Chicken infectious anemia virus (CIAV) is a unique infectious agent with an amino acid composition that has been found to be remarkably conserved even in isolates from different parts of the world. We have characterized field isolates of CIAV which vary significantly in terms of their abilities to replicate in culture, demonstrating a biological difference between isolates. Two sublines of MDCC-MSB1 cells that differ in their abilities to support CIAV were identified. In the MSB1(S) subline the CIA-1 isolate of CIAV was found to be less cytopathogenic than the prototype Cux-1(C) isolate; the MSB1(L) subline, which supports Cux-1(C) replication, was found to be nonpermissive for CIA-1. Alignments of the VP1 sequences of previously examined isolates with those of the field isolates CIA-1 and L-028 and the culture-adapted ConnB isolate revealed a previously unreported hypervariable region spanning amino acid positions 139 to 151. Chimeras of Cux-1(C) and CIA-1 were constructed to examine the potential for this region to affect cytopathogenicity. Transfer of a 316-bp region of Cux-1(C) open reading frame 1 into CIA-1 produced a virus with a cytopathogenic profile typical of Cux-1(C), indicating that one or both of the amino acid differences at positions 139 and 144 affect the rate of replication or the spread of infection. Transfection experiments with additional chimeras indicated that the inability of CIA-1 to replicate in MSB1(L) cells is mediated by a larger region of the genome which contains the hypervariable region in addition to upstream amino acid differences. Analysis of chimeras excluding the entire region of open reading frame 1 suggested the presence of a secondary mediator in the progression of infection in culture that was localized to a region containing a single nucleotide difference which results in amino acid differences in both VP2 (V-153) and the nuclear localization signal of VP3 (C-118). Immunofluorescence assays indicated an increased cytoplasmic distribution of VP3 and a general lack of VP3-associated apoptotic bodies in infections of CIA-1 and chimeras containing V-153 or C-118, as opposed to a primarily nuclear distribution and association with well-formed apoptotic bodies in Cux-1(C)-infected cells.

Chicken infectious anemia virus (CIAV) DNA in infected cell cultures and chicken tissues was detected using a polymerase chain reaction (PCR) assay. The complete CIAV genome of several strains was amplified in two segments with two sets of primer pairs. The DNA segments of four CIAV strains and full-length Cux-1 strain DNA were cloned. After amplification, 100 original genome equivalents were detected by Southern hybridization. The sensitivity of the assay was enhanced considerably by performing a reamplification with nested primers. This modification permitted the detection of one molecule of CIAV DNA. Some problems of the assay and its possible application are discussed.

Twenty two hybridoma strains producing monoclonal antibodies against Francisella tularensis ATCC 6223, var. trlarensis, were characterized. In an enzyme-linked-immunosorbent-assay (ELISA) using formaldehyde fixed bacteria as antigens, neither cross-reactions with six different Brucella spp., with Yersinia enterocolitica 0 : 9 nor with two biotypes of Yersinia pseudotuberculosis could be detected. The antibodies gave comparable titres with the three strains of F. tularensis tested. ELISA binding studies indicated that fifteen of the antibodies bound with high affinities to their epitopes of the three Francisella strains, while the others each seemed to bind with low affinity to at least one of the antigens. Immunoblot analysis showed that six of the antibodies were directed to epitopes on the core moiety of the lipopolysaccharide molecule, while the other 16 antibodies bound to 0 side chain components.

Pestivirus infection in domestic ruminants has been reported in several parts of southern Africa (Theodoridis and Boshoff, 1974). In'wildlife naturally occurring bovine viral diarrhoea virus (BVDV) infection has only rarely been reported (Plowright, 1969). It was the purpose of this investigation to record the antibody levels to BVDV in 535 sera from the following 9 Namibian wildlife species: roan antelope The sera originated either from wildlife cropping operations in southern Namibia or from the Etosha National Park in northern Namibia. Neither age nor sex of the sampled animals were known. All sera were stored at -20~ until testing.For the determination of antibody levels, a direct neutralising peroxidase-linked antibody (NPLA) assay using the 0712/Han/80 strain of BVDV was performed (Hyera et aL, 1987). Neutralising antibody titres greater than 1:5 were considered positive.The percentage of seropositive animals within a species, as well as the titre range, is given in Table I. Six out of 9 species were shown to have antibodies to BVDV. The prevalence in seropositive species ranged from 5 to 67 per cent. Giraffe and roan antelope sera showed titres 1 : 1,000; the highest antibody titres were found in 2 giraffe with 1:56,234 and 1:28,184. Oryx, kudu, sable antelope and blue wildebeest had titres of about 1:100 (Table I). All sera originating from red hartebeest, black wildebeest and springbok were free of detectable antibodies against BVDV.The data presented showed that BVDV infection is widespread in Namibian wildlife. Hamblin and Hedger (1979) demonstrated antibodies to BVDV in the sera of 17 out of 45 wildlife species from various African regions. Among these were sera from kudu, oryx, wildebeest, springbok and giraffe sampled in Namibia. In addition, we demonstrated antibodies in sera from roan and sable antelope but failed to detect antibodies in springbok sera.The very high antibody titres in giraffe and roan antelope suggest that these animals could have experienced a recent infection and that the BVDV strain which was used throughout the test is antigenetically similar to field virus strains which infected these animals. The isolation of a cytopathogenic pestivirus from a diseased giraffe in Kenya (Plowright, 1969) and the high titres measured in our survey indicate that giraffe are highly susceptible to pestivirus infection. No significance is attributed to the absence of antibodies in sera from red hartebeest and black wildebeest due to the low number of samples.Unless BVDV persistence and its perpetuation in wildlife species is proven, their role in the epidemiology of BVDV infection in livestock remains obscure.