Fecal Microbiota Transplantation for Refractory Clostridioides Difficile Infection Is Effective and Well Tolerated Even in Very Old Subjects: A Real-Life Study.

OBJECTIVES: Fecal microbiota transplantation (FMT) is an innovative therapy indicated for the treatment of recurrent Clostridioides difficile infections. Although CDI and its complications are more common in very old patients (≥80 years) due to their comorbidities, frailty and senescence of the immune system, limited data are available for this older patient population. DESIGN: This was a single-center, real-life cohort study with retrospective outcome data registration, conducted at Toulouse, France. SETTING AND PARTICIPANTS: Older people group was compared to the control group aged 18-79 years. MEASUREMENTS: The primary outcome was overall survival at 52 weeks for ≥80 years patients compared to the control group after FMT. Recurrence-free survival at 52 weeks and, the occurrence of adverse events in the short and long term were the secondary endpoints. RESULTS: A total of 58 patients were included, 19 were aged ≥80 years and 39 were aged 18-79 years. Overall survival at 52 weeks after FMT of the very old patients was not different from the control group (78.9% versus 89.7%, p= 0.29). Recurrence-free survival of CDI was not different between groups, with 94.3% in the 18-79-group versus 86.9% in the ≥80 group (p=0.44). The occurrence of short- or long-term adverse events was not statistically different between the two groups (36.8% vs 41%, p=0.45). CONCLUSIONS: FMT is effective and well-tolerated in very old frail patients. This treatment brings a rapid benefit and limits the loss of functions. It also favors their maintenance at home or in a non-medical institution dedicated to dependent subjects and improves their quality of life.

Severe adverse events during medical and surgical treatment of hip and knee prosthetic joint infections.

INTRODUCTION: The management of prosthetic joint infection requires a complex treatment procedure and can be associated with complications. However, the occurrence of severe adverse events during this intervention has been poorly evaluated. PATIENTS AND METHODS: A 5-year multicentric retrospective study including patients from 3 hospitals in the South-Western France referral center for complex bone and joint infections (Crioac GSO) and treated for hip or knee prosthetic joint infection with 1 or 2-stage implant exchanges. The objective was to describe grade≥3 adverse events, according to the CTCAE classification, occurring within 6 weeks after surgery and to identify their associated factors. RESULTS: One hundred and eighteen patients were identified. We observed 71 severe events in 50 patients (42.3%; 95% confidence interval [CI95%]: 33.8-51.4%). Sixteen severe events were an evolution of the infection. The remaining 55 others (47 grade 3 and 8 grade 4) occurred in 41 patients (34.7%; CI95%: 26.8-43.7%). They were distributed as follows: 27 (49.1%) medical complications, 21 (38.2%) surgical complications and 7 (12.7%) antibiotic-related complications. The main identified risk factor was a two-stage prosthetic exchange with OR=3.6 (CI95% [1.11-11.94], P=0.032). Obesity was limit of significance with OR=3.3 (CI95% [0.9-12.51], P=0.071). Infection with coagulase negative Staphylococcus was a protective factor with OR=0.3 (CI95% [0.12-0.99], P=0.047). CONCLUSION: Severe adverse events are frequent following prosthetic exchange for PJI (34.7%) and are related to the high frequency of comorbidities in this population and to the complex surgical procedures required. The risk factor significantly associated with these events was a two-stage exchange.

Clinical characteristics and outcome of hospitalized patients with SARS-CoV-2 infection at Toulouse University hospital (France). Results from the Covid-clinic-Toul cohort.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has spread worldwide from epicenter of Wuhan, China since December 2019. The aim of our study was to describe the clinical characteristics and outcome of hospitalized patients with SARS-CoV-2 pneumonia at the Toulouse university hospital, France. PATIENTS AND METHODS: We selected the patients included from March 7, 2020 to April 20, 2020 in the retrolective Covid-clinic-Toul cohort that follows all hospitalized patients with SARS-CoV-2 infection at the Toulouse Hospital. Cases were confirmed by real-time reverse transcriptase polymerase chain reaction. We report demographics, clinical, biological and radiological features, as well as unfavorable outcome at Day 14 after admission (admission in an intensive care unit, mechanical ventilation, death). RESULTS: Among 263 hospitalized patients, the median age was 65 years and 155 (58.9%) were males. Two hundred and twenty-seven patients (86.3%) had at least one comorbidity. The median time from first symptom to hospital admission was 7.0 days (interquartile range: 4-10). On day 14 after admission, 111 patients (42.2%) had been transferred to intensive care unit (ICU), including 50 (19.0%) on Day 1; 61 (23.1%) needed mechanical ventilation and 19 patients (7.2%) had died. Patients admitted to ICU at Day 1 of admission (n=50) were more frequently men (66.0% vs 57.3%), smokers (25.0% vs 7.1%), with obesity (42.0% vs 24.7%) and had a higher mean level of C-reactive protein (median: 110.9mg/L vs 46.2mg/L). CONCLUSION: This cohort provides epidemiological data on SARS-CoV-2 in hospitalized patients in a University hospital in the South of France.

COVID-19, Virology and Geroscience: A Perspective.

A new coronavirus, called SARS-CoV-2, was identified in Wuhan, China, in December 2019. The SARS-CoV-2 spread very rapidly, causing a global pandemic, Coronavirus Disease 2019 (COVID-19). Older adults have higher peak of viral load and, especially those with comorbidities, had higher COVID-19-related fatality rates than younger adults. In this Perspective paper, we summarize current knowledge about SARS-CoV-2 and aging, in order to understand why older people are more affected by COVID-19. We discuss about the possibility that the so-called "immunosenescence" and "inflammaging" processes, already present in a fraction of frail older adults, could allow the immune escape of SARS-CoV-2 leading to COVID-19 serious complications. Finally, we propose to use geroscience approaches to the field of COVID-19.

Kaposi sarcoma among people living with HIV in the French DAT'AIDS cohort between 2010 and 2015.

BACKGROUND: Although antiretroviral therapy (ART) has reduced the risk of Kaposi sarcoma (KS), KS cases still occur in HIV-infected people. OBJECTIVE: To describe all KS cases observed between 2010 and 2015 in a country with high ART coverage. METHODS: Retrospective study using longitudinal data from 44 642 patients in the French Dat'AIDS multicenter cohort. Patients' characteristics were described at KS diagnosis according to ART exposure and to HIV-plasma viral load (HIV-pVL) (≤50 or >50) copies/mL. RESULTS: Among the 209 KS cases diagnosed during the study period, 33.2% occurred in ART naïve patients, 17.3% in ART-experienced patients and 49.5% in patients on ART, of whom 23% for more than 6 months. Among these patients, 24 (11.5%) had HIV-pVL ≤50 cp/mL, and 16 (66%) were treated with a boosted-PI-based regimen. The distribution of KS localization did not differ by ART status nor by year of diagnosis. LIMITATIONS: Data on human herpesvirus 8, treatment modalities for KS and response rate were not collected. CONCLUSION: Half of KS cases observed in the study period occurred in patients not on ART, reflecting the persistence of late HIV diagnosis. Factors associated with KS in patients on ART with HIV-pVL ≤50 cp/mL remain to be explored.

Too fast to stay on track? Shorter time to first anti-retroviral regimen is not associated with better retention in care in the French Dat'AIDS cohort.

BACKGROUND: Rapid antiretroviral therapy (ART) initiation has been proven beneficial for patients and the community. We aimed to analyze recent changes in timing of ART initiation in France and consequences of early start. METHODS: We selected from a prospective nationwide cohort, on 12/31/2017, patients with HIV-1 infection diagnosed between 01/01/2010 and 12/31/2015. We described time from (1) diagnosis to first specialized medical encounter, (2) from this encounter to ART initiation, (3) from diagnosis to first undetectable HIV viral load (VL). We analyzed the determinants of measured temporal trends. A multivariate logistic regression was performed to assess characteristics related with 1-year retention in care. RESULTS: In the 7 245 included patients, median time (1) from HIV diagnosis to first medical encounter was 13 (IQR: 6-32) days, (2) to ART initiation was 27 (IQR: 9-91) days, decreasing from 42 (IQR: 13-272) days in 2010 to 18 (IQR: 7-42) in 2015 (p<0.0001), (3) to first undetectable VL was 257 (IQR: 151-496) days, decreasing from 378 (IQR: 201-810) days in 2010 to 169 (IQR: 97-281) in 2015. After one year, proportion of patients alive and still in care was significantly lower in those in the lower quartile of time from first encounter to ART (<9 days) than those in the higher quartile (>90 days), 79.9% and 85.2%, respectively (p<0.0001). CONCLUSIONS: In a country with unrestricted rapid access to ART, keeping recently diagnosed HIV infected patients in care remains challenging. Starting ART rapidly did not seem to be profitable for all and every patient.

Increased CXCR3+ T Cells Impairs Recruitment of T-Helper Type 17 Cells via Interferon γ and Interleukin 18 in the Small Intestine Mucosa During Treated HIV-1 Infection.

The restoration of CD4+ T cells, especially T-helper type 17 (Th17) cells, remains incomplete in the gut mucosa of most human immunodeficiency virus type 1 (HIV-1)-infected individuals despite sustained antiretroviral therapy (ART). Herein, we report an increase in the absolute number of CXCR3+ T cells in the duodenal mucosa during ART. The frequencies of Th1 and CXCR3+ CD8+ T cells were increased and negatively correlated with CCL20 and CCL25 expression in the mucosa. In ex vivo analyses, we showed that interferon γ, the main cytokine produced by Th1 and effector CD8+ T cells, downregulates the expression of CCL20 and CCL25 by small intestine enterocytes, while it increases the expression of CXCL9/10/11, the ligands of CXCR3. Interleukin 18, a pro-Th1 cytokine produced by enterocytes, also contributes to the downregulation of CCL20 expression and increases interferon γ production by Th1 cells. This could perpetuate an amplification loop for CXCR3-driven Th1 and effector CD8+ T cells recruitment to the gut, while impairing Th17 cells homing through the CCR6-CCL20 axis in treated HIV-1-infected individuals.

Antiretroviral unbound concentration during pregnancy: piece of interest in the puzzle?

Atazanavir and darunavir total concentrations (drug bound to plasma proteins plus unbound drug) progressively decrease during pregnancy. This pharmacokinetic variation leads physicians to recommend increasing doses. Conversely, the unbound concentration (Cu), i.e. the pharmacologically active form of the drug, remains unchanged. The explanation of this desynchronization lies in the fact that the clearance of the unbound form, corresponding to the intrinsic metabolic capacity of the hepatocytes, is the only factor driving Cu, and is constant during pregnancy. The attention of HIV physicians should be attracted to this aspect of pharmacokinetics, which is often incompletely understood and could lead to inadequate dose adjustment, which could then cause overexposure of the foetus for many months, with unknown consequences.

CCR6(-) regulatory T cells blunt the restoration of gut Th17 cells along the CCR6-CCL20 axis in treated HIV-1-infected individuals.

The gut CD4(+) T cells, particularly the T helper type 17 (Th17) subset, are not completely restored in most HIV-1-infected individuals despite combined antiretroviral therapy, when initiated at the chronic phase of infection. We show here that the CCR6-CCL20 chemotactic axis is altered, with reduced CCL20 production by small intestine epithelial cells in treated HIV-1-infected individuals. This leads to impaired CCR6(+)CD4(+) T-cell homing, particularly Th17 cells, to the small intestine mucosa. In contrast, the frequency of gut FoxP3(+) T regulatory (Treg) cells, specifically the CCR6(-) subset, was increased. The resulting imbalance in the Th17/CCR6(-) Treg ratio and the associated shift from interleukin (IL)-17 to IL-10 and transforming growth factor-ß (TGF-ß) blunts CCL20 production by enterocytes, perpetuating a negative feedback for the recruitment of CCR6(+)CD4(+) T cells to the small intestine in treated HIV-1-infected individuals.

Minority resistant HIV-1 variants and the response to first-line NNRTI therapy.

BACKGROUND: The presence of low-frequency HIV-1 variants with mutations making them resistant to non-nucleoside reverse-transcriptase inhibitors (NNRTI) could influence the virological response to first-line NNRTI therapy. OBJECTIVES: This study was designed to describe the proportions and quantities of NRTI and NNRTI-resistant variants in patients with successful first-line NNRTI therapy. STUDY DESIGN: We evaluated the presence of drug-resistance mutations (DRMs) prior to treatment initiation in 131 naive chronically HIV-1-infected patients initiating NNRTI-based first-line therapy. DRMs were detected by ultradeep pyrosequencing (UDPS) on a GS Junior instrument (Roche). RESULTS: The mean HIV RNA concentration was 4.78 ± 0.74 log copies/mL and the mean CD4 cell count was 368 ± 184 CD4 cells/mm(3). Patients were mainly infected with subtype B (68%) and 96% were treated with efavirenz. The sensitivity threshold for each mutation was 0.13-1.05% for 2000 reads. Major NRTI-resistant or NNRTI-resistant mutations were detected in 40 patients (33.6%). The median frequency of major NRTI-resistant mutations was 1.37% [IQR: 0.39-84.1], i.e.: a median of 556 copies/mL [IQR: 123-37,553]. The median frequency of major NNRTI-resistant DRMs was 0.78% [IQR: 0.67-7.06], i.e.: a median of 715 copies/mL [IQR: 391-3452]. The genotypic susceptibility score (GSS) of 9 (7.3%) patients with mutations to given treatment detected by UDPS was 1.5 or 2. CONCLUSIONS: First-line NNRTI-based treatment can produce virological success in naïve HIV-1-infected patients harboring low-frequency DRMs representing <1% of the viral quasispecies. Further studies are needed to determine the clinical cut-off of low-frequency resistant variants associated to virological failure.

FDG-PET/CT findings during immune reconstitution in an HIV-1 patient infected with visceral leishmaniasis.

Visceral leishmaniasis can rarely be unmasked by immune reconstitution in human immunodeficiency virus (HIV)-1-infected patients. We report the first case of immune reconstitution associated with leishmaniasis in an HIV patient to be imaged with [(18)F]fluorodeoxyglucose positron emission tomography (FDG/PET), at both baseline and after therapy.

A 'fragile cell' sub-population revealed during cytometric assessment of Saccharomyces cerevisiae viability in lipid-limited alcoholic fermentation.

AIMS: To show that in anaerobic fermentation with limiting lipid nutrients, cell preparation impacts the viability assessment of yeast cells, and to identify the factors involved. METHODS AND RESULTS: Saccharomyces cerevisiae viability was determined using propidium iodide staining and the flow cytometry. Analyses identified intact cells, dead cells and, under certain conditions, the presence of a third subpopulation of apparently damaged cells. This intermediate population could account for up to 40% of the entire cell population. We describe, analyse and discuss the effects of different solutions for cell resuspension on the respective proportion of these three populations, in particular that of the intermediate population. We show that this intermediate cell population forms in the absence of Ca(2+)/Mg(2+). CONCLUSIONS: Cell preparation significantly impacts population viability assessment by FCM. The intermediate population, revealed under certain conditions, could be renamed as 'fragile cells'. For these cells, Ca(2+) and Mg(2+) reduce cell membrane permeability to PI. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study that analyses and discusses the factors influencing the formation of an intermediate population when studying viability in yeast alcoholic fermentation. With a wider application in biological research, this study provides important support to the relatively new questioning of propidium iodide staining as a universal cell death indicator.

Minority variants associated with resistance to HIV-1 nonnucleoside reverse transcriptase inhibitors during primary infection.

BACKGROUND: Recent data suggest that subjects harbouring low-frequency variants of HIV that are resistant to non-nucleoside reverse-transcriptase inhibitors (NNRTI) could suffer virological failure when treated with NNRTI-based therapy. Rilpivirine, a second-generation NNRTI, will be used in first-line regimen therapy, but the prevalence of minority variants that are resistant to rilpivirine is unknown. OBJECTIVES: We evaluated the presence of low-frequency NNRTI resistance associated mutations (RAMs) in 27 patients with a primary HIV-1 infection. STUDY DESIGN: We performed genotypic resistance test at baseline and used ultradeep pyrosequencing (UDPS) to detect minority RAMs. RESULTS: Bulk genotyping identified NNRTI-resistant RAMs in 3/27 (11%) patients while UDPS identified NNRTI-resistant RAMs in 10/27 (37%) patients. The 11 RAMs not detected by bulk sequencing were A98G (n=2), L100I (n=3), K101E (n=2), V106I (n=3) and E138G (n=1). The prevalence of these minority variants was 0.34-18.26%. The absolute copy numbers of minority resistant variants were 3.21-5.53 log copies/mL. CRF02 harboured more minority resistant variants than subtypes B (P<0.05). Four samples (15%) had a major rilpivirine resistant mutation (E138G, K101E and E138A), 3 of which were detected by UDPS. CONCLUSION: In these primary HIV infected patients, as regards to the detection of RAMs at the cut-off level>15-25% of the virus population, the concordance between bulk genotypic and UDPS was perfect. UDPS detected additional major NNRTI-resistant mutations, including rilpivirine resistant variants. Further studies are needed to assess the impact of these minority variants on treatment efficacy.

Factors associated with a strictly undetectable viral load in HIV-1-infected patients.

OBJECTIVES: The aim of the study was to identify factors associated with a strictly undetectable viral load (VL) using a routine sensitive real-time polymerase chain reaction (RT-PCR) technology. METHODS: From a large prospective cohort, 1392 patients with a VL<50 HIV-1 RNA copies/mL while receiving a three-drug suppressive regimen for at least 1 year were included in a cross-sectional analysis. Patients were classified into three groups and compared by univariate and multivariate analysis: 479 patients with a strictly undetectable VL (group 1; 34%), 617 patients with detectable VL below the threshold of 20 copies/mL (group 2; 44%), and 296 patients with a VL of 20-50 copies/mL (group 3; 12%). RESULTS: Comparing groups 1 and 2, VL zenith<5 log(10) copies/mL [odds ratio (OR) 1.51; 95% confidence interval (CI) 1.15-1.99; P=0.003], current CD4 T-cell count<500 cells/µL (OR 1.44; 95% CI 1.08-1.92; P=0.01), and duration of viral suppression<50 copies/mL longer than 2 years (OR 2.32; 95% CI 1.20-4.54; P=0.01) were associated with undetectable VL. Comparing groups 1 and 3, VL zenith<5 log(10) copies/mL (OR 2.48; 95% CI 1.75-3.50; P<0.001), duration of viral suppression<50 copies/mL longer than 1 year (OR 3.33; 95% CI 1.66-6.66; P=0.0006), and nonnucleoside reverse transcriptase inhibitor (NNRTI)-based regimens (OR 1.45; 95% CI 1.03-2.04; P=0.03) were associated with undetectable VL. No individual drug effect was found within NNRTI molecules. CONCLUSIONS: Longer duration of viral suppression<50 copies/mL, lower viral load zenith and NNRTI-based regimen were independently associated with a strictly undetectable viral load. This routinely used RT-PCR assay may prove to be a valuable tool in further large-scale studies.

Ecological success of a group of Saccharomyces cerevisiae/Saccharomyces kudriavzevii hybrids in the northern european wine-making environment.

The hybrid nature of lager-brewing yeast strains has been known for 25 years; however, yeast hybrids have only recently been described in cider and wine fermentations. In this study, we characterized the hybrid genomes and the relatedness of the Eg8 industrial yeast strain and of 24 Saccharomyces cerevisiae/Saccharomyces kudriavzevii hybrid yeast strains used for wine making in France (Alsace), Germany, Hungary, and the United States. An array-based comparative genome hybridization (aCGH) profile of the Eg8 genome revealed a typical chimeric profile. Measurement of hybrids DNA content per cell by flow cytometry revealed multiple ploidy levels (2n, 3n, or 4n), and restriction fragment length polymorphism analysis of 22 genes indicated variable amounts of S. kudriavzevii genetic content in three representative strains. We developed microsatellite markers for S. kudriavzevii and used them to analyze the diversity of a population isolated from oaks in Ardèche (France). This analysis revealed new insights into the diversity of this species. We then analyzed the diversity of the wine hybrids for 12 S. cerevisiae and 7 S. kudriavzevii microsatellite loci and found that these strains are the products of multiple hybridization events between several S. cerevisiae wine yeast isolates and various S. kudriavzevii strains. The Eg8 lineage appeared remarkable, since it harbors strains found over a wide geographic area, and the interstrain divergence measured with a (δµ)(2) genetic distance indicates an ancient origin. These findings reflect the specific adaptations made by S. cerevisiae/S. kudriavzevii cryophilic hybrids to winery environments in cool climates.

Activation of two different resistance mechanisms in Saccharomyces cerevisiae upon exposure to octanoic and decanoic acids.

Medium-chain fatty acids (octanoic and decanoic acids) are well known as fermentation inhibitors. During must fermentation, the toxicity of these fatty acids is enhanced by ethanol and low pH, which favors their entrance in the cell, resulting in a decrease of internal pH. We present here the characterization of the mechanisms involved in the establishment of the resistance to these fatty acids. The analysis of the transcriptome response to the exposure to octanoic and decanoic acids revealed that two partially overlapping mechanisms are activated; both responses share many genes with an oxidative stress response, but some key genes were activated differentially. The transcriptome response to octanoic acid stress can be described mainly as a weak acid response, and it involves Pdr12p as the main transporter. The phenotypic analysis of knocked-out strains confirmed the role of the Pdr12p transporter under the control of WAR1 but also revealed the involvement of the Tpo1p major facilitator superfamily proteins (MFS) transporter in octanoic acid expulsion. In contrast, the resistance to decanoic acid is composite. It also involves the transporter Tpo1p and includes the activation of several genes of the beta-oxidation pathway and ethyl ester synthesis. Indeed, the induction of FAA1 and EEB1, coding for a long-chain fatty acyl coenzyme A synthetase and an alcohol acyltransferase, respectively, suggests a detoxification pathway through the production of decanoate ethyl ester. These results are confirmed by the sensitivity of strains bearing deletions for the transcription factors encoded by PDR1, STB5, OAF1, and PIP2 genes.

[Impact of malaria on HIV infection]. / Impact du paludisme sur l'infection par le VIH.

Malaria and HIV are two major public health issues, especially in sub-Saharan Africa. HIV infection increases the incidence of clinical malaria, inversely correlated with the degree of immunodepression. The effect of malaria on HIV infection is not as well established. Malaria, when fever and parasitemia are high, may be associated with transient increases in HIV viral load. The effect of subclinical malaria on HIV viral load is uncertain. During pregnancy, placental malaria is associated with higher plasma and placental HIV viral loads, independently of the severity of immunodeficiency. However, the clinical impact of these transient increases of HIV viral load remains unknown. Although some data suggests that malaria might enhance sexual and mother-to-child transmissions, no clinical study has confirmed this. Nevertheless pregnant women and children with malaria-induced anemia are also exposed to HIV through blood transfusions. Integrated HIV and malaria control programs in the regions where both infections overlap are necessary.

Low interleukin-10 production by monocytes of patients with a self-limiting hepatitis C virus infection.

Host factors seem to be crucial for the spontaneous clearance of hepatitis C virus (HCV). Monocytes play a pivotal role in innate immunity and help regulate adaptive responses. This study assesses the characteristics of monocytes from patients with self-limiting HCV infections. We studied 35 consecutive patients [11 with a self-limiting HCV infection, 16 chronically infected with HCV and sustained virological responders (SVR) following antiviral therapy, and eight chronically infected HCV but untreated] and eight healthy donors (HD). The production of interleukin (IL)-10, tumour necrosis factor-alpha (TNF-alpha) and IL-12p40 by monocytes stimulated with lipopolysaccharides(LPS) or HCV Core protein was measured by enzyme-linked immunoassay. Monocyte surface markers were analysed by flow cytometry. LPS and Core protein triggered IL-10 and TNF-alpha production, but monocytes from self-limiting infection patients produced significantly less IL-10 and TNF-alpha than those of SVR, chronically infected or HD (P < 0.05), while IL-12p40 production was unchanged. This cytokine production profile did not appear to be due to expansion of the CD14(+) CD16(+) monocyte subset or to a classical or alternative activation monocyte profile. Monocytes from self-limiting infection patients had more CCR7 than those from SVR or chronically infected patients (P < 0.05). Monocytes of self-limiting infection patients appear to produce little IL-10 and TNF-alpha in response to viral or unspecific stimulation and to have a higher CCR7 expression. This profile seems to be independent to a particular monocyte subset or activation state. Low IL-10 production may help establish an effective immune response and spontaneous HCV clearance.

Gene expression profiling of Spodoptera frugiperda hemocytes and fat body using cDNA microarray reveals polydnavirus-associated variations in lepidopteran host genes transcript levels.

BACKGROUND: Genomic approaches provide unique opportunities to study interactions of insects with their pathogens. We developed a cDNA microarray to analyze the gene transcription profile of the lepidopteran pest Spodoptera frugiperda in response to injection of the polydnavirus HdIV associated with the ichneumonid wasp Hyposoter didymator. Polydnaviruses are associated with parasitic ichneumonoid wasps and are required for their development within the lepidopteran host, in which they act as potent immunosuppressive pathogens. In this study, we analyzed transcriptional variations in the two main effectors of the insect immune response, the hemocytes and the fat body, after injection of filter-purified HdIV. RESULTS: Results show that 24 hours post-injection, about 4% of the 1750 arrayed host genes display changes in their transcript levels with a large proportion (76%) showing a decrease. As a comparison, in S. frugiperda fat body, after injection of the pathogenic JcDNV densovirus, 8 genes display significant changes in their transcript level. They differ from the 7 affected by HdIV and, as opposed to HdIV injection, are all up-regulated. Interestingly, several of the genes that are modulated by HdIV injection have been shown to be involved in lepidopteran innate immunity. Levels of transcripts related to calreticulin, prophenoloxidase-activating enzyme, immulectin-2 and a novel lepidopteran scavenger receptor are decreased in hemocytes of HdIV-injected caterpillars. This was confirmed by quantitative RT-PCR analysis but not observed after injection of heat-inactivated HdIV. Conversely, an increased level of transcripts was found for a galactose-binding lectin and, surprisingly, for the prophenoloxidase subunits. The results obtained suggest that HdIV injection affects transcript levels of genes encoding different components of the host immune response (non-self recognition, humoral and cellular responses). CONCLUSION: This analysis of the host-polydnavirus interactions by a microarray approach indicates that the presence of HdIV induces, directly or indirectly, variations in transcript levels of specific host genes, changes that could be responsible in part for the alterations observed in the parasitized host physiology. Development of such global approaches will allow a better understanding of the strategies employed by parasites to manipulate their host physiology, and will permit the identification of potential targets of the immunosuppressive polydnaviruses.