Language
Country/Area
No result found
Can the number of CD4 cells determine whether you will be infected with tuberculosis? Uncovering the relationship between HIV and tuberculosis!
Among current global health challenges, the co-epidemic of tuberculosis (TB) and human immunodeficiency virus (HIV) has become a major focus. According to the World Health Organization (WHO), tuberculosis is one of the leading causes of death among HIV patients. In 2019, TB was responsible for 30% of 690,000 HIV/AIDS-related deaths worldwide, and of the 1.4 million global TB deaths, 15% were HIV-infected.
“HIV interacts with tuberculosis to damage the immune system, thereby accelerating the progression of tuberculosis.”
HIV will cause the immune system to gradually decline. Especially when the CD4 T cell count is less than 200, the risk of tuberculosis infection will increase to 25 times. This situation is exacerbated in the case of multidrug-resistant tuberculosis (MDRTB) and extensively drug-resistant tuberculosis (XDRTB), which are difficult to treat and are associated with high mortality.
Tuberculosis can occur at any stage of HIV infection, but the risk and severity of TB increases soon after infection. Although tuberculosis may be a relatively early manifestation of HIV infection, the risk of tuberculosis increases as the CD4 cell count decreases. Even with high CD4 cell counts (after receiving antiretroviral therapy), the risk of tuberculosis in HIV-infected people remains higher than that in the general population.
“Internationally, the incidence of tuberculosis has been reduced by 60% and tuberculosis mortality has been reduced by 72% with the introduction of antiretroviral therapy.”
Between 2000 and 2021, the global launch of highly effective antiretroviral therapy (HAART) significantly reduced the incidence of tuberculosis among HIV-infected people.
Tuberculosis and HIV infection
Traditionally, tuberculosis affects the upper lobes, causing cavitary lesions. However, in HIV-infected individuals, the presentation may be more typical. In the setting of immunosuppression, patients with HIV may develop noncavitary nodular consolidation of the lower lobes, associated with hilar or mediastinal lymph node swelling. In people with advanced HIV/AIDS, chest X-rays may be normal. People with both HIV and TB are more likely to develop disseminated TB (the spread of TB in the blood or to sites outside the lungs).
In HIV-infected persons, the most common sites of extrapulmonary tuberculosis are lymph nodes, liver, spleen, and central nervous system (tuberculous meningitis). For tuberculous meningitis in HIV patients, the mortality rate is as high as 40%. Among patients infected with latent tuberculosis and HIV, there is a 5-10% chance that latent tuberculosis will progress to active tuberculosis. If not treated in time, the mortality rate can be as high as 50%.
The pathogenesis of HIV and tuberculosis co-infection
Tuberculosis develops when the immune response fails to suppress the growth of mycobacteria. Under normal circumstances, CD4+ helper T cells secrete the cytokine IFN-γ to recruit macrophages and stimulate them to destroy tuberculosis bacteria and form granulomas to prevent the spread of infection. However, in HIV patients, especially those with low CD4+ helper T cell counts, granulomatous tissue is often poorly developed, leading to the spread of TB in the lungs and throughout the body.
“The unique microenvironment of HIV makes it easier for tuberculosis bacteria to invade.”
HIV infection also affects the production of IFN-γ, thereby increasing the risk of HIV/TB patients developing reactivation or reinfection with tuberculosis.
Preventive measures
For HIV-negative children, allergic use of isoniazid can reduce the risk of tuberculosis infection. Some studies have explored the preventive effect of isoniazid in HIV-positive children and found that it can reduce the risk of active tuberculosis and death. Among children receiving antiretroviral therapy, there was no apparent benefit.
In addition, for HIV patients, the use of isoniazid and rifampicin as preventive therapy has been proven to be effective in preventing tuberculosis infection.
Diagnosis
Diagnosis of tuberculosis is relatively difficult in HIV-positive patients because the signs and symptoms may be atypical. Traditional sputum tests have low sensitivity. PCR tests based on GeneXpert rapid screening can detect tuberculosis and drug resistance in a short time, which is particularly important for HIV patients.
Treatment methods
Current recommendations suggest that HIV-infected patients with TB should receive comprehensive treatment regardless of CD4+ cell count. Standard therapy is six months of rifampin-based therapy. For rifampicin-resistant tuberculosis, treatment with other anti-tuberculosis drugs is recommended.
To summarize, the interaction between HIV and tuberculosis is extremely complex. Faced with this global health challenge, how should we prevent and treat it more effectively?
