Marker test for vertical transmission of HIV
Ans. (a) p24 antigenRef : Harrison 19th ed. /1246-47* Following HIV infection, the sequences of markers to identify infection in their chronologic order of appearance in serum are: viral RNA followed by p24 antigen and lastly anti-HIV antibody.* ELISA is positive in all babies born to HIV positive mother, due to transplacental transferrin of anti - HIV antibody.* About 2 weeks after infection, viremia is thought to increase exponentially and then decline to a steady- state level as the humoral and cell-mediated immune responses control HIV replication. This time interval, the serologic "window period," is characterized by seronegativity, occasionally detectable antigenemia, viremia (as measured by RNA), and variable CD4 lymphocyte levels. Detection of specific antibody to HIV signals the end of the window period and labels the individual as seropositive.* The exact time when HIV RNA, antigen, and antibody can be detected depends on several factors, including the test used, individual host responses, and viral characteristics. Viral RNA can be detected within the first 2 weeks using the highly sensitive RT-PCR method. Antigen, although transient, can appear as early as 2 weeks after infection and lasts 3 to 5 months Newer generation antibody assays, including the HIV third generation antigen-sandwich antibody assays, can detect antibody in most individuals at about 3 to 4 weeks post- infection and Hep D.
p24 antigen
Serum ELISA
Western blot
Immunoblot
Virology