Since the recent outbreak of COVID-19, there have been intense efforts to understand
viral pathogenesis and host immune response to combat SARS-CoV-2. It has become evident
that different host alterations can be identified in SARS-CoV-2 infection based on
whether infected cells, animal models or clinical samples are studied. Although
nasopharyngeal swabs are routinely collected for SARS-CoV-2 detection by RT-PCR testing,
host alterations in the nasopharynx at the proteomic level have not been systematically
investigated. Thus, we sought to characterize the host response through global proteome
profiling of nasopharyngeal swab specimens. A mass spectrometer combining trapped ion
mobility spectrometry (TIMS) and high-resolution QTOF mass spectrometer with parallel
accumulation-serial fragmentation (PASEF) was deployed for unbiased proteome profiling.
First, deep proteome profiling of pooled nasopharyngeal swab samples was performed in
the PASEF enabled DDA mode, which identified 7723 proteins that were then used to
generate a spectral library. This approach provided peptide level evidence of five
missing proteins for which MS/MS spectrum and mobilograms were validated with synthetic
peptides. Subsequently, quantitative proteomic profiling was carried out for 90
individual nasopharyngeal swab samples (45 positive and 45 negative) in DIA combined
with PASEF, termed as diaPASEF mode, which resulted in a total of 5023 protein
identifications. Of these, 577 proteins were found to be upregulated in SARS-CoV-2
positive samples. Functional analysis of these upregulated proteins revealed alterations
in several biological processes including innate immune response, viral protein
assembly, and exocytosis. To the best of our knowledge, this study is the first to
deploy diaPASEF for quantitative proteomic profiling of clinical samples and shows the
feasibility of adopting such an approach to understand mechanisms and pathways altered
in diseases.