Analysis of cerebrospinal fluid protein concentrations of patients with cryptococcal meningitis treated with antifungal agents

Cryptococcal meningitis (CM) caused by Cryptococcus neoformans and Cryptococcus gattii [1] is notorious for prolonged treatment and high mortality [2‐4]. There is an increasing number of cases caused by Cryptococcus gattii, which infects both immunosuppressed and immunocompetent individuals [5]. In contrast, there are reports of immunocompetent patients infected with C. neoformans [6‐8]. This disease imposes a great burden worldwide, particularly in sub-Saharan Africa [3].

Lumbar puncture (LP) is advocated for the diagnosis and management of patients with CM [9, 10]. Analyses of the cerebral spinal fluid (CSF) of patients with CM patients provide a wealth of clinical data acquired through the use of the India ink stain, microbial culture, and biochemical tests. The CSF protein concentration is important as well, because increased concentrations are present in patients with neurological diseases. This condition is referred to as blood-CSF/blood–brain barrier dysfunction [11]. However, the clinical implication of differences in CSF protein concentrations in patients with CM is not fully understood.

The clinical interpretation of the levels of CSF protein concentrations is difficult, because the values change during treatment, and most studies report a single data point data rather than a time course. In the present study, we conducted a retrospective analysis of patients with CM who received antifungal treatment in our hospital and evaluated the clinical implication of the longitudinal data of CSF protein concentrations and the association with patients’ outcomes.

There were no significant differences between age, sex, and underlying diseases of the GR and PR groups (Table 1). The observation periods ranged from 32 days to 457 days. Patients received antifungal treatment within several days after admission. Two patients died while hospitalized.

Clinical treatment of patients with CM employs amphotericin B (AMB) and flucytosine to decrease the fungal burden in the central nervous system (CNS) [16]. To achieve a better outcome, most patients receive treatment that includes AMB [17]; however, we found that the implementation of antifungal strategies varied because of practical considerations such as costs, side effects, and availability of drugs (e.g. flucytosine was temporarily unavailable). The antifungal strategies are listed in Table 2, and analysis using the Fisher's exact test did not reveal significant differences between the groups.

We show here that patients in the good antifungal response group had higher baseline CSF protein concentrations, which indicates an increased inflammatory response in the CNS [18]. A plausible hypothesis to explain the data is that the intensity of the inflammatory response influences the antifungal response, and the CSF protein concentrations simply represent the intensity of inflammatory responses. Another study of patients with CM found that those infected with hepatitis B virus (HBV) had lower CSF white blood cell (WBC) counts and lower percentages of total protein in the CSF > 0.45 g/L, indicating a lower intensity of immune inflammation compared with patients with CM who were not infected with HBV who had a lower survival rate [19]. These findings indicate a correlation between the intensity of inflammatory responses and clinical outcomes.

A prospective study of patients with CM indicates that the baseline number of CSF colony-forming units (CFUs) is a prognostic factor, because patients with a lower number of CSF CFUs had better clinical outcomes [20]. Another study found a negative correlation between protein concentrations and fungal burdens in the CSF [21]. The higher baseline CSF protein concentrations reported here indicate a lower fungal burden, which indicated a better antifungal response. Others found that a higher WBC correlates with a good clinical response [21, 22] as well as a positive correlation between WBC count and CSF protein concentration was found in this study(Spearman’s rank correlation: R = 0.34, P = 0.00). Because drug concentrations in the CSF may be higher during inflammation of the CNS compared with those of patients without inflammation [23, 24], an elevated CSF protein concentration might indicate a higher level of inflammation that increases the transport of AMB to the CNS [24]. The rapid decrease of the CSF protein concentration in the GR-group indicates faster attenuation of inflammation, which led to a more effective antifungal response.

There are differences between the findings of the present study and those of other reports. For example, Lu et al., (1999) reported no significant difference in CSF protein concentrations between treatment failures and cured or improved groups [22]. However, the value of a single LB was not sufficient to evaluate the significance of changes in CSF protein concentrations during treatment. The difference may be attributed to the type of data analysis used compared with that of the present study. In the present study, we determined the time course of changes in CSF protein concentrations. Patients with CM are frequently immunocompromised, for example, those with infected with HIV [1]. However, only four (8.70 %) patients studied here were infected with HIV, which is lower compared with the rates reported by others [25]. The multiple polymorphisms in the genes encoding mannose-binding lectin and the Fc-gamma receptor 2B (FCGR2B) in the Han population, which is the largest ethnic group in China, might contribute to the discrepancies between studies [26]. The mortality rates (4.34 %) of patients treated at our hospital are lower compared with those of other studies [1]. The lower proportion of HIV-related infections may explain the discrepancy as well, and observations over eight years reveal that mortality rates are lower for patients with CM who are not infected with HIV [27].

The present study supports the hypothesis that there is a correlation between antifungal responses and CSF protein concentrations. These findings must be confirmed by prospective studies of larger numbers of patients. However, we recommend that the treatment of patients with CM should include detailed analyses of CSF protein concentrations with focus on their variability.