Papel de las plaquetas en la infección por el VIH/SIDA
HIV and Platelets
María José Míguez, M.D. Ph.D., Universidad de Miami, EEUU.
If you think that platelets are only those small corpuscles to prevent you from bleeding, think again. Platelets, along with all blood cells, originate as stem cells and mature in the bone marrow, where they then become differentiated into specialized cells. . The normal number of platelet cells ranges from 150000 to 350,000. HIV infection is associated with numerous abnormalities of hematopoiesis, affecting both the myeloid and lymphoid lineages derived from the hematopoietic stem cells.
From the immunological point of view platelets have both CD4 and CCR4 co-receptors. Furthermore, examination of platelets incubated with HIV shows internalization of HIV particles, indicating that platelets may play an important role in the immune response against HIV. On the other hand, Rozmyslowics and colleagues recently demonstrated that platelets can transfer CXCR4 to CXCR4-null targets, render i.e astrocytes and cardiomyocyte cells susceptible to HIV infection.
As many as 40% of HIV patients develop thrombocytopenia (TCP<150,000 cells /mm3platelets), and this condition is the first symptom or sign of infection in approximately 10% of all HIV-infected patients. Since it is frequently an asymptomatic condition and early studies suggested that TCP does not affects HIV disease prognosis, most physicians provided only symptomatic treatment (i.e. transfusion).
Recently, the TCP approach has started to change in light of studies demonstrating that TCP may have a significant impact on HIV disease. In support of this proposition, our recently published findings indicate more rapid disease progression in patients with TCP. Despite having similar baseline CD4 cell counts, a significant decline in CD4 cell count over time was observed in TCP patients as compared to those with normal platelet counts. Furthermore, a higher proportion of patients with TCP developed AIDS as compared to the controls. In accord, as part of the CDC-sponsored Adult and Adolescent Spectrum of Disease Project, thrombocytopenia (<50,000/mm3) has been associated with shorter survival (risk ratio, 1.7: 95% confidence interval = 1.6-1.8), after controlling for multiple factors (AIDS, CD4+ cell count, anemia, neutropenia, antiviral therapy, receipt of prophylaxis against P carinii).
In summary platelets seems to have an important role during HIV disease. Further research needs to be conducted to fully understood the role of platelets of HIV.