Infection can cause temporary loss of immunity to other diseases

02 January 2014

Anopheles gambiae mosquito

Image: Anopheles gambiae mosquito©  US Centers for Disease Control and Prevention.

Immunity following vaccination can be temporarily lost due to another infection, but replenished over time by immune cells called memory B cells, according to a new study.

The fascinating finding comes from a study by a team at the Medical Research Council's National Institute for Medical Research (NIMR; now part of the Francis Crick Institute) who vaccinated mice against flu and then infected them with malaria.

The subsequent malaria infection caused the mice to lose their immunity to influenza. However this loss was only temporary - they regained immunity within a few weeks.

George Kassiotis of NIMR explained: "Think of immunological memory (in this case, antibody memory of immunity to flu) as computer memory. You store all your photos and videos - memories of past events - as single copies on a physical hard drive. You can retrieve these memories as you need them, but if the hard drive breaks down they are permanently lost.

"However, imagine that these memory files are not static copies, but are constantly being replaced with new copies from another source, such as an online storage vault. If the hard drive breaks down now, you would temporarily lose your memories, but as soon as you plug in a new hard drive, they could all be copied back and restored."

After vaccinating the mice against flu, checking that they had developed immunity and then infecting them with malaria, the researchers measured their amount of flu-specific antibodies and numbers of specific plasma cells over several weeks. The specific plasma cells are responsible for secreting the antibodies that provide immunity to flu.

They found that the plasma cells were replenished over the following weeks by circulating memory B cells, a type of white blood cell. The work shows that B memory cells are crucial - not only for providing immunity against reinfection by a pathogen an animal is already immune to, but also in recovery of this immunity if it is lost due to infection by a different pathogen.

Jean Langhorne, also of NIMR, said: "This study is important because it directly demonstrates how an acute infection such as malaria can cause loss of existing immunity to other infections. This might mean that there are periods when an otherwise protective vaccine is no longer protective. 

"However, this is transient as memory B cells replenish the pool of cells making protective antibodies. A large pool of memory B cells is therefore very important for maintaining and recovering protective antibody responses after vaccination."

The results have implications for understanding the length of time vaccination provides immunity against various diseases, which is especially important in countries where continuous infections are common.

The paper, Recovery of an antiviral antibody response following attrition caused by unrelated infection, by Dorothy Ng, John Skehel, George Kassiotis and Jean Langhorne, is published in PLOS Pathogens.

  • Infecting mice with malaria after vaccinating them against the flu virus causes transient loss of their immunity to flu, according to scientists from the Medical Research Council's National Institute for Medical Research. The immunity is recovered over the following weeks thanks to white blood cells called memory B cells - the same cells that are responsible for retaining long-term memory of infections against which an animal already has immunity.
  • The work may lead to new insights into the longevity of immune memory after vaccination - which is particularly important in countries where continuous or recurring infections are common.