Hendra virus (HeV) and Nipah virus (NiV) are henipaviruses discovered in the mid-to late 1990s that possess a broad host tropism and are known to cause severe and often fatal disease in both humans and animals. In 2002, the International Committee on Taxonomy of Viruses (ICTV) classified Hendra and Nipah viruses as a new genus, belonging to the paramyxoviridae family of the order Mononegatives. The number and sequence of genes of Henipa virus (30-N-P-M-F-G-L-50) are similar to those of respiratory virus and measles virus. The six transcription units encode six major structural proteins. Namely nucleocapsid protein (N), phosphoprotein (P) matrix protein (M), fusion (F) protein, glycoprotein (G) and large protein (L) or RNA polymerase. Hendra and Nipah virus genome ends are highly conserved and complementary to other paramyxoviruses. Similar to other viruses of the paramyxovirinae Hendra and Nipah genomes are multiples of six in length. Hendra and Nipah viruses have also been shown to replicate in minigenomes following the 'rule of 6'. The length of the gene comes from the "6-fold rule", and the replication efficiency is often not high. Transcription and replication are templated by Ns, where each nucleoprotein subunit is a 6-nucleotide genomic RNA.The nucleotide and amino acid compositions of Hendra and Nipah viruses have high similarity. The amino acid sequence similarity of the N, P and L proteins of Hendra and Nipah viruses was 92%, 71%, and 87%, respectively. Overall, these viruses share a higher level of nucleotide similarity in their genes in their protein-coding regions (70%-80%) than in their 50- and 30-UTR (untranslated) regions (40%-67%) . However, the leading and terminal sequences of the genomes have 80% and 90% similarity, respectively.

Glycoprotein G（O89343/Q9IH62）

Interacts with host ephrinB2/EFNB2 or ephrin B3/EFNB3 to provide virion attachment to target cell. This attachment induces virion internalization predominantly through clathrin-mediated endocytosis

RNA-directed RNA polymerase L（O89344/Q997F0）

RNA-directed RNA polymerase that catalyzes the transcription of viral mRNAs, their capping and polyadenylation. The template is composed of the viral RNA tightly encapsidated by the nucleoprotein (N). The viral polymerase binds to the genomic RNA at the 3' leader promoter, and transcribes subsequently all viral mRNAs with a decreasing efficiency. The first gene is the most transcribed, and the last the least transcribed. The viral phosphoprotein acts as a processivity factor. Capping is concommitant with initiation of mRNA transcription. Indeed, a GDP polyribonucleotidyl transferase (PRNTase) adds the cap structure when the nascent RNA chain length has reached few nucleotides. Ribose 2'-O methylation of viral mRNA cap precedes and facilitates subsequent guanine-N-7 methylation, both activities being carried by the viral polymerase. Polyadenylation of mRNAs occur by a stuttering mechanism at a slipery stop site present at the end viral genes. After finishing transcription of a mRNA, the polymerase can resume transcription of the downstream gene.

Fusion glycoprotein F0（O89342/Q9IH63）

Class I viral fusion protein. Under the current model, the protein has at least 3 conformational states: pre-fusion native state, pre-hairpin intermediate state, and post-fusion hairpin state. During viral and plasma cell membrane fusion, the heptad repeat (HR) regions assume a trimer-of-hairpins structure, positioning the fusion peptide in close proximity to the C-terminal region of the ectodomain. The formation of this structure appears to drive apposition and subsequent fusion of viral and plasma cell membranes. Directs fusion of viral and cellular membranes leading to delivery of the nucleocapsid into the cytoplasm. This fusion is pH independent and occurs directly at the outer cell membrane. The trimer of F1-F2 (F protein) probably interacts with G at the virion surface. Upon G binding to its cellular receptor, the hydrophobic fusion peptide is unmasked and interacts with the cellular membrane, inducing the fusion between cell and virion membranes. Later in infection, F proteins expressed at the plasma membrane of infected cells could mediate fusion with adjacent cells to form syncytia, a cytopathic effect that could lead to tissue necrosis

Matrix protein（O89341/Q9IK90）

Plays a crucial role in virion assembly and budding. Forms a shell at the inner face of the plasma membrane,Transits through the host nucleus before gaining the functional ability to localize and bud from the plasma membrane.Mediates together with fusion protein the incorporation of the glycoprotein to the viral particles.Participates also in the inhibition of the host interferon type I antiviral response by interacting with and thereby inhibiting host TRIM6 

Phosphoprotein(O55778/Q9IK91)

Essential component of the RNA polymerase transcription and replication complex. Binds the viral ribonucleocapsid and positions the L polymerase on the template (By similarity).

May play a role to prevent the establishment of cellular antiviral state by binding to host STAT1 in the cytoplasm. This activity is not as strong as that of V and W.

Nucleoprotein(O89339/Q9IK92)

Encapsidates the genome protecting it from nucleases. The encapsidated genomic RNA is termed the nucleocapsid (NC) and serves as template for transcription and replication (By similarity).

References

Hendra virus. PMID: 21895580
Nipah Virus Infection. PMID: 29643201
Hendra Virus Infection in Horses: A Review on Emerging Mystery Paramyxovirus. PMID: 32684248
Hendra virus: what do we know? PMID: 21781619
Hendra virus ecology and transmission. PMID: 26978066
Hendra virus: to vaccinate or not to vaccinate? What is the alternative? PMID: 33258486
Emerging trends of Nipah virus: A review. PMID: 30251294
Hendra virus: Epidemiology dynamics in relation to climate change, diagnostic tests and control measures. PMID: 33363250
Hendra virus: an emerging paramyxovirus in Australia. PMID: 22921953

Nipah Virus Infection. PMID: 31313551
Nipah Virus: Past Outbreaks and Future Containment. PMID: 32325930
Nipah virus infection: A review. PMID: 30869046
Emerging trends of Nipah virus: A review. PMID: 30251294
Nipah virus: epidemiology, pathology, immunobiology and advances in diagnosis, vaccine designing and control strategies - a comprehensive review. PMID: 31006350
Lessons from the Nipah virus outbreak in Malaysia. PMID: 19108397
Nipah virus dynamics in bats and implications for spillover to humans. PMID: 33139552