This review aims to summarize current data describing the characteristics of bovine coronavirus (BCV) and the three clinical syndromes with which this virus is associated. The first half of this paper consists of a general description of the virus, commencing with a brief outline of the methods used for in vitro growth. The structure of the virus is then described in more detail, with particular reference to the structure and functions of the four major viral proteins. This is followed by an outline of the unique replication strategy adopted by coronaviruses. The second half of this review discusses the clinical significance of the virus, beginning with a detailed account of BCV-induced neonatal calf diarrhoea, the clinical syndrome with which this virus is most commonly associated. The clinical and epidemiological importance of BCV respiratory tract infection is then discussed, and finally the evidence supporting the aetiological role of BCV in outbreaks of winter dysentery in adult cattle is examined.

We have developed a sensitive and quantitative reverse-transcription polymerase chain reaction (RT-PCR) assay for detection of PML-RARalpha, the fusion oncogene present as a specific marker in >99% of cases of acute promyelocytic leukemia (APL). The assay is linear over at least 5 orders of magnitude of input DNA or RNA, and detects as few as 4 copies of PML-RARalpha plasmid DNA. PML-RARalpha transcripts could be detected in mixtures containing 2 to 5 pg of RNA from fusion-containing cells in a background of 1 microg of RNA from PML-RARalpha-negative cells. Using 1.0 to 2.5 microg of input RNA, the sensitivity of the assay was between 10(-5) and 10(-6). Furthermore, determination of GAPDH copy number in each reaction allowed an accurate assessment of sample-to-sample variation in RNA quality and reaction efficiency, with consequent definition of a detection limit for each sample assayed. Using an internal calibrator, assay precision was high, with coefficients of variation between 10 and 20%. An interlaboratory study using coded samples demonstrated excellent reproducibility and high concordance between laboratories. This assay will be used to test the hypothesis that sensitive and quantitative measurement of leukemic burden, during or after therapy of APL, can stratify patients into discrete risk groups, and thereby serve as a basis for risk-adapted therapy in APL.

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A relatively simple and sensitive method is described which enables the effect of monoclonal antibodies (MAbs) on the receptor-destroying enzyme (RDE) and the haemagglutination (HA) activity of bovine coronavirus (BCV) to be analysed in one assay. A lysate of HRT-18 cells infected with the L9 strain of BCV was found to have a higher RDE:HA ratio than purified virus. At 4 °C the lysate induced an HA pattern which completely disappeared upon raising of the temperature to 37 °C. This L9-infected cell lysate was used to determine the HA inhibition (HAI) titres of MAbs directed against the surface glycoproteins S and HE of BCV. Thereafter, the test plates were incubated at 37 °C to enable the ability of the MAbs to prevent elution of virus from BCV-erythrocyte complexes to be assessed. No inhibition of RDE was detectable with MAbs against glycoprotein S, which had HA1 titres ranging from 1:16 to 1:128. On the other hand, MAbs directed against glycoprotein HE had similar HA1 titres, but they inhibited elution of 8 HA units of BCV at titres of up to 1: 65 000.Bovine coronavirus (BCV) is an enteropathogen which causes severe diarrhoea in neonatal calves (Mebus et al., 1973) and which is implicated aetiologically in winter dysentery of adult cattle (Saif et al., 1988). BCV represents one of the better characterized haemagglutinating coronaviruses. Four major structural proteins are associated with infectious BCV (King & Brian, 1982;St Cyr-Coats et al., 1988), two of which are a phosphorylated nucleocapsid protein of Mr 50K to 54K and the integral membrane protein M, consisting of a family of glycoproteins of 23K to 26K.King et al. (1985) identified a haemagglutinin with an approximate Mr of 62K in the reduced, and of 124K in the non-reduced form. This structural protein forms the short spikes of the viral envelope (Doughri et al., 1976). Acetylesterase (AE) activity is associated with this glycoprotein, which is referred to as haemagglutininesterase (HE) (Vlasak et al., 1988a; Cavanagh et al., 1990). The enzyme is able to inactivate cellular receptors for BCV by hydrolysing an ester bond to release acetate from C-9 of sialic acid. The gene encoding HE is located upstream of the S gene, and encodes a protein of 424 amino acids Kienzle et al., 1990).The S glycoprotein is the third envelope-associated protein and forms the longer surface projections characteristic of BCV (Doughri et al., 1976). The nucleotide sequence of the S gene of BCV encodes 1363 amino acids, with an N-terminal signal sequence and a transmembrane sequence near the C-terminal end. Cleavage of the S glycoprotein into proteins S1 and $2 is predicted to occur at an RRSRR or RRSVR sequence at positions 764 to 768 (Zhang et al., 1991;Parker et al., 1990;Boireau et al., 1990;Abraham et al., 1990). The N-terminal moiety is the S1 glycoprotein and that at the C terminus represents the $2 subunit (Spaan et al., 1988). Cleavage of the S protein precursor is required for cell fusion activity (Storz et al., 1981 ;Sturman et al., 1985). The functions of the S prot...

The humoral immune response to p53 was determined in 54 individuals with colon or breast cancer and 50 healthy subjects, in an attempt to better understand the origin and significance of anti-p53 serum antibodies. The presence of anti-p53 antibodies in serum was determined by enzyme-linked immunosorbent assay using purified recombinant human p53, and results were validated by immunoprecipitation of radiolabelled p53. Immunohistochemical analysis of 28 tumours was performed to detect the accumulation of p53 protein. Antibodies against p53 were significantly more common in patients with colorectal (10 of 42) and breast (2 of 12) cancer than in healthy individuals (2 of 50). They were of both the IgM (7 of 11) and IgG (4 of 11) isotypes. There was no significant difference in prevalence of serum antibodies against p53 with respect to the p53 immunohistochemical status of the tumour or to other pathological features, including the presence of lymph node and distant metastases. These findings provide indirect evidence that, rather than arising as a result of a specific immune response, anti-p53 antibodies in individuals with cancer may represent elevated levels of naturally occurring polyreactive antibodies.