Growth promoting activity of Pangasianodon hypophthalmus recombinant growth hormone expressed in Escherichia coli

Recombinant growth hormone of Pangasianodon hypophthalmus (rPhGH) was efficiently expressed in Escherichia coli BL 21 (DE3) cells. The expression vector pET-32a(+) was used to clone and express a 550 bp long cDNA fragment, which encodes the mature region of growth hormone. The rPhGH was expressed as a 6X HIS-tag fusion protein in E. coli upon induction by Isopropyl b-D-thiogalactoside, and formed insoluble inclusion bodies in the host cells. SDS-PAGE analysis indicated that the molecular weight of the fusion protein was about 23 kDa, which is comparable to the theoretical value of the mature growth hormone of the fish. The expressed protein was recovered by solubilising the inclusion bodies under denaturing conditions with urea and then the denatured proteins were refolded and purified on Ni-NTA column. The purified recombinant protein was confirmed by Western blot analysis using anti-His antibodies. Total yield of the refolded and purified protein was 20 mg l-1 of LB medium. Biological activity of the purified recombinant protein was determined in in vivo bioassay by its ability to promote growth in rohu (Labeo rohita) fingerlings, injected with three different concentrations of the hormone. A significant increase in growth was observed in rohu fingerlings administered with rPhGH at a dosage of 1.0 mg g body weight -1

Determinants of SARS-CoV-2 entry and replication in airway mucosal tissue and susceptibility in smokers.

Understanding viral tropism is an essential step toward reducing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission, decreasing mortality from coronavirus disease 2019 (COVID-19) and limiting opportunities for mutant strains to arise. Currently, little is known about the extent to which distinct tissue sites in the human head and neck region and proximal respiratory tract selectively permit SARS-CoV-2 infection and replication. In this translational study, we discover key variabilities in expression of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), essential SARS-CoV-2 entry factors, among the mucosal tissues of the human proximal airways. We show that SARS-CoV-2 infection is present in all examined head and neck tissues, with a notable tropism for the nasal cavity and tracheal mucosa. Finally, we uncover an association between smoking and higher SARS-CoV-2 viral infection in the human proximal airway, which may explain the increased susceptibility of smokers to developing severe COVID-19. This is at least partially explained by differences in interferon (IFN)-β1 levels between smokers and non-smokers

Determinants of SARS-CoV-2 entry and replication in airway mucosal tissue and susceptibility in smokers.

Understanding viral tropism is an essential step towards reducing SARS-CoV-2 transmission, decreasing mortality from COVID-19, and limiting opportunities for mutant strains to arise. Currently, little is known about the extent to which distinct tissue sites in the human head & neck region and proximal respiratory tract selectively permit SARS-CoV-2 infection and replication. In this translational study, we discover key variabilities in the expression of ACE2 and TMPRSS2, essential SARS-CoV-2 entry factors, among the mucosal tissues of the human proximal airways. We show that SARS-CoV-2 infection is present in all examined head & neck tissues, with a notable tropism for the nasal cavity and tracheal mucosa. Finally, we uncover an association between smoking and higher SARS-CoV-2 viral infection in the human proximal airway, which may explain the increased susceptibility of smokers to developing severe COVID-19. This is at least partially explained by differences in IFN-β1 levels between smokers and non-smokers