The above data suggest that following a breakthrough infection of Omicron, the neutralizing capacity of serum for BA.4/5 is reduced compared to BA.1. 1.5.3.4. and the evasion strategies employed by SARS-CoV-2 variants will improve our capacity to combat newly emerging Omicron variants. Keywords: SARS-CoV-2, Omicron, Immune evasion, Mutations, Booster, Bivalent mRNA vaccine Graphical Abstract Open in a separate window 1.?Introduction 1.1. Zoonotic coronaviruses and human pathogenic coronavirus Zoonotic coronaviruses (CoV) are a large group of pathogens that often infect humans or animals to cause severe (R)-Oxiracetam diseases, which potentially threaten public health and interpersonal development [1], [2]. In 1965, Tyrrell and Bynoe isolated the first human coronavirus, named B814, from your nasal wash of a chilly patient using a human embryo tracheal culture [3]. Electron microscopy revealed that there are spinous processes shaped like coronas on their envelopes, hence the name coronavirus was proposed [4]. Coronavirus can be classified into 4 different genera by the International Committee of Taxonomy of Viruses (ICTV), namely Alpha-, Beta-, Gamma-, and Delta-coronaviruses [5]. Alpha- and Beta-coronaviruses infect mammals only, whereas Gamma- and Delta-coronaviruses infect birds and occasionally also infect mammals [5]. Currently, 7 coronaviruses are known to be capable of infecting humans [6]. SARS-CoV-2 is the 7th coronavirus with a confirmed ability to infect humans and can cause mild to severe disease depending on pathogenicity, infectivity, and subvariants [5], [6], [7], [8], [9], [10]. Of these 7 coronaviruses, HCoV-229E and HCoV-NL63 are in the Alpha-coronavirus, while SARS-CoV, SARS-CoV-2, HCoV-HKU1, HCoV-OC43, and MERS-CoV are all in the Beta-coronaviruses [5], [11]. The genera of Beta-coronavirus can further be divided into subgroups based on their genomic structures and phylogenetic associations [5]. HCoV-OC43 and HCoV-HKU1 belong to subgroup A, SARS-CoV, SARS-CoV-2 to subgroup B, and MERS-CoV to subgroup C [5], [11] ( Fig. 1). HCoV-229E, HCoV-NL63, HCoV-HKU1, and HCoV-OC43 cause (R)-Oxiracetam humans to develop moderate upper respiratory symptoms and are commonly referred to as common chilly CoVs [5], [6], [7], [8], [9], [10]. The human lower respiratory tract can be infected by SARS-CoV and MERS-CoV, leading to severe respiratory disease [5], [6], [7], [8], [9], [10]. Open in a separate windows Fig. 1 Classification of the Coronaviridae. The Coronaviridae family has been divided (R)-Oxiracetam into Orthocoronavirnae and Torovirinae subfamilies. The subfamily Orthocoronavirnae is usually divided into 4 genera, Alpha-, Beta-, Gamma-, and Delta-coronavirus. Viruses in the Alpha-genus are represented in blue and the Beta-genus are represented in orange. Viruses in the Beta-genus are divided into 4 subgroups A, B, C, and D, with subgroup A, represented in light green, subgroup B in orange, subgroup C in lavender, and subgroup D in light yellow. SARS-CoV-2 belongs to subgroup B in the genus Beta-coronavirus. The Variants of issues of SARS-CoV-2 are represented in yellow, and Omicron subvariants are represented in purple. 1.2. Genome structure, hosts, symptoms, and transmission routes of SARS-CoV-2 SARS-CoV-2 is usually a single-stranded RNA computer virus with about 30?kb long genome [12]. Its genome encodes 4 structural proteins called membrane (M), envelope (E), nucleocapsid (N), and spike (S) plus 16 nonstructural proteins and 9 accessory proteins [12] ( Fig. 2). SARS-CoV isolated from your 2003 pandemic was found to spread from bats to an intermediate host, the civet, which subsequently infected humans [6]. MERS-CoV, which caused Middle East Respiratory Syndrome (MERS) in 2012, was transmitted from bats to dromedary camels before infecting humans [6]. Analogous to SARS-CoV and MERS-CoV, bats are considered to be natural hosts for SARS-CoV-2 [13]. However, the intermediate host of SARS-CoV-2 remains undetermined [13]. When infected by SARS-CoV-2, the most common COVID-19 symptoms in humans are fever, cough, myalgia, and tiredness [6], [12], [14], [15], [16]. More than half of the patients developed dyspnoea [6], [12], [17], [18]. In addition to respiratory symptoms, some patients may also develop gastrointestinal symptoms including diarrhea, vomiting, and abdominal pain [14]. How SARS-CoV-2 transmits Rabbit Polyclonal to APOL1 among individuals is a major concern. It can spread through respiratory droplets, aerosols, contact transmission, and fecal-oral routes [19], [20], [21]. There is even evidence that SARS-CoV-2 can be transmitted from mothers to their offspring in a vertical manner during pregnancy and childbirth [22], [23], [24]. Open in a separate windows Fig. 2 Overview of the SARS-CoV-2 genome encoding nonstructural proteins, structural proteins, and accessory proteins. Nonstructural proteins include ORF1a (NSP 1C11) and ORF1b (NSP 12C16). Structural proteins include membrane (M), envelope (E), nucleocapsid (N), and (R)-Oxiracetam spike (S). Accessory proteins include ORF3a, ORF3b, ORF6, ORF7a, ORF7b, ORF8, ORF9b, ORF9c, and ORF10..