Jilbert A R, Miller D S, Scougall C A, Turnbull H, Burrell C J
Infectious Diseases Laboratories, Institute of Medical and Veterinary Science, Adelaide, South Australia.
Virology. 1996 Dec 15;226(2):338-45. doi: 10.1006/viro.1996.0661.
Using pooled serum from congenitally duck hepatitis B virus (DHBV)-infected ducks as inoculum, we examined the effect of virus dose on the incubation period of infection and on the patterns of spread of virus infection in the liver. The pooled serum inoculum contained 9.5 x 10(9) DHBV genomes per milliliter and had an infectivity titre (ID50) in newly hatched ducks of 1.5 x 10(10) per milliliter with a 95% confidence interval of 3.0 x 10(9) to 6.3 x 10(10) ID50/ml, indicating the equivalence between one DHBV genome and one infectious unit within the limits of the assays. The incubation period of infection was inversely related to the dose of inoculum and the onset of viraemia ranged from Day 6 with the highest dose to Day 14 or 29 with the lowest dose inoculum. To study the spread of virus infection from a low percentage of initially infected cells we inoculated newly hatched ducks intravenously with sufficient DHBV (1.5 x 10(3) ID50) to infect only approximately 0.0001% of total liver cells. DHBV infection first reached detectable levels on Day 4 postinoculation (p.i.) and was detected in approximately 0.035% of hepatocytes, most of which occurred as single cells or pairs of cells, indicating that a number of rounds of infection had occurred with the spread of virus both to adjoining cells, i.e., by cell-to-cell spread, and to cells located in other parts of the liver lobule. Despite some bird-to-bird variation in timing, the percentage of infected hepatocytes increased exponentially with a mean doubling time of 16 hr from Day 4 to Day 14 p.i., by which time replication was seen in > 95% of hepatocytes. This rapid dissemination from a small number of infected hepatocytes suggests that, in neonatal ducks, there are no major delays in virus replication within the liver, that any innate and adaptive defence mechanisms operating during the first 10 to 14 days of infection are insufficient to contain virus spread, and that even a small number of infected hepatocytes produce enough progeny to rapidly infect the remaining hepatocytes.
我们使用来自先天性感染鸭乙型肝炎病毒（DHBV）的鸭子的混合血清作为接种物，研究了病毒剂量对感染潜伏期以及肝脏中病毒感染传播模式的影响。该混合血清接种物每毫升含有9.5×10⁹个DHBV基因组，在新孵出的鸭子中的感染性滴度（ID50）为每毫升1.5×10¹⁰，95%置信区间为3.0×10⁹至6.3×10¹⁰ ID50/ml，表明在测定范围内一个DHBV基因组与一个感染单位等效。感染潜伏期与接种物剂量呈负相关，病毒血症的发作时间从高剂量接种时的第6天到低剂量接种物时的第14天或第29天不等。为了研究从低比例初始感染细胞开始的病毒感染传播，我们给新孵出的鸭子静脉注射足够的DHBV（1.5×10³ ID50），仅感染约0.0001%的肝脏细胞总数。DHBV感染在接种后（p.i.）第4天首次达到可检测水平，并在约0.035%的肝细胞中检测到，其中大多数以单个细胞或成对细胞形式出现，这表明随着病毒向相邻细胞传播，即通过细胞间传播，以及向位于肝小叶其他部位的细胞传播，发生了多轮感染。尽管不同鸟类在时间上存在一些差异，但从接种后第4天到第14天，感染肝细胞的百分比呈指数增长，平均倍增时间为16小时，到那时在>95%的肝细胞中可见复制。这种从少数感染肝细胞迅速传播表明，在新生鸭中，肝脏内病毒复制没有重大延迟，在感染的前10至14天起作用的任何先天和适应性防御机制都不足以遏制病毒传播，而且即使少数感染肝细胞也能产生足够的子代来迅速感染其余肝细胞。
