CRISPR-dCas9 based DNA detection scheme for diagnostics in resource-limited settings

Nucleic-acid detection is crucial for basic research as well as for applications in medicine such as diagnostics. In resource-limited settings, however, most DNA-detection diagnostic schemes are inapplicable since they rely on expensive machinery, electricity, and trained personnel. Here, we present an isothermal DNA detection scheme for the diagnosis of pathogenic DNA in resource-limited settings. DNA was extracted from urine and blood samples using two different instrument-free methods, and amplified using Recombinase Polymerase Amplification with a sensitivity of <10 copies of DNA within 15 minutes. Target DNA was bound by dCas9/sgRNA that was labelled with a DNA oligomer to subsequently induce Rolling Circle Amplification. This second amplification step produced many copies of a G-quadruplex DNA structure that facilitates a colorimetric readout that is visible to the naked eye. This isothermal DNA-detection scheme can be performed at temperatures between 20-45 °C. As an example of the applicability of the approach, we isothermally (23 °C) detected DNA from a parasite causing visceral leishmaniasis that was spiked into buffer and resulted in a sensitivity of at least 1 zeptomole. For proof of principle, DNA spiked into blood was coupled to the CRISPR-dCas9-based detection scheme yielding a colorimetric readout visible to the naked eye. Given the versatility of the guide-RNA programmability of targets, we envision that this DNA detection scheme can be adapted to detect any DNA with minimal means, which facilitates applications such as point-of-care diagnostics in resource-limited settings.

Diagnosing point-of-care diagnostics for neglected tropical diseases

Inadequate and nonintegrated diagnostics are the Achilles' heel of global efforts to monitor, control, and eradicate neglected tropical diseases (NTDs). While treatment is often available, NTDs are endemic among marginalized populations, due to the unavailability or inadequacy of diagnostic tests that cause empirical misdiagnoses. The need of the hour is early diagnosis at the point-of-care (PoC) of NTD patients. Here, we review the status quo of PoC diagnostic tests and practices for all of the 24 NTDs identified in the World Health Organization's (WHO) 2021-2030 roadmap, based on their different diagnostic requirements. We discuss the capabilities and shortcomings of current diagnostic tests, identify diagnostic needs, and formulate prerequisites of relevant PoC tests. Next to technical requirements, we stress the importance of availability and awareness programs for establishing PoC tests that fit endemic resource-limited settings. Better understanding of NTD diagnostics will pave the path for setting realistic goals for healthcare in areas with minimal resources, thereby alleviating the global healthcare burden.

αv-Class integrin binding to fibronectin is solely mediated by RGD and unaffected by an RGE mutation

Fibronectin (FN) is an essential glycoprotein of the extracellular matrix; binds integrins, syndecans, collagens, and growth factors; and is assembled by cells into complex fibrillar networks. The RGD motif in FN facilitates cell binding- and fibrillogenesis through binding to α5β1 and αv-class integrins. However, whether RGD is the sole binding site for αv-class integrins is unclear. Most notably, substituting aspartate with glutamate (RGE) was shown to eliminate integrin binding in vitro, while mouse genetics revealed that FNRGE preserves αv-class integrin binding and fibrillogenesis. To address this conflict, we employed single-cell force spectroscopy, engineered cells, and RGD motif-deficient mice (Fn1ΔRGD/ΔRGD) to search for additional αv-class integrin-binding sites. Our results demonstrate that α5β1 and αv-class integrins solely recognize the FN-RGD motif and that αv-class, but not α5β1, integrins retain FN-RGE binding. Furthermore, Fn1ΔRGD/ΔRGD tissues and cells assemble abnormal and dysfunctional FNΔRGD fibrils in a syndecan-dependent manner. Our data highlight the central role of FN-RGD and the functionality of FN-RGE for αv-class integrins.

Matching Development of Point-of-Care Diagnostic Tests to the Local Context: A Case Study of Visceral Leishmaniasis in Kenya and Uganda

We provide a new protocol to connect how findings from field research on the local health care setting in resource-limited regions can inform researchers that are working toward developing a new point-of-care diagnostic test for neglected tropical diseases.

The rapid growth of point-of-care (POC) diagnostic tests necessitates a clear vision of when, where, and why a new POC diagnostic test needs to be developed and how it can be used in a way that matches a local health care context. Here, we present an innovative approach toward developing a concept target product profile (CTPP), which is a new mapping tool that helps researchers match a new diagnostic test to a specific local health care context early in the research and development process. As a case study, we focus on the diagnosis of visceral leishmaniasis (VL) in rural resource-limited regions of Kenya and Uganda. Our stepwise approach integrates elements of design thinking and uses a combination of literature reviews and field research for a context analysis of local health care systems and practices. We then use visual thinking in the form of Gigamaps and patient journeys to identify use case scenarios and to present our findings from the field research to key stakeholders. The use case scenarios describe the diagnostic scope of a new POC test based on the feasibility of the new test, the local need, and the contextual fit. For our case study of VL, we identify 2 valuable use case scenarios, namely test-of-cure and screening and confirmation, and we formulate a CTPP. We anticipate that a CTPP will enable researchers to match a new POC diagnostic test during the research and development process to the local health care context in which it will be used.

Corrigendum: Fibronectin-bound α5β1 integrins sense load and signal to reinforce adhesion in less than a second

This corrects the article DOI: 10.1038/nmat5023.

Fibronectin-bound α5β1 integrins sense load and signal to reinforce adhesion in less than a second

Integrin-mediated mechanosensing of the extracellular environment allows cells to control adhesion and signalling. Whether cells sense and respond to force immediately upon ligand-binding is unknown. Here, we report that during adhesion initiation, fibroblasts respond to mechanical load by strengthening integrin-mediated adhesion to fibronectin (FN) in a biphasic manner. In the first phase, which depends on talin and kindlin as well as on the actin nucleators Arp2/3 and mDia, FN-engaged α5β1 integrins activate focal adhesion kinase (FAK) and c-Src in less than 0.5 s to steeply strengthen α5β1- and αV-class integrin-mediated adhesion. When the mechanical load exceeds a certain threshold, fibroblasts decrease adhesion and initiate the second phase, which is characterized by less steep adhesion strengthening. This unique, biphasic cellular adhesion response is mediated by α5β1 integrins, which form catch bonds with FN and signal to FN-binding integrins to reinforce cell adhesion much before visible adhesion clusters are formed.

αV-class integrins exert dual roles on α5β1 integrins to strengthen adhesion to fibronectin

Upon binding to the extracellular matrix protein, fibronectin, αV-class and α5β1 integrins trigger the recruitment of large protein assemblies and strengthen cell adhesion. Both integrin classes have been functionally specified, however their specific roles in immediate phases of cell attachment remain uncharacterized. Here, we quantify the adhesion of αV-class and/or α5β1 integrins expressing fibroblasts initiating attachment to fibronectin (≤120 s) by single-cell force spectroscopy. Our data reveals that αV-class integrins outcompete α5β1 integrins. Once engaged, αV-class integrins signal to α5β1 integrins to establish additional adhesion sites to fibronectin, away from those formed by αV-class integrins. This crosstalk, which strengthens cell adhesion, induces α5β1 integrin clustering by RhoA/ROCK/myosin-II and Arp2/3-mediated signalling, whereas overall cell adhesion depends on formins. The dual role of both fibronectin-binding integrin classes commencing with an initial competition followed by a cooperative crosstalk appears to be a basic cellular mechanism in assembling focal adhesions to the extracellular matrix.

The fibronectin synergy site re-enforces cell adhesion and mediates a crosstalk between integrin classes

Fibronectin (FN), a major extracellular matrix component, enables integrin-mediated cell adhesion via binding of α5β1, αIIbβ3 and αv-class integrins to an RGD-motif. An additional linkage for α5 and αIIb is the synergy site located in close proximity to the RGD motif. We report that mice with a dysfunctional FN-synergy motif (Fn1^syn/syn) suffer from surprisingly mild platelet adhesion and bleeding defects due to delayed thrombus formation after vessel injury. Additional loss of β3 integrins dramatically aggravates the bleedings and severely compromises smooth muscle cell coverage of the vasculature leading to embryonic lethality. Cell-based studies revealed that the synergy site is dispensable for the initial contact of α5β1 with the RGD, but essential to re-enforce the binding of α5β1/αIIbβ3 to FN. Our findings demonstrate a critical role for the FN synergy site when external forces exceed a certain threshold or when αvβ3 integrin levels decrease below a critical level.

DOI:http://dx.doi.org/10.7554/eLife.22264.001

Kindlin-2 cooperates with talin to activate integrins and induces cell spreading by directly binding paxillin

Integrins require an activation step prior to ligand binding and signaling. How talin and kindlin contribute to these events in non-hematopoietic cells is poorly understood. Here we report that fibroblasts lacking either talin or kindlin failed to activate β1 integrins, adhere to fibronectin (FN) or maintain their integrins in a high affinity conformation induced by Mn(2+). Despite compromised integrin activation and adhesion, Mn(2+) enabled talin- but not kindlin-deficient cells to initiate spreading on FN. This isotropic spreading was induced by the ability of kindlin to directly bind paxillin, which in turn bound focal adhesion kinase (FAK) resulting in FAK activation and the formation of lamellipodia. Our findings show that talin and kindlin cooperatively activate integrins leading to FN binding and adhesion, and that kindlin subsequently assembles an essential signaling node at newly formed adhesion sites in a talin-independent manner.

clpC operon regulates cell architecture and sporulation in Bacillus anthracis

The clpC operon is known to regulate several processes such as genetic competence, protein degradation and stress survival in bacteria. Here, we describe the role of clpC operon in Bacillus anthracis. We generated knockout strains of the clpC operon genes to investigate the impact of CtsR, McsA, McsB and ClpC deletion on essential processes of B. anthracis. We observed that growth, cell division, sporulation and germination were severely affected in mcsB and clpC deleted strains, while none of deletions affected toxin secretion. Growth defect in these strains was pronounced at elevated temperature. The growth pattern gets restored on complementation of mcsB and clpC in respective mutants. Electron microscopic examination revealed that mcsB and clpC deletion also causes defect in septum formation leading to cell elongation. These vegetative cell deformities were accompanied by inability of mutant strains to generate morphologically intact spores. Higher levels of polyhydroxybutyrate granules accumulation were also observed in these deletion strains, indicating a defect in sporulation process. Our results demonstrate, for the first time, the vital role played by McsB and ClpC in physiology of B. anthracis and open up further interest on this operon, which might be of importance to success of B. anthracis as pathogen.

Assay for characterizing the recovery of vertebrate cells for adhesion measurements by single-cell force spectroscopy

Single-cell force spectroscopy (SCFS) is becoming a widely used method to quantify the adhesion of a living cell to a substrate, another cell or tissue. The high sensitivity of SCFS permits determining the contributions of individual cell adhesion molecules (CAMs) to the adhesion force of an entire cell. However, to prepare adherent cells for SCFS, they must first be detached from tissue-culture flasks or plates. EDTA and trypsin are often applied for this purpose. Because cellular properties can be affected by this treatment, cells need to recover before being further characterized by SCFS. Here we introduce atomic force microscopy (AFM)-based SCFS to measure the mechanical and adhesive properties of HeLa cells and mouse embryonic kidney fibroblasts while they are recovering after detachment from tissue-culture. We find that mechanical and adhesive properties of both cell lines recover quickly (<10 min) after detachment using EDTA, while trypsin-detached fibroblasts require >60 min to fully recover. Our assay introduced to characterize the recovery of mammalian cells after detachment can in future be used to estimate the recovery behavior of other adherent cell types.

Markers and risk factors for HCV, HBV and HIV in a network of injecting drug users in Melbourne, Australia

BACKGROUND AND AIMS

Current injecting drug users (IDU) in major street drug markets within greater Melbourne were recruited to a longitudinal study on blood borne viruses. Here we investigated risk factors for hepatitis C virus (HCV), hepatitis B virus (HBV) and HIV infection in these IDU at the time of their recruitment.

METHODS

Three hundred and eighty-two IDU completed detailed questionnaires on their drug use and risk behaviours, and provided blood samples for serology testing. These data were analysed using univariate and multivariate techniques.

RESULTS

The overall prevalence of exposure to HCV, HBV and HIV was estimated at 70%, 34% and <1%, respectively. Independent predictors of HCV exposure were history of imprisonment (RR 1.34, 95% CI 1.19-1.52), use of someone else's needle or syringe (RR 1.23, 95% CI 1.07-1.42), >7.6years length of time injecting (RR 1.21, 95% CI 1.07-1.37), and originating from Vietnam (RR 1.12, 95% CI 1.07-1.18). Independent predictors of HBV exposure were HCV exposure (RR 2.15, 95% CI 1.35-3.43), >7.6years length of time injecting (RR 1.57, 95% CI 1.17-2.13) and originating from outside Australia (RR 1.60, 95% CI 1.22-2.10). Neither prison- nor community-applied tattoos predicted HCV or HBV exposure. Up to 31% of IDU who injected for 1year or less were HCV antibody positive, as were 53% of those who injected for 2years or less.

CONCLUSIONS

Ongoing engagement with young IDU, through the provision of harm reduction education and resources, is critical if we are to address blood borne viral infections and other health and social harms associated with injecting drug use.

Allelic variations in CYP2D6 gene and susceptibility to cervical cancer

Epidemiological studies have identified a number of risk factors that contribute to the development of cervical cancer precursors and cervical cancer. These include infection with certain oncogenic types of human papillomaviruses (HPVs) and other socio-economic factors. Tobacco smoking is an independent risk-factor for cervical neoplasia. It has been found that polymorphism at loci that encode carcinogen-metabolizing enzyme such as cytochrome P450 2D6 (CYP2D6) catalyzing the detoxification of carcinogens may determine susceptibility to cervical cancer. Therefore, it is likely that an understanding of these allelic differences is important for determining an individual's risk of cancer and susceptibility to potentially toxic agents. The aim of the present study was to elucidate the role of CYP2D6 polymorphism and susceptibility to squamous cell carcinoma of the uterine cervix in Indian population. Therefore, the genotype frequencies at this locus in females suffering with low-grade CIN, high-grade CIN and squamous cell carcinoma were compared. The control group consisted of 77 females with normal cervical cytology and the cases comprised of 61 mild/moderate dysplasia, 48 severe dysplasia and 45 cases of squamous cell carcinoma of uterine cervix. The individuals were divided into poor metabolizers (PM) and extensive metabolizers (EM) on the basis of their ability to metabolize certain drugs and carcinogens. Comparison of the frequency distribution for the combination of CYP2D6 EM genotype and smoking between mild/moderate and severe dysplasia was statistically significant (p=0.047) suggesting that women with cervical intraepithelial neoplasia I/II (CIN I/ CIN II) and CYP2D6 EM genotype who smoke appears to have more chances for the lesions to progress to CIN III. Whereas, frequency distribution for the same combination between severe dysplasia and squamous cell carcinoma failed to attain any statistical significance suggesting that CIN III with CYP2D6 EM genotype has less chance to progress to cervical cancer. Increased frequency of CYP2D6 EM and tobacco smoking show strong association with CIN III, indicating that not all lesions with the histopathological high grade CIN are premalignant. Conversely some squamous cell carcinomas may not be preceded by CIN.

DCs as targets for vaccine design

The increasingly stringent requirements laid down by regulatory authorities have brought to an end the largely empirical design of vaccines. Vaccines must now be designed rationally, in order that appropriate immune responses are elicited with few or no side effects. The DC plays a pivotal role in determining the type of immune response that ensues following exposure of the host to an Ag. In this review, we identify some of the features and properties of DCs, and how these properties can be exploited in the design of smart vaccines.

Will a vaccine to nasopharyngeal carcinoma retain orphan status?

Epstein-Barr virus (EBV) infection is associated with infectious mononucleosis (IM) and with a number of human malignancies including nasopharyngeal carcinoma (NPC), Hodgkin's disease (HD) and immunoblastic lymphoma (IL). Their potential for immunotherapeutic treatment by cytotoxic T cells (CTL) is dependent on the degree of EBV antigen expression, with the best prospect revolving around IM where a vaccine is under development and IL of transplant patients where adoptive transfer of in vitro reactivated CTL has already been demonstrated to be effective. The opportunities for effective immunotherapy in the treatment of NPC is reduced since the available targets are limited to relatively non-immunogenic proteins. Perhaps more importantly, the development of immunotherapeutics is not considered a realistic commercial proposition. The best chance of developing an effective vaccine is to exploit the similarities in phenotype between HD and NPC since a vaccine to the former is likely to have more commercial appeal.

Asymptomatic primary Epstein-Barr virus infection occurs in the absence of blood T-cell repertoire perturbations despite high levels of systemic viral load

Primary infection with the human herpesvirus, Epstein-Barr virus (EBV), may result in subclinical seroconversion or may appear as infectious mononucleosis (IM), a lymphoproliferative disease of variable severity. Why primary infection manifests differently between patients is unknown, and, given the difficulties in identifying donors undergoing silent seroconversion, little information has been reported. However, a longstanding assumption has been held that IM represents an exaggerated form of the virologic and immunologic events of asymptomatic infection. T-cell receptor (TCR) repertoires of a unique cohort of subclinically infected patients undergoing silent infection were studied, and the results highlight a fundamental difference between the 2 forms of infection. In contrast to the massive T-cell expansions mobilized during the acute symptomatic phase of IM, asymptomatic donors largely maintain homeostatic T-cell control and peripheral blood repertoire diversity. This disparity cannot simply be linked to severity or spread of the infection because high levels of EBV DNA were found in the blood from both types of acute infection. The results suggest that large expansions of T cells within the blood during IM may not always be associated with the control of primary EBV infection and that they may represent an overreaction that exacerbates disease.

Contrasting Epstein-Barr virus-specific cytotoxic T cell responses to HLA A2-restricted epitopes in humans and HLA transgenic mice: implications for vaccine design

This study investigates the hierarchy of cytotoxic T cell (CTL) responses to twelve HLA A2-restricted epitopes from the latent, lytic and structural proteins of Epstein-Barr virus (EBV) in acute infectious mononucleosis and in healthy seropositive donors and the relative immunogenecity of these epitopes in transgenic mice. Responses to the lytic epitope were uniformly strong in all healthy seropositive individuals and acute infectious mononucleosis donors while moderate or low responses were observed to the latent and structural epitopes, respectively in both groups studied. In contrast, when HLA A2/Kb transgenic mice were immunised with these peptide epitopes, CTL responses were observed to all epitopes with a maximal response to the epitopes within the structural proteins and low to moderate responses to the latent epitopes. This hierarchy of CTL responses in mice was also reflected in an MHC stabilisation analysis. These contrasting CTL responses in humans following natural infection compared to the immunogenicity of these epitopes and their ability to stabilise MHC may need to be considered when designing an EBV vaccine.

Dysregulation of IL-4 expression in lepromatous leprosy patients with and without erythema nodosum leprosum

In order to increase our understanding of the immunological basis of erythema nodosum leprosum (ENL), we studied Th-like cytokine profiles in 130 leprosy patients, employing both the conventional and a novel, real-time, fluorogenic reverse transcriptase-based PCR (RT-PCR). The concomitant expression of both Th-like cytokines, interferon-gamma and IL-4, and the regulatory cytokines, IL-10 and IL-12, was studied in the peripheral blood cells of leprosy patients with and without ENL. In the conventional RT-PCR, varied cytokine profiles were observed in individual patients of all clinical types. Fifty-three percent of lepromatous patients without ENL and 59% of tuberculoid leprosy patients showed co-expression of IFN gamma and IL-4, indicating a non-polarized Th 0 pattern. Of the 36 patients with ENL, 58% demonstrated a polarized Th 1 pattern, with only 30% expressing both cytokines. Semiquantitative RT-PCR indicated a lower expression of IL-4 compared to that of IFN gamma in the lepromatous patients without ENL; the difference was even greater among those with ENL. The sensitive, real-time PCR confirmed the down-regulation of IL-4 and IL-10, with absence of IL-4 in half of the patients, resulting in skewing of the cytokine response toward a Th 1-like profile.

Peptide-MHC class I tetrameric complexes display exquisite ligand specificity

The production of synthetic MHC-peptide tetramers has revolutionized cellular immunology by revealing enormous CD8(+) T cell expansions specific for peptides from various pathogens. A feature of these reagents, essential for their staining function, is that they bind T cells with relatively high avidity. This could, theoretically, promote cross-reactivity with irrelevant T cells leading to overestimates of epitope-specific T cell numbers. Therefore, we have investigated the fine specificity of CTL staining with these reagents for comparison with functional data. Using a panel of CTL clones with distinct fine specificity patterns for analogs of an HLA-B8-binding EBV epitope, together with B8 tetramers incorporating these peptides, we show a very good correlation between tetramer staining and peptide activity in cytotoxicity assays. Significant staining only occurred with tetramers that incorporate strong stimulatory agonist peptides and not weak agonists that are unlikely to induce full T cell activation at physiological levels of presentation. In almost every case where a peptide analog had >10-fold less activity than the optimal EBV peptide in cytotoxicity assays, the corresponding tetramer stained with >10-fold less intensity than the EBV epitope tetramer. Furthermore, by examining an EBV-specific clonotypic T cell expansion in EBV-exposed individuals, we show similar fine specificity in tetramer staining of fresh peripheral T cells. Collectively, our data demonstrate the exquisite specificity of class I MHC-peptide tetramers, underlining their accuracy in quantifying only those T cells capable of recognizing the low levels of cell surface peptide presented after endogenous Ag processing.

Experimental infection model for Sin Nombre hantavirus in the deer mouse (Peromyscus maniculatus)

The relationship between hantaviruses and their reservoir hosts is not well understood. We successfully passaged a mouse-adapted strain of Sin Nombre virus from deer mice (Peromyscus maniculatus) by i.m. inoculation of 4- to 6-wk-old deer mouse pups. After inoculation with 5 ID(50), antibodies to the nucleocapsid (N) antigen first became detectable at 14 d whereas neutralizing antibodies were detectable by 7 d. Viral N antigen first began to appear in heart, lung, liver, spleen, and/or kidney by 7 d, whereas viral RNA was present in those tissues as well as in thymus, salivary gland, intestine, white fat, and brown fat. By 14 d nearly all tissues examined displayed both viral RNA and N antigen. We noted no consistent histopathologic changes associated with infection, even when RNA load was high. Viral RNA titers peaked on 21 d in most tissues, then began to decline by 28 d. Infection persisted for at least 90 d. The RNA titers were highest in heart, lung, and brown fat. Deer mice can be experimentally infected with Sin Nombre virus, which now allows provocative examination of the virus-host relationship. The prominent involvement of heart, lung, and brown fat suggests that these sites may be important tissues for early virus replication or for maintenance of the virus in nature.

Humoral immune responses in the hantavirus cardiopulmonary syndrome

The immunologic responses that mediate viral clearance of and recovery from hantavirus cardiopulmonary syndrome (HCPS) due to Sin Nombre (SN) virus are unknown. Serial serum samples from 26 patients with acute SN virus infection were tested for IgG, IgA, and IgM reactivity to recombinant viral nucleocapsid (N) and glycoprotein G1 antigens by a novel strip immunoblot assay. The titers of antibodies capable of neutralizing SN virus in vitro also were determined for each sample. At admission, patients with severe disease had lower titers of IgG antibodies to SN virus N antigen (P<.033) and lower neutralizing antibody titers (P<3.4x10-5), compared with patients with mild disease. These data suggest that a strong neutralizing antibody response may be a predictor of effective clearance of and recovery from SN virus infection and raise the possibility that passive immunotherapy may be useful in HCPS.

Intramuscular inoculation of Sin Nombre hantavirus cDNAs induces cellular and humoral immune responses in BALB/c mice

To examine whether genetic immunization with Sin Nombre (SN) hantavirus genes could elicit immune responses, nine fragments spanning the envelope glycoprotein genes G1 and G2, and the complete N gene were cloned into a CMV expression vector. To ensure representation of all potential epitopes, adjacent fragments of the glycoprotein genes overlapped one another by 100 nucleotides. Vectors containing the gene fragments were inoculated intramuscularly into BALB/c mice and splenocyte proliferation and western blot-detectable antibodies and neutralization titers were determined. The N gene and seven of the nine M segment-derived cDNAs tested produced significant specific lymphoproliferative responses, and many of the constructs elicited either neutralizing or western blot-detectable antibodies. These promising results encourage the development of infection models for SN virus that will be capable of detecting protective responses.

High prevalence of hantavirus infection in Indian communities of the Paraguayan and Argentinean Gran Chaco

Serologic evidence of past infection with a Sin Nombre-like hantavirus(es) was demonstrated in 78 (40.4%) of 193 Indians living in western Paraguay and in 38 (17.1%) of 222 Indians inhabiting the Salta province of northern Argentina. In both populations seroprevalence increased with age, with the most striking increase occurring at 18 years of age in the Paraguayan population and at 35 years of age in the Salta population. The peak prevalences in both populations (66.6% and 44.0%, respectively) were seen in Indians > 53 years old. Although no sex difference was observed in the Paraguayan Indians, in the Salta population seroprevalence was greater in males than in females. Familiar clustering of the infection was observed. The data indicate that the Indian populations of the Gran Chaco are frequently exposed to and survive infection with a Sin Nombre-like virus(es). Possible explanations of this novel epidemiology are discussed.

Bayou virus-associated hantavirus pulmonary syndrome in Eastern Texas: identification of the rice rat, Oryzomys palustris, as reservoir host

We describe the third known case of hantavirus pulmonary syndrome (HPS) due to Bayou virus, from Jefferson County, Texas. By using molecular epidemiologic methods, we show that rice rats (Oryzomys palustris) are frequently infected with Bayou virus and that viral RNA sequences from HPS patients are similar to those from nearby rice rats. Bayou virus is associated with O. palustris; this rodent appears to be its predominant reservoir host.

Management of hydrocephalus

The present study is an analysis of 747 patients with hydrocephalus, treated and followed up in the Hydrocephalus Clinic run by the department of Paediatric Surgery at the All India Institute of Medical Sciences, New Delhi. The distribution of patients was: congenital-46%, post-meningomyelocoele excision-28%, post-meningitic-21% and others-5% (including post haemorrhagic and post encephalocoele excision hydrocephalus. The average age was 7 months in the shunted group and 10 months in the medical group with overall male to female ratio of 2.3:1. The data were analysed to study the effect of treatment on ventriculomegaly and mental development with special reference to the type of treatment (shunt versus medical) and age at starting treatment. The probability of shunt failure was also studied. A comparison of ventricular size in US/CAT scans between the time of starting treatment and last follow-up revealed improvement in ventriculomegaly in 60% of the shunted patients but only 30% of the medically treated patients. A significant difference was particularly noted in patients with severe hydrocephalus, 72% and 22%, respectively. Comparison of the mean Mental Performance Quotient (MPQ) scores in the shunted & medically treated patients also revealed significantly better MPQ scores in the shunted group (p = < 0.001). Probability of shunt survival, as depicted by the Kaplan-Meier survival curve, revealed that there is a high rate of shunt failure in the first 12 months, followed by a dramatic slowing down. Our observations support the contention that CSF shunt surgery offers better outcome than medical management even when ventriculomegaly is severe at the time of presentation.

Rio Mamore virus: genetic characterization of a newly recognized hantavirus of the pygmy rice rat, Oligoryzomys microtis, from Bolivia

Human hantavirus disease occurs throughout much of South America. The rodent hosts and the specific etiologic agent(s) are largely unknown, but many reported cases occurred within the habitation ranges of oryzomine rodents (rice rats). We have identified a genetically novel hantavirus (Rio Mamore virus [RM]) of the pygmy rice rat Oligoryzomys microtis in Bolivia. The complete sequence of the small (S) genome and the partial sequence of the medium (M) genome are described. This virus is closely related to the newly identified human pathogen Andes virus from Patagonia. To facilitate improved diagnosis of hantavirus infections in South America, we have expressed the complete nucleocapsid protein of RM in Escherichia coli and affinity-purified it for use in an ELISA and Western blot assays for antibodies to RM.

Induction of hypoglycaemia in Japanese encephalitis virus infection: the role of T lymphocytes

We report here development of hypoglycaemia in the convalescent phase of Japanese encephalitis virus (JEV) infection in mice by the induction of antigen-specific Ly1- 2+ T cells in the spleen which mediate hypoglycaemia through the generation of soluble T cell hypoglycaemic factor (TCHF). The TCHF acted in a dose-dependent manner and was found to be trypsin-sensitive and thermolabile. It was purified on Superose-12 high performance liquid chromatography (HPLC) gel filtration column and purified protein migrated as a approximately 25-kD band on SDS-PAGE. The JEV-induced hypoglycaemia coincided with an increased circulating glucagon level, without any alterations in blood insulin and growth hormone concentrations. These effects were mimicked by TCHF. These results indicate that JEV-primed T lymphocytes mediate hypoglycaemia through the production of a soluble hypoglycaemic factor.

Cocirculation of multiple hantaviruses in Texas, with characterization of the small (S) genome of a previously undescribed virus of cotton rats (Sigmodon hispidus)

An environmental and laboratory investigation was conducted after a fatal childhood case of hantavirus pulmonary syndrome occurred in Deaf Smith County, Texas in May 1995. A trapping campaign was conducted to identify possible rodent carriers. Six species of murid and heteromyid rodents were collected, and at least one hantavirus-seropositive specimen was found in each of the five murid species. Tissues from a selection of 11 seropositive specimens were examined by the polymerase chain reaction (PCR) and sequencing of viral genetic material. The predominant hantavirus was El Moro Canyon virus (ELMCV), which occurred in three of three harvest mice (Reithrodontomys megalotis) and in three of four deer mice (Peromyscus maniculatus) examined. Sin Nombre virus (SNV) was found in one deer mouse and one white-footed mouse (P. leucopus). A seropositive house mouse (Mus musculus) was negative by PCR. Two cotton rats (Sigmodon hispidus) were infected by a virus of novel genotype (Muleshoe virus [MULEV]) that bears closet resemblance to Bayou hantavirus. The sequence of the complete small genomic segment was determined for one MULEV, and high-level expression of its nucleocapsid protein was induced in Escherichia coli. Serologic studies indicated that the most likely etiologic agent in the human infection was SNV.

Characterization of a membrane protease from rat submaxillary-gland mitochondria that possess thrombin-like activity

A membrane protease possessing thrombin-like activity was purified to homogeneity from mitochondria of rat submaxillary gland. The molecular mass of the enzyme was determined to be 45 kDa by SDS/PAGE under reducing conditions and by gel filtration on a Sephadex G-100 column. The enzyme is a glycoprotein and has an isoelectric point of 3.25. Maximum activity was observed at pH 10.5. Inhibition by di-isopropyl fluorophosphate, benzamidine, aprotinin and antipain suggested the enzyme to be a serine protease. Other inhibitors such as EDTA, soya-bean trypsin inhibitor, lima-bean trypsin inhibitor, TosLysCH2Cl and chymostatin did not alter the activity. The enzyme showed affinity towards different synthetic substrates (p-nitroanilide derivatives) containing arginine at the P1 position. Kinetic studies revealed that Kcat./Km was highest with the substrate N-Bz-Phe-Val-Arg-p-nitroanilide. The enzyme exhibits significant plasma-coagulating activity. The coagulation initiated by the enzyme was not altered by concanavalin A, indicating that the carbohydrate moiety of the enzyme is not essential for this reaction. Further, this enzyme can catalyse the formation of fibrin clots from purified fibrinogen, which describes its thrombin-like activity. However, an antibody raised against the purified enzyme inhibited the plasma-clotting as well as fibrinogen-clotting activity of the enzyme. Fibrinogen coagulation by the enzyme was blocked in the presence of aprotinin, a protease inhibitor. Release of fibrinopeptides A and B from bovine fibrinogen by the enzyme has been shown by HPLC analysis. Our studies reveal that the enzyme reported here differs from trypsin, chymotrypsin and other mitochondrial proteases reported so far.

Monocyte derived IL 10 and PGE2 are associated with the absence of Th 1 cells and in vitro T cell suppression in lepromatous leprosy

Our previous studies had shown that the clinicopathological spectrum in leprosy was associated with discrete T cell subsets in circulation, with tuberculoid patients having antigen-induced Th 1, whereas lepromatous leprosy patients with antigen-specific T cell anergy possessed Th 2 cells. The present study shows that infected monocytes from lepromatous but not tuberculoid leprosy patients released soluble factors (MoF(s)) containing IL-10 and PGE2 which inhibited M. leprae induced in vitro lymphoproliferation of previously sensitised healthy or tuberculoid leprosy subjects. A strong negative correlation was observed between adherent cell derived IL-10 and IL-2 at the level of both the product and cytokine mRNA. Moreover, anti-IL-10 antibodies and indomethacin partially reversed the suppressor effects of MoF(s). Taken together these studies indicate that infected monocytes contribute to the development of T cell anergy by releasing factors that affect regulatory cytokines and T cell subset differentiation in lepromatous leprosy.

Myelin P0 glycoprotein and a synthetic peptide containing the palmitoylation site are both autoacylated

P0, the major protein of the PNS myelin, is palmitoylated at the cytoplasmic Cys153. To gain insights into the mechanism of P0 acylation, the in vitro palmitoylation of both P0 and a synthetic Cys153-containing octapeptide was studied. Incubation of PNS myelin membranes or isolated P0 with [3H]palmitoyl-CoA resulted in specific labeling of this protein, suggesting that the reaction is nonenzymatic. Incorporation of the labeled fatty acid into P0 was not affected by boiling the isolated P0 for 15 min before incubation or by adding sciatic nerve homogenate to the reaction mixture, which confirms the nonenzymatic nature of the reaction. After chemical deacylation, P0 was palmitoylated at a higher rate, suggesting that the original site was reacylated. Furthermore, tryptic digestion and peptide mapping showed that the same sites are acylated in vitro as in nerve slices indicating that the reaction has physiological significance. On incubation with [14C]palmitoyl-CoA, the synthetic peptide encompassing the natural P0 acylation site (I150RYCWLRR157) was also spontaneously acylated at the cysteine residue. Thus, the integrity of the protein is not required for the nonenzymatic transacylation reaction. At pH 7.4 and 37 degrees C, peptide palmitoylation followed a second-order reaction (k2 = 246 +/- 6 M-1 min-1) and is likely a bimolecular nucleophilic substitution with the peptide thiolate attacking the highly reactive thioester bond in palmitoyl-CoA. The activation energy calculated from the Arrhenius plot is approximately 2 kcal/mol and much lower than that of enzyme-catalyzed transacylations. Finally, two other P0 peptides (V121PTRYG126 and K109TSQVTL115) as well as various unrelated thiol-containing compounds, including cysteine, glutathione, pressinoic acid (CYFQNC), and crustacean cardioactive peptide (PFCNAFTGC), were not autoacylated. These results indicate that the IRYCWLRR peptide represents a particular structural motif and/or has some chemical features that allow the reaction to occur spontaneously.

Technetium-99m-HMPAO SPECT cerebral blood flow study in children with craniosynostosis

Premature closure of cranial sutures (primary craniosynostosis) in children leads to characteristic skull deformities and prevents the constricted brain from growing normally. Although the cause remains unknown, several etiological factors have been cited. Recently, hypovascularity has been reported as a possible cause of craniosynostosis.

METHODS

In a prospective study regional cerebral blood flow studies were carried out with 99mTc-HMPAO SPECT in seven children with craniosynostoses. Five preoperative and six postoperative studies were conducted and the results correlated with radiological and surgical findings.

RESULTS

Preoperative studies revealed regional hypovascularity in the underlying cerebral hemisphere, corresponding to the fused sutures. Postoperative studies revealed disappearance of these perfusion defects in most cases, indicating normalization of perfusion following surgical decompression.

CONCLUSION

This study establishes the presence of cerebral hypovascularity in craniosynostoses and suggests that early surgery and release of craniostenosis is essential to achieve optimum perfusion and brain development.

Overview: protein palmitoylation in the nervous system: current views and unsolved problems

Palmitoylation refers to a dynamic post-translational modification of proteins involving the covalent attachment of long-chain fatty acids to the side chains of cysteine, threonine or serine residues. In recent years, palmitoylation has been identified as a widespread modification of both viral and cellular proteins. Because of its dynamic nature, protein palmitoylation, like phosphorylation, appears to have a crucial role in the functioning of the nervous system. Several important questions regarding the post-translational acylation of cysteine residues in proteins are briefly discussed: (a) What are the molecular mechanisms involved in dynamic acylation? (b) What are the determinants of the fatty acid specificity and the structural requirements of the acceptor proteins? (c) What are the physiological signals regulating this type of protein modification, and (d) What is the biological role(s) of this reaction with respect to the functioning of specific nervous system proteins? We also present the current experimental obstacles that have to be overcome to fully understand the biology of this dynamic modification.

Prognostic significance of serum iron levels in cases of Japanese encephalitis

Forty-one children with acute laboratory confirmed Japanese encephalitis were studied. Serum iron concentrations were consistently low following Japanese encephalitis virus infection, with the levels being of prognostic significance.

Effect of macrophage-derived factor on hypoferraemia induced by Japanese encephalitis virus in mice

Depression of serum iron following Japanese encephalitis virus (JEV) infection was observed in mice. The hypoferraemia was associated with the accumulation of iron in reticulo-endothelial cells in the spleen. Splenectomy (compared with sham-operation) prevented the depression in serum iron concentration after JEV infection. It also prevented the rise in levels of liver iron. The effect of JEV-stimulated, splenic macrophage-derived factor (MDF) was evaluated in causing hypoferraemia. MDF produced a rapid reduction in the serum iron levels with accumulation of iron in spleen. These observations suggest that MDF plays a key role in the regulation of iron metabolism during JEV infection.

Alterations in iron levels in Japanese encephalitis virus infection

Following Japanese encephalitis virus (JEV) infection in mice the serum iron concentration decreased; the decline started from day 3 and persisted up to day 9 postinfection. No significant difference was found in the total iron-binding capacity of serum in JEV-infected mice compared with that of controls. The hypoferraemia was associated with accumulation of iron in the spleen. Large amounts of stainable iron were demonstrated in splenic macrophages from day 5. This was accompanied by transient anaemia. Thus, the hypoferraemia, following intraperitoneal inoculation of JEV, was attributed to a block in the release of iron from the RES.

An epidemic of dengue haemorrhagic fever and dengue shock syndrome in Delhi: a clinical study

Twenty-four cases of dengue haemorrhagic fever/dengue shock syndrome were studied in Delhi in the months of September and October, 1988. The majority of these cases were boys aged 6-10 years. Classical symptoms of dengue (fever, headache, aesthesia, myalgia) occurred in all the patients. Digestive symptoms (nausea, vomiting, anorexia, abdominal pain and hepatomegaly) were also common. Haemorrhagic manifestations were present in 41.7% of the cases. Of these, 90% had gastrointestinal haemorrhages. Shock occurred in 17 cases (70.8%). Thrombocytopenia and prolongation of coagulation profile were found in 62.5% of cases. Three patients (12.5%) who presented with encephalopathy died. The other 21 patients recovered after an average period of 2-8 days.

Immunopathological study of spleen during Japanese encephalitis virus infection in mice

Following intraperitoneal inoculation, Japanese encephalitis virus replicated in peritoneal macrophages, appeared on day 3 in the splenic macrophages of the perifollicular region and later in cells of the periarteriolar lymphoid sheath (PALS) as shown by indirect immunofluorescence. Productive JEV infection was observed both in macrophages and T-cells. Morphological study of spleen during JEV infection revealed proliferative changes, with increased number of macrophages from day 3 p.i. in the perifollicular region followed by accumulation of polymorphonuclear leucocytes which reached a maximum on day 9 p.i. The T dependent areas were considerably enlarged by day 9 and gradually reduced in size by week 3. At later periods germinal centres appeared in the T independent area and were prominent by day 15. The cells containing virus antigen disappeared with the appearance of germinal centres, thus indicating the role of the latter also in virus clearance.