Etiology and properties of the pathogen
The disease is caused by the human immunodeficiency virus, belonging to the subfamily of "slow" viruses (Lentivirinae). The main culprit of the pandemic is HIV-1. The virion contains viral RNA, a complex of enzymes (the most important being reverse transcriptase), and an envelope with the specific glycoprotein gp120. This particular protein acts as a key that binds to CD4 receptors on the surface of human cells.
The external environment is detrimental to the pathogen: it is thermolabile (killed by boiling in 1 minute), rapidly inactivated by ethanol (70% and 96%) and standard disinfectants. At the same time, the virus is quite resistant to low temperatures and ultraviolet radiation.
Pathogenesis of infection
Infection requires the entry of infected biological fluid (blood, vaginal secretions, semen, breast milk) into the bloodstream or onto mucous membranes. The concentration of the virus in saliva, tears, and urine is too low for transmission.
The process of viral replication is strictly linked to target cells (T-helper cells, monocytes, and endothelial cells):
- The virus attaches to the CD4 receptor and enters the cell.
- RNA and reverse transcriptase are released into the cytoplasm.
- Viral DNA is synthesized and integrated into the host cell genome, turning into a provirus.
Activation of the provirus triggers the death of T-lymphocytes via apoptosis. Simultaneously with the T-cell defect, the B-cell link is also affected, and the central nervous system is damaged (the virus infects neuroglia, causing encephalitis).
Stages and pediatric specifics
The national classification (by V.I. Pokrovsky) divides the process into five stages: from asymptomatic incubation and primary manifestations to the subclinical phase (generalized lymphadenopathy), the stage of secondary diseases (substages 4A, 4B, 4C depending on weight loss and the severity of opportunistic infections), and the inevitable terminal stage.
Pediatric clinical features:
- The disease progresses faster, and the latent period is short.
- Interstitial pneumonia, encephalopathies, gastrointestinal lesions, and chronic parotitis predominate.
- If the infection was transmitted vertically, stigmata are observed: prematurity, growth retardation, microcephaly.
- Unlike adults, Kaposi's sarcoma is extremely rare in children; primary CNS lymphomas and non-Hodgkin lymphomas predominate.
Diagnostic challenges in newborns
The basis of laboratory diagnosis in adults is the detection of specific antibodies by ELISA with confirmation in immunoblotting. However, in pediatrics, this rule does not apply to children in the first year of life.
The fact is that maternal IgG class antibodies are able to cross the placenta. They circulate in the infant's blood up to 15 months, yielding false-positive results in serological tests. Therefore, for early verification of status, the molecular genetic method — PCR (detection of viral RNA) is mandatory. Additionally, viral load and CD4 lymphocyte levels are assessed to determine the stage.
Principles of therapy and vaccination
Specific treatment is based on lifelong combination antiretroviral therapy (cART). Standard "triple therapy" includes a combination of reverse transcriptase and protease inhibitors. It does not completely kill the virus, but reliably blocks key replication enzymes.
Vaccine prophylaxis in HIV-infected children is carried out according to the national immunization schedule, but with strict restrictions:
- Live vaccines are strictly contraindicated: BCG (against tuberculosis) and OPV (oral polio vaccine).
- Allowed: inactivated polio vaccine (IPV), standard vaccines against measles, rubella, mumps (MMR), pertussis, diphtheria, tetanus, and hepatitis B.
To remember contraindicated vaccines: in immunodeficiency, "LIVE" is dangerous — Live Infectious Vaccines (BCG, OPV) cause generalized infection.
Class and exam questions
Why can the HIV ELISA be false-positive in children under 15 months?
During this period, maternal IgG antibodies that crossed the placenta during pregnancy still circulate in the child's blood. Only PCR provides a reliable picture.
Which tumors are atypical for children with HIV, unlike adults?
Classic AIDS-associated tumors, such as Kaposi's sarcoma, rarely develop in children. In pediatric patients, oncopathology most commonly manifests as brain lymphomas.
How does the virus destroy the child's nervous system?
The pathogen exhibits direct neurotropism. It primarily affects microglial cells, leading to trophic damage to neurons and resulting in subacute encephalitis and severe cognitive deficit.
What else to study on this topic
- Criteria for substages 4A, 4B, and 4C of secondary diseases
- Treatment regimens for Pneumocystis pneumonia and severe mycoses
- Differential diagnosis with primary immunodeficiencies
- Progression markers: evaluation of viral load and CD4/CD8 status
- Legal liability and medical confidentiality in managing HIV patients
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