Comparative features of low‐virulence and high‐virulence marek's disease virus Infections

Smith, M. W.; Calnek, B. W.

doi:10.1080/03079457409353837

Cited by 9 publications

(7 citation statements)

References 19 publications

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“…A pathotypic classification of mildly virulent (m) was proposed (Witter, 1997) to include serotype 1 strains such as CU2 (Smith & Calnek, 1974), B14 (Biggs & Payne, 1963) or other classical isolates (Biggs & Payne, 1967;Biggs & Milne, 1972). Such strains are less virulent than viruses of the v pathotype such as the JM, GA and HPRS-16 strains.…”

Section: Pathotyping Mild Strainsmentioning

confidence: 99%

Classification of Marek's disease viruses according to pathotype: philosophy and methodology

Witter¹,

et al. 2005

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The concept of pathotype in Marek's disease (MD) probably dates from the recognition of a more virulent form of the disease in the late 1950s (Benton & Cover, 1957). Distinctions between MD virus strains were further expanded with the description of the vv pathotype in the early 1980s and of the vv+ pathotype in the 1990s. Pathotype designations reflect important biological properties that correlate with the break-through of vaccinal immunity in the field. However, pathotyping methods applied by various laboratories have not been uniform, preventing critical comparison of results. Better uniformity of pathotyping procedures is desirable.The Avian Disease and Oncology Laboratory (ADOL) method is based on induction of lymphoproliferative lesions in vaccinated chickens. This method has been used to pathotype more than 45 isolates and is the basis for the current pathotype classification of MD virus strains. Its limitations include requirements for a specific type of chickens (15x7 ab+), large numbers of animals, and a statistical method to compare lesion responses to those of JM/102W and Md5 control strains. Because of these limitations, it has not been and is not likely to be used in other laboratories. Comparability in pathotyping can be improved by the comparison of field isolates with standard prototype strains such as JM/102W, Md5 and 648A (American Type Culture Collection) or their equivalents. Data may be generated by different in vivo procedures that measure tumour induction, neurological disease (both neoplastic and non-neoplastic lesions), or solely non-neoplastic criteria (such as lymphoid organ weights or virus replication). Methods based on neoplastic criteria, especially when generated in MD-immunized chickens, will probably correlate most closely with that of the ADOL method and be most relevant to evolution of MD virus in the field. Based on data from several trials, a modification of the ADOL method that utilizes fewer chickens and can be conducted with commercial specific pathogen free strains is proposed. The modified method is based on "best fit" comparisons with prototype strains, and is expected to provide results generally comparable with the original method. A variety of other alternative criteria (see earlier) are also evaluated both for primary pathotyping and as adjuncts to other pathotyping methods. Advantages and disadvantages of alternative methods are presented.

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Section: Pathotyping Mild Strainsmentioning

confidence: 99%

Classification of Marek's disease viruses according to pathotype: philosophy and methodology

Witter¹,

et al. 2005

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“…MDV inocula were cloned isolates JM-10, GA-5 (Calnek, 1973), CU-2 (Smith and Calnek, 1974), RB-1B (Schat etal., 1982a) and JM-l6(Calneketal., 1984). All had been serially passaged from 5 to 83 times in spleen-cell cultures as described .…”

Section: Viral Inoculamentioning

confidence: 99%

Further characterization of marek's disease virus‐infected lymphocytes. II. In vitro infection

Calnek

Schat

Ross

et al. 1984

Intl Journal of Cancer

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Lymphocyte cultures from chicken spleens had been shown to be susceptible to in vitro infection by Marek's disease virus (MDV)4 in an earlier report from this laboratory. In that study, virus infection was evidenced by virus isolation and detection of viral internal antigen (VIA) 2 days post inoculation (DPI), and serial passage was accomplished by adding fresh spleen cells at 2-day intervals. The susceptible cells were identified as bursa-derived lymphocytes (B cells). Using a dual fluorescence technique to identify surface markers for B cells, thymus-derived lymphocytes (T cells) or Ia antigen on VIA-positive cells, we have now shown that a small proportion (generally less than 10%) of VIA-positive cells observed 2 DPI are T cells, and that a low level of infection can be maintained by serial passage of MDV in cultures totally free of B cells. Most infected T cells in this study had Ia antigen. As the incubation period for infected cultures was extended from 2 to 4 or 5 days, the average number of viable cells decreased but the percentage of viable cells infected with MDV (VIA-positive) increased. Also, both the proportion and the actual number of infected T cells increased, significantly more so in cultures from genetically susceptible P-2 donors than from resistant N-2 donors. Spleen-cell cultures from resistant Line 6 chickens were markedly less susceptible than those from susceptible Line 7 chickens to in vitro MDV infection, as assessed by numbers of VIA-positive cells at 5 DPI.

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“…Smith and Calnek (1974) found that the MD response (in terms of incidence and mean time to death) in genetically susceptible birds given virulent virus was maximal even when a limiting dilution of virus was inoculated. Sharma (1973) was unable to break through the genetic resistance of RPL Line 6 chickens with 10 6 times the dose of MD virus required to induce a neoplastic response in RPL line 7.…”

Section: Resultsmentioning

confidence: 99%

The effect of virus dose on the development of Marek's disease in two strains of chickens

et al. 1980

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SUMMARYThe effect of inoculating different doses of Marek's disease virus on the consequent lymphocyte-associated viraemia titres, survival time and mortality was studied in two strains of chickens, one highly susceptible (a strain of Rhode Island Red) and one moderately resistant (a strain of Light Sussex) to Marek's disease. In both strains an increase in the infecting dose of virus increased the ensuing viraemia, and there was an inverse relationship between virus dose and survival time. There was a negative correlation between viraemia titres and survival time. The modulation of infecting dose had no effect on overall mortality among the susceptible, Rhode Island Red strain, chickens, but did influence the mortality of the Light Sussex strain chickens. It was suggested that the outcome of infection within an individual may be determined by a rather subtle interaction between the infection and transformation of a limiting number of target cells and an immune response directed against such infected or transformed cells, and that in different breeds of chickens these two factors may differ in importance. INTRODUCTIONMarek's disease (MD) is an economically important lymphoproliferative disease of the domestic fowl caused by aherpesvirus (MDV). The incidence of MDV infection is high but the disease incidence is quite variable. The factors that influence the extent of losses in infected flocks may be related either to the virus or to the host and include virus strain, route of infection, age at time of exposure to the virus, genetic constitution of the host, sex, the presence of maternal antibodies and stress (Payne et al, 1976). Little attention has been paid to the question of virus dosage although this may be of importance under natural conditions. We have studied this aspect of MDV infection by inoculating graded doses of virulent virus into 1-day-old chickens of two different strains, one highly susceptible to MD and one moderately resistant. Titres of lymphocyte-associated viraemia were determined at 16 and 38 days after infection, and birds that died were examined post mortem for evidence of MD.

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Comparative features of low‐virulence and high‐virulence marek's disease virus Infections

Cited by 9 publications

References 19 publications

Classification of Marek's disease viruses according to pathotype: philosophy and methodology

Classification of Marek's disease viruses according to pathotype: philosophy and methodology

Further characterization of marek's disease virus‐infected lymphocytes. II. In vitro infection

The effect of virus dose on the development of Marek's disease in two strains of chickens

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