Category Archives: Structure of Virus

Measles virus: structure, pathogenesis, clinical feature, complications and lab diagnosis

  • Measles (Also called Rubeola) is usually a disease of childhood and is followed by life-long immunity.
  • Important cause of childhood mortality in developing countries.

    Kopliks spot

    Koplik’s spot is the major diagnostic criteria for Measles
    Source: CDC

  • Human is the natural host

Structure of Measles Virus

  • Measles virus is a member of the genus Morbillivirus of the family Paramyxoviridae
  • Measles) virus is a typical paramyxovirus (spherical enveloped particles that contain a non segmented negative strand RNA genome)
  • Measles virus have two types of envelope spikes that shows:

Structure clinical feature and Lab diagnosis of Herpes Simplex Virus

Herpes Simplex viruses are members of the Alphaherpesvirinae subfamily of human herpesviruses together with varizella-zoster virus, also called human herpesvirus. HSV is a large virus with a core containing double-stranded DNA within a coat, an icosahedron with 162 capsomeres. The envelope which surrounds the ‘naked’ particle is partly nuclear membrane derived, partly virally coded, with glycoprotein spikes. The diameter of a complete particle is 120–200 nm. The ‘naked’ virion measures about 100 nm.

The virus enters the cells through cellular membrane fusion after being attached to specific receptors through an envelope glycoprotein. The capsid is transported to nuclear pores where DNA circularizes after uncoating, and enters the nucleus. The genome is a 120–230 kbp double-stranded, linear DNA with repeated sequences located at each flank and certain other regions. Genomic rearrangements giving genomic ‘isomers’ may occur, but the biological significance of this is unknown. HSV1 and HSV2 show 50% sequence homology.

Describe the structure of HIV Virus

HIV is a complex RNA virus of the genus Lentivirus within the Retroviridae family. The virus is an approximately 100nm icosahedral structure with 72 external spikes that are formed by the two major envelope glycoproteins gp120 and gp41.
Structure of HIV Virus: Cross-Section

Human Immuno Deficiency Virus (HIV VIRUS)

Human Immunodeficiency Virus (HIV) Virus is the cause of acquired immunodeficiency syndrome (AIDS). Both HIV-1 and HIV-2 cause AIDS, but HIV-1 is found worldwide, whereas HIV-2 is found primarily in West Africa.
Viron: spherical, 80-100 nm diameter, cylindric, core (ribonucleoprotein)
Genome: ss RNA, linear, diploid, 9-10kb, +ve sense.
Proteins: RT, Env gp, protease
Envelope: present, acquired from the host cell membrane when budding out of cell.
·        non- oncogenic, may be cytocidal, provirus remain permanently associated with cells.

Influenza Virus, Structure, Replication and Pathogenesis

ORTHOMYXOVIRUSES ( INFLUENZA VIRUSES)
-         affinity of the viruses to mucins ( myxa: mucus)
-         4 genera: influenza A, B, C viruses and thogotoviruses
-         Mutability and high frequency of genetic reassortment.
resultant antigenic changes in viral surface gp.
-         Influenza type A antigenically highly variable and responsible for most cases of epidemic influenza.
Structure / composition
-         virion spherical, pleomorphic (80-120 nm diameter), helical nucleocapsid (9m) SS RNA, (-) sense (13.6 kb genome size) of A and B viruses with and separate segments; infection C → 7 segments lacking neuraminidase gene.
-         Segment
1→ PB2                   4→HA             7→M1 and M2
      2→PB1                        5→NP             8→NS1 and NS2
      3→PA                   6→NA

Schematic representation of Influenza Virus Structure