Toward the Rational Design of Better Antivirals: The Development of cGAMP as an HIV-1 Anti-Retroviral and the Genetic Surveillance of WNV Evolution

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2017-04-17

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Aroh, Chukwuemika Nnabuike

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Abstract

The innate immune response is the first line of defense against pathogens and thus represents the first hurdle viruses must overcome to cause severe disease in humans. Understanding the consequences of viral evolution can give insights to mechanisms of viral pathogenesis as well as the development of novel therapeutics. Here I studied two clinically important viruses: Human Immunodeficiency Virus (HIV) and West Nile Virus (WNV). HIV-1 has evolved several mechanisms to evade immune detection by the cGAS-STING cytosolic DNA sensing pathway. A small cyclic di-nucleotide, cGAMP, activates the same pathway by directly binding STING. Treatment with cGAMP, delivered by ultra-pH sensitive nanoparticles or by liposomes, in human peripheral blood mononuclear cells (PBMCs) induced potent and long-acting protection against replication of several laboratory-adapted and clinical HIV-1 isolates in contrast to the short-lasting effect of current anti-retroviral therapy (ARTs). These results present the first evidence for potentially developing cGAMP or other STING agonists as a long-acting antiretroviral immunotherapy. West Nile Virus (WNV) is a mosquito-borne Flavivirus which was introduced to North America in 1999 and is currently the leading cause of viral encephalitis. The lack of specific therapeutics or human vaccines makes WNV an ongoing public health threat. Now endemic, WNV is steadily evolving, but the contribution of positively-selected mutations to human disease remains unclear. In 2012 the second largest outbreak of human West Nile disease occurred in the U.S., with one-third of the cases happening in Texas. The outbreak was associated with groups of WNV carrying positively-selected mutations. By sequencing WNV in Texas from 2012-2015, we show that positively-selected mutations in WNV mediate increased circulation and over-wintering in the environment, which may promote increases of human disease. Additionally, we show evidence that the WNV population is still evolving new alleles. These results advance our understanding of the impact of WNV evolution to human disease, and may afford insights to the evolution of other invading flaviviruses, such as Dengue and Zika virus. Altogether, these results show that understanding the consequences of viral evolution can be harnessed towards overcoming challenges to the development of more effective therapeutics.

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