morphosis

Herpes simplex virus is spherical, and the complete virus consists of core, capsid, envelope and envelope. The core contains two DNA strands, which are wound into a filament reel. The capsid is icosahedron, which consists of 162 shell particles with a diameter of 100nm. The outer layer of the capsid is covered with a film with uneven thickness, and the outermost layer is a typical lipid bilayer capsule with protrusions on it. The diameter of enveloped virus is 150 ~ 200 nm. The envelope surface contains glycoproteins such as gb, gC, gD, gE, gG, gH, etc. These glycoproteins are related to the absorption/permeation of virus into cells (gBgCgDge), the control of virus bud release from nuclear membrane (gH) and the induction of cell fusion (gbgCgDgH). It can induce neutralizing antibody (gd is the strongest) and cytotoxicity (all known HSV glycoproteins can be used).

(2) Gene structure

HSV genome is a linear DNA molecule, which consists of a long segment (L) and a short segment (S) connected by valence bonds. Each fragment contains a single sequence and an inverted repeat sequence. There are 72 genes in the genome, and * * * codes for more than 70 different protein. Among them, 18 codes for viral DNA binding proteins and various enzymes, which are involved in viral DNA synthesis, packaging and nucleotide metabolism. More than 30 kinds of protein have formed viral structural proteins (such as capsid proteins and envelope proteins), which play an important role in protecting HSV DNA, and also play a role in inducing HSV pathogenicity and immune response.

(3) Cultivation characteristics

HSV can grow in many kinds of cells, such as BHK cells, Vero cells and Hep-2 cells. When the virus was first isolated, primary newborn rabbit kidney cells and human embryonic lung cells were more sensitive. HSV infects a wide range of animals, many animals can cause herpetic encephalitis, foot pad inoculation in mice can cause fatal infection of central nervous system, corneal inoculation in rabbits can cause herpetic keratitis, and vaginal inoculation in guinea pigs can cause cervicitis and cervical cancer. Inoculated on chick chorioallantoic membrane, forming hyperplastic white plaque.

(4) Typing

There are two serotypes of HSV, namely HSV- 1 and HSV-2. The nucleotide sequences of the two viruses are 5% homologous, and there are * * * identical antigens and specific antigens between the two viruses. Types can be distinguished by ELISA, DNA restriction map analysis and DNA hybridization test with type-specific monoclonal antibodies.

Second, pathogenicity.

Patients and health are the sources of infection, mainly through direct close contact and sexual contact. HSV invades the body through oral cavity, respiratory tract, genital mucosa and damaged skin. Human infection is very common, and the infection rate is 80 ~ 90%. The common clinical manifestation is herpes accumulated in local mucosa or skin, and occasionally serious systemic diseases may occur, involving internal organs.

(1) Primary infection

Within 6 months, most babies get antibodies from their mothers through the placenta. About 90% of the initial infection has no clinical symptoms, and most of them are recessive infections. The first infection of HSV- 1 often occurs at the age of 1 ~ 15. The common infection is gingivitis, which is a cluster of herpes in buccal mucosa and gums. After it burst, it was covered with a layer of necrotic tissue. In addition, it can cause cold sores, eczema-like herpes, herpetic keratitis and herpetic encephalitis. Genital herpes is mostly caused by HSV-2 after 14 years old, which is more serious, with severe local pain, accompanied by fever, general malaise and lymphadenitis.

(2) Latent infection and recurrence

After the primary infection of HSV produces immunity, most viruses are destroyed, and some viruses can reach trigeminal ganglion (HSV- 1) and spinal ganglion (HSV-2) cells or astrocytes around them along the myelin sheath, and persist in a latent state, which is in a relatively balanced state with the body and does not cause clinical symptoms. When the body has fever, cold, sun exposure, menstruation, emotional stress, use of pituitary or adrenocortical hormones, and infection by some bacteria and viruses, the latent virus is activated and proliferated, and it goes down the nerve fiber cord to the sensory nerve endings, and continues to proliferate in nearby epidermal cells, causing local herpes recurrence. Its characteristic is that each recurrence often occurs in the same place. Most commonly, small herpes groups appear at the junction of skin and mucosa between lips and nose. Herpes keratitis and herpetic cervicitis can also recur.

(3) Congenital infection

HSV affects the mitosis of embryonic cells through placental infection, and is prone to congenital diseases such as abortion, fetal malformation and mental retardation. About 40 ~ 60% newborns can be infected when they pass through the birth canal infected by HSV-2, which leads to high fever, dyspnea and central nervous system diseases. Among them, 60 ~ 70% infected newborns can die because of this, and the sequelae of survivors can reach 95%.

(4) Carcinogenic relationship

Some investigations show that HSV- 1 and HSV-2 may be related to lip cancer, vulvar cancer and cervical cancer respectively, especially HSV- 1 as the cause of cervical cancer has been concerned, but recent research shows that human papillomavirus is directly related to this kind of cancer, so the cause of cervical cancer may be complicated.

Third, immunity.

Neutralizing antibodies can appear in the blood about 1 week after the initial infection of HSV, reaching the peak in 3-4 weeks and lasting for many years. Neutralizing antibody can inactivate the virus outside the cell, prevent the virus from spreading through the blood stream and limit the course of disease, but it can't eliminate the latent infection virus and prevent recurrence. Cellular immunity plays a more important role in the body's immunity against HSV infection. NK cells can specifically kill HSV-infected cells. With the participation of antibodies, the mediated ADCC effect can also lyse HSV-infected cells. Cytotoxic T cells and various lymphocyte molecules (such as interferon) are also of great significance in anti-HSV infection.

Fourth, microbial diagnosis.

(A) virus isolation

Susceptible cells were inoculated with saliva, spinal fluid, oral cavity, cervical secretion, vaginal secretion or curettage of cornea and conjunctiva, and cultured for 1 ~ 2 days. The cells swelled, rounded and fused with each other, which can be used for preliminary diagnosis.