chad petitAssistant Professor

Research Areas
Host-pathogen interactions involving influenza viruses and coronaviruses


 

Research Interests

My research goals are grounded in the use of biomolecular nuclear magnetic resonance (NMR) spectroscopy to define the structural mechanisms that underlie interactions between host and viral proteins. My graduate training in molecular virology (SARS-CoV) combined with my postdoctoral training in NMR spectroscopy makes me suited to integrate structural biology and molecular virology into a cohesive research program. My lab currently uses NMR and other structural techniques combined with molecular virology to mechanistically understand host-pathogen interactions that can be exploited in the development of antivirals. We currently focus on two pathogens that are of high priority to public health, influenza viruses and coronaviruses.

Influenza Viruses

The influenza virus is a serious public health concern causing significant mortality and morbidity worldwide. The annual impact of which is largely determined by each strain’s ability to efficiently be transmitted from one host to another, or transmissibility, and the severity of the disease state caused by the virus, or virulence. While the interactions between viral and host proteins that determine transmissibility have been extensively studied, our understanding of the strain specific interactions that underlie virulence is extremely limited. One protein that facilitates viral evasion of the host immune response, and thus plays a critical role in modulating virulence, is the non-structural protein 1 (NS1). Not only does its absence attenuate influenza infection, certain variants also dramatically enhance virulence. NS1 is also considered to be a high valued target for the development of novel antivirals against influenza infection. Although many cellular proteins that interact with NS1 have been identified, a thorough structural and biophysical analysis of the strain dependent nature of these interactions is lacking. The knowledge gained by answering these questions will not only provide structural and biophysical insight into strain specific interactions that enhance virulence, but it will also guide the development of novel antivirals against influenza infection.

The overall goal of this project is to structurally and biochemically characterize the strain dependence of NS1 function through analysis of naturally occurring mutations in NS1. The rationale that underlies our research is that elucidating structure-function relationships between NS1 and its cellular interaction partners will provide critical insight into how influenza is able to evade the host immune response. To determine the strain dependent aspects of NS1 function, we utilize a number of biophysical methods designed to interrogate the interaction between NS1 and host cell proteins. The primary method we us for determining and characterizing the interaction between NS1 and host proteins is biomolecular NMR. For example, we use an NMR technique known as chemical shift perturbation analysis to map intermolecular interface between NS1 and host cell proteins. Analysis of each interaction includes NS1 proteins derived from multiple strains of influenza to determine their dependence on strain. In addition, using multiple strains identifies naturally occurring mutations that are critical to the interactions being studied. Ultimately, this information will allow us to formulate further experiments using mutant recombinant influenza viruses to determine each naturally occurring mutation’s role in replication, the innate immune response, and pathogenicity.

Coronaviruses

The periodic emergence of novel coronaviruses (CoVs) represents an ongoing public health concern with significant health and financial burden worldwide. The most recent occurrence originated in the city of Wuhan, China where a novel coronavirus (SARS-CoV-2) emerged causing severe respiratory illness and pneumonia (COVID-19). The continual emergence of novel coronaviruses underscores the importance of developing effective vaccines as well as novel therapeutic options that target either viral functions or host factors recruited to support coronavirus replication. The CoV nonstructural protein 1 (nsp1) has been highlighted as a viable target for both antiviral therapy and vaccine development. However, the fundamental molecular and structural mechanisms that underlie nsp1 function remain poorly understood, despite its critical role in the viral lifecycle.

Nsp1 is the N-terminal cleavage product released from the replicase polyprotein by the virally encoded papain-like proteinase (nsp3d; PLpro). It has been shown to promote cellular mRNA degradation, block host cell translation, and inhibit the innate immune response to virus infection. Deletion of the nsp1-coding region in infectious clones prevented the virus from productively infecting cultured cells. Also, mutations preventing the release of nsp1 from the nascent ORF1a polyprotein substantially limited virus viability. While there have been multiple studies on describing nsp1 function, there have been no studies that focus on structurally defining the host-protein interactions that facilitate these functions. These types of studies are needed to fully exploit nsp1 as a target for both the development of antivirals and rational vaccine design and are the focus of this project.

Education

Graduate School
Ph.D., Louisiana State University, Baton Rouge, LA

Contact

Office
Kaul Human Genetics Building
Room 452
720 20thStreet South
Birmingham, AL 35294-0024

Phone
(205) 975-3398

Email
cpetit@uab.edu