What is HIV infection?

What is HIV infection?

تاريخ النشر : 20-01-2025

تحديث في : 20-01-2025

الموضوع: علم الفيروسات

الوقت المقدر للقراءة : 1 min

AIDS is an infectious disease caused by the HIV virus. To understand what it is and explore the mechanisms of infection and therapeutic strategies, we delve into the topic with Professor Guido Poli, Professor of General Pathology at the Vita-Salute San Raffaele University and Group Leader of the Human Immuno-Virology Unit at IRCCS Ospedale San Raffaele.

What Are AIDS and HIV?

AIDS is a viral sexually transmitted disease. As the name suggests, sexually transmitted diseases spread through sexual contact and can be caused by bacteria, parasites, or viruses.

The acronym AIDS stands for "Acquired Immunodeficiency Syndrome." The term "syndrome" was coined when the cause of the disease was still unknown and has remained even after the discovery of the virus. The specification "acquired immunodeficiency" was introduced to distinguish the new pathology from congenital immunodeficiencies.

HIV attacks the human immune system, weakening its ability to fight other infections, including harmless ones that do not pose a problem for healthy individuals.

"Historically, AIDS was first described in the literature in 1981 when cases were observed among male homosexuals in the USA. Shortly after, it became clear that the disease also occurred in people with hemophilia, heroin drug users, and heterosexuals. Later, the virus's transmission from mother to fetus or newborn was also demonstrated," explains Professor Poli.

Between 1983 and 1984, it was discovered that the cause of AIDS was a new retrovirus that can be transmitted through unprotected sexual contact, contaminated blood or derivatives, or breast milk in infants.

Today, approximately 40 million people worldwide live with an HIV diagnosis. In Italy, the Istituto Superiore di Sanità reports more than 72,000 cases of AIDS.

HIV Transmission and Mechanism of Action

HIV transmission occurs:

  • Horizontally, through sexual contact or the sharing of contaminated needles and syringes.
  • Vertically, from mother to fetus during pregnancy or through breast milk.

At the molecular level, HIV is a retrovirus with an RNA genome that is copied into DNA by an enzyme called reverse transcriptase.

HIV primarily infects CD4+ T lymphocytes of the immune system. Inside the cells, the viral RNA is transcribed into DNA and integrated into the cellular genome, directing the synthesis of new viral particles.

Macrophages: Immune Cells as Reservoirs for HIV

In addition to CD4+ T lymphocytes, the HIV virus also attacks macrophages, another type of immune cell, which are much more resilient than CD4+ T lymphocytes. Most macrophages do not succumb to the virus, whose genome can remain “silently” integrated into their DNA.

Alternatively, new viral particles are synthesized and accumulate within internal compartments of the cell, turning macrophages into “silent” reservoirs that are ready to “explode,” releasing the HIV virus.

Professor Poli’s Research on Macrophages

In recent years, Professor Poli’s research has focused on studying macrophages and their role in containing the virus and, therefore, in the propagation of HIV infection.

In particular, we developed an in vitro model to study how macrophages become reservoirs of the virus. These cells can be activated in two ways: M1 activation in response to inflammatory stimuli and M2 activation, which suppresses the inflammatory response.

We observed that in M1 macrophages, stimulated both before and after infection, the HIV virus remains integrated into their genome in a reversible state of ‘quiescence.’ Currently, we are using genomic techniques to better characterize the molecular identity of these cells, which act as reservoirs for dormant HIV,” explains the professor.

The combination of viral memory in T lymphocytes and the viral compartments within macrophages means that infected individuals may act as silent carriers of HIV without displaying symptoms of the disease. Furthermore, it is estimated that approximately 14% of infected individuals (around 10,000 in Italy) are unaware of their status, complicating efforts to control the spread of the virus.

Prevention and Awareness

Fortunately, today it is possible to control HIV infection thanks to the availability of antiretroviral drugs, which improve the quality and life expectancy of affected individuals,” continues Professor Poli.

However, since no therapy currently exists to completely eliminate HIV and cure the infection, it is essential to focus on prevention to protect both our health and the health of others.

The most important preventive measures currently are:

  • the use of condoms, which is the most effective, affordable, and widely available measure to protect not only against HIV but also against other pathogens transmitted through unprotected sexual contact;
  • the use of pre-exposure prophylaxis (PrEP) for HIV, based on the same drugs used in therapy, which is taken before engaging in sexual activity (though it does not protect against other sexually transmitted diseases).

It remains essential to integrate education and prevention programs starting in schools to promote awareness of the importance of preventing HIV and other sexually transmitted diseases without judgment,” concludes the professor.

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