Age-dependent resistance of mice to sindbis virus infection: viral replication as a function of host age.
The development of resistance of outbred white mice to two plaque size variants of Sindbis virus was studied as a function of host age. A sudden drop in mortality occurred over a 3-day period. As little as 1 plaque-forming unit (PFU) per mouse was lethal in 1-day-old animals, whereas inocula of 10(9) PFU per mouse failed to produce high mortality in weanlings. A comparison of viral growth kinetics shows that early replication was similar in newborns and weanlings but that after 6 to 8 hr the production rate and, therefore, the maximal viral titer were suppressed in weanlings. The data demonstrate a lethal viral threshold. Titers in excess of this level lead to mortality, whereas those below it allow survival.
Department of Microbiology, The University of Texas at Austin, Austin, Texas 78712.
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Reinarz
M G
MG
Broome
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BP
Sagik