Human coronaviruses: Clinical features and phylogenetic analysis

Abstract

Strains of human coronavirus (HCoV), namely HCoV-OC43, HCoV-229E, HCoV-NL63, and HCoV-HKU1, primarily infect the upper respiratory and gastrointestinal tracts and are the most common cause of non-rhinovirus-induced common cold in humans. Although the manifestations of coronavirus infection (i.e., rhinorrhea, sneezing, cough, nasal obstruction, and bronchitis) are generally self-limiting in healthy adults, certain strains such as HCoV-NL63 and HCoV-HKU1 can cause severe lower respiratory tract infection and febrile seizure, especially in infants, people of advanced age, and immunocompromised hosts. In 2003, a novel HCoV strain was identified as the causative agent of the severe acute respiratory syndrome (SARS) epidemic that began in Asia in 2002. The strain has hence been referred to as SARS-CoV. In addition, as recently as September 2012, another novel HCoV, human betacoronavirus 2c EMC2012, was identified as being the cause of fever, renal failure, pneumonia, and severe respiratory distress in two patients in the Middle East. Phylogenetic analysis has revealed highly conserved sequences of ORF1ab, spike, nucleocapsid, and envelope protein genes, but not membrane protein genes, between human betacoronavirus 2c EMC2012 and SARS-CoV. This review focuses on the differences in the genomes of certain HCoV strains, the pathogenesis of said strains, and recent developments in the establishment of therapeutic agents that might aid in the treatment of patients with such infections.

Keywords: human betacoronavirus 2c EMC2012; human coronavirus; phylogenetic tree; severe acute respiratory syndrome coronavirus (SARS-CoV).

Fig. 1

Coronavirus genome. ORF1a and 1b are located at the 5'-terminal 2/3 gene of the coronavirus and encode two polyproteins, namely pp1a (∼450 kDa) and pp1ab (∼750 kDa). The four structural proteins in coronavirus include the spike (S) protein, envelope (E) protein, membrane (M) protein, and nuclepcapsid (N) protein.

Fig. 2

Phylogenetic trees. Phylogenetic trees were constructed with (A) ORF1ab, (B) nucleocapsid, (C) membrane, (D) spike, and (E) envelope protein. The phylogenetic trees were constructed using MEGA5 software , , , .