Costal Cartilage Lateral Crural Strut Graft for Correction of External Nasal Valve Dysfunction in Primary and Revision Rhinoplasty

OBJECTIVE

To evaluate and compare the costal cartilage lateral crural strut graft's (LCSG) ability to support a weak lateral crus in patients with external nasal valve dysfunction (EVD) undergoing primary versus revision functional rhinoplasty.

METHODS

This is a prospective cohort study of 26 patients (mean [SD]: 40.23 [6.75] years of age; 10 [38%] females) with clinically diagnosed EVD, who underwent primary versus revision functional rhinoplasty with the use of a costal cartilage LCSG (10 [38%] primary functional rhinoplasty patients and the 16 [62%] revision patients). Preoperative and 12-month postoperative subjective and objective functional measurements along with statistical analysis were performed.

RESULTS

While all baseline demographic and preoperative functional measurement scores were similar between the 2 groups, the primary cohort's preoperative scores were higher overall. Follow-up was a mean of 14.58 months. The primary group demonstrated a greater difference in score improvement postoperatively in all categories. All patients had significantly improved visual analog scale (VAS), Nasal Obstruction Symptom Evaluation Scale, 22-Item Sinonasal Outcome Test, and nasal peak inspiratory flow (NPIF) scores. When comparing the overall score outcome and surgical efficacy of the LCSG, both groups had near equal final score outcomes with the exception of VASL and NPIF.

CONCLUSION

The LCSG is a viable and versatile option in the management of EVD for both primary and revision rhinoplasty patients.

Association Between Bitter Taste Receptor Phenotype and Clinical Outcomes Among Patients With COVID-19

IMPORTANCE

Bitter taste receptors (T2Rs) have been implicated in sinonasal innate immunity, and genetic variation conferred by allelic variants in T2R genes is associated with variation in upper respiratory tract pathogen susceptibility, symptoms, and outcomes. Bitter taste receptor phenotype appears to be associated with the clinical course and symptom duration of SARS-CoV-2 infection.

OBJECTIVE

To evaluate the association between T2R phenotype and patient clinical course after infection with SARS-CoV-2.

DESIGN, SETTING, AND PARTICIPANTS

A prospective cohort study was performed from July 1 through September 30, 2020, at a tertiary outpatient clinical practice and inpatient hospital in the United States among 1935 participants (patients and health care workers) with occupational exposure to SARS-CoV-2.

EXPOSURE

Exposure to SARS-CoV-2.

MAIN OUTCOMES AND MEASURES

Participants underwent T2R38 phenotype taste testing to determine whether they were supertasters (those who experienced greater intensity of bitter tastes), tasters, or nontasters (those who experienced low intensity of bitter tastes or no bitter tastes) and underwent evaluation for lack of infection with SARS-CoV-2 via polymerase chain reaction (PCR) testing and IgM and IgG testing. A group of participants was randomly selected for genotype analysis to correlate phenotype. Participants were followed up until confirmation of infection with SARS-CoV-2 via PCR testing. Phenotype of T2R38 was retested after infection with SARS-CoV-2. The results were compared with clinical course.

RESULTS

A total of 1935 individuals (1101 women [56.9%]; mean [SD] age, 45.5 [13.9] years) participated in the study. Results of phenotype taste testing showed that 508 (26.3%) were supertasters, 917 (47.4%) were tasters, and 510 (26.4%) were nontasters. A total of 266 participants (13.7%) had positive PCR test results for SARS-CoV-2. Of these, 55 (20.7%) required hospitalization. Symptom duration among patients with positive results ranged from 0 to 48 days. Nontasters were significantly more likely than tasters and supertasters to test positive for SARS-CoV-2 (odds ratio, 10.1 [95% CI, 5.8-17.8]; P < .001), to be hospitalized once infected (odds ratio, 3.9 [1.5-10.2]; P = .006), and to be symptomatic for a longer duration (mean [SE] duration, 23.7 [0.5] days vs 13.5 [0.4] days vs 5.0 [0.6] days; P < .001). A total of 47 of 55 patients (85.5%) with COVID-19 who required inpatient admission were nontasters. Conversely, 15 of 266 patients (5.6%) with positive PCR test results were supertasters.

CONCLUSIONS AND RELEVANCE

This cohort study suggests that T2R38 receptor allelic variants were associated with participants' innate immune response toward SARS-CoV-2. The T2R phenotype was associated with patients' clinical course after SARS-CoV-2 infection. Nontasters were more likely to be infected with SARS-CoV-2 than the other 2 groups, suggesting enhanced innate immune protection against SARS-CoV-2.

A52 ANALYSIS AND CHARACTERIZATION OF THE EXCRETED/SECRETED PRODUCTS OF PARASITIC HELMINTHS AS IMMUNOMODULATORS OF INFLAMMATORY BOWEL DISEASE (IBD)

Background

Parasitic helminths Trichuris suis and Ascaris suum are known to modulate host immune responses. This is thought to be mediated by the secretome, or excreted factors released by these parasites. We are interested in the excretory/secretory products (ESP, TsESP and AsESP) and mechanisms responsible for modulating immune disfunciton in autoinflammatory diseases.

Aims

This research studies the mechanisms of immune modulation by parasitic helminths in the context of IBD. We aim to describe the cellular response in vitro, as well as the systemic response in vivo, to better characterize the scope of immune modulation in ESP treatment.

Methods

ESPs were collected from T. suis or A. suum-conditioned media and proteins and metabolites were isolated.

Bone marrow (BM) derived macrophages (BMDM) from C57BL6 mice, were treated with ESP fractions, stimulated with LPS, and secreted cytokines levels measured. Alternatively, undifferentiated BM was incubated with or without metabolites throughout the process of differentiation.

Using a DSS-colitis model, mice were given 3% DSS or water, then treated with ESP or PBS once daily by IP injection. Colon lengths and TNFα mRNA levels were measured and histological preparations were scored to assess pathology.

ESP with bioactivity were selected for further HPLC analysis. Fractions were collected and assayed for bioactivity.

Results

BMDM treated with T. suis or A. suum crude ESP decreased secretion of TNFα and increased IL-10. BMDM precursors incubated with A. suum metabolites during differentiation had fewer BMDM-like cells. Cytokine analysis showed decreased TNFα secretion. Experiments with Alamar suggested that metabolites remmodelled the BMDM metabolic pathways. These effects are being explored further.

We found that metabolites released by A. suum improved DSS-colitis. Specifically, mice with DSS-induced colitis given IP metabolites had reduced colon shortening compared to PBS controls, a lower histologic damage score, as well as lower levels TNFα mRNA expression in gut epithelial cells.

HPLC showed multiple peaks from crudes analyzed at 210 nm and 280 nm. HPLC fractions used to treat BMDM yielded varying secretion of TNFα. Bioactive fractions from HPLC coincide with the UV/Vis peaks, further suggesting they could be isolated and studied for immunomodulation.

Conclusions

These data suggested that ESP contains immunomodulators that may provide lead therapeutic compounds for patients with IBD. Helminth-derived components can immunologically polarize a response in vitro, as well as alter disease recovery in DSS colitis. HPLC fractionation and biological testing suggest that a bioactive molecule can be obtained. Further analysis must be done to determine structure using mass spectrometry and NMR analysis.

Funding Agencies

Natural Sciences and Engineering Research Council of Canada (NSERC) and Fonds de recherche nature et technologies Québec (FRQNT)

Variability of the Anterior Ethmoid Artery in Endoscopic Sinus Surgery

INTRODUCTION

The anterior ethmoidal artery (AEA) demonstrates anatomic variability relative to its descent from the anterior skull base. Our study's objective was to assess for correlation of AEA descent and laterality, in addition to correlation of AEA descent and the presence of supraorbital ethmoid cells (SOEC) and concha bullosae (CB).

METHOD

A retrospective study was performed at a tertiary rhinology center from January 2019 to January 2020. Noncontrast maxillofacial computed tomography scans were examined independently by 2 fellowship trained rhinologists. The vertical distance from both left and right AEAs to the ipsilateral skull base were compared and correlated with the presence of ipsilateral SOEC and CB.

RESULTS

Computed tomography scans from 50 subjects were included. Mean age was 50.68 years (40% females). The distance of AEA to the skull base was greater on the left when compared to the right (62% vs 48%) (P < .05). The left AEA had an average descent of 2.84 mm versus 1.78 mm on the right (P < .05). An SOEC was present in 56% of cases. Thirty-eight percent of subjects had both SOEC and AEA descent on the right, while 52% of subjects had both on the left. This reached a statistical significance on both sides (P < .05). Concha bullosa was present in 35% of cases, with both AEA descent and CB present in 16% on the right, and 32% on the left.

CONCLUSION

The AEA displays variability in vertical descent from the skull base, with greater variability on the left. These findings implore vigilance with evaluation of preoperative imaging and during sinus surgery, especially in the presence of SOEC and CB.

Rhinologic Procedures in the Era of COVID-19: Health-care Provider Protection Protocol

Introduction

SARS-CoV-2 has been identified as the pathogen causing the outbreak of Coronavirus Disease 2019 (COVID-19) that started in Wuhan, China, in December 2019. SARS-CoV-2 has human-to-human transmission ability and universally contagious to all populations. The main transmission patterns are respiratory droplets transmission and contact transmission. The purpose of this study is to propose a protocol that may be used as a guide to reduce the incidence of COVID-19 infections among otolaryngology care teams.

Methods

A prospective cohort study was conducted to show the efficacy of our protocol to prevent transmission to health-care providers from March 11, 2020 through April 14, 2020. The protocol consisted of a series of protective measures that we applied to all health-care providers, then testing of our providers for COVID-19 using reverse transcription polymerase chain reaction along with immunoglobulin M (IgM) and immunoglobulin G (IgG) testing at the end of the study period to ensure effectiveness.

Results

Our protocol resulted in zero transmissions to our health-care providers during the duration of the initial study. We were involved in greater than 150 sinonasal, skull base, open airway, and endoscopy procedures during this study. At the conclusion of the initial 5 weeks, we had no health-care providers test positive for SARS-CoV-2.

Conclusion

According to our proposed protocol, we were able to provide care for all patients in clinic, hospital, emergent, intensive, and surgical settings with no transmission of SARS-CoV-2 by symptomatology and post evaluation testing.

Impact of Draf III, Draf IIb, and Draf IIa frontal sinus surgery on nasal irrigation distribution

BACKGROUND

Delivery of topical pharmacotherapy to the paranasal sinuses remains integral to the management of chronic rhinosinusitis. The frontal sinus remains a difficult access site for irrigations, often limited by its position relative to the nostril and ethmoid sinus. In view of the previous demonstration of improved frontal sinus irrigation with Draf III vs Draf IIa, in this work we sought to evaluate topical access of Draf IIb relative to Draf IIa and Draf III modification of the frontal sinus outflow tract.

METHODS

Unfixed human cadaver heads were dissected using Draf IIa, Draf IIb, and Draf III frontal sinusotomies. Draf IIa, Draf IIb, and Draf III frontal sinusotomies were performed in progressive sequence on each cadaver head. Nasal irrigation fluid access to the frontal sinus was tested after each successive frontal sinus intervention. Irrigations were performed using Frankfort horizontal and vertex positioning. Blinded reviewers were then asked to evaluate nasal irrigation access based on an ordinal scale.

RESULTS

Eight cadaveric specimens (age, 78 ± 12.3 years; 62.5% female) were assessed. The greatest distribution scores were recorded by Draf III, then IIb, and then IIa (90.7% vs 81.3% vs 50.1%; p < 0.001). Similarly, the rate of lavage was greatest with Draf III (50% vs 12.5% vs 12.5%). Vertex positioning and increasing volume trended toward improved distribution but did not reach statistical significance.

CONCLUSION

Adequate delivery of topical therapy to the paranasal sinuses by nasal irrigation remains critical in the postoperative state. Although increasing the dimensions of the frontal recess improves nasal irrigation delivery, the Draf III procedure provides the optimal delivery of pharmacotherapy in those with frontal sinus disease.

Genetic control of susceptibility to infection with Plasmodium chabaudi chabaudi AS in inbred mouse strains

To identify genetic effects modulating blood stage replication of the malarial parasite, we phenotyped a group of 25 inbred mouse strains for susceptibility to Plasmodium chabaudi chabaudi AS infection (peak parasitemia, survival). A broad spectrum of responses was observed, with strains such as C57BL/6J being the most resistant (low parasitemia, 100% survival), and strains such as NZW/LacJ and C3HeB/FeJ being extremely susceptible (very high parasitemia and uniform lethality). A number of strains showed intermediate phenotypes and gender specific effects, suggestive of rich genetic diversity in response to malaria in inbred strains. An F2 progeny were generated from SM/J (susceptible) and C57BL/6J (resistant) parental strains, and was phenotyped for susceptibility to P. chabaudi chabaudi AS. A whole genome scan in these animals identified the Char1 locus (LOD=7.40) on chromosome 9 as a key regulator of parasite density and pointed to a conserved 0.4Mb haplotype at Char1 that segregates with susceptibility/resistance to infection. In addition, a second locus was detected in [SM/J x C57BL/6J] F2 mice on the X chromosome (LOD=4.26), which was given the temporary designation Char11. These studies identify a conserved role of Char1 in regulating response to malaria in inbred mouse strains, and provide a prioritized 0.4Mb interval for the search of positional candidates.

Caspase-12 deficiency enhances cytokine responses but does not protect against lethal Plasmodium yoelii 17XL infection

To investigate the effect of caspase-12 deficiency on IFN-γ- independent control of blood-stage malaria, we compared lethal Plasmodium yoelii 17XL infection in wild-type C57BL ⁄ 6J and caspase-12-/-mice. Infected caspase-12-/- mice exhibited higher parasitaemia than WT mice on days 8 and 9 post-inoculation, but all WT and caspase-12-/- mice succumbed by day 10. In addition, infected caspase-12-/-mice had significantly elevated levels of IFN-γ, TNF, IL-18,and IL-10 in sera compared to infected WT mice. At the terminal stage of disease, there were no differences in cytokine levels in the tissues of infected WT and caspase-12-/- mice. However, liver pathology was more severe in infected caspase-12-/- mice compared to infected WT mice. Together, these findings indicate that although caspase-12 deficiency results in enhanced pro-inflammatory and immunoregulatory cytokine levels in sera during P. yoelii 17XL infection, these responses are not essential for protection against lethal malaria infection.

Mapping of Char10, a novel malaria susceptibility locus on mouse chromosome 9

Resistance to blood-stage malaria in AcB55 and AcB61 is caused by a loss of function mutation in pyruvate kinase (Pklr(I90N)). Likewise, pyruvate kinase (PK) deficiency in humans is protective against Plasmodium replication in vitro. We identified a third AcB strain, AcB62 that also carries the Pklr(I90N) mutation. However, AcB62 mice were susceptible to P.chabaudi infection and showed high levels of parasite replication (54-62% peak parasitemia). AcB62 mice showed the hallmarks of PK deficiency-associated anemia similar to AcB55/61 with reticulocytosis, splenic red pulp expansion, tissue iron overload, and increased expression of iron metabolism proteins. This suggests that malaria susceptibility in AcB62 is not because of absence of PK deficiency-associated pathophysiology. To map novel genetic factors affecting malaria susceptibility in AcB62, we generated an informative F2 population using AcB62 (Pklr(I90N)) and CBA-Pk(slc) (Pklr(G338D)) as progenitors and identified a novel locus on chromosome 9 (Char10; LOD=7.24) that controls peak parasitemia. A weaker linkage to the Pklr region of chromosome 3 (LOD=3.7) was also detected, a finding that may reflect the segregation of the two defective Pklr alleles. AcB62 alleles at both loci are associated with higher peak parasitemia. These results identify Char10 as a novel locus modulating severity of malaria in the context of PK deficiency.

Modulation of malaria-induced immunopathology by concurrent gastrointestinal nematode infection in mice

We investigated malaria-associated pathology in mice co-infected with Heligmosomoides polygyrus (Hp) and Plasmodium chabaudi AS (Pc). Despite higher peak parasitemia, co-infected wild-type (WT) C57BL/6 mice displayed similar body weight losses, malarial anaemia, and tissue damage but less severe hypothermia and hypoglycaemia, and earlier reticulocytosis than Pc-infected WT mice. Co-infected STAT6(-/-) mice, deficient in nematode-induced Th2 responses, experienced similar peak parasitemias and generally suffered malaria-associated pathology to a similar degree as co-infected WT mice. These data indicate a complex relationship amongst helminths, malaria and host immune responses resulting in modulation of some but not all aspects of malaria-associated pathology.

Incremental expression of Tlr4 correlates with mouse resistance to Salmonella infection and fine regulation of relevant immune genes

The mouse response to Salmonella Typhimurium infection is partly controlled through detection of the bacterium lipopolysaccharide by the host pattern recognition receptor, Toll-like receptor 4 (Tlr4). Mice deficient in Tlr4 signaling are extremely susceptible to Salmonella infection with a 1,000-fold reduction in LD(50). In a previous study, we showed, using transgenic mice carrying one, three, six and >30 copies of Tlr4, that the level of expression of this gene influences the outcome of Salmonella infection, with a plateau effect starting at three copies. In the present study, we further investigate the impact of Tlr4 during Salmonella infection in mice expressing Tlr4 at slightly sub-normal, normal and slightly supra-normal levels by comparing host responses in mice carrying one, two and three copies of Tlr4 on the same genetic background. We describe in detail the in vivo host response to pathogenic Salmonella and show for the first time, in this narrow range of Tlr4 expression, an incremental protective effect against Salmonella due to improved control of bacterial growth in target organs and increased expression of important immune response genes in the spleen.

Antigen presentation and dendritic cell biology in malaria

Dendritic cells (DCs) are important both in amplifying the innate immune response and in initiating adaptive immunity and shaping the type of T helper (Th) response. Although the role of DCs in immune responses to many intracellular pathogens has been delineated and research is underway to identify the mechanisms involved, relatively little is known concerning the role of DCs in immunity to malaria. In this review, we provide an overview and summary of previous and current studies aimed to investigate the role of DCs as antigen presenting cells (APCs). In addition, the role of DCs in inducing innate and adaptive immunity to blood-stage malaria is discussed and, where information is available, the mechanisms involved are presented. Data from studies in humans infected with Plasmodium falciparum, the major human parasite responsible for the high morbidity and mortality associated with malaria throughout many regions of the developing world, as well as data from experimental mouse models are presented. Overall, the data from these studies are conflicting. The possible reasons for these differences, including the use of different parasite species and parasite strains in the mouse studies, are discussed. Nevertheless, together the data have important implications for development of an effective malaria vaccine since the selection of appropriate Plasmodium antigens and/or adjuvants, targeting innate immune responses involving DCs, may provide optimal protection against malaria. It is hoped that this review promotes more investigation among malariologists and immunologists alike on DCs and malaria.

Early interactions between blood-stage plasmodium parasites and the immune system

Accumulating evidence provides strong support for the importance of innate immunity in shaping the subsequent adaptive immune response to blood-stage Plasmodium parasites, the causative agents of malaria. Early interactions between blood-stage parasites and cells of the innate immune system, including dendritic cells, monocytes/macrophages, natural killer (NK) cells, NKT cells, and gamma6 T cells, are important in the timely control of parasite replication and in the subsequent elimination and resolution of the infection. The major role of innate immunity appears to be the production of immunoregulatory cytokines, such as interleukin (IL)-12 and interferon (IFN)-gamma, which are critical for the development of type 1 immune responses involving CD4+ Thl cells, B cells, and effector cells which mediate cell-mediated and antibody-dependent adaptive immune responses. In addition, it is likely that cells of the innate immune system, especially dendritic cells, serve as antigen-presenting cells. Here, we review recent data from rodent models of blood-stage malaria and from human studies, and outline the early interactions of infected red blood cells with the innate immune system. We compare and contrast the results derived from studies in infected laboratory mice and humans. These host species are sufficiently different with respect to the identity of the infecting Plasmodium species, the resulting pathologies, and immune responses, particularly where the innate immune response is concerned. The implications of these findings for the development of an effective and safe malaria vaccine are also discussed.

Phenotypic expression of pyruvate kinase deficiency and protection against malaria in a mouse model

The recombinant congenic mouse strains AcB55 and AcB61 are extremely resistant to malaria (Plasmodium chabaudi AS) despite the presence of susceptibility alleles at the known Char1/Char2 resistance loci. Resistance in AcB55 and AcB61 is controlled by a locus on chromosome 3 (Char4) shown to be allelic with or tightly linked to a loss-of-function mutation in pyruvate kinase (Pklr). AcB55 and AcB61 show important splenomegaly prior to infection caused by the expansion of the red pulp, and display histological signs of extramedullary erythropoiesis in the liver. Examination of splenic cell populations by flow cytometry demonstrates elevated numbers of TER119-positive erythroid precursor cells (>30% of total spleen cells), while RNA expression studies show elevated expression of erythrocyte-specific transcripts such as globin, transferrin receptor, and Nramp2/Slc11a2 in the spleen of both strains. Hematological profiling in both strains is consistent with the presence of anemia as evidenced by low total erythrocyte counts, decreased hemoglobin, as well as abnormally high numbers of circulating reticulocytes (15-20%). These results strongly suggest that the mutant Pklr allele (Pklr(269A)) of AcB55/61 strains causes hemolytic anemia compensated by constitutive erythropoiesis, which in turn protects the mice against P. chabaudi infection. The possible molecular basis of the Pklr protective effect is discussed and is under current investigation in these two strains.

Susceptibility to malaria as a complex trait: big pressure from a tiny creature

Malaria, which is a major infectious disease worldwide, is caused by the Plasmodium parasite, one of the longest-known parasites infecting humans. The malaria situation is complicated by the emergence of drug resistance and the lack of an effective vaccine. Genetic factors play a key role in disease susceptibility, progression and outcome. Interestingly, an increasing large number of polymorphisms associated with resistance and susceptibility in humans have been found in proteins from erythrocytes, the site of Plasmodium replication. Some of these deleterious alleles have been selected by direct genetic pressure from the parasite in endemic areas of malaria. A number of additional gene effects have been mapped both in humans and in mice using population studies and experimental models of malaria, respectively. These recent studies have started to reveal additional aspects of the complex host-parasite interactions.

Complex genetic control of susceptibility to malaria in mice

Malaria is a major infectious disease worldwide, with over 1 million deaths in African children every year. The molecular pathways of pathogenesis of the Plasmodium parasite and the host mechanisms of defense against this infection remain poorly understood. Epidemiological studies, together with linkage analyses in endemic areas have clearly pointed at a genetic component of innate susceptibility and severity of disease. In humans, this genetic trait is complex, and has been studied in a mouse experimental model over the past few years. Inbred strains of mice show different degrees of susceptibility to infection with Plasmodium chabaudi, and the genetic component of these inter-strain differences has been studied in standard informative backcross and F2 populations, as well as in recombinant inbred strains and more recently, in recombinant congenic strains. These studies have shown that genetic susceptibility to malaria is also complex in mice, and have led to the mapping of major susceptibility Char (Chabaudi resistance) loci, located on chromosomes 9 (Char1), 8 (Char2), 17 (Char3) and 3 (Char4).

Identification of a new malaria susceptibility locus (Char4) in recombinant congenic strains of mice

The genetic component of susceptibility to malaria is complex, both in humans and in the mouse model of infection. Two murine loci on chromosomes 8 (Pchr/Char2) and 9 (Char1) have previously been mapped in F(2) crosses, and play an important role in regulating blood parasitemia and survival to infection with Plasmodium chabaudi. These loci explain only part of the interstrain phenotypic variance, and their penetrance and expressivity vary in different inbred strains. Novel loci regulating response to P. chabaudi infection were investigated by using an alternative strategy based on a newly derived set of AcB/BcA recombinant congenic strains bred from malaria-susceptible A/J (A) and resistant C57BL/6J (B6). One of the AcB strains, AcB55, is shown to be highly resistant to infection despite 83% susceptible A genomic composition, including susceptibility alleles at Char1 and Pchr/Char2. Early onset of parasite clearance in AcB55 is associated with lower peak parasitemia and absence of mortality. Linkage analysis in an informative (AcB55 x A)F(2) population, using peak parasitemia as a quantitative trait, located a new B6-derived resistance locus on chromosome 3 (lod score = 6.57) that we designate Char4. A second, suggestive linkage on chromosome 10 (lod score = 2.53) shows additive effect with Char4 on peak parasitemia. Char4 maps to a small congenic B6 fragment in AcB55 that should facilitate the search for candidate genes. Our findings provide an entry point for parallel association studies in humans between the syntenic 4q21-4q25 region and susceptibility to disease in endemic areas of malaria.

Modulation of host responses to blood-stage malaria by interleukin-12: from therapy to adjuvant activity

This review focuses on the role of interleukin (IL)-12, a proinflammatory cytokine with pleiotropic effects as a potent immunoregulatory molecule and hematopoietic growth factor, in infection with Plasmodium parasites, the causative agents of malaria. IL-12 has been demonstrated to have profound effects on the immune response to blood-stage malaria, to induce protection, and to alleviate malarial anemia. In combination with an anti-malarial drug, IL-12 is effective in an established malaria infection. This cytokine also has potent immune effects as a malaria vaccine adjuvant. However, IL-12 can also mediate pathology during blood-stage malaria.

Granulocyte-macrophage colony-stimulating factor-deficient mice have impaired resistance to blood-stage malaria

The contribution of granulocyte-macrophage colony-stimulating factor (GM-CSF), a hematopoietic and immunoregulatory cytokine, to resistance to blood-stage malaria was investigated by infecting GM-CSF-deficient (knockout [KO]) mice with Plasmodium chabaudi AS. KO mice were more susceptible to infection than wild-type (WT) mice, as evidenced by higher peak parasitemia, recurrent recrudescent parasitemia, and high mortality. P. chabaudi AS-infected KO mice had impaired splenomegaly and lower leukocytosis but equivalent levels of anemia compared to infected WT mice. Both bone marrow and splenic erythropoiesis were normal in infected KO mice. However, granulocyte-macrophage colony formation was significantly decreased in these tissues of uninfected and infected KO mice, and the numbers of macrophages in the spleen and peritoneal cavity were significantly lower than in infected WT mice. Serum levels of gamma interferon (IFN-gamma) were found to be significantly higher in uninfected KO mice, and the level of this cytokine was not increased during infection. In contrast, IFN-gamma levels were significantly above normal levels in infected WT mice. During infection, tumor necrosis factor alpha (TNF-alpha) levels were significantly increased in KO mice and were significantly higher than TNF-alpha levels in infected WT mice. Our results indicate that GM-CSF contributes to resistance to P. chabaudi AS infection and that it is involved in the development of splenomegaly, leukocytosis, and granulocyte-macrophage hematopoiesis. GM-CSF may also regulate IFN-gamma and TNF-alpha production and activity in response to infection. The abnormal responses seen in infected KO mice may be due to the lack of GM-CSF during development, to the lack of GM-CSF in the infected mature mice, or to both.

Mouse models of chronic lung infection with Pseudomonas aeruginosa: models for the study of cystic fibrosis

The discovery of the CFTR gene in 1989 has lead to rapid progress in understanding the molecular basis of cystic fibrosis (CF) and the biological properties of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. However, more than 10 years later, recurrent lung infections with Pseudomonas aeruginosa, which lead to chronic lung disease and eventual respiratory failure, remain the major cause of morbidity and mortality among CF patients. A distinguishing feature of lung disease in CF is an exaggerated and persistent inflammatory response, characterized by the accumulation of excessive numbers of neutrophils and dysregulated cytokine production. The events leading to the establishment of lung infection with P. aeruginosa, especially the inflammatory and immunological events, and the relation between the CF defect and infection, remain largely undefined. Progress in this area has been hampered by the lack of a suitable animal model. An exciting achievement in the past few years has been the development of a number of variants of CFTR-deficient mice which exhibit defective cAMP-mediated Cl(-) conductance and have a range of clinical phenotypes from mild to severe. In parallel, a model of chronic P. aeruginosa lung infection has been established in genetically and immunologically well-defined inbred mouse strains which differ in susceptibility to this infection in the lung. BALB/c mice are resistant, while DBA/2 mice are extremely susceptible, with high mortality within 3 days of infection. C57BL/6 and A/J mice are relatively susceptible and experience low mortality. Furthermore, the bacterial load correlates with the magnitude and quality of the inflammatory response in the infected lungs of BALB/c and C57BL/6 mice. Although results of infection studies in CFTR-deficient mice have been variable, C57BL/6-Cftr(m1UNC)/Cftr(m1UNC) knockout mice compared to littermate control mice are highly susceptible to chronic P. aeruginosa infection in the lung. The availability of CFTR knockout mice and non-CF inbred mice differing in susceptibility to chronic P. aeruginosa infection offers useful tools for progress in understanding the genesis of chronic P. aeruginosa infection and the ensuing inflammation in the CF lung, as well as the relation between the CF defect and infection. Information generated from these studies will provide the rationale for the development of novel immunomodulatory measures capable of ameliorating or modulating the chronic inflammation associated with CF lung disease.

Identification and characterization of naturally occurring variants of the macrophage scavenger receptor (SR-A)

The scavenger receptor (SR) family comprises a group of cell surface proteins functionally defined by their ability to bind chemically modified lipoproteins. In macrophages, the class A Type I and Type II SRs (SR-AI/II) are thought to play a key role in adherence to and phagocytosis of infectious agents. Immunoprecipitation studies show that the rat anti-SR-AI/II monoclonal antibody 2F8 detects the mature, trimeric form of the receptor expressed in peritoneal macrophages from A/J, but not from C57Bl/6J (B6) mice. Subsequent sequencing of cDNA and genomic clones indicates that SR-AI and AII of A/J and B6 mice differ in sequence at nine positions, two in the cytoplasmic domain and seven in the extracellular spacer and alpha-helical coiled coil domains. These sequence polymorphisms are non-conservative and produce distinct receptor molecules that differ by four charged residues and alter recognition of the receptor by the monoclonal 2F8 antibody. The B6 SR-AI/II haplotype appears unique, since most inbred strains analyzed show the A/J-type haplotype. Interestingly, several of the B6 polymorphic variant residues are conserved in human and bovine receptors, suggesting a recent divergence of the A/J haplotype. Initial studies in CHO-derived cells expressing individual receptor isoforms indicate that the A/J and B6 receptors are stable and can mature into oligomers expressed in the membrane fractions of these cells. In these transfectants, no major functional differences were detected between receptors of the two haplotypes with respect to internalization and degradation of (125)I-labeled acetylated LDL. However, since SR-AI/II recognizes a large number of structurally unrelated anionic molecules, the possibility that different haplotypes may affect either binding and release of other ligands, or receptor recycling, cannot be excluded.

Characterization of T cell clones derived from lymph nodes and lungs of Pseudomonas aeruginosa-susceptible and resistant mice following immunization with heat-killed bacteria

Pseudomonas aeruginosa-resistant BALB/c and susceptible C57Bl/6 (B6) mice were immunized with heat-killed Pseudomonas either in the foot pad or via the trachea, and panels of Pseudomonas-specific T cell clones were developed from lymph nodes and lungs. All clones from either strain, whether of lymph node or lung origin, were CD3+CD4+CD8-TCRalphabeta+. The efficacy of cloning from lymph node cells was comparable between BALB/c and B6 mice. All lymph node BALB/c clones proliferated in response to Pseudomonas antigen in a dose-dependent manner, and this response was MHC class II-restricted. Vigorous proliferation by a considerable proportion of B6 T cell clones occurred in the absence of specific antigen. Lymph node clones from either strain could be categorized as either Th1 or Th0 on the basis of interferon-gamma (IFN-gamma)/IL-4 production. In either mouse strain the efficacy of cloning from lung tissue was substantially lower than from lymph nodes, but the efficacy of cloning from BALB/c compared with B6 lungs was higher. Four lung T cell clones from BALB/c and two from B6 mice were expanded for further analyses, and an interstrain difference was observed in cytokine production. Both B6 lung T cell clones were Th1-like and produced IFN-gamma but not IL-4 and IL-10, whereas four BALB/c lung T cell clones were Th2-like and produced IL-4 and IL-10 but not IFN-gamma. These observations suggest that differences in the CD4+ Th response in the lung may contribute to differences among inbred mouse strains in the level of resistance to bronchopulmonary Pseudomonas infection.

Central role of endogenous gamma interferon in protective immunity against blood-stage Plasmodium chabaudi AS infection

The role of endogenous gamma interferon (IFN-gamma) in protective immunity against blood-stage Plasmodium chabaudi AS malaria was studied using IFN-gamma gene knockout (GKO) and wild-type (WT) C57BL/6 mice. Following infection with 10(6) parasitized erythrocytes, GKO mice developed significantly higher parasitemia during acute infection than WT mice and had severe mortality. In infected GKO mice, production of interleukin 12 (IL-12) p70 and tumor necrosis factor alpha in vivo and IL-12 p70 in vitro by splenic macrophages was significantly reduced compared to that in WT mice and the enhanced nitric oxide (NO) production observed in infected WT mice was completely absent. WT and GKO mice had comparable numbers of total nucleated spleen cells and B220(+) and Mac-1(+) spleen cells both before and after infection. Infected WT mice, however, had significantly more F4/80(+), NK1.1(+), and F4/80(+)Ia(+) spleen cells than infected GKO mice; male WT had more CD3(+) cells than male GKO mice. In comparison with those from WT mice, splenocytes from infected GKO mice had significantly higher proliferation in vitro in response to parasite antigen or concanavalin A stimulation and produced significantly higher levels of IL-10 in response to parasite antigen. Infected WT mice produced more parasite-specific immunoglobulin M (IgM), IgG2a, and IgG3 and less IgG1 than GKO mice. Significant gender differences in both GKO and WT mice in peak parasitemia levels, mortality, phenotypes of spleen cells, and proliferation of and cytokine production by splenocytes in vitro were apparent during infection. These results thus provide unequivocal evidence for the central role of endogenous IFN-gamma in the development of protective immunity against blood-stage P. chabaudi AS.

Early IL-12 p70, but not p40, production by splenic macrophages correlates with host resistance to blood-stage Plasmodium chabaudi AS malaria

In this study, we compared synthesis of IL-12, a potent Th1-inducing cytokine, by splenic macrophages recovered from resistant C57Bl/6 (B6) mice, which develop predominantly Th1 responses, and susceptible A/J mice that mount primarily Th2 responses during early Plasmodium chabaudi AS infection. Quantitative analysis of IL-12 p40 and p70 release by ELISA revealed significant differences between resistant B6 and susceptible A/J mice in the synthesis of biologically active IL-12 p70, but not p40, by splenic macrophages during early blood-stage P. chabaudi AS infection. Despite up-regulation in p40 and p35 mRNA levels, spontaneous release of p40 in vitro by splenic macrophages was not significantly increased following infection in either mouse strain. In contrast, spontaneous release of p70 by splenic macrophages was increased in cells from B6 mice and levels were significantly higher compared with A/J mice. Furthermore, compared with infected A/J hosts, splenic macrophages recovered from infected B6 mice produced significantly greater quantities of IL-12 p70, but not p40, in vitro, following stimulation with lipopolysaccharide (LPS) or malaria parasite antigen (PRBC). Moreover, we found significant increases in the percentage of macrophages earlier in the spleens of infected B6 mice that could further contribute to differences in total p70 levels in vivo. Taken together, these data suggest that macrophage IL-12 synthesis may contribute to the polarization of Th responses seen in resistant B6 and susceptible A/J mice during acute blood-stage malaria.

Deficiency in tumor necrosis factor alpha activity does not impair early protective Th1 responses against blood-stage malaria

Blood-stage Plasmodium chabaudi AS infection was controlled by 4 weeks in mice with deletion of tumor necrosis factor p55 and p75 receptors (TNFR-knockout [KO]) and control wild-type (WT) mice, although female TNFR-KO mice showed slightly but significantly higher parasitemia immediately following the peak. Serum interleukin 12 (IL-12) p70 and gamma interferon (IFN-gamma) levels were similar but tumor necrosis factor alpha levels were significantly higher in TNFR-KO mice than in WT controls. Splenic IL-12 receptor beta1 and beta2 and IFN-gamma mRNA expression, as well as spleen cell production of IFN-gamma and IL-4, were comparable in both mouse types, but IL-10 production was significantly higher in cells from TNFR-KO mice than in cells from WT mice. Lipopolysaccharide-induced NO secretion by splenic macrophages in vitro was significantly reduced but systemic NO3- levels were similar in infected TNFR-KO and WT mice.

Characterization of chronic bronchopulmonary Pseudomonas aeruginosa infection in resistant and susceptible inbred mouse strains

Chronic bronchopulmonary Pseudomonas aeruginosa infection, initiated by intratracheal instillation of 1 to 2 x 10(5) colony-forming units of a mucoid strain of bacteria trapped in agar beads, was characterized in resistant BALB/c mice and susceptible C57BL/6 (B6) mice through 28 d postinfection. B6 mice experienced a more severe infection than BALB/c mice as evidenced by significantly higher mortality and significantly greater weight loss during the first 14 d. Furthermore, B6 mice had significantly higher numbers of bacteria in the lungs through 21 d after infection. Overall, only 22% of these hosts cleared the infection. In contrast, 67% of BALB/c mice cleared the infection. These differences between resistant and susceptible mice were found to correlate with histopathologic differences in the type of inflammation and the extent of tissue damage. An acute, predominantly neutrophilic inflammation and extensive tissue damage were apparent in the lungs of susceptible B6 mice, whereas chronic, granulomatous inflammation and little or no tissue damage were visible in resistant BALB/c mice. The finding of acute inflammation in the lungs of infected B6 mice was confirmed by fluorescence-activated cell sorter (FACS) analyses, which demonstrated that these mice had significantly greater proportions of polymorphonuclear neutrophils in the lungs on Days 7 and 14 after infection than did BALB/c mice. FACS analyses also revealed significant and similar increases in CD3(+) lung cells in both strains as the infection progressed. The CD4/CD8 ratio was significantly greater in BALB/c mice by 21 d after infection when the majority of these animals, but not B6 mice, had cleared the infection.

In vivo IL-12 production and IL-12 receptors beta1 and beta2 mRNA expression in the spleen are differentially up-regulated in resistant B6 and susceptible A/J mice during early blood-stage Plasmodium chabaudi AS malaria

As previously reported, blood-stage Plasmodium chabaudi AS malaria is lethal by days 10-12 postinfection in susceptible A/J mice that mount an early, predominantly Th2 response. In contrast, resistant C57BL/6 (B6) mice clear the infection by 4 wk with an early Th1 response. In this study, we analyzed in vivo production of IL-12, a potent Th1-inducing cytokine, during the first 5 days after P. chabaudi AS infection in these mice. By day 2, serum IL-12 p70 levels were significantly increased in B6 mice over basal levels and were also significantly higher compared with A/J mice that showed no significant changes in serum p70 levels after infection. Splenectomy of resistant B6 mice before infection demonstrated that the spleen is the major source of systemic IL-12 in these hosts. Splenic mRNA levels of both p40 and p35 were significantly higher in A/J mice; however, the ratios of p40/p35 mRNA levels were similarly up-regulated in both strains. Furthermore, B6 but not A/J mice showed significant up-regulation of splenic IL-12R beta2 mRNA over basal levels by days 3 and 4, coincident with sustained up-regulation of splenic IFN-gamma mRNA levels on days 3-5. However, IL-12R beta1 mRNA levels in the spleen were similarly up-regulated in both mouse strains by day 3. Taken together, these data suggest that high systemic IL-12 production, accompanied by an early and sustained up-regulation of both IL-12R beta1 and beta2 mRNA levels in the spleen, as occurs in resistant B6 mice, appears to preferentially induce protective Th1 responses against blood-stage malaria.

Therapy with a combination of low doses of interleukin 12 and chloroquine completely cures blood-stage malaria, prevents severe anemia, and induces immunity to reinfection

The immunoregulatory cytokine interleukin 12 (IL-12) induces host resistance against experimental malaria. In this study, we tested the feasibility of using IL-12 in combination with chloroquine (CQ) to rescue susceptible A/J mice from lethal blood-stage Plasmodium chabaudi AS infection. Combined treatment with low doses of CQ and IL-12 resulted in a >15-fold reduction in the parasite load and 100% survival of A/J mice with established infections. Compared to control mice, which succumbed to severe anemia, CQ-plus-IL-12-treated mice had significantly higher early- and late-stage erythroid-cell progenitors in the bone marrow and spleen, resulting in significantly higher hematocrits, erythrocyte counts, and percentages of reticulocytes. Production of parasite-specific gamma interferon (IFN-gamma) by splenocytes from these mice was upregulated >20-fold relative to controls in parallel with enhanced IFN-gamma mRNA expression. Further, enhanced responsiveness to IL-12 and increased downstream IFN-gamma production in CQ-plus-IL-12-treated mice was evident from increased mRNA expression for the beta1 and beta2 subunits of IL-12 receptor in the splenocytes. Moreover, this combined therapy induced higher levels of anti-malaria antibodies than did CQ alone as well as sterile immunity against reinfection. Because IL-12 can be used at low doses and is effective even in established infections, it may be feasible to use this immunochemotherapeutic approach in human malaria.

Quantitative and qualitative differences in bronchoalveolar inflammatory cells in Pseudomonas aeruginosa-resistant and -susceptible mice

The difference in severity of Pseudomonas aeruginosa-induced chronic lung infection may be determined by differences in host inflammatory responses. In the present study we investigate this possibility using BALB/c and C57Bl/6 mice, resistant and susceptible, respectively, to chronic lung infection with P. aeruginosa. Following intratracheal inoculation of P. aeruginosa-impregnated agar beads, C57Bl/6 mice mounted a stronger inflammatory response with significantly higher total cell numbers in the bronchoalveolar lavage fluid compared with BALB/c mice. While polymorphonuclear leucocytes were the predominant cell in C57Bl/6 mice, macrophages constituted the majority in BALB/c mice at day 7 post-infection. Alveolar macrophages from C57Bl/6 mice showed significantly higher spontaneous production of nitric oxide (NO) at day 7 post-infection compared with BALB/c mice. Following in vitro stimulation with heat-killed Pseudomonas antigen, these cells produced significantly higher NO compared with cells from BALB/c mice at day 21 post-infection. Production of tumour necrosis factor-alpha (TNF-alpha) by alveolar macrophages was significantly higher at day 7 in BALB/c mice compared with C57Bl/6 mice, which showed significantly higher levels at day 28 post-infection. Taken together, these results suggest that defects in the host inflammatory process contribute to the variable outcome of chronic lung infection with P. aeruginosa. An exaggerated inflammatory response dominated by polymorphonuclear cells correlates with susceptibility to infection, whilst a modest inflammatory response dominated by macrophages correlates with resistance. Moreover, the quantity and timing of production of NO and TNF-alpha by alveolar macrophages may modulate the course and outcome of infection.

Dyserythropoiesis and severe anaemia associated with malaria correlate with deficient interleukin-12 production

Complex cytokine interactions occur during blood-stage malaria which offer a unique opportunity to study their influence on the pathogenesis of malarial anaemia. Plasmodium chabaudi AS susceptible A/J mice experience severe and fatal anaemia whereas resistant C57BL/6 (B6) mice survive following moderate anaemia. In this study we analysed the role of IL-12 in erythropoiesis and tested whether the levels of IL-12 produced in these mice correlated with the extent of anaemia. In vitro, IL-12 significantly enhanced the numbers of erythroid burst (BFU-E) and colony forming units (CFU-E) in bone marrow and spleen cells from normal and day 7 infected A/J and B6 mice. Despite the presence of IL-12 in vitro, the level of splenic erythropoiesis in infected A/J mice was significantly lower than in B6 mice. Moreover, sera from infected B6 mice, but not A/J mice, significantly up-regulated erythropoiesis in vitro and this enhancement correlated with several fold higher levels of IL-12 in the sera of B6 compared to A/J mice. Furthermore, the erythropoietic potentiating effect of sera from infected B6 mice was abrogated following depletion of IL-12. Taken together, these findings suggest that defective IL-12 production in A/J mice during the early course of infection may result in fatal anaemia.

Dietary protein and zinc restrictions independently modify a Heligmosomoides polygyrus (Nematoda) infection in mice

The effects of dietary protein and zinc restrictions on Heligmosomoides polygyrus were compared following primary and challenge infection in female BALB/c mice fed either control (24%), marginal (7%) or low (3%) protein combined with either high or low zinc (60 or 3 mg Zn/kg diet). Dietary protein restriction (3%) resulted in significantly lower body weight gain. As well, blood urea nitrogen (BUN) significantly decreased with decreasing dietary protein level. However, neither plasma albumin concentration nor relative thymus or spleen weights were reduced. Marginal zinc deficiency was confirmed by significantly lower tibia and liver zinc concentration, but food intake, body weight gain, relative thymus and spleen weights, and alkaline phosphatase activity were not altered. On day 29 post-primary infection, worm burdens were significantly higher in mice fed either marginal or low protein and in mice fed a low zinc diet, while parasite egg output was significantly higher in mice fed both low protein and low zinc diet. Immune status was compromised in mice fed low protein (significantly lower serum IgG1 and lower eosinophilia), and in mice fed low zinc diet (significantly lower eosinophilia). Early in the infection, IgE titres were elevated in mice fed low protein or low zinc, but IgE titres declined to levels lower that the control diet groups after 14-21 days. On day 29 post-challenge infection, worm burdens and parasite egg output were significantly higher in mice fed low protein, whereas the other group had expelled almost all parasites. Dietary restriction had no effect on IgE. Significantly reduced serum IgG1 titres and eosinophilia in mice fed 3% protein supported the view that low dietary protein but not low zinc increased host susceptibility to H. polygyrus by compromising host immune function following reinfection in immunized mice.

Impaired ability of Cftr knockout mice to control lung infection with Pseudomonas aeruginosa

The present study was aimed at investigating the innate susceptibility of C57BL/6-Cftrunc/Cftrunc knockout [B6-Cftr (-/-)] mice to pulmonary infection with Pseudomonas aeruginosa. Our results indicate that 58.4% of B6-Cftr (-/-) mice died within 6 d following lung infection with 10(5) P. aeruginosa entrapped in agar beads, whereas only 12.1% of B6-Cftr (+/+) mice died over the same period of time. Moreover, the number of bacteria recovered from the lungs of B6-Cftr (-/-) mice 3 and 6 d after infection was significantly higher than that observed in their littermate controls. No correlation was found between the weight or age of the animals and the number of viable bacteria recovered from the lungs of mice. Histopathological examination of lung sections from P. aeruginosa-infected mice revealed that the infection results in a severe bronchopneumonia. Both B6-Cftr (-/-) knockout mice and their littermate controls developed similar lung pathology during the course of infection. Overall, results reported in the present study suggest that a defect at the Cftr locus leads to an exacerbation of P. aeruginosa lung infection resulting in a dramatically increased mortality rate and higher bacterial load.

Energy restriction and zinc deficiency impair the functions of murine T cells and antigen-presenting cells during gastrointestinal nematode infection

This study examined whether the impaired immune responses in zinc deficient- and/or energy-restricted mice exposed to a challenge infection of Heligmosomoides polygyrus might be associated with reduced numbers of spleen cells, altered proportions of spleen cell subpopulations and/or altered function of the T cells or antigen-presenting cells (APC). Female BALB/c mice were given free access to either a zinc-sufficient (60 mg zinc/kg diet, Zn+) or a zinc-deficient diet (0.75 mg zinc/kg diet, Zn-) or were pair-fed (PF) the zinc-sufficient diet. Significant differences in parasite burdens were observed. Worm numbers were lowest in Zn+ mice, intermediate in the PF mice and highest in the Zn- mice, showing that both zinc deficiency and energy restriction reduced protective immunity against the gastrointestinal nematode H. polygyrus. Although the absolute numbers of spleen cells were reduced in both Zn- and energy-restricted (PF) mice, neither deficiency altered the phenotypic distribution of the subpopulations of positive marker cells in the spleen. In vitro functional assays using a 1:1 ratio of APC:T cells showed that T-cell proliferation in response to parasite antigen (Ag) was impaired by a dietary effect of zinc deficiency on T cells and of energy restriction and zinc deficiency on APC function. Consequences of the nutritional deficiencies on cytokine production in response to parasite antigen were more complex: zinc deficiency reduced T-cell function [interleukin-4 and interleukin-5 (IL-4 and IL-5) production], and both nutritional deficits depressed APC functions [IL-4, IL-5, and interferon-gamma (IFN-gamma) production] and T-cell function (IFN-gamma production). Thus, this study showed that zinc deficiency and energy restriction played identifiably distinct roles in regulating host immune responses against the gastrointestinal nematode H. polygyrus.

Interleukin-12 corrects severe anemia during blood-stage Plasmodium chabaudi AS in susceptible A/J mice

The in vivo role of interleukin (IL)-12 in correcting anemia and the underlying defect in erythropoiesis in Plasmodium chabaudi AS-susceptible A/J mice was examined. Six daily intraperitoneal injections of 0.1 microg IL-12 in A/J mice, beginning on the day of infection, rapidly and significantly enhanced bone marrow and splenic erythropoiesis as demonstrated by marked increases in early and late committed erythroid progenitors, the erythroid burst (BFU-E) and colony-forming units (CFU-E), respectively, compared with control mice. The most dramatic effect of IL-12 treatment was a sevenfold increase in the number of splenic CFU-E on day 7 postinfection, compared with untreated, infected A/J mice. Treatment with IL-12 also caused significant increases in hematocrit levels, erythrocyte counts, percentage of reticulocytes, spleen cellularity, and frequencies of BFU-E and CFU-E in the bone marrow and spleen of A/J mice during infection. The frequency of BFU-E in the peripheral blood of these mice was also significantly increased, suggesting enhanced mobilization of precursor cells to the spleen as well as increased production of erythroid precursors in this organ. Consistent with previous observations using higher doses, 0.1 microg IL-12 administered daily for 6 days to normal A/J mice significantly decreased bone marrow erythropoiesis and significantly increased splenic erythropoiesis. However, the influence of IL-12 on erythropoiesis was much more pronounced during ongoing malaria infection. These results suggest a role for IL-12 during blood-stage malaria in not only enhancing the development of protective immunity but also in alleviating malaria-induced anemia by increasing the number of erythroid precursors and enhancing the expansion of committed erythroid progenitors.

Natural killer cell cytokine production, not cytotoxicity, contributes to resistance against blood-stage Plasmodium chabaudi AS infection

Our recent study showed that IL-12 treatment of susceptible A/J mice induces Th1-mediated, protective immunity against lethal blood-stage Plasmodium chabaudi AS infection. To further understand the mechanism of this protection, we examined NK cell cytotoxic (NKCC) and cytokine secretory functions in untreated and IL-12-treated A/J mice, along with resistant C57BL/6 (B6) mice. Normal A/J mice receiving six daily doses of 0.1 microg IL-12 exhibited significant increases in NKCC in total spleen cell populations. Defective NKCC evident in vitro in enriched NK cells from infected A/J mice was corrected by addition of 10 ng/ml IL-12 and was comparable with that seen in B6 mice. In vivo and in vitro analyses revealed that enriched NK cells from day 6 infected A/J mice were defective not only in NKCC, but also in IFN-gamma, and to a certain extent, TNF-alpha secretion, which could also be corrected by IL-12 treatment. Depletion of NK cells from resistant B6 mice resulted in a more severe course of infection, while NK cell-depleted, IL-12-treated A/J mice had significantly higher parasitemia, as well as 100% mortality, suggesting the importance of NK cells in IL-12-mediated protection. NKCC-defective bg/bg mice produced optimum IFN-gamma and TNF-alpha and recovered from infection similar to bg/+ controls; in vivo depletion of these cytokines resulted in significantly higher parasitemia early in infection. Based on these results, we conclude that IFN-gamma, and possibly TNF-alpha, secretion by NK cells during early infection plays a major role in protective immunity to blood-stage malaria.

Natural killer cell cytokine production, not cytotoxicity, contributes to resistance against blood-stage Plasmodium chabaudi AS infection

Our recent study showed that IL-12 treatment of susceptible A/J mice induces Th1-mediated, protective immunity against lethal blood-stage Plasmodium chabaudi AS infection. To further understand the mechanism of this protection, we examined NK cell cytotoxic (NKCC) and cytokine secretory functions in untreated and IL-12-treated A/J mice, along with resistant C57BL/6 (B6) mice. Normal A/J mice receiving six daily doses of 0.1 microg IL-12 exhibited significant increases in NKCC in total spleen cell populations. Defective NKCC evident in vitro in enriched NK cells from infected A/J mice was corrected by addition of 10 ng/ml IL-12 and was comparable with that seen in B6 mice. In vivo and in vitro analyses revealed that enriched NK cells from day 6 infected A/J mice were defective not only in NKCC, but also in IFN-gamma, and to a certain extent, TNF-alpha secretion, which could also be corrected by IL-12 treatment. Depletion of NK cells from resistant B6 mice resulted in a more severe course of infection, while NK cell-depleted, IL-12-treated A/J mice had significantly higher parasitemia, as well as 100% mortality, suggesting the importance of NK cells in IL-12-mediated protection. NKCC-defective bg/bg mice produced optimum IFN-gamma and TNF-alpha and recovered from infection similar to bg/+ controls; in vivo depletion of these cytokines resulted in significantly higher parasitemia early in infection. Based on these results, we conclude that IFN-gamma, and possibly TNF-alpha, secretion by NK cells during early infection plays a major role in protective immunity to blood-stage malaria.

Zinc deficiency and energy restriction modify immune responses in mice during both primary and challenge infection with Heligmosomoides polygyrus (Nematoda)

This study characterized the consequences of zinc-sufficient (Zn+, 60 mg zinc/kg diet, ad libitum), zinc-deficient (Zn-075 mg zinc/kg diet, ad libitum) and energy-restricted (ER, 60 mg zinc/kg diet which was restricted to match food intake of Zn- mice) diets on the in vivo and in vitro immune response of BALB/c mice during both primary and challenge infection with Heligmosomoides polygyrus. In Zn+ mice, both primary and challenge infection with H. polygyrus induced not only a strong Th2 response (IgE, IgG1, eosinophilia, IL-4, IL-5, IL-10), but also elements of a TH1 response (IgG3, IFN-gamma). Zinc deficiency significantly depressed Th2-dependent antibody production during both primary and challenge infection, and reduced mitogen and antigen-induced T cell proliferation during the challenge infection. Th2 cytokine production was reduced by zinc deficiency (IL-4), energy restriction (IL-5) and by zinc deficiency possibly in combination with energy restriction (IL-10) during the primary infection whereas TH1 cytokine production (IFN-gamma) was depressed during the challenge infection by zinc deficiency, possibly together with energy restriction. Both zinc deficiency and energy restriction reduced eosinophilia with the more profound effect being exerted by zinc deficiency. Thus, both zinc deficiency and its concurrent energy restriction modify immune responses in the mice during primary and challenge infection with H. polygyrus.

Differential clearance of glycoforms of IgG in normal and autoimmune-prone mice

In order to understand better the origins of the elevated levels of the glycoform of IgG that lacks galactose on both arms of the oligosaccharide chain (G0%) located in the Fc, which occurs in man and mouse with age, and in particular in autoimmune disease, we investigated the clearance of two glycosylated forms of IgG2a and IgG1 in normal (BALB/c) and autoimmune-prone (MRL/1pr, MRL/+, and non-obese diabetic (NOD)) mice. To investigate the possibility of different rates of catabolism, enzymatically generated glycoforms of monomeric IgG1 and IgG2a (fully glycosylated or G0%), were iodinated and injected into the tail vein of the mice. We found that the G0% IgG2a remained in circulation significantly longer than the fully glycosylated variants, in all of the mouse strains tested. In contrast, the two forms of IgG1 had similar kinetics in all the autoimmune-prone mice, whereas in BALB/c, there was a longer half-life (t1/2) for G0% IgG1. These data suggest that there may be differences in the ability of the IgG glycoforms to bind to the Fc gamma receptors, in particular Fc gamma RI. The clearance rates were found to vary among the strains studied, with MRL/1pr having the fastest catabolic rates for all glycoforms and IgG subclasses tested. This appeared to be due to the presence of circulating IgG and IgM rheumatoid factors (RF). There were significantly increased frequencies and titres for both IgM and IgG RF in MRL/1pr mice compared with the other strains. In contrast, interferon-gamma, known to induce the Fc gamma RI, was found to be similar in the sera, in all of the strains of mice examined. These results suggest that RF probably play an important biological function in the MRL/1pr mice and aid in the clearance of circulating IgG. Our study shows that the state of glycosylation of IgG affects the t1/2 in vivo, and that by removing the terminal sugars (sialic acid and galactose), the antibody (IgG2a) will remain in circulation significantly longer. These observations may thus provide a partial explanation for the increase in relative percentage of this glycoform that occurs with age.

A Th1-associated increase in tumor necrosis factor alpha expression in the spleen correlates with resistance to blood-stage malaria in mice

We investigated the kinetics of tissue-specific mRNA expression and systemic production of tumor necrosis factor alpha (TNF-alpha) and the kinetics of splenic expression of mRNAs of gamma interferon (INF-gamma) and interleukin-4 (IL-4), cytokines that may regulate TNF-alpha production, during the early phase of blood-stage infection with Plasmodium chabaudi AS. Northern blot analysis revealed that resistant C57BL/6 mice, which clear the infection by 4 weeks, had higher levels of TNF-alpha mRNA in the spleen and liver early during infection that did susceptible A/J mice, which succumb to the disease 10 days after initiation of infection. Treatment of resistant mice with a polyclonal anti-TNF-alpha antibody confirmed the protective role of TNF-alpha early during the course of infection. Furthermore, resistant C57BL/6 mice also expressed high levels of mRNA of IFN-gamma (a Th1 marker) and low levels of mRNA of IL-4 (a Th2 marker) in the spleen, whereas susceptible A/J mice had low levels of IFN-gamma mRNA but high levels of TNF-alpha mRNA in the liver and had high levels of TNF-alpha protein in serum, as measured by enzyme-linked immunosorbent assay, later during infection just before death occurred. These results demonstrate that a Th1-associated increase in TNF-alpha mRNA expression in the spleen early during infection correlates with resistance to P. chabaudi AS, whereas increased TNF-alpha mRNA levels in the liver and excessive levels of the TNF-alpha protein in serum later during infection correlate with susceptibility. Thus, the role of the TNF-alpha during malaria appears to depend on the timing and site of its expression and the presence of cytokines regulating its production.

In vivo regulation of nitric oxide production by tumor necrosis factor alpha and gamma interferon, but not by interleukin-4, during blood stage malaria in mice

We investigated whether gamma interferon (IFN-gamma; a Th1 cytokine), tumor necrosis factor alpha (TNF-alpha), and interleukin-4 (IL-4; a Th2 cytokine) modulate nitric oxide (NO) production in vivo during blood stage infection with Plasmodium chabaudi AS. Treatment of resistant C57BL/6 mice, which resolve infection with P. chabaudi AS and produce increased levels of IFN-gamma, TNF-alpha, and NO early during infection, with anti-IFN- gamma plus anti-TNF-alpha monoclonal antibodies (MAbs) resulted in a reduction of both splenic inducible NO synthase mRNA and serum NO3- levels by 50 and 100%, respectively. Treatment with the anti-TNF-alpha MAb alone reduced only serum NO3- levels by 35%, and treatment with the anti-IFN-gamma MAb alone had no effect on NO production by these mice during infection. Susceptible A/J mice, which succumb to infection with P. chabaudi AS and produce increased levels of IL-4 but low levels of IFN-gamma, TNF-alpha, and NO early during infection, were treated with an anti-IL-4 MAb. The latter treatment had no effect on NO production by this mouse strain during infection. In addition, our results also demonstrate that treatment of resistant C57BL/6 mice with anti-IFN-gamma plus anti-TNF-alpha MAbs affects, in addition to NO production, other traits of resistance to P. chabaudi AS malaria such as the peak level of parasitemia and the development of splenomegaly. Furthermore, the change in spleen weight was shown to be an IFN-gamma-independent effect of TNF-alpha. Treatment of susceptible A/J mice during infection with an anti IL-4 MAb had no effect on these markers of resistance. Thus, these results demonstrate that TNF-alpha and IFN-gamma are critical in the regulation of NO production and other traits of resistance during P. chabaudi AS malaria in C57BL/6 mice. These data also indicate that treatment with an anti-IL-4 antibody alone is not able to induce NO production or confer resistance to A/J mice against P. chabaudi AS malaria.

Nitric oxide expression in the spleen, but not in the liver, correlates with resistance to blood-stage malaria in mice

The production and function of nitric oxide during the early phase of blood-stage infection with Plasmodium chabaudi AS was analyzed using two inbred strains of mice that differ in the level of resistance to this parasite. Northern blot analysis of in vivo expression of inducible nitric oxide synthase (iNOS) revealed that early during infection resistant C57BL/6 mice, which clear the infection by 4 wk, have higher levels of iNOS mRNA in the spleen than susceptible A/J mice. In contrast, susceptible A/J mice have significantly increased levels of iNOS mRNA in the liver later in the course of infection just before death occurs. Splenic macrophages recovered from resistant C57BL/6 mice on day 7 postinfection express iNOS mRNA which is up-regulated following overnight stimulation of the cells with LPS. Furthermore, during the first week postinfection, splenic macrophages recovered from resistant hosts produce significantly higher levels of nitrite (NO2-) in vitro in response to LPS than similarly stimulated macrophages from susceptible A/J mice. Increased levels of nitrate (NO3-) were only detected in serum of resistant C57BL/6 mice at the time of peak parasitemia. Treatment with the iNOS inhibitor, aminoguanidine, reduced NO3- levels in serum of C57BL/6 mice and eliminated resistance of these hosts to P. chabaudi AS malaria without affecting parasitemia. These results demonstrate that the ability to produce high amounts of nitric oxide (NO) early during infection with blood-stage P. chabaudi AS correlates with resistance, but that NO may not be involved in parasite killing. Moreover, the tissue site of NO production, that is, spleen vs liver, appears to be critical and correlates with resistance vs susceptibility to P. chabaudi AS malaria, respectively.

Nitric oxide expression in the spleen, but not in the liver, correlates with resistance to blood-stage malaria in mice

The production and function of nitric oxide during the early phase of blood-stage infection with Plasmodium chabaudi AS was analyzed using two inbred strains of mice that differ in the level of resistance to this parasite. Northern blot analysis of in vivo expression of inducible nitric oxide synthase (iNOS) revealed that early during infection resistant C57BL/6 mice, which clear the infection by 4 wk, have higher levels of iNOS mRNA in the spleen than susceptible A/J mice. In contrast, susceptible A/J mice have significantly increased levels of iNOS mRNA in the liver later in the course of infection just before death occurs. Splenic macrophages recovered from resistant C57BL/6 mice on day 7 postinfection express iNOS mRNA which is up-regulated following overnight stimulation of the cells with LPS. Furthermore, during the first week postinfection, splenic macrophages recovered from resistant hosts produce significantly higher levels of nitrite (NO2-) in vitro in response to LPS than similarly stimulated macrophages from susceptible A/J mice. Increased levels of nitrate (NO3-) were only detected in serum of resistant C57BL/6 mice at the time of peak parasitemia. Treatment with the iNOS inhibitor, aminoguanidine, reduced NO3- levels in serum of C57BL/6 mice and eliminated resistance of these hosts to P. chabaudi AS malaria without affecting parasitemia. These results demonstrate that the ability to produce high amounts of nitric oxide (NO) early during infection with blood-stage P. chabaudi AS correlates with resistance, but that NO may not be involved in parasite killing. Moreover, the tissue site of NO production, that is, spleen vs liver, appears to be critical and correlates with resistance vs susceptibility to P. chabaudi AS malaria, respectively.

IL-12-induced protection against blood-stage Plasmodium chabaudi AS requires IFN-gamma and TNF-alpha and occurs via a nitric oxide-dependent mechanism

The effects of IL-12 administration on the development of protective immunity to blood-stage Plasmodium chabaudi AS were analyzed. Treatment of susceptible A/J mice on the day of infection and for 5 days postinfection with various doses 0.025-0.3 microgram) of rIL-12 significantly decreased the peak parasitemia level, but only treatment with 0.1 microgram resulted in increased survival. Treatment of resistant B6 mice with 0.1 microgram of rIL-12 using the same regimen also significantly decreased the peak parasitemia level, but 40% of the animals died. Treatment of these mice with anti-IL-12 mAb resulted in a more severe course of infection, but survival was not significantly altered. The mechanism of IL-12-induced resistance was examined in A/J mice during infection. Compared with spleen cells from untreated mice, cells from IL-12-treated mice produced significantly higher levels of IFN-gamma spontaneously as well as in response to Con A or Ag stimulation on day 7 postinfection. Significantly higher levels of INF-gamma and TNF-alpha were found in the sera of IL-12-treated mice, which correlated with high levels of the nitric oxide (NO) metabolite, NO3-. Furthermore, CD4+T cell depletion was found to abrogate IL-12-induced resistance. Administration of neutralizing mAb against IFN-gamma or TNF-alpha to IL-12-treated mice showed that simultaneous depletion of both cytokines resulted in 100% mortality. The role of NO was investigated by administration of aminoguanidine, a selective inhibitor of cytokine-inducible nitric oxide synthase, to IL-12-treated mice. Significantly increased mortality was observed following treatment twice daily with 9 mg of aminoguanidine, but there was no effect on parasitemia. In conclusion, these results demonstrate that IL-12 regulates the development of resistance to P. chabaudi AS via a CD4+ Th1 response, which involves the cytokines IFN-gamma and TNF-alpha, and is in part NO dependent. Therefore, IL-12, given in the appropriate dose, may be useful in the induction of protective immunity to blood-state malaria.

IL-12-induced protection against blood-stage Plasmodium chabaudi AS requires IFN-gamma and TNF-alpha and occurs via a nitric oxide-dependent mechanism

The effects of IL-12 administration on the development of protective immunity to blood-stage Plasmodium chabaudi AS were analyzed. Treatment of susceptible A/J mice on the day of infection and for 5 days postinfection with various doses 0.025-0.3 microgram) of rIL-12 significantly decreased the peak parasitemia level, but only treatment with 0.1 microgram resulted in increased survival. Treatment of resistant B6 mice with 0.1 microgram of rIL-12 using the same regimen also significantly decreased the peak parasitemia level, but 40% of the animals died. Treatment of these mice with anti-IL-12 mAb resulted in a more severe course of infection, but survival was not significantly altered. The mechanism of IL-12-induced resistance was examined in A/J mice during infection. Compared with spleen cells from untreated mice, cells from IL-12-treated mice produced significantly higher levels of IFN-gamma spontaneously as well as in response to Con A or Ag stimulation on day 7 postinfection. Significantly higher levels of INF-gamma and TNF-alpha were found in the sera of IL-12-treated mice, which correlated with high levels of the nitric oxide (NO) metabolite, NO3-. Furthermore, CD4+T cell depletion was found to abrogate IL-12-induced resistance. Administration of neutralizing mAb against IFN-gamma or TNF-alpha to IL-12-treated mice showed that simultaneous depletion of both cytokines resulted in 100% mortality. The role of NO was investigated by administration of aminoguanidine, a selective inhibitor of cytokine-inducible nitric oxide synthase, to IL-12-treated mice. Significantly increased mortality was observed following treatment twice daily with 9 mg of aminoguanidine, but there was no effect on parasitemia. In conclusion, these results demonstrate that IL-12 regulates the development of resistance to P. chabaudi AS via a CD4+ Th1 response, which involves the cytokines IFN-gamma and TNF-alpha, and is in part NO dependent. Therefore, IL-12, given in the appropriate dose, may be useful in the induction of protective immunity to blood-state malaria.