Host-parasite biology in the real world: the field voles of Kielder.

Research on the interactions between the field voles (Microtus agrestis) of Kielder Forest and their natural parasites dates back to the 1930s. These early studies were primarily concerned with understanding how parasites shape the characteristic cyclic population dynamics of their hosts. However, since the early 2000s, research on the Kielder field voles has expanded considerably and the system has now been utilized for the study of host-parasite biology across many levels, including genetics, evolutionary ecology, immunology and epidemiology. The Kielder field voles therefore represent one of the most intensely and broadly studied natural host-parasite systems, bridging theoretical and empirical approaches to better understand the biology of infectious disease in the real world. This article synthesizes the body of work published on this system and summarizes some important insights and general messages provided by the integrated and multidisciplinary study of host-parasite interactions in the natural environment.

Wild rodents as a model to discover genes and pathways underlying natural variation in infectious disease susceptibility.

Individuals vary in their susceptibility to infectious disease, and it is now well established that host genetic factors form a major component of this variation. The discovery of genes underlying susceptibility has the potential to lead to improved disease control, through the identification and management of vulnerable individuals and the discovery of novel therapeutic targets. Laboratory rodents have proved invaluable for ascertaining the function of genes involved in immunity to infection. However, these captive animals experience conditions very different to the natural environment, lacking the genetic diversity and environmental pressures characteristic of natural populations, including those of humans. It has therefore often proved difficult to translate basic laboratory research to the real world. In order to further our understanding of the genetic basis of infectious disease resistance, and the evolutionary forces that drive variation in susceptibility, we propose that genetic research traditionally conducted on laboratory animals is expanded to the more ecologically valid arena of natural populations. In this article, we highlight the potential of using wild rodents as a new resource for biomedical research, to link the functional genetic knowledge gained from laboratory rodents with the variation in infectious disease susceptibility observed in humans and other natural populations.

Differences in HIV risk behavior of injection drug users in New York City by health care setting.

The purpose of this study is to examine the HIV risk behaviors and demographic characteristics of injection drug users (IDUs) by type of health care setting, which can inform development of tailored structural interventions to increase access to HIV prevention and medical treatment services. IDU syringe customers were recruited from pharmacies as part of the "Pharmacist As Resources Making Links to Community Services" (PHARM-Link) study, a randomized community-based intervention in New York City (NYC) aimed at connecting IDUs to HIV prevention, medical, and social services. An ACASI survey ascertained demographics, risk behavior, health-care utilization, and location where health care services were received in the past year. Data were analyzed using logistic regression. Of 602 participants, 34% reported receiving health care at a community clinic, 46% a private medical office, 15% a mobile medical unit, and 59% an emergency room (ER). After adjustment, participants who attended a community clinic were significantly more likely to have health insurance, report syringe sharing, and be HIV positive. Whites, nondaily injectors, insured, and higher income IDUs were more likely to attend a private medical office. Participants who recently used a case manager and had multiple sexual partners were more likely to use a mobile medical unit. ER attendees were more likely to be homeless and report recent drug treatment use. These findings show that IDU demographics and risk behaviors differ by health care setting, suggesting that risk reduction interventions should be tailored to health care settings. Specifically, these data suggest that community clinics and mobile medical units serve high-risk IDUs, highlighting the need for more research to develop and test innovative prevention and care programs within these settings.

Race/ethnic differences in bone mineral density in men.

UNLABELLED: The epidemiology of osteoporosis in male and minority populations is understudied. We compared BMD in 1,209 Black, Hispanic, and White men. Black men exhibited higher BMD than Hispanic or White men. Age-related BMD decreases were greatest among Hispanic men. Results may help explain variation in hip fracture rates by race/ethnicity. INTRODUCTION: The epidemiology of osteoporosis in male and minority populations is understudied. To address this concern, we conducted a study of skeletal health in a diverse population of adult males. METHODS: A total of 367 Black, 401 Hispanic, and 451 White men aged 30-79 years were randomly sampled from Boston, MA. Bone densitometry (bone area (BA), bone mineral content (BMC), and bone mineral density (BMD)) at the whole body, hip, lumbar spine, and forearm was performed. Multiple regression analyses on 1,209 men with available data were used to describe race/ethnic group-specific means (height- and age-adjusted) and age trends (height-adjusted) in BMC, BA, and BMD. Results were weighted to represent the Boston male population aged 30-79 years. RESULTS: Black men had greater BMC and BMD than Hispanic or White men. Femoral neck BMD was 5.6% and 13.3% higher in Black men than in Hispanic and White men, respectively. Differences between Hispanic and White subjects were restricted to the hip. Age-related declines in BMC and BMD were significantly steeper among Hispanic than Black or White men. CONCLUSIONS: Differences in BMC and BMD could explain variation in fracture rates among Black, Hispanic, and White men. The steeper age-related BMD decline in Hispanic men is of particular concern.

Contribution of proton-translocating proteins to the virulence of Salmonella enterica serovars Typhimurium, Gallinarum, and Dublin in chickens and mice.

We investigated the attenuating effects of a range of respiratory chain mutations in three Salmonella serovars which might be used in the development of live vaccines. We tested mutations in nuoG, cydA, cyoA, atpB, and atpH in three serovars of Salmonella enterica: Typhimurium, Dublin, and Gallinarum. All three serovars were assessed for attenuation in their relevant virulence assays of typhoid-like infections. Serovar Typhimurium was assessed in 1-day-old chickens and the mouse. Serovar Gallinarum 9 was assessed in 3-week-old chickens, and serovar Dublin was assessed in 6-week-old mice. Our data show variation in attenuation for the nuoG, cydA, and cyoA mutations within the different serovar-host combinations. However, mutations in atpB and atpH were highly attenuating for all three serovars in the various virulence assays. Further investigation of the mutations in the atp operon showed that the bacteria were less invasive in vivo, showing reduced in vitro survival within phagocytic cells and reduced acid tolerance. We present data showing that this reduced acid tolerance is due to an inability to adapt to conditions rather than a general sensitivity to reduced pH. The data support the targeting of respiratory components for the production of live vaccines and suggest that mutations in the atp operon provide suitable candidates for broad-spectrum attenuation of a range of Salmonella serovars.

Construction and characterization of genetically defined aro omp mutants of enterotoxigenic Escherichia coli and preliminary studies of safety and immunogenicity in humans.

Enterotoxigenic Escherichia coli (ETEC) is a leading cause of diarrhea in travelers to countries where the disease is endemic and causes a major disease burden in the indigenous population, particularly children. We describe here the generation and preclinical characterization of candidate strains of ETEC which are intended to provide the basis of a live attenuated oral vaccine to prevent this disease. It has been shown previously that a spontaneously arising toxin-negative variant ETEC strain, E1392/75-2A, could confer 75% protection against challenge when administered to volunteers. Unfortunately this strain induced mild diarrhea in 15% of recipients. To eliminate the unacceptable reactogenicity of strain E1392/75-2A, it was further attenuated by introducing three different combinations of defined deletion mutations into the chromosome. A mouse intranasal model of immunization was developed and used to show that all of the strains were immunogenic. Immune responses against colonization factor antigens (CFAs) were particularly strong when the bacterial inocula were grown on "CFA agar," which induces strong expression of these antigens. Two of the strains were selected for a phase I dose escalation safety study with healthy adult volunteers. Freshly grown organisms were harvested from CFA agar plates and administered to volunteers as a suspension containing from 5 x 10(7) to 5 x 10(9) CFU. The vaccine was well tolerated at all doses and induced significant immune responses in all recipients at the highest dose of either strain. The results provide the basis for further clinical evaluation of these vaccine candidates.

Vaccination for control of Salmonella in poultry.

Salmonella spp. are facultative intracellular pathogens causing localised or systemic infections, in addition to a chronic asymptomatic carrier state. They are of worldwide economic and public health significance. In poultry, which represent important sources of cheap protein throughout the world, fowl typhoid and pullorum disease continue to cause economic losses in those parts of the world where the poultry industries are continuing to intensify and where open sided housing is common. A number of serotypes that cause human gastro-enteritis are also increasing. The costs or impracticality of improvements in hygiene and management together with the increasing problems of antibiotic resistance suggest that vaccination in poultry will become more attractive as an adjunct to existing control measures. However, our understandings of the immunology of Salmonella infections in poultry is rudimentary and much poorer than that of equivalent infections in mice and live vaccine development for poultry has therefore been largely empirical. In addition to the killed Salmonella vaccines which have been used over the past few years with variable efficacy, a number of live vaccines have become available and some new vaccines will appear on the market over the next few years. These new vaccines should fulfil the criteria of efficacy, safety and compatibility with existing systems for monitoring infection before they are released on to a mass market. In this review we attempt to summarise the current understanding of Salmonella immunology in poultry together with the progress that has been made in poultry vaccine development.

Complement processing and immunoglobulin binding to Neisseria gonorrhoeae determined in vitro simulates in vivo effects.

Local inflammation elicited by Neisseria gonorrhoeae correlates closely with sensitivity to killing by normal human serum. Serum-sensitive (SS) isolates are rendered resistant in vitro by lipooligosaccharide sialylation. Differences in C3b processing on N. gonorrhoeae in vitro were found to match findings at the cervical level in vivo. Nonsialylated SS gonococci bound 5-fold more C3b than did stably serum-resistant (SR) gonococci; most was processed to iC3b, yet significant C3b persisted. Sialylated SS gonococci bound 4-fold less total C3 antigen than did SR gonococci, which was promptly converted to iC3b. C3b bound later on stably SR gonococci but again was processed swiftly to iC3b. In vivo, the iC3b/C3 ratio of SS isolates more closely resembled nonsialylated SS isolates in vitro, implying heterogeneous sialylation or desialylation in vivo. In vitro, total IgM bound was unchanged by sialylation of SS isolates, but total C4 bound decreased by 75%, suggesting that sialylation may indirectly regulate the classical complement pathway.

Protection of chickens against experimental fowl typhoid using a nuoG mutant of Salmonella serotype Gallinarum.

A nuoG mutation in NADH dehydrogenase I was introduced into a virulent strain of Salmonella serotype Gallinarum, the causative agent of fowl typhoid, using gene replacement with a nuoG open reading frame inactivated by insertion of DNA encoding a kanamycin resistance determinant. The S. Gallinarum nuoG mutant, named SG9NGK, was highly attenuated in chickens. SG9NGK colonized the caeca of chickens less efficiently than the S. Gallinarum parental strain, was less invasive and showed no evidence of multiplication in the liver or spleen. Using a single oral immunization with live bacteria SG9NGK reduced mortality in 2-week-old chickens following challenge with virulent S. Gallinarum from 75% to less than 8%.

Identification of Salmonella typhimurium genes required for colonization of the chicken alimentary tract and for virulence in newly hatched chicks.

From a collection of 2,800 Tn5-TC1 transposon mutants of Salmonella typhimurium F98, 18 that showed reduced intestinal colonization of 3-week-old chicks were identified. The sites of transposon insertion were determined for most of the mutants and included insertions in the lipopolysaccharide biosynthesis genes rfaK, rfaY, rfbK, and rfbB and the genes dksA, clpB, hupA, and sipC. In addition, identification was made of an insertion into a novel gene that encodes a protein showing similarity to the IIC component of the mannose class of phosphoenolpyruvate-carbohydrate phosphotransferase systems, which we putatively called ptsC. Transduction of most of the transposon mutations to a fresh S. typhimurium F98 genetic background and construction of defined mutations in the rfbK, dksA, hupA, sipC, and ptsC genes of S. typhimurium F98 supported the role in colonization of all but the pts locus. The virulence of the rfbK, dksA, hupA, sipC, and ptsC defined mutants and clpB and rfaY transductants in 1-day-old chicks was tested. All but the ptsC and rfaY mutants were attenuated for virulence. A number of other phenotypes associated with some of the mutations are described.

The utility of portable dual-energy X-ray absorptiometry of the wrist in patients referred to a bone health clinic: a pilot study.

Fifty white female patients referred to a bone health care clinic were studied. Patients with a history of fracture were excluded. At the time of hip and spine dual-energy X-ray absorptiometry (DXA), those willing underwent portable dual-energy X-ray absorptiometry (pDXA) of the wrist. The mean age of the patients was 57 yr. Bone mineral density (BMD) assessment was performed on each patient at four different sites: posterior-anterior lumbar spine, nondominant hip, the distal radius and ulna, and the proximal radius and ulna of the nondominant arm. Comparison of the pDXA results with that of the conventional DXA results showed the highest correlation between pDXA of the distal radius and ulna (DR + U) and the DXA of the femoral neck and lumbar spine. By defining a pDXA (DR + U) T-score

Oncogenic osteomalacia: clinical presentation, densitometric findings, and response to therapy.

A 72-yr-old white female who had previously enjoyed excellent health presented with global bone and muscle pain, and chronic fatigue. Her evaluation revealed an increased sedimentation rate and mild anemia, and a diagnosis of polymyalgia rheumatica was made. Prednisone therapy was of little benefit. A laboratory evaluation revealed mild hypocalcemia, marked hypophosphatemia, elevated alkaline phosphatase, normal 25- hydroxyvitamin D, and undectable 1,25-dihydroxyvitamin D. A diagnosis of oncogenic osteomalacia was made and the patient received calcitriol and neutraphos therapy. The patient's initial bone density by dual energy X-ray absorptiometry of the lumbar spine was 0.847 g/cm2 (T score -1.96) and of the femoral neck was 0.669 gm/cm2 (T score -2.89). After 40 mo of treatment with calcitriol and neutraphos, the bone mineral density of the lumbar spine and hip rose dramatically by 47.8 and 59.1%, respectively. Although oncogenic osteomalacia is a very rare metabolic bone disease, its recognition and appropriate treatment can have a dramatic effect not only on the bone mineral density of the patient, but also on the patient's general health and feeling of well-being.

Influence of genes encoding proton-translocating enzymes on suppression of Salmonella typhimurium growth and colonization.

Twenty-four-hour-old, aerobically grown, Luria-Bertani broth cultures of Salmonella typhimurium F98 suppressed the growth of a spectinomycin-resistant (Spcr) derivative of the same strain inoculated at 10(3) CFU ml(-1). This growth suppression is genus specific and RpoS independent, and it is not solely a result of nutrient depletion (P. A. Barrow, M. A. Lovell, and L. Zhang-Barber, J. Bacteriol. 178:3072-3076, 1996). Mutations in three genes are shown here to significantly reduce growth suppression under these conditions. The mutations were located in the nuo, cyd, and unc operons, which code for the NADH dehydrogenase I, cytochrome d oxidase, and F0F1 proton-translocating ATPase complexes, respectively. When cultures were grown under strictly anaerobic conditions, only the unc mutant did not suppress growth. Prior colonization of the alimentary tract of newly hatched chickens with the S. typhimurium F98 wild type or nuo or cyd mutants suppressed colonization by an S. typhimurium F98 Spcr derivative inoculated 24 h later. In contrast, the S. typhimurium unc mutant did not suppress colonization. The nuo and unc mutants showed poorer growth on certain carbon sources. The data support the hypothesis that growth suppression operates because of the absence of a utilizable carbon source or electron acceptor.

Extracellular DNA from Serpulina hyodysenteriae consists of 6.5 kbp random fragments of chromosomal DNA.

Preparations of chromosomal DNA from a number of Serpulina hyodysenteriae strains have shown, using agarose gel electrophoresis, the presence of an additional band with a mobility similar to that of a 6.5 kbp linear DNA fragment. Analysis showed that this is not a plasmid but rather a form of extracellular DNA like that observed for Gram-negative bacteria. However, unlike the extracellular DNA from Gram-negative bacteria, which showed a similar band profile to that of the DNA from whole cells, that from S. hyodysenteriae consisted primarily of fragments of a fixed 6.5 kbp.

Distribution of the smpA gene from Serpulina hyodysenteriae among intestinal spirochaetes.

Forty intestinal spirochaete strains were investigated for nucleotide sequences related to the smpA locus from Serpulina hyodysenteriae by Southern hybridization of chromosomal DNA using the smpA locus from S. hyodysenteriae strain P18A as a probe and by PCR using primers internal to the smpA gene. The intensity of the hybridization signal at high stringency and positive PCR results suggested that 12 S. hyodysenteriae strains possessed a similar nucleotide sequence. PCR was negative for another 12 S. hyodysenteriae strains and the hybridization signal obtained from 11 of these was weak and one was negative. All S. hyodysenteriae strains hybridized under low stringency conditions. These results indicated that there is variation among the smpA loci of S. hyodysenteriae strains. Among seven strains of S. innocens, and the proposed species 'S. intermedius' and 'S. murdochii', hybridization was weak and no PCR products were obtained, suggesting that these species have sequences related to, but divergent from, the smpA sequences of strains of S. hyodysenteriae. Both gene probe hybridization and PCR analysis of nine strains of the proposed new genus 'Anguillina', including isolates from pigs and humans, gave negative results.

Nucleotide sequence within Tn3926 confirms this as a Tn21-like transposable element and provides evidence for the origin of the mer operon carried by plasmid pKLH2.

The DNA sequence of the resolvase gene, resolution sites, and the region between the transposition functions and the end of the mercury resistance operon of the bacterial transposon, Tn3926, is presented. The sequence of Tn3926 upstream of the resolution sites is homologous to that bordering the 11.2-kb insert of Tn21, supporting the idea that this insert transposed into a progenitor of Tn3926. This region of Tn3926 also shows 97.0% identity to the mercury-resistant determinant of the plasmid, pKLH2, suggesting that this plasmid once harbored a close relative of Tn3926. It is proposed that the mercury resistance operon of Tn3926 will have a structure very similar to that found on pKLH2.

Reproducibility of the catecholamine response to serial exercise testing in normals.

Plasma norepinephrine (NE) and epinephrine (E) increase with exercise but the reproducibility of their response to short-term serial exercise testing has not been established. Therefore, NE and E were measured at rest, 6 minutes, peak exercise, and 5 minutes postexercise in 10 normal subjects undergoing three identical exercise tolerance tests within 4-13 days. Norepinephrine and E were also measured in tests 2 and 3 at the time equivalent to the peak exercise duration in test 1 (peak--equivalent). Exercise duration increased slightly from test 1 (15.6 +/- 0.7 min) to test 2 (16.5 +/- 0.5 min; p = 0.07) but no further on test 3 (16.2 +/- 0.9 min). Norepinephrine and E did not differ across the three tests at rest, 6 minutes, peak test or posttest, but a significant decrease in both NE and E was seen at peak-equivalent by test 3 (p less than 0.05). Heart rate decreased across the three tests at 3, 6, 9, and 12 minutes (p less than 0.02 for each) and peak equivalent (p less than 0.005) but was unchanged at rest, peak exercise and postexercise. Thus, plasma catecholamines and heart rate decrease at high levels of exercise with repeated, short-term exercise testing, possibly due to familiarity with the protocol. These results suggest that control groups are important when measuring the effects of short-term pharmacologic intervention by serial exercise tests.