Washington, Aug 12 (IANS) Clinching evidence unearthed by John Hopkins researchers about why some people with HIV remain symptom free even without treatment, has raised hopes of a vaccine against AIDS. These people also have never progressed to full-blown AIDS, probably because of the strength of their immune systems and not owing to defects in the HIV strain that infected them in the first place.

These conclusions about ‘elite’ suppressors, come from rigorous blood and genetic studies from a monogamous, married, African-American couple in Baltimore, in which the wife was infected through sex with her husband more than a decade ago.

Unlike her husband, the wife remains symptom free, has consistently had viral counts of fewer than 50 copies per cubic mm of blood, and has not needed any treatment to keep the disease in check.

The husband, as a so-called progressor, takes a potent drug cocktail to keep his infection from developing into full-blown AIDS, as demonstrated by viral counts in the hundreds of thousands per cubic mm of blood. The couple has been married for two decades and the husband was an intravenous drug user.

The scientists say the case study disproved some suspect theories about elite suppression that suggest it always involves a defective or “weakened” viral strain, which is easier for the immune system to attack, or that genetic variants confer a protective effect in suppressors.

“This is an extremely rare case of co-infection in a controlled, monogamous relationship, which showed us how a strong immune system in the elite suppressor kept the virus from replicating and infecting other cells,” said senior study investigator and infectious disease specialist Joel Blankson.

“Our findings offer hope to vaccine researchers because they reveal that the immune system’s primary offence, known as CD8 killer T-cells, can effectively halt disease progression by a pathogenic form of HIV,” said Blankson, an assistant professor at the Johns Hopkins University School of Medicine.

Included in the blood analysis was genetic testing which confirmed that both husband and wife were infected with the same pathogenic strain of HIV and ruled out the possibility that there were genetic deficiencies in the virus that infected the wife.

Using new lab tests that precisely measure the immune response to various strains of HIV, researchers first tested T-cells from both the wife and husband to see if their immune system cells suppressed viral replication. They found that activated T-cells from the wife stalled HIV replication by as much as 90 percent, while the husband’s T-cells stopped it by only 30 percent.

These findings were published this month in the Journal of Virology.