Symptoms of acute HIV infection are nonspecific and include fatigue, rash, headache, nausea, and night sweats. AIDS is characterized by pronounced suppression of the immune system and development of a wide variety of severe opportunistic infections or unusual neoplasms (especially Kaposi sarcoma). The more serious symptoms in adults are often preceded by a prodrome (“diarrhea and dwindling”) that can include fatigue, malaise, weight loss, fever, shortness of breath, chronic diarrhea, white patches on the tongue (hairy leukoplakia, oral candidiasis), and lymphadenopathy. Disease symptoms in the gastrointestinal tract from the esophagus to the colon are a major cause of debility. With no treatment, the interval between primary infection with HIV and the first appearance of clinical disease is usually long in adults, aver aging about 8–10 years. Death occurs about 2 years later.

A. Plasma Viral Load

The amount of HIV in the blood (viral load) is of significant prognostic value. There are continual rounds of viral replication and cell killing in each patient, and the steady-state level of virus in the blood (viral set point) varies from individual to individual during the asymptomatic period. This level reflects the total number of productively infected cells and their average burst size. A single measurement of plasma viral load about 6 months after infection is able to predict the subsequent risk of development of AIDS in men several years later in the absence of treatment (Figure 1). High set points tend to correlate with rapid disease progression and poorer responses to treatment. However, more recent data suggest a gender difference in this parameter—in women, the viral load may be less predictive of progression to AIDS. Plasma HIV RNA levels can be determined using a variety of commercially available assays. The plasma viral load appears to be the best predictor of long-term clinical outcome, whereas CD4 lymphocyte counts are the best predictor of short-term risk of developing an opportunistic disease. Plasma viral load measurements are a critical element in assessing the effectiveness of antiretroviral drug therapy.

Fig1. Prognostic value of HIV-1 RNA levels in the plasma (viral load). The virologic set point predicts the long-term clinical outcome. (Reproduced with permission from Ho DD: Viral counts count in HIV infection. Science 1996;272:1124. Reprinted with permission from AAAS.)

B. Pediatric AIDS

 The responses of infected neonates are different from those observed in HIV-infected adults. Pediatric AIDS—acquired from infected mothers—usually presents with clinical symptoms by 2 years of age; death follows in another 2 years. The neonate is particularly susceptible to the devastating effects of HIV because the immune system has not developed at the time of primary infection. Clinical findings may include lymphoid interstitial pneumonitis, pneumonia, severe oral candidiasis, encephalopathy, wasting, generalized lymphadenopathy, bacterial sepsis, hepatosplenomegaly, diarrhea, and growth retardation.

Children with perinatally acquired HIV-1 infection— if untreated—have a very poor prognosis. A high rate of dis ease progression occurs in the first few years of life. High levels of plasma HIV-1 load appear to predict infants at risk of rapid progression of disease. The pattern of viral replication in infants differs from that in adults. Viral RNA load levels are generally low at birth, suggesting infection acquired close to that time; RNA levels then rise rapidly within the first 2 months of life and are followed by a slow decline until the age of 24 months, suggesting that the immature immune system has difficulty containing the infection. A small percentage of infants (≤5%) display transient HIV infections, suggesting that some infants can clear the virus.

C. Neurologic Disease

 Neurologic dysfunction occurs frequently in HIV-infected persons. Around 40–90% of patients have neurologic symptoms, and many are found during autopsy to have neuro pathologic abnormalities.

Several distinct neurologic syndromes that occur frequently include subacute encephalitis, vacuolar myelopathy, aseptic meningitis, and peripheral neuropathy. AIDS dementia complex, the most common neurologic syndrome, occurs as a late manifestation in 25–65% of AIDS patients and is characterized by poor memory, inability to concentrate, apathy, psychomotor retardation, and behavioral changes. Other neurologic diseases associated with HIV infection include toxoplasmosis, cryptococcosis, primary lymphoma of the central nervous system, and JC virus-induced progressive multifocal leukoencephalopathy. Mean survival time from onset of severe dementia is usually less than 6 months.

Pediatric AIDS patients also display neurologic abnormalities. These include seizure disorders, progressive loss of behavioral developmental milestones, encephalopathy, attention deficit disorders, and developmental delays. HIV encephalopathy may occur in as many as 12% of children, usually accompanied by profound immune deficiency. Bacterial pathogens predominate in pediatric AIDS as the most common cause of meningitis.

As children born with HIV infection are living to adolescence and adulthood due to antiretroviral therapy, many appear to be at high risk for psychiatric disorders. The most common problems are anxiety disorders.

D. Opportunistic Infections

The predominant causes of morbidity and mortality among patients with late-stage HIV infection are opportunistic infections, that is, severe infections induced by agents that rarely cause serious disease in immune-competent individuals. Opportunistic infections usually do not occur in HIV-infected patients until CD4 T-cell counts have dropped from the nor mal level of about 1000 cells/µL to less than 200 cells/µL. As treatments are developed for some common opportunistic pathogens and management of AIDS patients permits longer survivals, the spectrum of opportunistic infections changes.

The most common opportunistic infections in untreated AIDS patients include the following:

1. Protozoa: Toxoplasma gondii, Isospora belli, Cryptosporidium species.

2. Fungi: Candida albicans, Cryptococcus neoformans, Coccidioides immitis, Histoplasma capsulatum, Pneumocystis jiroveci.

 3. Bacteria: Mycobacterium avium-intracellulare, M. tuberculosis, Listeria monocytogenes, Nocardia asteroides, Salmonella species, Streptococcus species.

4. Viruses: Cytomegalovirus, herpes simplex virus, varicella zoster virus, adenovirus, JC polyomavirus, hepatitis B virus, hepatitis C virus.

 Herpesvirus infections are common in AIDS patients, and multiple herpesviruses are frequently detected being shed in saliva. Cytomegalovirus retinitis is the most common severe ocular complication of AIDS.

E. Cancer

 AIDS patients exhibit a marked predisposition to the development of cancer, another consequence of immune suppression. AIDS-associated cancers tend to be those with a viral cofactor and include non-Hodgkin lymphoma (both systemic and central nervous system types), Kaposi sarcoma, cervical cancer, and anogenital cancers. Epstein-Barr viral DNA is found in the majority of B-cell malignancies classified as Burkitt lymphoma and those of the central nervous system (but is not found in most of the systemic lymphomas). Burkitt lymphoma occurs 1000 times more commonly in AIDS patients than in the general population.

Kaposi sarcoma is a vascular tumor thought to be of endothelial origin that appears in skin, mucous membranes, lymph nodes, and visceral organs. Before this type of malignancy was observed in AIDS patients, it was considered to be a very rare cancer. Kaposi sarcoma is 20,000 times more common in untreated AIDS patients than in the general population. Kaposi sarcoma-associated herpesvirus, or HHV8, appears to be causally related to the cancer. Cervical cancer is caused by high-risk papillomaviruses; the anogenital cancers also arise as a result of coinfections with human papillomaviruses.

Effective antiretroviral drug therapy has resulted in a marked reduction in the occurrence of Kaposi sarcomas but has had less of an effect on the incidence of non-Hodgkin lymphomas in HIV-infected individuals.

As HIV-infected persons live longer lives due to effective antiretroviral therapy, they are developing a broad spectrum of cancers at higher frequencies than the noninfected population. These HIV-associated malignancies include head and neck cancer, lung cancer, Hodgkin lymphoma, liver cancer, melanoma, and oral cancer. There does not appear to be an increased risk of breast, colon, or prostate cancer.

اخر الاخبار

اخبار العتبة العباسية المقدسة

العتبة العباسية المقدسة: نهج البلاغة مصدر صافٍ للفكر والمعرفة ومحصِّنٌ من الشبهات

العتبة العباسية المقدسة تطلق محاضرات محفل نهج البلاغة الأسبوعي في ذي قار

العتبتان المقدستان الحسينية والعباسية تدعوان للمشاركة في مهرجان الشموع بنسخته السادسة والعشرين

بالتعاون مع مستشفى الكفيل.. قسم الشؤون الطبّية يواصل إقامة البرنامج التدريبي لملاكاته النسوية

المزيد

الآخبار الصحية

الصحة العالمية تكشف حقيقة انتشار فيروس نيباه خارج الهند

متى يصبح محيط الخصر "مؤشر خطر"؟

دراسة تكشف دور "العوامل الوراثية" في تحديد عمر الإنسان

رائحة كريهة في الجسم.. "علامة خفية" أخطر مما تتصور

المزيد

الآخبار التكنلوجية

مايكروسوفت تكشف عن الجيل الثاني من شرائحها للذكاء الاصطناعي

خرافة "ثمانية أكواب يوميا".. كم من الماء يحتاج جسمك فعليا؟

هل توجد حياة خارج كوكبنا؟.. اكتشاف جديد يثير اهتمام العلماء

اكتشاف الخلايا المسؤولة عن فقدان ذاكرة الطفولة

المزيد

مواضيع ذات صلة

HIV Infections in Humans: Laboratory Diagnosis

HIV Infections in Humans : Pathogenesis and Pathology

Animal Lentivirus Systems

Classification of Lentiviruses

Viral DNA Is Integrated into the Host-Cell Genome in Some Nonlytic Viral Growth Cycles

Lytic Viral Growth Cycles Lead to Death of Host Cells

Viral Capsids Are Regular Arrays of One or a Few Types of Protein

Structure and Composition of Lentiviruses

HERPESVIRUSES

POLYOMAVIRUSES

Human T-Lymphotropic Viruses

Replication of Retroviruses