[Primary pericardial synovial sarcoma]

Primary pericardial synovial sarcoma is an extraordinarily very rare tumor with a poor prognosis, and little is known about its therapeutic management. We describe the case of a 51-year-old woman patient who underwent incomplete surgical resection, chemotherapy, and radiotherapy. To the best of our knowledge, no primary pericardial synovial sarcoma has been described which, after surgery, remains asymptomatic for 5 years, and until a control CT scan detects cardiac metastases that compromised the lumen of the right cavities and with chemotherapy, echocardiography demonstrated complete resolution of cardiac metastases.

[Experience in infective endocarditis over 30 years in a hospital in Buenos Aires]

Infective endocarditis (IE) is a disease that in recent decades has shown changes in its presentation, diagnosis and treatment. This is a prospective study of 252 patients admitted at a reference hospital in Buenos Aires, Argentina, with a diagnosis of IE and they were grouped according to the decade of admission: Group A: from January 1988 to December 1997 (89 patients -35.3%-), Group B: from January 1998 to December 2007 (88 patients -34.9%-), and Group C: from January 2008 to December 2018 (75 patients -29.8%). The characteristics were analyzed and compared: age, sex, underlying heart disease, blood cultures and germs, presence of vegetations, surgical treatment and in-hospital mortality. Over the three decades, the predisposing heart condition showed that rheumatic valve disease decreased significantly (p < 0.0001) while the IE in cardiac devices also increased significantly (p < 0.0001). The percentage of blood culture-negatives decreased significantly over the years (p < 0.0001). In-hospital mortality showed a downward trend in the last decade (p = 0.069). The development of complications during hospitalization, the indication for surgery, and the presence of heart failure on admission were independent predictors of in-hospital mortality. The presence of vegetations and febrile syndrome on admission were independent predictor for lower mortality. The comparison over the years showed important changes in the epidemiological profile of IE. Probably due to advances in diagnostic techniques, treatment, and the implementation of interdisciplinary IE teams in the last decade, in-hospital mortality shows a strong tendency to decrease.

4091Mechanical dispersion by speckle tracking echocardiography in fabry disease

Background

Fabry disease is a rare X-linked storage disorder caused by a deficiency of the lysosomal enzyme α-galactosidase A and generally causes multi-organ dysfunction. Heart disease is the main cause of death, due to severe left ventricular (LV) systolic dysfunction and sudden death. In several heart diseases, the LV systolic dysfunction and ventricular arrhythmias are associated with mechanical dispersion (MD). The presence of MD in patients with FD has not been studied yet. In this cross-sectional study, we investigated the prevalence of MD in patients with FD.

Methods

Complete echocardiographic and speckle tracking echocardiographic (STE) data were collected. MD is an index of inter-segmental discoordination of contraction which has been used to quantify LV dyssynchrony and was defined as the standard deviation (SD) of time to peak negative strain in 17 left ventricular segments. Patients were divided into two groups according to whether or not they had left ventricular hypertrophy (LVH). MD was defined as an SD >49 msec.

Results

We studied 108 patients with FD, 24 patients (22%) were excluded due to inadequate imaging quality or presence of comorbidities, so the final study population consisted of 84 patients (mean age 33.3±14.6 years, 60.7% women). LVH in FD appears at older ages than in patients without LVH (48±12.5 y/o vs 27.8±11.1 y/o, p<0.0001). Patients with FD without LVH (Group I) showed normal global longitudinal peak strain (GLPS) (21.2±2.5%) and no MD (32.7±8.8 msec). In Group II (n=23) patients with FD with LVH, 17 (73.9%) had MD >49 msec prolonged mechanical dispersion (73.3±20.7 msec) and reduced GLPS (13.6±4.0%). MD was more pronounced in Fabry patients with LVH than in patients without LVH (63.4±24.7 msec vs. 32.7±8.8 msec, p<0.0001). GLPS was lower in Fabry patients with LVH than in patients without LVH (15.3±4.7% vs 21.2±2.5%, p<0.0001).

Figure 1

Conclusions

To our knowledge, this is the first study to demonstrate the prevalence of mechanical dispersion in patients with FD. Mechanical dispersion was seen in 73.9% of patients with FD with LVH. This dyssynchrony should be taken into account in patients who develop heart failure or life-threatening ventricular tachyarrhythmias.

[Clinical examination and the Valsalva maneuver in heart failure]

Congestion in heart failure patients with reduced ejection fraction (HFrEF) is relevant and closely linked to the clinical course. Bedside blood pressure measurement during the Valsalva maneuver (Val) added to clinical examination may improve the assessment of congestion when compared to NT-proBNP levels and left atrial pressure (LAP) estimation by Doppler echocardiography, as surrogate markers of congestion in HFrEF. A clinical examination, LAP and blood tests were performed in 69 HFrEF ambulatory patients with left ventricular ejection fraction ≤ 40% and sinus rhythm. Framingham Heart Failure Score (HFS) was used to evaluate clinical congestion; Val was classified as normal or abnormal, NT-proBNP was classified as low (< 1000 pg/ml) or high (≥ 1000 pg/ml) and the ratio between Doppler early mitral inflow and tissue diastolic velocity was used to estimate LAP and was classified as low (E/e'< 15) or high (E/e' ≥ 15). A total of 69 patients with HFrEF were included; 27 had a HFS ≥ 2 and 13 of them had high NT-proBNP. HFS ≥ 2 had a 62% sensitivity, 70% specificity and a positive likelihood ratio of 2.08 (p=0.01) to detect congestion. When Val was added to clinical examination, the presence of a HFS ≥ 2 and abnormal Val showed a 100% sensitivity, 64% specificity and a positive likelihood ratio of 2.8 (p = 0.0004). Compared with LAP, the presence of HFS = 2 and abnormal Val had 86% sensitivity, 54% specificity and a positive likelihood ratio of 1.86 (p = 0.03). In conclusion, an integrated clinical examination with the addition Valsalva maneuver may improve the assessment of congestion in patients with HFrEF.

Predicting total dissolved solids release from central Appalachian coal mine spoils

Appalachian USA surface coal mines face public and regulatory pressure to reduce total dissolved solids (TDS) in discharge waters, primarily due to effects on sensitive macroinvertebrates. Specific conductance (SC) is an accurate surrogate for TDS and relatively low levels of SC (300-500 μS cm(-1)) have been proposed as regulatory benchmarks for instream water quality. Discharge levels of TDS from regional coal mines are frequently >1000 μS cm(-1). The primary objectives of this study were to (a) determine the effect of rock type and weathering status on SC leaching potentials for a wide range of regional mine spoils; (b) to relate leachate SC from laboratory columns to actual measured discharge SC from field sites; and (c) determine effective rapid lab analyses for SC prediction of overburden materials. We correlated laboratory unsaturated column leaching results for 39 overburden materials with a range of static lab parameters such as total-S, saturated paste SC, and neutralization potential. We also compared column data with available field leaching and valley fill discharge SC data. Leachate SC is strongly related to rock type and pre-disturbance weathering. Fine-textured and non-weathered strata generally produced higher SC and pose greater TDS risk. High-S black shales produced the highest leachate SC. Lab columns generated similar range and overall SC decay response to field observations within 5-10 leaching cycles, while actual reduction in SC in the field occurs over years to decades. Initial peak SC can be reliably predicted (R(2) > 0.850; p < 0.001) by simple lab saturated paste or 1:2 spoil:water SC procedures, but predictions of longer-term SC levels are less reliable and deserve further study. Overall TDS release risk can be accurately predicted by a combination of rock type + S content, weathering extent, and simple rapid SC lab measurements.

The effects of diet-induced obesity on B cell function

B-1 and B-2 B cell subsets carry out a diverse array of functions that range broadly from responding to innate stimuli, antigen presentation, cytokine secretion and antibody production. In this review, we first cover the functional roles of the major murine B cell subsets. We then highlight emerging evidence, primarily in preclinical rodent studies, to show that select B cell subsets are a therapeutic target in obesity and its associated co-morbidities. High fat diets promote accumulation of select murine B cell phenotypes in visceral adipose tissue. As a consequence, B cells exacerbate inflammation and thereby insulin sensitivity through the production of autoantibodies and via cross-talk with select adipose resident macrophages, CD4(+) and CD8(+) T cells. In contrast, interleukin (IL)-10-secreting regulatory B cells counteract the proinflammatory profile and improve glucose sensitivity. We subsequently review data from rodent studies that show pharmacological supplementation of obesogenic diets with long chain n-3 polyunsaturated fatty acids or specialized pro-resolving lipid mediators synthesized from endogenous n-3 polyunsaturated fatty acids boost B cell activation and antibody production. This may have potential benefits for improving inflammation in addition to combating the increased risk of viral infection that is an associated complication of obesity and type II diabetes. Finally, we propose potential underlying mechanisms throughout the review by which B cell activity could be differentially regulated in response to high fat diets.

Valve replacement with bileaflet HP-Biplus mechanical prostheses versus standard prostheses: long-term results

BACKGROUND AND AIM OF THE STUDY

At present, no reports are available regarding the hemodynamic assessment and survival of patients undergoing valve replacement with HP-Biplus prostheses. Hence, the present study was designed to acquire this information. The aim was to assess: (i) any potential hemodynamic differences between the HP-Biplus prosthesis and the 'standard' bileaflet mechanical valves (SJM, ATS, Sorin Bicarbon and CarboMedics); and (ii) the incidence of postoperative complications and long-term mortality.

METHODS

The data from 242 patients (139 males, 103 females; mean age 58.4 +/- 14.0 years) who survived mitral or aortic valve surgery with mechanical bileaflet standard prostheses (SJM, ATS, Sorin Bicarbon or CarboMedics), between January 1985 and December 2005, were analyzed retrospectively. Evaluations were conducted consecutively with Doppler echocardiography, and compared with 35 patients (20 males, 15 females; mean age 52.2 +/- 12.8 years) who received an HP-Biplus prosthesis and underwent surgery between January 2000 and December 2005.

RESULTS

At seven years after surgery, actuarial survival was 40% for the HP-Biplus prosthesis and 84% for the 'standard' prostheses (p < 0.0001). The HP-Biplus prostheses had a higher rate of reoperations for aortic valves (15.2% versus 1.7%; p < 0.003, OR 10.2), a higher rate of prosthesis dysfunction (62.9% versus 7.8%; p < 0.00001, OR 25), and a higher rate of total events (72% versus 21.8%; p < 0.0001, OR 11).

CONCLUSION

The present study was the first to compare long-term results of the HP-Biplus prostheses with those obtained with 'standard' mechanical prostheses. Valve replacement with standard prostheses was shown to carry low morbidity and mortality (21.8%), whereas the HP-Biplus prosthesis showed high morbidity and mortality (92%). The data acquired may be very important when selecting prostheses with better hemodynamic characteristics, and show that the HP-Biplus prosthesis, in the authors' opinion, is not suitable for clinical use.

Selenium deficiency alters epithelial cell morphology and responses to influenza

It is unknown whether nutritional deficiencies affect the morphology and function of structural cells, such as epithelial cells, and modify the susceptibility to viral infections. We developed an in vitro system of differentiated human bronchial epithelial cells (BEC) grown either under selenium-adequate (Se+) or selenium-deficient (Se-) conditions, to determine whether selenium deficiency impairs host defense responses at the level of the epithelium. Se- BECs had normal SOD activity, but decreased activity of the selenium-dependent enzyme GPX1. Interestingly, catalase activity was also decreased in Se- BECs. Both Se- and Se+ BECs differentiated into a mucociliary epithelium; however, Se- BEC demonstrated increased mucus production and increased Muc5AC mRNA levels. This effect was also seen in Se+ BEC treated with 3-aminotriazole, an inhibitor of catalase activity, suggesting an association between catalase activity and mucus production. Both Se- and Se+ were infected with influenza A/Bangkok/1/79 and examined 24 h postinfection. Influenza-induced IL-6 production was greater while influenza-induced IP-10 production was lower in Se- BECs. In addition, influenza-induced apoptosis was greater in Se- BEC as compared to the Se+ BECs. These data demonstrate that selenium deficiency has a significant impact on the morphology and influenza-induced host defense responses in human airway epithelial cells.

Usefulness of Myocardial Contrast Echocardiography Early After Acute Myocardial Infarction

OBJECTIVES

(1) Evaluate wall motion and perfusion abnormalities after reperfusion therapy of the culprit lesion, (2) delineate the ability of myocardial contrast echocardiography (MCE) to evaluate the microvasculature after reperfusion, in order to distinguish between stunning and necrosis in the risk area.

METHODS

We analyzed 446 segments from 28 patients, 10 normal controls (160 segments), and 18 with a first AMI (286 segments). MCE was obtained with Optison and a two-dimensional echocardiography was performed at 3 months post acute myocardial infarction (AMI).

RESULTS

In the group with AMI, we analyzed 286 segments, of which 107 had wall motion abnormalities (WMA) related to the culprit artery. Two subgroups were identified: Group I with WMA and normal perfusion (50 segments, 47%) and Group II with WMA and perfusion defects (57 segments, 53%). According to the 2D echocardiogram at 3 months, they were further subdivided into: Group IA: with wall motion improvement (stunning): 18 segments, 36%, Group IB: without wall motion improvement: 32 segments, 64%, Group IIA: with wall motion improvement: 12 segments, 21%, Group IIB: without wall motion improvement (necrosis): 45 segments, 79%.

CONCLUSIONS

(1) The presence of myocardial perfusion in segments with WMA immediately after AMI reperfusion therapy predicts viability in most patients. Conversely, the lack of perfusion is not an absolute indicator of the presence of necrosis. (2) Perfusion defects allow to detect patients with thrombolysis in myocardial infarction (TIMI) 3 flow and "no-reflow" phenomenon who will not show improved wall motion in the 2D echocardiogram. However, some patients with initial no-reflow could have microvascular stunning and their regional contractile function will normalize after a recovery period.

Cinefluoroscopic assessment of mechanical disc prostheses: its value as a complementary method to echocardiography

BACKGROUND AND AIM OF THE STUDY

Many types of mechanical prostheses are used for heart valve replacement, but it is difficult to distinguish between them using transthoracic echocardiography. Hence, cinefluoroscopy complements the echocardiographic evaluation of cardiac prostheses. The aims of the present study were to: (i) describe the contribution of cinefluoroscopy in identifying different prostheses; (ii) compare gradients obtained by Doppler echocardiography with the opening angle of the discs assessed by cinefluoroscopy; and (iii) assess the ability of cinefluoroscopy to distinguish normal from dysfunctional prostheses.

METHODS

A total of 229 mechanical disc prostheses was prospectively evaluated with cinefluoroscopy. Eight prosthetic valves (six aortic, two mitral) were excluded due to the coexistence of severe left ventricular dysfunction. Thus, the final analysis comprised 221 prosthetic valves (146 aortic, 75 mitral).

RESULTS

Based on the characteristics of the ring and the discs, cinefluoroscopy identified 87 single-leaflet and 134 bileaflet prostheses. Disc motion allowed distinction to be made between normal and dysfunctional prostheses (opening angle: 74 +/- 13 degrees versus 49 +/- 18 degrees). Fluoroscopy could not define disc profile or the ring in 6% of aortic valves and in 26% of mitral prostheses. The technique could be used to identify the TriTechnologies and HP-Biplus valves, but could not provide data on prosthetic function due to radiolucency of the discs. Among the 146 aortic prostheses, Doppler echocardiography helped to identify 109 normal valves and 37 dysfunctional valves. Among 75 mitral prostheses, 54 normal and 21 dysfunctional prosthetic valves were identified. When both methods were correlated, the sensitivity, specificity and positive and negative predictive values of fluoroscopy to distinguish normal from malfunctioning prostheses were 83%, 80%, 89%, and 71%, respectively.

CONCLUSION

Each prosthesis type has radioscopic characteristics that allow its identification. Fluoroscopy permitted rapid and easy evaluation of mechanical prosthetic valve function, and in most cases allowed a distinction to be made between normal and dysfunctional prostheses. The presence of high gradients by Doppler echocardiography, with normal opening angles by fluoroscopy, and without pannus on transesophageal echocardiography, is indicative of patient-prosthesis mismatch. Fluoroscopy was superior to echocardiography in identifying disc motion, whilst Doppler study allowed the measurement of gradients and areas, and semiquantification of regurgitation. Thus, cinefluooscopy rapidly provides valuable information which is complementary to that obtained by echocardiography.

Prenatal and early postnatal environments are significant predictors of total immunoglobulin E concentration in Filipino adolescents

BACKGROUND

Recent evidence suggests that atopic disease may in part be mediated by fetal growth, as well as exposure to infectious disease early in life. Few studies have been able to evaluate these associations simultaneously, or to investigate prospectively the long-term effects of early environments while adequately controlling for potentially confounding variables.

OBJECTIVE

To examine how prenatal growth and infectious disease in infancy are related to total IgE production in adolescence.

METHODS

Ninety-nine adolescents (aged 14-15 years) were selected from a larger cohort study according to the following criteria: full-term birth, currently healthy, and small-for-gestational age (N=53) or appropriate-for-gestational age (N=46). Plasma total IgE was measured with ELISA, and analysed in relation to anthropometric, nutritional, and environmental quality data collected prospectively beginning in the third trimester prior to birth.

RESULTS

Each episode of infectious morbidity recorded at bimonthly intervals in the first 6 months of life was associated with a 0.12 log IU/mL reduction in total IgE in adolescence (P=0.004). Prenatal undernutrition was associated with increased adolescent IgE, but only under conditions of an unsanitary household environment (P=0.002). Each additional kilogram gained per month in the first 6 months of life was associated with an increase in adolescent IgE of 0.74 log IU/mL (P=0.03). Each quartile increase in weekly household income at the time of blood sampling was associated with a 0.10 log IU/mL reduction in total IgE (P=0.02).

CONCLUSION

Infectious disease in infancy, as well as interactions between prenatal and postnatal environments, appear to have long-term effects on adolescent total IgE production. Future research should investigate the mechanisms behind these effects, and their implications for symptoms of atopic disease.

Prenatal undernutrition, postnatal environments, and antibody response to vaccination in adolescence

BACKGROUND

Recently, researchers have considered the fetal and infant origins of several adult cardiovascular and metabolic diseases, but the implications of early events for immune function and infectious disease are unclear.

OBJECTIVE

We investigated the association between prenatal undernutrition and immunocompetence in adolescence and hypothesized that intrauterine growth retardation is associated with a lower likelihood of mounting an adequate antibody response later in life.

DESIGN

A subsample of one hundred three 14-15-y-olds was recruited from an ongoing longitudinal study in which data collection began while participants were in utero. A typhoid vaccine was given, and anti-typhoid antibodies were measured 2 wk and 3 mo later as a functional marker of immunocompetence. The likelihood of mounting an adequate antibody response was compared for adolescents who were small for gestational age or appropriate for gestational age at birth while controlling for a range of postnatal exposures.

RESULTS

The predicted probability of mounting a positive antibody response for adolescents who were prenatally and currently undernourished was 0.32, compared with probabilities of 0.49-0.70 for adequately nourished adolescents (P = 0.023). Diarrhea in the first year of life (P = 0.009) and fast weight gain during the first 6 mo (P = 0.003) were also associated with a higher probability of response.

CONCLUSIONS

These findings extend the concept of fetal and early infant programming of adult diseases to the immune system and suggest that early environments may have long-term implications for immunocompetence and infectious disease risk, particularly in developing countries.

Antioxidants and viral infections: host immune response and viral pathogenicity

Malnutrition has long been associated with increased susceptibility to infectious disease. The increase in severity from and susceptibility to infectious disease in malnourished hosts is thought to be the result of an impaired immune response. For example, malnutrition could influence the immune response by inducing a less effective ability to manage the challenge of an infectious disease. Work in our laboratory has demonstrated that not only is the host affected by the nutritional deficiency, but the invading pathogen is as well. Using a deficiency in selenium (Se) as a model system, mice deficient in Se were more susceptible to infection with coxsackievirus, as well as with influenza virus. Se-deficient mice develop myocarditis when infected with a normally benign strain of coxsackievirus. They also develop severe pneumonitis when infected with a mild strain of influenza virus. The immune system was altered in the Se-deficient animals, as was the viral pathogen itself. Sequencing of viral isolates recovered from Se-deficient mice demonstrated mutations in the viral genome of both coxsackievirus and influenza virus. These changes in the viral genome are associated with the increased pathogenesis of the virus. The antioxidant selenoenzyme, glutathione peroxidase-1, was found to be critically important, as glutathione peroxidase knockout mice developed myocarditis, similar to the Se-deficient mice, when infected with the benign strain of myocarditis. This work points to the importance of host nutrition in not only optimizing the host immune response, but also in preventing viral mutations which could increase the viral pathogenicity.

The role of oxidative stress in viral infections

Oxidative stress is implicated as a pathogenic factor in a number of viral infections. Our work has shown that nutritionally induced oxidative stress exacerbates the pathogenesis of coxsackievirus B3 (CVB3) infection in mice. Of particular note, mice fed on a diet deficient in antioxidants developed myocarditis when infected with a normally benign strain of CVB3. This change in virulence was found to be due to changes in the viral genome. Immune functions of the oxidatively stressed mice were also altered. Another example of the effect of oxidative stress on a viral pathogen took place in Cuba in the 1990s. An epidemic of optic and peripheral neuropathy in the population occurred that was associated with a lack of dietary antioxidants and with smoking (a pro-oxidant). A coxsackie-like virus was isolated from the cerebrospinal fluid from 84% of patients cultured. Thus, oxidative stress can have profound effects, not only on the host, but on the pathogen as well.

Prenatal undernutrition and postnatal growth are associated with adolescent thymic function

The fetal and early infant origins of a number of adult cardiovascular and metabolic diseases have received considerable attention, but the long-term consequences of early environments for human immune function have not been reported. We investigated the effects of pre- and postnatal environments on thymic hormone production in adolescents participating in an ongoing longitudinal study in the Philippines. Prospective data collected at birth, during y 1 of life, in childhood and in adolescence were used to predict plasma thymopoietin concentration in 14- to 15-y-old adolescents (n = 103). Thymopoietin concentration was compared for small-for-gestational-age and appropriate-for-gestational-age individuals while controlling for a range of postnatal exposures. Prenatal undernutrition was significantly associated with reduced thymopoietin production in interaction with the duration of exclusive breast-feeding (P = 0.006). Growth in length during y 1 of life was positively associated with adolescent thymopoietin production (P = 0.002). These associations remained significant after adjusting for a range of potentially confounding variables. These findings provide support for the importance of fetal and early infant programming of thymic function, and suggest that early environments may have long-term implications for immunocompetence and adult disease risk.

Micronutrients and host resistance to viral infection

Previous work in our laboratory demonstrated that a virus could undergo rapid mutation in a host deficient in Se, leading to a normally avirulent virus acquiring virulence due to genome changes. Once these mutations occur, even a host with adequate Se-nutriture is susceptible to the newly virulent virus. What influence does the deficiency in Se have on the immune response of the host? Infection with myocarditic strains of coxsackievirus induces an inflammatory response in the cardiac tissue. It is this immune response that induces the heart damage, rather than direct viral effects on the heart tissue. Chemokines are chemo-attractant molecules that are secreted during an infection in order to attract immune cells to the site of the injury, and have been found to be important for the development of coxsackievirus-induced myocarditis. We found that a deficiency in Se influences the expression of mRNA for the chemokine monocyte chemo-attractant protein-1, which may have implications for the development of myocarditis in the Se-deficient host. Expression of mRNA for interferon-gamma was also greatly decreased in the Se-deficient animal. Thus, a deficiency in Se can have profound effects on the host as well as on the virus itself. How the alteration of the immune response of the Se-deficient animal affects the development of the virulent genotype remains to be answered.

Host nutritional status and its effect on a viral pathogen

The nutritional status of the host has long been associated with both severity and susceptibility to infectious disease. The accepted model system proposes that inadequate nutrition impairs the functioning of the immune system, thus resulting in increased susceptibility to infection. However, current work suggests that not only can the nutritional status of the host affect the immune response, but it can also affect the viral pathogen. In a mouse model, a benign strain of coxsackievirus B3 became virulent and caused myocarditis in selenium- and vitamin E-deficient mice. This change in pathogenicity was due to mutations in the viral genome, which changed an avirulent virus into a virulent one. Once these mutations occurred, even mice with normal nutriture developed disease from the mutated virus. These results suggest that the oxidative stress status of the host can have a profound influence on a viral pathogen.

Nutritionally induced oxidative stress: effect on viral disease

It has long been known that the nutritional status of the host can influence both susceptibility to infectious disease and the severity of the disease if contracted. In studies of coxsackievirus infection and selenium deficiency in mice, we found that mice fed a selenium-deficient diet developed myocarditis, but mice fed a diet adequate in selenium did not. Similarly, mice fed a diet deficient in vitamin E developed myocarditis, but mice fed a diet with adequate vitamin E did not. The epidemic of optic and peripheral neuropathy that occurred in Cuba in the early 1990s provides another example of how the nutritional status of the host may affect the impact of a virus. Patients who developed neuropathy had lower blood concentrations of riboflavin, vitamin E, selenium, alpha- and beta-carotenes, and the carotenoid lycopene, which suggests that the disease was associated with an impairment of protective antioxidant pathways. After supplementation of the population with these nutrients, the disease began to subside. The nutritional status of the host can have a profound influence on a virus, so that a normally avirulent virus becomes virulent because of changes in the viral genome. Our studies suggest that outbreaks of disease attributed to a nutritional deficiency may actually result from infection by a virus that has become pathogenic by replicating in a nutritionally deficient host.

Contrasting effects of CCR5 and CCR2 deficiency in the pulmonary inflammatory response to influenza A virus

The immune response to influenza A virus is characterized by an influx of both macrophages and T lymphocytes into the lungs of the infected host, accompanied by induced expression of a number of CC chemokines. CC chemokine receptors CCR5 and CCR2 are both expressed on activated macrophages and T cells. We examined how the absence of these chemokine receptors would affect pulmonary chemokine expression and induced leukocyte recruitment by infecting CCR5-deficient mice and CCR2-deficient mice with a mouse-adapted strain of influenza A virus. CCR5(-/-) mice displayed increased mortality rates associated with acute, severe pneumonitis, whereas CCR2(-/-) mice were protected from the early pathological manifestations of influenza because of defective macrophage recruitment. This delay in macrophage accumulation in CCR2(-/-) mice caused a subsequent delay in T cell migration, which correlated with high pulmonary viral titers at early time points. Infected CCR5(-/-) mice and CCR2(-/-) mice both exhibited increased expression of the gene for MCP-1, the major ligand for CCR2(-/-) and a key regulator of induced macrophage migration. These studies illustrate the very different roles that CCR5 and CCR2 play in the macrophage response to influenza infection and demonstrate how defects in macrophage recruitment affect the normal development of the cell-mediated immune response.

Selenium and host defence towards viruses

The association between viral disease and nutrition has long been thought to be due to effects on the host immune system. This theory suggests that when a host is malnourished, the immune system is compromised, and thus increased susceptibility to viral infection will occur. However, the virus itself may also be affected by the nutritional status of the host. We have demonstrated that a normally-benign strain of coxsackievirus B3 (CVB3/0) becomes virulent in either Se-deficient or vitamin E-deficient mice. Although the deficient animals are immunosuppressed, the virus itself is also altered. Six nucleotide changes were found in the virus that replicated in the deficient mice, and once these mutations occurred, even mice with normal nutrition became susceptible to disease. Thus, the nutritional status of the host was able to transform an avirulent virus into a virulent one due to genomic changes in the virus. We believe that a common mechanism of oxidative stress is the underlying cause of the genetic changes. Both vitamin E and Se act as antioxidants, and benign virus inoculated into GSH peroxidase (EC 1.11.1.9)-knockout mice will also convert to virulence due to genomic changes. Our work points to the importance of host nutrition during a viral disease, not only from the perspective of the host, but from the perspective of the viral pathogen as well.

Flavonol glycosides from Eschscholtzia californica

The aqueous EtOH extract of aerial parts of Eschscholtzia californica Cham. yielded six flavonol 3-O-glycosides including two new compounds: quercetin 3-O-[alpha-rhamnopyranosyl-(1-4)-alpha-rhamnopyranosyl-(1-6)-beta- glucopyranoside] and isorhamnetin 3-O-[alpha-rhamnopyranosyl-(1-4)-alpha-rhamnopyranosyl-(1-6)-beta- glucopyranoside]. Their structures were established on the basis of spectroscopic studies.

Selenium and viral virulence

A mouse model of coxsackievirus-induced myocarditis is being used to investigate nutritional determinants of viral virulence. This approach was suggested by research carried out in China which showed that mice fed diets composed of low selenium ingredients from a Keshan disease area suffered more extensive heart damage when infected with a coxsackie B4 virus than infected mice fed the same diet but supplemented with selenium by esophageal intubation. Selenium deficiency in our mice increased the virulence of an already virulent strain of coxsackievirus B3 (CVB3/20) and also allowed conversion of a non-virulent strain (CVB3/0) to virulence. Such conversion of CVB3/0 was accompanied by a change in the viral genome to more closely match that of the virulent virus, CVB3/20. As far as the authors are aware, this is the first report of host nutrition influencing the genetic make-up of an invading pathogen. Nutritionists may need to consider this mechanism of increased viral virulence in order to gain a better understanding of diet/infection relationships.

Glutathione peroxidase protects mice from viral-induced myocarditis

Glutathione peroxidase 1 (GPX-1) is a selenium-dependent enzyme with antioxidant properties. Previous investigations determined that mice deficient in selenium developed myocarditis when infected with a benign strain of coxsackievirus B3 (CVB3/0). To determine whether this effect was mediated by GPX-1, mice with a disrupted Gpx1 gene (Gpx1-/-) were infected with CVB3/0. Gpx1-/- mice developed myocarditis after CVB3/0 infection, whereas infected wild-type mice (Gpx1+/+) were resistant. Sequencing of viruses recovered from Gpx1(-/-)-infected mice demonstrated seven nucleotide changes in the viral genome, of which three occurred at the G residue, the most easily oxidized base. No changes were found in virus isolated from Gpx1+/+ mice. These results demonstrate that GPX-1 provides protection against viral-induced damage in vivo due to mutations in the viral genome of a benign virus.

Dietary oxidative stress and the potentiation of viral infection

Oxidative stress is implicated in the pathogenesis of several viral infections, including hepatitis, influenza, and AIDS. Dietary oxidative stress due to either selenium or vitamin E deficiency increases cardiac damage in mice infected with a myocarditic strain of coxsackievirus B3. Such dietary oxidative stress also allows a normally benign (i.e., amyocarditic) coxsackievirus B3 to convert to virulence and cause heart damage. This conversion to virulence is due to a nucleotide sequence change in the genome of the benign virus, which then resembles more closely the nucleotide sequence of virulent strains. Although it has been known for many years that poor nutrition can affect host response to infection, this is the first report of host nutrition affecting the genetic sequence of a pathogen. Further research is needed to determine whether poor host nutrition plays any role in the emergence of new viral diseases via alterations in he genotype of an infectious agent.

Contribution to the quantitative and enantioselective determination of kavapyrones by high-performance liquid chromatography on ChiraSpher NT material

A simultaneous HPLC separation of the enantiomers of kavain, dihydrokavain, methysticin and dihydromethysticin, as well as the achiral dienolides yangonin and desmethoxyyangonin was carried out on a ChiraSpher NT column. For quantitative determinations, calibration curves with correlation coefficients between 0.9982 and 0.9996 were established for the genuine kavapyrones. Detection limits between 0.25 microg and 0.5 microg per injection were measured at 240 nm. The defined scopes of work corresponded with the different kavapyrone amounts, depending on growth factors of distinct plant locations. The precision of the method was verified by analysing a phytopharmacon with a nominal value of 40 mg kavapyrones per tablet. The evaluation revealed 39.62 mg per tablet by the sum of single calculated kavapyrones. Relative standard deviations between 1.06% and 2.39% were found for the compounds under investigation. The accuracy of the method was proved by a recovery of 99.7%. To simplify the determination of the total kavapyrone amount, response factors and correlation factors for (+)-dihydrokavain, (+)-methysticin, (+)-dihydromethysticin, yangonin and desmethoxyyangonin were calculated relative to (+)-kavain.

Rapid genomic evolution of a non-virulent coxsackievirus B3 in selenium-deficient mice

Keshan disease, an endemic cardiomyopathy in China, can be prevented with selenium (Se) supplementation. However, the seasonal and annual nature of the disease suggests that an infectious co-factor is required along with a deficiency in Se. Using a murine model of coxsackievirus B3 (CVB3)-induced myocarditis, Se-deficient mice were shown to be more susceptible to the cardiopathologic effects of the virus. In addition, a normal benign strain of CVB3 becomes virulent in Se-deficient mice. This change in virulence was shown to be due to point mutations in the viral genome. Although the mechanism of the viral mutation is not known, the oxidative stress status of the Se-deficient host may play a role, either by directly affecting the virus and/or affecting host immune defenses.

Increased virulence of coxsackievirus B3 in mice due to vitamin E or selenium deficiency

Nutrition has long been known to affect the ability of the host to respond to infectious disease. Widespread famines are often accompanied by increased morbidity and mortality due to infectious diseases. The currently accepted view of the relationship between nutrition of the host and its susceptibility to infectious disease is one of a direct relationship with host immune status. That is, if the nutritional status of the host is poor-due to either single or multiple nutrient deficiencies-then the functioning of the host immune system is compromised. This impairment of the immune response will lead to an increased susceptibility to infectious disease. Clearly, the immune response has been shown to be weakened by inadequate nutrition in many model systems and in human studies. However, what about the effect of host nutrition on the pathogen itself? Our laboratory has shown, using a mouse model of coxsackievirus-induced myocarditis, that a host deficiency in either selenium or vitamin E leads to a change in viral phenotype, such that an avirulent strain of the virus becomes virulent and a virulent strain becomes more virulent. The change in phenotype was shown to be due to point mutations in the viral genome. Once the mutations occur, the phenotype change is stable and can now be expressed even in mice of normal nutriture. Our results suggest that nutrition can affect not only the host, but the pathogen as well, and demonstrate a new model of relating host nutritional effects to viral pathogenesis.

Piper methysticum: enantiomeric separation of kavapyrones by high performance liquid chromatography

A simultaneous separation of the enantiomers of kawain, dihydrokawain, methysticin, and dihydromethysticin as well as the achiral dienolides yangonin and demethoxyyangonin was carried out on a ChiraSpher NT column. This HPLC method can be used for the investigation of the enantiomeric purity of plant material and herbal medicines. The influence of temperature and flow rate are discussed in respect to the chromatographic resolution of the enantiomers. All tested enolide racemates can be preparatively separated on ChiraSpher NT.

Interacting nutritional and infectious etiologies of Keshan disease. Insights from coxsackie virus B-induced myocarditis in mice deficient in selenium or vitamin E

In 1979, Chinese scientists reported that selenium had been linked to Keshan disease, an endemic juvenile cardiomyopathy found in China. However, certain epidemiological features of the disease could not be explained solely on the basis of inadequate selenium nutrition. Fluctuations in the seasonal incidence of the disease suggested involvement of an infectious agent. Indeed, a coxsackievirus B4 isolated from a Keshan disease victim caused more heart muscle damage when inoculated into selenium-deficient mice than when given to selenium-adequate mice. Those results led us to study the relationship of nutritional status to viral virulence. Coxsackievirus B3/0 (CVB3/0), did not cause disease when inoculated into mice fed adequate levels of Se and vitamin E. However, mice fed diets deficient in either Se or vitamin E developed heart lesions when infected with CVB3/0. To determine if the change in viral phenotype was maintained, we passaged virus isolated from Se-deficient hosts, designated as CVB3/0 Se-, back into Se-adequate hosts. The CVB3/0 Se- virus caused disease in Se-adequate mice. To determine if the phenotype change was due to changes in the viral genome, we sequenced viruses isolated from Se-deficient mice and compared them with the input CVB3/0 virus. Six point mutations differed between the parent strain and the recovered CVB3/0 Se- isolates. When the experiment was repeated using vitamin E-deficient mice, the same 6 point mutations were found. This is the first report of a specific host nutritional deficiency altering viral genotype. Keshan disease may be the result of several interacting causes including a dominant nutritional deficiency (selenium), other nutritional factors (vitamin E, polyunsaturated fatty acids), and an infectious agent (virus).

Requirement of MIP-1 alpha for an inflammatory response to viral infection

Macrophage inflammatory protein-1 alpha (MIP-1 alpha) is a chemokine that has pro-inflammatory and stem cell inhibitory activities in vitro. Its biologic role in vivo was examined in mice in which the gene encoding MIP-1 alpha had been disrupted. Homozygous MIP-1 alpha mutant (-/-) mice were resistant to Coxsackievirus-induced myocarditis seen in infected wild-type (+/+) mice. Influenza virus-infected -/- mice had reduced pneumonitis and delayed clearance of the virus compared with infected +/+ mice. The -/- mice had no overt hematopoietic abnormalities. These results demonstrate that MIP-1 alpha is an important mediator of virus-induced inflammation in vivo.

Rapid genomic evolution of a non-virulent coxsackievirus B3 in selenium-deficient mice results in selection of identical virulent isolates

Previous work from our laboratory demonstrated that selenium deficiency in the mouse allows a normally benign (amyocarditic) cloned and sequenced Coxackievirus to cause significant heart damage. Furthermore, Coxsackievirus recovered from the hearts of selenium-deficient mice inoculated into selenium-adequate mice still induced significant heart damage, suggesting that the amyocarditic Coxsackievirus had mutated to a virulent phenotype. Here we report that sequence analysis revealed six nucleotide changes between the virulent virus recovered from the selenium-deficient host and the avirulent input virus. These nucleotide changes are consistent with known differences in base composition between virulent and avirulent strains of Coxsackievirus. To the best of our knowledge, this is the first report of a specific nutritional deficiency driving changes in a viral genome, permitting an avirulent virus to acquire virulence due to genetic mutation.

Increased virulence of a human enterovirus (coxsackievirus B3) in selenium-deficient mice

Coxsackievirus B3 (CVB3/20)-induced myocarditic lesions occurred more quickly and were more severe and virus titers in heart and liver were higher in selenium (Se)-deficient than Se-adequate mice. NK cell activity and serum neutralizing antibody titers were similar in both Se-adequate and -deficient CVB3/20-infected mice; however, lymphocyte proliferation to both mitogen and antigen was decreased in Se-deficient mice. CVB3/20 isolated from Se-deficient donor mice and inoculated into Se-adequate recipient mice induced severe myocarditis. In contrast, CVB3/20 isolated from Se-adequate donor mice and inoculated into Se-adequate recipient mice induced only moderate myocarditis, similar to that caused by the original virus stock. Thus, the general population of CVB3/20 virions, as a consequence of replicating in an Se-deficient host, underwent a phenotypic change to increased virulence. These results have important implications for the emergence of virulent viruses.

Benign human enterovirus becomes virulent in selenium-deficient mice

Coxsackieviruses have been implicated as possible co-factors in the etiology of the selenium (Se)-responsive cardiomyopathy known as Keshan disease. Here we report that a cloned and sequenced amyocarditic coxsackievirus B3 (CVB3/0), which causes no pathology in the hearts of Se-adequate mice, induces extensive cardiac pathology in Se-deficient mice. CVB3/0 recovered from the hearts of Se-deficient mice inoculated into Se-adequate mice induced significant heart damage, suggesting mutation of the virus to a virulent genotype. We demonstrate the important role of host nutritional status in determining the severity of a viral infection.

Vitamin E deficiency intensifies the myocardial injury of coxsackievirus B3 infection of mice

Feeding a vitamin E-deficient diet increases pathology in hearts of mice infected with a myocarditic coxsackievirus B3 (CVB3/20). Hearts from infected mice fed a vitamin E-deficient diet rich in highly unsaturated fat (menhaden oil) exhibited more severe pathology than hearts from infected mice fed a vitamin E-deficient diet based largely on saturated fat (lard). Furthermore, a cloned and sequenced amyocarditic coxsackievirus B3 (CVB3/0), which caused little or no pathology in the hearts of vitamin E-supplemented mice, induced extensive cardiac pathology in vitamin E-deficient mice. In infected mice, both mitogen and antigen responses were depressed by vitamin E deficiency, although neutralizing antibody responses were unaffected. Natural killer cell responses were comparable in infected mice fed a lard-based diet with or without supplemented vitamin E. However, a menhaden oil-based diet, whether supplemented with vitamin E or not, significantly depressed natural killer cell activity in infected mice compared with mice fed the lard-based diet. Coxsackievirus B3/0 recovered from the heart of a vitamin E-deficient donor mouse, passaged one time onto HeLa cells, caused significant heart damage when passed back into vitamin E-supplemented recipient mice, demonstrating that the amyocarditic CVB3/0 had changed to a virulent phenotype. Enhanced virulence was also seen with CVB3/20 virus similarly passaged in a vitamin E-deficient donor. Our work demonstrates the important role of host nutritional antioxidant status in determining the severity of certain viral infections.

Comoviruses and enteroviruses share a T cell epitope

An in vitro murine T cell proliferation assay was used to determine whether an antigenic epitope(s) recognized by enterovirus-immune T cells is held in common between plant comoviruses and human enteroviruses. Splenocytes isolated from C3H/HeJ mice infected with coxsackievirus B3 (CVB3) proliferated in vitro not only against a variety of enterovirus (CVB2, CVB3, CVB6, CVA16, PV1) antigens, but against comovirus (CPMV, BPMV) antigens as well. Splenocytes from mice inoculated with bean pod mottle virus (BPMV) also proliferated in response to comoviral and enteroviral antigens in vitro. However, if the viral inocula were highly purified prior to inoculation, then the splenocyte response was generated only against the group used to inoculate, suggesting that the epitope shared between the comoviruses and the enteroviruses resided in the nonstructural region. B (nonstructural) and M (structural) genomic segments of CPMV were translated in rabbit reticulocyte lysates and used as in vitro antigens. Splenocytes from mice inoculated with live CVB3 proliferated in response to the B-RNA-encoded but not the M-RNA-encoded polypeptides, confirming the nonstructural coding region location of the common epitope. Comparison of predicted amino acid sequences in the nonstructural coding regions of the comoviruses and picornaviruses suggested a potentially immunogenic linear epitope in protein 2C. The consensus peptide LEEKGI was synthezized and shown to be immunogenic for both BPMV- and CVB3-immune splenocytes.

Progress and challenges in the pathological diagnosis of myocarditis

The pathological diagnosis of myocarditis rests on well-described histopathological criteria. Appreciation for the disease-specific sensitivity of the endomyocardial biopsy, as well as the phenotypical and functional nature of inflammatory infiltrates, will enhance the clinical utility of the biopsy technique. New information regarding the role of enteroviruses in immunological sensitization and the study of enteroviruses in murine models and human patients are fostering new perspectives and routes of investigation of appropriate therapeutic interventions for myocarditis.

Echovirus 22 is an atypical enterovirus

Although echovirus 22 (EV22) is classified as an enterovirus in the family Picornaviridae, it is atypical of the enterovirus paradigm, typified by the polioviruses and the coxsackie B viruses. cDNA reverse transcribed from coxsackievirus B3 (CVB3) RNA does not hybridize to genomic RNA of EV22, and conversely, cDNA made to EV22 does not hybridize to CVB3 genomic RNA or to molecular clones of CVB3 or poliovirus type 1. EV22 cDNA does not hybridize to viral RNA of encephalomyocarditis virus or to a molecular clone of Theiler's murine encephalomyelitis virus, members of the cardiovirus genus. The genomic RNA of EV22 cannot be detected by the polymerase chain reaction using generic enteroviral primers. EV22 does not shut off host cell protein synthesis, and the RNA of EV22 is efficiently translated in vitro in rabbit reticulocyte lysates. Murine enterovirus-immune T cells recognize and proliferate against EV22 as an antigen in vitro, demonstrating that EV22 shares an epitope(s) common to enteroviruses but not found among other picornaviruses.

A molecular and serologic evaluation of enteroviral involvement in human myocarditis

Murine coxsackie B virus infection models of myocarditis and numerous human serologic studies associating elevated enterovirus-specific IgM titers with the clinical diagnosis of myocarditis have been used to support an etiologic role for enteroviruses in human myocarditis. Of the human enteroviruses, coxsackie B viruses (CVB) are the enterovirus group most commonly associated with the human disease. While hybridization probes exist to detect most, if not all, human enteroviruses, no probe capable of specifically detecting an enteroviral group (such as the CVB) to the exclusion of all others has been described to date. Thus, to test the hypothesis that enteroviral involvement in human myocarditis is commonplace, we examined a case series of human myocarditic heart tissues for enteroviruses by in situ hybridization using a generic enterovirus probe. These results were then compared with CVB-specific IgM levels in the cognate patient sera. Comparison of the hybridization data with the CVB-specific IgM levels in the cognate sera yielded no valid correlation between the detection of enteroviral RNA and specificity of CVB identification in any patient. The data are consistent with common enterovirus infections in humans and a possible etiologic role in myocarditis but do not support a specific etiologic role for CVB in this study group.

Secondary enterovirus infection in the murine model of myocarditis. Pathologic and immunologic aspects

Enteroviruses are implicated as etiologic agents in the inflammatory diseases myocarditis and polymyositis. In this report, we show that a previous enterovirus exposure in mice can influence development of myocardial inflammation with a second enteroviral exposure. Inoculation of 25-day-old male C3H/HeJ mice with 10(3) or 10(5) plaque-forming units (PFU) of infectious or ultra violet (UV)-inactivated coxsackievirus B2 (CVB2), followed by inoculation 28 days later with 10(5) PFU of a myocarditic variant of coxsackievirus B3 (CVB3-m) results in more intense myocardial inflammation and injury than is seen in age-matched mice inoculated with CVB3-m alone. More severe disease occurs with the lower primary dose of CVB2. Neutralizing antibody to CVB2 is detected early after primary inoculation and neutralizing antibody to CVB3 is first detected 5 days after secondary inoculation. In vitro proliferation of splenocytes from mice inoculated with one or both viruses occurs in response to both CVB2 and CVB3 antigens. We recently demonstrated that murine T cells are capable of recognizing an enterovirus group antigen. Thus cell-mediated immune responses to a conserved antigenic epitope(s) among the enteroviruses may be involved in the exacerbation of myocardial inflammatory disease during a second enterovirus infection. The secondary infection model described here may more accurately mirror virus-induced myocarditis in the human population because the majority of adults have been exposed to several enteroviruses before induction of disease.

Murine cell-mediated immune response recognizes an enterovirus group-specific antigen(s)

Splenocytes taken from mice inoculated with coxsackievirus B3 (CVB3) (Nancy) developed an in vitro proliferative response against CVB3 antigen. This response could not be detected earlier than 8 days postinoculation but could be detected up to 28 days after exposure to CB3. CVB3-sensitized splenocytes responded not only to the CVB3 antigen but to other enteroviruses as well. This response was found to be enterovirus specific in that no response was detected to a non-enteroviral picornavirus, encephalomyocarditis virus, or to an unrelated influenza virus. The generation of a splenocyte population capable of responding to an enterovirus group antigen(s) was not limited to inoculation of mice with CVB3, as similar responses were generated when mice were inoculated with CVB2. Cell subset depletions revealed that the major cell type responding to the enterovirus group antigen(s) was the CD4+ T cell. Current evidence suggests that the group antigen(s) resides in the structural proteins of the virus, since spleen cells from mice inoculated with a UV-inactivated, highly purified preparation of CVB3 virions also responded in vitro against enteroviral antigens.

Regulation of lymphokine response during reinfection by influenza virus. Production of a factor that inhibits lymphokine activity

Mononuclear cells, obtained from the spleens and lungs of influenza virus-seropositive C57BL/6 mice at 2 to 4 days after re-infection with homologous virus (strain A/Bangkok/1/79), produced a low m.w. factor in vitro that prevents the biologic expression, but not production, of the lymphokine, leukocyte migration inhibition factor (LIF). The low m.w. factor inhibited LIF activity without destroying the LIF molecule inasmuch as simple dialysis restored lymphokine activity to culture supernatants. Production of the low m.w. factor was observed from 2 to 4 days after re-infection, at which time the delayed-type hypersensitivity response to viral Ag was suppressed. In contrast, LIF was produced by splenocytes and lung mononuclear cells obtained at all times tested after re-infection (from 2 to 30 days). Production of the low m.w. factor required re-infection of influenza A virus-seropositive mice with type A virus; re-infection with influenza B virus failed to induce production. Ag specificity was also required in vitro for splenocytes to produce the factor; cells from type A virus-re-infected mice required type A Ag stimulation. Cell depletion studies with mAb plus C revealed that macrophages and T cells along with Ag stimulation were required for factor production by spleen cells. However, mononuclear cells obtained within 4 days from the lungs of re-infected mice did not require in vitro Ag stimulation for production of the low m.w. factor, and factor production was dependent upon the presence of CD4+ (L3T4) cells in the culture. Fractionation of culture supernatants over a Sephadex G-50 column indicated that the factor had a molecular mass of 2 to 3 kDa, and by FPLC chromatofocusing over a Mono P column, the factor eluted at a pH of approximately 8.2. Thus, re-exposure of influenza virus-seropositive mice to homologous virus resulted in the production of a low m.w. factor that prevented the biologic expression of LIF, but not its production. Lymphokines are an important component of the delayed-type hypersensitivity response; the presence of mononuclear cells secreting a low m.w. factor and LIF concomitantly at the site of virus replication (lungs) and the capacity of the factor to block the biologic expression of LIF in vitro suggest that the factor may have a role in the regulation of a delayed-type hypersensitivity response in vivo during re-infection.