Study of Safety, Tolerability, and Efficacy of Ustekinumab for Symptomatic Gastrointestinal Inflammation Associated With Common Variable Immunodeficiency

* DIAGNOSIS AND CRITERIA FOR INCLUSION: A subject is eligible for the study if all of the following criteria are met: * Has given written informed consent. * Is male or female aged 18 through 75 years. * Has CVID or selective IgG subclass deficiency of either one or concomitant IgG subclasses comprising IgG1, IgG2, IgG3 or IgG4 (functional hypogammaglobulinemia) diagnosed prior to screening as based on the International Union of Immunological Societies (IUIS) criteria. * Has a documented, unintended loss of \>5% of their body weight over the last year or requires nutritional supplements to maintain his/her body weight and/or has chronic diarrhea defined as a complaint of at \>/= 50% of stools are non-formed for at least 4 consecutive weeks per patient history. Alternately, must be dependent on a therapeutic dose of antidiarrheals (e.g., loperamide or diphenoxylate with atropine) for control of chronic diarrhea. * If taking oral antibiotics chronically, must have used a stable dose of the antibiotic continuously for at least 2 weeks prior to start of screening period. * Is willing to have samples stored. * Be willing to consistently take appropriate measures to avoid pregnancy through the Week 48 study point. All subjects will be informed of the potential risks of ustekinumab during pregnancy and counseled on pregnancy avoidance appropriate to the subject s circumstances (e.g. fertility status, medical contraindications to hormonal birth control, and/or personal or religious beliefs regarding pregnancy avoidance). Subject to the judgment and discretion of the PI, some subjects may not need to take pregnancy avoidance measures. Patient handout on pregnancy avoidance will be provided to patients at the time of consent and discussion regarding pregnancy avoidance during the study. -Subjects who have previously been treated with a single 270 mg dose of ustekinumab on this study must be greater than 6 months from their treatment dose and have had recurrence of enteropathy symptoms. CRITERIA FOR EXCLUSION: A subject is excluded from the study if any of the following criteria are met: GENERAL CRITERIA: * Has any clinically significant disease or condition (e.g., renal, hepatic, neurological, cardiovascular, pulmonary, endocrinologic, psychiatric, hematologic, urologic, or other acute or chronic illness) that in the opinion of the investigator would make the subject an unsuitable candidate for this trial, or put the subject at undue risk by participating in this study. * Is a woman who has a positive pregnancy test or who is breast-feeding * Is a woman who does not agree to abide by the contraceptive measures required to prevent pregnancy during participation in the study, or meets exemption criteria for contraceptive measures, as outlined in the protocol. * Has any of the following clinical chemistry values: * AST \>2.5 times upper limit of normal (ULN). * ALT \>2.5 times ULN. * Serum bilirubin \>1.5 times ULN. * Serum creatinine \>1.5 times ULN. * Alkaline phosphatase \>2.5 times ULN. * Has a hemoglobin level \<9 g/dL or hematocrit \<30%. * Has an International Normalized Ratio (INR) \>1.3 or a Partial Thromboplastin Time (PTT) \>3 sec of ULN. * Has the following cell counts (cells/microL): * Platelet count \<75,000 or \>800,000. * White blood cell count \<2,000. * Neutrophil count \<1,000. * Has a current infection requiring intravenous antibiotics, a serious local infection (e.g., cellulitis, abscess) or systemic infection (e.g., pneumonia, septicemia). * Has a history of cancer within the past 5 years, with the exception of excised basal cell carcinoma, squamous cell carcinoma of the skin, or cervical carcinoma in situ. * Had a dependency for any illicit drug, chemical, or alcohol within the past 5 years. * Has a history of active tuberculosis (TB) (or a chest x-ray (CXR) with findings suggestive of old TB infection including calcified nodular lesions, apical fibrosis, or pleural scarring), acute or chronic hepatitis B, hepatitis C, human immunodeficiency virus (HIV) or opportunistic infections. GASTROINTESTINAL CRITERIA -Has a stool sample determined positive for acute gastrointestinal infection with impact of occurrence on gastrointestinal inflammation as determined by principal investigator during screening. In addition, stool samples positive for GI pathogens will be discussed with an infectious disease physician to determine impact of occurrence on gastrointestinal inflammation. If organism thought to be pathogenic, the subject will be treated with appropriate therapy. This will be documented in the subject s medical record. PRIOR MEDICATION CRITERIA * Received daily corticosteroids within 1 month prior to receiving study agent. The use of short-term or single-dose corticosteroids as a pretreatment regimen for IVIG is acceptable. * Received any investigational drug within 3 months prior to receiving study agent. * Received certolizumab or natalizumab within 3 months prior to receiving study agent * Received vedolizumab, infliximab, etanercept, or adalimumab within 2 months prior to receiving study agent. * Received cyclosporine, tacrolimus, sirolimus, pimecrolimus, mycophenolate mofetil or any other systemic immunosuppressants within 1 month prior to receiving study agent.