Dynamic of replication and tissue tropism in early stages of infection inAndes virus/hamster disease model.

MARTINEZ VALERIA P.; MAIDANA SILVINA S.; PADULA PAULA J.

Ciudad de Buenos Aires. Argentina

Conferencia; VII International Conference on HFRS,HPS and Hantaviruses; 2007

Fundación Mundo Sano

Andes virus (ANDV) is a hantavirus pulmonary syndrome (HPS) agent and one of the most lethal human pathogen. The system ANDV-hamster has been described as a lethal disease model for HPS. The objective of this work was to analyse several parameters in the early phase of infection, before death, using the mentioned system. We evaluated the effect of different viral doses on lethality, survival time and viremia. We also study humoral response, tissue tropism, replicative dynamics and sites of replication. Increasing viral doses had no effect on the severity of illness, lethality almost reach 100% with 5 different doses; hamsters infected with higher viral doses showed shorter survival. High initial viral doses resulted in transient moderate viremia lasting only 1 day, and lower doses in undetectable viremia. IgG response was low and was not detected until day 7 post inoculation (p.i.). To test ANDV tissue tropism and replicative dynamics, 2 hamsters were sacrificed since day 4 to 9 after inoculated with 10000 pfu of ANDV. Virus titration was performed, and viral RNA monitored by RT-PCR and real time RT-PCR. In order to quantify total RNA copy number, real time RT-PCR (TaqManâ technology) was performed. To determine active sites of replication amplification of positive RNA chain was performed as follows: firstly by RT with antisense primer, followed by real time PCR amplification. Infectious particles were detected since day 5 p.i. and real time RT-PCR detected viral genome since day 4  p.i. on  several tissues. RNA viremia was detected since day 5 p.i. reaching the highest level between days 7 and 8 p.i. Active replication was detected mainly in lung and liver. ANDV showed a wide and early distribution pattern throughout several tissues. Although the infection was performed by intramuscular injection, lung seems to be the first active replication site. This early pattern of distribution could be reflecting a marked delay in antiviral defense mechanisms in hamsters caused by ANDV. Citotoxic celular response to widely distributed infected cells could be probably responsible for the abrupt outcome of disease as a consequence of viral clearance, as it was hypothesized for human illness.