Human chorionic gonadotropin (hCG) is not made normally by a woman and its appearance in urine or blood is taken as an indication of the on-set of pregnancy. With these established criteria, we made vaccine-inducing antibodies against hCG, which should be safe in a non-pregnant female devoid of hCG. As hCG plays an important role in the establishment of pregnancy, vaccine-inducing antibodies neutralizing hCG should prevent pregnancy. This was proven to be true by our phase II clinical trials conducted on the initial vaccine developed by us [1]. To enhance immunogenicity, β-hCG was linked non-covalently to α-subunit of ovine luteinizing hormone (LH). This heterospecies dimer (HSD) linked to tetanus toxoid (TT) was more immunogenic and induced higher antibody titers than hCGβ-TT [2]. It was then taken through phase I safety followed by phase II efficacy trials with the approval of ethics and drugs regulatory authorities. All women immunized generated antibodies. On the decline of titers, they were given booster injections to maintain antibody titers above 50 ng/mL. They all remained protected from becoming pregnant. Only 1 pregnancy occured in 1224 cycles [1]. Antibody response in 4 women of proven fertility who were sexually active, is shown in Figure 1.

All women continued to ovulate as indicated by progesterone in the luteal phase. Menstrual regularity was maintained. Antibodies generated by the vaccine did not intervene with normal reproductive functions. They remained sexually active.

The block of fertility was reversible. With the decline of antibodies titers, women desiring further a child, conceived at antibody titers below 10 ng/mL and gave birth to normal children fully comparable to others in the family born before they joined the trials [3].

I retired as director of the National Institute of Immunology (NII), New Delhi, India, and my successor asked me to leave the vaccine with NII. However, nothing was done. In 2006, I received a grant under Indo-US Bilateral Program to revive the vaccine. We now thought of making a genetically engineered recombinant vaccine so that it can be made at low cost with consistent characteristics, and made accessible to all, wherever they are, including France.

In the new vaccine, the β-subunit of hCG was linked to B subunit of heat-labile enterotoxin (LTB) of Escherichia coli as a carrier (Figure 2). The carrier chosen in this design of the vaccine does not evoke carrier-induced-immuno-suppression which TT as carrier did on continuous repeated use for long periods [4]. The B subunit of enterotoxin does not have these disadvantages. LTB has also adjuvant properties and evokes a mucosal response.

Keeping all these properties in mind, LTB was used to replace the previous carriers TT and diphtheria toxoid (DT) [5].

The hCGβ-LTB vaccine adsorbed on alhydrogel was used along with heat-killed Mycobacterium indicus pranii (MIP formerly known as Mw), a vaccine which we had developed originally against leprosy. MIP is a potent potentiator of humoral and cell-mediated immune responses [7]. The atomic microscopic image of MIP is shown in Figure 3. Figure 4 shows bioneutralization capacity of hCG by antibodies generated by hCGβ-LTB vaccine given with and without MIP.

Besides enhancing substantially antibody titers generated by the genetically engineered hCGβ-LTB vaccine, MIP brings in additional advantages to the body. It is effective against tuberculosis and several cancers [8, 9].

Very recently 2 clinical trials with MIP on coronavirus disease 2019 (COVID-19) infected patients have been published. In one conducted at Fortis Hospital in Mumbai, 117 patients suffering from COVID-19, were given treatment with MIP (Mw), 0.3 mL intradermal injections every day for 3 days, It led to rapid recovery of 116 patients. No systemic side-effects were observed of using Mw, MIP [10]. Another randomized trial with MIP (Mw) has been carried out in critically ill patients infected with COVID-19 in Delhi. The trial was on 42 subjects (22 patients treated with MIP, 20 with placebo). On days 14 and 21, subjects on the Mw (previous code of MIP) arm had a better clinical status than placebo [11]. No adverse events related to MIP use were observed.

We obtained the approval of the Review Committee of Genetic Manipulations (RCGM) for our recombinant vaccine after extensive toxicology studies. With the permission of the Drugs Controller General of India (DCGI) and ethics committees, a combined phase I/II trial has started at the All India Institute of Medical Sciences, New Delhi, and Sir Gangaram Hospital, New Delhi, India. Before the unforeseen COVID epidemic, 9 women received the primary injections consisting of 2 injections at fortnight intervals of the DNA version of the recombinant vaccine followed by 2 injections of the protein version of the recombinant vaccine. As the recombinant vaccine is first made in DNA form, followed by its expression as protein, we have tested in mice, the immunogenicity of the combined use of the DNA form of the vaccine for priming, followed by the protein version of the vaccine. This mode of immunization generates a higher antibody response in mice (Figure 5) [12], hence the adoption of this regime for the clinical trial.

An unexpected observation was the formation of nodules at the site of immunization in 3 women. Experiments were carried out in mice, where again nodules were seen after 2 injections of the DNA version followed by 2 injections of the protein version of the vaccine, all given intradermally with MIP as adjuvant (unpublished observations). We hypothesized that repeated use of the adjuvant in all 4 injections may have caused the formation of nodules. Employing MIP only in the first DNA version of the vaccine followed by the remaining one injection of DNA and two of the protein versions of the recombinant vaccine without MIP was seen to avoid the formation of nodules in mice. This mode of immunization will be followed in the clinical trial.

The recombinant vaccine has been passed on to M/s Bharat Biotech, who are making the recombinant vaccine under GMP conditions and supplying it free of charge for the clinical trial. The clinical trial has been interrupted by the COVID-19 epidemic. It will be resumed on the removal of the restrictions.

A number of papers have appeared reporting the ectopic synthesis of hCG by a variety of cancers at the advanced stage: lung cancer [13], bladder carcinoma [14], colorectal carcinoma [15], pancreatic carcinoma [16], breast cancer [17], cervical carcinoma [18], oral cancers [19], vulva/vaginal cancers [20], prostate cancer [21] and gastric carcinomas [22]. At this stage, the tumors are highly metastasizing and aggressive. We confirmed in mice that antibodies generated against hCG bind selectively to the tumor secreting hCG and not elsewhere in the body (Figure 6) [23]. What is amazing and highly interesting is that antibodies against hCG exercise impressive cytotoxicity on tumor cells expressing ectopically hCG (Figure 7).

Thus an additional unforeseen use of anti-hCG vaccine along with humanized antibodies will be in the treatment of such cancers.

A recombinant vaccine against hCG has been made and passed onto the industry. It is highly immunogenic. Its safety has been established and approval has been received from the DCGI and ethics committees for confirming its ability to prevent pregnancy by another trial. The trial which started around 24 months back is suspended due to the COVID-19 pandemic. An additional, but highly useful application of this vaccine is expected in advanced stage cancers expressing ectopically hCG.