A CD4 cell is a type of T cell that has a glycoprotein called CD4 on its surface. Also known as “helper” cells, CD4 does not neutralize infection, but rather prompts the body’s immune system to act upon an infective agent. By depleting CD4 cells, the immune function is gradually compromised, increasing the risk of HIV-related opportunistic infections.
During or soon after budding, the virion enters the maturation stage in which long strings of protein are cut up into functional HIV protein and enzymes. Maturation is required in order for the virus to become infectious.
Worldwide, TB is the leading cause of death among people living with HIV. In the United States, of the 8,683 people with TB who had a documented HIV test in 2011, 6% were coinfected with HIV.
Pneumocystis jiroveci pneumonia (also known as PCP) is considered an AIDS-defining condition in people with HIV. Due to the effectiveness of combination antiretroviral therapy (cART), the incidence of PCP has dropped dramatically since the height of the HIV epidemic the mid-1990s. That said, PCP is still the most common serious infection among people with AIDS in the United States.
P. jirovecii was originally classified as P. carinii but was later changed to differentiate it from other forms of Pneumocystis found in animals.
C. albicans one of a genus of yeast fungi that can cause infections in humans, ranging from superficial oral candidiasis (thrush) and vaginitis (vaginal yeast infection) to potentially life-threatening, systemic disease in immune-compromised individuals. The CDC has classified esophageal candidiasis (candidiasis of lungs, bronchi, or trachea) as an AIDS-defining condition in people with HIV.
Candidiasis is common in people with HIV. While the implementation of combination antiretroviral therapy (cART) can significantly reduce the risk of esophageal candidiasis, it still remains one of the most common opportunistic infections in both resource-rich and resource-poor countries.
C. albicans is the predominant species most frequently associated with candidiasis, although other forms of Candida can cause the infection in humans.
Studies suggest that women with HIV are at greater risk for acquisition of HPV than non-HIV-infected women while demonstrating greater incidences of HPV-related abnormalities of cervical cells. It is these cells that can develop into cancer of the cervix.
Invasive cervical cancer is one of the conditions classified by the CDC as an AIDS-defining illness in people with HIV.
Meanwhile, an estimated 90% of anal cancers are attributed to HPV, with men who have sex with men (MSM) running nearly 35 times the risk of anal cancer than the general population.
T. gondii is a parasitic protozoan that can cause a disease called toxoplasmosis in humans and other warm-blooded creatures. If left untreated, toxoplasmosis can cause severe encephalitis (inflammation of the brain) and retinal damage. The most common neurological signs are speech and motor impairment. In advanced disease, seizures, meningitis, optic nerve damage, and psychiatric manifestations are often seen.
Toxoplasmosis of the brain is classified by the CDC as an AIDS-defining illness in people with HIV.
Over 200,000 cases of toxoplasmosis are reported in the United States each year, resulting in nearly 750 deaths—making it the second most common cause of lethal food-borne disease behind Salmonella.
Salmonella septicemia is a condition wherein the presence of Salmonella in the blood triggers a potentially life-threatening, whole-body inflammatory response. Recurrent Salmonella septicemia in people with HIV is classified as an AIDS-defining illness by the CDC.
With the advent of combination antiretroviral therapy (cART), Salmonella septicemia is considered rare among people living with HIV in the developed world. However, the majority of U.S. Salmonella-related deaths are either among older people or those with severely compromised immune systems.
Coccidioidomycosis is a fungal disease caused by C. immitis or C. posadaii, and is commonly known as “valley fever.” It is endemic to parts of the southwestern United States, from Texas to Southern California, as well as northern Mexico, Central America, and South America.
While coccidioidomycosis generally presents inside the lungs, when it spreads beyond the lungs in people with HIV, it is considered an AIDS-defining illness by the CDC.
In 2011, over 22,000 new cases of coccidioidomycosis were reported by the CDC, a tenfold increase from 1998. In California alone, the number increased from 719 in 1998 to a high of 5,697 in 2011.
Varicella zoster virus (VZV) is a member of the herpes virus family, which commonly causes chickenpox in children, teens, and young adults. After the resolution of primary infection, VZV lies dormant in the nervous system, with no further complications or consequence.
However, in 10%–20% of cases, VZV will reactivate in later adulthood, resulting in herpes zoster (or shingles). These generally occur in older people or people with severely compromised immune systems.
People with HIV are 17 times more likely to have VZV reactivation than those non-HIV-infected persons. While herpes zoster appears more frequently in individuals with low CD4 counts (under 200), they can present in people with moderate immune suppression (CD4s around 400).
VZV belongs to the same family of virus as the herpes simplex virus (HSV). VZV infection is not considered an AIDS-defining illness.
Cystoispora belli (formerly known as Isospora belli) is an intestinal parasite that can cause can disease in humans called cystoisosporiasis.
With the advent of combination antiretroviral therapy (cART), cystoisosporiasis is considered rare among people living with HIV in the developed world. However, occasional outbreaks have been reported in recent years, due in large part to returning travelers from tropical regions, where the disease is more widespread.
Cystoisosporiasis has been classified by the CDC as an AIDS-defining illness in people with HIV.
C. neoformans is one of two fungal species that can cause disease in humans called cryptococcosis. (The other is C. gattii.) Transmission occurs mainly through inhalation of the fungus, which is present in soil and bird droppings.
While the majority of adults and children exposed to the fungus will not develop cryptococcosis, people with severely compromised immune systems are at increased risk—with infection presenting primarily in the lungs or central nervous system, where it can cause potentially life-threatening meningitis.
In the developed world, the incidence of cryptococcosis has dropped dramatically since the introduction of combination antiretroviral therapy (cART). However, the disease is still a significant contributor to deaths and morbidity in the developing world, particularly sub-Saharan Africa.
Extrapulmonary cryptococcosis has been classified by the CDC as an AIDS-defining illness in people with HIV.
H. capsulatum is a fungus that can cause disease in humans called histoplasmosis. H. capsulatum is endemic to parts of the United States, as well as parts of Africa, Southeast Asia, southern Europe, Central America, and South America.
The H. capsulatum fungus can be found in soil, bird droppings, and bat guano. Because of its association with bats and caves, the disease is frequently referred to as “cave’s disease” or “spelunker’s lung.”
As much as 90% of the population in the eastern and central United States have been exposed to H. capsulatum, with most people experiencing little or no side effects. Those who do generally have mild, flu-like symptoms that quickly resolve with no lasting impact.
In immune-compromised individuals, histoplasmosis can progress to chronic lung infection, similar in expression to tuberculosis. Disseminated histoplasmosis, which can affect multiple major organs, is generally seen in HIV-infected patients with CD4 counts under 150.
Histoplasmosis has been classified by the CDC as an AIDS-defining condition in people with HIV.
