Understanding barriers to reducing antimicrobials on Australian dairy farms: A qualitative analysis

INTRODUCTION

Reducing antibiotic use in production animal systems is one strategy which may help to limit the development of antimicrobial resistance. To reduce antimicrobial use in food-producing animals, it is important to first understand how antibiotics are used on farm and what barriers exist to decreasing their use. In dairy production systems, mastitis is one of the most common reasons for administering antimicrobials. Therefore, it is important to understand the motivations and behaviours of dairy farmers in relation to the diagnosis, treatment and prevention of mastitis.

MATERIALS AND METHODS

In this study, we interviewed a sample of dairy farmers and dairy industry professionals from the major dairying regions of eastern Australia regarding their current practices used to diagnose, treat, and control subclinical and clinical mastitis. Inductive thematic analysis was used to code interview transcripts and identify the recurrent themes.

RESULTS

Four overarching themes were identified: (1) the challenges associated with the detection and diagnosis of clinical mastitis, including with laboratory culture, (2) the motivations behind treatment decisions for different cases, (3) decisions around dry cow therapy and the role of herd recording, and (4) concerns regarding the development of antimicrobial resistance.

DISCUSSION

This study identifies several challenges which may limit the ability of Australian dairy farmers to reduce antimicrobial use on farm, such as the need for rapid and reliable diagnostic tests capable of identifying the pathogenic causes of mastitis and the difficulties associated with conducting herd recording for the implementation of selective dry cow therapy. Industry professionals were concerned that farmers were not using individual cow records to aid in treatment decisions, which could result in unnecessary antimicrobial use. The results of this study can act as the basis for future research aimed at assessing these issues across the broader Australian dairy industry.

A holistic analysis of the intrinsic and delivery-mediated toxicity of siRNA therapeutics

Small interfering RNAs (siRNAs) are among the most promising therapeutic platforms in many life-threatening diseases. Owing to the significant advances in siRNA design, many challenges in the stability, specificity and delivery of siRNA have been addressed. However, safety concerns and dose-limiting toxicities still stand among the reasons for the failure of clinical trials of potent siRNA therapies, calling for a need of more comprehensive understanding of their potential mechanisms of toxicity. This review delves into the intrinsic and delivery related toxicity mechanisms of siRNA drugs and takes a holistic look at the safety failure of the clinical trials to identify the underlying causes of toxicity. In the end, the current challenges, and potential solutions for the safety assessment and high throughput screening of investigational siRNA and delivery systems as well as considerations for design strategies of safer siRNA therapeutics are outlined.

Effects of psychotropic switches on weight change: a prospective cohort study

Introduction

Many psychotropic drugs can induce weight gain with differences in their metabolic risk profiles (i.e. high, medium or low-risk).

Objectives

To compare the weight evolution of patients switching versus patients keeping their psychotropic drugs with different risk-profiles.

Methods

Data for patients switching or keeping the same drug were obtained from the Psyclin (from 2007 to 2015) and Psymetab (2007- 2019) cohort studies, conducted at the Lausanne University Hospital, Switzerland. Patients either switched from a high to a low-risk, a high to a medium-risk, a medium to a low-risk drug, or for a drug with the same risk category. Patients not switching either kept a high, medium or low-risk drug. The evolution of weight is currently being analyzed using a linear mixed-effect model.

Results

Preliminary results showed that switching from a high to low-risk molecule had the strongest impact on weight changes. The analysis being ongoing, the quantitative results will be presented at the congress.

Conclusions

Switching from a high-risk to a low-risk molecule is likely to have the strongest impact on weight changes.

Disclosure

No significant relationships.

The quest for a better fight: How can nanomaterials address the current therapeutic and diagnostic obstacles in the fight against COVID-19?

The inexorable coronavirus disease 2019 (COVID-19) pandemic with around 226 million people diagnosed and approximately 4.6 million deaths, is still moving toward more frightening statistics, calling for the urgent need to explore solutions for the current challenges in therapeutic and diagnostic approaches. The challenges associated with existing therapeutics in COVID-19 include lack of in vivo stability, efficacy, and safety. Nanoparticles (NPs) can offer a handful of tools to tackle these problems by enabling efficacious and safe delivery of both virus- and host-directed therapeutics. Furthermore, they can enable maximized clinical outcome while eliminating the chance of resistance to therapy by tissue-targeting and concomitant delivery of multiple therapeutics. The promising application of NPs as vaccine platforms is reflected by the major advances in developing novel COVID-19 vaccines. Two of the most critical COVID-19 vaccines are mRNA-based vaccines delivered via NPs, making them the first FDA-approved mRNA vaccines. Besides, NPs have been deployed as simple, rapid, and precise tools for point of care disease diagnosis. Not enough said NPs can also be exploited in novel ways to expedite the drug discovery process. In light of the above, this review discusses how NPs can overcome the hurdles associated with therapeutic and diagnostic approaches against COVID-19.

Wooden hoof blocks: are we using the right wood?

AIMS

To investigate the association between the density of wooden hoof blocks and resistance to wear in pasture-based dairy herds, and to assess the density of commercially available wooden hoof blocks.

METHODS

Three types of wooden hoof blocks with different densities (low, medium and high) were attached to 36 lactating dairy cows with parity ≤2 and sound locomotion (score ≤2 on a scale of 1-4). The height of wooden blocks was measured in three different regions, front, abaxial and caudal on Days 7, 11, 14, 18, 21, 25 and 28 after application. Due to the loss of low-density wooden blocks, the data for these blocks were analysed for only two measurements on Days 7 and 11. The data for medium and high-density wooden blocks were analysed from Days 7-25. A linear mixed model with repeated measures was used to analyse the repeated observations. Height, density and surface area of commercially available hoof blocks (n = 19) were measured and compared to the blocks used in this study.

RESULTS

The magnitude of wear, in the front and the abaxial point of the blocks were greater in blocks made of low-density wood compared to those made of medium and high-density wood (p < 0.001). The amount of wear increased over time for all groups (p < 0.001). Wood density was negatively associated with wear and loss. Measurements of commercial wooden blocks revealed that the 13/19 (63%) had lower density and 12/19 (68%) less surface area than the wooden blocks with medium density used in this study.

CONCLUSION

In this study, the density of the wood was significantly associated with the longevity of hoof blocks when applied to hooves of pasture-based dairy cows.

CLINICAL RELEVANCE

The longevity of the wooden hoof blocks applied to treat lame cows plays a significant role in the healing of the claw horn lesions. The density of a wooden hoof block affects the rate of wear of the block, and this should be considered by manufacturers and those treating lame cows.

Effect of plasma-induced oxidative stress on the glycolysis pathway of Escherichia coli

Antibiotic resistance is one of the world's most urgent public health problems. Due to its antibacterial properties, cold atmospheric plasma (CAP) may serve as an alternative method to antibiotics. It is claimed that oxidative stress caused by CAP is the main reason of bacteria inactivation. In this work, we computationally investigated the effect of plasma-induced oxidation on various glycolysis metabolites, by monitoring the production of the biomass. We observed that in addition to the significant reduction in biomass production, the rate of some reactions has increased. These reactions produce anti-oxidant products, showing the bacterial defense mechanism to escape the oxidative damage. Nevertheless, the simulations show that the plasma-induced oxidation effect is much stronger than the defense mechanism, causing killing of the bacteria.

Targeting non-apoptotic cell death in cancer treatment by nanomaterials: Recent advances and future outlook

Many tumors develop resistance to most of the apoptosis-based cancer therapies. In this sense targeting non-apoptotic forms of cell death including necroptosis, autophagy and ferroptosis may have therapeutic benefits in apoptosis-defective cancer cells. Nanomaterials have shown great advantages in cancer treatment owing to their unique characteristics. Besides, the capability of nanomaterials to induce different forms of cell death has gained widespread attention in cancer treatment. Reports in this field reflect the therapeutic potential of necroptotic cell death induced by nanomaterials in cancer. Also, autophagic cell death induced by nanomaterials alone and as a part of chemo-, radio- and photothermal therapy holds great promise as anticancer therapeutic option. Besides, ferroptosis induction by iron-based nanomaterials in drug delivery, immunotherapy, hyperthermia and imaging systems shows promising results in malignancies. Hence, this review is devoted to the latest efforts and the challenges in this field of research and its clinical merits.

Linear body measurements and productivity of subtropical Holstein-Friesian dairy calves

OBJECTIVE

The study aimed to describe growth parameters and to quantify the association between linear body measurements as predictors of liveweight (LW) of Holstein-Friesian (HF), and HF crossbred dairy calves in Queensland. A secondary objective was to quantify the effect of disease events on LW change.

STUDY DESIGN

Longitudinal study.

METHODS

Fortnightly LW, hip height (HH), hip width (HW) and heart girth (HG) measurements were recorded from 16 male and 28 female HF calves from birth until weaning. The association between linear body measurement and the effect of a disease event on LW change were explored using linear mixed-effects modelling with random intercepts and random slopes.

RESULTS

HG was the best body measure used individually as a predictor of calf LW (R2 = 82%; P < 0.001), while the combined use of HG, HW and HH was the most accurate predictor of calf LW between birth and weaning (R2 = 90%; P < 0.001). HW, average feed intake and total feed intake were significantly affected by disease events (P < 0.05). On average, total average LW loss associated with a single pneumonia event was estimated at 14.6 kg (95% CI = 10.5 to 18.7 kg; P < 0.05).

CONCLUSIONS

Calves of this study performed at a level consistent with the previously published reports. Growth performance was significantly compromised by pneumonia. HW was found to be the least predictive individual measure, and the combined use of HH, HW and HG had the most accurate prediction of calf liveweight from birth to weaning.

Farmers' perceptions and approaches to detection, treatment and prevention of lameness in pasture-based dairy herds in New South Wales, Australia

AIMS

The objective of this study was to investigate farmers' perception of lameness in comparison to the estimated prevalence of lameness in NSW pasture-based dairies to evaluate farmers' perceptions and approaches to detection, treatment and prevention of lameness.

METHODS

Across-sectional study was conducted on 62 pasture-based dairy farms across NSW, Australia. The prevalence of lameness in these farms was estimated using locomotion scoring (1-4 scale). A survey was also conducted, using a questionnaire and face-to-face interview, to explore farmers' perceived prevalence of lameness and approaches to treatment and prevention.

RESULTS

The prevalence of lameness estimated by farmers was 3.7 times less (mean: 5%; range 0% to 26%) than that determined by locomotion scoring (mean: 19.1%; range 5.0%-44.5%). Approaches to treatment included antimicrobial therapy, hoof inspection with or without application of wooden blocks. In 28% of the farms, the lame cows were managed by farmers or farm staff with no official training in treatment of lame cows. The mean interval from detection of lameness to examination of the affected hoof was almost 55 hours (range 2-720 hours). A very low percentage of farms kept lameness records or implemented lameness preventive strategies such as footbaths and prophylactic foot trimming.

CONCLUSIONS

Farmers and farm managers were found to underestimate the prevalence of lameness which could be due to the low level of awareness and can contribute to subsequent lack of implementation of prophylactic procedures and preventive management strategies for lameness. These findings accentuate the need to improve farmers' ability to detect lame cows and to emphasise the importance of recording in order to facilitate the management of lameness in dairy herds.

P1759 How an echocariologist can work off-line in a personal computer on the echocardiography images at the level of mitral valve?

Background

The objective of this presentation is to provide an educational survey on the mitral valve geometrical indices measurements using MATLAB software offline in a personal computer as an echo desk for further information and recommendation before mitral valve repairs or the other treatments.

Methods and Results:

Utilizing mathematical equation and MATLAB software (a simple echo desk) to measure the geometrical mitral valve variables offline based on 2D or 3D conventional echocardiographic images.

MATLAB software as an echocardiography desk

Open the MATLAB software. Write down the command pic = imread(‘’) in the command window. You can use this command to read an echocardiographic image from your computer and in a variable like a put. You must write the image address, image name and photo extensions in parentheses. For example, your echocardiographic image is in the following address: C:\Users\USER\Desktop\echo image 1.jpg. You should write the above command like this: pic = imread(‘C:\Users\USER\Desktop\echo image 1.jpg’); Finally, call that image by imshow(pic) command and then save the program and click the RUN bottom. You will see that a new window is opened and the image you are looking for is displayed. You can edit or measure the distances of the image using the menus above this observed image (Figure A). You can also extract frames from an echocardiography video clip of a patient by writing down the command Avi2frame (‘1.avi’, ‘OutputFolder’,’jpg’) in the command window and then you can work offline on echocardiography images frame by frame to calculate quantitative data (Figures B and C).

Conclusion

In spite of the introduced methods applied for echocardiographic datasets at the level of mitral valve for practical applications and clinical verifications. The most important applications, however, may be pedagogical. A computer desk (online or offline) can help an Echocardiologist to work on the echocardiographic images to evaluate the data.

Abstract P1759 Figure. working offline on echo images

Emerging Roles of Probiotics in Prevention and Treatment of Breast Cancer: A Comprehensive Review of Their Therapeutic Potential

Breast cancer is the most common cancer among women. Need for novel preventive and curative approaches with more safety than the present one seems inevitable. This review is devoted to potentially favorable role of probiotics in prevention and treatment of breast cancer as well as their alleviating role regarding chemotherapy-induced side effects. Literature was searched for human, animal, and in vitro studies about the role of probiotics in breast cancer. In vitro studies showed that probiotic intervention induces cancer cells apoptosis and inhibits their proliferation. In animal models, treatment with probiotics inhibited tumor growth and reduced tumor size; also, the immunomodulatory, antiangiogenesis and antimetastatic activities of probiotics were illustrated. Human studies showed that intake of Lactobacillus casei shirota reduced the breast cancer incidence and consumption of fermented milk products and yogurt was inversely associated with breast cancer incidence; however, no study regarding the curative role of probiotics in breast cancer is available. Studies on the effect of probiotics on chemotherapy-induced side effects in breast cancer were contradictory but showed potential for more investigation. Probiotics seem to have a potential role in both prevention and treatment of breast cancer. However, more clinical studies are needed to elucidate their efficacy and safety.

Tetrahydroquinolinone derivatives as potent P-glycoprotein inhibitors: design, synthesis, biological evaluation and molecular docking analysis

P-glycoprotein (P-gp) is a transmembrane efflux pump that has been associated with ineffective cancer chemotherapy and multidrug resistance (MDR). Chemical inhibitors of P-gp could have potential cancer therapeutic applications by preventing or reversing MDR. To exploit this, we designed twenty-five tetrahydroquinolinone analogs bearing pyridyl methyl carboxylate at C₃ and different substituents at C₄ as MDR reversal agents. The inhibitory effects of the synthesized compounds against P-gp were assessed by flow cytometric determination of rhodamine 123 accumulation in P-gp over-expressing MES-SA/DX5 cells. Fluorescence imaging of intracellular rhodamine 123 accumulation in MES-SA/DX5 cells was also performed. Furthermore, the effect of active derivatives on the reduction of doxorubicin's IC₅₀ in MES-SA/DX5 cells was evaluated using MTT assay. Molecular docking was used to confirm the binding mode of some of the synthesized compounds. Five compounds in group A, bearing a 2-pyridyl methyl ester substituent at the C₃ position, significantly increased rhodamine accumulation at 25 μM comparable to verapamil, a well-established P-gp inhibitor, while only 2 compounds in group B bearing 3-pyridyl methyl ester at the same position had this effect. This study shows that tetrahydroquinolinones containing methyl pyridine esters could represent an attractive scaffold for the discovery of P-gp inhibitors as MDR reversal agents in cancer cells.

MRI-Based Texture Analysis to Differentiate Sinonasal Squamous Cell Carcinoma from Inverted Papilloma

BACKGROUND AND PURPOSE

Because sinonasal inverted papilloma can harbor squamous cell carcinoma, differentiating these tumors is relevant. The objectives of this study were to determine whether MR imaging-based texture analysis can accurately classify cases of noncoexistent squamous cell carcinoma and inverted papilloma and to compare this classification performance with neuroradiologists' review.

MATERIALS AND METHODS

Adult patients who had inverted papilloma or squamous cell carcinoma resected were eligible (coexistent inverted papilloma and squamous cell carcinoma were excluded). Inclusion required tumor size of >1.5 cm and preoperative MR imaging with axial T1, axial T2, and axial T1 postcontrast sequences. Five well-established texture analysis algorithms were applied to an ROI from the largest tumor cross-section. For a training dataset, machine-learning algorithms were used to identify the most accurate model, and performance was also evaluated in a validation dataset. On the basis of 3 separate blinded reviews of the ROI, isolated tumor, and entire images, 2 neuroradiologists predicted tumor type in consensus.

RESULTS

The inverted papilloma (n = 24) and squamous cell carcinoma (n = 22) cohorts were matched for age and sex, while squamous cell carcinoma tumor volume was larger (P = .001). The best classification model achieved similar accuracies for training (17 squamous cell carcinomas, 16 inverted papillomas) and validation (7 squamous cell carcinomas, 6 inverted papillomas) datasets of 90.9% and 84.6%, respectively (P = .537). For the combined training and validation cohorts, the machine-learning accuracy (89.1%) was better than that of the neuroradiologists' ROI review (56.5%, P = .0004) but not significantly different from the neuroradiologists' review of the tumors (73.9%, P = .060) or entire images (87.0%, P = .748).

CONCLUSIONS

MR imaging-based texture analysis has the potential to differentiate squamous cell carcinoma from inverted papilloma and may, in the future, provide incremental information to the neuroradiologist.

Ultrastructural localization of the RNA of immunodeficiency viruses using electron microscopy in situ hybridization and in vitroinfected lymphocytes

Cells infected in vitro with immunodeficiency viruses have been examined by electron microscopy in situ hybridization (EM ISH) methods for localization of viral RNA. Techniques used for preparation of specimens and probes are described. Unambiguous positive results were obtained using a mixture of two or three single negative strand DNA oligonucleotides complementary to regions of the gag, env and nef genes, each 200-300 bases and labelled with dig-11-UTP. Positive strand probes were used as a negative control. Cells were fixed with a mixture of formaldehyde and glutaraldehyde, dehydrated in ethanol with progressive lowering of temperature and embedded in Lowicryl K4M or HM20 at -35 degrees C. Permeabilization or pre-treatment of sections with proteinase K was not essential. The hybridization mixture was applied for 3-4h at 37 degrees C and probe was visualized by direct immuno-staining with sheep anti-digoxigenin antibodies conjugated to 10nm gold. This method would be suitable for future studies of the pathogenesis of retroviral infections and as a basis for further development of the EM ISH technique. EM ISH of in vitro infections of immunodeficiency viruses has shown the location of viral RNA in immature and mature viruses and its relationship to multimerized Gag protein during viral budding. The label for RNA has also been found in the cytoplasm of infected cells; it was mainly located adjacent to the plasma membrane and unassociated with visible Gag proteins. This may indicate that viral RNA migrates to the plasma membrane independently of the Gag protein and may, in some instances, arrive at the plasma membrane prior to the Gag protein. Viral RNA has also been found in the nucleus of peripheral blood mononuclear cells (PBMC) that were showing no morphological evidence of infection. The RNA was typically located in the nucleolus and in peripheral dense chromatin. These cells, which displayed morphological features of macrophage lineage, may have been the initial cell type to be infected in the PBMC.

Construction of infectious SIV/HIV-2 chimeras

OBJECTIVE

To construct SIV/HIV-2 chimeras (SHIV) that replicate in vivo. These would be valuable tools to elucidate the mechanism by which HIV-2 can bypass protection conferred by live attenuated SIV vaccines.

METHOD

Novel SHIV were constructed to express either the vpx, vpr, tat, rev and env genes (SHIV-2isy env) or the gag and pol genes (SHIV-2isy gag/pol) of the infectious molecular clone HIV-2isy in an SIVmac backbone. The replication of SHIV-2isy env and SHIV-2isy gag/pol were evaluated on selected cell lines and peripheral blood mononuclear cells (PBMC) in vitro. In addition, their infectivity was assessed in vivo.

RESULT

Virus stocks of SHIV-2isy env and SHIV-2isy gag/pol were prepared in vitro. For SHIV-2isy gag/pol both the 5' and 3' boundaries of the chimeric construct were critical for infectivity in vitro. The growth of each chimera on T cell lines in vitro mirrors that of the parental viruses donating the envelope gene. On PBMCs SHIV-2isy env replicated well on human and simian PBMC whereas SHIV-2isy gag/pol replicated to detectable levels on human PBMC only. In vivo, SHIV-2isy env virus was isolated from one of two cynomolgus macaques challenged intravenously, SHIV-2isy gag/pol was isolated from one of two cynomolgus macaques and both rhesus macaques challenged intravenously.

CONCLUSION

This is the first report of SIV/HIV-2 chimeras that are infectious in macaques. Moreover, this is the first report of an infectious chimera in which both SIV gag and pol have been replaced with the equivalent regions of an HIV isolate.

Comparison of in vitro and in vivo infectivity of different clade B HIV-1 envelope chimeric simian/human immunodeficiency viruses in Macaca mulatta

The use of HIV-1 env/SIVmac chimeric viruses expressing divergent HIV-1 envelopes of clinical isolates, facilitates homologous and heterologous evaluation of various recombinant HIV-1 envelope vaccine candidates in lower primates. In this study we compare the in vitro and in vivo infectivity, via intravenous (IV) and intravaginal (IVAG) routes of infection, of stocks of chimeric viruses expressing env from four different clade B HIV-1 isolates. The TCID50/ml was 7.1 x 10(4), 1.0 x 10(4), 6.3 x 10(4), and 1.2 x 10(3) for SHIVsf13, SHIVHan2, SHIVNM-3rn, and SHIVW6.1D, respectively, with a MID50/ml upon IV inoculation of 3.2 x 10(3), 3.2 x 10(4), 3.2 x 10(4), and 3.2 x 10(3), respectively. The same SHIVsf13 stock was infectious after IVAG administration, requiring a 300-fold higher virus dose. Plasma antigenemia and cell-associated viremia were generally highest at weeks 2 or 4 after infection and decreased to subdetectable levels after 8-12 weeks. All infected animals tested developed anti-HIV-1 gp120 antibodies. Inoculated virus dose showed no (linear) quantitative correlation with cellular virus load, duration of viremia, plasma antigenemia, and anti-gp120 antibody titers. No significant changes in peripheral blood CD4 cell levels were observed and none of the animals has shown evidence of disease progression to date (i.e., 13 months postinfection). Four in vivo passages of cell-associated SHIVW6.1D did not result in increased virulence. Vaccine development studies in macaques monkeys have become feasible with the use of various clade B HIV-1 env SHIV chimeras.

The construction and evaluation of SIV/HIV chimeras that express the envelope of European HIV type 1 isolates

The molecular construction of SIV/HIV-1 chimeric viruses (or SHIVs), provides a means of infecting macaques with immunodeficiency viruses that express the envelope protein of HIV-1. However, to date, most SHIVs produced express the envelope of isolates of HIV-1 that have been passaged repeatedly in T cell lines. We have taken SHIV-4 and replaced an NheI-AvrII fragment that encompasses the gp120 region and the extracellular portion of gp41 with the equivalent region of two European isolates of HIV-1 (ACH320.3.1 and HIV-1Han-2). Neither of these viruses had been passaged in T cell lines for prolonged periods prior to molecular cloning. Virus stocks were prepared of both SHIV constructs. In vitro, the relative ability of each clone to replicate in four T cell lines mirrored closely the pattern observed with the parental virus donating the envelope sequences. In vivo, only one of the chimeric viruses was infectious in cynomolgus macaques and its recovery was transient. The factors that affect the replication of SHIVs in vitro and in vivo are discussed.

Influence of hydrogen peroxide on the in vitro infectivity of human immunodeficiency virus

The object of this study was to investigate the influence of reactive oxygen intermediates (ROI), such as H2O2, on HIV-1 infection of cell cultures. The CD4+ HeLa human epithelial carcinoma cell line clone pBKTRLac was infected with HIV-1MN that had been treated with 0.01-5mM H2O2. Virus infectivity was detected by 3 methods: (a) using transactivation of LTR-linked beta-Galactosidase, (b) viral core p24 antigen enzyme-linked immunoasorbent assay (ELISA), and (c) reverse transcriptase activity assay. Treatment of HIV-1MN cell free virus particles with 0.01 mM H2O2 resulted in a significant increase in virus infection. This effect declined with increasing H2O2 concentrations from 0.05 to 0.1 mM. Further increases in H2O2 concentration up to 5 mM resulted in significant suppression in virus infection. These observations indicate that H2O2 may play a role in affecting the course of HIV infection.

Standard conditions of virus isolation reveal biological variability of HIV type 1 in different regions of the world. WHO Network for HIV Isolation and Characterization

HIV-1 isolates were obtained from four countries within the framework of the WHO Network for HIV Isolation and Characterization. The use of standard HIV isolation procedures allowed us to compare the biological properties of 126 HIV-1 isolates spanning five genetic subtypes. In primary isolation cultures, viruses from Uganda and Brazil appeared early and replicated without delay, whereas the replication of Thai viruses was delayed by several weeks. Regardless of genetic subtype or country of origin, blood samples collected more than 2 years after seroconversion yielded virus that replicated efficiently in the primary isolation cultures. None of the isolates obtained from Thailand or Rwanda replicated in cell lines, whereas 5 of the 13 Brazilian isolates and 7 of the 11 Ugandan isolates replicated and induced syncytia in MT-2 cells. As expected for virus isolates obtained early in HIV-1 infection (within 2 years of seroconversion), all viruses from Brazil, Rwanda, and Thailand showed a slow/low replicative pattern. For the Ugandan samples, the time from seroconversion was known precisely for a few of the samples and only in one case was less than 2 years. This may explain why the five viruses that were able to replicate in all cell lines, and thus classified as rapid/high, were of Ugandan origin. Viruses able to induce syncytia in MT-2 cells, also induced syncytia in PBMC. However, 8 slow/low viruses (out of 27) gave discordant results, inducing syncytia in PBMC but not in MT-2 cells. Furthermore, using syncytium induction as a marker, changes in virus populations during early in vitro passage in PBMC could be observed.(ABSTRACT TRUNCATED AT 250 WORDS)

T-lymphocyte transformation in experimental obstructive jaundice: the role of serum-suppressive factors

Infective complications are a significant problem in the management of patients with obstructive jaundice, despite the widespread use of prophylactic antibiotics. The cause of this may be suppression of the immune system. This study investigates the effect of serum from an animal model of extrahepatic biliary obstruction (BDL) for 7, 14, and 21 days on the lymphoproliferative response of a single population of T-lymphocytes to the mitogen phytohemagglutinin (PHA). Mean stimulation counts for lymphocytes cultured with 7 days with BDL serum (938 +/- 90 p = 0.04) and for 21 days with BDL serum (844 +/- 253 p = 0.04) are significantly lower than control serum (2382 +/- 1340). The effect of 14 days BDL serum has some suppression of lymphocyte stimulation but this is not significant (1115 +/- 429 p = 0.06). There was no significant correlation with any clinical parameters including bilirubin and the duration of jaundice. We have concluded that serum from animals with obstructive jaundice is immunosuppressive, but further studies are required to identify the factor and its role in vivo.

DNA damage in human T-lymphoblastoid cell line Molt-3 induced by reactive oxygen species

In the course of studying the effect of reactive oxygen species such as superoxide anion (O2-), hydrogen peroxide (H2O2) on oxidant-sensitive human T-lymphoblastoid cell line Molt-3, O2- has been generated by the interaction of xanthine with xanthine oxidase (XOD). To confirm that H2O2 is a key intermediate for inducing DNA single-strand breaks in Molt-3 cells, studies have been carried out with pure H2O2. In the presence of xanthine + XOD or H2O2 the amount of DNA single-strand breaks has been found to increase as a function of the O2- and H2O2 concentration. Data from studies with antioxidants such as superoxide dismutase and catalase supports a mechanism of DNA damage dependent on the presence of H2O2 in Molt-3 cells. Molt-3 cells are CD4+ and sensitive to reactive oxygen stress and therefore, could be an ideal cell line for determining the relationship between oxidative stress and various diseases such as acquired immunodeficiency syndrome (AIDS).