MicrobiologyBytes

Previous studies have demonstrated that IgG and neutralizing antibodies against coronavirus associated with the severe acute respiratory syndrome (SARS) may persist, in spite of a decline in titer, for two years in patients who have recovered from SARS. For 3 years, we followed patients who had recovered from infection with SARS-associated coronavirus, to measure the longevity of specific antibodies. Fifty-six patients who were positive for serum IgG and neutralizing antibodies against SARS-associated coronavirus at the time of recovery from acute SARS infection were included in this study. The titers of IgG and neutralizing antibodies were significantly correlated during the 3-year follow-up period. The titers peaked at month 4 and diminished thereafter. IgG and neutralizing antibodies were undetectable in 19.4% and 11.1% of serum samples, respectively, at month 30, and in 25.8% and 16.1%, respectively, at month 36. For the IgG antibody, the mean titers dropped from 244 at month 4 to 34 at month 30 and 28 at month 36. For the neutralizing antibody, the mean titers dropped from 1232 at month 4 to 32 at month 30 and remained at that value through month 36. There were no significant differences in the kinetics of specific antibodies according to disease severity, duration of hospitalization, type and number of coexisting conditions, or use or nonuse of corticosteroids.
Experiments in animals indicate that IgG and neutralizing antibodies, along with T-cell mediated immunity, are essential for protection against live-virus challenge. These data suggest that immune protection may wane over time, as demonstrated in patients infected with human coronavirus 229E. How this waning humoral immunity may affect future SARS-associated disease in the context of re-exposure to SARS is unknown. In the absence of another SARS outbreak, we do not know whether lower or even undetectable levels of specific antibodies would be adequate to protect a person from reinfection due to a potential anamnestic response, as seen with other viral infections such as measles and hepatitis A. The implications of the lower neutralizing antibody levels in patients with aseptic femoral neck necrosis are unclear.

Disappearance of Antibodies to SARS-Associated Coronavirus after Recovery
NEJM 2007 357: 1162-1163

Tags: coronavirus, IgG, infection, neutralizing antibodies, SARS, severe acute respiratory syndrome, T-cell mediated immunity, virus

This entry was posted on Thursday, September 27th, 2007 at 4:42 am and is filed under Biology, Emerging disease, Health, Medicine, Microbiology, Science, Virology. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.