Lungs Diseases in HIV-Positive Patients: Causes and Prevention

Introduction

AIDS, or Acquired immunodeficiency syndrome, is one of the fatal disorders on the earth and is considered a significant burden for the healthcare system. It is caused by human immunodeficiency viruses (HIV) which are responsible for the depletion of the human immune system. Around round, 38.5 million people worldwide are suffering from AIDS. Almost 650000 have died in 2021 due to AIDS-related complications. AIDS is associated with a spectrum of conditions that are responsible involvement of various tissues and organs and infections related to them. Infection in the lungs is a common problem for AIDS patients.

What Is HIV?

Human immunodeficiency viruses (HIV) are types of retrovirus. They enter the human body as single-stranded RNA ( Ribonucleic acid) viruses. After entering the target cells, they change into double-stranded DNA (deoxyribonucleic acid) with the help of the reverse transcriptase enzyme. There are two types of HIV viruses. One is HIV-1 is the most predominant virus, which is highly virulent and infectious. Another one is HIV-2, which is less infectious and mainly seen in West Africa.

Transmission of HIV:

The main mood of transmission of HIV is:

• Through unprotected sexual contact. The virus can transmit through vaginal fluids, semen, and secretions of the genital organs.

• During a blood transfusion, if the donor receives the blood of the affected person.

• Needle prick is the most common cause of cross-contamination. Using the same needle that is off the infected person or sharing needles (occasionally done by drug addicts) may cause transmission of infection.

• It can transmit the child from the mother during pregnancy.

• This infection is not transmitted through touch, kissing, or saliva.

Pathophysiology of HIV:

The envelope of the HIV viruses fused with the cell membranes of macrophages and CD4+T lymphocytes by adsorptions of glycoproteins. They can also infect dendritic cells (antigen-presenting cells) transmitted through the sexual route. After this, ribonucleic acid and various enzymes are injected into the cells. Here synthesis of complementary deoxyribonucleic acid (DNA). These infected CD4+ T cells are destroyed by CD8+ T cells. As a result, the number of CD4+ cells dropped dramatically. In the chronic phase, the drop in CD4+ t lymphocyte cells is associated with the secondary infection due to lack of immunity. Body’s defense mechanisms Infection also affects various cells like the nervous system's macrophages, monocytes, and microglia cells.

What Are the Causes of HIV Associated Lung Infections?

As discussed during HIV infections, various opportunistic pathogens cause lung infections. These opportunistic pathogens are:

1. Bacteria: The virulent bacteria which may cause lung infections are Streptococcus pneumoniae, Haemophilus species, Staphylococcus aureus, and Pseudomonas aeruginosa. Also, bacteria belonging to mycobacteria species like Mycobacterium tuberculosis, and Mycobacterium avium are involved in various lung infections.

2. Fungi: Fungal infections are not common in healthy persons. But various fungal infections are common in HIV patients and are caused by Pneumocystis jirovecii, Cryptococcus neoformans, Histoplasma capsulatum, and Aspergillus species.

3. Cytomegalovirus infections can also be seen in HIV patients.

4. Toxoplasma gondii is a parasite that also may cause lung infection in such conditions.

Other than this, many noninfectious conditions are also associated with lung disorders. These are- Kaposi sarcoma, lymphomas, lymphocytic interstitial pneumonitis, pulmonary arterial hypertension, and Sarcoidosis.

Types of lung disorders are correlated to the level CD4 level. This is as follows:

1. CD4 count is less than or equal to 500 cells per cubic millimeter of blood: Related to bacterial pneumonia and tuberculosis.

2. CD4 count is less than 200 cells per cubic millimeter of blood: pneumocystis jiroveci; disseminated tuberculosis (a condition in which tuberculosis has spread to other organs than the lungs); toxoplasmosis.

3. CD4 count is less than 100 cells per cubic millimeter of blood: Kaposi sarcoma and non-Hodgkin lymphoma is seen in this condition.

4. CD4 count is less than 50 cells per cubic millimeter of blood: Atypical infection caused by mycobacteria species, fungal infections, and cytomegalovirus virus infections can be seen.

What Are the Common HIV Associated Lung Infections?

Different kinds of lung infections that are commonly seen in HIV patients are:

1. Bacterial Pneumonia: The most common type of lung infection is pneumonia. The incidence of bacterial pneumonia in HIV patients is five times more than in normal individuals. Streptococcus pneumoniae and Haemophilus influenzae are most commonly associated with such infections. Fever, cough, and purulent sputum are common symptoms of this condition.

2. Tuberculosis: Tuberculosis is one of the most common lung disorders. Tuberculosis can be seen at any stage of HIV-associated lung infection. When the CD4 count is in between 400 to 350 cells per cubic millimeter of blood, the clinical presentation of tuberculosis is similar to that of a normal person. When the CD4 count goes below 200 cells per cubic millimeter of blood, other tissues like lymph nodes, bones, spinal cord, and meninges are also affected by such infections. At a very low CD4 count (count is less than 50 cells per cubic millimeter of blood), tubercular infections by unusual organisms like Mycobacterium avium and Mycobacterium kansasii can also be seen.

3. Pneumocystis Pneumonia: This is one of the most common HIV-related lung infections affecting children and adolescents. It is caused by a fungus named Pneumocystis jirovecii. fever, nonproductive cough, breathing problems, and oxygen deficiency are the common symptoms of this condition.

4. Kaposi's Sarcoma: This is a cancerous condition that affects the blood and lymph nodes. The human herpes virus 8 is the causative organism in this case. Lung parenchyma, pleura, and other portions of the respiratory tract, like the oropharynx and larynx, are affected by these conditions.

5. Lymphomas: Lymphomas are the second most common type of cancer affecting the lungs of HIV-infected patients. This is a cancerous condition of the lymphatic system. Several types of lymphomas like Non-Hodgkin's lymphoma(the number of white blood cells is increased), Hodgkin's lymphoma (the number of white blood cells is increased, and a specific type of cell known as Reed-Sternberg cell can be seen), and Burkitt's lymphoma (caused by Epstein - Barr virus) affects the lungs.

What Are the Diagnostic Methods?

Several diagnostic tests can be done for the assessment of lung infections. These are:

1. Chest radiograph.

2. Computed Tomography

3. High-Resolution Computed Tomography

4. Positron Emission Tomography (PET)- CT.

5. Blood culture and cytological evaluation.

What Are the Preventive Methods?

Anti-retroviral therapy and regular evaluation of CD4 is the most efficient way of preventing lung infections. The use of antibiotics such as macrolide and fluoroquinolone can be done in cases of tuberculosis and pneumonia. Standard 4-drug therapy can be used in the case of multi-drug-resistant tuberculosis. Though, drug interactions with anti-retroviral in such cases can be a potential complication. Trimethoprim-sulfamethoxazole can be used in the treatment of pneumocystis pneumonia. Amphotericin B is used for the treatment of other fungal infections.

Conclusions:

HIV is a life-threatening disorder. Reduced immunity in HIV patients is responsible for infection and various disorders of other organs. Lung infections in HIV patients can be fatal. Opportunistic pathogens and carcinomas are lung disorders that are seen in such conditions. However, early initiation of anti-retroviral therapy can prevent such conditions.