Abstract 3251: Assessment of NK cell-mediated killing and phenotypic analysis using advanced flow cytometry and an optimized multiplexed assay

In this study, a novel multiplexed assay was developed that simultaneously measures NK cell phenotype and function in relation to tumor target killing. Natural Killer (NK) cells are an essential part of the innate immune system, interface with the adaptive immune system, and play a critical role in tumor immune surveillance and anti-tumor responses. Although chimeric antigen receptor (CAR)-modified T cells have proven to be highly effective as an anti-cancer therapeutic, there are potential problems associated with their use, particularly the risk of inducing graft-versus-host disease (GVHD) resulting in aberrant cytokine release. In contrast to T cells, NK cells are potent cytotoxic effector cells that do not require MHC restriction and have a low risk of inducing GVHD. Recent advances in the development of CAR-modified NK cells have shown great promise for clinical utilization in cancer immunotherapy with capability for both direct tumor killing as well as for use in combination therapy with monoclonal antibodies to boost NK cell antibody-dependent cell-mediated cytotoxicity (ADCC). A critical process in the development of new NK cell-mediated therapeutics is the ability to expediently assay, screen, and analyze data for NK cell activation and tumor killing. To address this need, a novel multiplexed assay was developed that measures tumor target cell killing, target-dependent expression of activation markers (CD69 and CD25), and the quantitation of secreted granzyme B, IFNγ, and TNFα in a single well of a microtiter plate. To validate the assay, a direct NK cell-tumor cell killing model was used. Purified human NK cells were mixed with target cells at different ratios. Tumor cell killing, NK cell activation status, and quantification of secreted proteins were measured at 4 and 24 hours after co-culture. Assay data acquisition was performed on Intellicyt iQue3® platform for advanced flow cytometry. Data analysis and visualization was performed using the integrated ForeCyt® software package. Tumor cell killing along with granzyme B release, was evident by 4 hours following co-culture, and both were increased with the increase in effector to target ratio (E:T). Killing was further enhanced when NK cells were stimulated with IL-2 and IL-15. As expected, an increase in CD69 and CD25 expression was also observed following cytokine stimulation with further increase upon co-culture of NK cells with tumor cell targets, along with increased levels of secreted IFNγ and TNFα. Further validation of the assay using an ADCC model was also performed. These data show that a miniaturized, multiplexed NK cell killing assay, combined with high throughput flow cytometry, is a powerful tool to rapidly screen CAR-NK cell effector functions and other NK cell based therapeutics.

Citation Format: Julie Lovchik, Sarita Chauhan, John O'Rourke. Assessment of NK cell-mediated killing and phenotypic analysis using advanced flow cytometry and an optimized multiplexed assay [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3251.

The role of PKCθ in Francisella tularensis infection in mice (164.4)

Francisella tularensis is a facultative intracellular bacteria that causes tularemia in animals and humans. F. tularensis is highly virulent and can be lethal. T cells play a critical role in Francisella immunity. It has been shown that mice succumb to sublethal infections when all T cells are depleted; however individual subsets including CD4, CD8 and an unusual CD4-CD8-NK1.1- population can be protective. While T cells control infection by producing IFNγ and TNFα, other less well-characterized mechanisms also play a role. PKCθ is a protein kinase involved in T cell activation; PKCθ is important in IFNγ production and PKCθ-/- mice are protected against both TH1 and TH2 mediated diseases. To investigate the role of PKCθ in F. tularensis infection, we infected wild-type C57Bl/6 (WT) mice and B6.PKCθ-/- mice with a lethal dose of LVS (live vaccine strain) which is commonly used to study F. tularensis infection. While WT mice died within 2 weeks of infection, surprisingly, over 50% of the PKCθ-/- mice survived past 3 weeks. We found that infected PKCθ-/- mice had more CD4-CD8- T cells in liver and lung than WT mice. In contrast, PKCθ-/- mice had fewer CD4+ T cells in lymph nodes, spleen, liver, and lung. We found no difference in numbers of activated T cells in liver and lung of infected WT and PKCθ-/- mice. These results show that PKCθ may be important in the expansion of CD4+ and CD4-CD8- T cell subtypes and this shift in the absence of PKCθ may protect against LVS infection.

Pre- and postexposure protection against virulent anthrax infection in mice by humanized monoclonal antibodies to Bacillus anthracis capsule

One of the two essential virulence factors of Bacillus anthracis is the poly-γ-D-glutamic acid (γDPGA) capsule. Five γDPGA-specific antibody antigen-binding fragments (Fabs) were generated from immunized chimpanzees. The two selected for further study, Fabs 11D and 4C, were both converted into full-length IgG1 and IgG3 mAbs having human IgG1 or IgG3 constant regions. These two mAbs had similar binding affinities, in vitro opsonophagocytic activities, and in vivo efficacies, with the IgG1 and IgG3 subclasses reacting similarly. The mAbs bound to γDPGA specifically with estimated binding affinities (K(d)) of 35-70 nM and effective affinities (effective K(d)) of 0.1-0.3 nM. The LD(50) in an opsonophagocytic bactericidal assay was ≈10 ng/mL of 11D or 4C. A single 30-μg dose of either mAb given to BALB/c mice 18 h before challenge conferred about 50% protection against a lethal intratracheal spore challenge by the virulent B. anthracis Ames strain. More importantly, either mAb given 8 h or 20 h after challenge provided significant protection against lethal infection. Thus, these anti-γDPGA mAbs should be useful, alone or in combination with antitoxin mAbs, for achieving a safe and efficacious postexposure therapy for anthrax.

The pathogenesis of acute pulmonary viral and bacterial infections: investigations in animal models

Acute viral and bacterial infections in the lower respiratory tract are major causes of morbidity and mortality worldwide. The proper study of pulmonary infections requires interdisciplinary collaboration among physicians and biomedical scientists to develop rational hypotheses based on clinical studies and to test these hypotheses in relevant animal models. Animal models for common lung infections are essential to understand pathogenic mechanisms and to clarify general mechanisms for host protection in pulmonary infections, as well as to develop vaccines and therapeutics. Animal models for uncommon pulmonary infections, such as those that can be caused by category A biothreat agents, are also very important because the infrequency of these infections in humans limits in-depth clinical studies. This review summarizes our understanding of innate and adaptive immune mechanisms in the lower respiratory tract and discusses how animal models for selected pulmonary pathogens can contribute to our understanding of the pathogenesis of lung infections and to the search for new vaccines and therapies.

Novel Semisynthetic Derivative of Antibiotic Eremomycin Active against Drug-Resistant Gram-Positive Pathogens Including Bacillus anthracis

Five adamantyl-containing carboxamides of eremomycin or vancomycin were synthesized and their antibacterial activities against some Gram-positive clinical isolates were investigated in vitro and in vivo. The adamantyl-2 amide of glycopeptide antibiotic eremomycin (1a in Chart 1, AN0900) was the most active compound and showed high activity against several Gram-positive pathogens: vancomycin-susceptible staphylococci and enterococci, glycopeptide-intermediate-resistant Staphylococcus aureus, and glycopeptide-resistant enterococci. Compound 1a was equally active in vitro against both Ciprofloxacin-susceptible and -resistant Bacillus anthracis strains (MICs 0.25-0.5 microg/mL). It was distinguished by having a 2.8 h half-life (t1/2) in mice and a volume of distribution of 2.18 L/kg. Compound 1a was active against Staphylococcus aureus in mice (iv) and provided complete protection against a lethal intravenous challenge with vegetative B. anthracis bacilli and also in a murine pulmonary anthrax model in which mice were challenged with Bacillus anthracis spores.

Toxin-deficient mutants of Bacillus anthracis are lethal in a murine model for pulmonary anthrax

Bacillus anthracis, the etiologic agent of anthrax, produces at least three primary virulence factors: lethal toxin, edema toxin, and a capsule. The capsule is absolutely required for dissemination and lethality in a murine model of inhalation anthrax, yet the roles for the toxins during infection are ill-defined. We show in a murine model that when spores of specific toxin-null mutants are introduced into the lung, dissemination and lethality are comparable to those of the parent strain. Mutants lacking one or more of the structural genes for the toxin proteins, i.e., protective antigen, lethal factor, and edema factor, disseminated from the lung to the spleen at rates similar to that of the virulent parental strain. The 50% lethal dose (LD50) and mean time to death (MTD) of the mutants did not differ significantly from those of the parent. The LD50s or MTDs were also unaffected relative to those of the parent strain when mice were inoculated intravenously with vegetative cells. Nonetheless, histopathological examination of tissues revealed subtle but distinct differences in infections by the parent compared to some toxin mutants, suggesting that the host response is affected by toxin proteins synthesized during infection.

MHC class I expression regulates susceptibility to spontaneous autoimmune disease in (NZBxNZW)F1 mice

(NZBxNZW)F1 mice spontaneously develop with age an autoimmune disease that resembles the human disease, systemic lupus erythematosus (SLE). Previous studies have demonstrated that susceptibility to experimentally induced SLE depended on the expression of MHC class I molecules: mice deficient in beta2-microglobulin did not express cell surface class I and were resistant to the induction of experimental SLE. Furthermore, the spontaneous SLE-like disease of (NZBxNZW)F1 mice was ameliorated by treatment with an agent that reduces MHC class I expression, methimazole (MMI). In the present study, the role of MHC class I has been examined in (NZBxNZW)F1 mice deficient in beta2-microglobulin expression. Homozygous (NZBxNZW)F1 beta2m-/- mice do not express class I or develop CD8+ T cells. Surprisingly, they show an increased susceptibility to disease. In sharp contrast, heterozygous (NZBxNZW)F1 beta2m+/- express class I, albeit at reduced levels, develop normal levels of CD8+ T cells and are less susceptible to autoimmune disease, relative to their wild-type litter mates. Taken together, these findings suggest that class I expression regulates the development of disease, both positively and negatively. We speculate that MHC class I expression itself confers susceptibility to disease through presentation of self-peptides, while also selecting for a CD8+ suppressor T cell population that mitigates disease.

Murine model of pulmonary anthrax: kinetics of dissemination, histopathology, and mouse strain susceptibility

Bioweapons are most often designed for delivery to the lung, although this route is not the usual portal of entry for many of the pathogens in the natural environment. Vaccines and therapeutics that are efficacious for natural routes of infection may not be effective against the pulmonary route. Pulmonary models are needed to investigate the importance of specific bacterial genes in virulence, to identify components of the host immune system that are important in providing innate and acquired protection, and for testing diagnostic and therapeutic strategies. This report describes the characteristics of host and Bacillus anthracis interactions in a murine pulmonary-infection model. The infective dose varied depending on the route and method of inoculation. The germination process in the lung began within 1 h of inoculation into the lung, although growth within the lung was limited. B. anthracis was found in the lung-associated lymph nodes approximately 5 h after infection. Minimal pneumonitis was associated with the lung infection, but significant systemic pathology was noted after dissemination. Infected mice typically succumbed to infection approximately 3 to 4 days after inoculation. The 50% lethal doses differed among inbred strains of mice, but within a given mouse strain, neither the age nor the sex of the mice influenced susceptibility to B. anthracis.

Active surveillance for respiratory virus infections in adults who have undergone bone marrow and peripheral blood stem cell transplantation

Community-acquired respiratory virus (RV) infections are an important cause of disease in immunocompromised adults with cancer. To investigate the viral etiology, incidence, clinical presentation, and outcome of RV infections in an outpatient cohort of adult bone marrow or peripheral blood stem cell transplant (SCT) recipients, we monitored 62 outpatient volunteers from January 1 to April 30, 2001. A nasopharyngeal aspirate was collected from subjects when they reported new respiratory symptoms and tested for RV (influenza A, influenza B, human parainfluenza 1-3, adenovirus, and respiratory syncytial virus) by culture and reverse transcription polymerase chain reaction (RT-PCR) assay. Of 62 subjects enrolled, 27% had received allogeneic SCT and 45% were within 1 year of their transplant. In all, 35 participants (56%) reported 37 episodes of respiratory symptoms. Of the 37 specimens tested, five (14%) were positive for RV by culture and 20 (54%) were positive by RT-PCR. Only six patients with RV infections developed lower respiratory tract illnesses; these patients had received either autologous or allogeneic transplants and developed illnesses between 41 and 2666 days post transplant. Although RV infections were common in SCT outpatients during the RV season, most participants had upper respiratory tract infections, which resolved without the need for hospitalization.

Multicenter evaluation of the BDProbeTec ET System for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in urine specimens, female endocervical swabs, and male urethral swabs

The performance of the Becton Dickinson BDProbe Tec ET System Chlamydia trachomatis and Neisseria gonorrhoeae Amplified DNA Assays (BD Biosciences, Sparks, Md.) was evaluated in a multicenter study. Specimens were collected from 2,109 men and women, with or without symptoms, attending sexually transmitted disease, family planning, and obstetrics and gynecology clinics. Both swab and urine samples were collected, and the results obtained from 4,131 specimens were compared to those from culture and the LCx nucleic acid amplification test (Abbott Industries, Abbott Park, Ill.). PCR and cytospin of the culture transport medium with chlamydia direct fluorescent antibody staining were used to adjudicate chlamydia culture-negative results. Sensitivity and specificity were calculated both with and without use of the amplification control (AC), with little apparent difference in the results. Without the AC result, sensitivity for C. trachomatis and N. gonorrhoeae were 92.8 and 96.6%, respectively, for cervical swabs and 80.5 and 84.9% for urine from women. C. trachomatis and N. gonorrhoeae sensitivities were 92.5 and 98.5%, respectively, for male urethral swabs and 93.1 and 97.9% for urine from men. This amplified DNA system for simultaneous detection of chlamydial and gonococcal infections demonstrated superior sensitivity compared to chlamydia culture and has performance characteristics comparable to those of other commercially available nucleic acid-based assays for these organisms.

Mismatch cleavage detects pathogenic microorganisms

When a DNA probe hybridizes a DNA target and generates a G/A mismatch in the probe-target DNA heteroduplex, the mismatch enzyme, mutY, will cut the A base at the site of the mismatch. This specific cleavage at the mismatched A on the known probe will reveal the complementary DNA sequences of the targets. This study shows mismatch cleavage assays identify the complementary sequence of cryptic plasmid target in the extract of chlamydia infected cells in culture. In addition, the specific cleavage at a single base permits differentiation of two sequences with one base difference. This was shown in differentiating the subtypes of human immunodeficiency virus (HIV) type 1. The addition of amines in the assays increases the sensitivity by freeing the target for recycling. The combined assay system of high sensitivity and demonstrated specificity allows further evaluation for direct identification of pathogenic microorganisms in patient samples.

Ureaplasma urealyticum respiratory tract colonization is associated with an increase in interleukin 1-beta and tumor necrosis factor alpha relative to interleukin 6 in tracheal aspirates of preterm infants

OBJECTIVE

To determine whether Ureaplasma urealyticum respiratory tract colonization in very low birth weight infants during the first week of life is associated with changes in tracheal aspirate concentrations of the cytokines interleukin 1-beta (IL-1-beta), tumor necrosis factor alpha (TNF-alpha) and IL-6.

METHODS

Infants with birth weights < or =1250 g were prospectively enrolled. Samples were obtained from the endotracheal tube or nasopharynx on Day 1 and again between Days 7 and 10 for U. urealyticum culture. The concentrations of IL-1-beta, TNF-alpha and IL-6 were measured in tracheal aspirate samples by enzyme-linked immunosorbent assay.

RESULTS

There were 18 positive cultures for U. urealyticum from 15 of 96 infants (15.6%). IL-1-beta in tracheal aspirates expressed as concentration per volume or as a ratio of IL-1-beta to IL-6 were 7- and 14.9-fold higher, respectively, in Ureaplasma-positive infants than in Ureaplasma-negative infants (P < 0.05). The TNF-alpha/IL-6 ratio was 18.9 and 15.5 times higher in the Ureaplasma-positive aspirates than in the Ure aplasma-negative aspirates on Day 1 and Days 7 to 10 (P < 0.05). Concentrations of IL-1-beta and TNF-alpha were significantly correlated on Day 1 and Days 7 to 10. Although there was no clinical association demonstrated between U. urealyticum colonization and the development of bronchopulmonary dysplasia (BPD) in this study, infants who developed BPD had significantly higher IL-1-beta concentrations and ratios of IL-1-beta to IL-6 in Day 1 aspirates than infants who did not develop BPD. Conclusions. Isolation of U. urealyticum from the respiratory tract is associated with increased IL-1-beta concentrations and IL-1-beta-IL-6 ratios on Day 1 and increased TNF-alpha-IL-6 ratios on Days 1 and 7 to 10 in tracheal aspirates of colonized infants. Infants who developed BPD had higher IL-1-beta concentrations and IL-1-beta-IL-6 ratios, suggesting that these may be early markers of lung inflammation.

Polymerase chain reaction-based detection of B-cell clonality in the fine needle aspiration biopsy of a thyroid mucosa-associated lymphoid tissue (MALT) lymphoma

Although it is possible to diagnose primary high-grade thyroid lymphoma from a fine needle aspiration (FNA) biopsy, the distinction of low-grade B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) from lymphocytic thyroiditis is sometimes problematic. Definitive diagnosis of lymphoma on cytologic specimens may be facilitated by the documentation of a clonal lymphoid proliferation within the specimen by flow cytometric immunophenotyping or immunocytochemistry. Recently, molecular techniques have also been developed to detect clonal lymphoid proliferation based on immunoglobulin (Ig) or T-cell receptor gene rearrangement. We have used a polymerase chain reaction (PCR)-based assay for Ig heavy chain gene arrangement to identify a clonal population of lymphocytes within the thyroid FNA specimen from a low-grade thyroid MALT lymphoma. Using this assay, we identified no distinct clonal population in five cytologic specimens of lymphocytic thyroiditis. Therefore, this PCR-based clonality assay represents a potentially useful adjunct to the cytologic diagnosis of thyroid lymphoma.

Expression of lung inducible nitric oxide synthase protein does not correlate with nitric oxide production in vivo in a pulmonary immune response against Cryptococcus neoformans

Mice infected intratracheally with Cryptococcus neoformans (Cne) require CD4 and CD8 T cells, IFN-gamma, and M phi production of nitric oxide (NO) for effective resolution of the pulmonary infection. Differences exist among strains of mice in clearing the infection. C.B-17 mice reduced Cne lung burden at a significantly greater rate than C57BL/6 (B6) mice and resistance correlated with greater IFN-gamma production by C.B-17 lung-associated lymph node cells. We examined whether the differences observed in the ability of B6 vs C.B-17 mice to clear Cne was due to 1) numbers of inflammatory cells recruited to the lung, 2) the activation state of the recruited cells as measured by expression of inducible nitric oxide synthase (iNOS), and/or 3) the in vivo production of NO as measured by quantitating urine nitrates. The level of iNOS protein was identical in lungs from both strains of mice during Cne infection as determined by Western blot analysis of whole lung homogenates and immunocytochemistry of isolated lung macrophages. Surprisingly, in vivo studies of iNOS activity indicated that NO production in B6 mice was significantly less than that in C.B-17 mice. While single cell suspensions from lungs of either mouse strain produced identical amounts of NO, NO production by lung explants paralleled in vivo urinary nitrate excretion, suggesting that the maintenance of pulmonary architecture and cell-cell interaction was necessary for suppression of iNOS activity in B6 mice. These data strongly implicate the existence of mechanisms that regulate NO production at the level of enzyme activity during infections and have important implications for analyzing the role of iNOS during an immune response in in vivo models.

Expression of lung inducible nitric oxide synthase protein does not correlate with nitric oxide production in vivo in a pulmonary immune response against Cryptococcus neoformans

Mice infected intratracheally with Cryptococcus neoformans (Cne) require CD4 and CD8 T cells, IFN-gamma, and M phi production of nitric oxide (NO) for effective resolution of the pulmonary infection. Differences exist among strains of mice in clearing the infection. C.B-17 mice reduced Cne lung burden at a significantly greater rate than C57BL/6 (B6) mice and resistance correlated with greater IFN-gamma production by C.B-17 lung-associated lymph node cells. We examined whether the differences observed in the ability of B6 vs C.B-17 mice to clear Cne was due to 1) numbers of inflammatory cells recruited to the lung, 2) the activation state of the recruited cells as measured by expression of inducible nitric oxide synthase (iNOS), and/or 3) the in vivo production of NO as measured by quantitating urine nitrates. The level of iNOS protein was identical in lungs from both strains of mice during Cne infection as determined by Western blot analysis of whole lung homogenates and immunocytochemistry of isolated lung macrophages. Surprisingly, in vivo studies of iNOS activity indicated that NO production in B6 mice was significantly less than that in C.B-17 mice. While single cell suspensions from lungs of either mouse strain produced identical amounts of NO, NO production by lung explants paralleled in vivo urinary nitrate excretion, suggesting that the maintenance of pulmonary architecture and cell-cell interaction was necessary for suppression of iNOS activity in B6 mice. These data strongly implicate the existence of mechanisms that regulate NO production at the level of enzyme activity during infections and have important implications for analyzing the role of iNOS during an immune response in in vivo models.

Chronic cytomegalovirus infection, immunodeficiency, and monoclonal gammopathy-antigen-driven malignancy?

An infant with severe combined immunodeficiency had normal numbers of lymphocytes which bore E rosette and surface Ig markers in an appropriate distribution. However, only minimal responsivity to in vitro stimulation by mitogens and allogenic cells, and none to antigens could be elicited; functional antibody responses were also nil, except to cytomegalovirus. Intrauterine-acquired cytomegalovirus may have caused his immune dysfunction, although the possibility of a postnatal infection cannot be excluded. Therapy with transfer factor and thymus transplantation was unsucessful in restoring immunity and may have aggravated a pre-existing monoclonal gammopathy. It is possible that the monoclonal protein was derived from B-cells transplacentally received from the patients mother.