Kinetic Study of Yellow Fever 17DD Viral Infection in Gallus gallus domesticus Embryos

Abstract

Yellow fever continues to be an important epidemiological problem in Africa and South America even though the disease can be controlled by vaccination. The vaccine has been produced since 1937 and is based on YFV 17DD chicken embryo infection. However, little is known about the histopathological background of virus infection and replication in this model. Here we show by morphological and molecular methods (brightfield and confocal microscopies, immunofluorescence, nested-PCR and sequencing) the kinetics of YFV 17DD infection in chicken embryos with 9 days of development, encompassing 24 to 96 hours post infection. Our principal findings indicate that the main cells involved in virus production are myoblasts with a mesenchymal shape, which also are the first cells to express virus proteins in Gallus gallus embryos at 48 hours after infection. At 72 hours post infection, we observed an increase of infected cells in embryos. Many sites are thus affected in the infection sequence, especially the skeletal muscle. We were also able to confirm an increase of nervous system infection at 96 hours post infection. Our data contribute to the comprehension of the pathogenesis of YF 17DD virus infection in Gallus gallus embryos.

Generation of Yellow Fever virus vaccine in skeletal muscle cells of chicken embryos

“…This model reproduces in vivo chicken infection, in which muscle fibres and myogenic progenitors are infected, thus corroborating previous data demonstrated by our group 7 8 In these previous studies, staining of viral proteins in perinuclear clusters was observed; after muscle fibre striations, a pattern was also observed here. Manso et al 8 discuss that the first cells to appear infected showed morphology suggestive of myoblasts.…”

“…Although chicken embryos have been used since 1937 as biological systems for the production of YFV, 2 tissues and cell targets responsible for the biosynthesis of viral particles have only been described very recently 7 . Moreover, skeletal muscle is the main tissue infected in chicken embryos, suggesting that muscle cells are a major site for production of viral particles after infection 8 …”

Kidney involvement in yellow fever: a review

“…Currently, specific antiviral treatment is not available for yellow fever (YF). Prevention and vaccination are the key control-factors in high-risk areas 18 . These areas are composed mainly of tropical forests in which the sylvatic cycle was first described in the 1930s and early 1940s 19 , 20 .…”

“…Yellow fever sporadically disappears during the winter period 18 . According to the Brazilian Ministry of Health and the WHO 32 , 33 , yellow fever is a seasonal disease that mostly occurs during the summer, with December and January being the hottest months in the Southern Hemisphere, when there is a higher number of confirmed cases, as shown in Figure 1 .…”

“…The 17D strain was first used in Brazil in 1937 for vaccination purposes, and since then The Oswald Cruz Foundation has produced the yellow fever 17DD (YF-17D) vaccine. To produce the 17DD vaccine, a sample of the yellow fever virus is inoculated into pathogens-free embryonated chicken eggs, as recommended by the WHO 14 , 18 .…”