Malignant Catarrhal Fever Virus Research Articles

PREVALENCE OF ANTIBODY TO MALIGNANT CATARRHAL FEVER VIRUS IN WILD AND DOMESTIC RUMINANTS BY COMPETITIVE-INHIBITION ELISA

A competitive-inhibition ELISA (CI-ELISA), based on a monoclonal antibody to an epitope conserved among malignant catarrhal fever virus (MCFV) strains of both wildebeest and sheep origin, was used to determine the prevalence of antibody to MCFV in selected domestic and wild ruminants, both free-ranging and captive, from the USA. We evaluated 2528 sera from 14 species between 1990 and 1995, including 80 pronghorn antelope (Antilocapra americana), 339 bighorn sheep (Ovis canadensis), 103 biston (Bison bison), 17 black-tailed deer (Odocoileus hemionus columbianus), 395 domestic cattle (Bos taurus), 291 domestic goats (Capra hircus), 680 domestic sheep (Ovis ammon), 323 elk (Cervus elaphus), 41 llamas (Lama glama), 21 mouflon sheep (Ovis musimon), 54 mountain goats (Oreamnos americanus), 101 mule deer (Odocoileus hemionus), 20 muskox (Ovibos moschatus), and 63 white-tailed deer (Odocoileus virginianus). A high seroprevalence (37 to 62%) was observed in domestic sheep, domestic goats, muskox, and some bighorn sheep populations. Seroprevalence in these species was generally age-related: a very low seroprevalence was present in these animals under one year of age. A low seroprevalence (2% to 13%) was found in clinically-susceptible species such as domestic cattle, deer, elk and bison, supporting the concept that significant numbers of non-lethal infections occur among clinically susceptible ruminants.

Detection of Sheep-Associated Malignant Catarrhal Fever Virus Antibodies by Complement Fixation Tests.

Some serological diagnosis methods and examinations for detection of antibodies to sheep-associated malignant catarrhal fever (MCF) infection were investigated. The wildebeest-associated MCF virus strain WC11 propagated on fetal bovine thyroid cell cultures was used as an antigen. Antibodies were detected by complement fixation (CF) tests in cattle pathologically diagnosed as having sheep-associated MCF, as well as in cattle experimentally infected with MCF virus strain WC11. However, immunodiffusion precipitation was only detected in cattle infected with MCF virus strain WC11. The results of serological investigation by CF tests indicated that 64.3% of sheep possessed antibodies to MCF virus in the Hokkaido district of Japan and all serum samples which contained CF antibody titers greater than 1:4 had antibody titers larger than 1:8 in indirect immunofluorescence tests. The CF test we demonstrated here is available to quantitatively detect MCF virus antibody titers in epidemiological surveys.

Investigation of sheep-associated malignant catarrhal fever virus infection in ruminants by PCR and competitive inhibition enzyme-linked immunosorbent assay

Development of control measures for the gammaherpesviral disease of cattle known as sheep-associated malignant catarrhal fever (SA-MCF) has been hampered by a lack of accurate diagnostic tests either for the causative virus or for antibody against that virus. A recently developed competitive-inhibition enzyme-linked immunosorbent assay (CI-ELISA) for the detection of antibody to malignant catarrhal fever (MCF) virus (MCFV) in ruminants based on a monoclonal antibody to a widely conserved epitope of MCFV (H. Li, D. T. Shen, D. P. Knowles, J. R. Gorham, and T. B. Crawford, J. Clin. Microbiol. 32:1674-1679, 1994) and a PCR assay based on previously reported primers (S. I. F. Baxter, I. Pow, A. Bridgen, and H. W. Reid, Arch. Virol. 132:145-159, 1993) were used to detect anti-MCFV antibody and SA-MCFV DNA in sheep and other ruminants. The PCR amplified a specific 238-bp SA-MCFV genomic DNA fragment from peripheral blood lymphocytes of adult sheep and other ruminants with clinical MCF. Of 144 samples from randomly selected healthy adult sheep, 143 (99%) were positive by PCR and 136 (94%) were positive by CI-ELISA. The agreement between the two assays exceeded 95%. Of nine samples collected from cattle and deer with clinical MCF of apparent sheep origin, seven were CI-ELISA positive and all 9 were PCR positive. Among 59 serum samples from presuckling lambs, none contained antibody detectable by CI-ELISA. After suckling, maternal anti-MCFV antibody was detectable for about 10 +/- 3 weeks. Although all colostrum and milk samples from infected ewes were strongly PCR positive, the appearance of detectable SA-MCFV DNA in lambs was correlated generally with antibody patterns, which suggests that the natural infection event in sheep may not occur during the perinatal period but occurs sometime later in life.

Multiple Superinfections Fail to Activate Defective Human Immunodeficiency Virus-1 (HIV-1) Infection of Rabbits

Superinfection of human immunodeficiency virus (HIV)-1-infected rabbits with Treponema pallidum, Mycobacterium avium, herpes simplex, Candida albicans, Mycoplama incognitus, and malignant catarrhal fever virus, as well as irradiation or cortisone treatment, fails to activate production of infectious virus. For up to 6 months after infection of rabbits with HIV-infected cells or free virus, there are neither clinical symptoms nor positive laboratory tests for detection of HIV. However, after superinfection with other agents, HIV sequences may be transiently found in peripheral blood mononuclear cells by polymerase chain reaction (PCR), and multiple antibodies to HIV antigens may be detected by Western blotting. Both the PCR positivity and Western blot reactivity become negative with time after superinfection. Other than delayed healing of the skin lesions produced by T. pallidum and vaccinia in HIV-infected rabbits, there is no evidence of any immune abnormality. After death, gag sequences are detectable in the splenocytes of essentially every HIV-infected rabbit, and the splenocytes of eight of 25 infected rabbits responded by proliferation to HIV peptides. In addition, gag sequences are detectable in rabbits that are injected with lymphoid cells from HIV-infected rabbits. However, after multiple testing of both peripheral blood of living rabbits and organs of rabbits that died or were killed (spleen, brain, lymph nodes, liver, and gastrointestinal tract), no viable virus has ever been convincingly detected by in vitro cultivation with indicator cells. In contrast to some other published reports, these data indicate that HIV-1 infection of rabbits does not provide a model for AIDS pathogenesis therapy or prevention, but it may be useful as a model to study the relative resistance of a small fraction of the human population to development of AIDS after HIV infection.

Identification and characterization of the major proteins of malignant catarrhal fever virus.

Malignant catarrhal fever virus (MCFV), a gamma-herpesvirus, causes a severe inflammatory and lymphoproliferative disease of cattle and other susceptible ruminants. Polyclonal antisera and monoclonal antibodies (MAbs) to the Minnesota isolate of MCFV were produced and used to examine the characteristics of the viral proteins. Immunoprecipitation of antigens of the Minnesota isolate of MCFV with polyclonal antisera revealed at least 11 proteins with molecular masses ranging from 17 kDa to 145 kDa. Among 279 candidate anti-MCFV hybridomas, 14 were selected and clustered into six groups on the basis of the patterns of reactivity to viral proteins in immunoprecipitation and immunoblot. The group I MAbs exhibited strong neutralizing activity and recognized a glycosylation-dependent conformational epitope on a 110 kDa protein. The MAbs in group II bound a non-neutralizing conformational epitope on a 130 kDa non-glycosylated protein. A glycosylated protein complex of 115/110/105/78/45 kDa moieties was identified by the MAbs in group III. The MAbs in groups IV, V and VI reacted with non-glycosylated proteins of 36/34 kDa, 24 kDa and 17 kDa, respectively. Comparison of three MCFV isolates [the Minnesota isolate, the Austrian isolate (Au-732) and the African prototype isolate (WC-11)] revealed no apparent differences in immunoprecipitation patterns with the single exception that the 110 kDa protein of WC-11 was slightly smaller than its counterpart in the Minnesota isolate.

Chronic generalized obliterative arteriopathy in cattle: a sequel to sheep-associated malignant catarrhal fever.

Malignant catarrhal fever (MCF) in cattle is generally associated with a short clinical course and a high case fatality rate (90-95%). The lesions in cattle that survive acute MCF for a prolonged period or appear to recover have not been documented. In a naturally occurring outbreak of MCF in a herd of beef cattle in Wyoming, 7 of 84 yearling heifers (8.3% of replacement herd) and 2 of 230 cows (0.9% of cow herd) developed clinical signs of pyrexia, mucopurulent discharge, bilateral keratitis, and weight loss following contact with ewes that had lambed 34-62 days earlier. Six of 9 affected cattle were examined postmortem following clinical signs (CS) that developed 2-150 days earlier. Three cattle with CS for < or = 39 days had lesions of regional lymphadenopathy and widespread severe segmental lymphoid arteritis-phlebitis that were typical of acute MCF, and proliferative intimal lesions were present in a small proportion of arteries at days 20 and 39 of CS. By contrast, 3 cattle that survived to 90, 105, and 150 days after clinical onset had distinctive arterial lesions in multiple organs, characterized by proliferative concentric fibrointimal plaques, disrupted inner elastic lamina, focally atrophic tunica media, and vasculitis of variable severity. Immunohistochemical and ultrastructural examination of intimal plaques identified the predominant cellular component to be smooth muscle cells with a contractile phenotype. No viral structures were seen. Serologic studies, using a competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) that detects antibody to an epitope broadly conserved among isolates of the MCF virus, found that 2 chronically affected cattle were serologically positive between days 42 and 100 of CS, with seroconversion in 1 animal between days 52 and 73 of CS. Seroprevalence was 7.9% in the 76 remaining healthy animals of the replacement heifer herd and 40% (75% in adult sheep and 4% in lambs) in the in-contact sheep flock 77 days after onset of CS in the index case. This episode suggests that, in addition to the common and well recognized acute form of MCF in cattle, this viral infection encompasses a disease spectrum that includes chronic disease and partial to "complete" clinical recovery, and in recovered animals chronic obliterative arteriopathy is the preeminent lesion.

Polymerase chain reaction amplification of wildebeest-associated and cervine-derived malignant catarrhal fever virus DNA.

A polymerase chain reaction (PCR) assay was developed for the detection of alcelaphine herpesvirus 1 (AHV1), a causative agent of malignant catarrhal fever (MCF) of ruminants. A pair of 20-base primers was constructed based on the published nucleotide sequence of gene A of the WC11 isolate of AHV1 and was used to amplify a DNA fragment of 413 base pairs. The optimised PCR assay was highly sensitive, i.e. it detected 10 fg of genomic DNA of AHV1 (WC11 isolate). The amplified fragment was shown to be specific for AHV1 DNA by (i) cleavage with XbaI which yielded 2 subfragments of approximately 140 and 280 base pairs and (ii) chemiluminescence Southern blot hybridisation with a digoxigenin-labelled 25-base internal probe. The PCR assay also amplified AHV1 gene sequences in tissue samples from deer and rabbits experimentally infected with materials derived from deer with clinical sheep-associated MCF.

Competitive inhibition enzyme-linked immunosorbent assay for antibody in sheep and other ruminants to a conserved epitope of malignant catarrhal fever virus

Malignant catarrhal fever (MCF) is a severe, usually fatal, acute systemic disease syndrome of certain domestic and wild ruminants caused by members of the family Gammaherpesvirinae. Two distinct but closely related viruses cause clinically indistinguishable syndromes: one that is indigenous to the widebeest and the other that apparently is indigenous to domestic sheep. Neither the pathogenesis nor the epidemiology of sheep-associated MCF (SA-MCF) is understood, primarily because of a lack of adequate detection methods for the etiologic agent or antibody against it. No acceptably documented isolates of SA-MCF virus have been reported, and existing antibody assays suffer from significant cross-reactivity with other viruses. As a basis for a specific serologic assay, an attempt was made to identify an epitope conserved among all isolates of MCF viruses, by using a monoclonal antibody (MAb) produced against a previously reported U.S. isolate of MCF virus. A MAb (15-A) which bound a conserved epitope present on all four isolates of MCF virus examined was found. MAb 15-A did not react with eight common sheep and goat viruses or five common bovine viruses. Immunoprecipitation revealed that the 15-A epitope was located on the viral glycoprotein complex, with molecular masses of 115, 110, 105, 78, and 45 kDa. Sera from experimentally and naturally infected animals which yielded a similar glycoprotein complex immunoprecipitation pattern competed with MAb 15-A for its epitope. A competitive inhibition enzyme-linked immunosorbent assay (ELISA) based on MAb 15-A was therefore developed. The assay detected antibody in inapparently infected sheep and in cattle, deer, and bison with clinical MCF. Of the 149 serum samples from sheep associated with MCF outbreaks, 88 (55%) were seropositive by competitive inhibition ELISA.

Attemps to immunize cattle against virulent African malignant catarrhal fever virus (alcelephine herpesvirus-1) with a herpesvirus isolated from American cattle

Two consecutive weekly inoculations with a herpesvirus isolated from sick cattle in America (707K), protected four out of four steers against a first challenge with virulent African malignant catarrhal fever virus (alcelaphine herpesvirus-1), strain C500. Three of these steers were still protected in a rechallange carried out 9.5 months after the first challenge. One inoculation with this agent did not protect such steers, and repeated weekly inoculations had the risk of inducing a malignant catarrhal fever-like disease. In addition such repeated inoculation did not necesarily confer adequate protection, either in the first or the second challenge. There was no correlation between the development of virus neutralizing antibody and protection to challenge with the virulent virus. Endonuclease analysis of the genome of 707K virus, revealed differences between the agent and the avirulent cell-free form of the virulent African malignant catarrhal fever virus (WC11).

Nucleotide sequence of a 3.5 kilobase fragment of malignant catarrhal fever virus strain WC11

A 3.5 kilobase DNA fragment of the malignant catarrhal fever virus (MCFV), strain WC11, was mapped with a number of restriction enzymes, subcloned and sequenced. The fragment was subcloned into plasmid vector, pUC19, for direct sequencing. A complete open reading frame of 2,058 base pairs and a partial open reading frame of 630 base pairs were identified. The sequence of 3,389 nucleotides was compared to other herpesviruses. A 310 base pairs sequence in gene A was 57% homologous to a sequence in reading frame BXLF1 of Epstein-Barr virus strain B95-8.

Epidemiologic and pathologic aspects of an epizootic of malignant catarrhal fever in exotic hoofstock.

An epizootic of malignant catarrhal fever (MCF) occurred at the Los Angeles Zoological Park which resulted in the deaths of four exotic ungulates. The source of infection was considered to be a newly purchased wildebeest bull (Connochaetes taurinus taurinus) that had been negative for antibody to MCF virus by an indirect immunofluorescent test. The need to re-evaluate regulations for the transportation and housing of young wildebeest is emphasized by this MCF outbreak. The diagnostic technology now available for identifying asymptomatic carriers of MCF virus and the present understanding of the behavior and pathogenesis of this highly cell-associated herpesvirus in exotic ruminants should provide a basis for the prevention and control of MCF in zoological parks.

Immunoblotting analysis of the reaction of wildebeest, sheep and cattle sera with the structural antigens of alcelaphine herpesvirus-1 (malignant catarrhal fever virus)

Malignant catarrhal fever (MCF) is a disease of cattle and some other ruminants caused by alcelaphine herpesvirus-1 (AHV-1), a virus of wildebeest. The disease also occurs in the absence of wildebeest and is then thought to be caused by a viral agent harboured by the sheep. The structural proteins of AHV-1 have been used as antigens for the immunoblotting analysis of sera from wildebeest, sheep and cattle infected by either AHV-1 or the “sheep-associated” form of the disease. Wildebeest sera showed a uniform response reacting strongly with six polypeptides. Sheep sera also gave positive results but individual sera reacted with varying subsets of the antigens recognized by wildebeest. These results support the earlier suggestion that sheep harbour a herpesvirus related to AHV-1. A bovine serum from a case of MCF caused by AHV-1 also reacted only with a subset of the six wildebeest-reactive polypeptides. Sera from cattle affected with the “sheep-associated” form of the disease gave reactions in only two of the eight cases tested; both positive sera reacted to a few polypeptides only.

Immunological relationships between malignant catarrhal fever virus (Alcelaphine herpesvirus 1) and Bovine cytomegalovirus (Bovine herpesvirus 3)

Strains of malignant catarrhal fever virus (alcelaphine herpesvirus 1 (AHV-1)) and bovine cytomegalovirus (bovine herpesvirus 3 (BHV-3)) were compared for serological relatedness by cross-titration in an indirect immunofluorescent (IIF) antibody assay. There was definite cross-reactivity between these 2 viruses, with heterologous sera staining intracellular and membrane antigens of infected cells. Heterologous antibody titres were ≈ 50-fold lower than homologous titres and could be removed by absorption with either homologous or heterologous virus-infected cells, but not with uninfected cells. Regression analyses of IIF antibody titres to AHV-1 and BHV-3 virus in 3 groups of wild ungulate sera also indicated a serological relationship between these herpesviruses. In a cross-immunity trial, 2 of 3 cattle immunized with a BHV-3 virus and 2 of 3 cattle immunized with avirulent AHV-1 resisted challenge with virulent AHV-1-infected blood which killed 3 unimmunized controls. These results are discussed particularly with respect to the involvement of BHV-3 in malignant catarrhal fever.

Concurrent malignant catarrhal fever and bovine virus diarrhoea virus infection in a dairy herd.

An account is given of an outbreak of malignant catarrhal fever which occurred in a 98-cow dairy herd. Ten animals died or were slaughtered and the disease was confirmed by clinical and histological examination. Serological tests for malignant catarrhal fever virus were positive in three of four animals. The diagnosis of malignant catarrhal fever was complicated by the presence of bovine virus diarrhoea virus infection in three of the early cases. The initial cases of malignant catarrhal fever occurred in a group of nine-month-old calves which were housed in an old milking parlour with 19 pedigree Suffolk ewes at lambing time. Later cases occurred in two adult cows and in two heifers. Investigations of the remainder of the herd for evidence of bovine virus diarrhoea virus did not reveal the presence of any persistently infected cattle. Serological examinations for antibody to malignant catarrhal fever and bovine virus diarrhoea virus were carried out on the 19 Suffolk ewes. Six of them had neutralising antibody titres to malignant catarrhal fever virus and three were positive in the indirect immunofluorescence test. The possible roles of bovine virus

Course of malignant catarrhal fever in immunosuppressed and immunostimulated rabbits.

Rabbits pretreated with cyclophosphamide for 7 days (CY+) and control rabbits (CY-), were infected with cell-associated malignant catarrhal fever virus (MCFV), and CY treatment of the CY+ group was continued to day 20 p.i. The time of onset and degree of antibody formation to bovine serum albumin was significantly suppressed in the CY+ group whilst the humoral antibody response to MCFV appeared to be delayed rather than suppressed. Although incubation periods of the disease were comparable in the CY+ and CY- groups, the disease course was much shorter in the CY- group, 100% mortality occurring within a mean of 4.5 days, as opposed to a mean of 15 days in CY+ animals. Mortalities did not occur in the CY+ group until a mean of 5.5 days following withdrawal of CY. In further experiments it was shown that pre-existing antibody to MCFV had no effect on the incubation period and course of MCF in rabbits. The results thus suggest that MCF may not be an immune complex disease.

Neutralising antibodies to wildebeest-derived malignant catarrhal fever virus in African wildlife

A total of 2,722 sera collected between 1963 and 1983, from 43 different species of wildlife in 11 African countries was examined for neutralising antibodies against the wildebeest-derived strain of malignant catarrhal fever (MCF) virus. Antibodies were demonstrated in 10 species of Bovidae which included eight species from the sub-family Hippotraginae and one species each from Bovinae and Antilopinae. Neutralising antibodies were also recorded in hippopotamus. It is suggested that the high prevalence of antibodies recorded in sera from waterbuck and reedbuck indicate infection with MCF. However, titres in other species may be due to antigenically related viruses.

Infectivity of cell-free malignant catarrhal fever virus in rabbits and cattle.

Malignant catarrhal fever was induced in cattle and rabbits inoculated intranasally with cell-free wildebeest-calf nasal and ocular secretions. This method of reproducing the disease is similar to that occurring in nature and should prove useful as a means of challenging experimentally induced immunity.

Role of wildebeest fetal membranes and fluids in the transmission of malignant catarrhal fever virus.

Malignant catarrhal fever virus was not isolated from samples of fetal membranes or fluid collected from 93 calving wildebeest (Connochaetes taurinus) in Kenya Maasailand. Cell-free strains of malignant catarrhal fever virus were very rapidly inactivated when exposed to the sun under field conditions, at least 3.0 log10 units/25 microliter being lost per hour at midday. It is suggested that wildebeest fetal membranes and fluids act as visual markers for areas of pasture which are particularly heavily contaminated with malignant catarrhal fever virus in oculonasal secretions of wildebeest calves. It is possible that starting to graze cattle one to two hours later each morning may be a useful measure for helping to protect cattle from malignant catarrhal fever in areas where they are forced to share pastures with calving wildebeest.

Antibodies in carrier Wildebeest to the lymphoproliferative herpesvirus of malignant catarrhal fever

Six types of antibody to malignant catarrhal fever virus (MCFV) were measured in 132 sera collected from Wildebeest in Kenya Masailand. The titre of all types of antibody declined slowly with increasing age of the wildebeest. A significantly greater proportion of wildebeest calves had higher titres of antibodies to MCFV early antigens, IgM antibodies to MCFV late antigens and complement-fixing antibodies, than did older animals. One seronegative calf, reared in isolation without colostrum, became seropositive 4 1 2 weeks after birth but did not show any clinical signs indicative of MCFV infection. Similarities between MCFV infection of wildebeest calves and other inapparent infections with lymphoproliferative herpesviruses are discussed.

Antibodies to malignant catarrhal fever virus in cattle with non-wildebeest-associated malignant catarrhal fever

Sera from 48 cattle with non-wildebeest-associated malignant catarrhal fever (MCF) were assayed for antibodies to wildebeest-associated MCF virus. Significant titres were found in 38 sera and these reactions appeared to be specific. Some cases of non-wildebeest-associated MCF may be caused by an agent antigenically related to MCFV.