New Trends in the Pandemic Battle: The Introduction of KP.2 Protein Raw Materials

Since 2020, the COVID-19 pandemic has emerged as one of the most severe global public health crises of the 21st century. It has not only caused widespread loss of life and health issues globally but has also triggered economic recessions, labor market instability, and mental health crises.

Figure 1: Structure of SARS-CoV-2

The SARS-CoV-2 viral particle is spherical or elliptical in shape and primarily consists of the spike glycoprotein (S), nucleocapsid (N), membrane glycoprotein (M), envelope protein (E), and RNA genome. The membrane glycoprotein and envelope protein are associated with the virus's morphological functions, assembly, and release.

The S protein, N protein, and receptor-binding domain (RBD) are critical components of the virus, playing significant roles in the virus's infection mechanism, immune response, and vaccine development.

Figure 2: Structure of the Spike Glycoprotein

The S protein is composed of two subunits, S1 and S2. The S1 subunit contains the RBD, which is responsible for binding to the ACE2 receptor on the surface of host cells, while the S2 subunit is involved in the fusion process of the virus with the host cell membrane. The RBD region of the S protein determines the virus's specificity and infectivity towards host cells.

The N protein binds to the RNA genome in a bead-like manner, forming a helically symmetrical nucleocapsid structure. It interacts with the viral RNA to form ribonucleoprotein complexes (RNPs), which are the core of the virus. The N protein plays a crucial role in the virus's replication and transcription processes and is involved in the virus's assembly. It is also a potential target for vaccine design and drug development.

Viral Evolution

As the virus continues to mutate, new variants emerge. The evolution of the virus can lead to new strains with higher escape capabilities, increased transmissibility, or potentially more severe disease risks. Facing these challenges, we must respond rapidly, continuously monitoring viral mutations and treatment methods.

Figure 3: Schematic Diagram of the Main Evolutionary Relationships of the COVID-19 Genome

KP.2

KP.2 (JN.1.11.1.2) is a third-generation sublineage of the Omicron JN.1 variant and one of the sublineages with a strong transmission advantage within the JN.1 variant. KP.2 has three new mutation sites, two of which are on the S protein.

KP.2 exhibits higher viral fitness and may become the dominant lineage worldwide. According to genomic surveillance data, the relative effective reproduction number (Re) of KP.2 in the USA, UK, and Canada is 1.22, 1.32, and 1.26 times that of JN.1, respectively. As of April 2024, the estimated mutation frequency of KP.2 in the UK has reached 20%. Neutralization assays using BXX1.5 vaccine sera and sera from patients with breakthrough infections of XBB.1.5, EG.5, HK.3, and JN.1 have shown that KP.2 has a significantly higher escape capability than JN.1. On May 3, WHO classified KP.2 as a "variant under monitoring."

In addition to KP.2, other notable variants include BA.2.75, BA.4, BA.5, XBB, and JN.1. BA.2.75 has multiple key mutations in the S protein, particularly in the receptor-binding domain (RBD), which confer higher ACE2 binding affinity. BA.4 and BA.5, known for their high escape characteristics, have become the dominant strains in multiple regions. XBB is a unique sublineage of the Omicron variant, classified as a recombinant variant, potentially formed by the combination of genetic material from two or more viral strains. JN.1, a novel variant of BA.2.86, inherits the antigenic diversity of BA.2.86 and an additional L455S mutation, which may enhance immune evasion by reducing ACE2 binding. WHO has also classified JN.1 as a "variant of interest."

S-RMab® Protein

Starter has been closely monitoring viral evolution and has introduced nearly 40 new COVID-19 proteins and antibodies, covering prevalent strains such as KP.2, JN.1, and XBB, providing core materials for COVID-19 research.