Tag: infectious diseases

• A retrovirus is a type of RNA virus that inserts a copy of its genome into the DNA of a host cell that it invades, thus changing the genome of that cell. 
• Such viruses are either single-stranded RNA (e.g. HIV) or double-stranded DNA (e.g. Hepatitis B virus) viruses.
•  In most viruses, DNA is transcribed into RNA, and then RNA is translated into protein.
•  However, retroviruses function differently, as their RNA is reverse-transcribed into DNA, which is integrated into the host cell's genome (when it becomes a provirus), and then undergoes the usual transcription and translational processes to express the genes carried by the virus. Hence, HIV belongs to the retrovirus group.

AIDS is a viral disease transmitted through certain body fluids such as semen, saliva, blood, the breast milk of an AIDS infected person by sexual contact,  breastfeeding from HIV-infected mother can transmit AIDS to the baby and by blood transfusion. During hug, no body fluid is entered into the body from one person to another. Thus, the correct answer is option B.

AIDS (Acquired immunodeficiency syndrome) is an infection which is caused by Human immunodeficiency virus (HIV). The causative agent of the disease is a virus and so the disease can spread from one person to the other by sexual contact. The disease also spreads through the use of the infected needles, syringes and blood transfusion from the infected person.

HIV causes AIDS by destroying or depleting the number of CD4+ cells or they may functionally impair the cells. This reduces the ability of the immune system to fight against diseases. So, the correct option is 'depleting CD+4 T-helper lymphocytes'.

HIV multiplies in macrophages and then new viruses targets T - helper cells which makes the infected person immuno - deficient . So the correct option is "T- helper cells"

HIV is a human immunodeficiency virus. When a person is infected by the HIV, it causes HIV infection. It affects the immune system of the body. It infects cells of the human immune system, such as helper T (T$ _H$) cells (CD$ _{4+}$ T cells), macrophages and dendritic cells. Due to this, it is difficult for the body to fight off other infections. 

AIDS virus destroys the immune system by attacking white blood cells called CD4 cells. HIV gets inside the CD4 cells and make copies of itself and then kills the CD4  cell. The new HIV copies find other CD4 cells to attack them. Thus, it destroys the immune cells, therefore reduces immunity. 

HIV (Human Immunodeficiency Virus) has a viral envelope, matrix proteins and core. The viral core consists of two single strands of RNA for its genome. The RNA genome consists of ribonucleotides (ribose + nitrogenous bases + phosphate) wherein thymine is replaced by uracil. The quick mutation rate of RNA genome makes it difficult to have a vaccine against it. The viral coat has trimeric glycoprotein gp120 which contacts CD4 terminal domain of the T4 cell. This contact leads to activation of gp120 followed by contact with chemokines receptor CCR5, a multipass membrane protein.  The result is activated gp41 which in turn cleaves gp120.  The terminal domain of gp41 interacts with the target cell and fuses with the T cell membrane to facilitate entry of virus with capsid into the cell.  RNA retroviruses have reverse transcriptase enzyme that synthesizes a DNA copy (cDNA) of viral RNA. Thus, the correct answer is option D.

HIV attacks and kills immune systems cells known as Helper T cells. Without Helper T cells many other immune system cells cannot work properly, including B cells that make antibodies 

HIV is a virus that targets and alters the immune system, increasing the risk and impact of other infections and diseases. It damages the immune system and infects macrophages, T- cells etc.