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Avian Reovirus | 183

(A)

(B)

Figure 6.3 Characteristic cytopathic effect (CPE) induced by avian orthoreovirus. (A) QM5 cell line uninfected control (left) and QM5 cell
line 2 days post infection with American crow reovirus isolate (right). (B) Vero cell line uninfected control (left) and Vero cell line 6 days post
infection with American crow reovirus isolate (right). Note the multinucleated giant cells (syncytia) and in B, right, detachment and floating
debris in medium. The scale bar represents 100 µm. (Kalupahana 2017).

in many cell cultures. In chicken embryo cell cultures, CPE was growth rate, special growth requirements, inability to subculture
first detected on the ninth, seventh and fourth passage of avian (Barta et al., 1984), tedious and time-consuming preparation
orthoreovirus strains Type 24, Type 25 and Type 59, respectively (Nwajei et al., 1988) make them less desirable than continuous
(Deshmukh and Pomeroy, 1969). The CPE of these viruses cell lines.
appeared at 5–7 days PI, and syncytia became numerous and
larger upon further incubation, until the entire monolayer was
destroyed by day 9 PI, however, the maximum virus titre was less Continuous cell lines
2
than 10 plaque forming units per millilitre (PFU/ml). Strain R1 Several mammalian cell lines have been used to propagate avian
of avian orthoreovirus, when prepared in CELu, CEK and CELi reoviruses, including those of bovine origin Madin Darby bovine
cell cultures produced titres of 6.2, 6.2 and 7.0 log10 TCID , kidney (MDBK), and Georgia bovine kidney (GBK), canine
50
respectively, by the third passage, which increased to 8.2, 7.2 and origin Madin Darby canine kidney (MDCK), murine origin
8.4 log10 TCID , respectively, by the 25th passage, while the L929, human origin Chang C, Hep-2, HeLa, primate origin
50
virus propagated in CEF only produced a maximum titre of 6.0 LLC-MK2, African green monkey kidney (VERO), feline origin
log10 TCID /ml (Guneratne et al., 1982). In addition to the Crandell feline kidney (CrFK), baby hamster kidney (BHK),
50
higher titre of virus, CELi cultures also produced larger plaques rabbit kidney (RK), and porcine kidney (PK) (Sahu and Olson,
than CEK cultures. More blind passages (5–7) were required 1975; Barta et al., 1984). In addition, avian orthoreoviruses were
before CPE was observed in virus isolation attempts using CL, grown in avian origin continuous cell lines, such as three cell lines
CK, and CTCC with avian orthoreovirus strains Type 24, Type established from a chemically induced fibrosarcoma of Japanese
25, Type 59, FC, WVU 1464–29H, WVU 2937, WVU 2986, and quail (Coturnix coturnix japonica) (Moscovici et al., 1977) QT35
WVU 71–212 (Guneratne et al., 1982). (Cowen and Braune, 1988), QT6 (Duncan et al., 1996), QM5,
Avian orthoreoviruses have a predilection for primary cultures a clonal derivative of QT6 (Duncan and Sullivan, 1998), and
of chicken cells (Guneratne et al., 1982). Therefore, primary chicken macrophage derived HD11 cell line (Swanson et al.,
chicken or chicken embryo origin cells have been considered the 2001).
most suitable cell culture for isolation and propagation of avian Data in literature on adaptation of avian reovirus to heter-
orthoreoviruses (Mustaffa-Babjee et al., 1973). However, slow ologous cell systems are inconsistent (Georgieva and Jordanova,