Dominant-negative effect of hetero-oligomerization on the function of the human immunodeficiency virus type 1 envelope glycoprotein complex

The human immunodeficiency virus type 1 (HIV-1) envelope (Env) glycoprotein forms trimers that mediate interactions with the CD4 receptor and a co-receptor on the target cell surface, thereby triggering viral fusion with the cell membrane. Cleavage of Env into its surface, gp120, and transmembrane, gp41, moieties is necessary for activation of its fusogenicity. Here, we produced pseudoviruses with phenotypically mixed wild-type (Wt) and mutant, cleavage-incompetent Env in order to quantify the effects of incorporating uncleaved Env on virion infectivity, antigenicity and neutralization sensitivity. We modeled the relative infectivity of three such phenotypically mixed viral strains, JR-FL, HXBc2 and a derivative of the latter, 3.2P, as a function of the relative amount of Wt Env. The data were fit very closely (R(2) > 0.99) by models which assumed that only Wt homotrimers were functional, with different approximate thresholds of critical numbers of functional trimers per virion for the three strains. We also produced 3.2P pseudoviruses containing both a cleavage-competent Env that is defective for binding the neutralizing monoclonal antibody (NAb) 2G12, and a cleavage-incompetent Env that binds 2G12. The 2G12 NAb was not able to reduce the infectivity of these pseudoviruses detectably. Their neutralization by the CD4-binding site-directed agents CD4-IgG2 and NAb b12 was also unaffected by 2G12 binding to uncleaved Env. These results further strengthen the conclusion that only homotrimers consisting of cleaved Env are functional. They also imply that the function of a trimer is unaffected sterically by the binding of an antibody to an adjacent trimer.     

Characteristics of hepatitis B viral strains in chronic carrier patients from North-East Algeria

Objective

The goal of the study was to determine the characteristics of chronic hepatitis B virus (HBV) infections in the north-east part of Algeria. Chronic HBV infection remains a global public health issue and Algeria is considered as an intermediate prevalence area. Improving our knowledge on the epidemiology of this infection is a prerequisite to adopt the best preventive and curative strategy.

Material and methods

We have studied 75 chronic hepatitis B patients from north-east Algeria. The characteristics of HBV strains were determined by use of serological and molecular testing. Genes encoding part of the precore, the surface and the polymerase were sequenced and phylogenetically analyzed.

Results

Median age of the patients was 35 years and 80% of them had normal transaminase level. Liver histological lesions were identified in 63% of the patients who benefited from a liver biopsy and 21% of them had cirrhosis. Median viral replication was 3.9 Log IU/ml and 87% of patients had a “precore” mutant serological profile without HBe Ag. Genotype D was predominant (93%) followed by genotype A (5%) and E for one patient. Algerian strains clustered independently from other genotype D reference sequences, suggesting a possible new D subtype. Within the “precore” region, only 16% of the strains did not show any mutation at positions 1762/1764 and 1896.

Conclusion

In this original set of patients from north Algeria, the virologic characteristics of HBV are comparable to what has been described in other Mediterranean countries. Our study raises several important aspects with regard to the prevention and treatment of chronic hepatitis B in Algeria.     

高海拔地区急慢性牙髓炎变形链球菌检出率分析

目的探讨急慢性牙髓炎与变形链球菌的感染及其临床意义。方法获取（海拔2260m）86份急性与64份慢性牙髓炎髓腔内容物标本接种于TM培养基,厌氧箱培养72h后分离可疑菌落,经耐氧实验确定厌氧菌,并做生化反应鉴定菌种。分析变形链球菌在急慢性牙髓炎中的感染率,经卡方检验观察有无差异性。结果变形链球菌在急慢性牙髓炎中的分离率分别为67．4％和29．7％,具有统计学意义（P〈0．01）。结论变形链球菌在高原地区是引起急性牙髓炎的重要病原菌,慢性时为次要病原菌,两者其病因菌存在着变迁。     

Sterile mutants of Schizosaccharomyces pombe: Analysis by somatic hybridization

Summary Sixteen sterile mutants of Schizosaccharomyces pombe, isolated from homothallic h ⁹⁰strains, were examined. It was found that they are blocked either in copulation and meiosis or in copulation alone.Protoplasts of the sterile strains were fused with protoplasts of h^+N, h^–S or h ⁹⁰strains. In these somatic crosses, eight of the sterile strains yielded hybrids which were able to form azygotic asci. Tetrad analyses revealed that seven of these sterile strains contain a single mutation; the mutations represent at least five sterility genes (ste2, ste3, ste4, ste5, ste6). One sterile strain contains two unlinked mutations which do not represent sterility genes, but genes the interaction of which results in a sterile phenotype.     

Control of motor axon guidance in the zebrafish embryo

The zebrafish neuromuscular system has been an exemplary model for studying motor axon guidance since its detailed characterization almost two decades ago. In particular, characterization and detailed analysis has focused on the development and axogenesis of early developing primary motoneurons. During the first day of development, neuromuscular connections are limited to three primary motoneurons per spinal cord hemisegment innervating three discreet myotome territories. Observations of dye labeled primary motor axons in living embryos revealed that axogenesis is highly stereotyped with each primary motor axon extending along specific pathways and displaying particular characteristics. Exploiting the unique attributes of zebrafish, notably the ability to analyze motoneurons in living embryos and the capability to induce mutations, has allowed a comprehensive cellular, molecular and genetic approach to discerning the mechanisms that control the formation of neuromuscular connectivity. Knowledge gained from this body of work not only relates to zebrafish, but to vertebrate axon guidance in general.     

Effects of glycosylation on antigenicity and immunogenicity of classical swine fever virus envelope proteins

Classical swine fever virus (CSFV) harbors three envelope glycoproteins (E^rns, E1 and E2). Previous studies have demonstrated that removal of specific glycosylation sites within these proteins yielded attenuated and immunogenic CSFV mutants. Here we analyzed the effects of lack of glycosylation of baculovirus-expressed E^rns, E1, and E2 proteins on immunogenicity. Interestingly, E^rns, E1, and E2 proteins lacking proper post-translational modifications, most noticeable lack of glycosylation, failed to induce a detectable virus neutralizing antibody (NA) response and protection against CSFV. Similarly, no NA or protection was observed in pigs immunized with E1 glycoprotein. Analysis of E^rns and E2 proteins with single site glycosylation mutations revealed that detectable antibody responses, but not protection against lethal CSFV challenge is affected by removal of specific glycosylation sites. In addition, it was observed that single administration of purified E^rns glycoprotein induced an effective protection against CSFV infection.     

Characterization of susceptibility variants of poliovirus grown in the presence of favipiravir

Background

T-705 (favipiravir) is a potent inhibitor of RNA-dependent RNA polymerases of influenza viruses and no favipiravir-resistant virus has been isolated. Poliovirus RNA polymerase has been well characterized and isolation of resistant virus was examined in poliovirus.

3,3′-Diindolylmethane (DIM) inhibits the growth and invasion of drug-resistant human cancer cells expressing EGFR mutants

Epidermal Growth Factor Receptor (EGFR) mutants are associated with resistance to chemotherapy, radiation, and targeted therapies. Here we found that the phytochemical 3,3′-Diindolylmethane (DIM) can inhibit the growth and also the invasion of breast cancer, glioma, and non-small cell lung cancer cells regardless of which EGFR mutant is expressed and the drug-resistant phenotype. DIM reduced an array of growth factor signaling pathways and altered cell cycle regulators and apoptotic proteins favoring cell cycle arrest and apoptosis. Therefore, DIM may be used in treatment regimens to inhibit cancer cell growth and invasion, and potentially overcome EGFR mutant-associated drug resistance.