Fulvio Erba

Human mast cells take up and hydrolyze anandamide under the control of 5-lipoxygenase and do not express cannabinoid receptors

Human mast cells (HMC‐1) take up anandamide (arachidonoyl‐ethanolamide, AEA) with a saturable process (K m=200±20 nM, V max=25±3 pmol min−1 mg protein−1), enhanced two‐fold over control by nitric oxide‐donors. Internalized AEA was hydrolyzed by a fatty acid amide hydrolase (FAAH), whose activity became measurable only in the presence of 5‐lipoxygenase, but not cyclooxygenase, inhibitors. FAAH (K m=5.0±0.5 μM, V max=160±15 pmol min−1 mg protein−1) was competitively inhibited by palmitoylethanolamide. HMC‐1 cells did not display a functional cannabinoid receptor on their surface and neither AEA nor palmitoylethanolamide affected tryptase release from these cells.

Novel Human Immunodeficiency Virus Type 1 Protease Mutations Potentially Involved in Resistance to Protease Inhibitors

ABSTRACT Plasma-derived sequences of human immunodeficiency virus type 1 (HIV-1) protease from 1,162 patients (457 drug-naïve patients and 705 patients receiving protease inhibitor [PI]-containing antiretroviral regimens) led to the identification and characterization of 17 novel protease mutations potentially associated with resistance to PIs. Fourteen mutations were positively associated with PIs and significantly correlated in pairs and/or clusters with known PI resistance mutations, suggesting their contribution to PI resistance. In particular, E34Q, K43T, and K55R, which were associated with lopinavir treatment, correlated with mutations associated with lopinavir resistance (E34Q with either L33F or F53L, or K43T with I54A) or clustered with multi-PI resistance mutations (K43T with V82A and I54V or V82A, V32I, and I47V, or K55R with V82A, I54V, and M46I). On the other hand, C95F, which was associated with treatment with saquinavir and indinavir, was highly expressed in clusters with either L90M and I93L or V82A and G48V. K45R and K20T, which were associated with nelfinavir treatment, were specifically associated with D30N and N88D and with L90M, respectively. Structural analysis showed that several correlated positions were within 8 Å of each other, confirming the role of the local environment for interactions among mutations. We also identified three protease mutations (T12A, L63Q, and H69N) whose frequencies significantly decreased in PI-treated patients compared with that in drug-naïve patients. They never showed positive correlations with PI resistance mutations; if anything, H69N showed a negative correlation with the compensatory mutations M36I and L10I. These mutations may prevent the appearance of PI resistance mutations, thus increasing the genetic barrier to PI resistance. Overall, our study contributes to a better definition of protease mutational patterns that regulate PI resistance and strongly suggests that other (novel) mutations beyond those currently known to confer resistance should be taken into account to better predict resistance to antiretroviral drugs.

Selective inhibition of human mast cell tryptase by gabexate mesylate, an antiproteinase drug

Gabexate mesylate is a non-antigenic synthetic inhibitor of trypsin-like serine proteinases that is therapeutically used in the treatment of pancreatitis and disseminated intravascular coagulation and as a regional anticoagulant for hemodialysis. Considering the structural similarity between gabexate mesylate and arginine-based inhibitors of trypsin-like serine proteinases, the effect of gabexate mesylate on human and bovine mast cell tryptase action was investigated. Values of the inhibition constant (K(i)) for gabexate mesylate binding to human and bovine tryptase were 3.4 x 10(-9) M and 1.8 x 10(-7) M (at pH 7.4 and 37.0 degrees ), respectively. Furthermore, gabexate mesylate inhibited the fibrinogenolytic activity of human tryptase. On the basis of the available x-ray crystal structure of human tryptase, the possible binding mode of gabexate mesylate to human and bovine tryptase was analyzed. Human tryptase inhibition by gabexate mesylate may account for the reported prevention of inflammation, erosion, and ulceration of skin and mucosae.

Comparison of the Cepheid GeneXpert and Abbott M2000 HIV-1 real time molecular assays for monitoring HIV-1 viral load and detecting HIV-1 infection

Assessing treatment efficacy and early infant diagnosis (EID) are critical issues in HIV disease management. Point-of-care assays may greatly increase the possibility to access laboratory monitoring also in rural areas. Recently two new laboratory tests have been developed by Cepheid (Sunnyvale, California) the Xpert HIV-1 Viral Load for viral load determination and the Xpert HIV-1 Qualitative for early infant diagnosis. We conducted a study in Blantyre, Malawi, comparing the 2 methods versus the Abbott real time quantitative and qualitative assays, for viral load and EID respectively. We tested 300 plasma samples for viral load determination and 200 samples for infant diagnosis. HIV-1 RNA values of the 274 samples quantified by both assays were highly correlated (Pearson r=0.95, R(2)=0.90). In 90.9% of the cases the two methods were concordant in defining the HIV-1 RNA levels as detectable or undetectable. For EID, the Xpert HIV-1 Qualitative assay yielded the same identical results as the Abbott assay. Both the quantitative and the qualitative Xpert assays are promising tools to monitor treatment efficacy in HIV patients receiving treatment and for early diagnosis in HIV-exposed infants.

Association between CYP2B6 polymorphisms and Nevirapine-induced SJS/TEN: a pharmacogenetics study.

PurposeNevirapine (NVP) is a non-nucleoside reverse transcriptase inhibitor, widely prescribed for type 1 human immunodeficiency virus infection. A small proportion of individuals treated with NVP experience severe cutaneous adverse events, including Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Our aim was to verify whether genetic variability in NVP-metabolizing cytochromes or in transporter genes could be involved in susceptibility to SJS/TEN.MethodsTwenty-seven patients with NVP-induced SJS/TEN and 78 controls, all from Mozambique, were genotyped for the ABCB1 and ABCC10 transporter genes and for CYP2B6, CYP3A4 and CYP3A5 cytochrome gene variants. A case–control and a genotype–phenotype analysis were performed.ResultsCYP2B6 G516T and T983C single nucleotide polymorphisms (SNPs) were found to be associated with SJS/TEN susceptibility. The 983C allele in particular was found to be highly associated with a higher risk to develop SJS/TEN [odds ratio (OR) 4.2, P = 0.0047]. The GT haplotype (wildtype for both SNPs) showed a protective effect, with an OR = 0.33 (P = 0.0016).ConclusionsThis is the first study showing that genetic variability in a metabolizing enzyme can also contribute to NVP-induced SJS/TEN susceptibility.

Antiretroviral prophylaxis for breastfeeding transmission in Malawi: drug concentrations, virological efficacy and safety.

BACKGROUND Limited information is available on antiretroviral concentrations in women/infant pairs receiving prophylaxis for breastfeeding transmission of HIV and on the relationship between drug levels and the virological and haematochemistry parameters. METHODS Patient population included HIV-positive pregnant women receiving antiretroviral prophylaxis from gestational week 25 until 6 months after delivery and their breastfed infants. Blood and breast milk samples were collected at delivery, and at months 1, 3 and 6 postpartum. Drug concentrations were measured by liquid chromatography-mass spectrometry. RESULTS Overall, 66 women were studied: 29 received zidovudine (ZDV), lamivudine (3TC) and nevirapine (NVP), 28 stavudine (d4T), 3TC and NVP, and 9 ZDV, 3TC and lopinavir/ritonavir (LPV/r). Women who received >9 weeks of pre-partum prophylaxis were significantly more likely to have an undetectable viral load both in plasma and in breast milk at delivery. No emergence of resistance mutations was observed in breast milk. Breast milk/plasma concentration ratios were 0.6 for ZDV, 3TC and NVP, 1.0 for d4T and 0.4 for LPV/r. Only NVP reached significant levels in the infants. No correlation with any adverse events, including infant anaemia, was observed with drug concentrations. Two infants who acquired HIV infection had non-nucleoside reverse transcriptase inhibitor mutations at month 6. CONCLUSIONS Maternal administration of these three regimens up to 6 months postpartum was effective and safe for both mothers and infants. No significant correlation was found between drug concentrations and infant haematological parameters, supporting the hypothesis that other factors may contribute to the development of anaemia in these settings.

Localization and interaction of bovine pancreatic trypsin inhibitor and tryptase in the granules of bovine mast cells.

The interaction of bovine pancreatic trypsin inhibitor and bovine tryptase, isolated from liver capsule mast cells, was investigated. They form a complex in vitro with a Ki of 5.6 nM at pH 8.0 and are localized within the mast cell granules, as shown by immunogold staining at the electron microscope level. In addition, double immunogold electron microscopy revealed that the inhibitor and the enzyme are present in the same granules, where they occur in clusters; this may be taken as an indication of their interaction in vivo and suggests a physiological role for bovine pancreatic trypsin inhibitor in the regulation of tryptase proteolytic activity.

Evidence for multiple interacting binding sites in bovine tryptase

The interaction of bovine pancreatic trypsin inhibitor (BPTI) and bovine tryptase, which are co‐localized in the same granules of bovine mast cells, has been analyzed at 30°C in 0.1 M Tris‐HCl, pH 8.0. The analysis has unravelled that the functional unit of bovine tryptase is formed of (at least) four binding sites for this inhibitor. These interaction sites display a simple binding behaviour for small inhibitors (and substrates), whereas heterogeneous properties have been observed in the binding of BPTI. Furthermore, in the presence of BPTI, a positive functional interaction can be detected among the binding sites also for a small synthetic inhibitor, like benzamidine. Such features indicate the existence of a complex functional interplay among the sites of the functional unit which is transmitted through the secondary specificity sites.

HCP5 genetic variant (RS3099844) contributes to Nevirapine-induced Stevens Johnsons Syndrome/Toxic Epidermal Necrolysis susceptibility in a population from Mozambique

PurposeNevirapine (NVP) is an anti-retroviral drug used for the treatment of HIV infection, that may cause several severe adverse events, including Stevens Johnsons Syndrome/Toxic Epidermal Necrolysis (SJS/TEN). A recent whole genome association study highlighted a strong association with allopurinol-induced SJS/TEN within the HCP5 and PSORS1C1 genes in the Japanese population. Our aim was to verify the contribution of these two genes in the susceptibility to NVP-induced SJS/TEN in a population from Mozambique.MethodsGenotyping of PSORS1C1 rs2233945 and HCP5 rs3099844 SNPs was performed in a sample of 27 patients with SJS/TEN and 76 controls. A case–control and a haplotype analysis were performed.ResultsThe HCP5 rs3099844 variant allele was significantly associated with the SJS/TEN susceptibility (OR = 2.03 and P = 0.039). The TA haplotype, carrying both the variant alleles of the two genes, showed a higher risk for developing SJS/TEN (OR = 3.44and P = 0.003). The regression analysis confirmed the contribution of HCP5 rs3099844 SNP (OR = 2.05, P = 0.047). By a log-linear model, we also investigated for interaction between HCP5 rs309844 and PSORS1C1 rs2233945 SNPs with respect to SJS/TEN risk, and we observed a strong interaction between the two SNPs (P = 0.005).ConclusionsWe confirmed the association of HCP5 with the SJS/TEN susceptibility in a population from Mozambique treated with NVP.

Emergence of lamivudine resistance hepatitis B virus mutations in pregnant women infected with HBV and HIV receiving antiretroviral prophylaxis for the prevention of mother‐to‐infant transmission in Malawi

HIV/HBV co‐infection is highly prevalent in sub‐Saharan Africa. The aim of this study was to determine if the use of triple combination lamivudine‐containing prophylaxis for the prevention of mother‐to‐infant HIV transmission was associated with the emergence of lamivudine HBV mutations. The study included 21 pregnant co‐infected women in Malawi who received either zidovudine or stavudine plus lamivudine and nevirapine from week 25 of gestation until 6 months after delivery or indefinitely if they met the criteria for treatment (CD4+ <350/mm3). HBV‐DNA was determined using the Roche COBAS assay. Resistance mutations were assessed by the Trugene assay (Siemens Diagnostics). At baseline 33% of the women were HBeAg positive and had HBV‐DNA > 104 IU/ml. Median CD4 count was 237 cells/mm3 and median HIV‐RNA was 3.8 log10 copies/ml. After a median of 259 days of treatment, HBV‐DNA was detectable in 9 out of 21 patients (42.8%). In three cases the HBV‐DNA level was >104 IU/ml. Resistance mutations (M204I in five cases and L180M + M204I/V in one case) were present in 6 (28.6%) patients. Women with a resistant virus had significantly higher baseline HBV‐DNA levels than those not developing resistance (1.1 × 107 IU/ml vs. 20.8 IU/ml, P = 0.022). Levels of ALT and AST were higher in women with resistant viruses compared to those retaining a wild‐type virus. A high rate of lamivudine resistance was seen in this cohort of pregnant women. Follow‐up of these patients will clarify if the presence of resistance has a significant impact on liver disease. J. Med. Virol. 84:1553–1557, 2012.