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Newly emerging viral pathogens pose a constant and unpredictable threat to human and animal health. Coronaviruses (CoVs) have a penchant for sudden emergence, as evidenced by severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome CoV (MERS-CoV) and most recently, swine acute diarrhea syndrome coronavirus (SADS-CoV). Small animal models of emerging viral pathogenesis are crucial to better understand the virus and host factors driving disease progression. However, rodent models are often criticized for their limited translatability to humans. The complete blood count is the most ordered clinical test in the United States serving as the cornerstone of clinical medicine and differential diagnosis. We recently generated a mouse model for MERS-CoV pathogenesis through the humanization of the orthologous entry receptor dipeptidyl peptidase 4 (DPP4). To increase the translatability of this model, we validated and established the use of an automated veterinary hematology analyzer (VetScan HM5) at biosafety level 3 for analysis of peripheral blood. MERS-CoV lung titer peaked 2 days post infection concurrent with lymphopenia and neutrophilia in peripheral blood, two phenomena also observed in MERS-CoV infection of humans. The fluctuations in leukocyte populations measured by Vetscan HM5 were corroborated by standard flow cytometry, thus confirming the utility of this approach. Comparing a sublethal and lethal dose of MERS-CoV in mice, analysis of daily blood draws demonstrates a dose dependent modulation of leukocytes. Major leukocyte populations were modulated before weight loss was observed. Importantly, neutrophil counts on 1dpi were predictive of disease severity with a lethal dose of MERS-CoV highlighting the predictive value of hematology in this model. Taken together, the inclusion of hematological measures in mouse models of emerging viral pathogenesis increases their translatability and should elevate the preclinical evaluation of MERS-CoV therapeutics and vaccines to better mirror the complexity of the human condition. [ABSTRACT FROM AUTHOR]

Middle East respiratory syndrome coronavirus (MERS-CoV) causes an acute and severe lower respiratory illness as well as vomiting, diarrhea, and renal failure. Because no licensed MERS-CoV vaccines are currently available, preventive and therapeutic measures are urgently needed. The surface spike (S) glycoprotein of MERS-CoV, which binds to the cellular receptor dipeptidyl peptidase 4 (DPP4), is considered as a major target for MERS-CoV vaccine development. Here, we designed recombinant replication-deficient adenovirus-based vaccines expressing the N-terminal domain (rAd/NTD) and receptor-binding domain (rAd/RBD) of the MERS-CoV S1 subunit and full-length Spike protein (rAd/Spike). We found that immunization with candidate vaccines via intranasal route induced S1-specific IgG antibodies and neutralizing antibodies against MERS spike pseudotyped virus. Especially, rAd/Spike induced the highest neutralizing antibody titer and the strongest cytokine-induced T cell responses among the three candidate vaccines. To compare the immune responses induced by different administration routes, rAd/Spike was administered via intranasal, sublingual, or intramuscular route. All these administration routes exhibited neutralizing effects in the serum. MERS-CoV-specific neutralizing IgA antibodies in the bronchoalveolar lavage fluid were only induced by intranasal and sublingual administration but not by intramuscular administration. Intranasal administration with rAd/Spike also created resident memory CD8 T cells in the airway and lung parenchyma. Taken together, our results showed that both the humoral and cellular immune responses are highly induced by rAd/Spike administration, suggesting that rAd/Spike may confer protection against MERS-CoV infection. [ABSTRACT FROM AUTHOR]