCR-alpha(beta)+ IEL.

Evolution of alphaviruses in the eastern equine encephalomyelitis complex.

Evolution of viruses in the eastern equine encephalomyelitis (EEE) complex was studied by analyzing RNA sequences and oligonucleotide fingerprints from isolates representing the North and South American antigenic varieties. By using homologous sequences of Venezuelan equine encephalomyelitis virus as an outgroup, phylogenetic trees revealed three main EEE virus monophyletic groups. A North American variety group included all isolates from North America and the Caribbean. One South American variety group included isolates from the Amazon basin in Brazil and Peru, while the other included strains from Argentina, Guyana, Ecuador, Panama, Trinidad, and Venezuela. No evidence of heterologous recombination was obtained when three separate regions of the EEE virus genome were analyzed independently. Estimates of the overall rate of EEE virus evolution (nucleotide substitution) were 1.6 x 10(-4) substitution per nucleotide per year for the North American group and 4.3 x 10(-4) for the Argentina-Panama South American group. Evolutionary rate estimates for the North American group increased over 10-fold (from about 2 x 10(-5) to 4 x 10(-4)) concurrent with divergence of two monophyletic groups during the early 1970s. The North and South American antigenic varieties diverged roughly 1,000 years ago, while the two main South American groups diverged about 450 years ago. Analysis of multiple strains isolated from an upstate New York transmission focus during the same years suggested that, in certain locations, EEE virus may be relatively isolated for short time periods.

A comparison of the nucleotide sequences of eastern and western equine encephalomyelitis viruses with those of other alphaviruses and related RNA viruses.

The complete nucleotide sequence of a 1982 Florida strain of eastern equine encephalomyelitis (EEE) virus, and partial sequence of the nonstructural protein genes of western equine encephalomyelitis (WEE) virus, were determined. The EEE virus genome was 11,678 nucleotides in length, excluding the cap nucleotide and poly(A) tail, and the nucleotide composition was 28% A, 24% G, 25% C, and 23% U. The organization of both EEE and WEE virus genomes was like that of other alphaviruses and included a termination codon between the nsP3 and nsP4 genes. Codon usage for 10 of 20 amino acids was nonrandom in the EEE genome, and dinucleotide CpG-containing codons were underutilized in both genomes. The slight CpG deficiency was similar to that seen in other alphaviruses and plant viruses in the alphavirus-like group, but less than that of poliovirus and yellow fever virus. This slight deficiency may reflect adaptation for replication in both CpG-deficient vertebrates, as well as insects which do not have CpG-deficient genomes. Phylogenetic analyses using nonstructural protein amino acid sequences indicated that alphaviruses evolved from a common ancestor which existed a few thousand years ago. An intercontinental introduction of an ancestral virus from the Old to New World, or vice versa, probably resulted in two main extant groups: one includes New World (EEE and Venezuelan equine encephalitis) viruses, while the other includes Old World (Sindbis, Middelburg, O'nyong-nyong, Ross River, and Semliki Forest) viruses. The position of WEE virus in the phylogenetic trees indicated that, in addition to its capsid gene (C. S. Hahn et al. (1988) Proc. Natl. Acad. Sci. USA 85, 5997-6001), WEE virus acquired its nonstructural genes from an EEE-like ancestor during recombination.

Genetic characterization of an antigenic subtype of eastern equine encephalomyelitis virus.

A 1983 human Mississippi isolate of eastern equine encephalomyelitis virus (EEEV), recently identified as an antigenic subtype of the North American variety, was genetically characterized using oligonucleotide fingerprinting and sequencing of viral RNA. This strain was found to be very closely related to other North American EEEV isolates from the same time period. Phylogenetic analysis suggested that this subtype belongs to a single EEEV lineage in North America. Two amino acid substitutions in the E2 envelope glycoprotein, not seen in either other isolates sequenced, probably contributed to the antigenic difference with respect to other EEEV strains. These substitutions include threonine for lysine at position 71, resulting in the addition of a potential N-linked glycosylation site, and lysine for glutamic acid at position 147.