People who start antiretroviral (ARV) therapy within six months of HIV infection retain immunity to other pathogens better than people who start treatment later, according to researchers at the National Institute of Allergy and Infectious Diseases (NIAID). The data, published online September 13 in the journal Blood, add to evidence that those living with HIV fortunate enough to be diagnosed within a few months of contracting the virus may benefit from immediate ARV treatment.

A number of studies from the past 15 years suggest important clinical benefits to starting ARV treatment very soon after infection. While the vast majority of people living with HIV are diagnosed several months, or even years, after contracting the virus, some individuals are diagnosed and enter care within weeks or a few months of infection.

If HIV is diagnosed and treated soon after infection is established, some researchers have suggested, it may be possible to protect cells capable of fighting HIV and other disease-causing pathogens.

B cells are a vital part of the immune system. They produce antibodies that target foreign organisms for destruction by other immune cells. Many of the B cells, and the antibodies they produce, are specific to only one type of pathogen. Vaccines take advantage of this. When we’re vaccinated against a disease, the vaccine prompts B cells to recognize parts of a pathogen and make antibodies. After an initial burst of activity, the B cells go into a resting state so that they are ready to wake up and quickly produce lots of antibodies as soon as we are exposed to the actual pathogen. Resting B cells can persist for many years.

To determine the impact of early ARV treatment on B cell preservation, Susan Moir, PhD, and her colleagues from NIAID compared B cell number and function in three groups: HIV-negative men, HIV-positive men who started ARVs within six months of infection and HIV-positive men who started ARVs many months or years after infection. The study looked backward, or retrospectively, at data that had already been collected for other studies.

Moir’s team found that before the two groups of HIV-positive men started treatment, both had poor B cell function and lower B cell numbers than HIV-negative men. After the HIV-positive men started treatment, however, the difference in both B cell number and function between those who started treatment within six months of infection and those who started later was striking.

Whereas the early treatment group saw their B cell number and function go back to similar levels as the HIV-negative men, those who started later had persistently lower and more poorly functioning B cells.

One way that Moir and her colleagues measured B cell function was to look at how well the three groups of men responded to influenza vaccination at the beginning of the study period—for the HIV-positive men this was just before starting ARVs—and then one year later. At the beginning of the study, both groups of HIV-positive men had poorer vaccine responses. A year after starting ARVs, however, men who’d started treatment early had normal vaccine responses, while those who started treatment later had persistently lower vaccine responses.

The authors stated that these data support recommendations to start treatment very early. They added: “These findings provide new insights on B cells in HIV infection and how early initiation of ART may prevent irreversible immune system damage.”