Summary auto-generated
This study investigated the replication kinetics of equine herpesvirus type 3 (EHV-3) in cultured equine epithelial cells (ETCC cells). Using a one-step growth curve, the researchers found that EHV-3 has a short 4-hour eclipse period, with new infectious virus detectable by 5 hours post-infection and maximum virus yield (200 plaque-forming units per cell) achieved by 10-12 hours. Notably, 90% of newly formed virus remained cell-associated rather than being released into the culture medium. EHV-3 infection rapidly suppressed host cell nucleic acid synthesis, reducing incorporation rates to 30% for RNA and 10% for DNA by 2 hours post-infection. Using density gradient centrifugation and DNA-RNA hybridization techniques, the researchers determined that viral DNA and RNA synthesis began within 2 hours of infection and peaked between 4-7 hours, preceding maximum infectious virus production. Compared to other equine herpesviruses (EHV-1 and EHV-2), EHV-3 demonstrated the most rapid replication cycle, with earlier onset and completion of viral nucleic acid synthesis.
Key findings
- EHV-3 has a short eclipse period of 4 hours with exponential infectious virus formation between 5-10 hours post-infection, reaching 200 plaque-forming units per cell by 10-12 hours
- Infection causes rapid suppression of host DNA synthesis to 10% and RNA synthesis to 30% of uninfected cell levels within 2 hours
- Viral DNA and RNA synthesis both begin by 2 hours post-infection and reach maximum levels between 4-7 hours, preceding peak infectious virus production
- Approximately 90% of newly synthesized virus remains cell-associated, with only 10% released into the extracellular medium
- EHV-3 replicates faster than EHV-1 and EHV-2, with earlier kinetics of viral nucleic acid synthesis and infectious particle formation
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Abstract
The kinetics of equine herpesvirus type 3 (EHV-3) multiplication and of the synthesis of EHV-3 specific DNA and RNA were investigated. A one-step growth curve of EHV-3 in equine epithelial cells from a transitional cell carcinoma was characterized by: (1) a short eclipse period (4 h); (2) an exponential increase in infectious virus between 5 and 10 h post-inoculation; and (3) a slow, inefficient release of newly formed virus into the extracellular fluid. Two hours after infection of cells with EHV-3, the rates of incorporation of specific precursors into total cell RNA or DNA were reduced to 30% and 10%, respectively, of that seen in uninfected cells. With the aid of DNA-RNA hybridization and caesium chloride isopycnic centrifugation techniques, the rates of synthesis of EHV-3 specific nucleic acids at different stages of the virus replication cycle were determined. Virus RNA and DNA synthesis was detectable 2 h after infection and reached maximum levels at an interval (4 to 7 h post-inoculation) corresponding to that period of the virus replication cycle just preceding the time of maximal synthesis of infectious virus.
* Present address: Department of Microbiology, University of Mississippi Medical Center, Jackson, Mississippi 39216, U.S.A.