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This st udy aims to evaluate the prevalence of SARS-CoV-2 antibodies in locked-down family households to determine viral dynamics and immunity acquisition. COVID-19 individuals and their households in lockdown under the same roof during early spring 2020 were interviewed and tested using rapid immunochromatographic lateral flow antibodies assays (LFA) between July and September 2020. Outcomes were secondary infection rate (SIR) among contacts, household infection rate, and predictors of transmission. We enrolled 87 households including 87 COVID-19 index cases (female 78.2%; median age: 47.0 years, IQR: 42.0–51.5) and 255 contacts (males: 52.9%; median age: 19.0 years, IQR: 11.0–43.5) consisting of their children (42%) or spouses/partners (28.2%). A total of 95/255 contacts were SARS-CoV-2 antibody positive leading to a SIR of 37.3% (95% confidence interval (CI): 31.3–43.5%). Viral transmission was observed in 54 households (62%). SARS-CoV-2 infection was asymptomatic in 33/95 (34.7%) of SARS-CoV-2-positive contacts. Independent predictors of virus transmission from index to contacts were housing surface area < 60 m2 (OR: 5.6 [1.1; 28.2] and a four-member family compared to five (OR: 3.6 [1.2; 10.3]). Households represent a high-risk setting for SARS-CoV-2 transmission through close contact within the family amplified by the number of family members and the housing surface area. [ABSTRACT FROM AUTHOR]

Dengue disease is caused by four different flavivirus serotypes, which infect 390 million people yearly with 25% symptomatic cases and for which no licensed vaccine is available. Recent phase III vaccine trials showed partial protection, and in particular no protection for dengue virus serotype 2 (refs 3, 4). Structural studies so far have characterized only epitopes recognized by serotype-specific human antibodies. We recently isolated human antibodies potently neutralizing all four dengue virus serotypes. Here we describe the X-ray structures of four of these broadly neutralizing antibodies in complex with the envelope glycoprotein E from dengue virus serotype 2, revealing that the recognition determinants are at a serotype-invariant site at the E-dimer interface, including the exposed main chain of the E fusion loop and the two conserved glycan chains. This 'E-dimer-dependent epitope' is also the binding site for the viral glycoprotein prM during virus maturation in the secretory pathway of the infected cell, explaining its conservation across serotypes and highlighting an Achilles' heel of the virus with respect to antibody neutralization. These findings will be instrumental for devising novel immunogens to protect simultaneously against all four serotypes of dengue virus. [ABSTRACT FROM AUTHOR]

Chikungunya virus (CHIKV) is an emerging mosquito-borne alphavirus that has caused widespread outbreaks of debilitating human disease in the past five years. CHIKV invasion of susceptible cells is mediated by two viral glycoproteins, E1 and E2, which carry the main antigenic determinants and form an icosahedral shell at the virion surface. Glycoprotein E2, derived from furin cleavage of the p62 precursor into E3 and E2, is responsible for receptor binding, and E1 for membrane fusion. In the context of a concerted multidisciplinary effort to understand the biology of CHIKV, here we report the crystal structures of the precursor p62-E1 heterodimer and of the mature E3-E2-E1 glycoprotein complexes. The resulting atomic models allow the synthesis of a wealth of genetic, biochemical, immunological and electron microscopy data accumulated over the years on alphaviruses in general. This combination yields a detailed picture of the functional architecture of the 25 MDa alphavirus surface glycoprotein shell. Together with the accompanying report on the structure of the Sindbis virus E2-E1 heterodimer at acidic pH (ref. 3), this work also provides new insight into the acid-triggered conformational change on the virus particle and its inbuilt inhibition mechanism in the immature complex. [ABSTRACT FROM AUTHOR]