Viral Infection Detection

Viral Infection DetectionClinical examinations & findings

Antibody detection

Electron Microscopic: SEM & TEM

Molecular assays: PCR

Detection of viral receptors

Example: Hemagglutination & Hemagglutination inhibition

Culture

Plaque formation (PFU, Pock)

The Culture of Viruses

1. laboratory animals

2. Embryonated eggs

3. Cell lines (Tissue cultures)

Primary cell culture

Diploid cell lines

Continuous cell lines

Cytopatic effects (CPEs)

Cytopatic effects (CPEs):

Cell lyses (degeneration) Aggregation Malignant transformation Giant cells Cell rounding Viral gene expression Loss of attachment (to culture dish) Cell-Cell fusion (Syncytial cells) Inclusion body: Negri body

Rabies Negri bodies

Syncytial cells by Respiratory syncytial virus (RSV)

herpes simplex virus (HSV) type 1-infected primary rabbit kidney cellsCPE: rounding and detachment of cells

Adenovirus beta galactosidase

Viral genetics

Virus - Virus interactions

Viral cancers

Different interactions between two different viruses in a cell

Recombination (based on Crossing over)

- between HSV1 & HSV2

Reassortment

- between Influenza viruses

Complementation

- Rescue of a lethal mutant with a defined genetic sequence of other virus

Transcapsidation

- Pseudoviruses

Cell transformationChanges in cellular growth, cellular morphology, antigenic compounds.

Oncogenic viruses can be carcinogen (causing malignant tumors) and make cells to transform.

Tumor viruses

Why some viruses are considered the causative of tumors?- Biological criteria for causal association of viruses with

tumors:

The presence of virus in tumor tissues

The presence of virus before disease onset

Viral persistence

The location of virus at appropriate sites

Prevention of the disease by prevention of viral infection

Human Oncogenic virusesHuman Oncogenic RNA viruses Retroviruses: HTLV-1 & HTLV-2, HIV: Kaposi’s sarcoma

Human Oncogenic DNA viruses Human Hepatitis B virus: Hepatocellular carcinoma Herpesviruses: Epstein-Barr virus: Burkitt’s Lymphoma/

Epstein-Barr virus: Nasopharyngeal Carcinoma Herpesviruses: Herpes Simplex virus Type 2: Cervical

intraepithelial neoplasia Herpesviruses: Human Cytomegalovirus: Cervical tumors/ Human Papillomaviruses: types 18, 16, 33: Cervical cancer

Viral and hast genes involved in cancers

Virus:

Promoter genes (viral oncogenes= v-onc )

Host:

Tumor Repressor Genes

Oncogenes (cellular oncogenes= c-onc)

Tumor Repressor Genes (Anti-oncogenes)

They are normally oncogene regulators.

If repressed (e.i. by a virus promoter)

Activating the relevant oncogene Causing oncogene products Cell transformation

Cellular Oncogenes(c-onc genes)

Normally inactivated.

If disregulated or mutated, then causes transformation in the cell by oncogene products.

Example:

Retinoblastoma (Rb) gene is one of these tumor repressor genes which regulates the pass of the cells to S stage of the cell cycle. Mutation of Rb gene by some viral promotors transforms the cell.

Growth factors

Signaling proteins

DNA binding proteins and other regulatory proteins

Cellular receptors