Surprising protective mechanisms against severe forms of COVID-19 infection among Common Variable Immunodeciency Patients- one center experience.

In this report we aimed to present the nonthreatening experience of patients diagnosed with Common variable immunodeciency (CVID) included in the National Rare Disease Program registry and consulted at the Immunology department of the Regional Institute of Gastroenterology and Hepatology “Prof Dr. Octavian Fodor” during the Coronavirus disease 2019 (COVID-19) pandemic as well as to review the current understanding of COVID-19 immunopathology followed by possible protective mechanisms against severe infection in these highly susceptible individuals. We report clinical and laboratory results of patients in a single-center retrospective study after lockdown restrictions were partially lifted (May-June 2020) and patients were able to come into the hospital for routine check-up and immunoglobulin replacement treatment. Of the 49 patients consulted during this period, we identied only one asymptomatic patient with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, supporting recently published data that not all immune compromised patients are at increased risk. According to recent publications the virus induces an inammatory response leading to a cytokine storm responsible for severe complications. CVID patients seem to be protected from severe forms of this severe virus through reduced viral susceptibility, decient B lymphocyte response, loss of Interleukin-6 (IL-6) receptor and impaired toll-like receptor pathway activation. Despite being at high risk for other infectious disease, in the context of SARS-CoV-2 induced pandemic, CVID patient’s lack of immune response is their protection against the dangerous macrophage hyper-activation resulting cytokine storm consequences.


Introduction
Common variable immunode ciency (CVID) is a heterogeneous immune disorder characterized by recurrent infections, associated with autoimmune disorders, and increased risk of malignancy; de ned by hypogammaglobulinemia involving IgG and either IgA and/or IgM de ciency as a result of reduced numbers of isotype-switched memory B cells and consequently absence of plasma cells [1]. Apart from a small subset of identi ed molecular defects, the main mechanisms accounting for the defective B cell differentiation into plasma cells observed in all cases have remained, for the most part, unknown [2,3].
Besides the lack of immunoglobulin production and its clinical rami cations, failure of B cell development also presents with a few other identi ed molecular alterations which may in fact prove to be protective in certain viral induced conditions. Patients with an immune disorder, that can be potentially life-threatening in the face of bacterial pathogens and quality-of-life modifying through progressive chronic disease affecting multiple systems as well as frequently associated with autoimmune and malignant disorders; would qualify as a highly susceptible group of individuals in the current Coronavirus disease 2019 (COVID-19) pandemic. To date however, global surveys designed to collect data on COVID-19 in Primary Immunode ciency patients do not point to an increased risk of infection, especially not in its severe form. Several cases of SARS-CoV-2 infection have been reported world-wide among those with predominantly humoral primary immunode ciency, nonethelessremarkable recovery was observed in most cases [4,5,6].

Methods
This is a single-center retrospective study of the 49 patients with CVID included in the Romanian National Rare Disease Program registry and consulted at the Immunology and Allergy department of the Regional Institute of Gastroenterology and Hepatology "Prof Dr Octavian Fodor" during the COVID-19 pandemic, from February to June 2020. Collection and analysis of data from clinical, laboratory and diagnostic testing reports was conducted after informed consent was acquired from all participants, followed by literature review of the topic. Table 1. Immune status of CVID patients after Covid-19 pandemic peak Of the total number of patients (Table 1) consulted during this period, six presented respiratory manifestations (dry/productive cough, sputum production, dyspnea) without positive epidemiological history, thus were not tested; their symptoms being interpreted as manifestations of the chronic lung disorders secondary to CVID. We performed PCR tests for two potentially SARS-CoV-2 infected individuals: patient no. 7 presenting with asthma exacerbation, fever and malaise and patient no.8 that presented with dyspnea, severe fatigue and myalgia. Both results were negative. One single CVID patient no. 23 from our center was con rmed to have SARS-CoV-2 infection, tested due to direct contact with Covid-19 case, however the patient remained completely asymptomatic, without laboratory tests to suggest a hyper-in ammatory response. Having a state of severe immunode ciency made it di cult to clear the infection, which lingered for a period of ten weeks, and as expected no speci c antibodies could be identi ed in patient's serum.
As can be observed in Table 1, sudden lockdown implementationand restricted hospital access left our patients without immunoglobulin replacement therapy for an average of two months resulting in marked hypogammaglobulinemia, putting them at increased risk for various severe infections. Strict social distancing and appropriate hygiene measures were highly recommended to our patients in order to assure their safety until they were able to access immunoglobulin replacement therapy again.

Discussion
Coronaviruses are a diverse group of single-stranded RNA (ssRNA) viruses which circulate among vertebrates and usually cause mild upper respiratory tract infections in humans [7]. In December 2019, in the city of Wuhan, a novel Betacoronavirus responsible for potentially fatalviral pneumonia was identi ed, o cially named severe acute respiratory syndrome coronavirus 2 (SARS-Co-V-2) [8]. As of July 22, 2020, the virus has caused 15,217,434 infections world-wide with a case-fatality rate of 4.09% (622,454/15,217,434).
Clinical presentation of SARS-CoV-2 infection is variable, ranging from lack of symptoms to mildmoderate symptoms including fever, dry cough, and fatigue in majority of cases [9], however severe infections can present with acute respiratory distress syndrome and multi-organ failure requiring intensive care unit admission [5]. Less frequent symptoms include headache, sputum production, dyspnea, sore throat, nasal and conjunctiva congestion, myalgia, arthralgia, chills, nausea, vomiting and diarrhea, anosmia and aguesia [10].

Immune mechanisms involved in COVID-19 severity
The physiological response to viral infections is generally initiated at the cellular level following replication. Transcriptional activation by the intracellular virus leads to the stimulation of two antiviral defense mechanisms. One antiviral response is the induction of type I and type III interferons (IFN) with subsequent upregulation of IFN-stimulated genes and viral control. The second antiviral response iscoordinated by cytokines responsible for the recruitment of speci c subsets of white blood cells involved in eradicating the infection [9].
A study that set out to identify the transcriptional signature of SARS-CoV-2, presented data that suggest that the immune response in COVID-19 is imbalanced with regard to controlling viral replicationversus activationof the adaptive immune response [9]. A reduced IFN-I and III response to SARS-CoV-2 was observed, thus viral replication control is weak, while a robust cytokine response (especially IL-6 and IL-1) was noted. The underlying pathophysiology of COVID-19 is still under investigation, but it appears that the virus induces an in ammatory response involving macrophage hyperactivation, leading to a cytokine storm responsible for severe complications [4,12].
Cytokine release syndrome is a systemic in ammatory response that can be cause by various factors (infections, drugs) characterized by a sharp increase in pro-in ammatory cytokines [8]. Interleukine-6 (IL-6) is a multi-faced cytokine with both anti-in ammatory and pro-in ammatory effects that is produced by T lymphocytes, endothelial cells, broblasts, macrophages and monocytes, activated by Interleukin-1b and tumor necrosis factor-alpha [8]. IL-6 has various biological functions: inducing B-cell proliferation and differentiation to produce antibodies (a process that is absent or defective in agammaglobulinemia and CVID), induces cytotoxic T lymphocyte activity and proliferation, strong inducer of acute-phase reactive proteins (CRP) in the hepatocytes, and is associated with hypergammaglobulinemia [8].
Macrophage activation syndrome-like disease seen in severe COVID-19 cases is also responsible for the commonly observed extensive pulmonary microthrombosis [12]. Blockade of implicated cytokines is responsible for spectacular clinical outcomes withimmunosuppressive targeted monoclonal therapy (anti-IL6 receptor, Tocilizumab) and systemic corticosteroids in moderate to severe cases of COVID-19 [8].

Loss of IL-6 receptor
Recently, a number of cases with primary immunode ciency were found to have genetic defects in various components of the IL-6 pathway. Spencer et al. [13] and Nahum et al [14] reported cases with IL-6 receptor loss of function defects. Although these patients lack expression of a function IL-6R chain, it was hypothesized that cells should retain responsiveness to IL-6 through trans-signaling by binding gp130 co-receptor, however this was not the case, resulting in complete loss of IL-6 responsiveness in these patients [14]. Thus, even if IL-6 is produced by immune cells as a response to infection, a subset of patients with primary immune de ciency demonstrate a complete loss of responsiveness to IL-6. An accessible measure to demonstrate lack of physiological IL-6 activity can be a disproportionate level of low CRP (normally synthesized by hepatocytes response to IL-6) as opposed to high serum IL-6 [14].

Impaired Toll-like Receptor pathway activation
The Toll-like receptors (TLR) are a family pattern recognition receptors that are essential in the innate immune response, being activated by different types of pathogen ligands in order to clear infections [15].
TRLs which detect viral nucleic acids (TLR3, 7, 8 and 9) are expressed on intracellular endosome membranes. TLR7 responds to single-stranded ribonucleic acid (ssRNA) viruses [15], such as SARS-CoV-2. TLR7 is intrinsically expressed on the membranes of endosomes in plasmacytoid dendritic cells and B lymphocytes, which are abundantly present in lung tissue [16]. Signaling in human immune cells by TLR7 has been well-known to trigger production of pro-in ammatory cytokines including TNF-a, IL-6, IL-1b, IL-12 and IFT-a [15]. Thus, it is plausible to assume that the well documented cytokine storm partially responsible for severe forms of SARS-CoV-2 infection could also be a result of exaggerated TLR7 activation in lung residing immune cells. It has been demonstrated that certain TLR pathway activation is impaired in CVID, particularly TLR 7 and TLR9 involved in anti-viral innate immune response [2,3].

High dose Immunoglobulin therapy
Immunoglobulin replacement therapy is the only therapeutic option for CVID and agammaglobulinemia.
High does intravenous immunoglobulin (IVIG) was used in all reported cases of COVID-19 in CVID patients with great results. IVIG could also be potentially useful in treating severe COVID-19 patients due to it's immunomodulatory and anti-in ammatory effects but also possibly due to it's content of antibodies to other coronaviruses that cross react with SARS-CoV-2 [4].

Conclusions
In this article we report the experience of our CVID patients in the COVID-19 pandemic. Our data concludes that individuals with predominant humoral immunode ciency, particularly CVID, despite being at high risk for other infectious disease, in the context of SARS-CoV-2 induced pandemic, their lack of immune response could potentially be their protection against the dangerous macrophage hyperactivation resulting cytokine storm consequences. Despite the hypothetical paradoxical protection through immune de ciency, continued appropriate hygiene measures such as wearing a facial mask in public places, appropriate hand washing and disinfection as well as sensible social distancing are important precautions for all individuals, especially those with Primary Immunode ciencies.
Declarations Table   TABLE 1. Immune status of CVID patients consulted after COVID-19 pandemic peak