Stereotactic Cardiac Ablative Radiotherapy (SCAR) for Refractory Ventricular Tachycardia: Western Australia Experience

PURPOSE/OBJECTIVE(S)

Ventricular tachycardia is a potentially life-threatening cardiac condition that is associated with significant morbidity and mortality. Despite advances in medical therapies, implantable cardioverter-defibrillator (ICD) and catheter ablative therapy (CAT), some patients continue to suffer recurrent VT. SCAR is a highly accurate, non-invasive, and novel ablative therapeutic option that has shown promising results in the treatment of refractory VT patients associated with structural heart disease. Early case series and subsequent prospective clinical trials have demonstrated SCAR to be well-tolerated with acceptable safety profiles and consistently decreased VT episodes in VT patients, who failed all conventional antiarrhythmic medications and CAT. The aim of the current study is to report the efficacy and safety/tolerability of SCAR in ICD-dependent patients with refractory VT in Western Australia, Australia.

MATERIALS/METHODS

Seven patients with recurrent refractory VT, deemed high risk or non-suitable for CAT, were referred to GenesisCare at Fiona Stanley Hospital, Western Australia for SCAR between July 2020 and November 2022. Target volume definition and delineation involved interdisciplinary teams by combining all available clinical, electrophysiological mapping and diagnostic/planning cardiac imaging data to generate radiotherapy plans. Patients were treated whilst awake, with a single dose of 25 Gy using VMAT technique on the Synergy Linac with stereotactic X-ray tool capability. Efficacy was assessed by counting the number of episodes of VT and ICD shocks after SCAR. Safety and tolerability were evaluated by treatment related toxicities during follow up.

RESULTS

Of the seven patients referred for SCAR, only five received SCAR as two patients died from their refractory VT before their radiotherapy. For the patients receiving SCAR with at least 6 months follow-up, overall reduction in VT episodes and ICD shocks was 95% and 85%, respectively. No significant treatment-related toxicities were documented during follow-up. Two patients had died. Neither of their deaths were directly attributed to their radiotherapy. One patient died after requesting to cease her antiarrhythmic medications and to have her ICD switched off 2 days after SCAR (against medical advice). The other patient died 431 days after SCAR from aspiration pneumonia after fracturing her cervical spine following a fall at home and was unrelated to her VT.

CONCLUSION

Our data reflects international experience in terms of treatment efficacy and safety profiles of SCAR for patients with refractory VT. SCAR is increasingly recognized as an alternative cardiac ablative option for ICD-dependent VT patients who failed all conventional antiarrhythmic treatments. Nonetheless, careful patient selection and longer-term follow-up are required to ensure the optimal treatment outcomes can be achieved in these patients.

Correlates of physical activity level among hemodialysis patients in Selangor, Malaysia

INTRODUCTION

There is mounting evidence demonstrating the importance of adequate physical activity to promote better well-being among hemodialysis patients. Available data pertaining to the levels of physical activity and its determinants among hemodialysis patients is, however, scarce in Malaysia. The objectives of this study are hence to determine the levels of physical activity and it associated factors among hemodialysis patients.

METHODOLOGY

A total of 70 subjects were recruited from three dialysis centres in Selangor. A face-to-face interview was conducted to obtain socio-demographic data and subjects' knowledge on dietary sources. Medical history, biochemical parameters and weight status were obtained from medical records. Physical activity level (PAL) was assessed using the Global Physical Activity Questionnaire (GPAQ).

RESULTS

A total of 81.4% and 18.6% of the respondents had low and moderate PALs, respectively. Thus, none of the respondents had high PAL. Serum creatinine, education level, personal income and knowledge score on potassium-related medical complications were factors found to correlate significantly with PAL. Multiple linear regression analysis showed that higher PAL was predicted by a lower knowledge score on dietary sodium source, higher education and higher serum creatinine.

CONCLUSION

Despite consistent documentation of the potential positive impact of physical exercise on hemodialysis outcomes, the level of physical activity remains low among these patients. It is hoped that these findings can add to the existing body of knowledge and serve as a supporting document for the formulation of appropriate interventions to improve the status of physical activity among hemodialysis patients in Malaysia.

Investigation of the binding preference of reovirus sigma1 for junctional adhesion molecule A by classical and steered molecular dynamics

Biochemical studies have determined that reoviruses attach to cells by combining attachment protein sigma1 to the binding interface of its receptor protein junctional adhesion molecule A (JAM-A), and the interface normally takes care of the homodimerization of JAM-A. Tighter binding and slower dissociation of for the sigma1-JAM complex than for the JAM-JAM complex have been probed by both biological and atomic force microscopy experiments; however, the mechanism of the binding preference of the attachment protein for JAM-A still remains unclear. With the help of classical and steered molecular dynamics and energy calculations, the unbinding forces and kinetic properties of the complexes are investigated, together with detailed structural information analyses. A multireceptor mechanism is proposed for the binding preference, which can be helpful for future viral infection and vector targeting studies.

Repetitive lumbar punctures as treatment for normal pressure hydrocephalus

Selected normal pressure hydrocephalus (NPH) patients cannot be treated by shunt operation because of the procedure's high complication rate. We have treated cases in which prolonged clinical improvement of NPH was experienced after one or two lumbar punctures (LPs). We evaluated the predictors of prolonged improvement of NPH symptoms by repeated LP. Thirty-one NPH patients were retrospectively evaluated (age 72.5 +/- 5.8 years). Gait disturbance, urinary incontinence, and cognitive impairment were semiquantified. We divided the patients into three groups (non-responders, temporary responders, and prolonged responders) according to their responses after LP. We analyzed the characteristics of the groups. Gait disturbance (p = 0.046) and urinary incontinence (p = 0.040) scores and total NPH symptom score (p = 0.007) after cerebrospinal fluid drainage were more significantly improved in prolonged responders than in temporary responders. On multiple logistic regression analyses, total NPH score improvement was the only predictor of the prolonged responders (p = 0.03, odds ratio 0.148). Our study showed that some NPH patients could maintain favorable courses for at least 1 year after LP without shunt operation. Repeated LP could be an alternative treatment in selected NPH patients.

Mechanistic insights into the physiological functions of cell adhesion proteins using single molecule force spectroscopy

Intercellular adhesion molecules play an important role in regulating several cellular processes such as a proliferation, migration and differentiation. They also play an important role in regulating solute diffusion across monolayers of cells. The adhesion characteristics of several intercellular adhesion molecules have been studied using various biochemical assays. However, the advent of single molecule force spectroscopy as a powerful tool to analyze the kinetics and strength of protein interactions has provided us with an opportunity to investigate these interactions at the level of a single molecule. The study of interactions involving intercellular adhesion molecules has gained importance because of the fact that qualitative and quantitative changes in these proteins are associated with several disease processes. In this review, we focus on the basic principles, data acquisition and analysis in single molecule force spectroscopy experiments. Furthermore, we discuss the correlation between results obtained using single molecule force experiments and the physiological functions of the proteins in the context of intercellular adhesion molecules. Finally, we summarize some of the diseases associated with changes in intercellular adhesion molecules.

CT planning for breast cancer

Radiotherapy to the affected breast or chest wall is well established as an integral part of postoperative management of breast cancer. However, it is known to be associated with increased cardiac and pulmonary morbidities and mortalities. Modern technologies, such as CT planning, have shown to improve treatment planning by accurately delivering optimal doses to the target volumes, while minimizing doses to sensitive structures, thus reducing potential treatment-related adverse effects. The purpose of this study is to report on our experiences with CT planning of adjuvant radiotherapy for breast cancer.

Cloning and characterization of Arabidopsis and Brassica juncea flavin-containing amine oxidases

Polyamines (PAs) are low molecular weight metabolites involved in various physiological and developmental processes in eukaryotic and prokaryotic cells. The cellular PA level is regulated in part by the action of amine oxidases (AOs) including copper diamine oxidases (DAOs) and flavoprotein polyamine oxidases (PAOs). In this study, the isolation and characterization of flavin amine oxidases (FAOs) from Brassica juncea (BJFAO) and Arabidopsis (ATFAO1) are reported that were clustered in the same group as polyamine oxidases from maize (MPAO) and barley (BPAO1) and monoamine oxidases from mammalian species. ATFAO1 was temporally and spatially regulated in Arabidopsis and showed distinct expression patterns in response to different stress treatments. To investigate the in vivo function of FAO, transgenic Arabidopsis plants expressing sense, antisense, and double-stranded BJFAO RNAs were generated and those with altered activity of FAOs were selected for further characterization. It was found that the shoot regeneration response in transgenic plants was significantly affected by the modulated PA levels corresponding to FAO activities. Tissues that originated from transgenic plants with down-regulated FAO activity were highly regenerative, while those from transgenic plants with upregulated FAO activity were poorly regenerative. The shoot regeneration capacity in these transgenic plants was related to the levels of individual PAs, suggesting that FAO affects shoot regeneration by regulating cellular PAs. Furthermore, it was found that the effect of FAO activity on shoot regeneration was exerted downstream of the Enhancer of Shoot Regeneration (ESR1) gene, which may function in a branch of the cytokinin signalling pathway.

Biophysical approaches for studying the integrity and function of tight junctions

Cell-cell adhesion is an extremely important phenomenon as it influences several biologically important processes such as inflammation, cell migration, proliferation, differentiation and even cancer metastasis. Furthermore, proteins involved in cell-cell adhesion are also important from the perspective of facilitating better drug delivery across epithelia. The adhesion forces imparted by proteins involved in cell-cell adhesion have been the focus of research for sometime. However, with the advent of nanotechnological techniques such as the atomic force microscopy (AFM), we can now quantitatively probe these adhesion forces not only at the cellular but also molecular level. Here, we review the structure and function of tight junction proteins, highlighting some mechanistic studies performed to quantify the adhesion occurring between these proteins and where possible their association with human diseases. In particular, we will highlight two important experimental techniques, namely the micropipette step pressure technique and the AFM that allow us to quantify these adhesion forces at both the cellular and molecular levels, respectively.

Light and scanning electron microscopic evaluation of Glyde File Prep in smear layer removal

AIM

To evaluate the effectiveness of Glyde File Prep used in conjunction with sodium hypochlorite irrigation in the removal of smear layer produced during root canal instrumentation.

METHODOLOGY

Thirty-nine extracted human teeth with single root canals were used. Access cavities were prepared and the teeth divided into three groups of 13 teeth each. Each group was treated by one of the three different regimes of irrigation and conditioning during root canal instrumentation. Group A: 0.5 mL of 1% NaOCl irrigation after each file size with an additional final irrigation of 10 mL 1% NaOCl; group B: 0.5 mL of 1% NaOCl irrigation after each file size with an additional final irrigation of 10 mL 17% EDTA; group C: Glyde File Prep coated on each instrumentation file used in conjunction with 0.5 mL 1% NaOCl irrigation after each file size and an additional final irrigation of 10 mL 1% NaOCl. The teeth were then longitudinally grooved and sectioned. Root canal cleanliness was evaluated with the aid of a Nikon light microscope (x40 and x100) and scanning electron microscope (x1000 and x3000). The debris scores obtained at three canal regions were compared statistically within the same group and among different groups using repeated measurements of analysis of variance (anova) with Bonferroni adjustments and anova with posthoc Tukey HSD, respectively.

RESULTS

The canals treated with EDTA and Glyde File Prep were significantly cleaner than those treated with NaOCl alone. The apical region of the root canals generally displayed more residual smear layer, but the difference was not significant.

CONCLUSIONS

Used in conjunction with NaOCl irrigation, Glyde File Prep was effective in removing smear layer produced during root canal instrumentation.

Instability in a laser-diode-pumped microchip Nd:YAG laser in a n-ary product scheme

Dynamical instability, chaotic pulsations, and generalized bistability have been observed in a laser-diode-pumped microchip Nd:YAG laser operating in a double transition scheme in which lasing occurs on two transitions with overlapping gain profiles, F(3/2)(4)(2)? I(11/2)(4)(3) and F(3/2)(4)(1)? I(11/2)(4)(2), and simultaneously involves excited Nd atoms from different sublevels of the upper manifold. The modeling of the experimental results requires rate equations that include cross-gain coupling among oscillating modes that belong to different transitions whose population inversion densities are determined by the Boltzmann distribution.

Association of tocolytic therapy with antenatal steroid administration and infant outcomes. Newborn Lung Project

The use of tocolytic agents to halt premature labor is controversial. We examine a database on very low-birth-weight infants born following the onset of premature labor (n = 540) for association between tocolytic and antenatal steroid therapy, and to assess neonatal and childhood outcomes following combined therapy. Data are from a multicenter regionally based study of all infants below 1501 g at seven neonatal intensive care units (NICUs) in Wisconsin and Iowa, born August 1, 1988 through June 30, 1991. Infant outcomes analyzed are death in the first 30 days, respiratory distress syndrome (RDS), and intraventricular hemorrhage (IVH). Fewer deliveries occurred within 12 hours of labor onset with tocolytics (61 vs. 75% without). A strong association between tocolytic therapy and antenatal steroid administration was found [adjusted odds ratio OR = 5.7, 95% confidence interval CI: (3.3, 10.0)]. Tocolytics were associated with lower mortality in the first 30 days [OR = 0.29, CI: (0.15, 0.56)]. Joint administration of tocolytics and antenatal steroids versus neither was associated with lower incidence of the combined outcome of respiratory distress syndrome (RDS) or death [OR = .30, CI: (0.15, 0.60)] and grade III-IV IVH or death [OR = 0.35, CI: (0.14, 0.98)]. Tocolytic therapy alone was not associated with IVH grade III-IV [OR = 1.0, CI: (0.57, 1.9)] among survivors.

A computer program in QuickBasic for the selection of tests for the identification of Helicobacter pylori

Reliable microbiological tests are needed for the identification of bacteria. A program has been written in QuickBasic to identify such tests by using a formula that is based on Gyllenberg's Sum of C(i) and Gyllenberg's Rank R(i). A total of 139 papers on a newly isolated bacterium, Helicobacter pylori, was used as data source for the coding of test results into an input file. The program outputs a list that aids in the determination of suitable tests for the identification of H. pylori. These tests chosen by the formula were found to be correctly identified as supported by later publications on the bacterium.

Influence of primary tumor site on host anti-tumor immunity

Stage IV-S neuroblastoma, characterized by a primary tumor plus disseminated tumors in liver, skin and bone marrow, has a favorable clinical prognosis when compared to metastatic Stage IV neuroblastoma. This favorable outcome also characterized mice receiving tumor transplants to these "IV-S" sites. We report the testing of the hypothesis that enhanced anti-tumor immunity in "IV-S" site neuroblastoma recipients explains this improved survival. A million murine C1300 neuroblastoma cells were inoculated into 256 A/J mice to either "IV-S" sites of skin, liver, peritoneal cavity, or to the disseminated stage "IV" sites of subcutaneous tissue, muscle, kidney and lung. After 21 and 28 days of tumor growth, spleen cells from tumor bearing mice were harvested and analyzed by a 51 Cr release lymphocytotoxicity assay. Cytotoxic T cell activity was consistently higher at day 28 than day 21. In the liver and in the peritoneal cavity, cytotoxic T cell activity was higher than in other organs, and at day 28 these values were significantly higher than Stage "IV" sites. On the other hand, skin is not a immunologically privileged site in vivo study.

Astigmatism following cataract surgery: comparison of a scleral and a corneal incision in a mixed group of patients with and without glaucoma

We retrospectively analysed the course of postoperative corneal astigmatism and corrected visual acuity after extracapsular cataract extraction and posterior chamber lens implantation with either a corneal or a scleral incision in 170 eyes of 155 patients with and without glaucoma. A continuous 10/0 nylon shoelace suture was used for wound closure in two groups. In a third group, corneal wound closure was performed with a shorter shoelace suture in combination with two vicryl wing sutures at 11 and 1 o'clock. Although early postoperative mean astigmatism in eyes operated through a corneal incision was high (range 2.92-6.67 diopters at 1 month postoperatively) and significantly different when compared to eyes operated through a scleral incision (1.96 diopters), final mean astigmatism did not differ significantly between those two groups. Moreover, in 27% of eyes operated through a corneal incision, mean astigmatism at 2 months postoperatively was not significantly different from the scleral group and suture removal was not necessary. There was no statistically significant difference in corrected visual acuity over the entire study period between groups. Since safety and functional results of the corneal incision were not different from the scleral incision, we prefer a corneal incision in cataract surgery because of its surgical advantages, especially in patients with cataract and coexisting glaucoma.

The role of fine needle aspiration for breast cancer in the climacteric--a preliminary report

Fine needle biopsy has been used with great accuracy in the diagnosis of breast tumours. There have been few reports on its efficacy as an adjunct to other breast screening techniques like x-ray mammography. Abnormal mammograms in the absence of a palpable breast lump are sometimes detected in the climacteric and these pose a problem of tissue sampling for pathologic diagnosis. We have tried to evaluate the technique of radiologically guided fine needle aspiration in such patients. Our report is of an initial series of 13 cases of non-palpable, mammographically abnormal breast lesions. Eight cases were fibroadenoma, 4 cases mammary dysplasia and 1 a benign breast lesion. Representative cytologic samples were obtained in 11 of our 13 cases. Cytologic diagnosis should be correlated with mammographic findings.

Vagino-peritoneal fistula from a cervical carcinoma

Locally advanced cervical carcinoma may present with a recto-vaginal or a vesico-vaginal fistula but these are more commonly complications following surgery, radiation, or combination therapy for advanced disease. A vagino-peritoneal fistula in a patient with a cervical carcinoma at initial presentation is reported. The method of confirming the diagnosis, problems of stage allocation, and management are discussed.

Evaluation of the whole blood lymphocyte transformation assay for scrub typhus exposure: adaptability to field sample collection

The optimal conditions for the determination of exposure to scrub typhus by the whole blood lymphocyte transformation assay was 7 days culture of 10% blood in RPMI 1640 medium supplemented with 10% human AB-negative serum and L-glutamine with 50-200 micrograms protein/ml of Karp, Kato, or Gilliam strain membrane antigen. A simple exponentially decaying linear model shows the decrease in lymphocyte viability, the ability of sensitized cells to be stimulated with PHA mitogen, and the corresponding decrease in stimulation by scrub typhus antigens with increasing time of preincubation on ice. The lower limit of stimulation index for the detection of scrub typhus by whole blood lymphocyte transformation assay was 4.0 with a type I error of 1%.

Pathologic activity of Plasmodium berghei prevented but not reversed by dexamethasone

Dexamethasone has recently been shown to block the production of cachectin (implicated in the pathogenesis of cerebral malaria) if administered prior to endotoxin induction of mouse macrophages. Using the hamster cheek pouch-cerebral malaria model, we tested the hypothesis that dexamethasone is effective as a therapeutic agent in severe malaria if given before some yet undefined trigger point in the disease. Infected hamsters were treated with dexamethasone (0.7 mg/kg) daily on days 7-12, 4-12, or 1-12 post-challenge. When treatment was started on day 1, whole body oxygen consumption (used as a measure of erythrocyte transport to sites of diffusion) on day 12 was greater than (P less than 0.05) that of infected control animals, though the degree of anemia was no different in treated and untreated groups. Furthermore, treatment produced a reduction in monocyte accumulation, capillary malfunction, and monocyte/red blood cell aggregate formation observable in the cheek pouch in vivo and a similar reduction in monocyte presence, capillary pathologic change, and multifocal hemorrhage in the brain on postmortem. These data suggest that mediator(s), whose production can be blocked by pretreatment with dexamethasone, are involved in the pathogenesis of disease leading to death of the Plasmodium berghei infected hamster.

A sensitive malaria immunoperoxidase assay for the detection of Plasmodium falciparum antibody

A new and rapid malaria immunoperoxidase assay using the enzyme horseradish peroxidase in place of fluorescein isothiocyanate was developed to allow the serological measurement of antimalarial antibody by light microscopy. Acetone-fixed thin blood films prepared from cultured Plasmodium falciparum were used as the source of antigen. This malaria immunoperoxidase assay is as sensitive as, and occasionally more sensitive than, the indirect fluorescent antibody assay. It is easy to perform and the antigen used does not show cross-reactivity with sera from nonmalarial diseases.

Detection of surface antigen in Rickettsia tsutsugamushi infected mouse reticuloendothelial cells

Antibody produced by immunizing CBA/CaJ mice with RE cells from C57B1/6J mice infected 14 days earlier with R. tsutsugamushi Gilliam strain bound readily to Gilliam strain non-cell associated rickettsiae and less readily to the periphery of infected RE cells. Conversely, antibody produced by immunizing with RE cells infected 21 days earlier did not bind to Gilliam rickettsiae but bound to the surface of RE cells from mice infected 21 days earlier. This binding was not related to alloantibodies because these were absorbed prior to testing. The demonstration of rickettsial antibody staining of infected cell associated antigen(s) in this assay system provides a new method for the detection of R. tsutsugamushi infection.

Suppression of lymphocyte responsiveness during acute Rickettsia tsutsugamushi infection in mice

Lymphocytes from Inbred Balb/cyJ mice infected subcutaneously with 10(3) MLD50 of Rickettsia tsutsugamushi Karp strain were unresponsive to rickettsial antigens and phytohemagglutinin in the lymphocyte transformation assay between 11 and 28 days post-infection. There was, however, no correlation between this suppressed responsiveness to rickettsial antigens and the immune capacity to resist a normally lethal ip challenge with the Karp strain. Fourteen days after infection, these mice survived a potentially lethal Karp challenge. Naive recipients of day 14 post-infection mouse splenic lymphocytes also were partially protected against ip challenge. Karp strain-specific anti-rickettsial antibody reached a peak geometric mean titer of 260 during the period of apparent cellular unresponsiveness. However, day 14 post infection mice showed a fourfold decrease of antibody response to a T-dependent antigen, which suggests the presence of T-dependent antibody suppression in these mice.

Thymosin fraction 5: effects on T cell functions in mice immunosuppressed by severe dietary protein deficiency

The present studies were performed to determine the effects of severe protein deficiency and subsequent injection of thymosin fraction 5 (TF5) on T and B cell functions. BALB/c mice, 4 weeks old, were fed a normal protein (21%), a low protein (4%) or a protein free (0%) diet and then injected with TF5 or buffer (PBS). A significant increase was observed in the PHA (phytohemagglutinin) and LPS (lipopolysaccharide) induced mitogenesis with increasing age of the well-nourished, PBS injected animals. The severely protein malnourished mice, PBS injected and the well nourished mice, injected with TF5 had smaller increases in both B and T cell mitogenesis with increasing age. TF5 injection of the malnourished mice increased PHA and LPS mitogenesis nearly to the levels of the well-nourished mice. The protein malnourished mice consistently had higher serum corticosteroid levels than controls. No changes in serum corticosteroids were observed with TF5 injection of controls, but there was a significant decrease in the corticosteroid levels of the severely malnourished with TF5 injection. Cytoxicity assays of T cell function, antibody dependent cellular cytoxicity and cytoxicity to mouse thymona tumor cells, in mice fed moderately protein deficient diets showed suppression compared to controls fed 20% protein. TF5 injection partially and temporarily increased these functions in the malnourished mice.

Effect of vitamin E on cell-mediated immune responses and serum corticosterone in young and maturing mice

A high vitamin E diet altered cell-mediated immune responses of maturing BALB/c mice. Serum corticosterone concentrations in these animals were also determined because of the pharmacological effect the glucocorticoid hormone has on immune systems. Mice receiving high vitamin E diet (twenty times higher than the vitamin E concentration in control diet) showed significant increase in antibody-dependent cellular cytotoxicity (ADCC) activity within a week after initiation of the diet. Adult levels of spleen and intestinal ADCC activities were reached at a much younger age in these high vitamin E-treated animals. In addition, there was a good correlation between increase in spleen and intestinal ADCC activities and the significantly lower than control concentration of serum corticosterone in these mice. However, after prolonged consumption of high vitamin E diet, decrease in ADCC activity was observed in these mice. No significant differences in PHA-induced spleen lymphocytes [3H]-thymidine incorporation, along with a decrease in serum corticosterone levels, were observed in mice given either high vitamin E or the control diets throughout most study periods.

Immune components of the intestinal mucosae of ageing and protein deficient mice

The studies were designed to investigate the effect of ageing and low protein (4%) diet on antibody-dependent cell-mediated cytotoxicity (ADCC) and IgA concentration in the intestine. Both ADCC activity and IgA concentration were shown to reach mature levels at 17 weeks old. The effect of ageing was greater on ADCC activity which showed a drastic drop in activity at 75 weeks old than IgA which had only a slight decline in concentration at this age. The low protein diet has a greater suppressive effect on IgA concentration than on ADCC activity. As the duration of feeding low protein to the young mice increased, greater decline in IgA concentration in the intestine was observed. There was, however, no significant difference from the normal mice in ADCC activity and IgA concentration of aged and adult mice given short term (8 weeks) low protein diet.

Transfer of immunity to cryptococcosis by T-enriched splenic lymphocytes from Cryptococcus neoformans-sensitized mice

Splenic enriched T-cells and sera were obtained from inbred CBA/J mice injected 7 or 35 days earlier with either 10(3) viable Cryptococcus neoformans or sterile physiological saline. The transfer of enriched T-cells collected 7 days after immunization or of normal enriched T-cells did not transfer immunity to C. neoformans or delayed-type hypersensitivity responsiveness to cryptococcal culture filtrate (CneF) antigen to the recipients. However, enriched T-cells harvested 35 days after immunization, when transferred to recipient mice, were able to confer immunity as indicated by the reduction in numbers of C. neoformans cells in the tissues, and they also transferred delayed-type hypersensitivity responsiveness to CneF antigens. Sera from either sensitized or normal mice were unable to transfer immunity to recipient animals. These results suggested that there was a time requirement for development of the immune response in the donor mice and that T-cells were crucial in the host defense against a cryptococcal infection. Culturing of day-35 C. neoformans-sensitized T-cells in the presence of homologous antigen (CneF) but not in the presence of heterologous antigen (purified protein derivative or 2, 4-dinitro-1-fluorobenzene) induced the production of migration inhibition factor, thus indicating that lymphocytes from C. neoformans-injected mice were specifically sensitized to CneF antigen.

Host-etiological agent interactions in intranasally and intraperitoneally induced Cryptococcosis in mice

Inbred CBA/J mice were used in developing a defined in vivo model for studying host-parasite relationships in cryptococcosis. Mice were infected either intranasally or intraperitoneally with 10(3) viable Cryptococcus neoformans cells. At weekly intervals over a 92-day period, C. neoformans growth profiles in the lungs, spleens, livers, and brains of the infected animals were determined. In addition, humoral and delayed-type hypersensitivity responses and cryptococcal antigen levels were assayed in these mice. Intranasally infected mice developed strong delayed-type hypersensitivity reactions in response to cryptococcal culture filtrate (CneF) antigen, and there was good correlation between acquisition of delayed-type hypersensitivity and the reduction of C. neoformans cell numbers in infected tissues. In contrast, intraperitoneally infected mice displayed greater numbers of C. neoformans cells in tissues and had somewhat suppressed delayed-type hypersensitivity responses to CneF antigen. Anticryptococcal antibodies were not detected in intranasally or intraperitoneally infected mice, but cryptococcal polysaccharide antigen titers were relatively high in both groups. The transfer of sensitized spleen cells from intranasally infected mice to syngeneic naive recipient mice resulted in the transfer of delayed-type hypersensitivity responsiveness to cryptococcal antigen in the recipients. The intranasally induced infection in mice was similar to the naturally acquired infection in humans; therefore we are proposing that this murine-cryptococcosis model would be useful in gaining a greater understanding of host-etiological agent relationships in this disease.