Coronavirus – Credit CDC PHIL
When we are infected by a never-before-encountered virus like MERS, our innate immune system launches a series of generic defenses to fight a delaying action in order to give our Adaptive Immune System time to produce pathogen-specific antibodies to (hopefully) neutralize the infection.
So we usually spike a fever while our natural killer cells and phagocytes rush to fight the infection. Our bodies produce protein and cytokine rich fluids at the site of the infection, and cells throughout our body release inflammatory mediators.
All good things, but they do tend to make us miserable when we are fighting a virus. This universal reaction explains why many viral infections `look and feel the same’ – particularly in the first few days of illness. How quickly and effectively we can mount a pathogen specific immune response to the infection can often determine the course of the illness.
But here things can get messy, as individual immune responses can vary greatly depending upon the host’s age, general health, previous viral exposures and/or vaccinations, and overall immune health. Complicating matters further, some viruses may invoke a faster or more robust immune response than others.
As you might imagine, a delayed immune response was linked to a worse outcome. While most patients developed robust antibody responses to the MERS virus within the first 3 weeks, a couple of cases did not, and the authors warn that survivors of MERS infection might not always be detectable in seroepidemiological surveys.
Volume 21, Number 12—December 2015
Wan Beom Park1, Ranawaka A.P.M. Perera1, Pyoeng Gyun Choe, Eric H.Y. Lau, Seong Jin Choi, June Young Chun, Hong Sang Oh, Kyoung-Ho Song, Ji Hwan Bang, Eu Suk Kim, Hong Bin Kim, Sang Won Park, Nam Joong Kim, Leo Lit Man Poon, Malik Peiris , and Myoung-don Oh
We investigated the kinetics of serologic responses to Middle East respiratory syndrome coronavirus (MERS-CoV) infection by using virus neutralization and MERS-CoV S1 IgG ELISA tests. In most patients, robust antibody responses developed by the third week of illness. Delayed antibody responses with the neutralization test were associated with more severe disease.
Knowledge of the kinetics and clinical correlates of serologic responses to Middle East respiratory syndrome coronavirus (MERS-CoV) infection is essential for diagnosing the disease, interpreting seroepidemiologic data to define prevalence and risk factors for infection, understanding pathogenesis, and assessing a potential role for passive immunotherapy. To address this knowledge gap, we investigated serologic responses to MERS-CoV in 17 patients.
During May–June 2015, an outbreak of MERS-CoV in South Korea resulted in 186 infections and 36 deaths (1–3); the outbreak strain was a clade B MERS-CoV closely related to viruses circulating in the Middle East (1). Seventeen patients with reverse transcription PCR–confirmed MERS-CoV infections were included in this study; the patients were hospitalized at Seoul National University (SNU) Hospital or SNU Boramae Medical Center in Seoul, South Korea, or at SNU Bundang Hospital, in Bundang, South Korea. We investigated early serologic responses; thus, patients who were transferred to these facilities >14 days after illness onset were excluded from study. Patients’ demographic and clinical profiles are shown in Technical Appendix[PDF - 288 KB - 2 pages] Table 1. Of the 17 patients, 9 had severe disease (4 required mechanical ventilation, 4 required supplemental oxygen; 1 died) and 8 had mild disease. Serial serum samples were collected and analyzed. The study was approved by the SNU Institutional Review Board.
An understanding of MERS-CoV antibody response kinetics helps in defining the window during which passive antibody therapy may be useful. In our study, this window was the first 21 days of illness for most patients. However, some patients may not develop strong antibody responses even after 4 weeks of illness, so therapy must be individualized.
In summary, our findings showed that an early MERS-CoV antibody response was associated with reduced disease severity. Robust neutralizing and S1 ELISA IgG antibody responses were mounted by the third week of illness in most patients. However, a robust response did not occur in a few patients, and infections in such patients may be undetectable by serologic and seroepidemiologic methods.
Although it is early days, it is encouraging to see dispatches and reports such as this coming out of South Korea so quickly following their outbreak.