T. C. Ayi

Evidence for the interaction of the human metapneumovirus G and F proteins during virus-like particle formation

BackgroundHuman metapneumovirus (HMPV) is now a major cause of lower respiratory infection in children. Although primary isolation of HMPV has been achieved in several different cell lines, the low level of virus replication and the subsequent recovery of low levels of infectious HMPV have hampered biochemical studies on the virus. These experimental methodologies usually require higher levels of biological material that can be achieved following HMPV infection. In this study we demonstrate that expression of the HMPV F, G and M proteins in mammalian cells leads to HMPV virus-like particles (VLP) formation. This experimental strategy will serve as a model system to allow the process of HMPV virus assembly to be examined.MethodsThe HMPV F, G and M proteins were expressed in mammalian cell lines. Protein cross-linking studies, sucrose gradient centrifugation and in situ imaging was used to examine interactions between the virus proteins. VLP formation was examined using sucrose density gradient centrifugation and electron microscopy analysis.ResultsAnalysis of cells co-expressing the F, G and M proteins demonstrated that these proteins interacted. Furthermore, in cells co-expression the three HMPV proteins the formation VLPs was observed. Image analysis revealed the VLPs had a similar morphology to the filamentous virus morphology that we observed on HMPV-infected cells. The capacity of each protein to initiate VLP formation was examined using a VLP formation assay. Individual expression of each virus protein showed that the G protein was able to form VLPs in the absence of the other virus proteins. Furthermore, co-expression of the G protein with either the M or F proteins facilitated their incorporation into the VLP fraction.ConclusionCo-expression of the F, G and M proteins leads to the formation of VLPs, and that incorporation of the F and M proteins into VLPs is facilitated by their interaction with the G protein. Our data suggests that the G protein plays a central role in VLP formation, and further suggests that the G protein may also play a role in the recruitment of the F and M proteins to sites of virus particle formation during HMPV infection.

Protozoon classifications based on size, shape and refractive index using on-chip immersion refractometer

This paper presents an on-chip immersion refractometer for the measurement of size, shape and refractive index of protozoa in treated water. The key features of the on-chip immersion refractometer include (1) multiple single cyst trapping sites, which enable the measurement of multiple sample per test; and (2) zig-zag micromixer, which enables the refractive index variation of external medium as the key component of immersion refractometry. The results show that C. parvum oocysts have size of 3 to 7 µm, spherical with ovality lower than 0.3, and refractive index of 1.418. G. lamblia cysts have size of 8 to 12 µm, oval with ovality higher than 0.3, and refractive index of 1.433. The refractive indices of the samples are measured with high precision of < 10−3.

Optofluidic detection for virus infection monitoring using effective refractive index

This paper presents an optofluidic imaging system to detect influenza virus infection via the change of refractive index based on scattering signature. This method allows for a direct monitor of the influenza flu virus.