Different evolution of S. aureus methicillin-resistant and methicillin-susceptible infections, Argentina

Staphylococcus aureus-(SA) is widespread among healthcare-associated-(HA) and the community-associated-(CA) infections. However, the contributions of MRSA and MSSA to the SA overall burden remain unclear. In a nationally-representative-survey conducted in Argentina, 668 SA clinical isolates from 61 hospitals were examined in a prospective, cross-sectional, multicenter study in April 2015. The study aimed to analyze MRSA molecular epidemiology, estimate overall SA infection incidence (MSSA, MRSA, and genotypes) in community-onset (CO: HACO, Healthcare-Associated-CO and CACO, Community-Associated-CO) and healthcare-onset (HO: HAHO, Healthcare-associated-HO) infections, stratified by age groups. Additionally temporal evolution was estimated by comparing this study's (2015) incidence values with a previous study (2009) in the same region. Erythromycin-resistant-MSSA and all MRSA strains were genetically typed. The SA total-infections (TI) overall-incidence was 49.1/100,000 monthly-visits, 25.1 and 24.0 for MRSA and MSSA respectively (P = 0.5889), in April 2015. In adults with invasive-infections (INVI), MSSA was 15.7 and MRSA was 11.8 (P = 0.0288), 1.3-fold higher. HA SA infections, both MSSA and MRSA, surpassed CA infections by over threefold. During 2009-2015, there was a significant 23.4 % increase in the SA infections overall-incidence, mainly driven by MSSA, notably a 54.2 % increase in INVI among adults, while MRSA infection rates remained stable. The MSSA rise was accompanied by increased antimicrobial resistance, particularly to erythromycin, linked to MSSA-CC398-t1451-ermT + -IEC+-pvl- emergence. The SA-infections rise was primarily attributed to community-onset-infections (37.3 % and 62.4 % increase for TI and INVI, respectively), particularly HACO-MSSA and HACO-MRSA in adults, as well as CACO-MSSA. The main CA-MRSA-PFGE-typeN-ST30-SCCmecIVc-PVL+/- clone along with other clones (USA300-ST8-IV-LV-PVL+/-, PFGE-typeDD-ST97-IV- PVL-) added to rather than replaced CA-MRSA-PFGE-typeI-ST5-SCCmecIVa-PVL+/- clone in HA invasive-infections. They also displaced clone HA-MRSA-PFGE-typeA-ST5-SCCmecI, mainly in HAHO infections. The overall-burden of SA infections is rising in Argentina, driven primarily by community-onset MSSA, particularly in adults, linked to increased erythromycin-resistance and MSSA-CC398-t1451-ermT + -IEC+-pvl- emergence. Novel knowledge and transmission-control strategies are required for MSSA.

A decrease in the incidence of Shiga toxin-related hemolytic uremic syndrome as a cause of kidney transplantation at an argentine referral center

BACKGROUND

In Argentina, Hemolytic uremic syndrome caused by Shiga toxin-producing Escherichia coli (STEC HUS), is the main cause of acute kidney injury and the second cause of end-stage renal disease (ESRD) in children. In recent decades, strategies have been implemented to reduce progression to ESRD, but it is not known whether the cumulative incidence of HUS requiring kidney transplantation (KTx) has decreased. We aimed to determine whether the cumulative incidence of STEC HUS in children undergoing KTx decreased and compared outcomes of HUS-related KTx vs. those related to other etiologies.

METHODS

All patients who underwent KTx at our institution were evaluated. The cohort was divided into quintiles (Q), and we compared the cumulative incidence of HUS-related KTx vs KTx due to other etiologies.

RESULTS

A total of 1000 consecutive KTx were included. The cumulative incidence of HUS-related KTx was 11%. HUS was the second cause of KTx in Q1: 17% (1988-1995); Q2: 13.5% (1996-2003); Q3: 11.5% (2004-2009) and third cause in Q4: 10% (2010-2015) and Q5: 3% (2016-2021). The cumulative incidence of HUS-related KTx decreased in Q4 and Q5 compared to Q1, Q2, and Q3 and the decline was even steeper when comparing Q4 to Q5 (p:0.019). There was no difference in graft survival in patients with HUS vs. congenital anomalies of kidney and urinary tract (CAKUT) but better than in those with focal segmental glomerulosclerosis (FSGS).

CONCLUSIONS

In this cohort, the cumulative incidence of HUS-related KTx decreased, which may have been due to the implementation of nephroprotective strategies.

Carbapenem-resistant Enterobacteriaceae bloodstream infections: A case-control study from a pediatric referral hospital in Argentina

Background

Antibiotic-resistant gram-negative bloodstream infections (BSI) remain a leading cause morbidity and mortality in pediatric patients with a high impact on the public health system. Data in resource-limited countries, including those in Latin America and the Caribbean region, are scarce. The aim of the study was to identify risk factors for acquiring carbapenem-resistant Enterobacteriaceae (CRE) bacteremia in children and to assess the use of resources.

Methods

A retrospective case-control study was conducted to analyze demographic, epidemiological, clinical, microbiological, and outcome data as well as the use of resources between 2014 and 2019. Univariate and logistic regression analysis was performed in order to identify risk factors associated with CRE-BSI. The R software version 4.1.2 was used.

Results

A total of 46 cases with CRE-BSI and 92 controls with gram-negative non-CRE-BSI were included. No statistical difference was observed regarding: median age (36 months; IQR, 11.2-117 vs. 48 months, IQR 13-119), male sex (50 vs. 60%), and underlying disease (98 vs. 91%) in cases vs. controls, respectively. The most frequent mechanism of CRE bacteremia were: KPC in 74%, OXA in 15%, and NDM in 6.5%. A total of 54.3% of cases vs. 32.6 % (p = 0.016) of controls were admitted to the pediatric intensive care unit (PICU), and 48 vs. 21% (p = 0.001) required mechanical ventilation. Bacteremia secondary to intra-abdominal infection was observed in 56.5% of cases vs. 35% of controls (p = 0.032). Previous colonization with CRE was detected in 76% of cases vs. 8% of controls. Combination antimicrobial treatment was most frequent in cases vs. control (100 vs. 56.5%). No difference was observed in median length of hospital stay (22 days; IQR, 19-31 in cases vs. 17.5 days; IQR, 10-31 in controls; p = 0.8). Overall case fatality ratio was 13 vs. 5.5%, respectively. The most statistically significant risk factors included previous PICU stay (OR, 4; 95%CI, 2-8), invasive procedures/surgery (OR, 3; 95%CI, 1-7), central venous catheter placement (OR, 6.5; 95%CI, 2-19), urinary catheter placement (OR, 9; 95%CI 4-20), mechanical ventilation (OR, 4; 95%CI, 2-10), liver transplantation (OR, 8; 95%CI, 2-26), meropenem treatment (OR, 8.4; 3.5-22.6) in univariate analysis. The logistic regression model used for multivariate analysis yielded significant differences for previous meropenem treatment (OR, 13; 95%CI, 3-77; p = 0.001), liver transplantation (OR, 13; 95%CI, 2.5-100; p = 0.006), and urinary catheter placement (OR, 9; 95%CI, 1.4-94; p = 0.03).

Conclusion

CRE-BSI affects hospitalized children with underlying disease, mainly after liver transplantation, with previous urinary catheter use and receiving broad-spectrum antibiotics, leading to high PICU requirement and mortality. These risk factors will have to be taken into account in our region in order to establish adequate health policies and programs to improve antimicrobial stewardship.

[Ascariasis in the intrahepatic biliary duct: about a case in pediatrics]

Twenty five percent of the world population is affected by Ascaris lumbricoides. Hepatobiliary ascariasis occurs in areas with high endemicity and great amount of parasitic load, generating intense inflammation to fibrosis. We report a twoyear- old patient that consults about abdominal distension and cough of one month of evolution associated with 72 hours of fever. Abdominal ultrasound is performed, which shows bile duct, stomach, small intestine with ascaris and chest x-ray with interstitial inflammatory infiltrate, associated with hyperleukocytosis with hypereosinophilia and elevated gamma-glutamyl transpeptidase. Antibiotic, anthelminthic treatment is administered, without achieving the elimination of the bile duct parasites, requiring their removal by percutaneous cholangiography.

[Experience with daptomycin in a tertiary pediatric hospital]

BACKGROUND

Vancomycin has been considered the treatment of choice especially for methicillin-resistant Staphylococcus aureus (MRSA) infections; but its poor tissue penetration, renal toxicity, and requiring of dosages monitoring, raises the need for new treatment alternatives such as daptomycin.

AIMS

To analyze the safety and effectiveness of daptomycin in children.

METHODS

Children with microbiologically documented infections treated with daptomycin were retrospectively included.

RESULTS

The most frequent infections were endocarditis in 9 (32%), sepsis in 4 (14%), bacteremia in 7 (associated with catheter in 3) (25%), osteomyelitis in 3 (10%), peritonitis associated with dialysis in 3 (10%) and suppurative thrombophlebitis in 2 patients (p) (7%). Methicillin-resistant Staphylococcus aureus was the most common pathogen in 18 patients (64%). The indications for daptomycin were due to the failure of conventional treatment in 17 (61%), and the toxicity or intolerance to vancomycin in 11 patients (39%). The average duration of treatment was 19 days (95% ICR 7-42 days). Four patients (14%) completed outpatient treatment, 22 patients had a favorable response (79%). Adverse events were reported in 3 patients (2 creatinine-phosfo-kinase increase) and in one severe skin rash.

CONCLUSIONS

Daptomycin demonstrated a favorable efficacy and safety in this pediatric population.

Epidemiological features and risk factors for mortality in Pseudomonas aeruginosa bacteremia in children

The objective was to describe the epidemiological, clinical, microbiological, and evolutionary characteristics and the risk factors for mortality. Retrospective, cohort study. A total of 100 patients were included. Of these, 42 (42 %) had septic shock upon admission and 56 (56 %) were admitted to the intensive care unit. Bacteremia was primary in 17 patients (17 %); catheter-related, in 15 (15 %); and secondary, in 68 (68 %). The most common source of infection was the skin and mucous membrane. Resistance to one or more antibiotic groups was 38 %. Thirty-one patients died (31 %). Risk factors for mortality were septic shock (p < 0.0005), admission to the intensive care unit (p < 0.0001), primary bacteremia (p < 0.009) or secondary, non-catheter-related bacteremia (p < 0.003), presence of mucocutaneous or pulmonary source of infection (p < 0.004), and multidrug resistance (p < 0.01) or resistance to carbapenems (p < 0.01).

[Histoplasmosis in Argentina: case series in children]

BACKGROUND

Histoplasmosis is a fungal disease, endemic in South America, and seldom reported in paediatrics.

AIMS

To report the epidemiology, clinical features and outcome of children diagnosed with histoplasmosis in an Argentinian Children's Hospital.

METHODS

A retrospective and descriptive study was performed from January 2008 to December 2016 in Hospital de Pediatría 'Prof. Dr. Juan Pedro Garrahan'. Patients under 18 years with clinical features, serological tests, cultures and/or histological findings compatible with histoplasmosis were included. Thirteen patients were selected (seven male and six female; mean age was 9 years with interquartile range 3.4-13); three children (23%) were from Buenos Aires province, three (23%) from Santa Fe province, and seven (54%) from other provinces.

RESULTS

In ten cases (77%) the clinical form was disseminated, and it was pulmonary in three (23%). Eight cases (62%) suffered other comorbidities. Serological tests were positive in seven patients (54%), with positive cultures obtained in nine patients (69%). Histological findings compatible with histoplasmosis were found in 10 cases (77%). All patients received treatment with amphotericin B (liposomal formulation in seven cases, deoxycholate in six), with 10 patients continuing with oral itraconazole. Three patients (23%) died from causes unrelated to histoplasmosis.

CONCLUSIONS

The majority of children in the series had comorbidities and disseminated histoplasmosis. Mortality was not directly associated with histoplasmosis.

Anidulafungin in children: Experience in a tertiary care children's hospital in Argentina

The experience using anidulafungin for the treatment of invasive fungal infections in pediatrics is limited. In this article, we describe our experience in 55 children. Anidulafungin was administered intravenously at a loading dose of 3 mg/kg once daily, followed by 1.5 mg/kg every 24 hours over a mean period of 14 days (range: 7-22 days). Patients' median age was 114 months old (interquartile range: 32-168 months old). All patients had underlying diseases. Among patients with bone marrow transplant, the difference in white blood cell count, transaminase levels, and renal function at baseline and at the end of anidulafungin administration was not significant. No adverse events were reported and no patient died from an anidulafungin-related cause. Anidulafungin may be considered an alternative for the prophylaxis or treatment of invasive fungal infections in pediatrics but methodologically robust studies are needed to confirm this.

[Use of posaconazole in children: Experience in a tertiary pediatric hospital]

There is limited information on the use of posaconazole in children. This retrospective and descriptive study was conducted to evaluate the clinical, microbiological characteristics and evolution of patients treated with posaconazole between August 2010 and March 2017. We included 16 children. Median age: 161 months (interquartile range -IQR- 69-173 m). All had underlying disease and a proven invasive fungal infection. The most frequent isolated were Mucor spp. and Aspergillus spp. The mean posaconazole dose was 600 mg/day (400-800 mg/day) and the median duration of treatment was 223 days (IQR 48-632). Ten patients had adverse effects, but only one required suspension of the antifungal treatment due to hydroelectrolytic disorders.

Echinococcosis in children: Experience in a tertiary care hospital outside the endemic area

Echinococcosis is a zoonotic disease that is widely spread across Argentina and worldwide. It is acquired during childhood but it is more common during adulthood. The pediatric population accounts for 10-20% of all cases. This study included 47 children diagnosed with echinococcosis over a 20-year period. Their median age was 8 years old (range: 3-17); most patients had some epidemiological history, such as having lived or living in an endemic or rural area and/ or having dogs that are fed with viscera. Findings included 85% of single cysts in only one parenchyma. Cysts were most commonly located in the liver and lungs. Medical/surgical treatment was carried out in 45 patients (96%). Subsequent complications were observed in 13 patients (28%), which were more common in those with lung cysts. Three patients (6%) relapsed 1-24 months later and required a new surgery. No patient died as a result of the parasitic disease.

[Cerebral hydatid disease: report of six pediatric cases]

Hydatid disease is a parasitic infection whose etiologic agent is Echinococcus granulosus. Human is an accidental intermediate host and the most common site is the liver. The brain involvement is unusual and up to 75% of cases are described in the pediatric population. We present six children with cerebral hydatid disease admitted to the Pediatric Hospital J.P. Garrahan. All had neurological involvement on admission. The images showed single cystic lesion in the brain. They did not present involvement in other organs. Serology was negative in all cases. Medical and surgical treatment in all cases. The clinical outcome was favorable without sequelae in five of them and one had a residual paresis right faciobrachiocrural. This infection should be considered in the differential diagnosis of cystic tumor lesions of the central nervous system.

Endospanin 1 silencing in the hypothalamic arcuate nucleus contributes to sustained weight loss of high fat diet obese mice

Leptin targets specific receptors (OB-R) expressed in the hypothalamus to regulate energy balance. Leptin decreases food intake in normal weight individuals, but this effect is blunted in obese subjects who are characterized by a state of leptin resistance. The prevention of leptin resistance is one of the major goals of obesity research. Recently, we identified endospanin 1 as a negative regulator of OB-R, which by interacting with OB-R retains the receptor inside the cell. We show here that in obese mice endospanin 1 is upregulated in the hypothalamic arcuate nucleus (ARC), the major brain structure involved in body weight regulation, suggesting that endospanin 1 is implicated in obesity development and/or the installation of leptin resistance. In contrast, silencing of endospanin 1 with lentiviral vectors in the ARC of obese mice fully restores leptin responsiveness when combined with a switch to ad libitum fed chow diet. The recovery of central leptin sensitivity is accompanied by sustained body weight loss and amelioration of blood lipid parameters and steatosis. Collectively, our results define endospanin 1 as a novel therapeutic target against obesity.

[Community-acquired Staphylococcus aureus bacteremia: 17 years of experience in Argentine children]

BACKGROUND

Community-acquired methicillin-resistant Staphylococcus aureus (CAMRSa) emerged in recent years. Few studies analyzed the impact of these infections in bacteremias (B).

OBJECTIVES

To analyze clinical, epidemiological, microbiological and outcome of CASa B between two periods (Period I: 1993-2004, and Period II: 2004-2007).

MATERIAL AND METHODS

Retrospective, observational and comparative study. All children older than 1 month of age and CASaB were included.

RESULTS

During the study period 647 SaB were diagnosed (Period I: 499 and Period II: 148). Of them, 140 (28%) and 49 (33%) were CSaB, respectively. The median age of patients was 5.9 and 4.8 years, respectively (p= NS). Clinical foci of infection and septic shock were more frequent in the period I (78% vs. 47%) and (5% vs. 16%) (p <0.05), respectively. Skin infection and septic shock were similar in both periods (78% vs. 67% and 5% vs. 8%; p= NS). Four CAMRSa B (3%) were diagnosed during the first period. One predisposing factor was identified in all cases. Inversely, 23 cases (47%) were diagnosed during the Period II (p <0.05). Resistance rates to clindamycin and gentamicin were more high during the second period (10% vs. 2% and 20% vs. 3%, respectively) (p <0.05). Patients in the second period had longer antibiotic treatment (X 16.6 vs. 10.1 days) and more frequent inappropriate treatment at admission (53% vs. 5%) (p <0.05). Hospital stay time was longer during de first period (19.2 vs. 12.2 days) (p <0.05). The mortality rate was higher in the first period (13% vs. 4%) (p= NS).

CONCLUSION

A significant increase of CAMRSa B were detected in recent years. It is necessary to evaluate the empirical treatment of severe community infections in children in our country.

[Community onset of methicillin resistant Staphylococcus aureus infections in previously healthy or health care-associated children in Argentina]

INTRODUCTION

Community-acquired methicillin-resistant Staphylococcus aureus infections (CA-MRSA) are prevalent in several countries of the world. These infections seem to differ clinically from those occurring within the health care system (HCS-MRSA).

OBJECTIVE

To compare clinical characteristics of infections by CA-MRSA and HCA-MRSA in the same community.

MATERIAL AND METHODS

Prospective, multicentric and comparative study. Children with clinically and microbiologically documented CA-MRSA were included.

RESULTS

Between 11/2006 and 11/2007, 840 infections caused by S. aureus were diagnosed. Of them 582 (68%) were community-acquired. Among these 356 (61%) were CA-MRSA. In this group, 75 (21%) were HCA-MRSA and 281 (79%) CA-MRSA. The median age was 36 months (range: 1-201). Chronic skin disease (13) and chronic disease of CNS (9) were the underlying disease predominant. Children with CA-MRSA had more frequency of previous antibiotic treatment (63 vs 34%) and previous medical consult (76 vs 52%), invasive procedures (31 vs 8%), surgery (15 vs 0.3%) and fever (94 vs 74%) (p = < 05). Children with CA-MRSA had subcutaneous abscesses (34 vs 15%) (p = < .05) more frequently. Bacteremia and sepsis rate was similar in both groups (21 vs 18%) and 17 vs 11%) respectively) (p = NS). Antibiotic resistance was more frequent in children with HCA-MRSA: Rifampin (7 vs 1%), trimethoprim-sulphametoxazole (7 vs 1%) and clindamycin (25 vs 9%) (p = < .05). Four children (5%) with HCA-MRSA infections died and 3 (1%) mCA-MRSA group (p = .05).

CONCLUSION

Children with HCA-MRSA infections more frequent antibiotic resistance than CA-MRSA should be reconsider the empiric antibiotic treatment of community-acquired infections in children in our area.

[Community-acquired methicillin-resistant Staphylococcus aureus infections in children: multicenter trial]

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) isolates are increasingly frequent causes of skin and soft-tissue infections or invasive infections in many communities. Local data are scarce.

OBJECTIVE

To determine the frequency, clinical features and outcome of infections caused by MRSA.

MATERIAL AND METHODS

Prospective and multicentric study of surveillance for community-acquired S. aureus infections in children from Argentina. Infections meeting the definition of community-acquired were identified. Demographic and clinical data were collected. Antibiotic susceptibilities were determined in the clinical microbiology laboratory with the methodology of the NCCLS.

RESULTS

From November 2006 to November 2007, 840 S. aureus infections were diagnosed, 447 of them were community-acquired. One hundred and thirty-five children with underlying disease or previous hospital admission were excluded. Two hundred and eighty one (62%) infections were community-acquired MRSA (CA-MRSA). The median age of children was 36 months (r:1-201), 60% were male. Among the CA-MRSA isolates, 62% were obtained from children with skin and soft-tissue infections, and 38% from children with invasive infections. Of them, osteomyelitis, arthritis, empyema and pneumonia were prevalent. Eigthteen percent of children had bacteremia and 11% sepsis. The rate of clindamycin resistance of CA-MRSA isolates was 10% and 1% for trimethoprim-sulfamethoxazole. Only 31% of children had appropriate treatment at admission. The median time of treatment delayed was 72 h. The median time of parenteral treatment was 6 days (r:1-70). In 72% of patients surgical treatment was required. Three children died (1%).

CONCLUSIONS

CA-MRSA isolates account for a high percentage and number of infections in children of Argentina. Community surveillance of CA-MRSA infections is critical to determine the appropriate empiric antibiotic treatment for either local or invasive infections. Clindamycin resistance was under 15% in the strains tested. Clindamycin should be use when CA-MRSA infection is suspected in children.

Expression of GDNF transgene in astrocytes improves cognitive deficits in aged rats

Glial cell line-derived neurotrophic factor (GDNF) was assayed for its neurotrophic effects against the neuronal atrophy that causes cognitive deficits in old age. Aged Fisher 344 rats with impairment in the Morris water maze received intrahippocampal injections at the dorsal CA1 area of either a lentiviral vector encoding human GDNF or the same vector encoding human green fluorescent protein as a control. Recombinant lentiviral vectors constructed with human cytomegalovirus promotor and pseudotyped with lyssavirus Mokola glycoprotein specifically transduced the astrocytes in vivo. Astrocyte-secreted GDNF enhanced neuron function as shown by local increases in synthesis of the neurotransmitters acetylcholine, dopamine and serotonin. This neurotrophic effect led to cognitive improvement of the rats as early as 2 weeks after gene transduction. Spatial learning and memory testing showed a significant gain in cognitive abilities due to GDNF exposure, whereas control-transduced rats kept their performance at the chance level. These results confirm the broad spectrum of the neurotrophic action of GDNF and open new gene therapy possibilities for reducing age-related neurodegeneration.

Sodium butyrate modifies the stabilizing complexes of tyrosine hydroxylase mRNA

Multiple mechanisms regulate the expression of the tyrosine hydroxylase (Th) gene, which encodes the rate-limiting enzyme in the biosynthesis of catecholamines. Sodium butyrate (SOB), a physiological histone deacetylase (HDAC) inhibitor, was reported to stimulate the Th gene promoter activity in reporter gene assays. However, the expression of the endogenous Th gene in PC12 cells was reported to be either stimulated or inhibited by SOB. Here, we report that SOB and other HDAC inhibitors drastically (up to 90%) and reversibly decrease the level of TH mRNA in PC12 cells. We also show that SOB does not influence the transcription initiation rate of the Th gene but perturbs the formation of protein-RNA complexes at the 3'UTR of the gene. Our results suggest that SOB inhibits the expression of the Th gene by destabilizing TH mRNAs.

Primary adult human astrocytes as an ex vivo vehicle for beta-glucuronidase delivery in the brain

Astrocytes are a good candidate cell type for brain transplantation: They are endogenous to the CNS, they have efficient secretory machinery, and they play a major role in neuronal support. We assessed the potential of genetically modified primary adult human astrocytes as vehicles for the delivery of secreted molecules in the mammalian CNS. We report that such cells can be efficiently transduced by a recombinant adenoviral vector carrying the human beta-glucuronidase cDNA (Ad/CMV*beta-glu) and that the transduced astrocytes produce large amounts of the enzyme. Released beta-glucuronidase could be captured, in vitro, by primary neurons and astrocytes and by a neuroblastoma cell line and beta-glucuronidase-deficient fibroblasts. Following grafting into the mouse striatum, adult human astrocytes survived and expressed the transgene for at least 8 weeks. Moreover, the dosage of beta-glucuronidase activity within the grafted brains revealed high enzymatic levels at a long distance from the graft. These experiments document the grafting of engineered primary adult human astrocytes, allowing the release of a secreted therapeutic factor throughout the brain.

The HIV-1 DNA flap stimulates HIV vector-mediated cell transduction in the brain

During HIV-1 reverse transcription, central initiation of the plus-strand DNA at the central polypurine tract (cPPT) and central termination at the central termination sequence (CTS) lead to the formation of a three-stranded DNA structure: the HIV-1 central DNA flap. We recently reported that the DNA flap acts as a cis-active determinant of HIV-1 genome nuclear import. Commonly employed HIV-1-derived vectors (HR vectors) lack the central DNA flap. Here we report that the insertion of this DNA flap sequence into HR vectors (TRIP vectors) improves gene transduction in neural cells, ex vivo and in vivo, in rat brain. When neural cells are exposed to increasing concentrations of TRIP vector particles, transgene expression correlates with the dose of vector. This effect contrasts with the plateau observed when using an HR vector. We further demonstrate that the increase of in vivo transduction efficiency obtained with TRIP vectors is due to the stimulation of their genome nuclear import.

Efficient transduction of neural cells in vitro and in vivo by a baculovirus-derived vector

Gene delivery to the central nervous system is central to the development of gene therapy for neurological diseases. We developed a baculovirus-derived vector, the Bac-CMV-GFP vector, containing a reporter gene encoding for the green fluorescent protein (GFP) under the control of the cytomegalovirus (CMV) promoter. Two neuroblastomal cell lines and three human primary neural cultures could be efficiently transduced. In all cases, addition of butyrate, an inhibitor of histone deacetylase, increased the level of expression in terms of the number of GFP-expressing cells and the intensity of fluorescence. The level of expression in a human telencephalic culture was over 50% of transduced cells with a multiplicity of infection of 25. GFP expression was demonstrated to be genuine expression and not pseudotransduction of the reporter protein. Most interestingly, Bac-CMV-GFP could transduce neural cells in vivo when directly injected into the brain of rodents and was not inactivated by the complement system. Thus, baculovirus is a promising tool for gene transfer into the central nervous system both for studies of the function of foreign genes and the development of gene therapy strategies.

CRE and TRE sequences of the rat tyrosine hydroxylase promoter are required for TH basal expression in adult mice but not in the embryo

Tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of catecholamine neurotransmitters, is expressed in a restricted number of areas, and subject to numerous regulations during development and in adulthood. Two transcription factor binding sites present in the proximal region of the TH gene, the TPA-responsive element (TRE) and the c-AMP responsive element (CRE), have been shown to play important roles in TH gene regulation in vitro. In order to elucidate in vivo the role of these two sites, we produced transgenic mice bearing a 5.3-kb fragment from the 5' flanking sequence of the TH gene with mutations in either the CRE-or TRE-sites. Using the intact 5.3-kb fragment fused to two different reporter genes (HSV1-tk and lacZ), we show that this promoter fragment is able to specifically direct expression in catecholaminergic tissues both in adult mice and embryos. Interestingly, the CRE- and TRE-mutated transgenes were not expressed in adult mice, contrary to the situation in embryos where they were specifically expressed in catecholaminergic regions. These results demonstrate that the CRE and TRE play an essential role in basal TH expression in adult tissues in vivo. Moreover, they suggest that distinct transcription factors are involved in TH regulation in developing and adult tissues. In support of this, gel mobility shift experiments revealed a complex present only in embryonic tissues. Taken together, these data highlight the diversity of the mechanisms underlying the establishment and maintenance of the catecholaminergic phenotype.