Impaired plant growth and development caused by human immunodeficiency virus type 1 Tat

Overlapping glycosylation sequon influences the glycosylation pattern of a chimeric protein expressed in tomato leaf and callus

Overlapping glycosylation sequon (OGS) is composed of two overlapping N-glycosylation sequons and has been found in certain glycoproteins with pharmaceutical value. With a growing interest to produce pharmaceutical glycoproteins in plants, it is important to establish the glycosylation pattern of OGS-containing proteins expressed in varying plant tissues. Here, a chimeric OGS (NNST)-containing gene and its mutated forms (NNAT and NASNAT) were expressed in callus-derived tomato plantlets. Tissue extracts from the recombinant leaf and callus were used in immunoblotting and glycoprotein detection. We found that the glycosylation patterns of the NNST-containing chimeric protein differ from that of NNAT- and NASNAT-containing proteins.

Cytokinin dehydrogenase differentially regulates cytokinin and indirectly affects hydrogen peroxide accumulation in tomato leaf

Cytokinin dehydrogenase (CKX) catalyzes the irreversible degradation of cytokinins (CKs). CKs play a role in the regulation of hydrogen peroxide (H(2)O(2)) accumulation while H(2)O(2) is involved in chlorophyll degradation. Here, we elucidated how CKX differentially regulates representative CK levels and indirectly influence H(2)O(2) accumulation in tomato leaves. We induced drought, salt and iron-deficiency stresses in tomato plants and found that chlorosis-inducing stresses (salt and iron-deficiency) induced lower chlorophyll levels as compared to drought stress and control. Protein gel blot analysis detected two CKXs in tomato leaves: a 35 kDa protein (CKX35) found in chlorotic leaves associated with a reduction in representative CK levels and high H(2)O(2) concentrations, and a 37 kDa protein (CKX37) found in green leaves associated with representative CKs and H(2)O(2) at normal levels. In summary, CKX isoforms in the tomato leaf appear to have distinct roles in differentially regulating CK levels and indirectly influencing H(2)O(2) accumulation.

A chloroplast-derived C4V3 polypeptide from the human immunodeficiency virus (HIV) is orally immunogenic in mice

Although the human immunodeficiency virus (HIV) causes one of the most important infectious diseases worldwide, attempts to develop an effective vaccine remain elusive. Designing recombinant proteins capable of eliciting significant and protective mammalian immune responses remain a priority. Moreover, large-scale production of proteins of interest at affordable cost remains a challenge for modern biotechnology. In this study, a synthetic gene encoding a C4V3 recombinant protein, known to induce systemic and mucosal immune responses in mammalian systems, has been introduced into tobacco chloroplasts to yield high levels of expression. Integration of the transgene into the tobacco plastome has been verified by Southern blot hybridization. The recombinant C4V3 protein is also detected in tobacco chloroplasts by confocal microscopy. Reactivity of the heterologous protein with both an anti-C4V3 rabbit serum as well as sera from HIV positive patients have been assayed using Western blots. When administered by the oral route in a four-weekly dose immunization scheme, the plant-derived C4V3 has elicited both systemic and mucosal antibody responses in BALB/c mice, as well as CD4+ T cell proliferation responses. These findings support the viability of using plant chloroplasts as biofactories for HIV candidate vaccines, and could serve as important vehicles for the development of a plant-based candidate vaccine against HIV.

Current status and perspectives of plant-based candidate vaccines against the human immunodeficiency virus (HIV)

Genetically engineered plants are economical platforms for the large-scale production of recombinant proteins and have been used over the last 21 years as models for oral vaccines against a wide variety of human infectious and autoimmune diseases with promising results. The main inherent advantages of this approach consist in the absence of purification needs and easy production and administration. One relevant infectious agent is the human immunodeficiency virus (HIV), since AIDS evolved as an alarming public health problem implicating very high costs for government agencies in most African and developing countries. The design of an effective and inexpensive vaccine able to limit viral spread and neutralizing the viral entry is urgently needed. Due to the limited efficacy of the vaccines assessed in clinical trials, new HIV vaccines able to generate broad immune profiles are a priority in the field. This review discusses the current advances on the topic of using plants as alternative expression systems to produce functional vaccine components against HIV, including antigens from Env, Gag and early proteins such as Tat and Nef. Ongoing projects of our group based on the expression of chimeric proteins comprising C4 and V3 domains from gp120, as an approach to elicit broadly neutralizing antibodies are mentioned. The perspectives of the revised approaches, such as the great need of assessing the oral immunogenicity and a detailed immunological characterization of the elicited immune responses, are also discussed.