SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion

Abstract: The B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha)1. In vitro, B.1.617.2 is sixfold less sensitive to serum neutralizing antibodies from recovered individuals, and eightfold less sensitive to vaccine-elicited antibodies, compared with wild-type Wuhan-1 bearing D614G. Serum neutralizing titres against B.1.617.2 were lower in ChAdOx1 vaccinees than in BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies to the receptor-binding domain and the amino-terminal domain. B.1.617.2 demonstrated higher replication efficiency than B.1.1.7 in both airway organoid and human airway epithelial systems, associated with B.1.617.2 spike being in a predominantly cleaved state compared with B.1.1.7 spike. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralizing antibody, compared with that of wild-type spike. We also observed that B.1.617.2 had higher replication and spike-mediated entry than B.1.617.1, potentially explaining the B.1.617.2 dominance. In an analysis of more than 130 SARS-CoV-2-infected health care workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune-evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era

Spontaneous fracture of the femoral neck in preexisting avascular necrosis of femoral head in sickle cell disease

【Abstract】 Avascular necrosis of the femoral head is a known complication of femoral neck fracture but on the contrary, femoral neck fracture in a case of preexisting avas-cular necrosis is a very rare phenomenon. We present a case study of a 47 year old Iraqi male who developed spon-taneous ipsilateral subcapital femoral neck fracture under the condition of preexisting sickle cell disease and avascu-lar necrosis of the femoral head. The fracture was unnoticed for a few months. The patient was managed successfully by uncemented total hip arthroplasty. Postoperative recovery was uneventful and he was discharged 4 days after surgery. At 1 year’s follow-up, the patient had normal gait and hip function, with no sign of loosening or any other complica-tions on radiograph. Key words: Femur head necrosis; Femoral neck fractures; Anemia, sickle cel