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A variety of expression vectors (e.g., Escherichia coli, Pichia pastoris and DNA) have been used to express Pvs25 protein which has been administered alone or in combination with adjuvants

To date these studies suggest that the recombinant protein currently requires both not only linear, but conformation dependent epitopes, and a strong adjuvant to induce transmission-blocking antibodies.

Intranasal and intramuscular immunization with Baculovirus Dual Expression System-based Pvs25 vaccine substantially blocks Plasmodium vivax transmission

Recently, we have developed a new vaccine vector system based on the baculovirus Autographa californica nucleopolyhedrosis virus (AcNPV) termed the “Baculovirus Dual Expression System”, which drives expression of vaccine candidate antigens by a dual promoter that consists of tandemly arranged baculovirus-derived polyhedrin and mammalian-derived CMV promoters. It has been shown that AcNPV, an enveloped double-stranded DNA virus that naturally infects insects, possesses strong adjuvant properties that can activate dendritic cell-mediated innate immunity

Mucosal vaccines have several attractive features compared with parenteral vaccines (e.g., safety, cost-effectiveness and ease of administration), but studies on their use have been limited almost exclusively to protection against mucosally transmitted pathogens. We provide evidence that i.n. immunization is a feasible alternative for preventing malaria, which is transmitted through non-mucosal routes

These results are consistent with our previous work showing that intranasal immunization with the baculovirus-based vaccine induced strong systemic humoral immune responses with high titres of antigen-specific antibodies and conferred complete protection against malaria blood-stage challenge

which can induce immunological memory against heterologous antigens in a rodent model; however, it is precluded from clinical use due to its enterotoxicity and potential hazardous effects on olfactory nerves [22]. In contrast, a baculovirus-based delivery system may offer an attractive immunization method, as AcNPV exhibits low cytotoxicity and is incapable of replication in mammalian cells

The data described here adds to previously presented data showing the significant potential of the baculovirus dual expression system against the blood stages of the parasite

but also demonstrates clearly its ability to induce antibodies against the ookinete surface protein Pvs25, and to elicit a transmission-blocking immune response against the P. vivax isolates from endemic areas, and a transgenic rodent malaria parasite model in preliminary studies.

One was SMFA on peripheral blood from P. vivax infected patients.

The only other disease to have been banished from the earth is rinderpest, a little-known relative of measles that kills hoofed animals and once caused widespread starvation in Africa; it was eradicated in 2011.

Smallpox, caused by the variola virus, was long one of mankind’s most terrifying scourges.

it killed almost a third of its victims, often through pneumonia or brain inflammation.

Many others were left blind from corneal ulcerations or severely disfigured by pockmarks.

Because it killed 80 percent of the American Indians who caught it, it was a major factor in the European conquest of the New World.

In 1796, Dr. Edward Jenner, an English physician, infected a young boy with cowpox taken from a blister on a milkmaid’s hand. Cowpox, a mild disease, protected those who had it from smallpox, and the modern vaccine era began.

Dr. Henderson quickly realized that trying to vaccinate vast populations was futile and switched to “ring vaccination.”

Dr. Foege, who is considered the father of this tactic, said it was “invented by accident” during a 1967 Nigerian outbreak when he had very little vaccine on hand.

“The first night, we asked ourselves what we would do if we were a virus bent on immortality,”

In 1977, success in hand, Dr. Henderson became dean of the Johns Hopkins University School of Hygiene and Public Health.“He was an imposing guy — physically big and very confident,” said Dr. Michael J. Klag, the school’s current dean, who was a student in that era. “He did not suffer fools gladly, and you were never sure if you were a fool or not.”

He gloomily foresaw failure for most other disease-elimination campaigns. The “siren song of eradication,” he once wrote, had led to goals that were more “evangelical” than attainable.

The problem, he would explain, was that each viral foe was so different. Smallpox had many weaknesses to exploit; it had no animal host. Every case can be found because victims have pox on their faces, and one vaccination provides lifetime immunity.

In 2011, when Bill Gates threw the full weight of his foundation into fighting polio, he struggled to explain how he would overcome such obstacles and, at the end of an interview, turned to an aide and said aloud, “I’ve got to get my D. A. Henderson response down better.”

The campaign, many experts have noted, succeeded just in time. A few years later, the virus that causes AIDS spread across Africa. Because the live smallpox vaccine can grow in an immune-compromised person into a huge, rotting, ultimately fatal lesion, it would have been impossible to deploy it.

Other members of the A3 family are believed to affect other exogenous viruses as well as endogenous retrovirus/retroelement movement within the genome. In particular, human A3A is a potent inhibitor of IAP and MusD and other retrotransposons such as LINE-1 and this inhibition is CDA-independent, at least in cultured cells [18]–[20]. A3A also inhibits adeno-associated virus replication, a nuclear-replicating parvovirus, via CDA-independent means [20]. In monocytes, A3A restricts HIV-1 infection and the decrease in A3A levels that occurs during monocyte-to-macrophage development is concomitant with increased susceptibility to HIV-1 infection [21]. A3A is not packaged into HIV virions and is thought to restrict infection by targeting incoming virus [22]–[24]. In contrast, A3A is packaged in human T-lymphotropic virus type-I virions and restricts infection, at least in transfected cells [25]. A3A preferentially deaminates cytidines that are in a TC motif [26].

To determine the level of transgene expression, we first isolated RNA from different tissues, including peripheral blood mononuclear cells (PBMCs), and performed reverse-transcribed real-time quantitative PCR (RT-qPCR). RNA from human H9 cultured cells and human and C57BL/6 mouse PBMCs served as controls. For each transgene, there was one high- (A3Ghigh, A3Ahigh) and one low- (A3Glow, A3Alow) expressing strain, defined by their relative expression in lymphoid tissues. The A3Ghigh strain expressed higher levels of the transgene than the endogenous mouse gene in spleen and thymus, but similar A3G levels in mouse and human PBMCs, while the A3Glow strain expressed approximately 10-fold lower levels in these tissues (Figure 1A). In contrast, the A3Ahigh strain expressed similar or lower levels than mouse A3; there was also about 2-fold lower expression of A3A in mouse PBMCs than in human PBMCs (Figure 1B). The A3Alow strain had very low but detectable levels of expression in several tissues. Since the β-actin regulatory region was used, transgene expression was seen in many tissues and in several at levels higher than endogenous mouse A3 (e.g. heart, brain and liver) (Figure 1A and 1B). We also performed western blots on different tissues from the 4 different mouse strains, using antiserum that detects both A3A and A3G. The relative protein expression levels were similar to that seen at the RNA level (Figure S1A and S1B).

We next determined if the in vivo-produced A3A and A3G proteins were functionally active. Extracts were prepared from primary splenocyte cultures and equal amounts (total protein concentration/volume) were incubated with FAM-labeled substrates containing the A3A- or A3G-preferred target sequence (S50-TTC and S50-CCC, respectively). As controls, we also performed these assays with extracts prepared from 293T cell lines transfected with A3A or A3G. Activity could be readily detected in transgenic mice expressing high levels of A3A or A3G. Further, in accord with the known specificity of the cytidine deaminases, extracts from the A3Ahigh mice deaminated the TTC- more efficiently than CCC-containing substrates, while those from A3Ghigh mice more efficiently deaminated the CCC substrate (Figure 2). For both A3Alow and A3G low, trace amounts of activity were detectable with the preferred substrates, while no activity was detectable with either endogenous mA3 or from mA3 knockout splenocytes. No deaminase activity was detected with WT mouse extracts, perhaps because the mouse protein has lower overall activity or expression. These data show that the transgenic mice expressed catalytically active human deaminases in these heterologous cells.

Humans have 7 APOBEC3 genes and determining how each specifically functions to inhibit retroviruses like HIV is complicated, because all 7 can be produced in a given cell type or tissue.

To overcome this limitation, we made transgenic mice that express two of the human proteins, APOBEC3A and APOBEC3G in mice that do not express their own APOBEC3. These mice were able to effectively block infection by several mouse retroviruses

We were unable to perform similar assays with in vivo produced MMTV, because the only cell-free virus in mice is found in milk and mammary tumors and we have not yet established breeding colonies of virus-infected human A3 transgenic mice.

A3G and A3A inhibit retrovirus infection by different means.

Two A3A and A3G mouse strains each were generated, expressing levels of these proteins within the range or at levels lower than that seen in human cells. This likely has relevance to what occurs in individual humans, where non-coding region polymorphisms in A3 genes alter expression levels and may influence progression to HIV-induced disease

An additional limitation of previous studies done on human A3 proteins is the reliance on transfecting constructs expressing A3 proteins, which may not reflect the endogenous levels of a protein expression found in vivo

Foreign immunogens or peptides can be displayed on the envelope of AcMNPV by fusion with the baculovirus major envelope protein gp64

Baculoviruses have strong adjuvant activity to promote humoral and cellular immune responses against coadministered antigens, activate dendritic cells maturation, induce the production of cytokines, chemokines, and type I IFNs

There are two influenza vaccine approaches licensed in the US; the inactivated, split vaccine and the live-attenuated virus vaccine. Inactivated vaccines can efficiently induce humoral immune responses but generally only poor cellular immune responses.

Therefore, influenza HA can be displayed on the surface of baculovirus

virus-like particle (VLP)

Even though cellular immune responses cannot confer sterilizing immunity, they are able to reduce the severity of infection and lower morbidity and mortality rates [47], and antigen-specific memory T cells are able to rapidly respond to a secondary virus infection [45]. Furthermore, cellular immune responses to the conserved epitopes contained in vaccines may provide cross-protective immunity against different subtypes of influenza virus infection

To confirm that each HA was incorporated on the envelope of baculoviruses, supernatants from infected Sf9 cells were used to perform hemagglutination assay

Most BV display strategies rely on gp64 protein which is the major envelope protein of baculovirus.