Mouse thymic virus (MTLV). A mammalian herpesvirus cytolytic for CD4+ (L3T4+) T lymphocytes.

Mouse thymic virus (MTLV; ICTV designation murid herpesvirus 3) infects developing T lymphocytes of neonatal mice, causing thymic necrosis and acute immunosuppression. Infected animals shed virus indefinitely. In the present report, two-color flow cytometric analysis of T lymphocyte subpopulations defined by the markers CD4 (L3T4) and CD8 (Lyt-2) was used to determine whether MTLV was lytic for a specific thymocyte population. At peak necrosis (8-11 d after infection), numbers of CD4+8+ cells in the thymus were reduced by 80% or more as compared with controls, and CD4+8- cells were reduced by greater than 98%. The major survivors were CD4-8+ and CD4-8- lymphocytes. These data indicate that the CD4 bearing lymphocyte is a primary target for cytolysis during MTLV infection. Possible parallels between MTLV and a newly described lymphotropic human herpesvirus, human herpesvirus 6 (HHV-6/HBLV), are also suggested.

Macrophage functions in beige (Chédiak-Higashi syndrome) mice.

Beige (C57BL/6J-bgj/bgj) mice are the murine counterpart of the Chédiak-Higashi syndrome, exhibiting abnormal lysosomes in phagocytes. These mice, however, responded normally to Corynebacterium parvum killed bacterial vaccine with splenomegaly and an increase in peritoneal macrophages. The C. parvum-elicited macrophages showed normal immunoglobulin G Fc- and C3b-mediated rosettes and phagocytosis. The antitumor action of the macrophages was assessed against the Lewis lung carcinoma, a tumor that is sensitive to inhibition by activated macrophages both in vitro and in vivo. The elicited macrophages from beige mice showed delays in vitro in cytostatic and cytotoxic activity against the tumor cells, as compared with C57BL/6J-+/+ control mice. The early delays in activity disappeared after 12 to 24 hr, when antitumor activity was similar to that exhibited by C. parvum-elicited macrophages of the C57BL/6J-+/+ mice. These delays in antitumor activity of beige mouse macrophages may be analogous to the delays observed in the bactericidal activity of beige mouse granulocytes. The ultimate antitumor activity, however, was comparable in beige and +/+ C. parvum-elicited macrophage. Moreover, the resistance of mice in vivo to the Lewis lung tumor was not markedly impaired. The growth of the primary tumors and the mean times to death of the tumor-bearing animals of both strains were similar.

Early image acquisition after administration of indium-111 platelets in clinically suspected deep venous thrombosis.

Indium-111 platelet scintigraphy accurately detects acute deep venous thrombosis in asymptomatic high-risk patients and may be used as a surveillance test. However, its value in symptomatic patients and its accuracy early after platelet injection are not satisfactorily established. The latter is important for timely institution of therapy. Accordingly, 65 patients (67 limbs) with suspected deep venous thrombosis (symptom duration 8 +/- 10 days, mean +/- standard deviation) were prospectively studied with platelet scintigraphy and contrast venography. Platelets were labeled with 405 +/- 101 mCi indium-111 oxine. The labeling efficiency was 80 +/- 10%. All images were acquired within 120 minutes after intravenous administration of the platelet suspension. Both platelet scintigraphy and venography were interpreted independently by 2 blinded observers (for each technique). Five separate analyses were performed. Each scintigraphic reader was compared to each venographic reader. A fifth analysis--consisting of readings with blinded agreement of both readings of the platelet scans and both readings of the venograms--was performed. Interobserver agreement was 92% for venography and 79% for scintigraphy. Excluding anticoagulated patients, the sensitivity of platelet scintigraphy was between 38 and 46% and the specificity was between 92 and 100%. Thus, early imaging of labeled platelets for the diagnosis of symptomatic deep venous thrombosis carries a high specificity but a much lower sensitivity. It is speculated that the low sensitivity is related to the inactivity of the thrombus. This may suggest that early imaging will only be useful in patients whose symptoms are of recent onset.

Identification and evaluation of new primer sets for the detection of lentivirus proviral DNA.

We have developed sets of degenerate oligonucleotides designed to detect pol gene sequences from any member of the lentivirus subfamily when used as primers in amplification techniques such as the polymerase chain reaction (PCR). This pan-lentivirus-specific primer set (PLSPS) consists of primers, LV1, LV2, and LV3, based on conserved regions common to lentiviruses only. Our protocol is based on primary amplification with LV1 and LV2 followed by secondary amplification with a nested primer set based on the YM/VDD motif found in all reverse transcriptases (or "DDMY," in the opposite direction), and LV3, a block of lentivirus homology nested just downstream of LV1. PLSPS-PCR analysis of DNA from cells infected with HIV-1, HIV-2, SIVmac239, BIV, visna, EIAV, CAEV, OPPV, or FIV resulted in the amplification of appropriately sized products. Sequence analysis of the LV1/2 products, cloned into pBluescript (pBS), indicated that at least 20% (most often, > 80%) contained the predicted lentivirus pol sequence. Greater than 95% of the LV3/DDMY products contained the expected lentiviral sequences. Using the PLSPS, lentivirus pol sequences could typically be detected at levels of one copy in 2 x 10(6) cells after secondary amplification. No specific lentiviral PCR products were detected in DNA from uninfected human or mouse monocytes, feline or bovine leukocytes, mouse, rat or human fibroblast cell lines, chicken embryo fibroblasts, Tahr lung cells, or cell lines infected with the following retroviruses which are not lentiviruses: Rous sarcoma virus, Moloney leukemia virus or Kirsten sarcoma virus, mouse mammary tumor virus, human T-cell lymphotropic virus I, and feline leukemia virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Prediction and biological evolution. Concept paper.

The major issue addressed was how to introduce evolutionary thinking into epidemiology, and the appropriate approach to "evolutionary epidemiology." There was general agreement that disease emergence is not a static but a dynamic process, and that dynamic approaches should therefore be emphasized.

Percutaneous nephrostomy and ureteral stenting in gynecologic malignancies.

OBJECTIVE: To identify the indications, complications, and efficacy of percutaneous nephrostomies and ureteral stents in women with gynecologic cancer. METHODS: In a retrospective study, 40 women underwent urinary diversion with percutaneous nephrostomy and ureteral stents. Nine had ureteral stenosis on initial presentation, 18 had persistent or recurrent cancer, nine had no evidence of disease, and four had operative ureteral damage. Of the nine who were without disease, seven had a urinary conduit. RESULTS: Thirty-five patients had ureteral stenosis, which was bilateral in 24, and five had a ureteral fistula. Sixteen had a unilateral and 22 had bilateral percutaneous nephrostomies, with two cases having stents only. The most common complication was hematuria. Thirteen women were later hospitalized for pyelonephritis. Twenty-nine (72.5%) had ureteral stents, which were bilateral in 12. Renal function was abnormal in 26, but improved in 14 and returned to normal in six. Five fistulas were managed with ureteral stents alone and four were closed. The median time to death (N = 22) was 5.5 months, 12 months in primary cases versus 5.5 months in recurrent cases. Twelve of the remaining 18 were alive without evidence of disease at a median of 38 months, five were alive with disease at a median of 16 months, and one was lost to follow-up. CONCLUSIONS: These techniques are safe and often improve renal function. The procedures have different roles in women with primary and recurrent gynecologic cancer, in those without evidence of recurrent disease, and in those with urinary conduits.

Comparative sensitivity of infectivity assay and mouse antibody production (MAP) test for detection of mouse thymic virus (MTLV).

Mouse thymic virus (murid herpesvirus-3; MTLV) is a naturally occurring T lymphotropic herpesvirus of mice. We compared the sensitivity of infectivity assay, which tests for induction of thymic necrosis in newborn mice, and an enzyme immunoassay (ELISA)-based modified mouse antibody production (MAP) test. Infection in adult mice was verified by infectivity assay of salivary glands. Approximately ten times as much virus was required to infect adult mice as newborns. No adults became infected at the lowest dose (just below 1 ID50 by thymic necrosis in newborn mice); a dose tenfold higher resulted in both infection and seroconversion in three out of five mice. At higher doses tested (up to 8000 ID50), all mice became infected and seroconverted. Infected mice shed virus and remained seropositive for at least six months. False positives were observed in ELISA; these could be eliminated by adding control (uninfected) thymic homogenate (1/10 volume of a 10% homogenate) to the sample diluent. These data suggest that the MAP assay can be a reliable and sensitive indicator of infection in adult mice undergoing primary infection. Although slightly less sensitive than infectivity assay for detecting MTLV, the MAP test is likely to detect most samples containing virus. It is recommended that several mice be used for each sample and that all positive serum samples be retested with control thymic homogenate for increased reliability.

Detection of neovascular signals in a 3 day Walker 256 rat carcinoma by CW Doppler ultrasound.

An animal model was used to study tumor blood flow by the Doppler CW technique. The objective was to determine when neovascularity could be detected as a function of tumor size and time since transplantation. A Walker 256 carcinosarcoma tumor was inoculated into the flank of 17 Sprague-Dawley rats. Doppler examinations, using a 9 MHz CW probe, were performed daily from day 0 to day 7. The contralateral flank was used as a control. No signals were detected from the control side nor from the inoculated side until day 3. By day 3, Doppler signals could be easily detected in all tumor implants with a minimum weight of only 50 mg. These signals showed a mean systolic frequency shift of 3.3 +/- 0.47 kHz at 3 days and 3.46 +/- 0.58 kHz at 7 days. The diastolic Doppler shifted frequency was 1.78 +/- 0.31 kHz at 3 days and 1.88 +/- 0.23 kHz at 7 days giving a Pourcelot index of 0.47 +/- 0.1 at 3 days and 0.46 +/- 0.09 at day 7. These figures indicate the presence of low impedance vessels with high velocity flow such as has been reported in many human tumors. The vascular morphology was further evaluated by digital angiography which demonstrated coincidence between the site of the high velocity Doppler signals and the presence of arteriovenous anastomoses manifested by simultaneous arterial and venous filling. Further infusion techniques using India ink or Microfil showed the chaotic arrangement of tumor vessels located around the growing edge of the tumor implant. The development of such vascularity is a well-recognized prerequisite for tumor growth and invasion.(ABSTRACT TRUNCATED AT 250 WORDS)

ProMED global monitoring of emerging diseases: design for a demonstration program.

The emergence and reemergence of infectious diseases, as the result of recent and ongoing social and environmental changes, urgently calls for a global surveillance system, so that unusual outbreaks can be recognized and controlled at an early stage. ProMED, an international non-governmental group of infectious disease experts, was organized by the Federation of American Scientists to promote the establishment of a global Program to Monitor Emerging Diseases. ProMED proposes the establishment of a demonstration program by prioritizing a small number of strategically-located institutions in the developing world, mainly those least in need of upgrading, for development as sentinel centers. In this way a functional, although limited, network with capabilities for monitoring both endemic and emerging diseases could be rapidly established at minimal cost. The network would serve as an experimental model for future expansion. Initially, each center would develop its own local/regional network with which it would exchange information and assistance, and through which it would collect clinical data and specimens for monitoring the emergence of a limited number of defined syndromes. A central program office would provide protocols, assistance, training, quality assurance, communications, etc. and would coordinate fundraising and program activities. If successful, the syndromes monitored would be expanded and additional institutions strengthened to become new network centers.

Factors and determinants of disease emergence.

Emerging infectious diseases can be defined as infections that have newly appeared in a population or are rapidly increasing in incidence or geographic range. Many of these diseases are zoonoses, including such recent examples as avian influenza, severe acute respiratory syndrome, haemolytic uraemic syndrome (a food-borne infection caused by certain strains of Escherichia coli) and probably human immunodeficiency virus/acquired immune deficiency syndrome. Specific factors precipitating the emergence of a disease can often be identified. These include ecological, environmental or demographic factors that place people in increased contact with the natural host for a previously unfamiliar zoonotic agent or that promote the spread of the pathogen. These factors are becoming increasingly prevalent, suggesting that infections will continue to emerge and probably increase. Strategies for dealing with the problem include focusing special attention on situations that promote disease emergence, especially those in which animals and humans come into contact, and implementing effective disease surveillance and control.

Critical factors in an enzyme immunoassay (ELISA) for antibodies to mouse thymic virus (MTLV).

Mouse thymic virus (MTLV; murid herpesvirus 3) is a naturally occurring herpesvirus of mice. Critical variables in an enzyme immunoassay (ELISA) for antibodies to mouse thymic virus (MTLV) were assessed. High protein binding plates proved unsuitable. For storing coated plates, the most consistent results were obtained when coated plates were washed and stored with coating buffer (phosphate buffered saline, PBS) at -70 degrees C. Storage of antigen at -20 degrees C was unsatisfactory, although coated plates could be stored at -20 degrees C for at least 1-2 weeks. In performing the ELISA, vigorous washing and blocking were critical. However, substituting isotonic (0.9%) saline for PBS in washing solutions gave reliable results at considerable cost savings. For blocking, and as sample diluent, a modification of 'BLOTTO' (5% nonfat dry milk and 0.2% Tween 20) was most satisfactory.

Health care workers' ability and willingness to report to duty during catastrophic disasters.

Catastrophic disasters create surge capacity needs for health care systems. This is especially true in the urban setting because the high population density and reliance on complex urban infrastructures (e.g., mass transit systems and high rise buildings) could adversely affect the ability to meet surge capacity needs. To better understand responsiveness in this setting, we conducted a survey of health care workers (HCWs) (N =6,428) from 47 health care facilities in New York City and the surrounding metropolitan region to determine their ability and willingness to report to work during various catastrophic events. A range of facility types and sizes were represented in the sample. Results indicate that HCWs were most able to report to work for a mass casualty incident (MCI) (83%), environmental disaster (81%), and chemical event (71%) and least able to report during a smallpox epidemic (69%), radiological event (64%), sudden acute respiratory distress syndrome (SARS) outbreak (64%), or severe snow storm (49%). In terms of willingness, HCWs were most willing to report during a snow storm (80%), MCI (86%), and environmental disaster (84%) and least willing during a SARS outbreak (48%), radiological event (57%), smallpox epidemic (61%), and chemical event (68%). Barriers to ability included transportation problems, child care, eldercare, and pet care obligations. Barriers to willingness included fear and concern for family and self and personal health problems. The findings were consistent for all types of facilities. Importantly, many of the barriers identified are amenable to interventions.

Thymic necrosis following oral inoculation of mouse thymic virus.

Mouse thymic virus (MTLV;ICTV designation murid herpesvirus 3) infects developing T lymphocytes of neonatal mice, causing thymic necrosis and acute immunosuppression. Infected animals shed virus indefinitely. However, although transmission in nature is presumably by contact and is likely to involve the oral-nasal route, virtually all experimental studies with MTLV have used systemic (intraperitoneal) inoculation. In order to determine whether systemic inoculation causes artifacts in pathogenesis of the infection, effects of intraperitoneal and oral-nasal inoculation were compared in newborn mice. Thymic necrosis occurred with either route of inoculation, although rate of infection was lower with oral inoculation, varying from about 20% to 67%. There were no gross differences in pathogenesis. Orally infected animals seroconverted and shed virus. These data indicate that the apparent lymphotropism of thymic virus, and induction of thymic necrosis, are not dependent on route of inoculation.

Mouse thymic virus (MTLV; murid herpesvirus 3) infection in athymic nude mice: evidence for a T lymphocyte requirement.

Mouse thymic virus (MTLV; murid herpesvirus 3) is a lymphotropic herpesvirus that cytolytically infects developing T lineage lymphocytes in the thymus of neonatal mice. MTLV establishes a persistent infection and can be recovered indefinitely from infected mice, but nothing is known about requirements for this persistent infection. In order to determine whether T lineage lymphocytes are required for infection, young adult athymic nude (nu/nu) mice and euthymic littermates were infected with MTLV and tested for virus shedding. Although euthymic littermates regularly shed virus, in the nude mice only about 20% of isolation attempts up to 100 days postinfection were positive. Blind passage yielded an additional three isolations out of 14 samples (21%). In addition, unlike many other herpesviruses, the virus did not replicate in a number of epithelial and fibroblastic cell lines that were tested. These data confirm that the virus is preferentially T lymphotropic and suggest that infection may require T lineage lymphocytes.

Mouse thymic necrosis virus: a novel murine lymphotropic agent.

Mouse thymic necrosis virus (TA), one of two naturally occurring herpesviruses in laboratory mice, was first described in 1961. TA has received relatively little attention even though the virus has been isolated independently from various mouse colonies. This neglect is probably due, at least in part, to the lack of suitable cell culture systems. This review summarizes current knowledge concerning thymic necrosis virus, including new results from the author's laboratory. In vivo, TA causes massive thymic necrosis in newborn mice, with temporary ablation of thymocyte precursors for most T lymphocyte classes except T suppressor cells. All strains of laboratory mice appear susceptible. Severe immunosuppression has been demonstrated in acutely infected mice. Most infected animals survive and shed TA chronically from salivary glands and possibly other glandular tissues. In adult mice, primary infection results in persistent salivary gland infection without overt thymic lesions. Infection appears lifelong, with few clinical signs, but possible effects of chronic TA infection on immune function have been studied little. Recent evidence from the author's laboratory suggests that chronic infection may involve T lymphocytes. The name mouse T lymphotropic virus (abbreviation MTLV) is proposed.

Evolving views of viral evolution: towards an evolutionary biology of viruses.

Despite considerable interest in viral evolution, at least among virologists, viruses are rarely considered from the same evolutionary vantage point as other organisms. Early work of necessity emphasized phenotype and phenotypic variation (and therefore arguably was more oriented towards the broader biological and ecological perspectives). More recent work (essentially since the development of molecular evolution in the 1960's but beginning earlier) has concentrated on genotypic variation, with less clarity about the significance of such variations. Other aspects of evolutionary theory, especially considerations of natural selection and of evolutionary constraints, have not widely been applied to viruses, and an evolutionary framework for virology has long been lacking. This becomes apparent in considering 'emerging' viruses, which have often been treated on an ad hoc basis. It was often felt that, because previously unrecognized viruses are involved, mechanisms of viral emergence must mirror the unpredictability of mutations in the viral genome. However, most examples of viral emergence are independent of mutation, at least initially, and are often pre-existing viruses in changed circumstances ('viral traffic'). This conclusion also readily follows from ordinary Darwinian premises, which would require that, like other living species, 'new' organisms are descended only from existing species. In this respect, from a Darwinian perspective, viruses would appear to resemble other organisms.

Factors in the emergence of infectious diseases.

"Emerging" infectious diseases can be defined as infections that have newly appeared in a population or have existed but are rapidly increasing in incidence or geographic range. Among recent examples are HIV/AIDS, hantavirus pulmonary syndrome, Lyme disease, and hemolytic uremic syndrome (a foodborne infection caused by certain strains of Escherichia coli). Specific factors precipitating disease emergence can be identified in virtually all cases. These include ecological, environmental, or demographic factors that place people at increased contact with a previously unfamiliar microbe or its natural host or promote dissemination. These factors are increasing in prevalence; this increase, together with the ongoing evolution of viral and microbial variants and selection for drug resistance, suggests that infections will continue to emerge and probably increase and emphasizes the urgent need for effective surveillance and control. Dr. David Satcher's article and this overview inaugurate Perspectives, a regular section in this journal intended to present and develop unifying concepts and strategies for considering emerging infections and their underlying factors. The editors welcome, as contributions to the Perspectives section, overviews, syntheses, and case studies that shed light on how and why infections emerge, and how they may be anticipated and prevented.

Patterns and predictability in emerging infections.

Many seemingly novel infections have a long history as zoonoses, and perhaps in sporadic human hosts; they gain access to new host populations through ecologic changes and human activity. identification of patterns in the emergence of such illnesses--ranging from influenza and Lyme disease to Ebola fever and AIDS--suggests that worldwide surveillance may be more feasible than once thought.

The public health threat of emerging viral disease.

"Emerging diseases" are those that either have newly appeared in the population or are rapidly increasing their incidence or expanding their geographic range. Emerging viruses usually have identifiable sources, often existing viruses of animals or humans that have been given opportunities to infect new host populations ("viral traffic"). Environmental and social changes, frequently the result of human activities, can accelerate viral traffic, with consequent increases in disease emergence. Host factors, including nutrition, have often received less attention in the past but are of considerable importance. These factors, combined with the ongoing evolution of viral and microbial variants, make it likely that emerging infections will continue to appear and probably increase, emphasizing the need for effective surveillance.