Herpesvirus Of Malignant Catarrhal Fever Research Articles

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.

Immune complexes associated with infection of cattle by the herpesvirus of malignant catarrhal fever

Associated with the fatal lymphoid proliferation induced by the herpesvirus of African malignant catarrhal fever (MCFV) was the deposition of immune complexes comprising immunoglobulin, complement and conglutinin in the kidneys of cattle with terminal pyrexia due to infection with this virus. Such deposits were common in glomeruli and were also seen in renal arteries with and without lesions. Absence of lytic complement and a significant depletion of conglutinin in terminal sera confirmed the activation of complement. However, virus antigen was only rarely detected and virus-specific antibody could not be demonstrated in the deposits. These disparities and the importance of the observations are discussed.

Target cells for malignant catarrhal fever virus in rabbits.

Lymphocytes from lymph nodes and spleens of malignant catarrhal fever virus (MCFV) infected rabbits were tested for MCFV infectivity in secondary calf thyroid cell monolayers. Most infectivity was demonstrated in the lymphocytes. Some infectivity was also detected in macrophages/monocytes. It was thus concluded that lymphocytes form the major target cell for the herpesvirus of malignant catarrhal fever in rabbits.

The detection and behaviour of the herpesvirus of malignant catarrhal fever in bovine lymphocytes.

In calves as in rabbits MCFV infectivity was detected in differentiated lymphocytes of 11 to 13 µm diameter and not in the proliferating lymphoblastoid cells. The increase in the number of infectious lymphocytes on explant was less in cattle than in rabbits but the initial infectivity was higher. Explanations for these disparities are suggested.

The location of primary replication of the herpesvirus of bovine malignant catarrhal fever in rabbits

The herpesvirus of malignant catarrhal fever (MCFV) was isolated from the spleen of 2 3 rabbits 4 days after the intravenous inoculation of infectious lymph node suspension, while no virus could be isolated at 2 and 6 days post inoculation (p.i.). Indirect immunofluorescence identified the antigen-positive cells at 4 days p.i. as medium sized lymphocytes lying in the venous sinuses of the spleen, lower numbers of fluorescing cells being seen in the paracortical areas of lymph nodes and in the thymus. Scanty fluorescence, without isolation of virus, was evident in the spleen at 6 days p.i. but by day 8 p.i. virus could be isolated irregularly from spleen and lymph nodes and at 12 days p.i. was found in all lymphoid tissues in those rabbits with lymphadenitis and pyrexia. The primary replication in the spleen at 4 days is compared with other herpes induced lymphoproliferative disorders.

Isolation and characterization of a herpesvirus from topi ( Damaliscus korrigum, ogilby)

A cell-associated herpesvirus was isolated from kidney and thyroid cell cultures established from 4 out of 18 topi. The virus isolates were found to be antigenically related to the herpesvirus of malignant catarrhal fever derived from wildebeest. Preliminary studies suggest that this virus is not pathogenic to cattle.

The development of delayed cutaneous hypersensitivity in rabbits infected with the herpesvirus of malignant catarrhal fever

Delayed-type hypersensitivity (DTH) was demonstrated in malignant catarrhal fever (MCF) virus-infected rabbits intradermally injected with homologous viral antigens. The response was first detected four days post-infection (pi) and was maximal on day 7 pi. DTH could not be demonstrated after the onset of pyrexia. The abrogation of DTH in MCF virus-infected rabbits is discussed in relation to the pathogenesis of the disease.

Antibodies to malignant catarrhal fever virus antigens in the sera of normal and naturally infected cattle in Kenya

Six different serological tests were used to examine Kenyan cattle sera for antibodies to the herpesvirus of malignant catarrhal fever. Significantly higher levels of indirect immunofluorescent antibody to early and late virus antigens and of complement fixing antibody were found in the sera of 13 naturally infected cattle than in 482 sera collected from four different groups of normal cattle. Virus neutralising and immunoprecipitating antibodies were also found in some infected cattle sera but not in normal cattle sera. Many non-specific reactions occurred using counterimmunoelectrophoresis. These preliminary results indicate that the serological diagnosis of wildebeest-associated malignant catarrhal fever may be possible.

The protection of rabbits against the herpesvirus of malignant catarrhal fever by inactivated vaccines

Cell-free virulent malignant catarrhal fever virus inactivated by either formalin or acetylethylenimine (AEI) and administered with Freund's complete adjuvant protected rabbits against two consecutive parenteral challenges with cell-free virus. However 'protected' rabbits succumbed within 20 days to later inoculation of infected rabbit lymph node suspensions. Both inactivated vaccines evoked high titres of neutralising and immunofluorescent antibody, but more of the rabbits given the AEI preparation showed pyrexia after the first challenge with cell-free virus. The degree of protection afforded was compared with that induced by inactivated antigens of other herpesviruses which cause lymphoproliferative disorders

Persistent Infection of Cattle with the Herpesvirus of Malignant Catarrhal Fever and Observations on the Pathogenesis of the Disease

A case of persistent MCF virus infection is described. A steer was inoculated with attenuated virus and apparently withstood challenge with virulent MCF virus. Five months later it developed a viraemia which persisted for four weeks and the animal died after only one day’s fever. Post-mortem and histological studies showed extensive ulcerative, haemorrhagic enteritis and a necrotizing polyvasculitis with mononuclear leucocyte infiltration. Experimental studies have demonstrated viraemia to preceed fever in cases of acute MCF. The pathogenesis of MCF is discussed in the light of these findings and it is concluded that MCF might be an immune complex disease.

Immunisation of cattle against the herpesvirus of malignant catarrhal fever: failure of inactivated culture vaccines with adjuvant

Attempts were made to immunise cattle against the herpesvirus of malignant catarrhal fever by inoculating living or formalinised preparations of the agent, propagated in cell cultures and combined with Freund's incomplete adjuvant. High and persistent levels of virus-neutralising antibody were regularly demonstrable, especially following two intramuscular inoculations at an interval of six to eight weeks. In spite of this no protection was demonstrable against parenteral challenge with virulent virus, whether in cell-free or cell-associated form. In a controlled field trial vaccinated cattle showed no evidence of protection against natural challenge by exposure to wildebeest herds. It was concluded that humoral mechanisms are probably not important in determining resistance to infection with virulent MCFV.