New Study Measures Effect of Strenuous Exercise on Soldiers’ Immune Systems

by U.S. Medicine

August 1, 2011

It may be possible to predict a soldier’s infection risks during and after strenuous physical exercise by pre-exercise immune system status or from a blood sample taken at rest, according to a recent study.1

According to the Swedish researchers, strain is put on the troops’ immune system in a military setting in many ways. This includes strenuous physical activity, sleep deprivation, caloric deficit and, environmental and mental stress.

“All these factors lead to immunological changes, resulting in a high rate of dropouts because of infections during military training,” they wrote in “Immunological Alterations Used to Predict Infections in Response to Strenuous Physical Training.”

For the study the researchers conducted a small scale pilot investigation that was designed to study immunological changes in the blood in 10 troops from the Swedish Coastal Ranger team before and after six days of military training and then to search for useful predictors of infections.

The troops worked, walked and kayaked as a group for 20 to 24 hours per day. During the training, four of the members had to leave because they were not able to perform the exercise due to illness. They were assigned to the Failed group. The other six completed the training and were assigned to the Completed group.

Blood samples were drawn from the troops in the morning of the first day of the study and immediately after the soldiers reached the military camp on day six. According to the researchers, only three of the measured variables differed between the Failed and Completed groups.

“The MESF (molecules of equivalent soluble fluorochrome) of CD3 on CD8+lymphocytes (T-cell receptor density on cytotoxic T cells) and the percent CD8+CD3+ lymphocytes (cytotoxic T cells) before the six days of training was lower and the CD4/CD8 ratio was higher in subjects who later failed to complete the course,” the authors wrote.

The researchers said that the findings indicate that the six days of military exercise “did not cause a major immune system depression.”

“Nevertheless, 4 out of 10 soldiers became ill and failed to complete the training period. It would have been possible to accurately predict these four subjects before their engagement in the training course based on their higher CD4/CD8 ratio and lower CD3 expression on CD8+ lymphocytes and percent CD8+CD3+ lymphocytes.”

The researchers suggested that a larger scale study with a focused analysis on T-cell surface receptors should be conducted to verify the results.

1. Ekblom O,Ekblom B, Malm C. Immunological Alterations Used to Predict Infections in Response to Strenuous Physical Training. Mil Med. 2011 July;176(7):785-790.

New Study Measures Effect of Strenuous Exercise on Soldiers’ Immune Systems Cont.

Children Have Higher Rates of Immunity Against HBV

Increased use of HBV vaccine in pediatric settings over the past decade has resulted in a cohort of children and adolescents with a very low prevalence of HBV infection and high rates of immunity. In contrast, adults, including those at high risk for HBV infection, continue to have low rates of immunity against this virus.

These findings were reported in a study that sought to determine up-to-date estimates of infection, exposure, and immunity rates for HBV in the United States population by using data on nearly 37,000 participants from the National Health and Nutrition Examination Survey  (NHANES) studies conducted from 1999 to 2008.1

Dr. George N. Ioannou, from the Veterans Affairs Puget Sound Health Care System and University of Washington in Seattle, reported in his paper that among persons aged 6 years or older, 4.6% had been exposed to HBV, according to NHANES data. In contrast, among the same age group surveyed from 1988 to 1994, 5.1% had been exposed to HBV. 

Among persons six years and older the prevalence rate of chronic hepatitis B was 0.27% in 1999 to 2008 compared to a 0.42% prevalence in 1988 to 1994. From 1999 to 2008 the prevalence of chronic HBV specifically in children ages 6 to 12 was 0.03%. Prevalence rates climbed with age and peaked at 0.57% for subjects in their 50s. It then decreased down to about 0.20% among older people.

“Other studies suggest that more than one half of the reported cases of acute hepatitis B in the United States occurred in persons who had previously received care in sexually transmitted disease clinics or correctional facilities,” he wrote in his paper. “Taken together with past studies, the current results highlight the need for better mechanisms to both reach and offer vaccination to these high-risk groups.”

A limitation cited in the study was that NHANES neither oversampled nor specifically identified Asian races or ethnicities that have high prevalence of HBV. Another limitation cited in the study was that incarcerated and homeless persons were not sampled.

“If these persons were added to the 704,000 persons that were estimated to have HBV, the total number of persons with chronic infection would increase to 738,000, or 0.28% (instead of 0.27%). Among homeless veterans hospitalized at a Veterans Administration domiciliary from 1995 to 2000 who were also tested for HBV infection, 1.17% had a positive result. The exclusion of homeless and incarcerated persons from NHANES means that the true national HBV prevalence was slightly underestimated,” Ioannou wrote.

The Veterans Affairs Research Enhancement Award Program was the primary funding source of the study.

  1.  Ioannou GN. Hepatitis B virus in the United States: infection, exposure, and immunity rates in a nationally representative survey. Ann Intern Med. 2011 Mar 1;154(5):319-28.

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New Study Measures Effect of Strenuous Exercise on Soldiers’ Immune Systems Cont.

Combination Vaccine More Effective Against Anthrax

A recent study concluded that combining BioThrax and CPG 7909 offers an enhanced immune response that has the potential to shorten the course of immunization and reduce the time to protection.1

Anthrax prevention efforts in the United States are supported by a stockpile of antimicrobials and the FDA-licensed vaccine BioThrax® (Anthrax Vaccine Adsorbed). BioThrax has also been used by the U.S. military to protect troops and civilians who may be deployed to areas where there is a significant risk of exposure to B. anthracis.

While the ACIP currently recommends vaccination with BioThrax for use in the post-exposure prophylaxis setting (PEP) under IND or Emergency Use Authorization, the researchers noted that  “a more rapid and stronger immune response” than that which can be achieved using BioThrax alone may be more advantageous in a PEP scenario.

“An advanced anthrax vaccine that would be capable of achieving protective immunity in less than three doses, and which would stimulate rapid and long-lasting immune responses would be an attractive option in a PEP setting, where both time to protection and protection against the threat of residual spores are important considerations,” the authors wrote.

The study pointed out that animal studies have demonstrated that the addition of CpG DNA adjuvants to BioThrax can markedly increase the immunogenicity of the vaccine, increasing both serum anti-protective antigen (PA) antibody and anthrax toxin-neutralizing antibody (TNA) concentrations.

For the study researchers evaluated The B-class CpG DNA adjuvant CPG 7909, a 24-base synthetic, single-strand oligodeoxynucleotide, for its safety profile and adjuvant properties in a Phase 1 clinical trial.

A double-blind study was performed in which 69 healthy subjects, age 18-45 years, were randomized to receive three doses of either: (1) BioThrax alone, (2) 1mg of CPG 7909 alone or (3) BioThrax plus 1mg of CPG 7909, all given intramuscularly on study days 0, 14 and 28. The subjects were then monitored.

The researchers found that those who received the adjuvant increased the antibody response by 6-8-fold at peak, and accelerated the response by three weeks compared to the response seen in subjects vaccinated with BioThrax alone. No serious adverse events related to study agents were reported, and the combination was considered to be reasonably well tolerated, the authors wrote.

“The marked acceleration and enhancement of the immune response seen by combining BioThrax and CPG 7909 offers the potential to shorten the course of immunization and reduce the time to protection, and may be particularly useful in the setting of post-exposure prophylaxis,” according to the researchers.

1. Rynkiewicz D, et al. Marked enhancement of the immune response to BioThrax® (Anthrax Vaccine Adsorbed) by the TLR9 agonist CPG 7909 in healthy volunteers. Vaccine (2011), doi:10.1016/j.vaccine.2011.05.047 

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