Measurement of thrombopoietic levels: clinical and biological relationships

Morpholino oligomers targeting the PB1 and NP genes enhance the survival of mice infected with highly pathogenic influenza A H7N7 virus

Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMO) are single-stranded nucleic acid-analogue antisense agents that enter cells readily and can reduce gene expression by steric blocking of complementary RNA (cRNA) sequences. Here, we tested a panel of PPMO designed to target conserved sequences in the RNA genome segments encoding polymerase subunits of a highly pathogenic mouse-adapted influenza A virus (SC35M; H7N7). Three PPMO, targeting the translation start site region of PB1 or NP mRNA or the 3'-terminal region of NP viral RNA (vRNA), potently inhibited virus replication in MDCK cells. Primer extension assays showed that treatment with any of the effective PPMO led to markedly reduced levels of mRNA, cRNA and vRNA. Initially, the potential toxicity of a range of intranasally administered PPMO doses was evaluated, by measuring their effect on body weight of uninfected mice. Subsequently, a non-toxic dosing regimen was used to investigate the effect of various PPMO on SC35M infection in a mouse model. Mice administered intranasal treatment of PPMO targeting the PB1-AUG region or NP vRNA, at 3 mug per dose, given once 3 h before and once 2 days after intranasal infection with 10xLD(50) of SC35M, showed a 2 log(10) reduction of viral titre in the lungs and 50 % survival for the 16 day duration of the experiment, whereas the NP-AUG-targeted PPMO treatment resulted in 30 % survival of an otherwise lethal infection. These data suggest that PPMO provide a useful reagent to investigate influenza virus molecular biology and may constitute a therapeutic strategy against highly pathogenic influenza viruses.

A case of essential thrombocythemia in an 8-year-old boy

Thrombocytosis in childhood is not rare but essential thrombocythemia is an extremely rare myeloproliferative disorder in childhood. The authors report a case of essential thrombocythemia in an 8-year-old boy who was diagnosed during further evaluation of an incidental finding of thrombocythemia in a school health examination.

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Risk factors and kinetics of thrombocytopenia associated with bortezomib for relapsed, refractory multiple myeloma

Bortezomib, a proteasome inhibitor with efficacy in multiple myeloma, is associated with thrombocytopenia, the cause and kinetics of which are different from those of standard cytotoxic agents. We assessed the frequency, kinetics, and mechanism of thrombocytopenia following treatment with bortezomib 1.3 mg/m2 in 228 patients with relapsed and/or refractory myeloma in 2 phase 2 trials. The mean platelet count decreased by approximately 60% during treatment but recovered rapidly between treatments in a cyclic fashion. Among responders, the pretreatment platelet count increased significantly during subsequent cycles of therapy. The mean percent reduction in platelets was independent of baseline platelet count, M-protein concentration, and marrow plasmacytosis. Plasma thrombopoietin levels inversely correlated with platelet count. Murine studies demonstrated a reduction in peripheral platelet count following a single bortezomib dose without negative effects on megakaryocytic cellularity, ploidy, or morphology. These data suggest that bortezomib-induced thrombocytopenia is due to a reversible effect on megakaryocytic function rather than a direct cytotoxic effect on megakaryocytes or their progenitors. The exact mechanism underlying bortezomib-induced thrombocytopenia remains unknown but it is unlikely to be related to marrow injury or decreased thrombopoietin production.

Patterns of thrombocytosis and thrombocytopenia in hospitalized neonates

OBJECTIVE

We sought to identify changes in platelet (PLT) counts over time, and to evaluate the patterns of thrombocytopenia and thrombocytosis in hospitalized infants 23.8 weeks to term gestation.

STUDY DESIGN

Neonates were divided into four gestational age groups and their PLT counts were retrospectively compared for prevalence of thrombocytopenia, thrombocytosis, and associated conditions.

RESULTS

Postconceptional age, postnatal age, and sepsis (among other factors) affected PLT counts. When counts from noninfected appropriately grown infants were evaluated, the risk of thrombocytopenia and thrombocytosis were highest in the most preterm infants, and these risks changed with corrected gestational age. PLT counts increased weekly over the first 4 weeks of life for all but the most preterm infants.

CONCLUSIONS

These data characterize the incidence of thrombocytopenia and thrombocytosis across a wide range of gestational ages and show that, even in noninfected neonates, these conditions are common, and risk decreases with increasing maturity. The age-related changes in PLT patterns may reflect maturation of platelet regulation.

Elevation of serum thrombopoietin precedes thrombocytosis in acute infections

To clarify the mechanisms underlying thrombocytosis secondary to infections, we longitudinally studied serum levels of thrombopoietin (TPO) and interleukin (IL)-6 in 15 infants and young children with prominent thrombocytosis (platelets >700 x 10(9)/l) following acute infections and 116 age-matched controls using an enzyme-linked immunosorbent assay. The subjects included nine patients with bacterial infections, three with viral infections and three with non-determined pathogens. TPO values in the controls were 2.24 +/- 0.87 fmol/ml (mean +/- SD) with a 95% reference interval of 0.85-4.47 fmol/ml. In the first week of infection, platelet counts were normal, but TPO values increased (approximately 10.73 fmol/ml). TPO levels peaked on day 4 +/- 2 at 6.44 +/- 2.37 fmol/ml and then fell gradually. When platelet counts peaked in the second and third weeks, TPO levels were similar to the controls. IL-6 levels in the first week rose and dropped more rapidly than TPO. Serum TPO values were significantly correlated with C-reactive protein levels (r = 0.688, P < 0.001) and IL-6 levels (r = 0.481, P = 0.027). These results suggest that TPO contributes to thrombocytosis following infections in conjunction with IL-6, arguing for additional regulatory mechanisms of blood TPO levels.

Thrombocytosis and thrombocythemia

Thrombocytosis is caused by three major pathophysiological mechanisms: (1) reactive or secondary thrombocytosis; (2) familial thrombocytosis; and (3) clonal thrombocytosis, including essential thrombocythemia and related myeloproliferative disorders. Recent work has begun to elucidate the abnormal megakaryocytopoiesis of essential thrombocythemia, which is associated with paradoxically elevated plasma levels of thrombopoietin. The clonal nature of all cases of essential thrombocythemia has been challenged. Thrombotic complications are the major causes of morbidity and mortality in this disease. Indications for platelet cytoreduction and antiplatelet therapy, as well as complications of treatment, are being clarified.

Early elevation of serum thrombopoietin levels and subsequent thrombocytosis in healthy preterm infants

To verify pathophysiological mechanisms underlying thrombocytosis in low-birth-weight (LBW) preterm babies, we evaluated kinetic changes in platelet counts and thrombopoietic cytokines including thrombopoietin (TPO), interleukin 6 (IL-6) and IL-11 in 24 uncomplicated preterm infants. Platelet counts in cord blood (CB) (265 +/- 64 x 10(9)/l) were similar to adult levels, increased by d 14 (473 +/- 140 x 10(9)/l), and then remained fairly constant. Thrombocytosis (> 500 x 10(9)/l) was observed in 9/24 (38%) subjects. Mean TPO level in CB was 5.11 +/- 1.51 fmol/ml, peaked at d 2 (7.64 +/- 3.28 fmol/ml), decreased at d 5 (3.93 +/- 1.67 fmol/ml), and thereafter kept fairly constant during the remaining neonatal period. Compared with term infants, mean TPO levels of preterm infants in CB and at d 2 were significantly higher (P < 0.01). There was an inverse correlation between platelet counts and TPO levels (r = 0.45, P < 0.001, n = 88). Preterm neonates with thrombocytosis had significantly higher TPO values in CB than those without thrombocytosis (P < 0.05). There was no significant relationship between platelet counts and IL-6. IL-11 was not detectable. These results suggest that an early elevation of serum TPO levels is related to the subsequent thrombocytosis in LBW preterm infants.

Neonatal thrombocytosis resulting from the maternal use of non-narcotic antischizophrenic drugs during pregnancy

Neonatal thrombocytosis can result from maternal narcotic drug abuse. The case of a male infant is reported who was born to a woman with schizophrenia treated with non-narcotic psychotropic drugs during pregnancy; he developed severe prolonged thrombocytosis. The platelet count reached 1310 x 10(9)/l on day 15. This thrombocytosis persisted for three months. The patient was treated with dipyridamole. A bone marrow aspirate showed normal myeloid and erythroid precursors with an increased number of megakaryocytes. Plasma concentrations of interleukin 6 and thrombopoietin were suppressed. No obvious complications from the thrombocytosis occurred, and the platelet count fell to within the upper limit of normal after 3 months of age. This case indicates that thrombocytosis may occur in infants born to mothers treated with non-narcotic psychopharmaceutical drugs during pregnancy. The thrombocytosis in this case may have been induced by factors other than interleukin 6 or thrombopoietin.

Familial thrombocytosis as a recessive, possibly X-linked trait in an Arab family

Familial thrombocytosis (FT) has previously been described as an autosomal-dominant disorder with manifestations similar to those of sporadic essential thrombocythaemia. We studied an Arab family consisting of four brothers, aged 4-8 years, who had either sustained markedly elevated (> 1000 x 109/l) or moderately elevated (> 500 x 109/l) platelet counts, two healthy sisters and their parents who had normal platelet counts. The four brothers with FT had normal plasma thrombopoietin levels and are currently not presenting with any thrombotic or haemorrhagic complications. Mutation analysis at the thrombopoietin gene (THPO) of the affected family members failed to detect the intron 3 G-->C splice mutation that had been described as causing FT. In addition, segregation analysis using a polymorphic CA marker revealed completely discordant THPO alleles among the affected brothers. We postulate the existence of a new locus for FT whereby the disease is transmitted as a recessive, possibly X-linked trait.