Disentangling specific and unspecific components of innate immune memory in a copepod-tapeworm system

Evidence that the innate immune system can respond with forms of memory upon reinfection has been accumulating over the past few years. These phenomena of "immune priming" in invertebrates, and "trained immunity" in vertebrates, are contrary to previous belief that immune memory and specificity are restricted to the adaptive immune system. However, while trained immunity is usually a response with rather low specificity, immune priming has shown highly specific responses in certain species. To date, it is largely unknown how specificity in innate immune memory can be achieved in response to different parasite types. Here, we revisited a system where an exceptionally high degree of innate immune specificity had been demonstrated for the first time, consisting of the copepod Macrocyclops albidus and its natural parasite, the tapeworm Schistocephalus solidus. Using homologous (same family) vs. heterologous (different family) priming-challenge experiments, we first confirm that copepods exposed to the same parasite family benefit from reduced secondary infections. We further focused on exposed-but-not-infected copepods in primary exposure to employ a transcriptomic approach, distinguishing between immunity that was either specific or unspecific regarding the discrimination between tapeworm types. A weighted gene co-expression network (WGCN) revealed differences between specific and unspecific immunity; while both involved histone modification regulation, specific immunity involved gene-splicing factors, whereas unspecific immunity was primarily involved in metabolic shift. We found a functional enrichment in spliceosome in specific immunity, whereas oxidative phosphorylation and carbon metabolism were enriched in unspecific immunity. Our findings allow discrimination of specific and unspecific components of an innate immune memory, based on gene expression networks, and deepen our understanding of basic aspects of immune systems.

Multiple Nucleocapsid Structural Forms of Shrimp White Spot Syndrome Virus Suggests a Novel Viral Morphogenetic Pathway

White spot syndrome virus (WSSV) is a very large dsDNA virus. The accepted shape of the WSSV virion has been as ellipsoidal, with a tail-like extension. However, due to the scarcity of reliable references, the pathogenesis and morphogenesis of WSSV are not well understood. Here, we used transmission electron microscopy (TEM) and cryogenic electron microscopy (Cryo-EM) to address some knowledge gaps. We concluded that mature WSSV virions with a stout oval-like shape do not have tail-like extensions. Furthermore, there were two distinct ends in WSSV nucleocapsids: a portal cap and a closed base. A C14 symmetric structure of the WSSV nucleocapsid was also proposed, according to our Cryo-EM map. Immunoelectron microscopy (IEM) revealed that VP664 proteins, the main components of the 14 assembly units, form a ring-like architecture. Moreover, WSSV nucleocapsids were also observed to undergo unique helical dissociation. Based on these new results, we propose a novel morphogenetic pathway of WSSV.

Metabolic Alterations in Shrimp Stomach During Acute Hepatopancreatic Necrosis Disease and Effects of Taurocholate on Vibrio parahaemolyticus

Acute hepatopancreatic necrosis disease (AHPND), a recently emerged bacterial shrimp disease, has increased shrimp mortality and caused huge economic losses in many Asian countries. However, molecular factors underlying pathogenesis of this disease remain largely unknown. Our objective was to characterize metabolic alterations in shrimp stomach during AHPND and determine effects of taurocholate on AHPND-causing Vibrio parahaemolyticus. Based on metabolomics, pathways for lipid metabolism and for primary bile acid (BA) synthesis were majorly affected following AHPND infection. Bile acid metabolites, namely taurocholate, were downregulated in the metabolomics database. This prompted us to study effects of taurocholate on biofilm formation, PirAB ^vp toxin release and biofilm detachment capabilities in AHPND-causing V. parahaemolyticus. Treatment of this bacterium with high concentration of taurocholate, a primary bile acid, induced biofilm formation, PirAB ^vp toxin release and facilitated the dispersion of bacterial cells. Taken together, our findings suggest that AHPND infection can affect the lipid metabolites in shrimp stomach, and further suggest that the primary bile acid taurocholate is important for the virulence of AHPND-causing V. parahaemolyticus.

0364 Sex and Race Influence Objective and Self-Report Sleep and Circadian Measures in Emerging Adults at Risk for Bipolar Spectrum Disorder

Introduction

There is a critical need to understand key factors that impact sleep and circadian rhythm function for emerging adults at risk for bipolar spectrum disorder (BSD). Sex and race are common demographic factors contributing to differences in health outcomes; however, the influence of these variables on sleep and circadian rhythm patterns for emerging adults at risk for BSD has not been characterized.

Methods

Multiple objective and self-report facets of sleep and circadian function, including dim light melatonin onset (DLMO), and measures derived from actigraphy and sleep diaries, were assessed in a 20-day ecological momentary assessment (EMA) study of 150 emerging adults (mean ± SD, 21.8 ± 2.1y; 58.7% female; 57.9% White, 23.4% Black, 10.3% Asian or Pacific Islander, 8.0% Other ethnicity) at-risk for BSD. Bivariate Pearson correlations (two-tailed, p <.05) were conducted between the sleep and circadian measures. ANCOVAs, controlling for BSD status, were conducted to evaluate differences on sleep and circadian characteristics by sex and race.

Results

Males exhibited better actigraphic sleep efficiency and later DLMO phase than females, whereas females exhibited more actigraphic discrete sleep periods. White participants exhibited more actigraphy-measured total sleep time, better sleep efficiency, and fewer sleep periods, and self-reported more total sleep time and better sleep efficiency than Black participants.

Conclusion

We show for the first time that sex and race are significant predictors of objective and self-reported sleep and circadian rhythm measures in a large sample of emerging adults at risk for BSD participating in an EMA study. Our findings extend the existing literature to a novel clinical population and to a naturalistic setting and inform ongoing research on sex and racial health disparities in sleep and circadian rhythms.

Support

This work was supported by NIH R01 MH77908 and R01 MH102310; a Banting Postdoctoral Fellowship from the Social Sciences and Humanities Research Council; and a National Science Foundation Graduate Student Research Fellowship.

Penaeus vannamei serine proteinase inhibitor 7 (LvSerpin7) acts as an immune brake by regulating the proPO system in AHPND-affected shrimp

Acute hepatopancreatic necrosis disease (AHPND) is a recently emerged disease in aqua cultured shrimp that is caused by virulent strains of Vibrio parahaemolyticus (VP). Our previous study used transcriptomics to identify key pathogenic factors in the stomach of AHPND-infected shrimp (Litopenaeus vannamei), and here we used a different subset of the same data to construct a gene-to-gene expression correlation network to identify immune-responsive genes. LvSerpin7 was found to have the highest number of correlations after infection, and it also showed a significant increase in mRNA expression. LvSerpin7 is expressed in all tissues but its expression levels are highest in hemocytes. After successfully silencing LvSerpin7 transcript prior to AHPND challenge, mortality was significantly increased relative to the controls and reached 100% within 36 h post infection. Compared to the controls, the phenoloxidase (PO) activity also increased in both hemolymph and stomach. Recombinant LvSerpin7 inhibited shrimp PO activity in vitro, and we also found that rLvSerpin7 inhibited the growth of AHPND-causing bacteria. These results suggest that LvSerpin7 might reduce the toxic effects that result from unregulated activation of the PO defense system by AHPND-causing bacteria.

Dscam in immunity: A question of diversity in insects and crustaceans

In insects and crustaceans, thousands of Down syndrome cell adhesion molecules (Dscam) can be generated by alternative splicing of variable exons from a single-locus gene, Dscam-hv. This extraordinarily versatile gene (38,016 protein isoforms produced in Drosophila) was first proposed to be involved in exon guidance and subsequently implicated in immunity as a hypervariable immune molecule. Almost 20 y after discovery of Dscam-hv, there have been many studies in insects and crustaceans regarding roles of Dscam in immunity, with many similarities and concurrently, many differences. Here, we review the current status of Dscam-hv, presented as a comparison of similarities and differences in insects and crustaceans and discuss hypotheses of Dscam functions in immunity.

Bile acid and bile acid transporters are involved in the pathogenesis of acute hepatopancreatic necrosis disease in white shrimp Litopenaeus vannamei

Acute hepatopancreas necrosis disease is a recently emerged shrimp disease that is caused by virulent strains of Vibrio parahaemolyticus. Although AHPND poses a serious threat to the shrimp industry, particularly in Asia, its underlying pathogenic mechanisms are not well characterized. Since a previous transcriptomic study showed upregulation of the apical sodium bile acid transporter (LvASBT), our objective here was to explore the role of bile acids and bile acid transporters in AHPND infection. We confirmed that mRNA expression of LvASBT was upregulated in the stomach of AHPND-infected shrimps. Bile acid concentrations were also higher in the stomach of AHPND-infected shrimp and correlated with high expression of pVA plasmid and Pir toxins. In vitro assays showed that bile acids enhanced biofilm formation and increased the release of PirAB^vp toxins in AHPND-causing V. parahaemolyticus, while in vivo inhibition of LvASBT by GSK2330672 reduced the copy numbers of pVA plasmid, Pir toxin and reduced the amounts of bile acids in AHPND-infected shrimp stomach. Transcriptomics data for AHPND-causing V. parahaemolyticus treated with bile acids showed upregulation of various genes involved in membrane transport, RND efflux pumps and a bacterial secretion system. Taken together, our results show that AHPND-causing V. parahaemolyticus virulence is positively regulated by bile acids and that LvASBT and bile acids in shrimp stomach have important roles in AHPND pathogenesis.

The gene structure and hypervariability of the complete Penaeus monodon Dscam gene

Using two advanced sequencing approaches, Illumina and PacBio, we derive the entire Dscam gene from an M2 assembly of the complete Penaeus monodon genome. The P. monodon Dscam (PmDscam) gene is ~266 kbp, with a total of 44 exons, 5 of which are subject to alternative splicing. PmDscam has a conserved architectural structure consisting of an extracellular region with hypervariable Ig domains, a transmembrane domain, and a cytoplasmic tail. We show that, contrary to a previous report, there are in fact 26, 81 and 26 alternative exons in N-terminal Ig2, N-terminal Ig3 and the entirety of Ig7, respectively. We also identified two alternatively spliced exons in the cytoplasmic tail, with transmembrane domains in exon variants 32.1 and 32.2, and stop codons in exon variants 44.1 and 44.2. This means that alternative splicing is involved in the selection of the stop codon. There are also 7 non-constitutive cytoplasmic tail exons that can either be included or skipped. Alternative splicing and the non-constitutive exons together produce more than 21 million isoform combinations from one PmDscam locus in the P. monodon gene. A public-facing database that allows BLAST searches of all 175 exons in the PmDscam gene has been established at http://pmdscam.dbbs.ncku.edu.tw/.

Selective expression of a "correct cloud" of Dscam in crayfish survivors after second exposure to the same pathogen

Arthropod hypervariable Dscam (Down syndrome cell adhesion molecule) may be involved in adaptive-like immune characteristics, namely immune priming, enabling the host to "learn" and "remember" pathogens previously encountered in arthropods. However, expression of Dscam in immune-primed arthropods after a second challenge has apparently not been confirmed. Herein, working with Dscam of Australian freshwater crayfish (Cherax quadricarinatus, i.e. CqDscam), we further investigated whether immune priming is mediated by "clouds" of appropriate (or "correct") CqDscam isoforms. In crayfish that survived a first WSSV challenge (immune priming), long-lasting CqDscam expression remained higher after a second WSSV challenge. Selective CqDscam isoforms were also induced after both challenges. Based on pathogen binding assays, these WSSV-induced CqDscam isoforms had a higher WSSV binding ability, perhaps mainly mediated by Ig3-spliced variants. We therefore hypothesized that in these crayfish survivors, an unknown selection process was generating a "correct cloud" of CqDscam against a previously encountered pathogen.

The Rho signalling pathway mediates the pathogenicity of AHPND-causing V. parahaemolyticus in shrimp

An emerging bacterial disease, acute hepatopancreatic necrosis disease (AHPND), is caused by strains of Vibrio parahaemolyticus with an additional AHPND-associated plasmid pVA1 encoding a virulent toxin (Pir^vp ) that damages the shrimp's hepatopancreas. Like other species of Vibrio, these virulent strains initially colonise the shrimp's stomach, but it is not yet understood how the bacteria or toxins are subsequently able to cross the epithelial barrier and reach the hepatopancreas. Here, by using transcriptomics and system biology methods, we investigate AHPND-induced changes in the stomach of AHPND-causing V. parahaemolyticus (5HP)-infected shrimp and identify host molecular mechanisms that might explain how the integrity of the stomach barrier is compromised. We found that the expression of 376 unique genes was differentially regulated by AHPND infection. Gene ontology, protein interaction, and gene-to-gene correlation expression interaction analyses indicated that in addition to the immune system, a number of these genes were involved in cytoskeleton regulation by Rho GTPase. The involvement of Rho pathway regulation during AHPND pathogenesis was further supported by experiments showing that while Rho inhibitor pretreatment delayed the infection, pretreatment with Rho activator enhanced the pathogenicity of 5HP, and both the bacteria and toxin were detected sooner in the hepatopancreas. Further, disruption of the stomach epithelial structure was found in both Rho preactivated shrimp and in 5HP-infected shrimp. Taken together, we interpret our results to mean that Rho signalling helps to mediate AHPND pathogenesis in shrimp.

What vaccination studies tell us about immunological memory within the innate immune system of cultured shrimp and crayfish

The possibility of immunological memory in invertebrates is a topic that has recently attracted a lot of attention. Today, even vertebrates are known to exhibit innate immune responses that show memory-like properties, and since these responses are triggered by cells that are involved in the innate immune system, it seems that immune specificity and immune memory do not necessarily require the presence of B cells and T cells after all. This kind of immune response has been called "immune priming" or "trained immunity". In this report, we review recent observations and our current understanding of immunological memory within the innate immune system in cultured shrimp and crayfish after vaccination with live vaccine, killed vaccine and subunit vaccines. We also discuss the possible mechanisms involved in this immune response.

Using CRISPR/Cas9-mediated gene editing to further explore growth and trade-off effects in myostatin-mutated F4 medaka (Oryzias latipes)

Myostatin (MSTN) suppresses skeletal muscle development and growth in mammals, but its role in fish is less well understood. Here we used CRISPR/Cas9 to mutate the MSTN gene in medaka (Oryzias latipes) and evaluate subsequent growth performance. We produced mutant F0 fish that carried different frameshifts in the OlMSTN coding sequence and confirmed the heritability of the mutant genotypes to the F1 generation. Two F1 fish with the same heterozygous frame-shifted genomic mutations (a 22 bp insertion in one allele; a 32 bp insertion in the other) were then crossbred to produce subsequent generations (F2~F5). Body length and weight of the MSTN-/- F4 medaka were significantly higher than in the wild type fish, and muscle fiber density in the inner and outer compartments of the epaxial muscles was decreased, suggesting that MSTN null mutation induces muscle hypertrophy. From 3~4 weeks post hatching (wph), the expression of three major myogenic related factors (MRFs), MyoD, Myf5 and Myogenin, was also significantly upregulated. Some medaka had a spinal deformity, and we also observed a trade-off between growth and immunity in MSTN-/- F4 medaka. Reproduction was unimpaired in the fast-growth phenotypes.

Pathogenesis of acute hepatopancreatic necrosis disease (AHPND) in shrimp

Acute hepatopancreatic necrosis disease (AHPND), also called early mortality syndrome (EMS), is a recently emergent shrimp bacterial disease that has resulted in substantial economic losses since 2009. AHPND is known to be caused by strains of Vibrio parahaemolyticus that contain a unique virulence plasmid, but the pathology of the disease is still unclear. In this study, we show that AHPND-causing strains of V. parahaemolyticus secrete the plasmid-encoded binary toxin PirAB(vp) into the culture medium. We further determined that, after shrimp were challenged with AHPND-causing bacteria, the bacteria initially colonized the stomach, where they started to produce PirAB(vp) toxin. At the same early time point (6 hpi), PirB(vp) toxin, but not PirA(vp) toxin, was detected in the hepatopancreas, and the characteristic histopathological signs of AHPND, including sloughing of the epithelial cells of the hepatopancreatic tubules, were also seen. Although some previous studies have found that both components of the binary PirAB(vp) toxin are necessary to induce a toxic effect, our present results are consistent with other studies which have suggested that PirB(vp) alone may be sufficient to cause cellular damage. At later time points, the bacteria and PirA(vp) and PirB(vp) toxins were all detected in the hepatopancreas. We also show that Raman spectroscopy "Whole organism fingerprints" were unable to distinguish between AHPND-causing and non-AHPND causing strains. Lastly, by using minimum inhibitory concentrations, we found that both virulent and non-virulent V. parahaemolyticus strains were resistant to several antibiotics, suggesting that the use of antibiotics in shrimp culture should be more strictly regulated.

Reprint of "review of Dscam-mediated immunity in shrimp and other arthropods"

Although true adaptive immunity is only found in vertebrates, there is increasing evidence that shrimp and other arthropods exhibit immune specificity and immune memory. The invertebrate immune response is now called "innate immunity with specificity" or "immune priming", and its underlying mechanisms are still unclear. However, while vertebrate antibodies have no invertebrate homolog, the Down syndrome cell adhesion molecule (Dscam), which is a hypervariable protein created by alternative splicing, can function as a pathogen-specific recognizing molecule in arthropods. Here we review our current understanding of the Dscam-mediated immune responses in arthropods, especially in shrimp, and show that Dscam may be involved in both general innate immunity and the pathogen-specific immune response.

The DNA fibers of shrimp hemocyte extracellular traps are essential for the clearance of Escherichia coli

Extracellular traps (ETs) are a part of the vertebrate immune response that was only recently discovered. These structures are formed in response to pathogenic invasion and they act to kill the invader. Vertebrate ETs are composed of chromosomal DNA, histone proteins and other antimicrobial cytoplasmic proteins. Pathogenic stimulation was also recently shown to trigger a similar ET response in shrimp hemocytes, and in the present study, we evaluate the role of the DNA fibers in the bactericidal properties of these invertebrate ETs. When the formation of shrimp ETs was disrupted by DNase I, the ETs anti-bacterial activity was also reduced, indicating that the DNA fibers are important for ET-mediated bacterial clearance. We also found that at high bacterial densities, shrimp ETs were a more effective anti-bacterial response than phagocytosis.

Review of Dscam-mediated immunity in shrimp and other arthropods

Although true adaptive immunity is only found in vertebrates, there is increasing evidence that shrimp and other arthropods exhibit immune specificity and immune memory. The invertebrate immune response is now called "innate immunity with specificity" or "immune priming", and its underlying mechanisms are still unclear. However, while vertebrate antibodies have no invertebrate homolog, the Down syndrome cell adhesion molecule (Dscam), which is a hypervariable protein created by alternative splicing, can function as a pathogen-specific recognizing molecule in arthropods. Here we review our current understanding of the Dscam-mediated immune responses in arthropods, especially in shrimp, and show that Dscam may be involved in both general innate immunity and the pathogen-specific immune response.

WSSV-induced crayfish Dscam shows durable immune behavior

One of the major gaps in our understanding of arthropod specific immune priming concerns the mechanism[s] by which the observed long-term (>2 weeks) protective effects might be mediated. Hypervariable Dscam (Down syndrome cell adhesion molecule) might support arthropod innate immunity with specificity for more extended periods. We show here that, in the relatively long-lived arthropod Cherax quadricarinatus, CqDscam does not behave like a typical, immediately-acting, short-lived innate immune factor: CqDscam was not induced within hours after challenge with a lethal virus, but instead was only up-regulated after 2-5 days. This initial response faded within ∼ 2 weeks, but another maximum was reached ∼ 1 month later. At around 2 months after the initial challenge, the virus-induced CqDscam bound to the virus virion and acted to neutralize the virus However, although CqDscam helped crayfish to survive during persistent infection, it nevertheless failed to provide any enhanced protection against a subsequent WSSV challenge. Thus, CqDscam is capable of supporting extended anti-virus immune memory in arthropods. Also, during a persistent virus infection, the balance of "immune firepower" in crayfish appears to be altered such that the general immune factors become depleted while CqDscam becomes relatively predominant.

Monitoring treatment response in sputum smear positive pulmonary tuberculosis patients: comparison of weight gain, sputum conversion and chest radiograph

BACKGROUND

Monitoring treatment response to anti-tuberculous therapy remains unsatisfactory in resource-limited countries where sophisticated and expensive tests are not readily available. Sputum culture for mycobacterium is desirable, but not obtainable in many developing countries. Sputum acid-fast bacilli (AFB) smear alone can be misinterpreted in the presence of unviable bacilli or non-tuberculous mycobacteria. Hence the search for a cheaper but reliable monitoring tool, or a combination of several tools, continues. Interesting reports from studies in third world nations have considered weight gain/loss as one such monitoring tool. Since pulmonary tuberculosis is endemic in this country, we take the opportunity to evaluate weight gain and chest radiograph, compared to sputum AFB smear in monitoring patient's response.

METHODS

This was a retrospective study of confirmed positive sputum AFB smear patients from January 1999 to December 2004 who attended the Chest Clinic at Hospital Tengku Ampuan Afzan, Kuantan, Malaysia. Data on weight, chest radiograph and sputum AFB smear from initiation of therapy to end of treatment and follow-up were collected and analyzed.

RESULTS

201 patients were included. At week-4 of anti-tuberculous treatment, only 14.7% had positive sputum smear. At completion of therapy 93.1% had improved chest radiographs. 90% had weight gain, 5% had weight loss and the remaining had no change in weight. Amongst patients with weight loss, there were no significant differences in the underlying illnesses (p=0.376), sputum smear at 4 weeks (p=0.697) and chest X-ray changes (p=0.731). Three patients who initially showed sputum smear conversion had reappearance of positive smear results towards the end of treatment. One of them was diagnosed as treatment failure while the other two remained well after discontinuation of therapy.

CONCLUSION

Weight gain is very common among smear-positive tuberculosis patients after treatment even though weight gain does not correlate well with underlying disease, sputum conversion and chest X-ray changes. Reappearance of smear-positive sputum must be interpreted with caution and not to be regarded as treatment failure without other evidence.

An invertebrate Warburg effect: a shrimp virus achieves successful replication by altering the host metabolome via the PI3K-Akt-mTOR pathway

In this study, we used a systems biology approach to investigate changes in the proteome and metabolome of shrimp hemocytes infected by the invertebrate virus WSSV (white spot syndrome virus) at the viral genome replication stage (12 hpi) and the late stage (24 hpi). At 12 hpi, but not at 24 hpi, there was significant up-regulation of the markers of several metabolic pathways associated with the vertebrate Warburg effect (or aerobic glycolysis), including glycolysis, the pentose phosphate pathway, nucleotide biosynthesis, glutaminolysis and amino acid biosynthesis. We show that the PI3K-Akt-mTOR pathway was of central importance in triggering this WSSV-induced Warburg effect. Although dsRNA silencing of the mTORC1 activator Rheb had only a relatively minor impact on WSSV replication, in vivo chemical inhibition of Akt, mTORC1 and mTORC2 suppressed the WSSV-induced Warburg effect and reduced both WSSV gene expression and viral genome replication. When the Warburg effect was suppressed by pretreatment with the mTOR inhibitor Torin 1, even the subsequent up-regulation of the TCA cycle was insufficient to satisfy the virus's requirements for energy and macromolecular precursors. The WSSV-induced Warburg effect therefore appears to be essential for successful viral replication.

The Warburg effect (or aerobic glycolysis) is a metabolic shift that was first found in cancer cells, but has also recently been discovered in vertebrate cells infected by viruses. The Warburg effect facilitates the production of more energy and building blocks to meet the enormous biosynthetic requirements of cancerous and virus-infected cells. To date, all of our knowledge of the Warburg effect comes from vertebrate cell systems and our previous paper was the first to suggest that the Warburg effect may also occur in invertebrates. Here, we use a state-of-the-art systems biology approach to show the global metabolomic and proteomic changes that are triggered in shrimp hemocytes by a shrimp virus, white spot syndrome virus (WSSV). We characterize several critical metabolic properties of the invertebrate Warburg effect and show that they are similar to the vertebrate Warburg effect. WSSV triggers aerobic glycolysis via the PI3K-Akt-mTOR pathway, and during the WSSV genome replication stages, we show that the Warburg effect is essential for the virus, because even when the TCA cycle is boosted in mTOR-inactivated shrimp, this fails to provide enough energy and materials for successful viral replication. Our study provides new insights into the rerouting of the host metabolome that is triggered by an invertebrate virus.

Shrimp hemocytes release extracellular traps that kill bacteria

Extracellular traps (ETs) are formed from the DNA, histones and cytoplasmic antimicrobial proteins that are released from a range of vertebrate immune-cells in response to pathogenic stimulation. This novel defense mechanism has not been demonstrated in invertebrates. In this study, we investigated the formation of ETs in the crustacean Litopenaeus vannamei. We found that stimulation of shrimp hemocytes with phorbol myristate acetate (PMA), lipopolysaccharide (LPS) and live Escherichia coli all led to the formation of the characteristic ET fibers made from host cell DNA. After E. coli stimulation, we found that histone proteins were co-localized with these extracellular DNA fibers. The results further showed that E. coli were trapped by these ET-like fibers and that some of the trapped bacteria were permeabilized. All of these results are characteristic of the ETs that are seen in vertebrates and we therefore conclude that shrimp are also capable of forming extracellular traps.

Properties of Litopenaeus vannamei Dscam (LvDscam) isoforms related to specific pathogen recognition

Arthropod Down syndrome cell adhesion molecules (Dscam) may sometimes function as hypervariable pathogen recognition receptors. They consist of an extracellular region and a cytoplasmic tail, both of which are highly variable. In shrimp, tail-less Dscam proteins (Dscams) have recently been identified, and these appear to be unlike other arthropod extracellular Dscams that are released from the cell membrane by proteolytic cleavage. Here we investigate the properties of these unique shrimp proteins and show that they can be directly secreted from transfected cells. We also investigate the diverse cytoplasmic tail variants of membrane-bound shrimp Dscams, and show that elements E1A and E3 seem to be related to Dscam immune function. Challenge with Vibrio harveyi not only enhanced total Dscam and the immune-related cytoplasmic tail variants, but also induced expression of certain Ig2 + Ig3 combinations. A pathogen binding assay with these Ig2 + Ig3 extracellular variants showed that both the V. harveyi-induced Dscams and Dscams induced by buffer injection could be either pathogen-specific or specific only for Gram-negative pathogens, while other "general" Dscam variants were sensitive to a wide range of pathogens. The same assay also suggested that shrimp Dscam isoforms show a stronger response to the host's natural pathogens.

Defaulters among lung cancer patients in a suburban district in a developing country

INTRODUCTION

This study was carried out to determine the prevalence, patient's characteristic and reasons for defaulting follow-up and treatment among patients with lung cancer.

METHODS

Patients with histologically confirmed lung cancer were recruited. Patient's detailed demographic data, occupation, socioeconomic status, and educational level of both the patients and their children were recorded. Defaulters were classified as either intermittent or persistent defaulters. By using Chi-square test, defaulter status was compared with various demographic and disease characteristic factors. The reasons for default were determined.

RESULTS

Ninety five patients were recruited. Among them, 81.1% patients were males; 66.3% were Malays. The mean age (SD) was 60 ± 10.5 years. About 46.3% of the patients had Eastern Cooperation Oncology Group (ECOG) functional status 0/1 and 96.8% of the patients presented with advanced stage (Stage 3b or 4). Overall, 20 patients (21.1%) were defaulters (35.0% intermittent defaulters; 65.0% persistent defaulters). Among the intermittent defaulters, 8 patients defaulted once and one patient defaulted 3 times. Among the 20 defaulters, only 2 (10%) patients turned up for the second follow-up appointment after telephone reminder. Two main reasons for default were 'too ill to come' (38.5.5%) and logistic difficulties (23.1%). No correlation was found between patient education, children education, income, ECOG status, stage of the disease, race, and gender with the defaulter rate.

CONCLUSION

Defaulter rate among lung cancer patients was 21.1%. Children education level is the only significant factor associated with the defaulter rate.

The use of multiplex real-time PCR improves the detection of the bacterial etiology of community acquired pneumonia

Community-acquired pneumonia (CAP) is still a major cause of morbidity and mortality especially to children and compromised hosts, such as the old and those with underlying chronic diseases. Knowledge of pathogens causing CAP constitutes the basis for selection of antimicrobial treatment. Previous data have shown that etiological agents can be identified in only up to 50% of patients, but this figure can be improved by using polymerase chain reaction (PCR). This study was designed to evaluate multiplex real-time PCR as a method for rapid differential detection of five bacterial causes of CAP (Streptococcus pneumoniae, Burkholderia pseudomallei and atypical bacterial pathogens namely Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella pneumophila) in CAP patients attending Hospital Tengku Ampuan Afzan (HTAA)/ Kuantan, Pahang, Malaysia. Two previously developed multiplex real-time PCR assays, duplex for the differential detection of S. pneumoniae and B. pseudomallei and triplex for the atypical bacterial pathogens, were used to detect a bacterial cause of CAP in blood and respiratory samples. Thus, 46 blood and 45 respiratory samples collected from 46 adult CAP patients admitted to HTAA were analysed by multiplex real-time PCR assays and conventional methods. The microbial etiology of CAP could be established for 39.1% (18/46) of CAP patients by conventional methods and this was increased to 65.2% (30/46) with the additional use of real-time PCR. The most frequently detected pathogens were S. pneumoniae (21.7% - all by PCR alone), Klebsiella pneumoniae (17.3%), B. pseudomallei (13% - 83% of them positive by PCR alone and 17% by both culture and PCR), Pseudomonas aeruginosa (6.5%), M. pneumoniae (6.5% - all by serology), C. pneumoniae (4.3% - all positive by both PCR and serology), L. pneumophila (2.1% - all by PCR alone), Escherichia coli (4.3%). Haemophilus infuenzae, Acinetobacter lwoffii and Acinetobacter baumannii were detected by conventional methods (2.1% for each).

The bug and the big heart --melioidotic pericardial effusion

Melioidosis is an infection caused by Gram negative bacterium Burkholderia pseudomallei leading to abscesses in lungs, liver, spleen, musculoskeletal system, prostate and sepsis. We present a rare case of purulent pericardial effusion caused by melioidosis with concomitant pneumonia and splenic abscesses. The patient underwent pericardiocentesis and successfully recovered from cardiogenic and septic shock.

The introduction, origin and life-history attributes of the non-native cichlid Etroplus suratensis in the coastal waters of Singapore

Etroplus suratensis, a southern Asian cichlid, has established populations in Singapore. The fish, which was first collected in 1995, was probably introduced via the aquarium trade or through the Johor River in Malaysia. The growth, feeding and reproductive characteristics were found to follow its ecology in its native range in southern Asia, and its establishment in Singapore could be due to the similarity in environment and availability of food. Changes in intestinal length indicated diet shifts from a predominantly herbivorous to an omnivorous one as it matured. Stomach contents did not provide comparable evidence. Diet similarity to two other introduced cichlids may imply that interspecies resource competition exists. Closer monitoring is needed to determine its effects on the local environment.

The man with the boggy head: cranial melioidosis

Melioidosis is known to cause abscesses in various organs, including the cranium, though less commonly. We present a patient with scalp abscess and subdural empyema that was visible on computed tomography of the brain. The neurosurgical drainage grew Burkholderia pseudomallei. Despite our best effort to treat the patient using parenteral antibiotics and surgical drainage, the patient did not survive.

A mimicry of melioidosis by Klebsiella ozaenae infection

Klebsiella ozaenae is a Gram negative bacillus. It has been described as a colonizer of oral and nasopharyngeal mucosa and is a cause of atrophic rhinitis. Klebsiella ozaenae has seldom been isolated from serious infections. However, several reports have stated that Klebsiella ozaenae may cause invasive infections and even mortality. We report a 55-year-old man with Klebsiella ozaenae infection causing abscesses involving the right eye and left kidney and possibly also in the brain, lungs and prostate. The isolates were sensitive to ceftazidime, ciprofloxacin, chloramphenicol, gentamicin and sulfamethoxazole-trimethoprim but resistant to ampicillin. He responded well to 4 weeks of i.v. ceftazidime and i.v. amoxycillin-clavulanic acid. To our knowledge, such a multiorgan infection has not been reported previously for this organism.

Melioidotic prostatic abscess in Pahang

Melioidosis is caused by Burkholderia pseudomallei, a Gram-negative bacillus. Melioidosis can affect many organs, including the prostate. However, prostatic abscess due to melioidosis is uncommon. We describe five cases of melioidosis with prostatic abscess. Four of five patients had diabetes mellitus and had more than one organ involvement. The diagnosis of prostatic abscess in our patients was only made with computed tomography of the abdomen and pelvis. None of our patients underwent surgical drainage and all remained well after treatment with antibiotics, except for one mortality secondary to severe septicaemia.

Pahang melioidosis registry

Melioidosis has a high annual incidence and mortality rate in Pahang, Malaysia. We initiated the first melioidosis registry in the country on 1st July 2005 to improve the management of melioidosis in the state. Continuous medical education on melioidosis was carried out in all hospitals in the state to highlight the magnitude of the disease and to educate the doctors on the treatment of the disease. All culture confirmed cases were registered and analysed. During the one-year study period from 1st July 2005 till 30th June 2006, a total of 63 patients had positive culture for Burkholderia pseudomallei. The calculated annual incidence of melioidosis in Pahang state was 4.3 per 100,000 population per year (Adult, 6.0 per 100, 000 population per year and paediatric, 1.6 per 100,000 population per year). There were 55 Malays (87.3%), three Chinese (4.8%), four aborigines (6.3%) and one Indonesian. Nine (14.3%) were less than 18 years old. The median age was 49 years (range: 1-68 years). Only one patient (1.6%) had a previous history of confirmed melioidosis. With this programme, we had observed a decline in adult mortality from 54% to 44%, although this was not statistically significant. However, culture-confirmed relapses had dropped from 19% to nil. Several measures need to be taken to decrease mortality from melioidosis in endemic countries.

An unusual cause of haemoptysis and headache: cryptococcosis

Pulmonary cryptococcosis can be clinically silent in non-HIV infected patients but can also present as nodules and masses on the chest radiograph, which can be mistaken for tuberculosis or lung cancer. Common symptoms include fever and cough, and uncommonly haemoptysis. This report illustrates a non-HIV infected patient whose main complaint was haemoptysis and headache. He was diagnosed with pulmonary cryptococcosis from biopsy of an endobronchial mass found on flexible bronchoscopy. Disseminated cryptoccoccal infection should be considered as a differential diagnosis in non-HIV infected patients presenting with haemoptysis and headache. Early recognition and administration of appropriate therapy will improve clinical outcome in these patients.

Medical thoracoscopy: Pahang experience

Medical thoracoscopy has gain its popularity in Malaysia recently. This paper presents our early experience in thoracoscopy using semi-rigid fiberoptic thoracoscope. All thoracoscopy records since October 2006 were retrieved. The patients' records, thoracocentesis investigations results, thoracoscopic findings and all pleural biopsy results were reviewed. Twenty-four thoracoscopic procedures on 22 patients in whom two patients had repeated thoracoscopy. Ten patients were confirmed carcinoma. Eight patients had inconclusive thoracoscopic pleural biopsy results. Three patients underwent pleurodesis for malignant effusion. One patient had adhesiolysis for empyema. There was no procedure-related deaths or intraoperative accidents. Thoracoscopy is a relatively safe procedure.

Transbronchial needle aspiration of mediastinal lymph node

In Malaysia, transbronchial needle aspiration (TBNA) is a relatively new procedure performed only in a handful of respiratory centres. We reviewed TBNA of mediastinal lymph node performed in Hospital Tengku Ampuan Afzan (HTAA) to determine the yield and its complications. Data was retrieved from endoscopy databases and patients' records, CT thorax images and all cytological and histological slides were reviewed. Twenty-five patients had TBNA performed. TBNA was positive in 15 patients (60%). Overall, 80% had confirmed malignancy after bronchoscopy. Only four patients had documented bleeding after TBNA and in two of them, bleeding stopped spontaneously and another two patients required diluted adrenaline to stop the bleed. No mortality was reported from this procedure. Hence, TBNA is a safe procedure.

Transbronchial needle aspiration of mediastinal lymph node

In Malaysia, transbronchial needle aspiration (TBNA) is a relatively new procedure performed only in a handful of respiratory centres. We reviewed TBNA of mediastinal lymph node performed in Hospital Tengku Ampuan Afzan (HTAA) to determine the yield and its complications. Data was retrieved from endoscopy databases and patients' records, CT thorax images and all cytological and histological slides were reviewed. Twenty-five patients had TBNA performed. TBNA was positive in 15 patients (60%). Overall, 80% had confirmed malignancy after bronchoscopy. Only four patients had documented bleeding after TBNA and in two of them, bleeding stopped spontaneously and another two patients required diluted adrenaline to stop the bleed. No mortality was reported from this procedure. Hence, TBNA is a safe procedure.

The urine bag used in pneumothorax

Pneumothorax is the presence of air in the pleural cavity. It can be classified into spontaneous, traumatic or iatrogenic. The majority of pneumothorax cases are spontaneous, which can be further classified into primary spontaneous pneumothorax (PSP) or secondary spontaneous pneumothorax (SSP), defined by the absence or presence of obvious underlying lung disease respectively. The treatment of spontaneous pneumothorax includes simple aspiration, intercostal tube drainage or surgical intervention. When intercostal tube drainage is used, it is usually attached to an underwater-seal system. Mobile chest drains, such as the Heimlich valve, replace the underwater-seal and allow outpatient management of spontaneous pneumothoraces. The Heimlich valve however, is costly and not readily available in many local hospitals. Cheaper and easily obtainable alternatives which are also safe are being sought. This is a case report describing the use of the urine bag in the management of a patient with spontaneous pneumothrax.

Implantation of a nerve ending into a vein

Neuromas can be painful and physically and psychologically disabling. Among the many methods of treatment available, translocation away from noxious stimuli, such as implantation in muscle or bone, has been used. Veins are easily available and accessible to nerves. The outcome of a nerve ending implanted into a vein and the effects of the implanted nerve on the vein have not been studied. This study evaluated neuroma prevention with a new technique that involves implanting a nerve ending into a vein. The medial branches of the right femoral nerve of 20 rats were transected at midthigh level. The distal segments were excised. The proximal segments were implanted into the femoral vein. The epineurium was sutured to the tunica adventitia using interrupted 10-0 Ethilon sutures. The left side served as controls where the proximal nerve stumps were left lying in their beds. The animals were sacrificed 12 weeks after the operation. Histologic analysis of 12 controls showed neuromas. Twelve implanted nerves showed neuromas that were smaller than those of the controls. The difference was statistically significant. The regenerated nerve fibers were found within the adventitia and muscular wall of the vein. There was no extension of nerve tissue into the vessel lumen and no thrombosis of the vein. Electron microscopic study on the other eight rats showed abnormal large myelinated fibers in the controls and in the implanted nerves. The fibers in the implanted group were degenerated.

A non-invasive isotope dilution technique for quantifying hepatic blood flow using radiolabelled red blood cells

Clinically significant changes in hepatic haemodynamics accompany the development of portal hypertension, hepatocellular carcinoma, liver metastases and liver cirrhoses, and after major liver resection. Hepatic blood flow parameters, such as hepatic arterial flow (HAF), hepatic portal flow (HPF), total hepatic blood flow (THBF) and hepatic perfusion index (HPI), are useful adjuncts to the diagnosis of liver pathology, the evaluation of disease progress and prognostication. Here, we describe a non-invasive method that combines the measurement of these parameters in a single study in real time. Red blood cells from eight pigs were labelled with 99Tc(m) using an in-vitro method and re-injected into the pigs. Data acquisition over the heart, lungs, liver and kidneys was started immediately and a blood sample was obtained 15 min post-injection. Hepatic arterial flow was determined from the ratio of the maximum gradients between the integrated time-activity curve of the left ventricle and the first-pass time-activity curve of the liver before the peak of the kidneys time-activity curve. The hepatic perfusion index was determined by comparing the slope of the liver time-activity curve before and after the kidney peak. Hepatic portal flow was determined from the hepatic arterial flow and the hepatic perfusion index, and total hepatic blood flow was determined as the sum of arterial and portal flow. The results were compared against those obtained from a clearance method using 99Tc(m)-DISIDA. The average hepatic perfusion index was 0.38, and the average hepatic arterial flow and hepatic portal flow were 168.3 +/- 52.9 and 274.6 +/- 60.1 ml x min(-1) respectively. The average total hepatic blood flow was 442.8 +/- 53.5 ml x min(-1), while the total hepatic flow determined by 99Tc(m)-DISIDA clearance was 419.7 +/- 62.6 ml x min(-1). No significant difference in total hepatic blood flow was found between the two methods. The results of this study show that it is possible to obtain all hepatic haemodynamics data in a single study using a non-invasive method.

Influence of respiration and portal pressure on transabdominal duplex Doppler ultrasound measurement of portal blood flow: a porcine model for experimental studies

Transabdominal duplex Doppler ultrasonography (TDDU) is commonly used for measuring hepatic blood flow (HBF) in clinical practice. Flow velocity and the cross-sectional area (CSA) of vessels are obtained separately and used to compute blood flow. Respiration and changes in portal pressure are known to cause variations in the CSA of the portal vein, but the impact of these parameters on TDDU measurement of portal blood flow is unclear. Eight Yorkshire pigs (20.7-25.1 kg) were used for the study. TDDU determination of portal blood flow was carried out using CSA of the portal vein obtained at inspiration (maximal) and at expiration (minimal) for computation, and the differences obtained were compared. Determination of HBF was carried out simultaneously on the same animals using diisopropyliminodiacetic acid (DISIDA) clearance. A physiological increase in portal pressure was then created by 50% hepatectomy and TDDU measurement similarly carried out on the second postoperative day. Computing portal blood flow in the intact liver using maximal and minimal CSA gave rise to a mean difference of 7.0 ml kg(-1) min(-1) (P < 0.001). A significant correlation was obtained between HBF and portal flow computed from maximal CSA (Pearson's correlation = 0.85, P < 0.033). The respiratory index of the portal vein (maximal CSA/minimal CSA) decreased from 1.5 to 1.2 after hepatectomy, which also caused a 90% increase in portal pressure. Respiration and portal pressure thus significantly impact on TDDU determination of HBF, and in this porcine model, computation using maximal CS more accurately reflects HBF.

End-to-side anastomosis of transected nerves to prevent neuroma formation

Neuroma can be painful and physically and psychologically disabling. Among the many methods of treatment available, one of the more successful is centrocentral nerve union with an autologous graft. However, it cannot be used in small nerves that lack two fascicles. This study evaluated neuroma prevention in an end-to-side anastomosis, a new technique applicable to all nerves. The lateral branch of the right sciatic nerve in 20 rats was transected at the midthigh level. The proximal segment was looped back to the main nerve and an end-to-side epineural anastomosis was performed. The lateral branch of the left sciatic nerve was transected to serve as a control, and the proximal nerve stump was closed by interrupted epineural sutures. The animals were sacrificed 12 weeks after the operation. Histologic analysis of specimens from the 12 controls showed neuroma formation. Specimens from 12 side-to-end anastomoses contained regenerated nerve tissues and formed smaller masses compared with that of the controls. The regenerated tissues at the anastomoses were orientated more orderly than were tissues from the controls in 75% of cases. The differences were statistically significant. Electron microscopic study on specimens from the remaining eight controls showed the presence of abundant large abnormal myelinated fibers (10-15 microns) with thick irregular myelin sheaths scattered among smaller myelinated fibers (2-10 microns) that had thin myelin sheaths. In the remaining eight end-to-side anastomoses, large abnormal myelinated fibers were absent. The myelinated fibers were 2 to 10 microns in diameters and had a normal appearance with thin myelin sheaths. End-to-side anastomosis formed a smaller mass of regenerated nerve tissues. Ultrastructurally they were formed better and orientated more orderly resembling normal nerve.

Pigmented central neurocytoma: case report and literature review

A case of pigmented central neurocytoma is reported. The tumor showed histologic, immunophenotypic, and ultrastructural features of central neurocytoma. The pigment consisted of an intimate association of lipofuscin and neuromelanin. Pigmented neuroepithelial tumors are rare, and the pigments may be neuromelanin or melanin. Pigmented central neurocytoma has not been described to date. The low proliferation rate of the tumor suggests a delayed turnover of tumor cells as a possible cause of lipofuscin accumulation. Autocatalytic peroxidation of lipofuscin is a possible mechanism of neuromelanin formation.

A simple method of blood pressure measurement in the pig using a neonatal cuff

The pig is a commonly used large animal model in experimental studies. Few non-invasive techniques exist however for the measurement of blood pressure in the porcine model. This study evaluates the novel use of the easily available neonatal blood pressure cuff for measuring blood pressure in the pig. Six Yorkshire pigs were used for the study. Blood pressure measurements obtained by the application of neonatal blood pressure cuff (Hewlett Packard) around the base of the tail were compared with results obtained from intra-arterial measurements in the normotensive range as well as in experimentally created hypertensive (intravenous dopamine) and hypotensive (hypovolaemic shock) ranges. Results of the two techniques are closely correlated (Pearson's coefficient = 0.95, 0.97, 0.90). Systematic bias was however detected at the extremes of hypertensive and hypotensive blood pressure. Analysis of the limits of agreement (method of Bland and Altman) showed that neonatal blood pressure cuff measurements fall within--2 to 2.5 mmHg of the readings obtained from the invasive technique (95% confidence interval). The neonatal blood pressure cuff technique is a good substitute for the standard invasive intra-arterial measurement of blood pressure in the pig model.

A practical technique of colour image analysis: applications in experimental research

Commercially available colour image analysers are relatively expensive. We describe a cheaper alternative developed by the Department of Experimental Surgery, Singapore General Hospital using an assembly of optical and computer equipment commonly available in the research laboratory. This manual colour imaging system is comparable to the commercial model in terms of functional capabilities and accuracy, except that it takes a longer time to process and analyse images and is unable to measure colour density. However, it is capable of not only analysing microscopic images of stained histological tissue sections but also X-ray images and images of large pathological specimens. In the case of commercial models, different systems have to be used to analyse images from different types of specimens. This system was developed in 1987 and has since been used successfully in a number of experimental studies. It has been applied to the measurement of parameters defining eye anatomical configuration, delineating the extent of tissue necrosis and fibrosis after therapeutic treatment and surgery, the development of new bone formation in fracture healing and to quantitative studies in liver regeneration. Due to its accuracy, low cost and versatility, this system should be within the means of even the most modest research laboratory.

Optimal flexible designs in phase II clinical trials

In the conduct of a phase II cancer clinical trial, patients usually enter in two stages. If the response rate from the first stage is low, then the study terminates. Within various two-stage designs, Simon proposed the optimal and minimax criteria. In the co-operative group setting, practical considerations make it difficult to arrive at the planned sample size exactly. Green and Dahlberg proposed and compared several flexible designs. In this paper, we explicitly define a flexible design as a collection of two-stage designs where the first stage size is in a set of consecutive values (n1, ..., nk) and the second stage size is also in another set of consecutive values (N1, ..., Nk), and each of k2 possible designs has the same probability of occurrence. We apply Simon's optimal and minimax criteria to flexible designs for phase II trials in order to minimize the number of patients tested on an ineffective drug.

Short segment Barrett's oesophagus: prevalence, diagnosis and associations

BACKGROUND

Prevalence of short segment Barrett's (SSB) oesophagus, defined as the absence of macroscopic Barrett's but histologically identifiable intestinal metaplasia, has been reported to be 18% based on haematoxylin and eosin (H&E) staining.

AIMS

To define the prevalence of SSB oesophagus using H&E and alcian blue staining and to determine whether SSB oesophagus is associated with inflammation at the gastro-oesophageal junction (GOJ).

SUBJECTS

Consecutive patients (n = 158) presenting for endoscopy completed a structured interview.

METHODS

Two biopsy specimens taken from the GOJ were stained with H&E, alcian blue and Giemsa. A third specimen was obtained from the distal oesophagus. Intestinal metaplasia was diagnosed if goblet cells were definitely identified by two independent observers.

RESULTS

SSB oesophagus was present in 46 (prevalence 36%, 95% confidence interval (CI) 28.5-43.5) using alcian blue staining. If H&E had been the sole staining method used, 50% cases of intestinal metaplasia would have been overlooked. There were no cases of intestinal metaplasia identified by H&E but missed by alcian blue staining. Logistic regression analysis identified age (odds ratio (OR) per decade 1.03, 95% CI 1.01-1.06), histological oesophagitis (OR 3.2, 95% CI 1.4-7.2) and inflammation at the gastrooesophageal junction (OR 5.9, 95% CI 2.2-15.6) as independent risk factors for SSB oesophagus.

CONCLUSION

Unrecognised SSB oesophagus is highly prevalent in patients presenting for diagnostic upper endoscopy if alcian blue staining is applied.

Evaluation of recommendations for replication-competent retrovirus testing associated with use of retroviral vectors

With input from the gene therapy community, CBER is actively examining the recommendations for RCR testing during retroviral vector production, production of ex vivo-transduced cells, and in patients who receive such material. Our initial recommendations were made at a time when our experience with RCR detection assays and clinical use of retroviral vectors was limited. As the gene therapy field has matured, there is an increasing amount of data available on RCR detection assays and from monitoring of patients in clinical trials. The cumulative data give assurance that RCR detection assays in use are of sufficient sensitivity to provide a margin of safety to patients: no patients to date have evidence of RCR infection. However, CBER encourages members of the gene therapy community to continue to submit data to the FDA or to publish data that will enhance the cumulative data base on RCR testing assays, experience with different VPC, and patient monitoring. Based on the analysis of data accumulated to data, and ongoing discussions with members of the gene therapy community, CBER is proposing to discuss changes to the current RCR testing recommendations, as summarized below. RCR testing during production of retroviral vector and ex vivo-transduced cells. Development of characterized standards for RCR testing of supernatant and cells should allow comparison of assay sensitivity. One proposal under consideration is to apply statistical methods to determine how much material needs to be tested independent of the size of the production lot. Data and discussion are still needed to define a limit concentration and a value for probability of detection for RCR testing, while maintaining an appropriate margin of safety. These modifications of RCR testing strategies could lead to improvements in assay sensitivity. Additional discussion and data are also needed to evaluate the current recommendations of the testing for ex vivo-transduced cells: should both cells and supernatant be tested in all cases? RCR testing during patient follow-up. The time points required for RCR testing during patient follow-up need examination. One proposal under consideration is to sample and assay at three time points during the first year of treatment (e.g., 4-6 weeks, 3 months, and 1 year post-treatment). Further discussion is needed to define appropriate additional follow-up. Choice of assays to detect surrogate markers for RCR infection (i.e., serologic or PCR-based assays) should consider mode of vector administration and the patient population. Positive results with such assays should be pursued by direct culture assay to obtain and characterize the infectious viral isolate. These proposals will be the focal point for the discussion at the Retroviral Vector Breakout Session at the 1997 FDA/NIH Gene Therapy Conference. After the 1997 FDA/NIH Gene Therapy Conference, CBR plans to propose revised recommendations for RCR testing for public comment.

Increased drug reactions in HIV-1-positive patients: a possible explanation based on patterns of immune dysregulation seen in HIV-1 disease. The Military Medical Consortium for the Advancement of Retroviral Research (MMCARR)

Drug reactions are common in HIV-1 disease, with the incidence having been reported to increase with increasing stage and with CD4+ T-cell counts below 200/microliters. However, there have been numerous reports of patients in which rechallenge, dosing changes or continued therapy have resulted in no recurrence or else clearing of the eruption. We followed 974 HIV-1-positive patients for 46 months as a part of a military study of HIV-1 disease. Within this group there were a total of 283 drug eruptions, with cutaneous manifestations in 201 patients in which clinical characteristics were noted and 86 patients in which cutaneous biopsies were performed. Serological evidence of reactivation or acute Epstein-Barr virus (EBV) or cytomegalovirus (CMV) infections were also noted, as well as peripheral eosinophilia. The incidence of drug eruptions significantly increased with increasing Walter Reed stage and decreasing CD4 counts and CD4/CD8 ratio, as well as with increasing age and in patients with increased numbers of other dermatological diagnoses. In addition, white patients had significantly more drug eruptions than did black. Serological or culture evidence of acute or reactivated EBV or CMV was significantly increased in patients with drug eruptions. The majority of the eruptions were maculopapular or morbilliform with a predominantly perivascular mononuclear cell infiltrate. HIV-1 positive patients have an increased incidence of drug reactions, the incidence having been reported to increase in patients with less than 200 CD4+ T cells/microliter. However, at very low T4 counts, especially those less than 25/microliter, and at a CD4/CD8 ratio of less than 0.10, the probability of reactions to trimethoprim-sulphamethoxazole (TMP-SMZ) is decreased in late-stage HIV-1 patients. Maculopapular or morbilliform eruptions are the most common clinical presentations, often accompanied by one or more of the following: fever, arthralgias, eosinophilia, and serum transaminase elevation. Histologically the majority of these eruptions show a perivascular mononuclear cell infiltrate, sometimes with focal interface changes and apoptotic, necrotic cells within the epidermis. Acute hypersensitivity reactions and toxic epidermal necrolysis (TEN) or Stevens-Johnson's syndrome (SJS) with diffuse epidermal apoptosis and necrosis have also been less commonly described. In a study of cutaneous manifestations in an HIV-1 positive military population, drug reactions were evaluated in terms of clinical features, histopathology, demographic features and laboratory findings.

Interfacial/free radical polymerization microencapsulation: kinetics of particle formation

Microcapsules containing pigment and polymer were prepared by dispersing a viscous mixture of pigment, core monomers, initiators and oil-soluble shell monomer in an aqueous solution of surfactants, forming oil-in-water droplets. Subsequently, a water-soluble shell monomer was added to these droplets, encapsulating them via interfacial (IF) polycondensation. These microcapsules were then heated for free radical (FR) polymerization of the core monomers. Effects of primary variables, such as the shearing time during particle formation, surfactant concentration, organic phase concentration, and mode of water-soluble shell monomer addition, were studied. The results indicated that polyvinylalcohol (PVOH), used as the surfactant/stabilizer, reacted with the oil-soluble shell monomers. The depletion of PVOH, especially when PVOH concentration was low, resulted in rapid growth of particle size and, eventually, suspension failure. The kinetic data revealed a particle formation mechanism which consists of two processes. The first process is the formation of an equilibrium particle size by the equilibrium process of particle breakage due to the mechanical shearing force and coalescence due to collisions among particles and surface tension forces. The second process is the reaction between PVOH and oil-soluble shell monomer which leads to the depletion of PVOH and consequently causes more coalescence of particles and a significant increase in the equilibrium particle size. The net effect of these two processes shows an optimum shearing time where the smallest particle size can be attained, and this optimum time is a function of several primary variables. Methods to prevent the reaction and therefore the depletion of PVOH are proposed.