Vector-Borne Transmission Imposes a Severe Bottleneck on an RNA Virus Population

PLoS Pathogens

Naomi L. Forrester¹  Robert L. Seymour¹  Scott C. Weaver¹  Mathilde Guerbois¹  Heidi Spratt² 

[1] Institute for Human Infections and Immunity, Center for Biodefense and Emerging Infectious Diseases and Department of Pathology, University of Texas Medical Branch, Galveston, Texas, United States of America;Sealy Center for Preventative Medicine and Preventative Medicine and Community Health, University of Texas Medical Branch, Galveston, Texas, United States of America

关键词: Cloning;    Mosquitoes;    Arboviral infections;    Saliva;    Vector-borne diseases;    Reverse transcriptase-polymerase chain reaction;    Arboviruses;    Population genetics;   

DOI  :  10.1371/journal.ppat.1002897

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

RNA viruses typically occur in genetically diverse populations due to their error-prone genome replication. Genetic diversity is thought to be important in allowing RNA viruses to explore sequence space, facilitating adaptation to changing environments and hosts. Some arboviruses that infect both a mosquito vector and a mammalian host are known to experience population bottlenecks in their vectors, which may constrain their genetic diversity and could potentially lead to extinction events via Muller's ratchet. To examine this potential challenge of bottlenecks for arbovirus perpetuation, we studied Venezuelan equine encephalitis virus (VEEV) enzootic subtype IE and its natural vector Culex (Melanoconion) taeniopus, as an example of a virus-vector interaction with a long evolutionary history. Using a mixture of marked VEEV clones to infect C. taeniopus and real-time RT-PCR to track these clones during mosquito infection and dissemination, we observed severe bottleneck events that resulted in a significant drop in the number of clones present. At higher initial doses, the midgut was readily infected and there was a severe bottleneck at the midgut escape. Following a lower initial dose, the major bottleneck occurred at initial midgut infection. A second, less severe bottleneck was identified at the salivary gland infection stage following intrathoracic inoculation. Our results suggest that VEEV consistently encounters bottlenecks during infection, dissemination and transmission by its natural enzootic vector. The potential impacts of these bottlenecks on viral fitness and transmission, and the viral mechanisms that prevent genetic drift leading to extinction, deserve further study.

【 授权许可】

CC BY