Feline coronavirus (FCoV) consists of two biotypes based on their growth in cell culture and their antigenicity. Infections with FCoV are highly prevalent in the cat population worldwide. In this study, Felis catus whole fetus (Fcwf-4)cell culture was infected with FCoV UPM11C/08. Virus multiplication in cell culture was monitored and examined under the transmission electron microscope. The virus particles revealed the characteristic morphology of feline FCoV represented by envelope viruses surrounded by peplomers. Virus attachment and entry into the cell occurred 15 h post-infection (pi), and the myriad of virus particles were observed both extracellularly and intracellularly after 48 h pi. Thereafter, intracellular virus particles were observed to be present in vacuoles or present freely in the cytoplasm.
The expression of the multidrug resistance (MDR) proteins may influence the outcome of treatment in patients with acute leukemia. The aim of this study was to determine the IC50 of cytotoxic drugs (cytosine arabinoside, ara-C and daunorubicin, dnr) using the in vitro 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)2H-tetrazolium, inner salt (MTS) assay method. A total of 82 newly diagnosed acute leukemia cases (43 adult myeloid leukaemia, AML cases and 39 acute lymphoblastic leukaemia, ALL cases) and 16 relapsed cases (8 AML cases and 8 ALL cases) were studied. The MTS assay was performed using two cytotoxic drugs, dnr and ara-C. Cells were incubated with different concentrations of drugs for 4 days and the IC50 was extrapolated from the viability curve. In newly diagnosed cases, we found that childhood ALL samples showed higher IC50 values of dnr (0.040 +/- 2.320) compared to adult AML samples (0.021 +/- 0.158). In contrast, newly diagnosed adult AML samples showed higher IC50 values of ara-C (0.157 +/- 0.529) compared to childhood ALL samples (0.100 +/- 2.350). In relapsed cases, two samples of childhood ALL showed IC50 values of dnr (0.910 +/- 1.760) and ara-C (1.310 +/- 2.390), which was higher compared to childhood AML samples (0.129 +/- 0.214 and 0.210 +/- 0.003, respectively). However, there was no correlation between IC50 values of these drugs tested with clinical outcome. In conclusion, we found that MTS assay is an easy, rapid and non laborious method to study in vitro drug resistance in acute leukaemia cases.