Diamond surface functionalization via visible light-driven C-H activation for nanoscale quantum sensing

Nitrogen-vacancy (NV) centers in diamond are a promising platform for nanoscale NMR sensing. Despite significant progress toward using NV centers to detect and localize nuclear spins down to the single spin level, NV-based spectroscopy of individual, intact, arbitrary target molecules remains elusive. Such sensing requires that target molecules are immobilized within nanometers of NV centers with long spin coherence. The inert nature of diamond typically requires harsh functionalization techniques such as thermal annealing or plasma processing, limiting the scope of functional groups that can be attached to the surface. Solution-phase chemical methods can be readily generalized to install diverse functional groups, but they have not been widely explored for single-crystal diamond surfaces. Moreover, realizing shallow NV centers with long spin coherence times requires highly ordered single-crystal surfaces, and solution-phase functionalization has not yet been shown with such demanding conditions. In this work, we report a versatile strategy to directly functionalize C-H bonds on single-crystal diamond surfaces under ambient conditions using visible light, forming C-F, C-Cl, C-S, and C-N bonds at the surface. This method is compatible with NV centers within 10 nm of the surface with spin coherence times comparable to the state of the art. As a proof-of-principle demonstration, we use shallow ensembles of NV centers to detect nuclear spins from surface-bound functional groups. Our approach to surface functionalization opens the door to deploying NV centers as a tool for chemical sensing and single-molecule spectroscopy.

Chemical Recycling of Thiol Epoxy Thermosets via Light-Driven C-C Bond Cleavage

Epoxy thermosets are high-volume materials that play a central role in a wide range of engineering applications; however, technologies to recycle these polymers remain rare. Here, we present a catalytic, light-driven method that enables chemical recycling of industrially relevant thiol epoxy thermosets to their original monomer at ambient temperature. This strategy relies on the proton-coupled electron transfer (PCET) activation of hydroxy groups within the polymer network to generate key alkoxy radicals that promote the fragmentation of the polymer through C-C bond β-scission. The method fully depolymerizes insoluble thiol epoxy thermosets into well-defined mixtures of small-molecule products, which can collectively be converted into the original monomer via a one-step dealkylation process. Notably, this process is selective and efficient even in the presence of other commodity plastics and additives commonly found in commercial applications. These results constitute an important step toward making epoxy thermosets recyclable and more generally exemplify the potential of PCET to offer a more sustainable end-of-life for a diverse array of commercial plastics.

Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

We present here a review of the photochemical and electrochemical applications of multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms in which both an electron and a proton are exchanged together, often in a concerted elementary step. As such, MS-PCET can function as a non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from a wide variety of common organic functional groups. We present an introduction to MS-PCET and a practitioner's guide to reaction design, with an emphasis on the unique energetic and selectivity features that are characteristic of this reaction class. We then present chapters on oxidative N-H, O-H, S-H, and C-H bond homolysis methods, for the generation of the corresponding neutral radical species. Then, chapters for reductive PCET activations involving carbonyl, imine, other X═Y π-systems, and heteroarenes, where neutral ketyl, α-amino, and heteroarene-derived radicals can be generated. Finally, we present chapters on the applications of MS-PCET in asymmetric catalysis and in materials and device applications. Within each chapter, we subdivide by the functional group undergoing homolysis, and thereafter by the type of transformation being promoted. Methods published prior to the end of December 2020 are presented.

Depolymerization of Hydroxylated Polymers via Light-Driven C-C Bond Cleavage

The accumulation of persistent plastic waste in the environment is widely recognized as an ecological crisis. New chemical technologies are necessary both to recycle existing plastic waste streams into high-value chemical feedstocks and to develop next-generation materials that are degradable by design. Here, we report a catalytic methodology for the depolymerization of a commercial phenoxy resin and high molecular weight hydroxylated polyolefin derivatives upon visible light irradiation near ambient temperature. Proton-coupled electron transfer (PCET) activation of hydroxyl groups periodically spaced along the polymer backbone furnishes reactive alkoxy radicals that promote chain fragmentation through C-C bond β-scission. The depolymerization produces well-defined and isolable product mixtures that are readily diversified to polycondensation monomers. In addition to controlling depolymerization, the hydroxyl group modulates the thermomechanical properties of these polyolefin derivatives, yielding materials with diverse properties. These results demonstrate a new approach to polymer recycling based on light-driven C-C bond cleavage that has the potential to establish new links within a circular polymer economy and influence the development of new degradable-by-design polyolefin materials.

Reservation Lands as a Protective Social Factor: An Analysis of Psychological Distress among Two American Indian Tribes

The unique physical, cultural, and ecological location of U.S. American Indian reservations simultaneously presents risks for mental health and offers sources of resilience to Native peoples. Using survey data from two American Indian tribes, we explore whether the length of one's life spent on a reservation is associated with lower odds of psychological distress. In both tribes, we find that individuals who live a vast majority of their lives on the reservation have lower odds of psychological distress than individuals who spent portions of their life off or near the reservation. These findings suggest a need to reframe the perception of life experience on tribal reservations but also call for a more nuanced investigation of the life experience of American Indians. This study illustrates the importance of deeply exploring the relationship that American Indians have with their tribal reservation lands.

Opposing consequences of IL-23 signaling mediated by innate and adaptive cells in chemically induced colitis in mice

The interleukin-23 (IL-23) pathway has emerged as a promising therapeutic target for inflammatory bowel disease. Although the pathogenic role of IL-23 receptor (IL-23R) on T lymphocytes is well established, its function on innate immune cells has not been thoroughly examined. Here we investigate the consequence of IL-23R deletion in dextran sulfate sodium (DSS)-induced colitis. In IL23R(-/-) and IL23p19(-/-) mice, we observed decreased weight loss and reduced leukocyte infiltrate following DSS exposure. Surprisingly, when the IL-23R(-/-) allele was crossed into Rag2(-/-) mice, we observed exacerbated disease, increased epithelial damage, reduced pSTAT3 in the epithelium, and delayed recovery of IL23R(-/-)Rag2(-/-) mice. This phenotype was rescued with exogenous IL22-Fc, and epithelial pSTAT3 was restored. Depletion of Thy1(+) innate lymphoid cells eliminated the majority of IL-22 production in the colon lamina propria of DSS-treated Rag2(-/-) mice, suggesting that these are the major IL-23 responsive innate cells in this context. In summary, we provide evidence for opposing consequences of IL-23R on innate and adaptive lymphoid cells in murine colitis.

Analysis of vaccine-virus-associated rabies cases in red foxes (Vulpes vulpes) after oral rabies vaccination campaigns in Germany and Austria

To eradicate rabies in foxes, almost 97 million oral rabies vaccine baits have been distributed in Germany and Austria since 1983 and 1986, respectively. Since 2007, no terrestrial cases have been reported in either country. The most widely used oral rabies vaccine viruses in these countries were SAD (Street Alabama Dufferin) strains, e.g. SAD B19 (53.2%) and SAD P5/88 (44.5%). In this paper, we describe six possible vaccine-virus-associated rabies cases in red foxes (Vulpes vulpes) detected during post-vaccination surveillance from 2001 to 2006, involving two different vaccines and different batches. Compared to prototypic vaccine strains, full-genome sequencing revealed between 1 and 5 single nucleotide alterations in the L gene in 5 of 6 SAD isolates, resulting in up to two amino acid substitutions. However, experimental infection of juvenile foxes showed that those mutations had no influence on pathogenicity. The cases described here, coming from geographically widely separated regions, do not represent a spatial cluster. More importantly, enhanced surveillance showed that the vaccine viruses involved did not become established in the red fox population. It seems that the number of reported vaccine virus-associated rabies cases is determined predominantly by the intensity of surveillance after the oral rabies vaccination campaign and not by the selection of strains.

Evaluation of aldrithiol-2-inactivated preparations of HIV type 1 subtypes A, B, and D as reagents to monitor T cell responses

The development of HIV vaccines is an urgent priority and there is need to generate reagents representing multiple subtypes that can be used to screen HIV-1-specific responses. We used Aldrithiol-2 (AT-2), a mild oxidizing reagent, to eliminate the infectivity of HIV while maintaining its structure and ability to be processed for presentation to T cells. Inactivated subtype A, B, and D viruses were evaluated for their ability to stimulate T cell responses in PBMC samples from 18 U.S. subjects infected with HIV-1 subtype B and 32 Ugandan subjects infected with subtypes A and D or recombinants AC and AD. Five HIV-1-negative samples were also analyzed. T cell responses to AT-2-inactivated viral isolates were monitored by interferon-gamma (IFN-gamma) intracellular cytokine secretion (ICS) analysis; matched microvesicle preparations served as negative controls. Among the 18 subtype B infected subjects, 39% had CD3(+) CD4 (+) IFN-gamma responses and 67% had CD3(+) CD8(+) IFN-gamma responses. Of the 32 Ugandan subjects, 34% demonstrated CD3(+) CD4(+) IFN-gamma responses and 78% demonstrated CD3(+) CD8(+) IFN-gamma responses. Both subtype-specific and cross-reactive responses were observed. Responses to the AT-2 viruses tended to be lower in magnitude than those detected by a set of overlapping gag peptides. Robust lymphoproliferative responses to AT-2 viruses were seen in a subset of subjects. In conclusion, AT-2-inactivated HIV-1 virions stimulated both CD4 and CD8 HIV-1-specific responses and may provide an additional reagent for screening HIV-1-specific responses in HIV seropositives and vaccinees.

The effect of herbal supplementation on the severity of exercise-induced pulmonary haemorrhage

Exercise-induced pulmonary haemorrhage (EIPH) is a serious condition that affects the health and possibly the performance of all racehorses. However, only two treatments, furosemide and the Flair™ equine nasal strip, both of which reduce capillary transmural pressure, have been successful in reducing EIPH. Alternatively, transient impairment of platelet function and coagulation during exercise has been considered an additional contributor to EIPH. Consequently, herbal formulations designed to enhance platelet function, and hence coagulation, are hypothesized to reduce EIPH. To investigate the validity of this hypothesis, five Thoroughbred horses completed three maximal incremental exercise tests on a 10% inclined treadmill in a randomized cross-over design experiment. Treatments included twice daily oral administration (for 3 days) of a placebo (PL; cornstarch) and two herbal formulas, Yunnan Paiyao (YP) or Single Immortal (SI). Blood samples for coagulation profiles, complete blood counts and biochemistry profiles were collected before each exercise test. During each test, pulmonary arterial pressure, oxygen uptake, arterial blood gases, plasma lactate and time-to-fatigue were measured. Severity of EIPH was quantified via bronchoalveolar lavage (BAL) at 30–60 min post-exercise. The herbal formulations were not effective in decreasing EIPH (×106 red blood cells ml−1 BAL fluid: PL, 27.1±11.6; YP, 33.2±23.4; SI, 35.3±15.4, P>0.05) or in changing any of the other variables measured with the exception of time-to-fatigue, which was slightly but significantly prolonged by Single Immortal compared with placebo and Yunnan Paiyao (PL, 670±9.6 s; YP, 665±5.5 s; SI, 685±7.9 s, P<0.05). Thus, these results do not support the use of these herbal formulations in the prevention of EIPH.

Regular exposure to rabies virus and lack of symptomatic disease in Serengeti spotted hyenas

We report a previously unrecognized complexity to the ecology of rabies in wildlife. Rabies-specific virus-neutralizing antibodies in spotted hyenas, the most numerous large carnivore in the Serengeti ecosystem (Tanzania, East Africa), revealed a high frequency of exposure of 37.0% to rabies virus, and reverse transcriptase (RT) PCR demonstrated rabies RNA in 13.0% of hyenas. Despite this high frequency, exposure neither caused symptomatic rabies nor decreased survival among members of hyena social groups monitored for 9 to 13 years. Repeated, intermittent presence of virus in saliva of 45.5% of seropositive hyenas indicated a "carrier" state. Rabies isolates from Serengeti hyenas differed significantly (8.5% sequence divergence) from those isolated from other Serengeti carnivores, suggesting that at least two separate strains circulate within the Serengeti carnivore community. This finding is consistent with the fact that exposure in hyenas increased with age and social status, following a pattern predicted by intraspecific age and social-status-dependent oral and bite contact rates. High seroprevalence of rabies, low basic reproductive rate of the virus (R(0)) of 1.9, a carrier state, and the absence of symptomatic rabies in a carnivore in an ecosystem with multihost and multistrain maintenance has not been previously demonstrated for rabies. Because of the substantial differences between the hyena viral isolates and those from canids and viverrids in the Serengeti, it is unlikely that spotted hyenas were the source of rabies virus that killed several African wild dog packs in the Serengeti ecosystem in the 1990s.

Selective increases in HIV-specific neutralizing antibody and partial reconstitution of cellular immune responses during prolonged, successful drug therapy of HIV infection

Because the immune response to HIV depends on viral gene expression, we examined the HIV-specific immune responses in persons whose viral load after highly active antiretroviral therapy (HAART) was <400 on at least 3 occasions over a 12-month interval. Eleven patients were identified. While there was little change in mean HIV-binding antibody (Ab) titers in this group, two persons mounted increases in HIV envelope-specific binding antibody. Neutralizing antibody (NAb) titers against a panel of HIV-1 primary isolates (BZ167, US1, and CM237) increased post-HAART (80% neutralization titer against US1, p = 0.06; against CM237, p = 0.04). The two persons with large increases in binding antibody also had increases in primary isolate NAb. Roughly half of HAART recipients had significant increases in neutralizing antibody to the primary isolates US1 and CM237. Compared with CD4-matched, non-HAART controls, there were significant increases in NAb against the subtype B primary isolate US1 (p < 0.0009); no increases were seen against more easily neutralized primary isolate BZ167. There were no differences after HAART in antibody-directed cellular cytotoxicity (ADCC). HAART resulted in a partial restoration of lymphoproliferative responses to recall antigens (tetanus and diphtheria). New responses developed to HIV Gag p24. No patient responded to HIV Env gp160 or gp120 either before or after HAART. The data underscore the lack of functional reconstitution of HIV-specific, CD4-mediated responses despite durable suppression of viral replication. In the setting of stable anti-HIV Ab levels, the development of increased NAb in certain individuals suggests that control of the virus by HAART may assist in immune control of HIV.

A Novel Approach to Antigen-Specific Deletion of CTL with Minimal Cellular Activation Using α3 Domain Mutants of MHC Class I/Peptide Complex

In this study, we have compared the effector functions and fate of a number of human CTL clones in vitro or ex vivo following contact with variant peptides presented either on the cell surface or in a soluble multimeric format. In the presence of CD8 coreceptor binding, there is a good correlation between TCR signaling, killing of the targets, and FasL-mediated CTL apoptosis. Blocking CD8 binding using alpha3 domain mutants of MHC class I results in much reduced signaling and reduced killing of the targets. Surprisingly, however, FasL expression is induced to a similar degree on these CTLs, and apoptosis of CTL is unaffected. The ability to divorce these events may allow the deletion of antigen-specific and pathological CTL populations without the deleterious effects induced by full CTL activation.

Differential transcription attenuation of rabies virus genes by intergenic regions: generation of recombinant viruses overexpressing the polymerase gene

Gene expression of nonsegmented negative-sense RNA viruses involves sequential synthesis of monocistronic mRNAs and transcriptional attenuation at gene borders resulting in a transcript gradient. To address the role of the heterogeneous rabies virus (RV) intergenic regions (IGRs) in transcription attenuation, we constructed bicistronic model RNAs in which two reporter genes are separated by the RV N/P gene border. Replacement of the 2-nucleotide (nt) N/P IGR with the 5-nt IGRs from the P/M or M/G border resulted in attenuation of downstream gene transcription to 78 or 81%, respectively. A severe attenuation to 11% was observed for the 24-nt G/L border. This indicated that attenuation in RV is correlated with the length of the IGR, and, in particular, severe downregulation of the L (polymerase) gene by the 24 nt IGR. By reverse genetics, we recovered viable RVs in which the strongly attenuating G/L gene border of wild-type (wt) RV (SAD L16) was replaced with N/P-derived gene borders (SAD T and SAD T2). In these viruses, transcription of L mRNA was enhanced by factors of 1.8 and 5.1, respectively, resulting in exaggerated general gene expression, faster growth, higher virus titers, and induction of cytopathic effects in cell culture. The major role of the IGR in attenuation was further confirmed by reintroduction of the wt 24-nt IGR into SAD T, resulting in a ninefold drop of L mRNA. The ability to modulate RV gene expression by altering transcriptional attenuation is an advantage in the study of virus protein functions and in the development of gene delivery vectors.

A comparative study of the impact of HIV infection on natural killer cell number and function in Thais and North Americans

Innate immunity may play a role in preventing HIV infection and progression to AIDS. Most studies of natural killer (NK) cell function have been conducted in populations with different HLA allele frequencies and HIV subtypes than those found in Southeast Asia. NK cell number and function, defined as CD3- cells expressing CD16+/CD56+ and the ability to lyse K562 cells, were enumerated in 42 HIV-seronegative Thais and 20 HIV-seronegative North Americans. The number and percentage of NK cells were similar for both groups, but cytotoxicity function expressed as lytic units (LU20) of NK cells was significantly greater in the Thai subjects compared with the North American subjects (p = 0.004). Comparisons were also conducted between the HIV-seronegative groups and HIV-infected subjects from both Thailand and North America. NK cell number and function were not significantly different between the Thai HIV-seronegative and -seropositive groups. However, the comparison between the North American HIV-seronegative and -seropositive subjects demonstrated profound impairment of NK cell number, percentage, and function (p < 0.001). Matching the Thai and North American HIV-infected subjects on CD4+ cell count revealed higher NK number and function in the Thai subjects (p < 0.001). The study indicates that NK function in both HIV-seronegative and -seropositive Thais is elevated relative to similar groups in North America.

Effect of short-term exercise training on leptin and insulin action

The purpose of the study was to determine the effect of short-term exercise training (7 consecutive days for 60 min/d at 75% maximal oxygen consumption [VO2 max]), which did not change body mass on fasting plasma leptin concentration and insulin action. Young, lean subjects (n = 16; age, 21.9 +/- 0.6 years; body fat, 17.5% +/- 1.5%) and older subjects with relatively more adipose tissue (n = 14; age, 58.6 +/- 1.4 years; body fat, 28.3% +/- 1.3%) were studied (mean +/- SE). Fasting plasma leptin was significantly (P < .05) related to adiposity (fat mass, r = .58; % body fat, r = .76) in this population. Body mass did not change (P < .05) in any of the groups with training (71.8 +/- 2.5 v 71.9 +/- 2.5 kg). The insulin sensitivity index (SI determined from an intravenous glucose tolerance test (IVGTT) improved significantly (P < .05) in both the young group (4.8 +/- 0.6 v6.9 +/- 0.8 x 10(-4)/ min (microU/mL) and the older group (3.2 +/- 0.6 v 5.9 +/- 1.0 x 10(-4)/min (microU/mL)). Fasting leptin did not change with training in either group (10.4 +/- 1.6 v 9.2 +/- 1.0 ng/mL). These findings suggest that exercise does not independently affect the fasting plasma leptin concentration and the improvement in insulin action with exercise is not associated with an alteration in fasting leptin in healthy sedentary lean and relatively lean subjects.

Pythiosis with bone lesions in a pregnant mare

A 9-year-old pregnant mare was referred for evaluation of a nonhealing wound of 8 weeks' duration on the lateral aspect of the left forelimb. A soft tissue mass encircled the proximal two thirds of the metacarpus; radiography revealed a moderate periosteal reaction affecting metacarpal bone i.v. Histologic and immunohistochemical examinations revealed eosinophilic granulomatous inflammation and Pythium sp in the soft tissues. The mare was treated for 12 days with antimicrobials, medicated wound dressings, debridement, and i.v. administration of sodium iodide; radiography revealed progression of the bone lesions. The mare was treated by regional arterial perfusion with miconazole and excision of affected soft tissues and the distal two thirds of metacarpal bone i.v. The mare recovered without complications and gave birth to a healthy foal. Regional perfusion of antifungal agents provides high concentrations in soft and osseous tissues and permits use of low dosages of agents administered by other routes, which reduces cost, adverse effects, and teratogenic effects.

Evaluation of natural killer cell activity

Natural killer (NK) cells are being appreciated not only for their ability to recognize and lyse tumor cells and virus-infected cells but also for their immunoregulatory properties. NK cells provide a first line of defense against invading pathogens with a two pronged attack, lysis of infected cells and secretion of cytokines and chemokines with potent antipathogen effects. This article describes the standard chromium release assay, which measures the ability of NK cells derived from the peripheral blood to lyse appropriate target cells.

Preliminary evaluation of human immunodeficiency virus type 1 (HIV-1) immunogen in children with HIV-1 infection

The safety and preliminary activity of human immunodeficiency virus type 1 (HIV-1) immunogen were evaluated in 10 HIV-1-infected children with disease stage N1,2 or A1,2. Multiple inoculations of 2. 5 or 10 units (U) of HIV-1 immunogen were safe and well tolerated without an acceleration of disease progression. When antiretroviral agents were coadministered, the 10 U dose appeared to be associated with more sustained reduction in plasma HIV-1 RNA than the 2.5 U dose (median log10 HIV-1 RNA at month 18, 3.07 vs. 4.01 copies/mL in 10 U [n=4] vs. 2.5 U [n=3], respectively; P=.034). Levels of regulated-on-activation, normal T cell-expressed and -secreted chemokine produced from HIV-1 immunogen-stimulated lymphocytes in vitro were increased in the children who had HIV-1 immunogen-specific antibody responses (P<.02) and appeared to be inversely correlated with levels of plasma HIV-1 RNA (P<.01). These preliminary data warrant larger studies to determine the effectiveness of adjunctive therapy with HIV-1 immunogen in children with HIV-1 infection.

Antibody-dependent cellular cytotoxicity in HIV type 1-infected patients receiving VaxSyn, a recombinant gp160 envelope vaccine

Antibody-dependent cellular cytotoxicity (ADCC) activity was measured in 60 human immunodeficiency virus (HIV-1)-infected patients receiving a recombinant gp160 (rgp160) envelope protein of HIV-1(NL4-3) in alum and 64 receiving placebo over a 5-year study period. There was no difference in the percentage of ADCC responders when comparing rgp160-immunized patients (mean, 78.4%) with those receiving placebo alone (mean, 81.5%) at any time point examined. Patients were further divided into progression groups regardless of their vaccine status. ADCC activity was somewhat higher in rapid than in slow-progressing groups, although the number that had detectable ADCC activity was equivalent in each group. ADCC activity of sera from rapid- and slow-progressing groups against primary or laboratory isolate envelopes was similar. This study showed that transcription with rgp160 did not appear to enhance HIV-specific ADCC activity. ADCC activity did not appear to correlate with protection against AIDS in this cohort of HIV-1-infected people.

Effect of aging on response to exercise training in humans: skeletal muscle GLUT-4 and insulin sensitivity

The purpose of this study was to compare the effects of short-term exercise training on insulin-responsive glucose transporter (GLUT-4) concentration and insulin sensitivity in young and older individuals. Young and older women [22.4 +/- 0.8 (SE) yr, n = 9; and 60.9 +/- 1. 0 yr, n = 10] and men (20.9 +/- 0.9, n = 9; 56.5 +/- 1.9 yr, n = 8), respectively, were studied before and after 7 consecutive days of exercise training (1 h/day, approximately 75% maximal oxygen uptake). The older groups had more adipose tissue, increased central adiposity, and a lower maximal oxygen uptake. Despite these differences, increases in whole body insulin action (insulin sensitivity index, determined with an intravenous glucose tolerance test and minimal-model analysis) with training were similar regardless of age, in both the women and men (mean increase of 2.2 +/- 0.3-fold). This was accompanied by similar relative increases in muscle (vastus lateralis) GLUT-4 protein concentration, irrespective of age (mean increase of 3.1 +/- 0.7-fold). Body mass did not change with training in any of the groups. These data suggest that older human skeletal muscle retains the ability to rapidly increase muscle GLUT-4 and improve insulin action with endurance training.

Evaluation of natural killer cell activity

The immune response to a virus infection involves both nonspecific and specific immune mechanisms. Natural killer (NK) cells are naturally-occurring cytolytic cells capable of lysing various tumor cells and virus-infected cells without previous sensitization or with a requirement for major histocompatibility (MHC) restriction. The molecular mechanisms that explain how NK cells are able to kill virus-infected cells and tumor cells while sparing self-cells have recently been elucidated (1). NK cells may play a role as a first line of defense against virus infection by mediating lysis of virus-infected cells prior to the development of specific humoral and cell-mediated defense mechanisms. Although the percentage of NK cells in HIV-1-infected patients may remain normal, the absolute numbers of some NK subsets are substantially reduced in the blood of HIV-1 patients and NK function decreases as HIV-1 infection proceeds (2-4). The interplay between NK cells and other cells of the innate and specific immune system is mediated, in part, through the release of cytokines, in particular interleukin-2 (IL-2) and γ-interferon (γ-IFN). Thus, it seems plausible that the generalized immunosuppression seen in HIV-1-infected patients may contribute to the impairment of NK activity. A dynamic balance between NK cells and cytotoxic T lymphocytes (CTL) is likely to occur (5). Therefore, any alterations in NK or CTL activity are likely to impair anti-HIV-1 cytolytic function.

HIV-1-Specific Cytotoxic T-Cell Assays

Cytotoxic T-cells (CTL) provide the basis of protective immunity in many viral infections by appearing early in the immune response and becoming involved with the elimination of virus by lysis of infected cells. A considerable amount of evidence suggests that CTL may be an especially important component of the host defense against HIV-1 (1,2) . Strong CTL activity is seen early during the course of infection (3,4), in nonprogressor individuals, some of whom have been infected for a decade or more with HIV-1 (5,6) and also in some HIV-1 exposed sex workers (7) and babies (8,9) who remain HIV-1-negative.

Correlation between humoral responses to human immunodeficiency virus type 1 envelope and disease progression in early-stage infection

Human immunodeficiency virus (HIV)-1-infected rapid and slow progressors showed differential humoral responses against HIV envelope peptides and proteins early in infection. Sera from slow progressors reacted more strongly with short envelope peptides modeling gp160NL4-3, predominantly in gp41. Reactivity to six peptides (in constant regions C3, C4, and C5 of gp120 and in gp41) correlated with slower progression. In a novel association, reactivity to three peptides (in constant regions C1 and C3 and variable region V3 of gp120) correlated with faster progression. Envelope peptide reactivity correlated with subsequent course of disease progression as strongly as did reactivity to gag p24. Patients heterozygous for 32-bp deletions in the CCR5 coreceptor reacted more frequently to an epitope in gp41. Rapid progressors had greater gp120 native-to-denatured binding ratios than did slow progressors. While antibody-dependent cellular cytotoxicity against gp120 did not strongly differentiate the groups, slow progressors showed a broader neutralization pattern against 5 primary virus isolates.

Cross-clade cytotoxic T cell response to human immunodeficiency virus type 1 proteins among HLA disparate North Americans and Thais

A globally effective vaccine will need to elicit cytotoxic T lymphocytes (CTL) capable of recognizing diverse human immunodeficiency virus type 1 (HIV-1) clades. Study of the cellular immune responses of HIV-1-infected persons may allow predictions to be made regarding useful vaccine antigen components. The frequency and magnitude of CTL responses to clade E and B Gag, Pol-RT, Env, and Nef proteins were compared in 12 HLA-characterized, clade E-infected Thais and in 10 clade B-infected North Americans using vaccinia recombinant constructs for protein expression. While responses were detected against all proteins, they were most frequent and cross-reactive to Gag in both groups. Pol-RT was recognized less frequently in Thais than North Americans. Cross-clade protein recognition was common but not uniformly present among these HLA-disparate individuals. Population-specific CTL data are needed to adequately prepare for vaccine trials outside of North America and Europe.

CD4+ and CD8+ T-lymphocytopenia in a filly with Pneumocystis carinii pneumonia

Decreased proportion of CD4+ and CD8+ T lymphocytes in peripheral blood likely contributed to susceptibility to Pneumocystis carinii in a foal. Cytological evaluation of bronchoalveolar lavage was required for identification of the pathogen and serial flow-cytometric analysis of peripheral blood lymphocytes documented transient low expression of CD4+ and CD8+ T lymphocytes. Although immunodeficiency is uncommon, it must be included in the differential diagnosis for patients suffering from chronic or opportunistic infections and may provide an indication for immunostimulant therapy.

Nucleic acid vaccine-induced immune responses require CD28 costimulation and are regulated by CTLA4

Immunization with plasmids expressing specific genes (DNA or nucleic acid vaccination (NAV)) elicits robust humoral and cell-mediated immune responses. The mechanisms involved in T cell activation by NAV are incompletely characterized. We have examined the costimulatory requirements of NAV. CD28-deficient mice did not mount Ab or CTL responses following i.m. immunization with eukaryotic expression plasmids encoding the bacterial gene beta-galactosidase (beta gal). Because these mice retained their ability to up-regulate the CTLA4 receptor (a negative regulator of T cell activation), we examined CTLA4's role in the response of wild-type BALB/c mice to NAV. Intact anti-CTLA4 mAb but not Fab fragments suppressed the primary humoral response to pCIA/beta gal without affecting recall responses, indicating CTLA4 activation inhibited Ab production but not T cell priming. Blockade of the ligands for CD28 and CTLA4, CD80 (B7-1) and CD86 (B7-2), revealed distinct and nonoverlapping function. Blockade of CD80 at initial immunization completely abrogated primary and secondary Ab responses, whereas blockade of CD86 suppressed primary but not secondary responses. Simultaneous blockade of CD80 + CD86 was less effective at suppressing Ab responses than either alone. Enhancement of costimulation via coinjection of B7-expressing plasmids augmented CTL responses but not Ab responses, and without evidence of Th1 to Th2 skewing. These findings suggest complex and distinct roles for CD28, CTLA4, CD80, and CD86 in T cell costimulation following nucleic acid vaccination.

CD4 glycoprotein degradation induced by human immunodeficiency virus type 1 Vpu protein requires the function of proteasomes and the ubiquitin-conjugating pathway

The human immunodeficiency virus type 1 (HIV-1) vpu gene encodes a type I anchored integral membrane phosphoprotein with two independent functions. First, it regulates virus release from a post-endoplasmic reticulum (ER) compartment by an ion channel activity mediated by its transmembrane anchor. Second, it induces the selective down regulation of host cell receptor proteins (CD4 and major histocompatibility complex class I molecules) in a process involving its phosphorylated cytoplasmic tail. In the present work, we show that the Vpu-induced proteolysis of nascent CD4 can be completely blocked by peptide aldehydes that act as competitive inhibitors of proteasome function and also by lactacystin, which blocks proteasome activity by covalently binding to the catalytic beta subunits of proteasomes. The sensitivity of Vpu-induced CD4 degradation to proteasome inhibitors paralleled the inhibition of proteasome degradation of a model ubiquitinated substrate. Characterization of CD4-associated oligosaccharides indicated that CD4 rescued from Vpu-induced degradation by proteasome inhibitors is exported from the ER to the Golgi complex. This finding suggests that retranslocation of CD4 from the ER to the cytosol may be coupled to its proteasomal degradation. CD4 degradation mediated by Vpu does not require the ER chaperone calnexin and is dependent on an intact ubiquitin-conjugating system. This was demonstrated by inhibition of CD4 degradation (i) in cells expressing a thermally inactivated form of the ubiquitin-activating enzyme E1 or (ii) following expression of a mutant form of ubiquitin (Lys48 mutated to Arg48) known to compromise ubiquitin targeting by interfering with the formation of polyubiquitin complexes. CD4 degradation was also prevented by altering the four Lys residues in its cytosolic domain to Arg, suggesting a role for ubiquitination of one or more of these residues in the process of degradation. The results clearly demonstrate a role for the cytosolic ubiquitin-proteasome pathway in the process of Vpu-induced CD4 degradation. In contrast to other viral proteins (human cytomegalovirus US2 and US11), however, whose translocation of host ER molecules into the cytosol occurs in the presence of proteasome inhibitors, Vpu-targeted CD4 remains in the ER in a transport-competent form when proteasome activity is blocked.

Highly stable expression of a foreign gene from rabies virus vectors

A reverse genetics approach was applied to generate a chimeric nonsegmented negative strand RNA virus, rabies virus (RV) of the Rhabdoviridae family, that expresses a foreign protein. DNA constructs containing the entire open reading frame of the bacterial chloramphenicol acetyltransferase (CAT) gene and an upstream RV cistron border sequence were inserted either into the nontranslated pseudogene region of a full-length cDNA copy of the RV genome or exchanged with the pseudogene region. After intracellular T7 RNA polymerase-driven expression of full-length antigenome RNA transcripts and RV nucleoprotein, phosphoprotein and polymerase from transfected plasmids, RVs transcribing novel monocistronic mRNAs and expressing CAT at high levels, were recovered. The chimeric viruses possessed the growth characteristics of standard RV and were genetically stable upon serial cell culture passages. CAT activity was still observed in cell cultures infected with viruses passaged for more than 25 times. Based on the unprecedented stability of the chimeric RNA genomes, which is most likely due to the structure of the rhabdoviral ribonucleoprotein complex, we predict the successful future use of recombinant rhabdovirus vectors for displaying foreign antigens or delivering therapeutic genes.

CD4+ T-lymphocyte lines developed from HIV-1-seropositive patients recognize different epitopes within the V3 loop

To define the epitopes present within the V3 loop sequence recognized by five HIV-1 envelope-specific T-cell lines, a panel of V3 LAI peptides bearing sequential truncations from both the N- and C-terminus was synthesized and tested for their ability to induce proliferation. Each individual T-cell line had a different pattern of response against the truncated V3 peptides, demonstrating the presence of a cluster of CD4+ T-cell epitopes within the V3 loop. To assess the ability of these envelope-specific T-cell lines to recognize and proliferate in response to V3 loops of different viral strains, they were tested against a panel of heterologous V3 loop peptides derived from different viral genotypes within and outside of HIV-1 clade B. There was no proliferative response against heterologous V3 loops by any of the lines, demonstrating that recognition of the V3 epitopes is highly strain specific. One of the defined epitopes was shown to elicit a cytotoxic response as well, suggesting the multifaceted role that the CD4+ T cell might play in HIV-1 disease.

Single- and multiple-dose-response relationships of beta-carotene in cystic fibrosis

Concentrations of carotenoids are low in patients with cystic fibrosis (CF) and are associated with essential fatty acid deficiency and increased markers of inflammation. We conducted single- and multiple-dose studies of beta-carotene supplementation in patients with CF. Dose-proportional increases in beta-carotene concentrations were found, although clearance was independent of dose. Large doses of beta-carotene were necessary to achieve normal plasma levels.

Establishment and characterization of human immunodeficiency virus type 1 (HIV-1) envelope-specific CD4+ T lymphocyte lines from HIV-1-seropositive patients

Human immunodeficiency virus type 1 (HIV-1) gp160-, gp120-, and tetanus toxoid-specific CD4+ T lymphocyte lines were developed from 11 HIV-1-seropositive volunteers enrolled in a vaccine therapy trial. Of the 20 HIV-1 envelope-specific T cell lines, 9 were challenged with a panel of overlapping peptides spanning the gp120LAI sequence. The most frequently recognized regions were amino acids 74-105 in the C1 region and 306-328 in the V3 region. When tested against a panel of divergent HIV-1 envelopes, 55% of the envelope-specific lines were able to recognize gp120MN, while only 22% recognized gp120SF2. Cytotoxicity testing with HIV-1 envelope antigen or peptides demonstrated killing by all 3 envelope-specific lines tested. Supernatants from 2 of 9 lines had high titers of p24 gag antigen, which did not seem to interfere with functional properties.

Presentation of endogenous and exogenous antigens is not affected by inactivation of E1 ubiquitin-activating enzyme in temperature-sensitive cell lines

Little is known regarding the mechanism by which MHC class I-associated peptides are generated. Proteins can be targeted for degradation by the covalent attachment of ubiquitin. The first step in ubiquitin conjugation to proteins is its binding to E1 ubiquitin-activating enzyme. To study the role of ubiquitin-targeted protein degradation in Ag processing, we used two mutant cell lines with temperature-sensitive E1 proteins, and a recombinant vaccinia virus expressing wild-type human E1. One of the cell lines examined (hamster ts20 cells) was previously reported to have a minimal capacity after a 1-h incubation at 41 degrees C to present osmotically loaded OVA to a T cell hybridoma, as assessed by IL-2 release. Even after incubating the same cells for 1 h at 43 degrees C, we failed to detect an E1-related decrease in the presentation of biosynthesized or osmotically loaded OVA to splenic T cells, as measured by target cell lysis. We introduce the use of mouse tsA1S9 cells to Ag-processing studies and provide the initial biochemical characterization of their defect in protein ubiquitination. Relative to parental L929 cells, after thermal inactivation of E1, these cells actually demonstrate enhanced presentation of endogenous or exogenous viral Ags to T cells. Our findings do not support a role for protein ubiquitination in Ag processing, and indicate that either the temperature-sensitive cell lines examined do not exhibit a sufficient reduction in ubiquitin-conjugating activity to affect the generation of antigenic peptides, or that ubiquitin-targeted proteolysis is not essential for processing the two exogenous and six endogenous Ags examined.

Presentation of endogenous and exogenous antigens is not affected by inactivation of E1 ubiquitin-activating enzyme in temperature-sensitive cell lines

Little is known regarding the mechanism by which MHC class I-associated peptides are generated. Proteins can be targeted for degradation by the covalent attachment of ubiquitin. The first step in ubiquitin conjugation to proteins is its binding to E1 ubiquitin-activating enzyme. To study the role of ubiquitin-targeted protein degradation in Ag processing, we used two mutant cell lines with temperature-sensitive E1 proteins, and a recombinant vaccinia virus expressing wild-type human E1. One of the cell lines examined (hamster ts20 cells) was previously reported to have a minimal capacity after a 1-h incubation at 41 degrees C to present osmotically loaded OVA to a T cell hybridoma, as assessed by IL-2 release. Even after incubating the same cells for 1 h at 43 degrees C, we failed to detect an E1-related decrease in the presentation of biosynthesized or osmotically loaded OVA to splenic T cells, as measured by target cell lysis. We introduce the use of mouse tsA1S9 cells to Ag-processing studies and provide the initial biochemical characterization of their defect in protein ubiquitination. Relative to parental L929 cells, after thermal inactivation of E1, these cells actually demonstrate enhanced presentation of endogenous or exogenous viral Ags to T cells. Our findings do not support a role for protein ubiquitination in Ag processing, and indicate that either the temperature-sensitive cell lines examined do not exhibit a sufficient reduction in ubiquitin-conjugating activity to affect the generation of antigenic peptides, or that ubiquitin-targeted proteolysis is not essential for processing the two exogenous and six endogenous Ags examined.

Expression of adenovirus E3/19K protein does not alter mouse MHC class I-restricted responses to vaccinia virus

The adenovirus E3/19K glycoprotein forms a tight complex with most human and certain mouse MHC class I allomorphs, retaining them in the endoplasmic reticulum by virtue of its cytosolic carboxyl terminal amino acids. This prevents the presentation of viral antigens at the cell surface to class I-restricted cytotoxic T lymphocytes (CTL). In adenovirus infection of cotton rats, E3/19K appears to act as an anti-inflammatory and/or immunosuppressive factor. Further studies of the role of E3/19K in adenovirus pathogenesis have been hampered by the lack of sufficient knowledge concerning the immune system of the cotton rat and by the poor correlation between adenovirus infection in mice and humans. We therefore addressed the function of this adenovirus glycoprotein in virus pathogenesis by infecting B10.HTG (H-2KdDb) mice with a vaccinia virus (VV) recombinant encoding E3/19K. The Kd and Db allomorphs normally present VV antigens to CTL and have high affinity for E3/19K. Infected mice were examined for the kinetics of virus replication in various tissues and the generation of natural killer (NK) cell and CTL responses. It was found that expression of E3/19K by vaccinia virus had no detectable effect on CTL responses, NK responses, or viral replication. These findings suggest that immune modulating proteins evolve to exploit unique circumstances of the host immune response to a given virus.

Association of human class I MHC alleles with the adenovirus E3/19K protein

A panel of HLA-A and -B locus products was analyzed for their ability to associate with the adenovirus E3/19K (E19) protein in a co-immunoprecipitation assay. Three general categories of binding were identified. HLA-A2.1 and -B7 bind very well to E19. Compared with A2.1, 6- to 30-fold less E19 was associated with HLA-A3, -A1, and -Aw69; 50- to 150-fold less E19 was associated with HLA-Aw68, -B27, and -Bw58. Digestion with endoglycosidase H indicated that all levels of association resulted in inhibition of intracellular transport and processing, however, a fraction of Aw68, B27, and Bw58 escaped from intracellular retention. In contrast to the human class I molecules analyzed, transport of the murine H-2Dd molecule was not inhibited in the presence of E19. Hybrid class I molecules, in which exons encoding domains of A2.1 and H-2Dd had been exchanged, were used to define the regions of A2.1 required for E19 association. The alpha 1 and alpha 2 domains of A2.1 contain the minimum residues necessary for both stable association with E19 and subsequent inhibition of transport. A hybrid construct containing only the alpha 2 domain of A2.1 associated weakly with E19, but its post-translational processing was completely inhibited. In contrast, although a construct containing only the alpha 1 domain of A2.1 also associated weakly with E19, its intracellular transport was slowed rather than completely inhibited. Taken together, these results indicate that residues in both the alpha 1 and alpha 2 domains of A2.1 and Dd can influence stable binding of E19, with the phenotypic changes dominated by the origin of the alpha 2 domain.

Association of human class I MHC alleles with the adenovirus E3/19K protein

A panel of HLA-A and -B locus products was analyzed for their ability to associate with the adenovirus E3/19K (E19) protein in a co-immunoprecipitation assay. Three general categories of binding were identified. HLA-A2.1 and -B7 bind very well to E19. Compared with A2.1, 6- to 30-fold less E19 was associated with HLA-A3, -A1, and -Aw69; 50- to 150-fold less E19 was associated with HLA-Aw68, -B27, and -Bw58. Digestion with endoglycosidase H indicated that all levels of association resulted in inhibition of intracellular transport and processing, however, a fraction of Aw68, B27, and Bw58 escaped from intracellular retention. In contrast to the human class I molecules analyzed, transport of the murine H-2Dd molecule was not inhibited in the presence of E19. Hybrid class I molecules, in which exons encoding domains of A2.1 and H-2Dd had been exchanged, were used to define the regions of A2.1 required for E19 association. The alpha 1 and alpha 2 domains of A2.1 contain the minimum residues necessary for both stable association with E19 and subsequent inhibition of transport. A hybrid construct containing only the alpha 2 domain of A2.1 associated weakly with E19, but its post-translational processing was completely inhibited. In contrast, although a construct containing only the alpha 1 domain of A2.1 also associated weakly with E19, its intracellular transport was slowed rather than completely inhibited. Taken together, these results indicate that residues in both the alpha 1 and alpha 2 domains of A2.1 and Dd can influence stable binding of E19, with the phenotypic changes dominated by the origin of the alpha 2 domain.

TAP (transporter associated with antigen processing)-independent presentation of endogenously synthesized peptides is enhanced by endoplasmic reticulum insertion sequences located at the amino- but not carboxyl-terminus of the peptide

Under most circumstances, cell surface MHC class I molecules display peptides derived from a cytosolic pool of proteins. The efficient presentation of such peptides requires the functioning of two MHC gene products [TAP1 and TAP2 (transporter-associated with Ag processing 1 and 2)] that form a complex that facilitates transmembrane movement of peptides from the cytosol to the endoplasmic reticulum, the site of peptide association with class I molecules. It has been previously shown that peptides can be presented in a TAP-independent manner in association with HLA A2.1 or H-2 Kd if they are expressed COOH-terminal to an endoplasmic reticulum insertion/signal sequence derived from the adenovirus E3/19K glycoprotein (Anderson et al., 1991. J. Exp. Med. 174: 489; Eisenlohr et al., 1992. Cell 71: 963). We show that: 1) the E3/19K signal sequence greatly enhances the presentation of each of four additional peptides tested in association with H-2 Kb or Kk, 2) the E3/19K signal sequence can be substituted by a signal sequence derived from beta-IFN, and 3) the E3/19K signal sequence does not function when located at the COOH terminus of antigenic peptides. These findings indicate that first, many peptides require TAP for efficient presentation to T cells, second, expression of peptides COOH-terminal to signal sequences is a generally applicable method of bypassing the TAP-dependence of peptide presentation and third, the leader sequence does not act to bypass TAP simply by increasing the hydrophobic nature of peptides.

TAP (transporter associated with antigen processing)-independent presentation of endogenously synthesized peptides is enhanced by endoplasmic reticulum insertion sequences located at the amino- but not carboxyl-terminus of the peptide

Under most circumstances, cell surface MHC class I molecules display peptides derived from a cytosolic pool of proteins. The efficient presentation of such peptides requires the functioning of two MHC gene products [TAP1 and TAP2 (transporter-associated with Ag processing 1 and 2)] that form a complex that facilitates transmembrane movement of peptides from the cytosol to the endoplasmic reticulum, the site of peptide association with class I molecules. It has been previously shown that peptides can be presented in a TAP-independent manner in association with HLA A2.1 or H-2 Kd if they are expressed COOH-terminal to an endoplasmic reticulum insertion/signal sequence derived from the adenovirus E3/19K glycoprotein (Anderson et al., 1991. J. Exp. Med. 174: 489; Eisenlohr et al., 1992. Cell 71: 963). We show that: 1) the E3/19K signal sequence greatly enhances the presentation of each of four additional peptides tested in association with H-2 Kb or Kk, 2) the E3/19K signal sequence can be substituted by a signal sequence derived from beta-IFN, and 3) the E3/19K signal sequence does not function when located at the COOH terminus of antigenic peptides. These findings indicate that first, many peptides require TAP for efficient presentation to T cells, second, expression of peptides COOH-terminal to signal sequences is a generally applicable method of bypassing the TAP-dependence of peptide presentation and third, the leader sequence does not act to bypass TAP simply by increasing the hydrophobic nature of peptides.

Molecular analysis of rabies-related viruses from Ethiopia

From brain samples collected from domestic animals in Ethiopia, two rabies-related viruses were isolated. According to their reactivity pattern with anti-nucleocapsid monoclonal antibodies, they were characterized as Lagos bat virus (isolate Eth-58) and Mokola virus (isolate Eth-16). This classification was confirmed by neutralization experiments with Mokola and Lagos bat specific antisera. Two potent anti-rabies vaccines were unable to protect mice against the two rabies-related viruses. In order to investigate molecular relationships to classical rabies virus, cDNA cloning and sequencing was performed. The RNA genome of both viruses comprises 12 kilobases (kb) and has an organization similar to that of rabies virus with the gene order 3'-N-P-M-G-L-5'. Using virus-specific cDNA as probes in heterologous hybridization experiments, the RNAs of other members of lyssavirus serotypes 2 and 3 were detected. From hybridization experiments and sequence analysis of the 3' terminal 5,5 kb of the genomes, Eth-16 and Eth-58 viruses were shown to be equally genetically distant from rabies virus with 60% nucleotide identity; Eth-16 and Eth-58 had 68% homology.

Nuclear localization of a double-stranded RNA-binding protein encoded by the vaccinia virus E3L gene

We produced a B cell hybridoma (TW2.3) from vaccinia virus-infected mice that secreted a monoclonal antibody (MAb) reactive with a 25-kDA early viral protein that was localized by laser scanning confocal microscopy to the nucleus and cytoplasmic viral factory regions of infected cells. By cell-free translation of mRNA selected by hybridization to a complete library of vaccinia virus DNA fragments, the immunoreactive polypeptide was mapped to open reading frame E3L. The RNA start site of an early promoter was located 26 nucleotides upstream of the first methionine codon of E3L. Evidence was obtained that translation initiation occurs in vivo and in vitro at both the first and second methionine codons to produce major and minor polypeptides of 25 and 19 kDa, respectively. Both polypeptides bound double-stranded RNA, confirming the recent report of H.-W. Chang, J. C. Watson, and B. L. Jacobs (Proc. Natl. Acad. Sci. USA 89, 4825-4829, 1992). Other vaccinia virus proteins were not required for the nuclear localization of the E3L protein, since MAb TW2.3 bound to the nuclei of uninfected cells that were transfected with the E3L gene under the control of the SV40 early promoter. We also demonstrated that the E3L protein can bind to nuclei of aldehyde fixed and detergent permeabilized uninfected cells. This binding was abrogated by treatment of the cells with RNase but not DNase. The nuclear and cytoplasmic locations of the double-stranded RNA binding protein are consistent with multiple functions in the vaccinia virus infectious cycle.