Arboviruses cycle between, and replicate in, both invertebrate and vertebrate hosts, which for Zika virus (ZIKV) involves Aedes mosquitoes and primates1. The viral determinants required for replication in such obligate hosts are under strong purifying selection during natural virus evolution, making it challenging to resolve which determinants are optimal for viral fitness in each host. Herein we describe a deep mutational scanning (DMS) strategy2–5 whereby a viral cDNA library was constructed containing all codon substitutions in the C-terminal 204 amino acids of ZIKV envelope (E) protein. The cDNA library was transfected into C6/36 (Aedes) and Vero (primate) cells, with subsequent deep sequencing and computational analyses of recovered viruses showing that K316Q and S461G, or Q350L and T397S substitutions conferred substantial replicative advantages in mosquito and primate cells, respectively. A 316Q/461G virus was constructed and shown to be replication-defective in mammalian cells due to severely compromised virus particle formation and secretion. The 316Q/461G virus was also highly attenuated in human brain organoids, and illustrated utility as a vaccine in mice. This approach can thus imitate evolutionary selection in a matter of days and identify amino acids key to regulating virus replication in specific host environments.

The disassembly of apoptotic cells into small membrane-bound vesicles termed apoptotic bodies (ApoBDs) is a hallmark of apoptosis; however, the functional significance of this process is not well defined. We recently discovered a new membrane protrusion (termed beaded apoptopodia) generated by apoptotic monocytes which fragments to release an abundance of ApoBDs. To investigate the function of apoptotic monocyte disassembly, we used influenza A virus (IAV) infection as a proof-of-concept model, as IAV commonly infects monocytes in physiological settings. We show that ApoBDs generated from IAV-infected monocytes contained IAV mRNA, protein and virions and consequently, could facilitate viral propagation in vitro and in vivo, and induce a robust antiviral immune response. We also identified an antipsychotic, Haloperidol, as an unexpected inhibitor of monocyte cell disassembly which could impair ApoBD-mediated viral propagation under in vitro conditions. Together, this study reveals a previously unrecognised function of apoptotic monocyte disassembly in the pathogenesis of IAV infections.

Dengue is a major vector-borne infection causing large outbreaks in urban communities in tropical regions. During the period 2010- 2014; 434 serum samples from febrile patients were collected from a  semi-rural community hospital located in the norwestern region of Ecuador. Dengue virus (DENV) was investigated by reverse transcriptase PCR; a total of 48 samples were positive for dengue. During our study we detected  DENV-2 and DENV-3 from 2010 to 2013 and the four  DENV  serotypes during the period 2013-2014.  Surprisingly, our results contrasted with surveys carried out in urban centers throughout the  Ecuadorian Coast in which  DENV-1, DENV-2 and DENV-4 were prevalent during years 2010-2013 and only 2 serotypes  (DENV-1 and DENV-2) in 2014.These results suggest  that dengue viruses in semi-rural communities didn’t  originate in the Ecuadorian cities.

Background The uncontrollable spread of Zika virus (ZIKV) in the Americas during 2015–2017, and its causal link to microcephaly in newborns and Guillain-Barré syndrome in adults, led the World Health Organisation to declare it a global public health emergency. One of the most notable features of ZIKV pathogenesis was the ability of the virus to pass the placental barrier to infect the growing foetus. This pathogenic trait had not been observed previously for medically important flaviviruses, including dengue and yellow fever viruses. Methods In this study we evaluated the replication kinetics of ZIKV and the related encephalitic flavivirus West Nile strain Kunjin virus (WNVKUN) in early-term placental cell lines. Results We have observed that WNVKUN in fact replicates with a greater rate and to higher titres that ZIKV in these cell lines. Conclusions These results would indicate the potential for all flaviviruses to replicate in placental tissue but it is the ability to cross the placenta itself that is the restrictive factor in the clinical progression and presentation of congenital Zika syndrome.

Here, we present the complete genome sequences of two Zika virus (ZIKV) strains, EcEs062_16 and EcEs089_16, isolated from the sera of febrile patients in Esmeraldas City, in the northern coastal province of Esmeraldas, Ecuador, in April 2016. These are the first complete ZIKV genomes to be reported from Ecuador.

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