Contact Tracing. Part 3
Concurrent with this observed increase in pro-inflammatory cytokines, a significant spike was measured in the IL-10 levels, an anti-inflammatory cytokine and potent inhibitor of Th1 cytokines and cellular responses. This spike coincided with the onset of a significant increase in the levels of LASV-specific IgM and IgG. Notably, IL-10 levels were elevated throughout the seven days of monitoring. Following the spike in pro- and anti-inflammatory cytokines, body temperature, respiration and pulse rates on day 10, the patient stabilized. His temperature did not return to febrile levels again during the course of these studies, and average respiration and pulse rates stabilized within normal levels. Thus, it appears that G-1180 experienced a dynamic interplay of pro- and anti-inflammatory cytokines and their physiological effects were ongoing throughout the extended analysis period of seven days. More importantly these results strengthen the hypothesis, as previously proposed by others, that an imbalance between pro- and anti-inflammatory cytokines plays an important role in the development of Lassa hemorrhagic shock, with poor outcome. Notably, the marked absence of TNF-α, a potent inducer of endothelial damage via apoptosis and thrombocytopenia throughout the monitored course of illness in G-1180, with the exception of a spike on day10, suggests a somewhat regulated and effective immune response at play. This applies to the marked absence of IL-1β during the same period. It has been suggested that an early pro-inflammatory cytokine response followed by downregulation to baseline levels, which has been characterized in Ebola patients, may also be important in a regulated and balanced immune response and outcome in Lassa fever infections. IL-4, a strong mediator of Th2 CD4+ T cells that stimulate B cells and enhance the humoral response, and IL-5, which functions as a B cell stimulator leading to increase in immunoglobulin secretion were not detected throughout the course of illness.
The two contacts of G-1180 that were admitted to the KGH LFW presented with lower, albeit significant levels of LASV NP antigen compared to G-1180. Surprisingly, and despite clear and re-confirmed presence of NP antigen in the serum of both G-1180-A and -B contacts by ELISA, levels did not decrease over a two day period following treatment with ribavirin. Neither contact presented with or developed classical symptoms of Lassa fever during their 10-day hospitalization period. Contact G-1180-A presented with very low but detectable IgM titer to NP, and background level titers to GP1 and GP2. G-1180-B presented with significant IgM titer to GP2, but undetectable titers to GP1 and NP. In both contacts IgG titers were detectable from the outset, but remained unchanged throughout the three days of testing according to endpoint titers. Thus, potential previous exposure to LASV and development of protective humoral and/or cellular immunity may have contributed to the observed Ag positive but asymptomatic status of these two patients
Despite the poor outcome for patient G-1177, a positive control used throughout these studies, she presented with moderate IgM to GP2, low IgM to GP1 and NP, high IgG to NP, and undetectable IgG to glycoproteins. Additionally, G-1177 presented with highly elevated levels of ALP and ALT, but with undetectable AST. Analysis of cytokines in the single G-1177 sample revealed similarities with those seen with G-1180. Notably, elevated levels of IFN-γ, IL-12p70, IL-6, IL-8, and IL-10 were detected. The most remarkable difference was a highly elevated level of IL-1β in G-1177, which was only detected in low levels in G-1180 on day 10. Similar to G-1180’s profile, cytokines IL-2, IL-4, IL-5, TNF-α, and TGF-β were not detected in G-1177.
Together, this case outlines the severe and prolonged multi-organ dysregulation, pro- and anti-inflammatory cytokine up- and down-regulation, and difficulty in management of acute Lassa fever infections. This case also delineates the necessity for prompt treatment with IV ribavirn, fluid management and maintenance of electrolyte balance to counter hypovolemia, hemorrhagic shock and malnutrition during the early stage of infection. Given the health status of G-1180 on day 6 post onset of symptoms, this study points to the possibility of positive outcomes in Lassa fever patients with severely compromised metabolic and immunological presentations.
Conclusions
Lassa fever has a high fatality rate if not diagnosed and treated promptly. Due to the low economic status of Lassa endemic areas, it often remains misdiagnosed and untreated. However, due to advances in diagnostics and laboratory research equipment at the KGH LFL, strides are being made towards better understanding the immunological impact of LASV. This case report exemplifies the utility of these methods in defining the host immune response to this pathogen. Our results combined with those of others that extensively characterized metabolic and immunological parameters of Lassa fever, point to a strong divergence in metabolites, cytokines and immunoglobulin levels in positive versus fatal outcomes. Further studies on both the cellular immune response and cytokine profiles early in LASV infections will be critical in deepening our understanding of Lassa fever and in closing the gap that currently exists between the initial time of infection and diagnosis and treatment.
This case report represents a snapshot of severe Lassa fever and exemplifies the capabilities of KGH LFL in diagnosing and monitoring the immunologic response during and post infection. This report dispels misconceptions that these studies are impossible in field hospital settings and demonstrates the potential to deploy diagnostic capabilities that will drastically impact treatment of Lassa fever by allowing the rapid identification, isolation and treatment of Lassa fever cases. Lastly the data in this manuscript provides insights into the clinical course of Lassa fever. Not only will these data inform clinical case management but they will also be critical to validating animal models currently being utilized for testing new candidate therapeutics and vaccines.