Microbewiki:Human Immunodeficiency Virus (HIV)

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Introduction


Human immunodeficiency virus (HIV) is an RNA retrovirus which attacks the immune system of the infected individual. There are two main strains of HIV: HIV-1 and HIV-2. HIV-1 is more prevalent and pathogenic. HIV belongs to a type of retroviruses which are called lentiviruses. Lentiviruses infect their hosts over a very long period of time and it can take years for symptoms to manifest. Over time, HIV can progress into Acquired Immunodeficiency syndrome or AIDS. HIV/AIDS is characterized by a decline in the number of CD4+ T-cells and an increased susceptibility to other infections.

The HIV genome consists of single-stranded, positive-sense mRNA, with three main open reading frames (gag, pol, and env). The viral capsid of HIV includes its genetic material, as well as reverse transcriptase, protease, and integrase. CD4 is the primary receptor targeted by HIV. CD4 is commonly found on helper T-lymphocytes, macrophages, dendritic cells, and monocytes. The virus also has to bind a co-receptor, CCR5, on the target cell in order to gain entry the cell. Once inside the cell, HIV uses its own reverse transcriptase to convert its mRNA into DNA and then inserts itself into the host genome, where it takes over the cell machinery to direct its own replication.

As of 2019, there are an estimate 38 million people currently living with HIV world-wide. Among the HIV-positive population, approximately 81% have received a diagnosis for HIV and 26 million HIV-positive people receive anti-retroviral therapy. Although HIV remains an enormous challenge to public health, significant improvements have been made in both preventing the spread of HIV and treating the infection. Over the last two decades, new infections have declined by 39% and deaths by 51%. This is due, in large part, to the creation of drugs known as anti-retroviral therapy (ART). ART consists of a combination of three drugs, which each target different components of the HIV life-cycle. Because HIV has such a HIV mutation rate, it is necessary to use a combination of different medications to ensure protection of a patient. Despite tremendous efforts, there still does not exist a vaccine for HIV. Currently, efforts are underway to develop a number of different types of vaccines for HIV.