Smallpox (variola virus) is a bioweapon concern. Monkeypox is a growing zoonotic poxvirus threat. These problems have resulted in extensive efforts to develop potential therapeutics that can prevent or treat potentially lethal poxvirus infections in humans. Monoclonal antibodies (mAbs) against smallpox are a conservative approach to this problem, as the licensed human smallpox vaccine (vaccinia virus, VACV) primarily works on the basis of protective antibody responses against smallpox. Fully human mAbs (hmAbs) against vaccinia H3 (H3L) and B5 (B5R), targeting both the mature virion (MV) and extracellular enveloped virion (EV) forms, have been developed as potential therapeutics for use in humans. Post-exposure prophylaxis was assessed in both murine and rabbit animal models. Therapeutic efficacy of the mAbs was assessed in three good laboratory practices (GLP) studies examining severe combined immunodeficiency mice (SCID) given a lethal VACV infection. Pre-exposure combination hmAb therapy provided significantly better protection against disease and death than either single hmAb or vaccinia immune globulin (VIG). Post-exposure combination mAb therapy provided significant protection against disease and death, and appeared to fully cure the VACV infection in ≥50% of SCID mice. Therapeutic efficacy was then assessed in two rabbit studies examining post-exposure hmAb prophylaxis against rabbitpox (RPXV). In the first study, rabbits were infected with RPVX and then provided hmAbs at 48 hrs post-infection, or 1 hr and 72 hrs post-infection. Rabbits in both groups receiving hmAbs were 100% protected from death. In the second rabbitpox study, 100% of animal treated with combination hmAb therapy and 100% of animals treated with anti-B5 hmAb were protected. These findings suggest that combination hmAb treatment may be effective at controlling smallpox disease in immunocompetent or immunodeficient humans.

The threat of a smallpox-based bioterrorist event or a human monkeypox outbreak has heightened the importance of new, safe vaccine approaches for these pathogens to complement older poxviral vaccine platforms. As poxviruses are large, complex viruses, they present technological challenges for simple recombinant vaccine development where a multicomponent mixtures of vaccine antigens are likely important in protection. We report that a synthetic, multivalent, highly concentrated, DNA vaccine delivered by a minimally invasive, novel skin electroporation microarray can drive polyvalent immunity in macaques, and offers protection from a highly pathogenic monkeypox challenge. Such a diverse, high-titer antibody response produced against 8 different DNA-encoded antigens delivered simultaneously in microvolumes has not been previously described. These studies represent a significant improvement in the efficiency of the DNA vaccine platform, resulting in immune responses that mimic live viral infections, and would likely have relevance for vaccine design against complex human and animal pathogens.

The New York City Board of Health (NYCBH) vaccinia virus is the currently licensed vaccine for use in the US against smallpox. The vaccine under investigation in this study has been attenuated by deletion of the innate immune evasion gene, E3L, and shown to be protective in homologous virus mouse challenge and heterologous virus mouse and rabbit challenge models. In this study we compared NYCBH deleted for the E3L gene (NYCBHΔE3L) to NYCBH for the ability to induce phosphorylation of proinflammatory signaling proteins and the ability to protect cynomolgus macaques from heterologous challenge with monkeypox virus (MPXV). NYCBHΔE3L induced phosphorylation of PKR and eIF2α as well as p38, SAPK/JNK, and IRF3 which can lead to induction of proinflammatory gene transcription. Vaccination of macaques with two doses of NYCBHΔE3L resulted in negligible pock formation at the site of scarification in comparison to vaccination using a single dose of NYCBH, but still elicited neutralizing antibodies and protected 75% of the animals from mortality after challenge with MPXV. However, NYCBHΔE3L-vaccinated animals developed a high number of secondary skin lesions and blood viral load similar to that seen in unvaccinated controls. The NYCBHΔE3L-vaccinated animals that survived MPXV challenge were able to show resolution of blood viral load, a decrease in number of skin lesions, and an improved clinical score by three weeks post challenge. These results suggest that although the highly attenuated NYCBHΔE3L allows proinflammatory signal transduction to occur, it does not provide full protection against monkeypox challenge.

The objective of this study was to analyze the immunogenicity and antigenicity of the V3 domain (Cys313-Cys346) of the external envelope glycoprotein gp125 of SIVmac251. The corresponding peptide was synthesized and characterized as linear and cyclic peptides. Our results showed that this region, as for HIV-1, contained an immunodominant epitope. The antigenicity was similar for the linear and cyclic peptides when tested against a panel of 15 sera from SIV infected macaques. Similarly, both peptide structures presented similar immunogenicity as shown by the characterization of the anti-peptide antibodies produced in rabbits against the cyclic and linear forms. But, unexpectedly, the antibodies produced against linear peptides recognized with a relatively higher intensity the native envelope gp140 than those produced against the cyclic structure. Furthermore, we showed that these antibodies recognized better the deglycosylated form of the glycoprotein. But, in contrast to the neutralizing activity obtained with anti-V3 peptides from HIV-1, no antiviral activity was obtained with antibodies generated against linear or cyclic SIVmac V3 peptides.

Depo-Provera (medroxyprogesterone acetate), a long-acting derivative of progesterone, is utilized during many nonhuman primate microbicide studies to facilitate simian immunodeficiency virus (SIV) infection by thinning the vaginal epithelium. To date, the systemic effects of this steroid hormone in regard to SIV/HIV pathogenesis are not well understood, but an increase in infection rates and lymphoproliferation following progesterone application has been reported. Therefore, a proactive study using 20 Chinese rhesus macaques was designed to investigate the effect of a single Depo-Provera injection on SIV disease progression. Group 1 (n = 10) was treated with 30 mg Depo-Provera intramuscularly 30 days prior to intravenous challenge with 50 TCID(50) SIVmac251, while Group 2 (n = 10) remained untreated, but received the same amount of SIV. Blood samples were taken at predetermined intervals to measure RNA viral loads, CD4(+), CD8(+), and CD20(+) lymphocyte counts and percentages and absolute numbers of naive and memory T lymphocytes. Upon statistical endpoint data analysis, none of the parameters measured were shown to be significantly different between the groups. One animal in the Depo-Provera-treated group and two macaques in the control group were euthanized prior to study end due to the development of clinical signs (in weeks 43 and 51, respectively). All other animals were euthanized between weeks 68 and 71 post-SIV infection. Histopathological evaluations revealed that 5 of 10 animals in each group had developed simian AIDS (SAIDS). In summary, this prospective study demonstrated that a single injection of 30 mg Depo-Provera did not have a significant influence on SIV disease progression.