IntroductionAdeno-associated viral (AAV) vectors are widely used for stable in vivo gene transfer to terminally differentiated or quiescent cells such as muscle fibers, hepatocytes, neurons, retinal cells, and others. These vectors, derived from a nonpathogenic, replicationdefective parvovirus with a small single-stranded (ss) DNA genome, have recently been successfully used in clinical gene transfer for inherited blindness and also show promise for other diseases. 1,2 Eight years ago, Zaiss et al 3 found that ssAAV serotype-2 vectors caused only a weak and highly transient innate immune response in the liver, suggesting that inflammatory reactions to AAV are negligible. Numerous animal studies have shown stable correction of genetic diseases by hepatic AAV gene transfer that may, in part, be because of the low innate immune profile of the vector, avoiding inflammatory signals. 4 In humans, hepatic gene transfer with AAV2 has been hampered by pre-existing adaptive immunity after natural infection in the form of neutralizing antibodies and capsid-specific CD8 ϩ T cells. 5 Numerous changes to capsid and vector genomes have been developed in recent years in attempts to improve gene transfer efficacy and possibly evade immunity. For example, AAV8 shows substantially higher transduction efficiency in mouse liver and reduced activation of capsid-specific T cells, and it facilitates tolerance induction to transgenes. 6,7 Furthermore, prevalence for neutralizing antibodies in humans is markedly lower to AAV8 than to AAV2. 8 In another set of investigations, replacing surfaceexposed tyrosine residues to phenylalanine has been shown to improve gene transfer for several serotypes. The resulting reduction in capsid phosphorylation in turn reduces accumulation in the cytoplasm (in favor of trafficking to the nucleus) and ubiquitination of capsid. 9 AAV2 gene transfer to hepatocytes was most improved by a combination of 3 Tyr-Phe changes in amino acid residues 444, 500, and 730. 10 Modifications of the recombinant AAV genome also can improve transduction rates. Being ss, the ssAAV genome has to be converted to a double-stranded form in the nucleus of an infected cell for transgene expression to occur. To overcome this ratelimiting step, self-complementary (sc)AAV vectors were developed by elimination of the terminal resolution site in one of the inverted terminal repeats (ITRs). 11 For such a genome to be packaged into capsid, the size of the expression cassette has to be further reduced to not exceed the packaging limit. Two groups reported optimized scAAV vectors for treatment of the X-linked bleeding disorder hemophilia B (coagulation factor IX deficiency) by liver gene transfer. 12,13 The hepatic microenvironment is more tolerogenic than that of many other tissues. 14 For example, we were able to tolerize hemophilia B mice to human factor IX (hF.IX) by hepatic ssAAV2 gene transfer. This protocol was successful in several strains, with the exception of C3H. 15 Nonetheless, AAV8 and AAV2(Y444/500/ 730F) vectors were able to...

To address complications of pathogenic antibody or life-threatening anaphylactic reactions in protein replacement therapy for patients with hemophilia or other inherited protein deficiencies, we have developed a prophylactic protocol using a murine hemophilia B model. Oral delivery of coagulation factor IX fused with cholera toxin β-subunit (with or without a furin cleavage site; CTB-FFIX or CTB-FIX), expressed in chloroplasts (up to 3.8% soluble protein or 0.4 mg/g leaf tissue), bioencapsulated in plant cells, effectively blocked formation of inhibitory antibodies (undetectable or up to 100-fold less than controls). Moreover, this treatment eliminated fatal anaphylactic reactions that occurred after four to six exposures to intravenous F.IX. Whereas only 20-25% of control animals survived after six to eight F.IX doses, 90-93% of F.IX-fed mice survived 12 injections without signs of allergy or anaphylaxis. Immunostaining confirmed delivery of F.IX to Peyer's patches in the ileum. Within 2-5 h, feeding of CTB-FFIX additionally resulted in systemic delivery of F.IX antigen. This high-responder strain of hemophilia B mice represents a new animal model to study anaphylactic reactions. The protocol was effective over a range of oral antigen doses (equivalent to 5-80 μg recombinant F.IX/kg), and controlled inhibitor formation and anaphylaxis long-term, up to 7 months (∼40% life span of this mouse strain). Oral antigen administration caused a deviant immune response that suppressed formation of IgE and inhibitory antibodies. This cost-effective and efficient approach of antigen delivery to the gut should be applicable to several genetic diseases that are prone to pathogenic antibody responses during treatment.allergy | chloroplast | genetic disorders | oral tolerance | plant-made therapeutics

Islet grafts can induce insulin independence in type 1 diabetic patients, but their function is variable with only 10% insulin indepence after 5 years. We investigated whether cultured grafts with defined ␤ cell number help standardize metabolic outcome.

This study was conducted to predict the preventive behaviours of healthcare workers (HCWs) towards COVID-19 based on the Protection Motivation Theory (PMT). This crosssectional and analytical study was conducted on 761 HCWs in Hamadan, Iran, using multi-stage random sampling. The preventive behaviours against COVID-19 among HCWs were assessed at a relatively desirable level. Based on the PMT, threat and coping appraisal were predictors of protection motivation to conduct COVID-19 preventive behaviours (P<0.001). The intention was also predictive of COVID-19 preventive behaviours (P<0.001). Consideration of personnel's self-efficacy and their knowledge regarding the effectiveness of protective behaviours in designing staff training programmes are recommended.