Marek's disease (MD) in chickens is caused by the alphaherpesvirus MD virus (MDV) and is characterizedby the development of lymphoblastoid tumors in multiple organs. The recent identification and cloning of RLORF4 and the finding that four of six attenuated strains of MDV contained deletions within RLORF4 suggested that it is involved in the attenuation process of MDV. To assess the role of RLORF4 in MD pathogenesis, its coding sequence was deleted in the pRB-1B bacterial artificial chromosome clone. Additionally, RLORF5a was deleted separately to examine its importance for oncogenesis. The sizes of plaques produced by MDV reconstituted from pRB-1B⌬RLORF5a (rRB-1B⌬RLORF5a) were similar to those produced by the parental pRB-1B virus (rRB-1B). In contrast, virus reconstituted from pRB-1B⌬RLORF4 (rRB-1B⌬RLORF4) produced significantly larger plaques. Replication of the latter virus in cultured cells was higher than that of rRB-1B or rRB-1B⌬RLORF5a using quantitative PCR (qPCR) assays. In vivo, both deletion mutants and rRB-1B replicated at comparable levels at 4, 7, and 10 days postinoculation (p.i.), as determined by virus isolation and qPCR assays. At 14 days p.i., the number of PFU of virus isolated from chickens infected with rRB-1B⌬RLORF4 was comparable to that from chickens infected with highly attenuated RB-1B and significantly lower than that from rRB-1B-infected birds. The number of tumors and kinetics of tumor production in chickens infected with rRB-1B⌬RLORF5a were similar to those of P2a chickens infected with rRB-1B. In stark contrast, none of the chickens inoculated with rRB-1B⌬RLORF4 died up to 13 weeks p.i.; however, two chickens had tumors at the termination of the experiment. The data indicate that RLORF4 is involved in attenuation of MDV, although the function of RLORF4 is still unknown.Marek's disease (MD) is a lymphoproliferative disease in chickens caused by a member of the Alphaherpesvirinae subfamily, MD virus (MDV). The pathogenesis of infection with MDV can be divided into four phases (3). Bursa-derived (B) lymphocytes are infected between 3 and 6 days postinfection (p.i.) and are the primary target cells for the first phase of lytic infection, which is followed by infection of activated CD4 ϩ thymus-derived (T) lymphocytes in the second phase. During the second phase, viral replication typically decreases and a latent infection is established between 5 and 10 days p.i. in activated CD4ϩ T lymphocytes. The third phase is characterized by reactivation of MDV replication between 14 and 21 days p.i. After the third phase, lymphomas may develop depending on the genetic susceptibility of the chickens and the virulence of the virus strain.The MDV genome consists of two unique regions, the unique short region (U S ) and the unique long region (U L ), flanked by inverted repeats known as the inverted repeat long (IR L ) and short (IR S ), and the terminal repeat long (TR L ) and short (TR S ). The MDV Eco Q (Meq or RLORF7) and viral interleukin-8 (IL-8) homologue genes and the open reading frames ...
Several outbreaks of gout were reported in commercial broilers in India during 2011 and 2012, causing up to 40% mortality in the birds. Gross and histopathological observations confirmed gout. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) analysis from kidney samples of gout-affected birds indicated the presence of chicken astrovirus (CAstV) in 41.7% of cases and a mixed infection of CAstV and avian nephritis virus (ANV) in 36.4% of cases. CAstV isolated from gout-affected kidneys by inoculating embryonated specific pathogen free (SPF) eggs showed dwarfing in embryos and a cytopathic effect in chicken embryo kidney cells. Inoculation of 1-day-old SPF and broiler chicks with CAstVs caused gout and mortality between 4 and 10 days post inoculation. Virus isolation and qRT-PCR analysis showed the presence of only CAstV in inoculated chicks. Sequence analysis of capsid genes indicated a major group of Indian CAstVs that displayed 92.0 to 99.2% intergroup amino acid identity and 83.9 to 90.4% identity with subgroup Bi CAstVs of UK origin. We designated this group Indian Bi. Analysis of the partial polymerase amino acid sequences of our isolates indicated two groups of CAstVs (Indian 1 and 2) that displayed 90.2 to 95.5% amino acid identity between them. We thus report for the first time that, in addition to infectious bronchitis virus and ANV, CAstVs are a causative agent of gout.
A new isolate of Marek's disease virus (MDV) was described. This virus, SB, and a clone, SB-1, differed from pathogenic isolates in in vitro growth characteristics as described for other apathogenic isolates. Serologically, as with other apathogenic isolates, SB could be distinguished from pathogenic MDV and the avirulent turkey herpesvirus. SB failed to induce lesions characteristic of Marek's disease (MD) during a 6- to 11-week experimental period. Also, SB was nononcogenic in immunosuppressed chickens or in chickens inoculated with this virus in ovo. However, under those conditions, SB caused a cytolytic infection. The term "nononcogenic" rather than "apopathogenic" was therefore proposed to classify this and similar isolates. SB-1 protected chickens against challenge with either virulent MDV or the non-virus-producing MD tumor transplant, JMV. Possible mechanisms of protection are discussed.
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