Comparison of cytotoxic properties of neonatal and adult neutrophils and monocytes and enhancement by cytokines

We studied cytotoxic capabilities of newborn polymorphonuclear leukocytes (PMNs) and monocytes and their enhancement by cytokines and antibodies. Umbilical cord PMNs were assessed for their ability to kill various target cells spontaneously, after activation with phorbol myristate acetate, in the presence of antiserum (antibody-dependent cellular cytotoxicity), and in the presence of dually specific antibody (heteroantibody-mediated cytotoxicity). Target cells included the K562 cell line (natural killer cell target), chicken erythrocytes (CRBCs), and herpes simplex virus-infected CEM cell lines. Newborn PMNs were equivalent to adult PMNs in their cytotoxic capacity in several cytotoxicity assays. Neither adult nor newborn PMNs lyse tumor cell targets (i.e., K562 cells) spontaneously, but both lyse K562 cells following activation with phorbol myristate acetate. Both adult and newborn PMNs lyse CRBCs and herpes simplex virus-infected CEM cells in antibody-dependent cellular cytotoxicity assays, and this lysis could be enhanced by the cytokines granulocyte-macrophage colony-stimulating factor and gamma interferon. PMN heteroantibody-mediated cytotoxicity, resulting from the use of an antibody with dual specificity to CRBCs and immunoglobulin G FcRII, was greater in newborn PMNs than in adult PMNs; however, monocyte heteroantibody-mediated cytotoxicity, resulting from the use of an antibody to CRBCs and monocyte immunoglobulin G FcRI, was lower in newborn monocytes than in adult monocytes. The percentage, but not the density, of PMNs expressing FcRII was significantly reduced in newborn PMNs compared with that in adult PMNs, while the percentages and densities of FcRI expression were equivalent in newborn and adult monocytes. We conclude that the cytotoxic capability in term newborn PMNs is equivalent to that in adult PMNs, that the activity of newborn PMNs can be enhanced by antibody and/or cytokines, and that PMNs can contribute to the newborn's ability to kill virus-infected cells.

Lipopolysaccharide and cytokine augmentation of human monocyte IgA receptor expression and function

Receptors for IgA (Fc alpha R) are found on phagocytic cells in the peripheral blood and tissues associated with mucosal areas where IgA Abs constitute a major line of defense. Because Fc alpha R are capable of triggering protective functions of monocytes and neutrophils, such as phagocytosis and the oxidative burst, they may be important in amplifying the antimicrobial effects of IgA. Various cytokines play a role in regulating function and FcR expression of monocytes, macrophages, and neutrophils. The present studies examine the modulation of monocyte Fc alpha R by LPS and cytokines. LPS strongly up-regulated monocyte Fc alpha R expression. TNF and IL-1, produced in response to LPS, promoted Fc alpha R increase, as did GM-CSF; whereas IFN-gamma down-regulated Fc alpha R. Increased receptor expression was accompanied by augmented IgA-mediated phagocytosis. An increase in Fc alpha R-specific mRNA was detected in monocytes treated with TNF, IL-1, GM-CSF, and LPS; whereas message was reduced in cells treated with IFN-gamma. Monocyte-derived macrophages and cells of the Monomac 6 monocyte-like line expressed greater numbers of Fc alpha R than monocytes but were less responsive to LPS and TNF. Cell lines THP-1 and U937, which expressed similar or lower levels of Fc alpha R than monocytes, displayed an increase in Fc alpha R in response to LPS and, to various degrees, to TNF, IL-1, and GM-CSF. These results indicate that Fc alpha R on monocytes are modulated by endotoxin and an array of cytokines distinct from those that regulate expression of FcR for IgG.

Lipopolysaccharide and cytokine augmentation of human monocyte IgA receptor expression and function

Receptors for IgA (Fc alpha R) are found on phagocytic cells in the peripheral blood and tissues associated with mucosal areas where IgA Abs constitute a major line of defense. Because Fc alpha R are capable of triggering protective functions of monocytes and neutrophils, such as phagocytosis and the oxidative burst, they may be important in amplifying the antimicrobial effects of IgA. Various cytokines play a role in regulating function and FcR expression of monocytes, macrophages, and neutrophils. The present studies examine the modulation of monocyte Fc alpha R by LPS and cytokines. LPS strongly up-regulated monocyte Fc alpha R expression. TNF and IL-1, produced in response to LPS, promoted Fc alpha R increase, as did GM-CSF; whereas IFN-gamma down-regulated Fc alpha R. Increased receptor expression was accompanied by augmented IgA-mediated phagocytosis. An increase in Fc alpha R-specific mRNA was detected in monocytes treated with TNF, IL-1, GM-CSF, and LPS; whereas message was reduced in cells treated with IFN-gamma. Monocyte-derived macrophages and cells of the Monomac 6 monocyte-like line expressed greater numbers of Fc alpha R than monocytes but were less responsive to LPS and TNF. Cell lines THP-1 and U937, which expressed similar or lower levels of Fc alpha R than monocytes, displayed an increase in Fc alpha R in response to LPS and, to various degrees, to TNF, IL-1, and GM-CSF. These results indicate that Fc alpha R on monocytes are modulated by endotoxin and an array of cytokines distinct from those that regulate expression of FcR for IgG.

Structure and genetics of the partially duplicated gene RP located immediately upstream of the complement C4A and the C4B genes in the HLA class III region. Molecular cloning, exon-intron structure, composite retroposon, and breakpoint of gene duplication

The correlation of many HLA-associated autoimmune and genetic diseases with the polymorphic complement C4 genes may be attributed to the presence of disease susceptibility genes in the close proximity of C4. We have cloned and characterized a pair of partially duplicated genes, RP1 and RP2, located 611 base pairs upstream of the human C4A and C4B genes, respectively. The putative RP protein, consisting of 364 amino acid residues, is basic and highly hydrophilic. There is a bipartite nuclear localization signal at residues 114-131 and therefore RP may be a nuclear protein. Northern blot analysis suggested that RP is ubiquitously expressed. The 5' region of the RP1 gene is CpG rich, which is a characteristic of housekeeping genes. The RP1 gene contains nine exons. Located in the fourth intron is a cluster of Alu elements, and a newly defined composite retroposon SVA with a SINE, multiple copies of GC-rich VNTRs and an Alu element altogether enclosed by direct terminal repeats. Members of SVA are also present in the complement C2 gene located about 20 kilobases upstream of RP1 in the HLA and in the cytochrome CYP1A1 gene. Determination of the DNA sequences for RP2 from two different HLA haplotypes revealed identical hybrid sequences which resulted from fusion of RP with the tenascin-like Gene X and truncation of the 5' regions of both genes. Cumulative data suggest that the four tandemly arranged genes RP, complement C4, steroid 21-hydroxylase (CYP21), and Gene X altogether form a modular structure, RCCX. The number of RCCX modules varies from one to three or more in the population. Absence of the truncated genes RP2 and Gene XA have been detected in genomes with single RCCX modules. Duplication of the RCCX modules probably occurred before the speciation of great apes and humans as they contain the same breakpoint region of RP and Gene X gene duplication.

Application of shape analysis to mammographic calcifications

The authors have developed a set of shape factors to measure the roughness of contours of calcifications in mammograms and for use in their classification as malignant or benign. The analysis of mammograms is performed in three stages. First, a region growing technique is used to obtain the contours of calcifications. Then, three measures of shape features, including compactness, moments, and Fourier descriptors are computed for each region. Finally, their applicability for classification is studied by using the three shape measures to form feature vectors. Classification of 143 calcifications from 18 biopsy-proven cases as benign or malignant using the three measures with the nearest-neighbor method was 100% accurate.

Sonic hedgehog, a member of a family of putative signaling molecules, is implicated in the regulation of CNS polarity

We have identified three members of a mouse gene family related to the Drosophila segment polarity gene, hedgehog (hh). Like hh, they encode putative secreted proteins and are thus implicated in cell-cell interactions. One of these, Sonic hh (Shh), is expressed in the notochord, the floor plate, and the zone of polarizing activity, signaling centers that are thought to mediate central nervous system (CNS) and limb polarity. Ectopic expression of Shh in the mouse CNS leads to the activation of floor plate-expressed genes. These results suggest that Shh may play a role in the normal inductive interactions that pattern the ventral CNS.

Evaluation of an in vitro method for the estimation of the selenium availability from cow's milk

The present study evaluates the application of an in vitro digestion procedure for estimating the selenium (Se) availability from cow's milk. The results obtained by this in vitro method indicate that only a small portion (< 10%) of milk Se can be estimated as available. The available fraction of whole milk (4.7%) was significantly lower compared to the Se availability of skim milk (7.3%). Investigations on the methodology of the in vitro method indicate that the portion of total potentially available Se, determined as total dialysable Se, increases simultaneously with protein digestibility along with the digestion process. Therefore it is concluded that protein digestibility might largely influence the Se availability from milk.

Plasmid analysis and phage typing in the study of staphylococcal colonization and disease in newborn infants

Plasmid analysis, bacteriophage typing and antibiograms were used to detect the source and rate of Staphylococcus aureus colonization and disease in newborn infants in a nursery. Staphylococcal colonization on the nasal mucosa and umbilicus of 140 neonates took place within 12 hours after birth. The colonization rates reached 100% from the fourth day onward and fell to 66.7%, 25.5% and 17.5% by the age of 1 month, 6 months and 1 year, respectively. The incidence of nursery-acquired infection caused by S. aureus was at least 16.4%. All infections were confined to the skin or mucosa and were not serious. It is believed that the S. aureus which colonized and infected the newborn infants mainly originated from the nares and the hands of nurses, because only S. aureus strains from nurses and infected infants had the same phage patterns (52/52A/47/53/75/77/81) and carried 2 plasmids of the same size (1.4 and 1.7 Md), whereas S. aureus isolated from other sources did not have the same phage patterns or plasmid profiles. In view of the results of this study, it is considered that the importance of careful washing of the hands of personnel before and after handling infants should be emphasized.

Conserved T-cell receptor repertoire in simian immunodeficiency virus-infected rhesus monkeys

Studies to assess the possibility that the HIV may encode a superantigen that plays a role in the depletion of functional CD4+ lymphocytes in the infected individual have yielded discrepant results. The problem in performing conclusive examinations of this issue may be attributed, at least in part, to the difficulty of prospectively studying individuals from before their infection until the time of profound CD4+ lymphocyte loss. To determine whether the AIDS virus deletes particular subpopulations of V beta-expressing lymphocytes, we have employed an animal model of AIDS, the simian immunodeficiency virus (SIV)-infected macaque monkey. Rhesus monkeys were experimentally infected with SIVmac and studied prospectively. A PCR-based quantitative method for assessing TCR repertoire was employed to analyze the expression of 24 V beta and 30 V alpha gene families in the monkeys. Although circulating PBL were increased in number by 3 wk after SIVmac infection, the expanded lymphocyte populations exhibited no significant perturbation in their TCR V beta repertoires. PBL obtained from monkeys before and 0.5 to 3 years after infection displayed no significant change in V beta and V alpha gene family expression. Finally, no deletion of V beta-expressing cell subpopulations could be demonstrated in purified CD4+ lymphocytes from infected monkeys. This was true even for monkeys whose blood contained less than 200 CD4+ lymphocytes/microliters. These results indicate that the TCR repertoire is conserved in SIVmac-infected rhesus monkeys and suggests that mechanisms other than superantigen-induced deletion must be responsible for CD4+ lymphocyte loss in these animals.

Conserved T-cell receptor repertoire in simian immunodeficiency virus-infected rhesus monkeys

Studies to assess the possibility that the HIV may encode a superantigen that plays a role in the depletion of functional CD4+ lymphocytes in the infected individual have yielded discrepant results. The problem in performing conclusive examinations of this issue may be attributed, at least in part, to the difficulty of prospectively studying individuals from before their infection until the time of profound CD4+ lymphocyte loss. To determine whether the AIDS virus deletes particular subpopulations of V beta-expressing lymphocytes, we have employed an animal model of AIDS, the simian immunodeficiency virus (SIV)-infected macaque monkey. Rhesus monkeys were experimentally infected with SIVmac and studied prospectively. A PCR-based quantitative method for assessing TCR repertoire was employed to analyze the expression of 24 V beta and 30 V alpha gene families in the monkeys. Although circulating PBL were increased in number by 3 wk after SIVmac infection, the expanded lymphocyte populations exhibited no significant perturbation in their TCR V beta repertoires. PBL obtained from monkeys before and 0.5 to 3 years after infection displayed no significant change in V beta and V alpha gene family expression. Finally, no deletion of V beta-expressing cell subpopulations could be demonstrated in purified CD4+ lymphocytes from infected monkeys. This was true even for monkeys whose blood contained less than 200 CD4+ lymphocytes/microliters. These results indicate that the TCR repertoire is conserved in SIVmac-infected rhesus monkeys and suggests that mechanisms other than superantigen-induced deletion must be responsible for CD4+ lymphocyte loss in these animals.

[Neuroendocrine markers in lung cancer]

80 cases of resected lung cancer were studied using five different neuroendocrine (NE) markers with the avidin-biotin-peroxidase complex method.

RESULTS

(1) The positive rates of carcinoid and small cell lung cancer (SCLC) expressing NE markers was 100% and 93.8% respectively, and the positive rate of non-SCLC (except carcinoid) was 24.1% (2) If NE granules were found by electron microscope, NE markers all gave positive reaction. (3) The positive sections on argyrophil stain all expressed NE markers. (4) Positive NE markers for tumors > 5 cm was 64.1%, but in non-SCLC, only 31.8% of tumors larger than 5 cm diameter had negative NE. The above results indicate that the use of NE markers in lung cancer is reliable, sensitive and practical. The relation between NE differentiation and biological behavior requires further study.

The octamer/mu E4 region of the immunoglobulin heavy-chain enhancer mediates gene repression in myeloma x T-lymphoma hybrids

We have shown previously that the immunoglobulin heavy-chain enhancer acts as a repressor of gene transcription in hybrids between immunoglobulin-producing myelomas and a T-lymphoma line. We have now mapped this repressive activity to a 51-bp enhancer subfragment which contains the octamer and mu E4 protein-binding motifs. Even a single copy of this subfragment will repress gene expression in hybrid cells. Mutational analyses of the repressor fragment suggest that in non-B cells, a strong transcriptional repressor(s) functions through the same motifs important for gene activation in B cells. Changes in chromatin structure that accompany reporter gene repression suggest a general mechanism for prohibiting immunoglobulin heavy-chain locus activation in inappropriate cell types.

Selenium content of sheep's milk and its distribution in protein fractions

The selenium (Se) distribution in sheep's milk is reported. Skim milk was found to contain the major part (98%) of total milk Se. The Se distribution over casein and whey protein fractions depends on the separation method used, but irrespective of these methods, skim milk Se is mainly associated with the casein fraction (> 68%). Approximately 11%, 4% and 17% Se is removed by dialysis (molecular mass cut-off 10-12 kDa) from skim milk, casein and whey respectively, indicating a major association of Se with milk proteins. This observation is confirmed through Se analysis of individual caseins and whey proteins isolated through ion-exchange chromatography and gel filtration. Se concentrations of the different isolated milk proteins show considerable variations (caseins, 304-750 ng Se/g; whey proteins, 241-806 ng Se/g).

Simian immunodeficiency virus-specific cytotoxic T lymphocytes in rhesus monkeys: characterization and vaccine induction

An effective HIV vaccine should be capable of eliciting virus-specific cytotoxic T lymphocytes (CTL). We have characterized the cellular and molecular features of a simian immunodeficiency virus of macaques (SIVmac) gag-specific CTL response in rhesus monkeys. We have shown that SIVmac-infected rhesus monkeys expressing the major histocompatibility complex (MHC) class I molecule Mamu-A*01 develop a SIVmac gag-specific CTL response which recognizes a 9 amino acid fragment of the gag protein in association with Mamu-A*01. Moreover, this peptide/MHC class I recognition is mediated by T cell receptors (TCR) employing a predominant V beta gene family and J beta gene. Using this understanding of a SIVmac-specific CTL response, we have shown that SIVmac-specific CTL can be elicited through three novel approaches to vaccination: a recombinant viral vector, a recombinant bacterial vector and a peptide vaccine. These studies illustrate the utility of the SIV/macaque model in AIDS vaccine research.

[Effects of combined therapy of traditional Chinese and Western medicine on C-reactive protein in post-debridement patients]

Closely monitoring whether the secondary infection in the patients of post-debridement occurred or not and appropriately treating these patients were the important ways to reduce the incidence of infection. Through estimating the level of the serum C-reactive protein (CRP) as the monitoring index of infection, dynamically observed the effect of the combined traditional Chinese and Western medicine therapy (TCM-WM) on CRP after debridement, as was compared with the effect of the Western medicine therapy (WM) group in which only the WM was administrated. The result showed that the levels of CRP decreased in both TCM-WM and WM group on 4th day after the operation, but the level of CRP in former group was lower than that in latter one, the difference was very significant (P < 0.001). So that, it was assumed that TCM-WM significantly excelled the WM on affecting the level of CRP and reducing the incidence of infection. It was suggested that CRP could be used as an effective and objective index to determine whether the secondary infection has happened and to assess the efficacy of some drugs.

Immunohistochemical mapping of angiotensin AT1 receptors in the brain

A new approach to study angiotensin receptor distribution in the brain has been taken by developing antibodies to partial sequence of the angiotensin II (AII) type-1 receptor subtype (AT1) and demonstrating the presence of receptors with immunohistochemical staining. The antibody to a portion of the 3rd cytoplasmic loop of the AT1 receptor revealed distinctive punctate immunoreactive staining on cell bodies. The cell bodies were distributed in the forebrain in paraventricular and supraoptic nuclei, the organum vasculosum lamina terminalis, median preoptic area and subfornical organ. In the brainstem, the entire locus coeruleus was stained, together with the adjacent mesencephalic and motor nuclei of the trigeminal nerve. The auditory system including the cochlear nucleus and superior olivary nuclei were stained. In the medulla, all the structures involved in blood pressure control were stained including the nucleus of the solitary tract, the 12th nerve nuclei, the rostroventral lateral area and the nucleus ambiguous. Sites where AT2 receptors are located were not stained or staining was limited to specific area such as the medial accessory nucleus of the inferior olive. Immunocytochemical staining of AT1 receptors provides a new and more precise approach to the cellular localization of AII receptors.

Recombinant soluble IgA Fc receptor: generation, biochemical characterization, and functional analysis of the recombinant protein

We previously described the cloning of a human myeloid cell surface receptor for the Fc region of immunoglobulin A (Fc alpha R). In the present study, a soluble version of the Fc alpha R (solFc alpha R) was generated by removing the transmembrane and cytoplasmic coding regions from full-length Fc alpha R cDNA and ligating into a mammalian expression vector. COS-7 cells transfected with the solFc alpha R plasmid secreted a protein that inhibited both immunoglobulin A (IgA) and anti-Fc alpha R monoclonal antibody (mAb) binding to Fc alpha R+ U937 cells. Furthermore, the solFc alpha R bound specifically to and could be eluted from an anti-Fc alpha R mAb-immunoaffinity column, retaining biological activity. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the recombinant full-length Fc alpha R migrates over a molecular mass range of approximately 40-60 kd, consistent with the reported size and heterogeneity of the naturally occurring myeloid cell surface Fc alpha R. The solFc alpha R ran on SDS-PAGE as a smaller band (37-55 kd) that reduced to two bands of 23 and 25 kd following N-glycanase treatment, indicating that the Fc alpha R is a heavily glycosylated protein. The biochemical data, coupled with flow cytometry studies showing that the recombinant Fc alpha Rs bind to five different anti-Fc alpha R mAbs, clearly demonstrate that the cloned Fc alpha R corresponds directly to the major Fc alpha R species expressed on human monocytes, neutrophils, and myeloid cell lines. The generation of soluble receptor protein will permit investigations of the role of Fc alpha R in IgA-mediated immunoregulation, effector functions, and disease.

Selenium distribution in egg white proteins

The present studies were undertaken to characterize selenium distribution in egg white. Ion-exchange chromatography fast protein liquid chromatography (FPLC) and flow injection atomic (absorption) spectrometry (FIAS) were used to separate egg white proteins and to determine the selenium content of different fractions. After purification, nine different proteins were identified with sodium dodecyl sulphate-polyacrylamide gel electrophoresis and 56% of the total selenium content was found to be associated with ovalbumin-1 and -2 (+/- 500 ng/g), which is the main protein in egg white. Flavoprotein was determined to be the richest selenium-containing protein (1800 ng/g). The selenium content of the other proteins (lysozyme, conalbumin, globulins and ovomucoid) ranged from 359 to 1094 ng/g.

Immunization with lentivirus-like particles elicits a potent SIV-specific recall cytotoxic T-lymphocyte response in rhesus monkeys

An effective acquired immunodeficiency syndrome (AIDS) vaccine should be capable of eliciting human immunodeficiency virus (HIV)-specific cytotoxic T-lymphocyte (CTL) responses. We have explored the use of lentivirus-like particles produced in mammalian cells infected with a recombinant vaccinia virus to immunize for the induction of CTL in the simian immunodeficiency virus (SIV)/rhesus monkey model for AIDS. SIV-like particles in a threonyl-MDP-based adjuvant did not elicit a high frequency of SIV gag-specific effector cells in naive rhesus monkeys. However, immunization with these particles elicited a potent recall CTL response in monkeys previously vaccinated with a recombinant vaccinia-SIV virus. These observations suggest that poxvirus-produced virus-like particles may represent a safe immunogen for use in periodic boosting to maintain viable cell-mediated immunity to the AIDS virus.

Role of oxygen intermediates in cytotoxicity: studies in chronic granulomatous disease

The ability of human neutrophils to lyse various target cells was investigated using cells from normal individuals and from patients with chronic granulomatous disease (CGD) whose cells lack the ability to form reactive oxygen intermediates (ROI). Cytolysis was stimulated by phorbol myristate acetate (PMA), rabbit antiserum, and a heteroantibody that binds to both the FcRII receptor of neutrophils and to the target. The PMA-activated CGD neutrophils were deficient compared to controls in killing both tumor and chicken erythrocyte (CRBC) targets at all effector-target ratios in 18-h assays. When CRBC were sensitized with rabbit antiserum, the normal cells still killed slightly more. When killing of CRBC was mediated by the heteroantibody, however, cytotoxicity of CGD neutrophils exceeded that of normal cells. CGD mononuclear cells (MNC) killed tumor cell targets as well as or better than normal MNC. Thus, PMA-mediated cytolysis appears to depend primarily upon the ability of the cell to generate ROI whereas antibody-mediated cytotoxicity and MNC-mediated lysis of tumor cells do not require ROI formation.

Verapamil regulation of a defective SR release channel in the cardiomyopathic Syrian hamster

The Bio 14.6 Cardiomyopathic Syrian Hamster (CMH) has an autosomal recessive disease characterized by intracellular calcium overload, cardiac and skeletal myopathies and premature death from congestive heart failure. Early treatment of these animals with the calcium antagonist, verapamil (V), prevents the development of the disease. We have previously provided evidence supporting a specific defect in the ryanodine-sensitive SR calcium release channel (SRCRC) in CMH. We now provide physiologic and biochemical evidence that V modulates SRCRC. Papillary muscles prepared from F1B control hamsters (F1B) revealed an enhanced inotropic responsiveness to V and ryanodine (R) with age, not seen with CMH. CMH papillary muscles demonstrated paradoxical positive inotropic effects of V and R not shared with F1B. The positive inotropic effects of V and R were not additive. V enhanced the affinity (decreased KD) of [3H]ryanodine binding to cardiac membranes. Thus, V may prevent the overt manifestations of genetic disease in CMH by modulating a defective ryanodine-sensitive SR release channel.

Positive inotropic effect of acetylcysteine in cardiomyopathic Syrian hamsters

Several laboratories have provided indirect evidence that the myocardium of the cardiomyopathic Syrian hamster (CMH) is chronically ischemic on the basis of microvascular spasm. We previously reported evidence supporting a defect in the ryanodine-sensitive sarcoplasmic reticulum calcium release channel (SRCRC) in CMH. A relation between alterations in SRCRC and chronic ischemia has not yet been explored. A potential mechanism could be the effects of changes in redox state on thiol groups. Thiol reagents have previously been shown to regulate calcium release from SRCRC. Accordingly, we studied the inotropic effects of the sulfhydryl donors, acetylcysteine (AC), cysteine, and cystine in CMH. AC was a positive inotrope in isolated papillary muscles prepared from CMH, but not F1B controls (F1B) (p < 0.01). No significant differences were noted in inotropic responses to cysteine or cystine. AC blunted the response of CMH > F1B control papillary muscle preparations to stimulation frequency (p < 0.01). The actual tension generated (in mg/mm2) by CMH was no longer different than F1B with addition of AC (10(-3) M), ryanodine (10(-8) M), or verapamil (5 x 10(-7) M). These findings are consistent with a defect in SRCRC in CMH. This defect may be primary or may provide a novel mechanism for hibernating myocardium owing to chronic ischemia.

Cytotoxic T lymphocytes do not appear to select for mutations in an immunodominant epitope of simian immunodeficiency virus gag

Studies to date assessing HIV escape from CTL in vivo have yielded conflicting results. Previous studies have demonstrated that simian immunodeficiency virus of macaques (SIVmac)-infected rhesus monkeys expressing the MHC class I allele Mamu-A*01 reproducibly develop a gag-specific CTL response limited to a 9-amino acid epitope of the SIVmac gag protein (residues 182-190 within peptide 11C). To determine whether CTL have a role in selecting for AIDS virus mutants, we examined mutations in SIVmac proviral DNA encoding this gag CTL epitope in PBL of infected rhesus monkeys. Three Mamu-A*01+ rhesus monkeys were infected with SIVmac and assessed for gag- and peptide 11C-specific CTL responses. This specific CTL response was maintained in two monkeys, but lost in the third animal 2 yr after infection. The generation of proviral gag mutations was then determined by sequencing 500-bp proviral fragments amplified from fresh PBL obtained from the monkeys more than 2.5 yr after infection. Although numerous point mutations were characterized in 131 polymerase chain reaction-generated clones of SIVmac gag, only four mutations within the gag CTL epitope-coding region of the genome were identified. Comparison of synonymous and nonsynonymous nucleotide substitutions in the regions encoding peptide 11C (p11C) and the flanking gag protein indicated a lack of selective pressure for viral mutations in the CTL epitope coding region. Interestingly, a predominant gag mutant encoding a single amino acid change in p11C was found in a monkey which lost its CTL activity. However, even in this setting there was no evidence for selection of mutations in the CTL epitope coding region when compared with the flanking region. Furthermore, synthetic peptides corresponding to all naturally occurring variants in the gag epitope-coding region were recognized by cloned and bulk cultured effector cells of the infected monkeys with persistent CTL. These results indicate that SIVmac gag- and p11C-specific CTL do not select for mutations in the immunodominant epitope-coding region and that the naturally occurring mutants do not appear to escape CTL recognition.