MERS-CoV ORF4b is a virulence factor involved in the inflammatory pathology induced in the lungs of mice

No vaccines or specific antiviral drugs are authorized against Middle East respiratory syndrome coronavirus (MERS-CoV) despite its high mortality rate and prevalence in dromedary camels. Since 2012, MERS-CoV has been causing sporadic zoonotic infections in humans, which poses a risk of genetic evolution to become a pandemic virus. MERS-CoV genome encodes five accessory proteins, 3, 4a, 4b, 5 and 8b for which limited information is available in the context of infection. This work describes 4b as a virulence factor in vivo, since the deletion mutant of a mouse-adapted MERS-CoV-Δ4b (MERS-CoV-MA-Δ4b) was completely attenuated in a humanized DPP4 knock-in mouse model, resulting in no mortality. Attenuation in the absence of 4b was associated with a significant reduction in lung pathology and chemokine expression levels at 4 and 6 days post-infection, suggesting that 4b contributed to the induction of lung inflammatory pathology. The accumulation of 4b in the nucleus in vivo was not relevant to virulence, since deletion of its nuclear localization signal led to 100% mortality. Interestingly, the presence of 4b protein was found to regulate autophagy in the lungs of mice, leading to upregulation of BECN1, ATG3 and LC3A mRNA. Further analysis in MRC-5 cell line showed that, in the context of infection, MERS-CoV-MA 4b inhibited autophagy, as confirmed by the increase of p62 and the decrease of ULK1 protein levels, either by direct or indirect mechanisms. Together, these results correlated autophagy activation in the absence of 4b with downregulation of a pathogenic inflammatory response, thus contributing to attenuation of MERS-CoV-MA-Δ4b.

MERS-CoV 4b protein interferes with the NF-κB-dependent innate immune response during infection

Middle East respiratory syndrome coronavirus (MERS-CoV) is a novel human coronavirus that emerged in 2012, causing severe pneumonia and acute respiratory distress syndrome (ARDS), with a case fatality rate of ~36%. When expressed in isolation, CoV accessory proteins have been shown to interfere with innate antiviral signaling pathways. However, there is limited information on the specific contribution of MERS-CoV accessory protein 4b to the repression of the innate antiviral response in the context of infection. We found that MERS-CoV 4b was required to prevent a robust NF-κB dependent response during infection. In wild-type virus infected cells, 4b localized to the nucleus, while NF-κB was retained in the cytoplasm. In contrast, in the absence of 4b or in the presence of cytoplasmic 4b mutants lacking a nuclear localization signal (NLS), NF-κB was translocated to the nucleus leading to the expression of pro-inflammatory cytokines. This indicates that NF-κB repression required the nuclear import of 4b mediated by a specific NLS. Interestingly, we also found that both in isolation and during infection, 4b interacted with α-karyopherin proteins in an NLS-dependent manner. In particular, 4b had a strong preference for binding karyopherin-α4 (KPNA4), which is known to translocate the NF-κB protein complex into the nucleus. Binding of 4b to KPNA4 during infection inhibited its interaction with NF-κB-p65 subunit. Thereby we propose a model where 4b outcompetes NF-κB for KPNA4 binding and translocation into the nucleus as a mechanism of interference with the NF-κB-mediated innate immune response.

Allogeneic hemopoietic stem cell transplantation for childhood acute lymphoblastic leukemia in second complete remission-similar outcomes after matched related and unrelated donor transplant: a study of the Spanish Working Party for Blood and Marrow Transplantation in Children (Getmon)

The authors report the results of 58 children with ALL in 2CR after related (n = 31) or unrelated (n = 27) AHSCT. Characteristics at diagnosis and initial and after relapse antileukemic treatment were similar in the related donor (RD) and the unrelated donor (UD) groups. Conditioning consisted of TBI/CY +/- VP-16 for patients > or = 3 years old (n = 43) and Bu/CY for the rest. Median recipient age was 8 years (range 1-17) in the RD and 9 years (range 3-14) in the UD group. Median follow-up was 54 months (range 24-80) and 52 months (range 22-85) in the RD and the UD groups repectively. The 5-year EFS probability was 43 +/- 9% for the RD group and 36 +/- 9% in the UD group (p = .25). The transplant-related mortality was 16% in the RD and 37% in the UD group (p = .016). In the RD group 36.7% of patients relapsed versus 18.6% in the UD group (p = .05). GvHD associated with organ failure or infection caused most of the transplant-related deaths in both groups. Survivor quality of life for both groups was good (Lansky score < or = 90).

Long-term outcome of allogeneic or autologous haemopoietic cell transplantation for acute lymphoblastic leukaemia in second remission in children. GETMON experience 1983–1998

We present a retrospective study of long-term outcome and predictive factors of survival and relapse in 219 paediatric patients with acute lymphoblastic leukaemia (ALL) in second remission. They received allogeneic (allo) or autologous (auto) haemopoietic cell transplantation (HCT) depending on the availability of a matched sibling donor. The probability of event-free survival (EFS) for the total patient group was 0.35+0.03 at 14 years. No significant differences were observed for EFS between allo- and auto-HCT: 0.39+0.05 vs 0.32+0.04 (P=0.43). A better EFS was seen in patients with a late relapse (LR) (P=0.06 and 0.02, for allogeneic and autologous respectively). Significantly better EFS was observed in allo-HCT patients under 10 years of age and in auto-HCT patients with leukocytes at diagnosis below 25 x 109/l and late relapse. Predictive factors of failure in both groups were early relapse (ER), medullary relapse and age over 10 years. The probability of relapse (RP) for the total group of patients was 0.57+0.03, and it was significantly higher in auto-HCT patients: 0.65+0.04 vs 0.42+0.06 (P=0.002). Factors predictive for relapse were medullary and early relapse, auto-HCT and WBC >25 x 109/l at diagnosis.

Factors regulating megakaryocyte progenitor commitment to polyploidization

Recognizable megakaryocytes are polyploid cells generated by a clonogenic, diploid progenitor, termed CFU-MKC (colony forming unit, megakaryocyte). In order to quantify polyploidization, ploidy histograms of megakaryocytes determined by microphotometric or flow cytometric measurements of megakaryocyte DNA have generally been used. However these techniques provide no information on the rate of commitment of CFU-MKC to polyploidy. Using a technique of clonal analysis determining the distributions of the number of doublings (NbD) undergone by CFU-MKC before committing to polyploidization, the polyploidization probability of CFU-MKC could be derived. This probability was found to be a constant independent from CFU-MKC mitotic history, since NbD distributions are exponential functions characterized by a constant rate of decay per doubling. By studying the effects of growth factors on polyploidization probability, it was also shown that: (1) this parameter is negatively regulated by growth factors contained in poke-weed or WEHI conditioned media, as well as by erythropoietin; (2) commitment to polyploidization does not require prior CFU-MKC division; (3) bipotent erythroid-megakaryocyte progenitors have a lower polyploidization probability than CFU-MKC; (4) determination of polyploidization probability reflects the activity of growth factors with greater accuracy than megakaryocyte colony count.

Factors regulating megakaryocyte progenitor commitment to polyploidization

Recognizable megakaryocytes are polyploid cells generated by a clonogenic, diploid progenitor, termed CFU-MKC (colony forming unit, megakaryocyte). In order to quantify polyploidization, ploidy histograms of megakaryocytes determined by microphotometric or flow cytometric measurements of megakaryocyte DNA have generally been used. However these techniques provide no information on the rate of commitment of CFU-MKC to polyploidy. Using a technique of clonal analysis determining the distributions of the number of doublings (NbD) undergone by CFU-MKC before committing to polyploidization, the polyploidization probability of CFU-MKC could be derived. This probability was found to be a constant independent from CFU-MKC mitotic history, since NbD distributions are exponential functions characterized by a constant rate of decay per doubling. By studying the effects of growth factors on polyploidization probability, it was also shown that: (1) this parameter is negatively regulated by growth factors contained in poke-weed or WEHI conditioned media, as well as by erythropoietin; (2) commitment to polyploidization does not require prior CFU-MKC division; (3) bipotent erythroid-megakaryocyte progenitors have a lower polyploidization probability than CFU-MKC; (4) determination of polyploidization probability reflects the activity of growth factors with greater accuracy than megakaryocyte colony count.

Anaemia during pregnancy as a risk factor for infant iron deficiency: report from the Valencia Infant Anaemia Cohort (VIAC) study

A prospective cohort study with a 1-year follow-up of 156 neonates was carried out specifically designed to test the hypothesis that there is a positive relationship between iron deficiency during pregnancy and the development of the same disease in newborn infants. Exposure was defined as being born of a mother with ferropenic anaemia at delivery, and cases as the infants who developed iron deficiency during their first year of life. A statistically significant positive association was detected with an odds ratio of 6.57 (95% confidence limits 1.81-25.97). A stratified analysis was also performed to control the effect of potential confounders such as socio-economic variables, feeding practices and other factors linked with the iron status of infants. This second analytical procedure showed no alteration in the association detected in the simple analysis but that there was a statistically significant strong interaction between the quantity of cow's milk intake and the ferropenic status of the mother. These results show a relationship between iron deficiency of the mother at delivery and the development of iron deficiency in the infants. These new findings could be important in the development of new prevention programmes applied to pregnant women.

Abnormal splenic megakaryopoiesis in MPSV-induced myeloproliferative disease

The myeloproliferative sarcoma virus (MPSV) induces a murine myeloproliferative syndrome characterized by an erythromyelemia, an anemia, a thrombocytopenia associated with a myeloproliferation in the spleen and a splenic and medullar fibrosis. We have used the in-vitro plasma clot technique to measure megakaryocytic precursors in the spleen and bone-marrow of MPSV-infected mice. We report that megakaryocytic colonies are increased, in number (X75), in concentration (X9) and in size, in the spleen but not in the bone-marrow of neoplastic mice. Furthermore, these splenic precursors are hypersensitive to growth factors present in the anemic mouse serum used in the culture system. These data show that the thrombocytopenia observed in the MPSV-induced neoplasia does not result from a lack of megakaryocyte precursors, but rather from an excess of megakaryocyte destruction. This ineffective splenic megakaryopoiesis associated with the presence of a massive splenic fibrosis make the MPS-induced neoplasia a suitable model for studying the perturbation of megakaryopoiesis in myeloproliferative syndrome associated with fibrosis.

Organization of haematopoietic stem cells and their relationship to mastocytopoiesis

Haematopoiesis is a dynamic process in which differentiated blood cells are regularly replaced by the proliferation and differentiation of stem cells. Two types of haematopoietic stem cells (HSC) can be distinguished: totiopotent HSC capable of giving rise to cells of all haematopoietic lineages, and pluripotent HSC capable of giving rise only to the myeloid lineages. HSC are characterized by their capacity for self-renewal and differentiation in committed stem cells determined towards one of the haematopoietic lineages. These committed stem cells, also named progenitor cells or colony-forming units (CFU), have the capacity to give rise, in semi-solid medium, to colonies composed of differentiated cells. It has recently been shown that mast cells originate from a pluripotent HSC and that CFU Baso/Masto can be detected from murine and human bone marrow and blood cells. The in vivo regulation of the proliferation and differentiation of HSC is not well known. Several studies have emphasized the role of the haematopoietic microenvironment and of long- and short-range factors in such regulation. The in vitro growth of HSC is strictly dependent on growth factors, also named CSF (colony-stimulating factors) and interleukin (IL), in particular IL3. IL3 is a glycoprotein which induces the proliferation and differentiation of pluripotent and committed HSC and which seems to have a preferential role in mast cell regulation.